Merge branch 'develop' into claude/deep-copy-key-comp-5649

Conflicts:
- tests/src/unit-comparison.cpp: kept both sides' helpers (key_case_less/
  key_case_json/innermost from the PR, case_insensitive_less/ci_json from
  develop's #5720) and both new test cases

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.github/workflows/check_amalgamation.yml

@@ -67,6 +67,7 @@ jobs:
 
           python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json.json -s .
           python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json_fwd.json -s .
+          cp include/nlohmann/json_literals.hpp $INCLUDE_DIR/json_literals.hpp
 
           # the header list of the Bazel "json" target must match the files in include/
           cmake -P cmake/scripts/gen_bazel_build_file.cmake

BUILD.bazel

@@ -21,6 +21,7 @@ cc_library(
         "include/nlohmann/adl_serializer.hpp",
         "include/nlohmann/byte_container_with_subtype.hpp",
         "include/nlohmann/detail/abi_macros.hpp",
+        "include/nlohmann/detail/bit_ops.hpp",
         "include/nlohmann/detail/conversions/from_json.hpp",
         "include/nlohmann/detail/conversions/to_chars.hpp",
         "include/nlohmann/detail/conversions/to_json.hpp",
@@ -33,6 +34,7 @@ cc_library(
         "include/nlohmann/detail/input/number_parse.hpp",
         "include/nlohmann/detail/input/parser.hpp",
         "include/nlohmann/detail/input/position_t.hpp",
+        "include/nlohmann/detail/input/pow5_table.hpp",
         "include/nlohmann/detail/input/string_scan.hpp",
         "include/nlohmann/detail/iterators/internal_iterator.hpp",
         "include/nlohmann/detail/iterators/iter_impl.hpp",
@@ -65,6 +67,7 @@ cc_library(
         "include/nlohmann/detail/value_t.hpp",
         "include/nlohmann/json.hpp",
         "include/nlohmann/json_fwd.hpp",
+        "include/nlohmann/json_literals.hpp",
         "include/nlohmann/ordered_map.hpp",
         "include/nlohmann/thirdparty/hedley/hedley.hpp",
         "include/nlohmann/thirdparty/hedley/hedley_undef.hpp",

Makefile

@@ -21,6 +21,8 @@ TESTS_SRCS=$(shell find tests -type f \( -name '*.hpp' -o -name '*.cpp' -o -name
 # the single headers (amalgamated from the source files)
 AMALGAMATED_FILE=single_include/nlohmann/json.hpp
 AMALGAMATED_FWD_FILE=single_include/nlohmann/json_fwd.hpp
+# json_literals.hpp only includes <nlohmann/json.hpp>, so it is copied verbatim
+AMALGAMATED_LITERALS_FILE=single_include/nlohmann/json_literals.hpp
 
 
 ##########################################################################
@@ -29,7 +31,7 @@ AMALGAMATED_FWD_FILE=single_include/nlohmann/json_fwd.hpp
 
 # main target
 all:
-	@echo "amalgamate - amalgamate files single_include/nlohmann/json{,_fwd}.hpp from the include/nlohmann sources"
+	@echo "amalgamate - amalgamate files single_include/nlohmann/json{,_fwd,_literals}.hpp from the include/nlohmann sources"
 	@echo "BUILD.bazel - regenerate the Bazel BUILD file from the include/nlohmann sources"
 	@echo "ChangeLog.md - generate ChangeLog file"
 	@echo "check-amalgamation - check whether sources have been amalgamated and BUILD.bazel is up to date"
@@ -154,14 +156,14 @@ install_astyle:
 
 # call the Artistic Style pretty printer on all source files
 pretty: install_astyle
-	$(ASTYLE) --project=tools/astyle/.astylerc $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) docs/mkdocs/docs/examples/*.cpp
+	$(ASTYLE) --project=tools/astyle/.astylerc $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) docs/mkdocs/docs/examples/*.cpp
 
 # call the Clang-Format on all source files
 pretty_format:
 	for FILE in $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) docs/mkdocs/docs/examples/*.cpp; do echo $$FILE; clang-format -i $$FILE; done
 
 # create single header files and pretty print
-amalgamate: $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE)
+amalgamate: $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE)
 	$(MAKE) pretty
 
 # call the amalgamation tool for json.hpp
@@ -172,16 +174,23 @@ $(AMALGAMATED_FILE): $(SRCS)
 $(AMALGAMATED_FWD_FILE): $(SRCS)
 	tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json_fwd.json -s . --verbose=yes
 
+# copy json_literals.hpp
+$(AMALGAMATED_LITERALS_FILE): include/nlohmann/json_literals.hpp
+	cp include/nlohmann/json_literals.hpp $(AMALGAMATED_LITERALS_FILE)
+
 # check if file single_include/nlohmann/json.hpp has been amalgamated from the nlohmann sources
 # Note: this target is called by Travis
 check-amalgamation:
 	@mv $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~
 	@mv $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~
+	@mv $(AMALGAMATED_LITERALS_FILE) $(AMALGAMATED_LITERALS_FILE)~
 	@$(MAKE) amalgamate
 	@diff $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE) ; false)
 	@diff $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE) ; false)
+	@diff $(AMALGAMATED_LITERALS_FILE) $(AMALGAMATED_LITERALS_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_LITERALS_FILE)~ $(AMALGAMATED_LITERALS_FILE) ; false)
 	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
 	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
+	@mv $(AMALGAMATED_LITERALS_FILE)~ $(AMALGAMATED_LITERALS_FILE)
 	@mv BUILD.bazel BUILD.bazel~
 	@$(MAKE) BUILD.bazel
 	@diff BUILD.bazel BUILD.bazel~ || (echo "===================================================================\n  BUILD.bazel is out of date! Please run 'make BUILD.bazel'.\n===================================================================" ; mv BUILD.bazel~ BUILD.bazel ; false)
@@ -222,7 +231,7 @@ json.tar.xz:
 # We use `-X` to make the resulting ZIP file reproducible, see
 # <https://content.pivotal.io/blog/barriers-to-deterministic-reproducible-zip-files>.
 include.zip: BUILD.bazel
-	zip -9 --recurse-paths -X include.zip $(SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) BUILD.bazel MODULE.bazel meson.build LICENSE.MIT
+	zip -9 --recurse-paths -X include.zip $(SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) BUILD.bazel MODULE.bazel meson.build LICENSE.MIT
 
 # Create the files for a release and add signatures and hashes.
 release: include.zip json.tar.xz
@@ -231,10 +240,12 @@ release: include.zip json.tar.xz
 	gpg --armor --detach-sig include.zip
 	gpg --armor --detach-sig $(AMALGAMATED_FILE)
 	gpg --armor --detach-sig $(AMALGAMATED_FWD_FILE)
+	gpg --armor --detach-sig $(AMALGAMATED_LITERALS_FILE)
 	gpg --armor --detach-sig json.tar.xz
 	cp $(AMALGAMATED_FILE) release_files
 	cp $(AMALGAMATED_FWD_FILE) release_files
-	mv $(AMALGAMATED_FILE).asc $(AMALGAMATED_FWD_FILE).asc json.tar.xz json.tar.xz.asc include.zip include.zip.asc release_files
+	cp $(AMALGAMATED_LITERALS_FILE) release_files
+	mv $(AMALGAMATED_FILE).asc $(AMALGAMATED_FWD_FILE).asc $(AMALGAMATED_LITERALS_FILE).asc json.tar.xz json.tar.xz.asc include.zip include.zip.asc release_files
 	cd release_files ; shasum -a 256 json.hpp include.zip json.tar.xz > hashes.txt
 
 

README.md

@@ -1395,6 +1395,7 @@ THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR I
 - The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2009 [Florian Loitsch](https://florian.loitsch.com/)
 - The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
 - The class contains parts of [Google Abseil](https://github.com/abseil/abseil-cpp) which is licensed under the [Apache 2.0 License](https://opensource.org/licenses/Apache-2.0).
+- The class contains an adapted version of the Eisel-Lemire algorithm and its table of powers of five from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors
 
 <img align="right" src="https://git.fsfe.org/reuse/reuse-ci/raw/branch/master/reuse-horizontal.png" alt="REUSE Software">
 

cmake/ci.cmake

@@ -373,9 +373,10 @@ file(GLOB_RECURSE INDENT_FILES
 set(include_dir ${PROJECT_SOURCE_DIR}/single_include/nlohmann)
 set(tool_dir ${PROJECT_SOURCE_DIR}/tools/amalgamate)
 add_custom_target(ci_test_amalgamation
-    COMMAND rm -fr ${include_dir}/json.hpp~ ${include_dir}/json_fwd.hpp~
+    COMMAND rm -fr ${include_dir}/json.hpp~ ${include_dir}/json_fwd.hpp~ ${include_dir}/json_literals.hpp~
     COMMAND cp ${include_dir}/json.hpp ${include_dir}/json.hpp~
     COMMAND cp ${include_dir}/json_fwd.hpp ${include_dir}/json_fwd.hpp~
+    COMMAND cp ${include_dir}/json_literals.hpp ${include_dir}/json_literals.hpp~
 
     COMMAND ${Python3_EXECUTABLE} -mvenv venv_astyle
     COMMAND venv_astyle/bin/pip3 --quiet install -r ${CMAKE_SOURCE_DIR}/tools/astyle/requirements.txt
@@ -383,10 +384,12 @@ add_custom_target(ci_test_amalgamation
 
     COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json.json -s .
     COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json_fwd.json -s .
+    COMMAND cp ${PROJECT_SOURCE_DIR}/include/nlohmann/json_literals.hpp ${include_dir}/json_literals.hpp
     COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=none ${include_dir}/json.hpp ${include_dir}/json_fwd.hpp
 
     COMMAND diff ${include_dir}/json.hpp~ ${include_dir}/json.hpp
     COMMAND diff ${include_dir}/json_fwd.hpp~ ${include_dir}/json_fwd.hpp
+    COMMAND diff ${include_dir}/json_literals.hpp~ ${include_dir}/json_literals.hpp
 
     COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=orig ${INDENT_FILES}
     COMMAND for FILE in `find . -name '*.orig'`\; do false \; done

docs/mkdocs/docs/api/basic_json/basic_json.md

@@ -139,8 +139,8 @@ basic_json(basic_json&& other) noexcept;
 
     - In case of a `#!json null` type, [invalid_iterator.206](../../home/exceptions.md#jsonexceptioninvalid_iterator206)
       is thrown.
-    - In case of other primitive types (number, boolean, or string), `first` must be `begin()` and `last` must be
-      `end()`. In this case, the value is copied. Otherwise,
+    - In case of other primitive types (number, boolean, string, or binary), `first` must be `begin()` and `last`
+      must be `end()`. In this case, the value is copied. Otherwise,
       [`invalid_iterator.204`](../../home/exceptions.md#jsonexceptioninvalid_iterator204) is thrown.
     - In case of structured types (array, object), the constructor behaves as similar versions for `std::vector` or
       `std::map`; that is, a JSON array or object is constructed from the values in the range.
@@ -242,8 +242,8 @@ basic_json(basic_json&& other) noexcept;
       and `last` are not compatible (i.e., do not belong to the same JSON value). In this case, the range
       `[first, last)` is undefined.
     - Throws [`invalid_iterator.204`](../../home/exceptions.md#jsonexceptioninvalid_iterator204) if iterators `first`
-      and `last` belong to a primitive type (number, boolean, or string), but `first` does not point to the first
-      element anymore. In this case, the range `[first, last)` is undefined. See the example code below.
+      and `last` belong to a primitive type (number, boolean, string, or binary), but `first` does not point to the
+      first element anymore. In this case, the range `[first, last)` is undefined. See the example code below.
     - Throws [`invalid_iterator.206`](../../home/exceptions.md#jsonexceptioninvalid_iterator206) if iterators `first`
       and `last` belong to a `#!json null` value. In this case, the range `[first, last)` is undefined.
 8. (none)
@@ -423,6 +423,8 @@ basic_json(basic_json&& other) noexcept;
 4. Since version 3.2.0.
 5. Since version 1.0.0.
 6. Since version 1.0.0.
-7. Since version 1.0.0.
+7. Since version 1.0.0. Fixed in version 3.13.0 to also check the iterator range for binary values; before, a range
+   that did not cover the whole value (such as `(end(), end())`) was accepted and the whole binary value was copied,
+   unlike the other primitive types.
 8. Since version 1.0.0.
 9. Since version 1.0.0.

docs/mkdocs/docs/api/basic_json/clear.md

@@ -7,15 +7,15 @@ void clear() noexcept;
 Clears the content of a JSON value and resets it to the default value as if [`basic_json(value_t)`](basic_json.md) would
 have been called with the current value type from [`type()`](type.md):
 
-| Value type | initial value        |
-|------------|----------------------|
-| null       | `null`               |
-| boolean    | `false`              |
-| string     | `""`                 |
-| number     | `0`                  |
-| binary     | An empty byte vector |
-| object     | `{}`                 |
-| array      | `[]`                 |
+| Value type | initial value                           |
+|------------|-----------------------------------------|
+| null       | `null`                                  |
+| boolean    | `false`                                 |
+| string     | `""`                                    |
+| number     | `0`                                     |
+| binary     | An empty byte vector with no subtype    |
+| object     | `{}`                                    |
+| array      | `[]`                                    |
 
 Has the same effect as calling
 
@@ -56,3 +56,4 @@ All iterators, pointers, and references related to this container are invalidate
 
 - Added in version 1.0.0.
 - Added support for binary types in version 3.8.0.
+- Fixed in version 3.13.0 to also clear the subtype of a binary value; before, the subtype was left unchanged.

docs/mkdocs/docs/api/basic_json/contains.md

@@ -58,6 +58,10 @@ Logarithmic in the size of the JSON object.
 
 - This method always returns `#!cpp false` when executed on a JSON type that is not an object.
 - This method can be executed on any JSON value type.
+- Calling this function with an integer argument (for example, `#!cpp contains(0)`) does not compile: such an argument
+  would otherwise implicitly convert to a null `#!cpp const char*` and, from there, cause undefined behavior when
+  constructing a `#!cpp std::string` for the object key. To check for an array element instead, use [`at`](at.md),
+  [`operator[]`](operator%5B%5D.md), or compare against [`size`](size.md).
 
 !!! info "Postconditions"
 
@@ -117,3 +121,5 @@ Logarithmic in the size of the JSON object.
 1. Added in version 3.11.0.
 2. Added in version 3.6.0. Extended template `KeyType` to support comparable types in version 3.11.0.
 3. Added in version 3.7.0.
+4. Deleted overloads for integral key types added in version 3.13.0 to reject such calls at compile time instead of
+   causing undefined behavior at runtime.

docs/mkdocs/docs/api/basic_json/count.md

@@ -40,7 +40,11 @@ Logarithmic in the size of the JSON object.
 
 ## Notes
 
-This method always returns `0` when executed on a JSON type that is not an object.
+- This method always returns `0` when executed on a JSON type that is not an object.
+- Calling this function with an integer argument (for example, `#!cpp count(0)`) does not compile: such an argument
+  would otherwise implicitly convert to a null `#!cpp const char*` and, from there, cause undefined behavior when
+  constructing a `#!cpp std::string` for the object key. To check for an array element instead, use [`at`](at.md),
+  [`operator[]`](operator%5B%5D.md), or compare against [`size`](size.md).
 
 ## Examples
 
@@ -81,3 +85,5 @@ This method always returns `0` when executed on a JSON type that is not an objec
 
 1. Added in version 3.11.0.
 2. Added in version 1.0.0. Changed parameter `key` type to `KeyType&&` in version 3.11.0.
+3. Deleted overload for integral key types added in version 3.13.0 to reject such calls at compile time instead of
+   causing undefined behavior at runtime.

docs/mkdocs/docs/api/basic_json/find.md

@@ -44,7 +44,11 @@ Logarithmic in the size of the JSON object.
 
 ## Notes
 
-This method always returns `end()` when executed on a JSON type that is not an object.
+- This method always returns `end()` when executed on a JSON type that is not an object.
+- Calling this function with an integer argument (for example, `#!cpp find(0)`) does not compile: such an argument
+  would otherwise implicitly convert to a null `#!cpp const char*` and, from there, cause undefined behavior when
+  constructing a `#!cpp std::string` for the object key. To access an array element instead, use [`at`](at.md),
+  [`operator[]`](operator%5B%5D.md), or compare against [`size`](size.md).
 
 ## Examples
 
@@ -85,3 +89,5 @@ This method always returns `end()` when executed on a JSON type that is not an o
 
 1. Added in version 3.11.0.
 2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.
+3. Deleted overloads for integral key types added in version 3.13.0 to reject such calls at compile time instead of
+   causing undefined behavior at runtime.

docs/mkdocs/docs/api/basic_json/from_cbor.md

@@ -80,8 +80,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   the end of the file was not reached when `strict` was set to true
 - Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if unsupported features from CBOR were
   used in the given input or if the input is not valid CBOR
-- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a string was expected as a map key,
-  but not found
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a map key is not a string (keys of other
+  types are not supported, as JSON object keys are always strings) or a string is malformed
 
 ## Complexity
 

docs/mkdocs/docs/api/basic_json/from_msgpack.md

@@ -73,8 +73,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   the end of the file was not reached when `strict` was set to true
 - Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if unsupported features from
   MessagePack were used in the given input or if the input is not valid MessagePack
-- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a string was expected as a map key,
-  but not found
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a map key is not a string (keys of other
+  types are not supported, as JSON object keys are always strings) or a string is malformed
 
 ## Complexity
 

docs/mkdocs/docs/api/basic_json/insert.md

@@ -195,5 +195,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
 1. Added in version 1.0.0.
 2. Added in version 1.0.0.
 3. Added in version 1.0.0.
-4. Added in version 1.0.0.
+4. Added in version 1.0.0. Fixed in version 3.13.0 to copy the values before inserting; before, an `ilist` that
+   referred to elements of the array being inserted into could insert wrong values, because the range insert could
+   move from or shift an element before it was copied.
 5. Added in version 3.0.0.

docs/mkdocs/docs/api/basic_json/operator[].md

@@ -70,6 +70,9 @@ Strong exception safety: if an exception occurs, the original value stays intact
 1. The function can throw the following exceptions:
     - Throws [`type_error.305`](../../home/exceptions.md#jsonexceptiontype_error305) if the JSON value is not an array
       or null; in that case, using the `[]` operator with an index makes no sense.
+    - Throws `#!cpp std::length_error` if `idx` equals the maximum value of `size_type`; the array is left unchanged.
+      (This is the one index for which growing the array to hold it cannot be expressed as a `size_type` size, the same
+      way an oversized [`resize`](https://en.cppreference.com/w/cpp/container/vector/resize) throws.)
 2. The function can throw the following exceptions:
     - Throws [`type_error.305`](../../home/exceptions.md#jsonexceptiontype_error305) if the JSON value is not an object
       or null; in that case, using the `[]` operator with a key makes no sense.
@@ -257,7 +260,8 @@ Strong exception safety: if an exception occurs, the original value stays intact
 
 ## Version history
 
-1. Added in version 1.0.0.
+1. Added in version 1.0.0. Fixed in version 3.13.0 to throw `#!cpp std::length_error` instead of emptying the array and
+   accessing it out of bounds when `idx` equals the maximum value of `size_type`.
 2. Added in version 1.0.0. Added overloads for `T* key` in version 1.1.0. Removed overloads for `T* key` (replaced by 3)
    in version 3.11.0.
 3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as

docs/mkdocs/docs/api/basic_json/parse.md

@@ -88,7 +88,12 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 ## Exceptions
 
 - Throws [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) in case of an unexpected token, or
-  empty input like a null `FILE*` or `char*` pointer.
+  empty input like a null `FILE*` or `char*` pointer, or an `std::istream` without a stream buffer
+  (`#!cpp i.rdbuf() == nullptr`, for instance `#!cpp std::istream(nullptr)`).
+- If reading from an `std::istream` reaches the end of the input and `eofbit` is part of the stream's
+  [`exceptions()`](https://en.cppreference.com/w/cpp/io/basic_ios/exceptions) mask, the `std::ios_base::failure`
+  thrown by the stream itself propagates instead of a `parse_error`, the same as it would for the standard library's
+  own extraction operators.
 
 ## Complexity
 
@@ -254,6 +259,8 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
 - `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
   it as end of input; planned to become the default in version 4.0.0.
+- Extended empty-input detection to also cover an `std::istream` without a stream buffer, and fixed a crash
+  (`std::terminate`) when parsing from an `std::istream` with `eofbit` in its exception mask, in version 3.13.0.
 
 !!! warning "Deprecation"
 

docs/mkdocs/docs/api/basic_json/parser_callback_t.md

@@ -100,3 +100,6 @@ the latter case, it is skipped completely, or replaced by `null` if it is the to
 - Added in version 1.0.0.
 - Fixed in version 3.13.0 to also remove discarded values from a parent object; before, discarding an array or a value
   stored under an object key left a discarded member behind, which made the parse result serialize to invalid JSON.
+- Fixed in version 3.13.0 so that discarding an array or object at its start event also hides its content from the
+  callback, as documented above; before, the callback was still called for the content, and the key of every member of
+  a discarded object was kept in memory until the parse ended.

docs/mkdocs/docs/api/basic_json/swap.md

@@ -6,7 +6,9 @@ void swap(reference other) noexcept (
     std::is_nothrow_move_constructible<value_t>::value &&
     std::is_nothrow_move_assignable<value_t>::value &&
     std::is_nothrow_move_constructible<json_value>::value &&
-    std::is_nothrow_move_assignable<json_value>::value
+    std::is_nothrow_move_assignable<json_value>::value &&
+    std::is_nothrow_move_constructible<json_base_class_t>::value &&
+    std::is_nothrow_move_assignable<json_base_class_t>::value
 );
 
 // (2)
@@ -14,7 +16,9 @@ friend void swap(reference left, reference right) noexcept (
     std::is_nothrow_move_constructible<value_t>::value &&
     std::is_nothrow_move_assignable<value_t>::value &&
     std::is_nothrow_move_constructible<json_value>::value &&
-    std::is_nothrow_move_assignable<json_value>::value
+    std::is_nothrow_move_assignable<json_value>::value &&
+    std::is_nothrow_move_constructible<json_base_class_t>::value &&
+    std::is_nothrow_move_assignable<json_base_class_t>::value
 );
 
 // (3)
@@ -37,11 +41,15 @@ void swap(typename binary_t::container_type& other);
    individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated. If macro
    [`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) is defined to `#!cpp 1`, the
    [`start_pos()`](start_pos.md)/[`end_pos()`](end_pos.md) diagnostic positions are exchanged along with the value.
+   The [`json_base_class_t`](json_base_class_t.md) subobject is exchanged along with the value as well, the same way it
+   is copied or moved by the copy/move constructors and assignment operators.
 2. Exchanges the contents of the JSON value from `left` with those of `right`. Does not invoke any move, copy, or swap
    operations on individual elements. All iterators and references remain valid. The past-the-end iterator is
    invalidated. Implemented as a friend function callable via ADL. If macro
    [`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) is defined to `#!cpp 1`, the
    [`start_pos()`](start_pos.md)/[`end_pos()`](end_pos.md) diagnostic positions are exchanged along with the value.
+   The [`json_base_class_t`](json_base_class_t.md) subobject is exchanged along with the value as well, the same way it
+   is copied or moved by the copy/move constructors and assignment operators.
 3. Exchanges the contents of a JSON array with those of `other`. Does not invoke any move, copy, or swap operations on
    individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated. 
 4. Exchanges the contents of a JSON object with those of `other`. Does not invoke any move, copy, or swap operations on
@@ -164,8 +172,8 @@ Constant.
 
 ## Version history
 
-1. Since version 1.0.0.
-2. Since version 1.0.0.
+1. Since version 1.0.0. Exchanges the `json_base_class_t` subobject along with the value since version 3.13.0.
+2. Since version 1.0.0. Exchanges the `json_base_class_t` subobject along with the value since version 3.13.0.
 3. Since version 1.0.0.
 4. Since version 1.0.0.
 5. Since version 1.0.0.

docs/mkdocs/docs/api/basic_json/to_bson.md

@@ -43,6 +43,9 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 - Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a document, array,
   string, or binary value exceeds the range of the 32-bit BSON length field; example:
   `"BSON length 2147483661 exceeds maximum of 2147483647"`
+- Throws [`out_of_range.415`](../../home/exceptions.md#jsonexceptionout_of_range415) if the subtype of a binary value
+  exceeds 255, the maximum of the BSON binary subtype; example:
+  `"subtype 70000 is too large for the BSON binary subtype (max 255)"`
 
 ## Complexity
 
@@ -78,3 +81,4 @@ pass before anything is written.
 
 - Added in version 3.4.0.
 - Linear in the size of `j`, and no longer limited by the call stack for deeply nested values, since version 3.13.0.
+- `out_of_range.415` is now detected before anything is written, like the other exceptions above, since version 3.13.0.

docs/mkdocs/docs/api/basic_json/to_msgpack.md

@@ -76,3 +76,6 @@ Linear in the size of the JSON value `j`.
 
 - Added in version 2.0.9.
 - Throws `out_of_range.412` and `out_of_range.415` since version 3.13.0.
+- Fixed in version 3.13.0 to serialize `number_integer_t`/`number_unsigned_t` pairs of different width correctly;
+  before, integers could be serialized with the wrong value if `number_integer_t` was narrower than
+  `number_unsigned_t`.

docs/mkdocs/docs/api/basic_json/value.md

@@ -52,6 +52,14 @@ This is equivalent to Python's `dict.get(key, default)`.
     - Unlike [`operator[]`](operator[].md), this function does not implicitly add an element to the position defined by
      `key`/`ptr` key. This function is furthermore also applicable to const objects.
 
+!!! note "Integer keys"
+
+    Calling this function with an integer `key` argument (for example, `#!cpp value(0, 1)`) does not compile in
+    C++11, where `object_comparator_t` is not transparent: such an argument would otherwise implicitly convert to a
+    null `#!cpp const char*` and, from there, cause undefined behavior when constructing a `#!cpp std::string` for the
+    object key. To access an array element with a default value, use [`at`](at.md) together with a `#!cpp try`/`#!cpp
+    catch` block, or compare against [`size`](size.md) instead.
+
 ## Template parameters
 
 `KeyType`
@@ -184,7 +192,9 @@ changes to any JSON value.
 
 ## Version history
 
-1. Added in version 1.0.0. Changed parameter `default_value` type from `const ValueType&` to `ValueType&&` in version 3.11.0.
+1. Added in version 1.0.0. Changed parameter `default_value` type from `const ValueType&` to `ValueType&&` in version
+   3.11.0. Deleted overload for integral key types added in version 3.13.0 to reject such calls at compile time
+   instead of causing undefined behavior at runtime.
 2. Added in version 3.11.0. Made `ValueType` the first template parameter in version 3.11.2.
 3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving
    `ptr` through an array unexpectedly threw `out_of_range` instead of returning the resolved element (or

docs/mkdocs/docs/api/macros/index.md

@@ -28,6 +28,7 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_HAS_RANGES**](json_has_ranges.md) - control `std::ranges` support
 - [**JSON_HAS_STD_FORMAT**](json_has_std_format.md) - control `std::format`/`std::formatter` support
 - [**JSON_HAS_THREE_WAY_COMPARISON**](json_has_three_way_comparison.md) - control 3-way comparison support
+- [**JSON_NO_AUTOMATIC_UDLS**](json_no_automatic_udls.md) - do not include the user-defined string literals (UDLs) automatically
 - [**JSON_NO_IO**](json_no_io.md) - switch off functions relying on certain C++ I/O headers
 - [**JSON_NO_THREAD_LOCAL**](json_no_thread_local.md) - switch off the use of `thread_local` storage
 - [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers

docs/mkdocs/docs/api/macros/json_no_automatic_udls.md

@@ -0,0 +1,68 @@
+# JSON_NO_AUTOMATIC_UDLS
+
+```cpp
+#define JSON_NO_AUTOMATIC_UDLS
+```
+
+When defined, `<nlohmann/json.hpp>` does not include `<nlohmann/json_literals.hpp>`, so the user-defined string
+literals [`operator""_json`](../operator_literal_json.md) and
+[`operator""_json_pointer`](../operator_literal_json_pointer.md) are not declared. Include
+`<nlohmann/json_literals.hpp>` in the files that use them.
+
+The literals are ordinary inline functions whose bodies call the parser, so every translation unit that includes them
+instantiates the parser — even if it never parses anything itself. Defining `JSON_NO_AUTOMATIC_UDLS` for a whole project
+avoids this cost in translation units that do not parse (e.g., ones that only define types and conversions or pass
+`json` values around) and reduces their compile time.
+
+## Default definition
+
+By default, `#!cpp JSON_NO_AUTOMATIC_UDLS` is not defined, and `<nlohmann/json.hpp>` includes
+`<nlohmann/json_literals.hpp>`.
+
+```cpp
+#undef JSON_NO_AUTOMATIC_UDLS
+```
+
+## Notes
+
+!!! info "Header `<nlohmann/json_literals.hpp>`"
+
+    The header includes `<nlohmann/json.hpp>` itself and places the literals according to
+    [`JSON_USE_GLOBAL_UDLS`](json_use_global_udls.md). It is part of the multi-header sources (`include/nlohmann`)
+    and of the single-header sources (`single_include/nlohmann`), next to `json.hpp`.
+
+!!! info "C++ modules"
+
+    The `nlohmann.json` [module](../../features/modules.md) always exports the literals, regardless of this macro.
+
+## Examples
+
+??? example
+
+    The code below includes the library without the literals and adds them in a single translation unit.
+
+    ```cpp
+    // compiled with -DJSON_NO_AUTOMATIC_UDLS for the whole project
+    #include <nlohmann/json.hpp>
+
+    // this file uses the literals, so it includes them explicitly
+    #include <nlohmann/json_literals.hpp>
+
+    int main()
+    {
+        auto j = R"({"foo": 42})"_json;
+        return j.at("/foo"_json_pointer) == 42 ? 0 : 1;
+    }
+    ```
+
+    Without the include of `<nlohmann/json_literals.hpp>`, the code would fail to compile.
+
+## See also
+
+- [`operator""_json`](../operator_literal_json.md)
+- [`operator""_json_pointer`](../operator_literal_json_pointer.md)
+- [`JSON_USE_GLOBAL_UDLS`](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
+
+## Version history
+
+- Added in version 3.13.0.

docs/mkdocs/docs/api/macros/json_strict_nul_handling.md

@@ -16,7 +16,8 @@ byte is still not rejected:
   [`from_msgpack`](../basic_json/from_msgpack.md), [`from_ubjson`](../basic_json/from_ubjson.md)) are never affected: there, `0x00` is ordinary data.
 - A bare `const char*` pointer has no length of its own, so its length is still determined with `strlen()`. The first
   NUL byte therefore still marks the end of the input, and nothing after it is read.
-- One trailing `'\0'` at the end of a `char` array (e.g., a string literal) is trimmed; see the warning below.
+- One trailing `'\0'` at the end of a `char`, `wchar_t`, `char16_t`, `char32_t`, or (C++20) `char8_t` array (e.g., a
+  string literal) is trimmed; see the warning below.
 
 ## Default definition
 
@@ -57,13 +58,15 @@ The default value is `0` (disabled — existing behavior is preserved).
     This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
     effect.
 
-    Enabling it also changes how a `char` array (including a string literal, e.g. `json::parse("123")`) is read: such
-    an array normally carries a trailing `'\0'` contributed by the compiler, not by the source text. With this macro
-    enabled, that one trailing byte is trimmed if present so that parsing a string literal keeps working; every other
-    byte in the array - including any `'\0'` that is not the very last element - is read as real data and rejected
-    like any other unexpected byte. Arrays of any other element type (`unsigned char`, `std::uint8_t`, ...), as used
-    for CBOR or MessagePack, are never affected by this trimming; their full extent - including a genuine trailing
-    `0x00` - is always preserved, in both states of this macro.
+    Enabling it also changes how an array of a text-literal element type (`char`, `wchar_t`, `char16_t`, `char32_t`,
+    or, since C++20, `char8_t` - including a string literal, e.g. `json::parse("123")` or `json::parse(L"123")`) is
+    read: such an array normally carries a trailing `'\0'` contributed by the compiler, not by the source text. With
+    this macro enabled, that one trailing element is trimmed if present so that parsing a string literal keeps
+    working, for any of these character types; every other element in the array - including any `'\0'` that is not
+    the very last element - is read as real data and rejected like any other unexpected byte. Arrays of any other
+    element type (`unsigned char`, `std::uint8_t`, ...), as used for CBOR or MessagePack, are never affected by this
+    trimming; their full extent - including a genuine trailing `0x00` - is always preserved, in both states of this
+    macro.
 
 !!! note "ABI compatibility"
 

docs/mkdocs/docs/api/macros/json_use_global_udls.md

@@ -15,7 +15,7 @@ The default value is `1`.
 #define JSON_USE_GLOBAL_UDLS 1
 ```
 
-When the macro is not defined, the library will define it to its default value.
+When the macro is not defined, the library behaves as if it were defined to its default value.
 
 ## Notes
 
@@ -32,6 +32,11 @@ When the macro is not defined, the library will define it to its default value.
     [`JSON_GlobalUDLs`](../../integration/cmake.md#json_globaludls) (`ON` by default) which defines
     `JSON_USE_GLOBAL_UDLS` accordingly.
 
+!!! info "Leaving out the literals"
+
+    If [`JSON_NO_AUTOMATIC_UDLS`](json_no_automatic_udls.md) is defined, the literals are only declared where
+    `<nlohmann/json_literals.hpp>` is included; this macro then applies to that header.
+
 ## Examples
 
 ??? example "Example 1: Default behavior"
@@ -92,6 +97,7 @@ When the macro is not defined, the library will define it to its default value.
 
 - [`operator""_json`](../operator_literal_json.md)
 - [`operator""_json_pointer`](../operator_literal_json_pointer.md)
+- [`JSON_NO_AUTOMATIC_UDLS`](json_no_automatic_udls.md) - do not include the user-defined string literals automatically
 - [:simple-cmake: JSON_GlobalUDLs](../../integration/cmake.md#json_globaludls) - CMake option to control the macro
 
 ## Version history

docs/mkdocs/docs/api/operator_gtgt.md

@@ -18,9 +18,18 @@ Deserializes an input stream to a JSON value.
 
 the stream `i`
 
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in `j`.
+
 ## Exceptions
 
-- Throws [`parse_error.101`](../home/exceptions.md#jsonexceptionparse_error101) in case of an unexpected token.
+- Throws [`parse_error.101`](../home/exceptions.md#jsonexceptionparse_error101) in case of an unexpected token, or if
+  `i` has no stream buffer (`#!cpp i.rdbuf() == nullptr`, for instance `#!cpp std::istream(nullptr)`).
+- If reading from `i` reaches the end of the input and `eofbit` is part of `i`'s
+  [`exceptions()`](https://en.cppreference.com/w/cpp/io/basic_ios/exceptions) mask, the `std::ios_base::failure`
+  thrown by `i` itself propagates instead of a `parse_error`, the same as it would for the standard library's own
+  extraction operators.
 
 ## Complexity
 
@@ -118,3 +127,7 @@ being read.
   it as end of input; planned to become the default in version 4.0.0.
 - `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave the character that terminates a number in
   the stream; planned to become the default in version 4.0.0.
+- Fixed a null pointer dereference for an `std::istream` without a stream buffer (now throws `parse_error.101`), and a
+  crash (`std::terminate`) when `i` has `eofbit` in its exception mask, in version 3.13.0.
+- Changed to the strong exception safety guarantee in version 3.13.0: `j` is no longer left with a partially parsed
+  value if parsing throws.

docs/mkdocs/docs/api/operator_literal_json.md

@@ -18,7 +18,9 @@ using namespace nlohmann;
 ```
 
 This is suggested to ease migration to the next major version release of the library. See
-[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details.
+[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details. The operator is declared in header
+`<nlohmann/json_literals.hpp>`, which `<nlohmann/json.hpp>` includes unless
+[`JSON_NO_AUTOMATIC_UDLS`](macros/json_no_automatic_udls.md) is defined.
 
 ## Parameters
 
@@ -59,6 +61,8 @@ Linear.
 ## See also
 
 - [Creating JSON values](../features/creating_values.md) - the article on creating JSON values
+- [JSON_NO_AUTOMATIC_UDLS](macros/json_no_automatic_udls.md) - do not include the user-defined string literals
+  automatically
 
 ## Version history
 

docs/mkdocs/docs/api/operator_literal_json_pointer.md

@@ -17,7 +17,9 @@ using namespace nlohmann::literals::json_literals;
 using namespace nlohmann;
 ```
 This is suggested to ease migration to the next major version release of the library. See
-[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details.
+[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details. The operator is declared in header
+`<nlohmann/json_literals.hpp>`, which `<nlohmann/json.hpp>` includes unless
+[`JSON_NO_AUTOMATIC_UDLS`](macros/json_no_automatic_udls.md) is defined.
 
 ## Parameters
 
@@ -58,6 +60,8 @@ Linear.
 ## See also
 
 - [json_pointer](json_pointer/index.md) - type to represent JSON Pointers
+- [JSON_NO_AUTOMATIC_UDLS](macros/json_no_automatic_udls.md) - do not include the user-defined string literals
+  automatically
 
 ## Version history
 

docs/mkdocs/docs/api/ordered_map.md

@@ -28,6 +28,11 @@ A minimal map-like container that preserves insertion order for use within [`nlo
 The type uses a `std::vector` to store object elements. Therefore, adding elements can yield a reallocation in which
 case all iterators (including the `end()` iterator) and all references to the elements are invalidated.
 
+When the storage grows, the keys are copied and the mapped values are moved to the new storage. A plain `std::vector`
+would copy the whole elements instead, because their `#!cpp const` keys make them not nothrow move constructible; for
+[`ordered_json`](ordered_json.md), this would be a deep copy of every nested value. The values are only copied if
+`T` is not default constructible or not nothrow move assignable.
+
 ## Member types
 
 - **key_type** - key type (`Key`)
@@ -56,6 +61,11 @@ std::equal_to<>     // since C++14
 - **find**
 - **insert**
 
+## Exception safety
+
+**emplace**, **operator\[\]**, and **insert(value)** have the strong exception guarantee: if an exception is thrown (for
+instance, because copying a key or allocating memory fails), the contents of the container are unchanged.
+
 ## Complexity
 
 Because the elements are stored in a `std::vector` in insertion order, there is no index to look a key up by. Every
@@ -122,3 +132,4 @@ This differs from `#!cpp std::map`, where the same operations are O(log n).
 
 - Added in version 3.9.0 to implement [`nlohmann::ordered_json`](ordered_json.md).
 - Added **key_compare** member in version 3.11.0.
+- Changed in version 3.13.0: growing the storage moves the mapped values instead of copying them.

docs/mkdocs/docs/features/binary_formats/cbor.md

@@ -174,7 +174,20 @@ The library maps CBOR types to JSON value types as follows:
 
 !!! warning "Object keys"
 
-    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected.
+    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps
+    with keys other than text strings (major type 3) are rejected with a
+    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with `allow_exceptions` set
+    to `false`, a discarded value) naming the type of the key that was found, for instance:
+
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found an unsigned integer; last byte: 0x01
+    ```
+
+    This applies to the [SAX interface](../parsing/sax_interface.md) as well, as the key is read before it is passed
+    on. This is a deliberate restriction of the library's JSON value model, not an oversight: formats built on CBOR
+    maps with integer keys, such as COSE ([RFC 9052](https://www.rfc-editor.org/rfc/rfc9052.html)) or CWT
+    ([RFC 8392](https://www.rfc-editor.org/rfc/rfc8392.html)), cannot be read with this library and need a
+    general-purpose CBOR library instead.
 
 !!! warning "UTF-8 validation of text strings"
 

docs/mkdocs/docs/features/binary_formats/messagepack.md

@@ -138,6 +138,21 @@ The library maps MessagePack types to JSON value types as follows:
 
     Any MessagePack output created by `to_msgpack` can be successfully parsed by `from_msgpack`.
 
+!!! warning "Object keys"
+
+    MessagePack allows map keys of any type, whereas JSON only allows strings as keys in object values. Like the
+    JSON-compatible [profile](https://github.com/msgpack/msgpack/blob/master/spec.md#profile) sketched in the
+    MessagePack specification, this library restricts map keys to `str` values. Maps with keys of any other type are
+    rejected with a [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
+    `allow_exceptions` set to `false`, a discarded value) naming the type of the key that was found, for instance:
+
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found nil; last byte: 0xC0
+    ```
+
+    This applies to the [SAX interface](../parsing/sax_interface.md) as well, as the key is read before it is passed
+    on. Such input needs a general-purpose MessagePack library instead.
+
 !!! warning "UTF-8 validation of string values"
 
     The MessagePack specification requires `str` values (`fixstr`, `str 8`, `str 16`, `str 32`) to be valid UTF-8.

docs/mkdocs/docs/features/macros.md

@@ -83,6 +83,15 @@ When defined, default parse and serialize functions for enums are excluded and h
 
 See [full documentation of `JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md).
 
+## `JSON_NO_AUTOMATIC_UDLS`
+
+When defined, `<nlohmann/json.hpp>` does not include `<nlohmann/json_literals.hpp>` with the user-defined string literals
+`operator""_json` and `operator""_json_pointer`. This reduces the compile time of translation units that do not use
+them, because the literals instantiate the parser in every translation unit that includes them. Include
+`<nlohmann/json_literals.hpp>` where the literals are needed.
+
+See [full documentation of `JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md).
+
 ## `JSON_NO_IO`
 
 When defined, headers `<cstdio>`, `<ios>`, `<iosfwd>`, `<istream>`, and `<ostream>` are not included and parse functions

docs/mkdocs/docs/features/modules.md

@@ -40,6 +40,9 @@ Only the following symbols are exported from `nlohmann.json`:
 - `nlohmann::literals::json_literals::operator""_json`
 - `nlohmann::literals::json_literals::operator""_json_pointer`
 
+The module always exports the two user-defined string literals, even if
+[`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md) is defined when building it.
+
 Additionally, the following `nlohmann::detail` symbols are exported, solely to work around an MSVC compilation issue
 ([#3970](https://github.com/nlohmann/json/issues/3970)). They are implementation details, not part of the public API,
 and should not be used directly:

docs/mkdocs/docs/features/types/template_parameters.md

@@ -389,6 +389,7 @@ using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
 | Functionality                                                                                                                     | Additional requirement                                                                                                                                                                       |
 |-----------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | [`diff`](../../api/basic_json/diff.md), [`items`](../../api/basic_json/items.md), [`std::hash`](../../api/basic_json/std_hash.md) | conversion of a `#!cpp std::size_t` to `StringType`: either assignability from the result of `#!cpp std::to_string`, or an ADL overload `#!cpp void int_to_string(StringType&, std::size_t)` |
+| [`operator/(std::size_t)`](../../api/json_pointer/operator_slash.md)                                                              | the same conversion of a `#!cpp std::size_t` to `StringType` as `diff`, `items`, and `std::hash` above                                                                                       |
 | [`std::hash<basic_json>`](../../api/basic_json/std_hash.md)                                                                       | additionally a specialization of `#!cpp std::hash<StringType>`                                                                                                                               |
 | [`to_bson`](../../api/basic_json/to_bson.md)                                                                                      | `find(value_type)` and `npos`                                                                                                                                                                |
 | [`parse`](../../api/basic_json/parse.md) from a `string_t`                                                                        | the input adapters must accept it; otherwise pass a character range                                                                                                                          |

docs/mkdocs/docs/home/exceptions.md

@@ -343,13 +343,20 @@ A string could not be read from a [binary format](../features/binary_formats/ind
 string was read where one was required (for instance as a map key), the string's length specification is invalid, or
 the string's bytes are not valid UTF-8.
 
+CBOR and MessagePack allow map keys of any type, but JSON object keys are always strings. Maps with keys of any other
+type (for instance integers or `null`) are therefore not supported; see the notes on
+[CBOR](../features/binary_formats/cbor.md) and [MessagePack](../features/binary_formats/messagepack.md).
+
 !!! failure "Example messages"
 
     ```
-    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found an unsigned integer; last byte: 0x01
     ```
     ```
-    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack string: expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0xFF
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found nil; last byte: 0xC0
+    ```
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x7C
     ```
     ```
     [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing UBJSON char: byte after 'C' must be in range 0x00..0x7F; last byte: 0x82

docs/mkdocs/docs/home/license.md

@@ -19,3 +19,5 @@ The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed und
 The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the [MIT License](https://opensource.org/licenses/MIT) (see above). Copyright © 2009 [Florian Loitsch](https://florian.loitsch.com/)
 
 The class contains a copy of [Hedley](https://nemequ.github.io/hedley/) from Evan Nemerson which is licensed as [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
+
+The class contains an adapted version of the Eisel-Lemire algorithm and its table of powers of five from [fast_float](https://github.com/fastfloat/fast_float) by Daniel Lemire and contributors, which is available under the [MIT License](https://opensource.org/licenses/MIT) (used here), the Apache 2.0 License, and the Boost Software License. Copyright © 2021 The fast_float authors

docs/mkdocs/docs/integration/index.md

@@ -15,4 +15,7 @@ Clang).
 
 You can further use file
 [`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp)
-for forward declarations.
+for forward declarations, and file
+[`single_include/nlohmann/json_literals.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_literals.hpp)
+for the user-defined string literals if you define
+[`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md).

docs/mkdocs/mkdocs.yml

@@ -293,6 +293,7 @@ nav:
           - 'JSON_HAS_STATIC_RTTI': api/macros/json_has_static_rtti.md
           - 'JSON_HAS_STD_FORMAT': api/macros/json_has_std_format.md
           - 'JSON_HAS_THREE_WAY_COMPARISON': api/macros/json_has_three_way_comparison.md
+          - 'JSON_NO_AUTOMATIC_UDLS': api/macros/json_no_automatic_udls.md
           - 'JSON_NOEXCEPTION': api/macros/json_noexception.md
           - 'JSON_NO_IO': api/macros/json_no_io.md
           - 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md

include/nlohmann/detail/bit_ops.hpp

@@ -0,0 +1,81 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <cstdint> // uint64_t
+
+#include <nlohmann/detail/abi_macros.hpp>
+
+// Portable bit-level helpers for the number and string scanners. They use
+// compiler builtins where available and plain C++ otherwise, so they need no
+// platform headers and work regardless of byte order.
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+/// number of leading zero bits of x (x != 0)
+inline int count_leading_zeros(std::uint64_t x) noexcept
+{
+#if defined(__GNUC__) || defined(__clang__)
+    return __builtin_clzll(x);
+#else
+    int n = 0;
+    for (int shift = 32; shift != 0; shift >>= 1)
+    {
+        if ((x >> (64 - shift)) == 0)
+        {
+            n += shift;
+            x <<= shift;
+        }
+    }
+    return n;
+#endif
+}
+
+/// the 128-bit product of two 64-bit numbers
+struct uint128_parts
+{
+    std::uint64_t low;
+    std::uint64_t high;
+};
+
+inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexcept
+{
+#if defined(__SIZEOF_INT128__)
+    __extension__ using uint128 = unsigned __int128;
+    const uint128 r = static_cast<uint128>(a) * b;
+    return {static_cast<std::uint64_t>(r), static_cast<std::uint64_t>(r >> 64u)};
+#else
+    const std::uint64_t a_lo = a & 0xFFFFFFFFu;
+    const std::uint64_t a_hi = a >> 32u;
+    const std::uint64_t b_lo = b & 0xFFFFFFFFu;
+    const std::uint64_t b_hi = b >> 32u;
+    const std::uint64_t lo_lo = a_lo * b_lo;
+    const std::uint64_t hi_lo = a_hi * b_lo;
+    const std::uint64_t lo_hi = a_lo * b_hi;
+    const std::uint64_t hi_hi = a_hi * b_hi;
+    const std::uint64_t cross = (lo_lo >> 32u) + (hi_lo & 0xFFFFFFFFu) + lo_hi;
+    return {(cross << 32u) | (lo_lo & 0xFFFFFFFFu), (hi_lo >> 32u) + (cross >> 32u) + hi_hi};
+#endif
+}
+
+/// eight bytes as a little-endian word (compilers fold this into one load on
+/// little-endian targets)
+inline std::uint64_t read_eight_bytes(const char* p) noexcept
+{
+    const auto* b = reinterpret_cast<const unsigned char*>(p); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    return static_cast<std::uint64_t>(b[0]) | (static_cast<std::uint64_t>(b[1]) << 8u)
+           | (static_cast<std::uint64_t>(b[2]) << 16u) | (static_cast<std::uint64_t>(b[3]) << 24u)
+           | (static_cast<std::uint64_t>(b[4]) << 32u) | (static_cast<std::uint64_t>(b[5]) << 40u)
+           | (static_cast<std::uint64_t>(b[6]) << 48u) | (static_cast<std::uint64_t>(b[7]) << 56u);
+}
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/conversions/from_json.hpp

@@ -167,9 +167,13 @@ template<typename BasicJsonType, typename EnumType,
          enable_if_t<std::is_enum<EnumType>::value, int> = 0>
 inline void from_json(const BasicJsonType& j, EnumType& e)
 {
-    typename std::underlying_type<EnumType>::type val;
+    using underlying_type = typename std::underlying_type<EnumType>::type;
+    // get_arithmetic_value() does not accept boolean_t; read the number that to_json() wrote instead
+    using value_type = typename std::conditional<std::is_same<underlying_type, typename BasicJsonType::boolean_t>::value,
+          typename BasicJsonType::number_unsigned_t, underlying_type>::type;
+    value_type val;
     get_arithmetic_value(j, val);
-    e = static_cast<EnumType>(val);
+    e = static_cast<EnumType>(static_cast<underlying_type>(val));
 }
 #endif  // JSON_DISABLE_ENUM_SERIALIZATION
 
@@ -564,7 +568,7 @@ inline void from_json(const BasicJsonType& j, std::map<Key, Value, Compare, Allo
     {
         if (JSON_HEDLEY_UNLIKELY(!p.is_array()))
         {
-            JSON_THROW(type_error::create(302, concat("type must be array, but is ", p.type_name()), &j));
+            JSON_THROW(type_error::create(302, concat("type must be array, but is ", p.type_name()), &p));
         }
         m.emplace(p.at(0).template get<Key>(), p.at(1).template get<Value>());
     }
@@ -584,7 +588,7 @@ inline void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Has
     {
         if (JSON_HEDLEY_UNLIKELY(!p.is_array()))
         {
-            JSON_THROW(type_error::create(302, concat("type must be array, but is ", p.type_name()), &j));
+            JSON_THROW(type_error::create(302, concat("type must be array, but is ", p.type_name()), &p));
         }
         m.emplace(p.at(0).template get<Key>(), p.at(1).template get<Value>());
     }

include/nlohmann/detail/conversions/to_json.hpp

@@ -287,7 +287,7 @@ struct external_constructor<value_t::object>
 #ifdef JSON_HAS_CPP_17
 template<typename BasicJsonType, typename T,
          enable_if_t<std::is_constructible<BasicJsonType, T>::value, int> = 0>
-void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept
+void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept(std::is_nothrow_assignable<BasicJsonType&, const T&>::value)
 {
     if (opt.has_value())
     {

include/nlohmann/detail/input/binary_reader.hpp

@@ -1324,6 +1324,80 @@ class binary_reader
         }
     }
 
+    /*!
+    @brief reads a CBOR object key
+
+    RFC 8949 allows any data item as a map key, but only strings have a
+    counterpart in JSON. A key of any other type is rejected with a message
+    naming that type, rather than the one @ref get_cbor_string gives for a
+    malformed string.
+
+    @param[out] result  created key
+
+    @return whether key creation completed
+    */
+    bool get_cbor_object_key(string_t& result)
+    {
+        // EOF and major type 3 (text string) are left to get_cbor_string
+        if (current == char_traits<char_type>::eof() || (static_cast<unsigned int>(current) & 0xE0u) == 0x60u)
+        {
+            return get_cbor_string(result);
+        }
+
+        const char* found = nullptr;
+        switch (static_cast<unsigned int>(current) >> 5u)
+        {
+            case 0:
+                found = "an unsigned integer";
+                break;
+            case 1:
+                found = "a negative integer";
+                break;
+            case 2:
+                found = "a byte string";
+                break;
+            case 4:
+                found = "an array";
+                break;
+            case 5:
+                found = "a map";
+                break;
+            case 6:
+                found = "a tag";
+                break;
+            default: // major type 7
+                switch (current)
+                {
+                    case 0xF4:
+                    case 0xF5:
+                        found = "a boolean";
+                        break;
+                    case 0xF6:
+                        found = "null";
+                        break;
+                    case 0xF7:
+                        found = "undefined";
+                        break;
+                    case 0xF9:
+                    case 0xFA:
+                    case 0xFB:
+                        found = "a floating-point number";
+                        break;
+                    case 0xFF:
+                        found = "a break stop code";
+                        break;
+                    default:
+                        found = "a simple value";
+                        break;
+                }
+                break;
+        }
+
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                exception_message(input_format_t::cbor, concat("only string keys are supported, but found ", found, "; last byte: 0x", last_token), "object key"), nullptr));
+    }
+
     /*!
     @brief reads a definite-length CBOR byte array
 
@@ -1568,7 +1642,7 @@ class binary_reader
                 if (top.is_object)
                 {
                     key.clear();
-                    if (JSON_HEDLEY_UNLIKELY(!get_cbor_string(key) || !sax->key(key)))
+                    if (JSON_HEDLEY_UNLIKELY(!get_cbor_object_key(key) || !sax->key(key)))
                     {
                         return false;
                     }
@@ -2069,6 +2143,98 @@ class binary_reader
         }
     }
 
+    /*!
+    @brief reads a MessagePack object key
+
+    The MessagePack specification allows any type as a map key, but only
+    strings have a counterpart in JSON. A key of any other type is rejected
+    with a message naming that type, rather than the one @ref
+    get_msgpack_string gives for a malformed string.
+
+    @param[out] result  created key
+
+    @return whether key creation completed
+    */
+    bool get_msgpack_object_key(string_t& result)
+    {
+        const char* found = nullptr;
+        switch (current)
+        {
+            case 0xC0:
+                found = "nil";
+                break;
+            case 0xC2:
+            case 0xC3:
+                found = "a boolean";
+                break;
+            case 0xCA:
+            case 0xCB:
+                found = "a float";
+                break;
+            case 0xC4:
+            case 0xC5:
+            case 0xC6:
+                found = "a bin";
+                break;
+            case 0xC7:
+            case 0xC8:
+            case 0xC9:
+            case 0xD4:
+            case 0xD5:
+            case 0xD6:
+            case 0xD7:
+            case 0xD8:
+                found = "an ext";
+                break;
+            case 0xCC:
+            case 0xCD:
+            case 0xCE:
+            case 0xCF:
+            case 0xD0:
+            case 0xD1:
+            case 0xD2:
+            case 0xD3:
+                found = "an integer";
+                break;
+            case 0xDC:
+            case 0xDD:
+                found = "an array";
+                break;
+            case 0xDE:
+            case 0xDF:
+                found = "a map";
+                break;
+            default:
+                // fixint, fixmap, and fixarray; strings, EOF, and the unused
+                // byte 0xC1 are left to get_msgpack_string
+                if (current == char_traits<char_type>::eof())
+                {
+                    return get_msgpack_string(result);
+                }
+                if (current <= 0x7F || current >= 0xE0)
+                {
+                    found = "an integer";
+                }
+                else if (current <= 0x8F)
+                {
+                    found = "a map";
+                }
+                else if (current <= 0x9F)
+                {
+                    found = "an array";
+                }
+                else
+                {
+                    return get_msgpack_string(result);
+                }
+                break;
+        }
+
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                exception_message(input_format_t::msgpack, concat("only string keys are supported, but found ", found, "; last byte: 0x", last_token), "object key"), nullptr));
+    }
+
     /*!
     @brief reads a MessagePack byte array
 
@@ -2231,7 +2397,7 @@ class binary_reader
                 {
                     get();
                     key.clear();
-                    if (JSON_HEDLEY_UNLIKELY(!get_msgpack_string(key) || !sax->key(key)))
+                    if (JSON_HEDLEY_UNLIKELY(!get_msgpack_object_key(key) || !sax->key(key)))
                     {
                         return false;
                     }

include/nlohmann/detail/input/input_adapters.hpp

@@ -106,7 +106,13 @@ class input_stream_adapter
             // was given back with release_lookahead()
             commit_lookahead();
 #endif
-            is->clear(is->rdstate() & std::ios::eofbit);
+            // only call clear() if there is something to clear: it throws
+            // std::ios_base::failure if the stream has exceptions() enabled
+            // for a state bit that remains set, and a destructor must not throw
+            if ((is->rdstate() & ~std::ios::eofbit) != 0)
+            {
+                is->clear(is->rdstate() & std::ios::eofbit);
+            }
         }
     }
 
@@ -811,12 +817,16 @@ inline file_input_adapter input_adapter(std::FILE* file)
 
 inline input_stream_adapter input_adapter(std::istream& stream)
 {
+    if (stream.rdbuf() == nullptr)
+    {
+        JSON_THROW(parse_error::create(101, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
+    }
     return input_stream_adapter(stream);
 }
 
 inline input_stream_adapter input_adapter(std::istream&& stream)
 {
-    return input_stream_adapter(stream);
+    return input_adapter(stream);
 }
 #endif  // JSON_NO_IO
 
@@ -845,16 +855,28 @@ template<typename T, std::size_t N>
 auto input_adapter(T (&array)[N]) -> decltype(input_adapter(array, array + N)) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
 {
 #if JSON_STRICT_NUL_HANDLING
-    // A `char` array from string-literal initialization (e.g. json::parse("123"))
-    // carries a trailing '\0' contributed by the compiler, not by the source
-    // text; drop exactly that one byte so it is not mistaken for real trailing
-    // data. Every other element type (unsigned char, std::uint8_t, ...) keeps
-    // the full extent unconditionally, since a trailing zero byte there is
-    // genuine data (e.g. CBOR/MessagePack). This intentionally does not
-    // strlen()-scan the array (as the pointer overload above does for a
-    // null-delimited string): for a `char` array that is not NUL-terminated
-    // within its bounds, that would read past the end of the array.
-    if (std::is_same<typename std::remove_cv<T>::type, char>::value && N > 0 && array[N - 1] == 0)
+    // A text-literal array from string-literal initialization (e.g.
+    // json::parse("123") or json::parse(L"123")) carries a trailing '\0'
+    // contributed by the compiler, not by the source text; drop exactly that
+    // one byte so it is not mistaken for real trailing data. This covers all
+    // character types that string literals can use: char, wchar_t, char16_t,
+    // char32_t, and (C++20) char8_t. Every other element type (unsigned char,
+    // std::uint8_t, ...) keeps the full extent unconditionally, since a
+    // trailing zero byte there is genuine data (e.g. CBOR/MessagePack). This
+    // intentionally does not strlen()-scan the array (as the pointer overload
+    // above does for a null-delimited string): for an array that is not
+    // NUL-terminated within its bounds, that would read past the end of the
+    // array.
+    using char_t = typename std::remove_cv<T>::type;
+    constexpr bool is_text_literal_type = std::is_same<char_t, char>::value
+                                          || std::is_same<char_t, wchar_t>::value
+                                          || std::is_same<char_t, char16_t>::value
+                                          || std::is_same<char_t, char32_t>::value
+#if defined(__cpp_char8_t)
+                                          || std::is_same<char_t, char8_t>::value
+#endif
+                                          ;
+    if (is_text_literal_type && N > 0 && array[N - 1] == 0)
     {
         return input_adapter(array, array + N - 1);
     }

include/nlohmann/detail/input/json_sax.hpp

@@ -582,8 +582,8 @@ class json_sax_dom_callback_parser
 
     bool start_object(std::size_t len)
     {
-        // check callback for object start
-        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
+        // check callback for object start; not called inside a discarded container
+        const bool keep = keep_stack.back() && callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
         keep_stack.push_back(keep);
 
         // the key this object will be stored under, read before handle_value()
@@ -619,6 +619,18 @@ class json_sax_dom_callback_parser
 
     bool key(string_t& val)
     {
+        if (!keep_stack.back() || !ref_stack.back())
+        {
+            // the object is not stored: the value of this key is dropped in
+            // handle_value() without touching the key stacks
+            if (keep_stack.back())
+            {
+                BasicJsonType k = BasicJsonType(val);
+                static_cast<void>(callback(static_cast<int>(ref_stack.size()), parse_event_t::key, k));
+            }
+            return true;
+        }
+
         BasicJsonType k = BasicJsonType(val);
 
         // check callback for the key
@@ -704,7 +716,7 @@ class json_sax_dom_callback_parser
 
     bool start_array(std::size_t len)
     {
-        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
+        const bool keep = keep_stack.back() && callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
 
         // see start_object()

include/nlohmann/detail/input/lexer.hpp

@@ -9,10 +9,8 @@
 #pragma once
 
 #include <array> // array
-#include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdio> // snprintf
-#include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
 #include <initializer_list> // initializer_list
 #include <string> // char_traits, string
 #include <utility> // move
@@ -206,7 +204,6 @@ class lexer : public lexer_base<BasicJsonType>
     explicit lexer(InputAdapterType&& adapter, bool ignore_comments_ = false, bool discard_number_values_ = false) noexcept
         : ia(std::move(adapter))
         , ignore_comments(ignore_comments_)
-        , decimal_point_char(static_cast<char_int_type>(get_decimal_point()))
         , discard_number_values(discard_number_values_)
     {}
 
@@ -218,19 +215,6 @@ class lexer : public lexer_base<BasicJsonType>
     ~lexer() = default;
 
   private:
-    /////////////////////
-    // locales
-    /////////////////////
-
-    /// return the locale-dependent decimal point
-    JSON_HEDLEY_PURE
-    static char get_decimal_point() noexcept
-    {
-        const auto* loc = localeconv();
-        JSON_ASSERT(loc != nullptr);
-        return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point);
-    }
-
     /////////////////////
     // scan functions
     /////////////////////
@@ -1038,24 +1022,6 @@ class lexer : public lexer_base<BasicJsonType>
         }
     }
 
-    JSON_HEDLEY_NON_NULL(2)
-    static void strtof(float& f, const char* str, char** endptr) noexcept
-    {
-        f = std::strtof(str, endptr);
-    }
-
-    JSON_HEDLEY_NON_NULL(2)
-    static void strtof(double& f, const char* str, char** endptr) noexcept
-    {
-        f = std::strtod(str, endptr);
-    }
-
-    JSON_HEDLEY_NON_NULL(2)
-    static void strtof(long double& f, const char* str, char** endptr) noexcept
-    {
-        f = std::strtold(str, endptr);
-    }
-
     /*!
     @brief scan a number literal
 
@@ -1092,9 +1058,10 @@ class lexer : public lexer_base<BasicJsonType>
             token_type::value_float if number could be successfully scanned,
             token_type::parse_error otherwise
 
-    @note The scanner is independent of the current locale. Internally, the
-          locale's decimal point is used instead of `.` to work with the
-          locale-dependent converters.
+    @note The scanner is independent of the current locale: token_buffer
+          always holds `.`. Only the std::strtod fallback of convert_number()
+          depends on the locale, and it looks up the decimal point right
+          before converting (see detail::convert_float_locale_aware()).
     */
     token_type scan_number()  // lgtm [cpp/use-of-goto] `goto` is used in this function to implement the number-parsing state machine described above. By design, any finite input will eventually reach the "done" state or return token_type::parse_error. In each intermediate state, 1 byte of the input is appended to the token_buffer vector, and only the already initialized variables token_buffer, number_type, and error_message are manipulated.
     {
@@ -1183,7 +1150,7 @@ scan_number_zero:
         {
             case '.':
             {
-                add(decimal_point_char);
+                add(current);
                 decimal_point_position = token_buffer.size() - 1;
                 goto scan_number_decimal1;
             }
@@ -1220,7 +1187,7 @@ scan_number_any1:
 
             case '.':
             {
-                add(decimal_point_char);
+                add(current);
                 decimal_point_position = token_buffer.size() - 1;
                 goto scan_number_decimal1;
             }
@@ -1425,65 +1392,12 @@ scan_number_done:
         return token_type::uninitialized;
     }
 
-    /*!
-    @brief check whether Clinger's fast path can still succeed for this token
-
-    parse_float_fast() needs a significand below 2^53. A mantissa with 17 or
-    more significant digits is at least 10^16 and therefore always exceeds it,
-    so calling the fast path would walk the token one extra time only to
-    decline before strtod has to run anyway.
-
-    Significant digits are the mantissa's digits from the first nonzero one on;
-    the sign, the decimal point, leading zeros, and the exponent do not count.
-    The answer is derived from indices - the digits are not scanned again - so
-    this stays off the hot path of the number scanners.
-
-    @param[in] mantissa_end  offset just past the last mantissa byte in
-                             token_buffer
-    @return false if parse_float_fast() is guaranteed to decline
-    */
-    bool mantissa_fits_clinger(std::size_t mantissa_end) const
-    {
-        // 10^16 already exceeds 2^53, so 17 digits can never fit
-        constexpr std::size_t limit = 17;
-
-        const std::size_t neg = (!token_buffer.empty() && token_buffer[0] == '-') ? 1u : 0u;
-        const std::size_t has_dot = (decimal_point_position != std::string::npos) ? 1u : 0u;
-        // the JSON grammar restricts the integer part to "0" or [1-9][0-9]*, so
-        // a leading zero can only be a lone "0", which is not significant
-        const std::size_t lead_zero = (token_buffer[neg] == '0') ? 1u : 0u;
-        JSON_ASSERT(mantissa_end >= neg + has_dot + lead_zero);
-        std::size_t digits = mantissa_end - neg - has_dot - lead_zero;
-
-        if (JSON_HEDLEY_LIKELY(digits < limit))
-        {
-            return true;
-        }
-
-        // Only a number below 1 can carry further insignificant zeros, and only
-        // while the count stays at the limit does removing them change the
-        // answer - so this loop is skipped for all but a few tokens. Note
-        // token_buffer holds the locale's decimal point, so the fraction is
-        // located through decimal_point_position rather than by searching '.'.
-        if (lead_zero != 0)
-        {
-            JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
-            for (std::size_t i = decimal_point_position + 1;
-                    digits >= limit && i < mantissa_end && token_buffer[i] == '0'; ++i)
-            {
-                --digits;
-            }
-        }
-
-        return digits < limit;
-    }
-
     /*!
     @brief convert the number text in token_buffer to its value and token type
 
     The digit sequence in token_buffer has already been validated (by the
-    scan_number() state machine or by the contiguous fast path) and holds the
-    locale decimal point in place of '.'. Integers are parsed first and fall
+    scan_number() state machine or by the contiguous fast path) and holds '.'
+    as decimal point, independent of the locale. Integers are parsed first and fall
     back to floating point on overflow. This is shared so both scanners produce
     identical results.
 
@@ -1491,7 +1405,7 @@ scan_number_done:
                              token_buffer (the index of 'e'/'E', or
                              token_buffer.size() when there is no exponent);
                              used to skip Clinger's fast path when it cannot
-                             possibly succeed - see mantissa_fits_clinger()
+                             possibly succeed - see detail::mantissa_fits_clinger()
     */
     token_type convert_number(token_type number_type, std::size_t mantissa_end)
     {
@@ -1563,26 +1477,13 @@ scan_number_done:
         // integer conversion above overflowed. Prefer std::from_chars
         // (Eisel-Lemire, locale-independent, correctly rounded) when available;
         // otherwise the exact Clinger fast path (double only); otherwise the
-        // locale-aware strtof/strtod.
-        if (parse_float_from_chars(num_begin, num_end, value_float))
-        {
-            return token_type::value_float;
-        }
-        // Skipping a fast path that cannot succeed is lossless and saves a full
-        // extra pass over the token's bytes, which otherwise shows up on
-        // high-precision inputs such as canada.json
-        if (mantissa_fits_clinger(mantissa_end)
-                && parse_float_fast(num_begin, num_end, decimal_point_char, value_float))
+        // locale-aware strtof/strtod/strtold.
+        if (convert_float_fast(num_begin, num_end, decimal_point_position, mantissa_end, value_float))
         {
             return token_type::value_float;
         }
 
-        char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
-        strtof(value_float, token_buffer.data(), &endptr);
-
-        // we checked the number format before
-        JSON_ASSERT(endptr == token_buffer.data() + token_buffer.size());
-
+        convert_float_locale_aware(token_buffer, decimal_point_position, value_float);
         return token_type::value_float;
     }
 
@@ -1591,7 +1492,7 @@ scan_number_done:
 
     Parses the whole number token straight from the input buffer, avoiding the
     per-character get()/add() of scan_number(). On success it fills token_buffer
-    (with the locale decimal point substituted, as scan_number() does) and
+    (as scan_number() does) and
     returns the token type. On anything it does not fully recognize as a
     well-formed number it makes no state change and returns
     token_type::uninitialized, so the caller falls back to scan_number(), which
@@ -1707,16 +1608,11 @@ scan_number_done:
         }
 #endif
 
-        // materialize the token exactly as scan_number() would, substituting the
-        // locale decimal point so convert_number()'s strtof fallback stays valid.
-        // reset() already cleared token_buffer, so append() fills it (assign() is
-        // avoided because custom string_t types need not provide it)
+        // materialize the token exactly as scan_number() would. reset() already
+        // cleared token_buffer, so append() fills it (assign() is avoided
+        // because custom string_t types need not provide it)
         token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), len);
-        if (dot_index != std::string::npos)
-        {
-            token_buffer[dot_index] = static_cast<typename string_t::value_type>(decimal_point_char);
-            decimal_point_position = dot_index;
-        }
+        decimal_point_position = dot_index;
 
         ia.bulk_skip(len - 1);
         position.chars_read_total += (len - 1);
@@ -1983,11 +1879,7 @@ scan_number_done:
     /// return current string value (implicitly resets the token; useful only once)
     string_t& get_string()
     {
-        // translate decimal points from locale back to '.' (#4084)
-        if (decimal_point_char != '.' && decimal_point_position != std::string::npos)
-        {
-            token_buffer[decimal_point_position] = '.';
-        }
+        // a number token holds '.' regardless of the locale (#4084)
         return token_buffer;
     }
 
@@ -2283,9 +2175,7 @@ scan_number_done:
     number_unsigned_t value_unsigned = 0;
     number_float_t value_float = 0;
 
-    /// the decimal point
-    const char_int_type decimal_point_char = '.';
-    /// the position of the decimal point in the input
+    /// the position of the decimal point in token_buffer
     std::size_t decimal_point_position = std::string::npos;
 
     /// whether the caller (e.g. accept()/json_sax_acceptor) only needs the

include/nlohmann/detail/input/number_parse.hpp

@@ -3,6 +3,7 @@
 // |  |  |__   |  |  | | | |  version 3.12.0
 // |_____|_____|_____|_|___|  https://github.com/nlohmann/json
 //
+// SPDX-FileCopyrightText: 2021 The fast_float authors <https://github.com/fastfloat/fast_float>
 // SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
 // SPDX-License-Identifier: MIT
 
@@ -10,10 +11,16 @@
 
 #include <array> // array
 #include <cfloat> // FLT_EVAL_METHOD
+#include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdint> // int64_t, uint64_t
+#include <cstdlib> // strtof, strtod, strtold
+#include <cstring> // memcpy
 #include <limits> // numeric_limits
+#include <string> // string
 
+#include <nlohmann/detail/bit_ops.hpp>
+#include <nlohmann/detail/input/pow5_table.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 
 // std::from_chars lives in <charconv>, but being in C++17 mode does not
@@ -29,8 +36,9 @@
 
 // This file contains the value-conversion helpers used by the lexer to turn an
 // already-validated number token into a value, without the locale/errno
-// overhead of std::strtoull/std::strtod. They are free functions so the lexer
-// stays focused on scanning; see lexer::convert_number().
+// overhead of std::strtoull/std::strtod where possible. They are free functions
+// so the lexer stays focused on scanning (see lexer::convert_number()) and so
+// that other parsers of JSON text can convert tokens exactly like it does.
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -118,14 +126,12 @@ std::strtod. The parser only activates for number_float_t == double; float and
 long double keep the std::strtof/std::strtold paths (see the templated overload
 below).
 
-@param[in]  first          pointer to the first character of the number
-@param[in]  last           pointer past the last character
-@param[in]  decimal_point  the (locale-dependent) decimal point character
-@param[out] out            the parsed value on success
+@param[in]  first  pointer to the first character of the number
+@param[in]  last   pointer past the last character
+@param[out] out    the parsed value on success
 @return true if the value was parsed exactly; false to fall back to strtod
 */
-template<typename DecimalPointType>
-bool parse_float_fast(const char* first, const char* last, DecimalPointType decimal_point, double& out) noexcept
+inline bool parse_float_fast(const char* first, const char* last, double& out) noexcept
 {
 #if defined(FLT_EVAL_METHOD) && FLT_EVAL_METHOD != 0
     // Clinger's fast path is only exact when double operations are evaluated in
@@ -136,7 +142,6 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
     // std::from_chars / std::strtod path.
     static_cast<void>(first);
     static_cast<void>(last);
-    static_cast<void>(decimal_point);
     static_cast<void>(out);
     return false;
 #else
@@ -175,7 +180,7 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
             ++num_digits;
             fractional_digits += static_cast<int>(seen_dot);
         }
-        else if (static_cast<DecimalPointType>(c) == decimal_point)
+        else if (c == '.')
         {
             if (JSON_HEDLEY_UNLIKELY(seen_dot))
             {
@@ -260,8 +265,8 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
 }
 
 /// fast float path is only exact for `double`; decline for float/long double
-template<typename DecimalPointType, typename FloatType>
-bool parse_float_fast(const char* /*first*/, const char* /*last*/, DecimalPointType /*decimal_point*/, FloatType& /*out*/) noexcept
+template<typename FloatType>
+bool parse_float_fast(const char* /*first*/, const char* /*last*/, FloatType& /*out*/) noexcept
 {
     return false;
 }
@@ -273,9 +278,7 @@ std::from_chars is locale-independent, correctly rounded, and - via the
 Eisel-Lemire algorithm in modern standard libraries - much faster than strtod
 over the whole value range (not just the Clinger subset). It is used only when
 __cpp_lib_to_chars indicates full floating-point support and only when it
-consumes the entire token ([first, last)); a partial parse means the buffer
-uses a non-'.' locale decimal point, in which case the caller falls back to the
-locale-aware path. An under-/overflow (result_out_of_range) also declines, so
+consumes the entire token ([first, last)). An under-/overflow (result_out_of_range) also declines, so
 the caller's strtod fallback supplies the well-defined ±inf/0 result the parser
 expects (side-stepping the P4168 divergence between implementations).
 
@@ -298,5 +301,415 @@ bool parse_float_from_chars(const char* first, const char* last, FloatType& out)
 #endif
 }
 
+/// whether the eight bytes of @a v (see read_eight_bytes()) are ASCII digits
+/// (after fast_float's is_made_of_eight_digits_fast)
+inline bool is_eight_digits(std::uint64_t v) noexcept
+{
+    return ((v & 0xF0F0F0F0F0F0F0F0u) | (((v + 0x0606060606060606u) & 0xF0F0F0F0F0F0F0F0u) >> 4u)) == 0x3333333333333333u;
+}
+
+/// the value of the eight ASCII digits in @a v (see read_eight_bytes()), three
+/// multiplications instead of eight (after simdjson and fast_float)
+inline std::uint32_t parse_eight_digits(std::uint64_t v) noexcept
+{
+    v = ((v & 0x0F0F0F0F0F0F0F0Fu) * 2561u) >> 8u;
+    v = ((v & 0x00FF00FF00FF00FFu) * 6553601u) >> 16u;
+    return static_cast<std::uint32_t>(((v & 0x0000FFFF0000FFFFu) * 42949672960001u) >> 32u);
+}
+
+/*!
+@brief the double nearest to w * 10^q (Eisel-Lemire)
+
+The algorithm of Daniel Lemire, "Number Parsing at a Gigabyte per Second"
+(Software: Practice and Experience, 2021), after fast_float's compute_float
+(used under the MIT license). With a 128-bit approximation of 5^q, the product
+is always sufficient to round correctly for w with at most 19 digits (Noble
+Mushtak and Daniel Lemire, "Fast number parsing without fallback", Software:
+Practice and Experience, 2023). Only integer arithmetic is used, so the result
+does not depend on the floating-point environment.
+
+@param[in] q  decimal exponent
+@param[in] w  significand, w != 0
+@return the IEEE-754 bits of the positive result (0 for underflow, infinity
+        for overflow)
+*/
+inline std::uint64_t eisel_lemire(std::int64_t q, std::uint64_t w) noexcept
+{
+    constexpr int mantissa_bits = 52;
+    constexpr std::uint64_t infinity = std::uint64_t{0x7FF} << mantissa_bits;
+    if (q < pow5_128_smallest_power)
+    {
+        return 0;
+    }
+    if (q > pow5_128_largest_power)
+    {
+        return infinity;
+    }
+
+    const int lz = count_leading_zeros(w);
+    w <<= static_cast<unsigned>(lz);
+    const auto index = static_cast<std::size_t>(2 * (q - pow5_128_smallest_power));
+    uint128_parts product = full_multiplication(w, pow5_128()[index]);
+    constexpr std::uint64_t precision_mask = 0xFFFFFFFFFFFFFFFFu >> (mantissa_bits + 3);
+    if ((product.high & precision_mask) == precision_mask)
+    {
+        // the lower bits may carry into the result: use the next 64 bits of 5^q
+        const uint128_parts second = full_multiplication(w, pow5_128()[index + 1]);
+        product.low += second.high;
+        if (second.high > product.low)
+        {
+            ++product.high;
+        }
+    }
+
+    const auto upperbit = static_cast<int>(product.high >> 63u);
+    const int shift = upperbit + 64 - mantissa_bits - 3;
+    std::uint64_t mantissa = product.high >> static_cast<unsigned>(shift);
+    // floor(log2(10^q)) + 63 + 1023, with log2(10) ~ 217706 / 2^16
+    std::int64_t power2 = (((152170 + 65536) * q) >> 16) + 63 + upperbit - lz + 1023;
+
+    if (power2 <= 0) // subnormal
+    {
+        if (-power2 + 1 >= 64)
+        {
+            return 0;
+        }
+        mantissa >>= static_cast<unsigned>(-power2 + 1);
+        mantissa += (mantissa & 1u);
+        mantissa >>= 1u;
+        // rounding up may produce the smallest normal number
+        power2 = (mantissa < (std::uint64_t{1} << mantissa_bits)) ? 0 : 1;
+        return mantissa | (static_cast<std::uint64_t>(power2) << mantissa_bits);
+    }
+
+    // a value exactly between two doubles rounds to even; this can only
+    // happen for small |q|, where 5^q is exact
+    if (product.low <= 1 && q >= -4 && q <= 23 && (mantissa & 3u) == 1
+            && (mantissa << static_cast<unsigned>(shift)) == product.high)
+    {
+        mantissa &= ~std::uint64_t{1};
+    }
+    mantissa += (mantissa & 1u);
+    mantissa >>= 1u;
+    if (mantissa >= (std::uint64_t{2} << mantissa_bits))
+    {
+        mantissa = std::uint64_t{1} << mantissa_bits;
+        ++power2;
+    }
+    mantissa &= ~(std::uint64_t{1} << mantissa_bits);
+    if (power2 >= 0x7FF)
+    {
+        return infinity;
+    }
+    return mantissa | (static_cast<std::uint64_t>(power2) << mantissa_bits);
+}
+
+/*!
+@brief parse a validated float token with the Eisel-Lemire algorithm
+
+The significand is accumulated eight digits at a time where possible. A token
+with more than 19 significant digits is truncated to w; the value then lies
+in [w, w + 1) * 10^q, and it is only returned if both ends round to the same
+double, which covers all but a few such tokens.
+
+@param[in]  first  pointer to the first character of the token
+@param[in]  last   pointer past the last character
+@param[out] out    the correctly rounded value on success (±infinity if it
+                   overflows, like strtod)
+@return true on success; false if strtod must decide
+*/
+inline bool parse_float_eisel_lemire(const char* first, const char* last, double& out) noexcept
+{
+    const char* p = first;
+    const bool negative = (p != last && *p == '-');
+    if (negative)
+    {
+        ++p;
+    }
+
+    std::uint64_t w = 0;
+    int digits = 0; // significant digits in w
+    std::int64_t exponent = 0;
+    bool truncated = false;
+    bool in_fraction = false;
+    for (;;)
+    {
+        // eight digits at a time, as long as they fit into w
+        while (w != 0 && digits <= 19 - 8 && last - p >= 8)
+        {
+            const std::uint64_t v = read_eight_bytes(p);
+            if (!is_eight_digits(v))
+            {
+                break;
+            }
+            w = (w * 100000000u) + parse_eight_digits(v);
+            digits += 8;
+            exponent -= in_fraction ? 8 : 0;
+            p += 8;
+        }
+        if (p == last)
+        {
+            break;
+        }
+        const char c = *p;
+        if (c >= '0' && c <= '9')
+        {
+            if (w == 0 && c == '0')
+            {
+                // leading zeros are not significant, but scale a fraction
+                exponent -= in_fraction ? 1 : 0;
+            }
+            else if (digits < 19)
+            {
+                w = (w * 10u) + static_cast<std::uint64_t>(c - '0');
+                ++digits;
+                exponent -= in_fraction ? 1 : 0;
+            }
+            else
+            {
+                // dropped: the value lies between w and w + 1 (in units of
+                // the last kept digit) unless all dropped digits are zero
+                truncated = truncated || c != '0';
+                exponent += in_fraction ? 0 : 1;
+            }
+            ++p;
+        }
+        else if (c == '.')
+        {
+            in_fraction = true;
+            ++p;
+        }
+        else
+        {
+            break; // 'e' or 'E'
+        }
+    }
+
+    if (p != last)
+    {
+        ++p; // 'e' or 'E'
+        bool exp_negative = false;
+        if (p != last && (*p == '-' || *p == '+'))
+        {
+            exp_negative = (*p == '-');
+            ++p;
+        }
+        std::int64_t exp_value = 0;
+        for (; p != last; ++p)
+        {
+            // saturate: any exponent beyond this under- or overflows anyway
+            if (exp_value < 100000)
+            {
+                exp_value = (exp_value * 10) + (*p - '0');
+            }
+        }
+        exponent += exp_negative ? -exp_value : exp_value;
+    }
+
+    std::uint64_t bits = 0;
+    if (w != 0)
+    {
+        bits = eisel_lemire(exponent, w);
+        if (truncated && (w + 1 == 0 || eisel_lemire(exponent, w + 1) != bits))
+        {
+            return false;
+        }
+    }
+    bits |= negative ? (std::uint64_t{1} << 63u) : 0u;
+    static_assert(sizeof(double) == sizeof(std::uint64_t), "double must have 64 bits");
+    std::memcpy(&out, &bits, sizeof(out));
+    return true;
+}
+
+/// Eisel-Lemire is only implemented for `double`
+template<typename FloatType>
+bool parse_float_eisel_lemire(const char* /*first*/, const char* /*last*/, FloatType& /*out*/) noexcept
+{
+    return false;
+}
+
+/*!
+@brief check whether Clinger's fast path can still succeed for a float token
+
+parse_float_fast() needs a significand below 2^53. A mantissa with 17 or
+more significant digits is at least 10^16 and therefore always exceeds it,
+so calling the fast path would walk the token one extra time only to
+decline before strtod has to run anyway.
+
+Significant digits are the mantissa's digits from the first nonzero one on;
+the sign, the decimal point, leading zeros, and the exponent do not count.
+The answer is derived from indices - the digits are not scanned again - so
+this stays off the hot path of the number scanners.
+
+@param[in] token                   the validated number token ('.' as decimal point)
+@param[in] decimal_point_position  index of the '.' in @a token, or
+                                   std::string::npos if there is none
+@param[in] mantissa_end            offset just past the last mantissa byte
+@return false if parse_float_fast() is guaranteed to decline
+*/
+inline bool mantissa_fits_clinger(const char* token, std::size_t decimal_point_position, std::size_t mantissa_end) noexcept
+{
+    // 10^16 already exceeds 2^53, so 17 digits can never fit
+    constexpr std::size_t limit = 17;
+
+    const std::size_t neg = (token[0] == '-') ? 1u : 0u;
+    const std::size_t has_dot = (decimal_point_position != std::string::npos) ? 1u : 0u;
+    // the JSON grammar restricts the integer part to "0" or [1-9][0-9]*, so
+    // a leading zero can only be a lone "0", which is not significant
+    const std::size_t lead_zero = (token[neg] == '0') ? 1u : 0u;
+    JSON_ASSERT(mantissa_end >= neg + has_dot + lead_zero);
+    std::size_t digits = mantissa_end - neg - has_dot - lead_zero;
+
+    if (JSON_HEDLEY_LIKELY(digits < limit))
+    {
+        return true;
+    }
+
+    // Only a number below 1 can carry further insignificant zeros, and only
+    // while the count stays at the limit does removing them change the
+    // answer - so this loop is skipped for all but a few tokens. The
+    // fraction is located through decimal_point_position rather than by
+    // searching '.'.
+    if (lead_zero != 0)
+    {
+        JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
+        for (std::size_t i = decimal_point_position + 1;
+                digits >= limit && i < mantissa_end && token[i] == '0'; ++i)
+        {
+            --digits;
+        }
+    }
+
+    return digits < limit;
+}
+
+/*!
+@brief convert a validated float token without the C library, if possible
+
+Tries std::from_chars (when available), Clinger's exact fast path (double
+only, skipped when it cannot succeed), and the Eisel-Lemire algorithm (double
+only).
+
+@param[in]  first                   pointer to the first character of the token
+@param[in]  last                    pointer past the last character
+@param[in]  decimal_point_position  index of the '.' in the token, or
+                                    std::string::npos if there is none
+@param[in]  mantissa_end            offset just past the last mantissa byte (the
+                                    index of 'e'/'E', or the token length)
+@param[out] value                   the converted value on success
+@return true if the value was converted; false if convert_float_locale_aware()
+        must convert it
+*/
+template<typename FloatType>
+bool convert_float_fast(const char* first, const char* last, std::size_t decimal_point_position,
+                        std::size_t mantissa_end, FloatType& value) noexcept
+{
+    if (parse_float_from_chars(first, last, value))
+    {
+        return true;
+    }
+    // Skipping a fast path that cannot succeed is lossless and saves a full
+    // extra pass over the token's bytes, which otherwise shows up on
+    // high-precision inputs such as canada.json
+    if (mantissa_fits_clinger(first, decimal_point_position, mantissa_end)
+            && parse_float_fast(first, last, value))
+    {
+        return true;
+    }
+    return parse_float_eisel_lemire(first, last, value);
+}
+
+/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
+JSON_HEDLEY_NON_NULL(2)
+inline void strtof_by_type(float& f, const char* str, char** endptr) noexcept
+{
+    f = std::strtof(str, endptr);
+}
+
+/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
+JSON_HEDLEY_NON_NULL(2)
+inline void strtof_by_type(double& f, const char* str, char** endptr) noexcept
+{
+    f = std::strtod(str, endptr);
+}
+
+/// std::strtof, std::strtod, or std::strtold, chosen by the type of @a f
+JSON_HEDLEY_NON_NULL(2)
+inline void strtof_by_type(long double& f, const char* str, char** endptr) noexcept
+{
+    f = std::strtold(str, endptr);
+}
+
+/// return the decimal point of the current locale
+inline char get_decimal_point() noexcept
+{
+    const auto* loc = localeconv();
+    JSON_ASSERT(loc != nullptr);
+    return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point);
+}
+
+/*!
+@brief convert a validated float token with strtof/strtod/strtold
+
+These functions expect the decimal point of the *current* locale, so it is
+looked up right before the conversion instead of once when the lexer is
+constructed: a locale change in between (by a parser callback, a SAX
+handler, or another thread) must not truncate the value (#5198). The
+token has been validated before, so if the conversion stops early and the
+decimal point changed in the meantime, the locale changed between the
+lookup and the call, and the conversion is repeated with the new decimal
+point. If the decimal point did not change, a retry cannot succeed: the
+locale's decimal point is not a single character (e.g., the two-byte
+U+066B of ar_EG.UTF-8 or fa_IR.UTF-8) and cannot be substituted in place.
+The value strtod parsed up to that point is kept, as before this change.
+
+Note that changing the locale in another thread *while* strtod runs is
+undefined behavior of the C library, which this function cannot prevent.
+
+@param[in,out] token                   the token with '.' as decimal point; its
+                                       decimal point is replaced during the
+                                       conversion and restored afterwards
+                                       (data() must be NUL-terminated)
+@param[in]     decimal_point_position  index of the '.' in @a token, or
+                                       std::string::npos if there is none
+@param[out]    value                   the converted value
+*/
+template<typename StringType, typename FloatType>
+void convert_float_locale_aware(StringType& token, std::size_t decimal_point_position, FloatType& value)
+{
+    const bool has_dot = decimal_point_position != std::string::npos;
+    char decimal_point = get_decimal_point();
+    for (;;)
+    {
+        const bool substitute = has_dot && decimal_point != '.';
+        if (substitute)
+        {
+            token[decimal_point_position] = static_cast<typename StringType::value_type>(decimal_point);
+        }
+
+        char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+        strtof_by_type(value, token.data(), &endptr);
+
+        if (substitute)
+        {
+            // the caller hands the token on (e.g. to the SAX interface) with '.'
+            token[decimal_point_position] = '.';
+        }
+
+        if (JSON_HEDLEY_LIKELY(endptr == token.data() + token.size()))
+        {
+            return;
+        }
+
+        // retry only if the locale changed; otherwise, this would loop forever
+        const char current_decimal_point = get_decimal_point();
+        if (current_decimal_point == decimal_point)
+        {
+            return;
+        }
+        decimal_point = current_decimal_point;
+    }
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/input/pow5_table.hpp

@@ -0,0 +1,371 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2021 The fast_float authors <https://github.com/fastfloat/fast_float>
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <array> // array
+#include <cstdint> // int64_t, uint64_t
+
+#include <nlohmann/detail/abi_macros.hpp>
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+/// the range of decimal exponents covered by pow5_128()
+constexpr std::int64_t pow5_128_smallest_power = -342;
+constexpr std::int64_t pow5_128_largest_power = 308;
+
+/*!
+@brief 128-bit approximations of 5^q for q in [-342, 308]
+
+Entry q (at index 2 * (q + 342)) holds the most significant 128 bits of 5^q,
+normalized so that the highest bit is set: for q >= 0 the truncated value, for
+q < 0 the value rounded up. This is the table of fast_float (Daniel Lemire and
+contributors, used under the MIT license), generated like its
+script/table_generation.py; unit-class_lexer.cpp recomputes every entry.
+*/
+inline const std::array<std::uint64_t, 1302>& pow5_128() noexcept
+{
+    static const std::array<std::uint64_t, 1302> table =
+    {
+        {
+            0xeef453d6923bd65au, 0x113faa2906a13b3fu, 0x9558b4661b6565f8u, 0x4ac7ca59a424c507u,
+            0xbaaee17fa23ebf76u, 0x5d79bcf00d2df649u, 0xe95a99df8ace6f53u, 0xf4d82c2c107973dcu,
+            0x91d8a02bb6c10594u, 0x79071b9b8a4be869u, 0xb64ec836a47146f9u, 0x9748e2826cdee284u,
+            0xe3e27a444d8d98b7u, 0xfd1b1b2308169b25u, 0x8e6d8c6ab0787f72u, 0xfe30f0f5e50e20f7u,
+            0xb208ef855c969f4fu, 0xbdbd2d335e51a935u, 0xde8b2b66b3bc4723u, 0xad2c788035e61382u,
+            0x8b16fb203055ac76u, 0x4c3bcb5021afcc31u, 0xaddcb9e83c6b1793u, 0xdf4abe242a1bbf3du,
+            0xd953e8624b85dd78u, 0xd71d6dad34a2af0du, 0x87d4713d6f33aa6bu, 0x8672648c40e5ad68u,
+            0xa9c98d8ccb009506u, 0x680efdaf511f18c2u, 0xd43bf0effdc0ba48u, 0x0212bd1b2566def2u,
+            0x84a57695fe98746du, 0x014bb630f7604b57u, 0xa5ced43b7e3e9188u, 0x419ea3bd35385e2du,
+            0xcf42894a5dce35eau, 0x52064cac828675b9u, 0x818995ce7aa0e1b2u, 0x7343efebd1940993u,
+            0xa1ebfb4219491a1fu, 0x1014ebe6c5f90bf8u, 0xca66fa129f9b60a6u, 0xd41a26e077774ef6u,
+            0xfd00b897478238d0u, 0x8920b098955522b4u, 0x9e20735e8cb16382u, 0x55b46e5f5d5535b0u,
+            0xc5a890362fddbc62u, 0xeb2189f734aa831du, 0xf712b443bbd52b7bu, 0xa5e9ec7501d523e4u,
+            0x9a6bb0aa55653b2du, 0x47b233c92125366eu, 0xc1069cd4eabe89f8u, 0x999ec0bb696e840au,
+            0xf148440a256e2c76u, 0xc00670ea43ca250du, 0x96cd2a865764dbcau, 0x380406926a5e5728u,
+            0xbc807527ed3e12bcu, 0xc605083704f5ecf2u, 0xeba09271e88d976bu, 0xf7864a44c633682eu,
+            0x93445b8731587ea3u, 0x7ab3ee6afbe0211du, 0xb8157268fdae9e4cu, 0x5960ea05bad82964u,
+            0xe61acf033d1a45dfu, 0x6fb92487298e33bdu, 0x8fd0c16206306babu, 0xa5d3b6d479f8e056u,
+            0xb3c4f1ba87bc8696u, 0x8f48a4899877186cu, 0xe0b62e2929aba83cu, 0x331acdabfe94de87u,
+            0x8c71dcd9ba0b4925u, 0x9ff0c08b7f1d0b14u, 0xaf8e5410288e1b6fu, 0x07ecf0ae5ee44dd9u,
+            0xdb71e91432b1a24au, 0xc9e82cd9f69d6150u, 0x892731ac9faf056eu, 0xbe311c083a225cd2u,
+            0xab70fe17c79ac6cau, 0x6dbd630a48aaf406u, 0xd64d3d9db981787du, 0x092cbbccdad5b108u,
+            0x85f0468293f0eb4eu, 0x25bbf56008c58ea5u, 0xa76c582338ed2621u, 0xaf2af2b80af6f24eu,
+            0xd1476e2c07286faau, 0x1af5af660db4aee1u, 0x82cca4db847945cau, 0x50d98d9fc890ed4du,
+            0xa37fce126597973cu, 0xe50ff107bab528a0u, 0xcc5fc196fefd7d0cu, 0x1e53ed49a96272c8u,
+            0xff77b1fcbebcdc4fu, 0x25e8e89c13bb0f7au, 0x9faacf3df73609b1u, 0x77b191618c54e9acu,
+            0xc795830d75038c1du, 0xd59df5b9ef6a2417u, 0xf97ae3d0d2446f25u, 0x4b0573286b44ad1du,
+            0x9becce62836ac577u, 0x4ee367f9430aec32u, 0xc2e801fb244576d5u, 0x229c41f793cda73fu,
+            0xf3a20279ed56d48au, 0x6b43527578c1110fu, 0x9845418c345644d6u, 0x830a13896b78aaa9u,
+            0xbe5691ef416bd60cu, 0x23cc986bc656d553u, 0xedec366b11c6cb8fu, 0x2cbfbe86b7ec8aa8u,
+            0x94b3a202eb1c3f39u, 0x7bf7d71432f3d6a9u, 0xb9e08a83a5e34f07u, 0xdaf5ccd93fb0cc53u,
+            0xe858ad248f5c22c9u, 0xd1b3400f8f9cff68u, 0x91376c36d99995beu, 0x23100809b9c21fa1u,
+            0xb58547448ffffb2du, 0xabd40a0c2832a78au, 0xe2e69915b3fff9f9u, 0x16c90c8f323f516cu,
+            0x8dd01fad907ffc3bu, 0xae3da7d97f6792e3u, 0xb1442798f49ffb4au, 0x99cd11cfdf41779cu,
+            0xdd95317f31c7fa1du, 0x40405643d711d583u, 0x8a7d3eef7f1cfc52u, 0x482835ea666b2572u,
+            0xad1c8eab5ee43b66u, 0xda3243650005eecfu, 0xd863b256369d4a40u, 0x90bed43e40076a82u,
+            0x873e4f75e2224e68u, 0x5a7744a6e804a291u, 0xa90de3535aaae202u, 0x711515d0a205cb36u,
+            0xd3515c2831559a83u, 0x0d5a5b44ca873e03u, 0x8412d9991ed58091u, 0xe858790afe9486c2u,
+            0xa5178fff668ae0b6u, 0x626e974dbe39a872u, 0xce5d73ff402d98e3u, 0xfb0a3d212dc8128fu,
+            0x80fa687f881c7f8eu, 0x7ce66634bc9d0b99u, 0xa139029f6a239f72u, 0x1c1fffc1ebc44e80u,
+            0xc987434744ac874eu, 0xa327ffb266b56220u, 0xfbe9141915d7a922u, 0x4bf1ff9f0062baa8u,
+            0x9d71ac8fada6c9b5u, 0x6f773fc3603db4a9u, 0xc4ce17b399107c22u, 0xcb550fb4384d21d3u,
+            0xf6019da07f549b2bu, 0x7e2a53a146606a48u, 0x99c102844f94e0fbu, 0x2eda7444cbfc426du,
+            0xc0314325637a1939u, 0xfa911155fefb5308u, 0xf03d93eebc589f88u, 0x793555ab7eba27cau,
+            0x96267c7535b763b5u, 0x4bc1558b2f3458deu, 0xbbb01b9283253ca2u, 0x9eb1aaedfb016f16u,
+            0xea9c227723ee8bcbu, 0x465e15a979c1cadcu, 0x92a1958a7675175fu, 0x0bfacd89ec191ec9u,
+            0xb749faed14125d36u, 0xcef980ec671f667bu, 0xe51c79a85916f484u, 0x82b7e12780e7401au,
+            0x8f31cc0937ae58d2u, 0xd1b2ecb8b0908810u, 0xb2fe3f0b8599ef07u, 0x861fa7e6dcb4aa15u,
+            0xdfbdcece67006ac9u, 0x67a791e093e1d49au, 0x8bd6a141006042bdu, 0xe0c8bb2c5c6d24e0u,
+            0xaecc49914078536du, 0x58fae9f773886e18u, 0xda7f5bf590966848u, 0xaf39a475506a899eu,
+            0x888f99797a5e012du, 0x6d8406c952429603u, 0xaab37fd7d8f58178u, 0xc8e5087ba6d33b83u,
+            0xd5605fcdcf32e1d6u, 0xfb1e4a9a90880a64u, 0x855c3be0a17fcd26u, 0x5cf2eea09a55067fu,
+            0xa6b34ad8c9dfc06fu, 0xf42faa48c0ea481eu, 0xd0601d8efc57b08bu, 0xf13b94daf124da26u,
+            0x823c12795db6ce57u, 0x76c53d08d6b70858u, 0xa2cb1717b52481edu, 0x54768c4b0c64ca6eu,
+            0xcb7ddcdda26da268u, 0xa9942f5dcf7dfd09u, 0xfe5d54150b090b02u, 0xd3f93b35435d7c4cu,
+            0x9efa548d26e5a6e1u, 0xc47bc5014a1a6dafu, 0xc6b8e9b0709f109au, 0x359ab6419ca1091bu,
+            0xf867241c8cc6d4c0u, 0xc30163d203c94b62u, 0x9b407691d7fc44f8u, 0x79e0de63425dcf1du,
+            0xc21094364dfb5636u, 0x985915fc12f542e4u, 0xf294b943e17a2bc4u, 0x3e6f5b7b17b2939du,
+            0x979cf3ca6cec5b5au, 0xa705992ceecf9c42u, 0xbd8430bd08277231u, 0x50c6ff782a838353u,
+            0xece53cec4a314ebdu, 0xa4f8bf5635246428u, 0x940f4613ae5ed136u, 0x871b7795e136be99u,
+            0xb913179899f68584u, 0x28e2557b59846e3fu, 0xe757dd7ec07426e5u, 0x331aeada2fe589cfu,
+            0x9096ea6f3848984fu, 0x3ff0d2c85def7621u, 0xb4bca50b065abe63u, 0x0fed077a756b53a9u,
+            0xe1ebce4dc7f16dfbu, 0xd3e8495912c62894u, 0x8d3360f09cf6e4bdu, 0x64712dd7abbbd95cu,
+            0xb080392cc4349decu, 0xbd8d794d96aacfb3u, 0xdca04777f541c567u, 0xecf0d7a0fc5583a0u,
+            0x89e42caaf9491b60u, 0xf41686c49db57244u, 0xac5d37d5b79b6239u, 0x311c2875c522ced5u,
+            0xd77485cb25823ac7u, 0x7d633293366b828bu, 0x86a8d39ef77164bcu, 0xae5dff9c02033197u,
+            0xa8530886b54dbdebu, 0xd9f57f830283fdfcu, 0xd267caa862a12d66u, 0xd072df63c324fd7bu,
+            0x8380dea93da4bc60u, 0x4247cb9e59f71e6du, 0xa46116538d0deb78u, 0x52d9be85f074e608u,
+            0xcd795be870516656u, 0x67902e276c921f8bu, 0x806bd9714632dff6u, 0x00ba1cd8a3db53b6u,
+            0xa086cfcd97bf97f3u, 0x80e8a40eccd228a4u, 0xc8a883c0fdaf7df0u, 0x6122cd128006b2cdu,
+            0xfad2a4b13d1b5d6cu, 0x796b805720085f81u, 0x9cc3a6eec6311a63u, 0xcbe3303674053bb0u,
+            0xc3f490aa77bd60fcu, 0xbedbfc4411068a9cu, 0xf4f1b4d515acb93bu, 0xee92fb5515482d44u,
+            0x991711052d8bf3c5u, 0x751bdd152d4d1c4au, 0xbf5cd54678eef0b6u, 0xd262d45a78a0635du,
+            0xef340a98172aace4u, 0x86fb897116c87c34u, 0x9580869f0e7aac0eu, 0xd45d35e6ae3d4da0u,
+            0xbae0a846d2195712u, 0x8974836059cca109u, 0xe998d258869facd7u, 0x2bd1a438703fc94bu,
+            0x91ff83775423cc06u, 0x7b6306a34627ddcfu, 0xb67f6455292cbf08u, 0x1a3bc84c17b1d542u,
+            0xe41f3d6a7377eecau, 0x20caba5f1d9e4a93u, 0x8e938662882af53eu, 0x547eb47b7282ee9cu,
+            0xb23867fb2a35b28du, 0xe99e619a4f23aa43u, 0xdec681f9f4c31f31u, 0x6405fa00e2ec94d4u,
+            0x8b3c113c38f9f37eu, 0xde83bc408dd3dd04u, 0xae0b158b4738705eu, 0x9624ab50b148d445u,
+            0xd98ddaee19068c76u, 0x3badd624dd9b0957u, 0x87f8a8d4cfa417c9u, 0xe54ca5d70a80e5d6u,
+            0xa9f6d30a038d1dbcu, 0x5e9fcf4ccd211f4cu, 0xd47487cc8470652bu, 0x7647c3200069671fu,
+            0x84c8d4dfd2c63f3bu, 0x29ecd9f40041e073u, 0xa5fb0a17c777cf09u, 0xf468107100525890u,
+            0xcf79cc9db955c2ccu, 0x7182148d4066eeb4u, 0x81ac1fe293d599bfu, 0xc6f14cd848405530u,
+            0xa21727db38cb002fu, 0xb8ada00e5a506a7cu, 0xca9cf1d206fdc03bu, 0xa6d90811f0e4851cu,
+            0xfd442e4688bd304au, 0x908f4a166d1da663u, 0x9e4a9cec15763e2eu, 0x9a598e4e043287feu,
+            0xc5dd44271ad3cdbau, 0x40eff1e1853f29fdu, 0xf7549530e188c128u, 0xd12bee59e68ef47cu,
+            0x9a94dd3e8cf578b9u, 0x82bb74f8301958ceu, 0xc13a148e3032d6e7u, 0xe36a52363c1faf01u,
+            0xf18899b1bc3f8ca1u, 0xdc44e6c3cb279ac1u, 0x96f5600f15a7b7e5u, 0x29ab103a5ef8c0b9u,
+            0xbcb2b812db11a5deu, 0x7415d448f6b6f0e7u, 0xebdf661791d60f56u, 0x111b495b3464ad21u,
+            0x936b9fcebb25c995u, 0xcab10dd900beec34u, 0xb84687c269ef3bfbu, 0x3d5d514f40eea742u,
+            0xe65829b3046b0afau, 0x0cb4a5a3112a5112u, 0x8ff71a0fe2c2e6dcu, 0x47f0e785eaba72abu,
+            0xb3f4e093db73a093u, 0x59ed216765690f56u, 0xe0f218b8d25088b8u, 0x306869c13ec3532cu,
+            0x8c974f7383725573u, 0x1e414218c73a13fbu, 0xafbd2350644eeacfu, 0xe5d1929ef90898fau,
+            0xdbac6c247d62a583u, 0xdf45f746b74abf39u, 0x894bc396ce5da772u, 0x6b8bba8c328eb783u,
+            0xab9eb47c81f5114fu, 0x066ea92f3f326564u, 0xd686619ba27255a2u, 0xc80a537b0efefebdu,
+            0x8613fd0145877585u, 0xbd06742ce95f5f36u, 0xa798fc4196e952e7u, 0x2c48113823b73704u,
+            0xd17f3b51fca3a7a0u, 0xf75a15862ca504c5u, 0x82ef85133de648c4u, 0x9a984d73dbe722fbu,
+            0xa3ab66580d5fdaf5u, 0xc13e60d0d2e0ebbau, 0xcc963fee10b7d1b3u, 0x318df905079926a8u,
+            0xffbbcfe994e5c61fu, 0xfdf17746497f7052u, 0x9fd561f1fd0f9bd3u, 0xfeb6ea8bedefa633u,
+            0xc7caba6e7c5382c8u, 0xfe64a52ee96b8fc0u, 0xf9bd690a1b68637bu, 0x3dfdce7aa3c673b0u,
+            0x9c1661a651213e2du, 0x06bea10ca65c084eu, 0xc31bfa0fe5698db8u, 0x486e494fcff30a62u,
+            0xf3e2f893dec3f126u, 0x5a89dba3c3efccfau, 0x986ddb5c6b3a76b7u, 0xf89629465a75e01cu,
+            0xbe89523386091465u, 0xf6bbb397f1135823u, 0xee2ba6c0678b597fu, 0x746aa07ded582e2cu,
+            0x94db483840b717efu, 0xa8c2a44eb4571cdcu, 0xba121a4650e4ddebu, 0x92f34d62616ce413u,
+            0xe896a0d7e51e1566u, 0x77b020baf9c81d17u, 0x915e2486ef32cd60u, 0x0ace1474dc1d122eu,
+            0xb5b5ada8aaff80b8u, 0x0d819992132456bau, 0xe3231912d5bf60e6u, 0x10e1fff697ed6c69u,
+            0x8df5efabc5979c8fu, 0xca8d3ffa1ef463c1u, 0xb1736b96b6fd83b3u, 0xbd308ff8a6b17cb2u,
+            0xddd0467c64bce4a0u, 0xac7cb3f6d05ddbdeu, 0x8aa22c0dbef60ee4u, 0x6bcdf07a423aa96bu,
+            0xad4ab7112eb3929du, 0x86c16c98d2c953c6u, 0xd89d64d57a607744u, 0xe871c7bf077ba8b7u,
+            0x87625f056c7c4a8bu, 0x11471cd764ad4972u, 0xa93af6c6c79b5d2du, 0xd598e40d3dd89bcfu,
+            0xd389b47879823479u, 0x4aff1d108d4ec2c3u, 0x843610cb4bf160cbu, 0xcedf722a585139bau,
+            0xa54394fe1eedb8feu, 0xc2974eb4ee658828u, 0xce947a3da6a9273eu, 0x733d226229feea32u,
+            0x811ccc668829b887u, 0x0806357d5a3f525fu, 0xa163ff802a3426a8u, 0xca07c2dcb0cf26f7u,
+            0xc9bcff6034c13052u, 0xfc89b393dd02f0b5u, 0xfc2c3f3841f17c67u, 0xbbac2078d443ace2u,
+            0x9d9ba7832936edc0u, 0xd54b944b84aa4c0du, 0xc5029163f384a931u, 0x0a9e795e65d4df11u,
+            0xf64335bcf065d37du, 0x4d4617b5ff4a16d5u, 0x99ea0196163fa42eu, 0x504bced1bf8e4e45u,
+            0xc06481fb9bcf8d39u, 0xe45ec2862f71e1d6u, 0xf07da27a82c37088u, 0x5d767327bb4e5a4cu,
+            0x964e858c91ba2655u, 0x3a6a07f8d510f86fu, 0xbbe226efb628afeau, 0x890489f70a55368bu,
+            0xeadab0aba3b2dbe5u, 0x2b45ac74ccea842eu, 0x92c8ae6b464fc96fu, 0x3b0b8bc90012929du,
+            0xb77ada0617e3bbcbu, 0x09ce6ebb40173744u, 0xe55990879ddcaabdu, 0xcc420a6a101d0515u,
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+            0xe070f78d3927556au, 0x85bbe253f47b1417u, 0x8c469ab843b89562u, 0x93956d7478ccec8eu,
+            0xaf58416654a6babbu, 0x387ac8d1970027b2u, 0xdb2e51bfe9d0696au, 0x06997b05fcc0319eu,
+            0x88fcf317f22241e2u, 0x441fece3bdf81f03u, 0xab3c2fddeeaad25au, 0xd527e81cad7626c3u,
+            0xd60b3bd56a5586f1u, 0x8a71e223d8d3b074u, 0x85c7056562757456u, 0xf6872d5667844e49u,
+            0xa738c6bebb12d16cu, 0xb428f8ac016561dbu, 0xd106f86e69d785c7u, 0xe13336d701beba52u,
+            0x82a45b450226b39cu, 0xecc0024661173473u, 0xa34d721642b06084u, 0x27f002d7f95d0190u,
+            0xcc20ce9bd35c78a5u, 0x31ec038df7b441f4u, 0xff290242c83396ceu, 0x7e67047175a15271u,
+            0x9f79a169bd203e41u, 0x0f0062c6e984d386u, 0xc75809c42c684dd1u, 0x52c07b78a3e60868u,
+            0xf92e0c3537826145u, 0xa7709a56ccdf8a82u, 0x9bbcc7a142b17ccbu, 0x88a66076400bb691u,
+            0xc2abf989935ddbfeu, 0x6acff893d00ea435u, 0xf356f7ebf83552feu, 0x0583f6b8c4124d43u,
+            0x98165af37b2153deu, 0xc3727a337a8b704au, 0xbe1bf1b059e9a8d6u, 0x744f18c0592e4c5cu,
+            0xeda2ee1c7064130cu, 0x1162def06f79df73u, 0x9485d4d1c63e8be7u, 0x8addcb5645ac2ba8u,
+            0xb9a74a0637ce2ee1u, 0x6d953e2bd7173692u, 0xe8111c87c5c1ba99u, 0xc8fa8db6ccdd0437u,
+            0x910ab1d4db9914a0u, 0x1d9c9892400a22a2u, 0xb54d5e4a127f59c8u, 0x2503beb6d00cab4bu,
+            0xe2a0b5dc971f303au, 0x2e44ae64840fd61du, 0x8da471a9de737e24u, 0x5ceaecfed289e5d2u,
+            0xb10d8e1456105dadu, 0x7425a83e872c5f47u, 0xdd50f1996b947518u, 0xd12f124e28f77719u,
+            0x8a5296ffe33cc92fu, 0x82bd6b70d99aaa6fu, 0xace73cbfdc0bfb7bu, 0x636cc64d1001550bu,
+            0xd8210befd30efa5au, 0x3c47f7e05401aa4eu, 0x8714a775e3e95c78u, 0x65acfaec34810a71u,
+            0xa8d9d1535ce3b396u, 0x7f1839a741a14d0du, 0xd31045a8341ca07cu, 0x1ede48111209a050u,
+            0x83ea2b892091e44du, 0x934aed0aab460432u, 0xa4e4b66b68b65d60u, 0xf81da84d5617853fu,
+            0xce1de40642e3f4b9u, 0x36251260ab9d668eu, 0x80d2ae83e9ce78f3u, 0xc1d72b7c6b426019u,
+            0xa1075a24e4421730u, 0xb24cf65b8612f81fu, 0xc94930ae1d529cfcu, 0xdee033f26797b627u,
+            0xfb9b7cd9a4a7443cu, 0x169840ef017da3b1u, 0x9d412e0806e88aa5u, 0x8e1f289560ee864eu,
+            0xc491798a08a2ad4eu, 0xf1a6f2bab92a27e2u, 0xf5b5d7ec8acb58a2u, 0xae10af696774b1dbu,
+            0x9991a6f3d6bf1765u, 0xacca6da1e0a8ef29u, 0xbff610b0cc6edd3fu, 0x17fd090a58d32af3u,
+            0xeff394dcff8a948eu, 0xddfc4b4cef07f5b0u, 0x95f83d0a1fb69cd9u, 0x4abdaf101564f98eu,
+            0xbb764c4ca7a4440fu, 0x9d6d1ad41abe37f1u, 0xea53df5fd18d5513u, 0x84c86189216dc5edu,
+            0x92746b9be2f8552cu, 0x32fd3cf5b4e49bb4u, 0xb7118682dbb66a77u, 0x3fbc8c33221dc2a1u,
+            0xe4d5e82392a40515u, 0x0fabaf3feaa5334au, 0x8f05b1163ba6832du, 0x29cb4d87f2a7400eu,
+            0xb2c71d5bca9023f8u, 0x743e20e9ef511012u, 0xdf78e4b2bd342cf6u, 0x914da9246b255416u,
+            0x8bab8eefb6409c1au, 0x1ad089b6c2f7548eu, 0xae9672aba3d0c320u, 0xa184ac2473b529b1u,
+            0xda3c0f568cc4f3e8u, 0xc9e5d72d90a2741eu, 0x8865899617fb1871u, 0x7e2fa67c7a658892u,
+            0xaa7eebfb9df9de8du, 0xddbb901b98feeab7u, 0xd51ea6fa85785631u, 0x552a74227f3ea565u,
+            0x8533285c936b35deu, 0xd53a88958f87275fu, 0xa67ff273b8460356u, 0x8a892abaf368f137u,
+            0xd01fef10a657842cu, 0x2d2b7569b0432d85u, 0x8213f56a67f6b29bu, 0x9c3b29620e29fc73u,
+            0xa298f2c501f45f42u, 0x8349f3ba91b47b8fu, 0xcb3f2f7642717713u, 0x241c70a936219a73u,
+            0xfe0efb53d30dd4d7u, 0xed238cd383aa0110u, 0x9ec95d1463e8a506u, 0xf4363804324a40aau,
+            0xc67bb4597ce2ce48u, 0xb143c6053edcd0d5u, 0xf81aa16fdc1b81dau, 0xdd94b7868e94050au,
+            0x9b10a4e5e9913128u, 0xca7cf2b4191c8326u, 0xc1d4ce1f63f57d72u, 0xfd1c2f611f63a3f0u,
+            0xf24a01a73cf2dccfu, 0xbc633b39673c8cecu, 0x976e41088617ca01u, 0xd5be0503e085d813u,
+            0xbd49d14aa79dbc82u, 0x4b2d8644d8a74e18u, 0xec9c459d51852ba2u, 0xddf8e7d60ed1219eu,
+            0x93e1ab8252f33b45u, 0xcabb90e5c942b503u, 0xb8da1662e7b00a17u, 0x3d6a751f3b936243u,
+            0xe7109bfba19c0c9du, 0x0cc512670a783ad4u, 0x906a617d450187e2u, 0x27fb2b80668b24c5u,
+            0xb484f9dc9641e9dau, 0xb1f9f660802dedf6u, 0xe1a63853bbd26451u, 0x5e7873f8a0396973u,
+            0x8d07e33455637eb2u, 0xdb0b487b6423e1e8u, 0xb049dc016abc5e5fu, 0x91ce1a9a3d2cda62u,
+            0xdc5c5301c56b75f7u, 0x7641a140cc7810fbu, 0x89b9b3e11b6329bau, 0xa9e904c87fcb0a9du,
+            0xac2820d9623bf429u, 0x546345fa9fbdcd44u, 0xd732290fbacaf133u, 0xa97c177947ad4095u,
+            0x867f59a9d4bed6c0u, 0x49ed8eabcccc485du, 0xa81f301449ee8c70u, 0x5c68f256bfff5a74u,
+            0xd226fc195c6a2f8cu, 0x73832eec6fff3111u, 0x83585d8fd9c25db7u, 0xc831fd53c5ff7eabu,
+            0xa42e74f3d032f525u, 0xba3e7ca8b77f5e55u, 0xcd3a1230c43fb26fu, 0x28ce1bd2e55f35ebu,
+            0x80444b5e7aa7cf85u, 0x7980d163cf5b81b3u, 0xa0555e361951c366u, 0xd7e105bcc332621fu,
+            0xc86ab5c39fa63440u, 0x8dd9472bf3fefaa7u, 0xfa856334878fc150u, 0xb14f98f6f0feb951u,
+            0x9c935e00d4b9d8d2u, 0x6ed1bf9a569f33d3u, 0xc3b8358109e84f07u, 0x0a862f80ec4700c8u,
+            0xf4a642e14c6262c8u, 0xcd27bb612758c0fau, 0x98e7e9cccfbd7dbdu, 0x8038d51cb897789cu,
+            0xbf21e44003acdd2cu, 0xe0470a63e6bd56c3u, 0xeeea5d5004981478u, 0x1858ccfce06cac74u,
+            0x95527a5202df0ccbu, 0x0f37801e0c43ebc8u, 0xbaa718e68396cffdu, 0xd30560258f54e6bau,
+            0xe950df20247c83fdu, 0x47c6b82ef32a2069u, 0x91d28b7416cdd27eu, 0x4cdc331d57fa5441u,
+            0xb6472e511c81471du, 0xe0133fe4adf8e952u, 0xe3d8f9e563a198e5u, 0x58180fddd97723a6u,
+            0x8e679c2f5e44ff8fu, 0x570f09eaa7ea7648u,
+        }
+    };
+    return table;
+}
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/json_pointer.hpp

@@ -26,6 +26,7 @@
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/string_concat.hpp>
 #include <nlohmann/detail/string_escape.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -116,7 +117,7 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slasheq/
     json_pointer& operator/=(std::size_t array_idx)
     {
-        return *this /= std::to_string(array_idx);
+        return *this /= detail::to_string<string_t>(array_idx);
     }
 
     /// @brief create a new JSON pointer by appending the right JSON pointer at the end of the left JSON pointer
@@ -746,7 +747,13 @@ class json_pointer
                         // "-" always fails the range check
                         return false;
                     }
-                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !("0" <= reference_token && reference_token <= "9")))
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.empty()))
+                    {
+                        // an empty reference token is not an array index; array_index()
+                        // would throw out_of_range.404 -- contains() must not throw (see #5395)
+                        return false;
+                    }
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !('0' <= reference_token[0] && reference_token[0] <= '9')))
                     {
                         // invalid char
                         return false;
@@ -774,7 +781,7 @@ class json_pointer
                     // not throw (see #5395), so such a reference token is treated as "not found"
                     errno = 0; // strtoull() does not reset errno on success
                     char* p_end = nullptr; // NOLINT(misc-const-correctness)
-                    const unsigned long long magnitude = std::strtoull(reference_token.c_str(), &p_end, 10); // NOLINT(runtime/int)
+                    const unsigned long long magnitude = std::strtoull(reference_token.data(), &p_end, 10); // NOLINT(runtime/int)
                     if (JSON_HEDLEY_UNLIKELY(errno == ERANGE // the value exceeds ULLONG_MAX
                                              || magnitude >= static_cast<unsigned long long>((std::numeric_limits<typename BasicJsonType::size_type>::max)()))) // NOLINT(runtime/int)
                     {

include/nlohmann/detail/macro_scope.hpp

@@ -336,7 +336,7 @@ void templated_json_throw(ExceptionType exception)
             return ej_pair.second == j;                                                         \
         });                                                                                     \
         if (it != std::end(m)) e = it->first;                                                   \
-        else templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410,"enum value out of range for " #ENUM_TYPE ": " + j.dump(), &j)); \
+        else templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410, nlohmann::detail::concat("enum value out of range for " #ENUM_TYPE ": ", j.dump(-1, ' ', false, nlohmann::detail::error_handler_t::replace)), &j)); \
     }
 
 // Ugly macros to avoid uglier copy-paste when specializing basic_json. They
@@ -915,7 +915,3 @@ void templated_json_throw(ExceptionType exception)
 #ifndef JSON_DISABLE_ENUM_SERIALIZATION
     #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif
-
-#ifndef JSON_USE_GLOBAL_UDLS
-    #define JSON_USE_GLOBAL_UDLS 1
-#endif

include/nlohmann/detail/macro_unscope.hpp

@@ -25,7 +25,6 @@
 #undef JSON_INLINE_VARIABLE
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
-#undef JSON_USE_GLOBAL_UDLS
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH

include/nlohmann/detail/meta/type_traits.hpp

@@ -189,6 +189,37 @@ struct actual_object_comparator
 template<typename BasicJsonType>
 using actual_object_comparator_t = typename actual_object_comparator<BasicJsonType>::type;
 
+template<typename T>
+using detect_key_comp = decltype(std::declval<const T&>().key_comp());
+
+// whether ObjectType can be constructed from a pair of Iterator together with
+// a copy of its own comparator, the way std::map can: it needs a nested
+// key_compare, a const key_comp() convertible to it, and a matching
+// (Iterator, Iterator, const key_compare&) constructor.
+//
+// used to preserve a stateful comparator when a copy is built from a range
+// past the iterative deep copy's nesting bound (see copy_object_level); an
+// object type that does not satisfy this, such as nlohmann::ordered_map
+// (which has key_compare for its std::map-like interface, but no key_comp()),
+// keeps default-constructing its comparator, just as it always has
+template<typename ObjectType, typename Iterator, typename = void>
+struct is_comparator_constructible_object_type_impl : std::false_type {};
+
+template<typename ObjectType, typename Iterator>
+struct is_comparator_constructible_object_type_impl <
+    ObjectType, Iterator, enable_if_t<is_detected<detect_key_compare, ObjectType>::value >>
+{
+    using key_compare = typename ObjectType::key_compare;
+
+    static constexpr bool value =
+        is_detected_convertible<key_compare, detect_key_comp, ObjectType>::value &&
+        std::is_constructible<ObjectType, Iterator, Iterator, const key_compare&>::value;
+};
+
+template<typename ObjectType, typename Iterator>
+struct is_comparator_constructible_object_type
+    : is_comparator_constructible_object_type_impl<ObjectType, Iterator> {};
+
 /////////////////
 // char_traits //
 /////////////////
@@ -725,7 +756,7 @@ std::is_constructible <decltype(std::declval<Compare>()(std::declval<A>(), std::
 // avoid their instantiation on all compilers, even when the first operand
 // is false. The dispatch on is_json_pointer_of can be removed once the
 // deprecated json_pointer comparison operators have been removed.
-template<typename Compare, typename A, typename B, bool = is_json_pointer_of<A, B>::value>
+template<typename Compare, typename A, typename B, bool = is_json_pointer_of<uncvref_t<A>, uncvref_t<B>>::value>
 struct is_comparable : std::false_type {};
 
 template<typename Compare, typename A, typename B>

include/nlohmann/detail/output/binary_writer.hpp

@@ -337,24 +337,25 @@ class binary_writer
                     // MessagePack does not differentiate between positive
                     // signed integers and unsigned integers. Therefore, we used
                     // the code from the value_t::number_unsigned case here.
-                    if (j.m_data.m_value.number_unsigned < 128)
+                    const auto value_as_unsigned = static_cast<typename BasicJsonType::number_unsigned_t>(j.m_data.m_value.number_integer);
+                    if (value_as_unsigned < 128)
                     {
                         // positive fixnum
                         write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint8_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint8_t>::max)())
                     {
                         // uint 8
                         oa.write_character(to_char_type(0xCC));
                         write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint16_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint16_t>::max)())
                     {
                         // uint 16
                         oa.write_character(to_char_type(0xCD));
                         write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_integer));
                     }
-                    else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint32_t>::max)())
+                    else if (value_as_unsigned <= (std::numeric_limits<std::uint32_t>::max)())
                     {
                         // uint 32
                         oa.write_character(to_char_type(0xCE));
@@ -410,31 +411,31 @@ class binary_writer
                 if (j.m_data.m_value.number_unsigned < 128)
                 {
                     // positive fixnum
-                    write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
+                    write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_unsigned));
                 }
                 else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint8_t>::max)())
                 {
                     // uint 8
                     oa.write_character(to_char_type(0xCC));
-                    write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
+                    write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_unsigned));
                 }
                 else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint16_t>::max)())
                 {
                     // uint 16
                     oa.write_character(to_char_type(0xCD));
-                    write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_integer));
+                    write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_unsigned));
                 }
                 else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint32_t>::max)())
                 {
                     // uint 32
                     oa.write_character(to_char_type(0xCE));
-                    write_number(static_cast<std::uint32_t>(j.m_data.m_value.number_integer));
+                    write_number(static_cast<std::uint32_t>(j.m_data.m_value.number_unsigned));
                 }
                 else
                 {
                     // uint 64
                     oa.write_character(to_char_type(0xCF));
-                    write_number(static_cast<std::uint64_t>(j.m_data.m_value.number_integer));
+                    write_number(static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
                 }
                 break;
             }
@@ -1055,15 +1056,26 @@ class binary_writer
     }
 
     /*!
-    @return The size of the BSON-encoded binary array @a value
+    @return The size of the BSON-encoded binary array in @a j
+    @throw out_of_range.415 if the subtype of @a j does not fit into a byte,
+           before anything is written
     */
-    static std::size_t calc_bson_binary_size(const typename BasicJsonType::binary_t& value)
+    static std::size_t calc_bson_binary_size(const BasicJsonType& j)
     {
+        const auto& value = *j.m_data.m_value.binary;
+
+        if (value.has_subtype() && JSON_HEDLEY_UNLIKELY(value.subtype() > (std::numeric_limits<std::uint8_t>::max)()))
+        {
+            JSON_THROW(out_of_range::create(415, concat("subtype ", std::to_string(value.subtype()), " is too large for the BSON binary subtype (max 255)"), &j));
+        }
+
         return sizeof(std::int32_t) + value.size() + 1ul;
     }
 
     /*!
     @brief Writes a BSON element with key @a name and binary value @a value
+    @pre    @a value's subtype, if any, fits into a byte; @ref calc_bson_sizes
+            checks this for every binary value in the document beforehand.
     */
     void write_bson_binary(const string_t& name,
                            const binary_t& value)
@@ -1072,11 +1084,6 @@ class binary_writer
 
         write_number<std::int32_t>(to_bson_length(value.size()), true);
 
-        if (value.has_subtype() && JSON_HEDLEY_UNLIKELY(value.subtype() > (std::numeric_limits<std::uint8_t>::max)()))
-        {
-            JSON_THROW(out_of_range::create(415, concat("subtype ", std::to_string(value.subtype()), " is too large for the BSON binary subtype (max 255)"), nullptr));
-        }
-
         write_number(value.has_subtype() ? static_cast<std::uint8_t>(value.subtype()) : static_cast<std::uint8_t>(0x00));
 
         oa.write_characters(reinterpret_cast<const CharType*>(value.data()), value.size());
@@ -1085,13 +1092,15 @@ class binary_writer
     /*!
     @return The size of the value of the BSON document entry for @a j, which
             is neither an object nor an array
+    @throw out_of_range.415 if @a j is binary with a subtype that does not fit
+           into a byte, before anything is written
     */
     static std::size_t calc_bson_value_size(const BasicJsonType& j)
     {
         switch (j.type())
         {
             case value_t::binary:
-                return calc_bson_binary_size(*j.m_data.m_value.binary);
+                return calc_bson_binary_size(j);
 
             case value_t::boolean:
                 return 1ul;
@@ -1217,6 +1226,8 @@ class binary_writer
     @return the size of @a document
     @throw out_of_range.409 if a key contains U+0000, before anything is
            written
+    @throw out_of_range.415 if a binary value's subtype does not fit into a
+           byte, before anything is written
     */
     static std::size_t calc_bson_sizes(const BasicJsonType& document, std::vector<std::size_t>& nested_sizes)
     {

include/nlohmann/detail/recursion_depth_limit.hpp

@@ -19,11 +19,17 @@ namespace detail
 /*!
 @brief the number of nesting levels an operation recurses into
 
-Operations that walk a value (serializing, hashing, merging, ...) recurse once
+Operations that walk a value (copying, comparing, serializing, hashing, merging,
+...) recurse once
 per nesting level, which is fastest, but a value nested deeply enough would
 exhaust the call stack. So they recurse only this many levels deep and finish
 whatever lies below with an explicit stack. All of them share this limit.
 
+Most of them pass the depth down as an argument. The copy constructor and the
+comparison operators cannot, as their signatures are fixed, so they count it
+in basic_json::nesting_depth() instead, a byte per thread; the limit must
+therefore stay below 255.
+
 @sa https://github.com/nlohmann/json/issues/5387
 */
 constexpr std::size_t recursion_depth_limit() noexcept

include/nlohmann/json.hpp

@@ -36,7 +36,9 @@
     #include <iosfwd> // istream, ostream
 #endif  // JSON_NO_IO
 #include <iterator> // make_move_iterator, random_access_iterator_tag
+#include <limits> // numeric_limits
 #include <memory> // unique_ptr
+#include <stdexcept> // length_error
 #include <string> // string, stoi, to_string
 #include <utility> // declval, forward, move, pair, swap
 #include <vector> // vector
@@ -898,12 +900,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     }
 
 #ifndef JSON_NO_THREAD_LOCAL
-    /// the number of levels an operation descends into before it finishes the
-    /// value below it without the call stack
-    static constexpr std::uint8_t nesting_depth_limit()
-    {
-        return 128;
-    }
+    // nesting_depth() is a byte and may exceed the limit by one level
+    static_assert(detail::recursion_depth_limit() < 255, "the nesting depth count must fit in a byte");
 
     /*!
     @brief how many levels the operation going on in this thread has descended into
@@ -945,7 +943,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         static_cast<void>(may_descend);
         return true;
 #else
-        return !may_descend || nesting_depth() >= nesting_depth_limit();
+        return !may_descend || nesting_depth() >= detail::recursion_depth_limit();
 #endif
     }
 
@@ -969,7 +967,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 #ifdef JSON_NO_THREAD_LOCAL
             : m_okay(false)
 #else
-            : m_okay(nesting_depth() < nesting_depth_limit())
+            : m_okay(nesting_depth() < detail::recursion_depth_limit())
 #endif
         {
 #ifndef JSON_NO_THREAD_LOCAL
@@ -1118,6 +1116,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         // provides the latter (e.g., ones without a matching allocator-aware
         // fill constructor)
         dst.m_data.m_value.array = create<array_t>();
+        // only now that the array exists may dst stop being a null value
+        dst.m_data.m_type = value_t::array;
         dst.m_data.m_value.array->resize(src_array.size());
 
         auto dst_it = dst.m_data.m_value.array->begin();
@@ -1127,6 +1127,27 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         }
     }
 
+    /// @brief create the object type from a range, preserving @a src_object's
+    /// comparator when the object type supports it
+    /// Enabled for object types that provide a key_comp() and a matching
+    /// range-plus-comparator constructor, such as std::map. Other object
+    /// types, such as nlohmann::ordered_map, fall back to the plain range
+    /// constructor and default-construct their comparator, just as they
+    /// always have (@ref detail::is_comparator_constructible_object_type).
+    template<typename Iterator, detail::enable_if_t<
+                 detail::is_comparator_constructible_object_type<object_t, Iterator>::value, int> = 0>
+    static object_t* create_object_with_comparator(const object_t& src_object, Iterator first, Iterator last)
+    {
+        return create<object_t>(first, last, src_object.key_comp());
+    }
+
+    template<typename Iterator, detail::enable_if_t<
+                 detail::negation<detail::is_comparator_constructible_object_type<object_t, Iterator>>::value, int> = 0>
+    static object_t* create_object_with_comparator(const object_t& /*src_object*/, Iterator first, Iterator last)
+    {
+        return create<object_t>(first, last);
+    }
+
     /// @brief create the copy of the object @a src in @a dst
     /// @note structured values are appended to @a worklist instead
     static void copy_object_level(const basic_json& src, basic_json& dst,
@@ -1144,8 +1165,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             scratch.emplace_back(element.first, basic_json());
         }
 
-        dst.m_data.m_value.object = create<object_t>(std::make_move_iterator(scratch.begin()),
+        dst.m_data.m_value.object = create_object_with_comparator(src_object,
+                                    std::make_move_iterator(scratch.begin()),
                                     std::make_move_iterator(scratch.end()));
+        // only now that the object exists may dst stop being a null value
+        dst.m_data.m_type = value_t::object;
         scratch.clear();
 
         // pair every value of the copy with its counterpart in the original;
@@ -1173,7 +1197,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     The values whose copy has not been created yet are kept on an explicit
     worklist rather than on the call stack. This is only reached for values
-    nested deeper than @ref nesting_depth_limit levels, which is why it copies
+    nested deeper than @ref detail::recursion_depth_limit levels, which is why it copies
     every container by hand instead of letting the container do it: the fast
     ways of doing so would descend into the elements and defeat the purpose.
     */
@@ -1208,9 +1232,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             src_value = next.first;
             dst_value = next.second;
             worklist.pop_back();
-
-            // the value stops being a null value exactly here
-            dst_value->m_data.m_type = src_value->m_data.m_type;
         }
     }
 
@@ -1239,7 +1260,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     Copying a container copies its elements, so a value nested deeply enough
     used to exhaust the call stack. The descent is bounded here: the first
-    @ref nesting_depth_limit levels are copied by the containers themselves, just
+    @ref detail::recursion_depth_limit levels are copied by the containers themselves, just
     as they always were, and anything below that is copied without the call
     stack by @ref copy_iteratively. Copying a value can therefore no longer
     exhaust the stack, however deeply it is nested, just like destroying one
@@ -1377,7 +1398,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /*!
     @brief compare @a lhs and @a rhs without descending into them
 
-    Reached once a comparison has descended @ref nesting_depth_limit levels, so
+    Reached once a comparison has descended @ref detail::recursion_depth_limit levels, so
     that comparing values cannot exhaust the call stack however deeply they are
     nested. The two values are walked in lockstep on an explicit stack and
     compared lexicographically, element by element in the order the containers
@@ -1507,7 +1528,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                         const auto found = (!Ordered && !detail::is_ordered_map<object_t>::value)
                                            ? rhs_object->find(current.lhs_object_it->first)
                                            : rhs_object->cend();
-                        if (found == rhs_object->cend())
+                        // the object's comparator may find an entry whose
+                        // key is only equivalent, not equal, to this one
+                        if (found == rhs_object->cend() || !(found->first == current.lhs_object_it->first))
                         {
                             return key_result;
                         }
@@ -1829,6 +1852,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             case value_t::number_integer:
             case value_t::number_unsigned:
             case value_t::string:
+            case value_t::binary:
             {
                 if (JSON_HEDLEY_UNLIKELY(!first.m_it.primitive_iterator.is_begin()
                                          || !last.m_it.primitive_iterator.is_end()))
@@ -1841,7 +1865,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             case value_t::null:
             case value_t::object:
             case value_t::array:
-            case value_t::binary:
             case value_t::discarded:
             default:
                 break;
@@ -2830,6 +2853,13 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             // fill up the array with null values if given idx is outside the range
             if (idx >= m_data.m_value.array->size())
             {
+                // idx + 1 would overflow size_type and wrap to 0, which would empty
+                // the array instead of growing it; reject such an idx the same way
+                // resize() rejects other indices that are too large to represent
+                if (JSON_HEDLEY_UNLIKELY(idx == (std::numeric_limits<size_type>::max)()))
+                {
+                    JSON_THROW(std::length_error(detail::concat("array index ", std::to_string(idx), " exceeds size_type")));
+                }
 #if JSON_DIAGNOSTICS
                 // remember array size & capacity before resizing
                 const auto old_size = m_data.m_value.array->size();
@@ -2975,6 +3005,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         string_t, typename std::decay<ValueType>::type >;
 
   public:
+    // an integer literal 0 would otherwise convert to a null const char* and from there to key_type
+    template<typename T, typename ValueType, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    ValueType value(T, ValueType&&) const = delete;
+
     /// @brief access specified object element with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
     template < class ValueType, detail::enable_if_t <
@@ -3409,6 +3443,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @name lookup
     /// @{
 
+    // an integer literal 0 would otherwise convert to a null const char* and from there to key_type
+    template<typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    iterator find(T) = delete;
+    template<typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    const_iterator find(T) const = delete;
+    template<typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    size_type count(T) const = delete;
+    template<typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
+    bool contains(T) const = delete;
+
     /// @brief find an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/find/
     iterator find(const typename object_t::key_type& key)
@@ -3833,6 +3877,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             case value_t::binary:
             {
                 m_data.m_value.binary->clear();
+                m_data.m_value.binary->clear_subtype();
                 break;
             }
 
@@ -4152,8 +4197,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
         }
 
+        // copy the values first: ilist may refer to elements of this array
+        array_t values;
+        detail::reserve_array(values, ilist.size(), detail::priority_tag<1> {});
+        for (const auto& element : ilist)
+        {
+            values.push_back(element.moved_or_copied());
+        }
+
         // insert to array and return iterator
-        return insert_iterator(pos, ilist.begin(), ilist.end());
+        return insert_iterator(pos, std::make_move_iterator(values.begin()), std::make_move_iterator(values.end()));
     }
 
     /// @brief inserts range of elements into object
@@ -4335,12 +4388,21 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         std::is_nothrow_move_constructible<value_t>::value&&
         std::is_nothrow_move_assignable<value_t>::value&&
         std::is_nothrow_move_constructible<json_value>::value&& // NOLINT(cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
-        std::is_nothrow_move_assignable<json_value>::value
+        std::is_nothrow_move_assignable<json_value>::value&&
+        std::is_nothrow_move_constructible<json_base_class_t>::value&&
+        std::is_nothrow_move_assignable<json_base_class_t>::value
     )
     {
         std::swap(m_data.m_type, other.m_data.m_type);
         std::swap(m_data.m_value, other.m_data.m_value);
 
+        // the custom base class travels with the value when it is copied or
+        // moved, so it is exchanged along with it
+        {
+            using std::swap;
+            swap(static_cast<json_base_class_t&>(*this), static_cast<json_base_class_t&>(other));
+        }
+
 #if JSON_DIAGNOSTIC_POSITIONS
         std::swap(start_position, other.start_position);
         std::swap(end_position, other.end_position);
@@ -4357,7 +4419,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         std::is_nothrow_move_constructible<value_t>::value&&
         std::is_nothrow_move_assignable<value_t>::value&&
         std::is_nothrow_move_constructible<json_value>::value&& // NOLINT(cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
-        std::is_nothrow_move_assignable<json_value>::value
+        std::is_nothrow_move_assignable<json_value>::value&&
+        std::is_nothrow_move_constructible<json_base_class_t>::value&&
+        std::is_nothrow_move_assignable<json_base_class_t>::value
     )
     {
         left.swap(right);
@@ -5050,7 +5114,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_gtgt/
     friend std::istream& operator>>(std::istream& i, basic_json& j)
     {
-        parser(detail::input_adapter(i)).parse(false, j);
+        // parse into a temporary so that j is left unchanged if parsing fails
+        basic_json result;
+        parser(detail::input_adapter(i)).parse(false, result);
+        j = std::move(result);
         return i;
     }
 #endif  // JSON_NO_IO
@@ -6150,12 +6217,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // the same time, determine whether every added key comes
                 // after every common key in target's order (a precondition
                 // for the fast path below, which only ever appends new keys
-                // at the very end): for an object_t whose iteration order is
-                // a pure function of the key set (e.g. the default std::map,
-                // which always iterates in sorted key order), the order
-                // check further below is always true and this whole
-                // mechanism is effectively a no-op; it only matters for a
-                // reorderable object_t such as the one backing `ordered_json`.
+                // at the very end). Both are only needed for an object_t that
+                // keeps its members in insertion order, such as the one
+                // backing `ordered_json`; for any other object_t, the fast
+                // path is always taken and they are not computed.
                 // patch ops for keys that were added (i.e., in target but not
                 // in source); built here so the fast path below can reuse
                 // them without a second source.find() per target key. Only
@@ -6179,15 +6244,32 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     }
                     else
                     {
-                        common_keys_target_order.push_back(it.key());
-                        if (seen_new_key)
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning(push )
+#pragma warning(disable : 4127) // ignore warning to replace if with if constexpr
+#endif
+                        if (detail::is_ordered_map<object_t>::value)
                         {
-                            new_keys_form_suffix = false;
+                            common_keys_target_order.push_back(it.key());
+                            if (seen_new_key)
+                            {
+                                new_keys_form_suffix = false;
+                            }
                         }
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning( pop )
+#endif
                     }
                 }
 
-                if (common_keys_source_order == common_keys_target_order && new_keys_form_suffix)
+                // Only an object type that keeps its members in insertion
+                // order, such as nlohmann::ordered_map, can need reordering:
+                // patch() appends a new member at the end of such an object.
+                // Any other object type places its members itself - std::map
+                // in key order, a hash map in an order its operator== ignores -
+                // so a member-by-member diff always reproduces target there.
+                if (!detail::is_ordered_map<object_t>::value
+                        || (common_keys_source_order == common_keys_target_order && new_keys_form_suffix))
                 {
                     // fast path: order of common keys already matches (or the
                     // object_t's iteration order does not depend on
@@ -6423,55 +6505,6 @@ std::string format_as(const NLOHMANN_BASIC_JSON_TPL& j)
     return j.dump();
 }
 
-inline namespace literals
-{
-inline namespace json_literals
-{
-
-/// @brief user-defined string literal for JSON values
-/// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json/
-JSON_HEDLEY_NON_NULL(1)
-#if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
-    inline nlohmann::json operator""_json(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json operator"" _json(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::parse(s, s + n);
-}
-
-#if defined(__cpp_char8_t)
-JSON_HEDLEY_NON_NULL(1)
-inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
-                                 reinterpret_cast<const char*>(s) + n);
-}
-#endif
-
-/// @brief user-defined string literal for JSON pointer
-/// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json_pointer/
-JSON_HEDLEY_NON_NULL(1)
-#if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
-    inline nlohmann::json::json_pointer operator""_json_pointer(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json::json_pointer operator"" _json_pointer(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::json_pointer(std::string(s, n));
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
-}
-#endif
-
-}  // namespace json_literals
-}  // namespace literals
 NLOHMANN_JSON_NAMESPACE_END
 
 ///////////////////////
@@ -6606,17 +6639,6 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 
 }  // namespace std
 
-#if JSON_USE_GLOBAL_UDLS
-    #if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
-        using nlohmann::literals::json_literals::operator""_json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator""_json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #else
-        // GCC 4.8 requires a space between "" and suffix
-        using nlohmann::literals::json_literals::operator"" _json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator"" _json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #endif
-#endif
-
 #include <nlohmann/detail/macro_unscope.hpp>
 
 // End of GCC diagnostic pragmas for C++ modules support
@@ -6624,4 +6646,13 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
     #pragma GCC diagnostic pop
 #endif
 
+// The user-defined string literals are in a separate header, because their
+// bodies instantiate the parser in every translation unit that includes them.
+// Define JSON_NO_AUTOMATIC_UDLS to include <nlohmann/json_literals.hpp> only
+// where needed.
+#ifndef JSON_NO_AUTOMATIC_UDLS
+    // NOLINTNEXTLINE(misc-header-include-cycle): json_literals.hpp includes this header
+    #include <nlohmann/json_literals.hpp>
+#endif
+
 #endif  // INCLUDE_NLOHMANN_JSON_HPP_

include/nlohmann/json_literals.hpp

@@ -0,0 +1,78 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#ifndef INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
+#define INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
+
+#include <cstddef> // size_t
+#include <string> // string
+
+// NOLINTNEXTLINE(misc-header-include-cycle): json.hpp includes this header at its end
+#include <nlohmann/json.hpp>
+
+// This header is included at the end of <nlohmann/json.hpp> unless
+// JSON_NO_AUTOMATIC_UDLS is defined, and can be included on its own after that.
+// Either way, the library's internal macros are no longer defined here (and the
+// amalgamation inlines macro_scope.hpp only once), so only standard and public
+// macros may be used below.
+
+// declares the literal operator for the given suffix; GCC 4.8 requires a space
+// between "" and the suffix, which newer compilers deprecate (CWG 2521)
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    #define NLOHMANN_JSON_LITERAL_OPERATOR(suffix) operator""##suffix
+#else
+    #define NLOHMANN_JSON_LITERAL_OPERATOR(suffix) operator"" suffix
+#endif
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+inline namespace literals
+{
+inline namespace json_literals
+{
+
+/// @brief user-defined string literal for JSON values
+/// @sa https://json.nlohmann.me/api/operator_literal_json/
+inline nlohmann::json NLOHMANN_JSON_LITERAL_OPERATOR(_json)(const char* s, std::size_t n)
+{
+    return nlohmann::json::parse(s, s + n);
+}
+
+#if defined(__cpp_char8_t)
+inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
+                                 reinterpret_cast<const char*>(s) + n);
+}
+#endif
+
+/// @brief user-defined string literal for JSON pointer
+/// @sa https://json.nlohmann.me/api/operator_literal_json_pointer/
+inline nlohmann::json::json_pointer NLOHMANN_JSON_LITERAL_OPERATOR(_json_pointer)(const char* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(s, n));
+}
+
+#if defined(__cpp_char8_t)
+inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
+}
+#endif
+
+}  // namespace json_literals
+}  // namespace literals
+NLOHMANN_JSON_NAMESPACE_END
+
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
+    using nlohmann::literals::json_literals::NLOHMANN_JSON_LITERAL_OPERATOR(_json); // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+    using nlohmann::literals::json_literals::NLOHMANN_JSON_LITERAL_OPERATOR(_json_pointer); //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+#endif
+
+#undef NLOHMANN_JSON_LITERAL_OPERATOR
+
+#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_

include/nlohmann/ordered_map.hpp

@@ -8,13 +8,15 @@
 
 #pragma once
 
+#include <algorithm> // max, min
 #include <functional> // equal_to, less
 #include <initializer_list> // initializer_list
 #include <iterator> // input_iterator_tag, iterator_traits
 #include <memory> // allocator
 #include <stdexcept> // for out_of_range
-#include <type_traits> // enable_if, is_convertible
-#include <utility> // pair
+#include <tuple> // forward_as_tuple
+#include <type_traits> // enable_if, integral_constant, is_convertible, is_nothrow_move_constructible
+#include <utility> // forward, move, pair, piecewise_construct
 #include <vector> // vector
 
 #include <nlohmann/detail/macro_scope.hpp>
@@ -79,7 +81,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::emplace_back(key, std::forward<T>(t));
+        append(key, std::forward<T>(t));
         return {std::prev(this->end()), true};
     }
 
@@ -94,7 +96,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::emplace_back(std::forward<KeyType>(key), std::forward<T>(t));
+        append(std::forward<KeyType>(key), std::forward<T>(t));
         return {std::prev(this->end()), true};
     }
 
@@ -368,7 +370,7 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
                 return {it, false};
             }
         }
-        Container::push_back(value);
+        append(value);
         return {--this->end(), true};
     }
 
@@ -386,6 +388,64 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
     }
 
 private:
+    /*!
+    @brief add an element whose key is not yet contained at the end
+
+    A std::vector copies all elements when it grows, because their const keys
+    make them not nothrow move constructible. For ordered_json, this is a deep
+    copy of every value. Where the strong exception guarantee can be kept, grow
+    the storage here instead, copying only the keys and moving the values.
+    */
+    template<typename... Args>
+    void append(Args&& ... args)
+    {
+        // evaluated here rather than at class scope, because T is still
+        // incomplete when basic_json instantiates its object_t
+        using move_values = std::integral_constant<bool, detail::conjunction<
+                detail::negation<std::is_nothrow_move_constructible<value_type>>,
+                std::is_copy_constructible<key_type>,
+                detail::is_default_constructible<mapped_type>,
+                std::is_nothrow_move_assignable<mapped_type>>::value>;
+        append_impl(move_values{}, std::forward<Args>(args)...);
+    }
+
+    template<typename... Args>
+    void append_impl(std::true_type /*unused*/, Args&& ... args)
+    {
+        if (this->size() < this->capacity())
+        {
+            Container::emplace_back(std::forward<Args>(args)...);
+            return;
+        }
+
+        // 1. May throw, but only changes tmp: copy the keys, value-initialize
+        //    the values, and add the new element. The arguments may refer to
+        //    elements of this container, so they are used before any value is
+        //    moved out of it.
+        Container tmp(this->get_allocator()); // equal allocators, so swap() is valid
+        tmp.reserve((std::min)(this->max_size(), (std::max)(size_type{1}, 2 * this->size())));
+        for (const auto& element : *this)
+        {
+            tmp.emplace_back(std::piecewise_construct, std::forward_as_tuple(element.first), std::forward_as_tuple());
+        }
+        tmp.emplace_back(std::forward<Args>(args)...);
+
+        // 2. Cannot throw: move the values over and adopt the new storage.
+        auto it = tmp.begin();
+        for (auto& element : *this)
+        {
+            it->second = std::move(element.second);
+            ++it;
+        }
+        Container::swap(tmp);
+    }
+
+    template<typename... Args>
+    void append_impl(std::false_type /*unused*/, Args&& ... args)
+    {
+        Container::emplace_back(std::forward<Args>(args)...);
+    }
+
     JSON_NO_UNIQUE_ADDRESS key_compare m_compare = key_compare();
 };
 

meson.build

@@ -15,6 +15,7 @@ nlohmann_json_multiple_headers = declare_dependency(
 if not meson.is_subproject()
 install_headers('single_include/nlohmann/json.hpp', subdir: 'nlohmann')
 install_headers('single_include/nlohmann/json_fwd.hpp', subdir: 'nlohmann')
+install_headers('single_include/nlohmann/json_literals.hpp', subdir: 'nlohmann')
 
 pkgc = import('pkgconfig')
 pkgc.generate(name: 'nlohmann_json',

single_include/nlohmann/json_literals.hpp

@@ -0,0 +1,78 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#ifndef INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
+#define INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
+
+#include <cstddef> // size_t
+#include <string> // string
+
+// NOLINTNEXTLINE(misc-header-include-cycle): json.hpp includes this header at its end
+#include <nlohmann/json.hpp>
+
+// This header is included at the end of <nlohmann/json.hpp> unless
+// JSON_NO_AUTOMATIC_UDLS is defined, and can be included on its own after that.
+// Either way, the library's internal macros are no longer defined here (and the
+// amalgamation inlines macro_scope.hpp only once), so only standard and public
+// macros may be used below.
+
+// declares the literal operator for the given suffix; GCC 4.8 requires a space
+// between "" and the suffix, which newer compilers deprecate (CWG 2521)
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    #define NLOHMANN_JSON_LITERAL_OPERATOR(suffix) operator""##suffix
+#else
+    #define NLOHMANN_JSON_LITERAL_OPERATOR(suffix) operator"" suffix
+#endif
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+inline namespace literals
+{
+inline namespace json_literals
+{
+
+/// @brief user-defined string literal for JSON values
+/// @sa https://json.nlohmann.me/api/operator_literal_json/
+inline nlohmann::json NLOHMANN_JSON_LITERAL_OPERATOR(_json)(const char* s, std::size_t n)
+{
+    return nlohmann::json::parse(s, s + n);
+}
+
+#if defined(__cpp_char8_t)
+inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
+                                 reinterpret_cast<const char*>(s) + n);
+}
+#endif
+
+/// @brief user-defined string literal for JSON pointer
+/// @sa https://json.nlohmann.me/api/operator_literal_json_pointer/
+inline nlohmann::json::json_pointer NLOHMANN_JSON_LITERAL_OPERATOR(_json_pointer)(const char* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(s, n));
+}
+
+#if defined(__cpp_char8_t)
+inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
+}
+#endif
+
+}  // namespace json_literals
+}  // namespace literals
+NLOHMANN_JSON_NAMESPACE_END
+
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
+    using nlohmann::literals::json_literals::NLOHMANN_JSON_LITERAL_OPERATOR(_json); // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+    using nlohmann::literals::json_literals::NLOHMANN_JSON_LITERAL_OPERATOR(_json_pointer); //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+#endif
+
+#undef NLOHMANN_JSON_LITERAL_OPERATOR
+
+#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_

src/modules/json.cppm

@@ -18,6 +18,7 @@ module;
 // See: https://github.com/nlohmann/json/issues/5103
 
 #include <nlohmann/json.hpp>
+#include <nlohmann/json_literals.hpp>
 
 export module nlohmann.json;
 

tests/benchmarks/src/benchmarks.cpp

@@ -119,6 +119,39 @@ BENCHMARK_CAPTURE(ParseIndented, canada / 4,       TEST_DATA_DIRECTORY "/nativej
 BENCHMARK_CAPTURE(ParseIndented, citm_catalog / 4, TEST_DATA_DIRECTORY "/nativejson-benchmark/citm_catalog.json", 4);
 BENCHMARK_CAPTURE(ParseIndented, twitter / 4,      TEST_DATA_DIRECTORY "/nativejson-benchmark/twitter.json",      4);
 
+//////////////////////////////////////////////////////////////////////////////
+// parse JSON from string into an ordered_json
+//
+// Same as ParseString above, but with nlohmann::ordered_json, whose objects
+// keep their members in a vector: the pair of rows shows what preserving the
+// insertion order costs.
+//////////////////////////////////////////////////////////////////////////////
+
+static void ParseStringOrdered(benchmark::State& state, const char* filename)
+{
+    std::ifstream f(filename);
+    std::string str((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
+
+    while (state.KeepRunning())
+    {
+        state.PauseTiming();
+        auto* j = new nlohmann::ordered_json();
+        state.ResumeTiming();
+
+        *j = nlohmann::ordered_json::parse(str);
+
+        state.PauseTiming();
+        delete j;
+        state.ResumeTiming();
+    }
+
+    state.SetBytesProcessed(state.iterations() * str.size());
+}
+BENCHMARK_CAPTURE(ParseStringOrdered, jeopardy,     TEST_DATA_DIRECTORY "/jeopardy/jeopardy.json");
+BENCHMARK_CAPTURE(ParseStringOrdered, canada,       TEST_DATA_DIRECTORY "/nativejson-benchmark/canada.json");
+BENCHMARK_CAPTURE(ParseStringOrdered, citm_catalog, TEST_DATA_DIRECTORY "/nativejson-benchmark/citm_catalog.json");
+BENCHMARK_CAPTURE(ParseStringOrdered, twitter,      TEST_DATA_DIRECTORY "/nativejson-benchmark/twitter.json");
+
 //////////////////////////////////////////////////////////////////////////////
 // serialize JSON
 //////////////////////////////////////////////////////////////////////////////

tests/src/unit-allocator.cpp

@@ -276,6 +276,133 @@ TEST_CASE("controlled bad_alloc")
     }
 }
 
+namespace
+{
+// counts every allocation made on behalf of a basic_json value (of its own
+// object_t/array_t/string_t/binary_t or of its own type), and can be told to
+// fail one of them: the n-th call to allocate() throws std::bad_alloc instead
+// of allocating, whichever type it is allocating for
+std::size_t alloc_call_count = 0;
+long fail_at_alloc_call = -1; // -1: never fail
+
+template<class T>
+struct nth_alloc_fails_allocator : std::allocator<T>
+{
+    using std::allocator<T>::allocator;
+
+    T* allocate(std::size_t n)
+    {
+        const auto index = alloc_call_count++;
+        if (fail_at_alloc_call >= 0 && index == static_cast<std::size_t>(fail_at_alloc_call))
+        {
+            throw std::bad_alloc();
+        }
+        return std::allocator<T>::allocate(n);
+    }
+
+    template <class U>
+    struct rebind
+    {
+        using other = nth_alloc_fails_allocator<U>;
+    };
+};
+
+// builds a value nested more than 128 levels deep - the bound the copy
+// constructor descends into before it continues without the call stack - and
+// checks that a copy survives any single allocation of it failing: every
+// attempt either throws std::bad_alloc, without crashing or leaving the
+// source altered, or completes the copy
+template<class BasicJsonType>
+void check_deep_copy_survives_failing_allocation(bool nest_objects)
+{
+    CAPTURE(nest_objects);
+
+    fail_at_alloc_call = -1;
+
+    // [[[ ... [1] ... ]]], or the same nesting with objects, 130 levels deep
+    BasicJsonType src = 1;
+    for (std::size_t i = 0; i < 130; ++i)
+    {
+        if (nest_objects)
+        {
+            BasicJsonType wrapper = BasicJsonType::object();
+            wrapper["a"] = std::move(src);
+            src = std::move(wrapper);
+        }
+        else
+        {
+            src = BasicJsonType::array({std::move(src)});
+        }
+    }
+
+    const std::string original_dump = src.dump();
+
+    // first measure how many allocations an unhindered copy takes
+    alloc_call_count = 0;
+    {
+        // NOLINTNEXTLINE(performance-unnecessary-copy-initialization): the copy is what is measured
+        const BasicJsonType measure(src);
+    }
+    const std::size_t total_allocations = alloc_call_count;
+    REQUIRE(total_allocations > 0);
+    REQUIRE(src.dump() == original_dump);
+
+    // let the 0th, 1st, 2nd, ... allocation of the copy fail in turn; every
+    // such copy must throw std::bad_alloc rather than crash, and the source
+    // must come out exactly as it went in
+    for (std::size_t n = 0; n < total_allocations; ++n)
+    {
+        CAPTURE(n);
+        alloc_call_count = 0;
+        fail_at_alloc_call = static_cast<long>(n);
+
+        CHECK_THROWS_AS(BasicJsonType(src), std::bad_alloc&);
+
+        fail_at_alloc_call = -1;
+        CHECK(src.dump() == original_dump);
+    }
+
+    // once no allocation is made to fail, the copy itself must succeed
+    fail_at_alloc_call = -1;
+    const BasicJsonType copy(src);
+    CHECK(copy.dump() == original_dump);
+    CHECK(src.dump() == original_dump);
+}
+} // namespace
+
+TEST_CASE("copy of a deeply nested value survives a failing allocation (#5640)")
+{
+    SECTION("std::map-backed object_t")
+    {
+        using bad_alloc_json = nlohmann::basic_json<std::map,
+              std::vector,
+              std::string,
+              bool,
+              std::int64_t,
+              std::uint64_t,
+              double,
+              nth_alloc_fails_allocator>;
+
+        check_deep_copy_survives_failing_allocation<bad_alloc_json>(false);
+        check_deep_copy_survives_failing_allocation<bad_alloc_json>(true);
+    }
+
+    SECTION("ordered_map-backed object_t")
+    {
+        using bad_alloc_ordered_json = nlohmann::basic_json<nlohmann::ordered_map,
+              std::vector,
+              std::string,
+              bool,
+              std::int64_t,
+              std::uint64_t,
+              double,
+              nth_alloc_fails_allocator>;
+
+        check_deep_copy_survives_failing_allocation<bad_alloc_ordered_json>(false);
+        check_deep_copy_survives_failing_allocation<bad_alloc_ordered_json>(true);
+    }
+}
+
 namespace
 {
 // counts the allocations of pairs with a non-const first member: the object

tests/src/unit-alt-string.cpp

@@ -174,6 +174,15 @@ bool operator<(const char* op1, const alt_string& op2) noexcept
     return op1 < op2.str_impl;
 }
 
+enum class alt_color { red, green };
+
+// NOLINTNEXTLINE(misc-use-internal-linkage,misc-const-correctness,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) - false positive
+NLOHMANN_JSON_SERIALIZE_ENUM_STRICT(alt_color,
+{
+    {alt_color::red, "red"},
+    {alt_color::green, "green"},
+})
+
 TEST_CASE("alternative string type")
 {
     SECTION("binary formats")
@@ -343,6 +352,41 @@ TEST_CASE("alternative string type")
         CHECK(j2.flatten().unflatten() == j2);
     }
 
+    SECTION("contains(json_pointer)")
+    {
+        // contains(json_pointer) must compile and work with a string_t that has
+        // no c_str() and no comparison with const char* (see #5666)
+        auto j = alt_json::parse(R"({"foo": ["bar", "baz"]})");
+
+        // present: object key and array indices
+        CHECK(j.contains(alt_json::json_pointer("/foo")));
+        CHECK(j.contains(alt_json::json_pointer("/foo/0")));
+        CHECK(j.contains(alt_json::json_pointer("/foo/1")));
+
+        // missing: absent object key and out-of-range array index
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/bar")));
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/2")));
+
+        // "-" always fails the range check
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/-")));
+
+        // an array index must not have a leading zero
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/01")));
+
+        // a reference token that is not a number
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/bar")));
+    }
+
+    SECTION("operator/(std::size_t)")
+    {
+        // json_pointer::operator/=(std::size_t) must compile without string_t
+        // being constructible from std::string (see #5666)
+        auto j = alt_json::parse(R"({"foo": ["bar", "baz"]})");
+
+        CHECK(j.at(alt_json::json_pointer("/foo") / std::size_t(0)) == j["foo"][0]);
+        CHECK(j.at(alt_json::json_pointer("/foo") / std::size_t(1)) == j["foo"][1]);
+    }
+
     SECTION("patch")
     {
         alt_json const patch1 = alt_json::parse(R"([{ "op": "add", "path": "/a/b", "value": [ "foo", "bar" ] }])");
@@ -374,4 +418,19 @@ TEST_CASE("alternative string type")
         const auto j2 = j.flatten();
         CHECK(j2.dump() == R"({"/foo/0":"bar","/foo/1":"baz"})");
     }
+
+    SECTION("strict enum")
+    {
+        // regression test for #5667: NLOHMANN_JSON_SERIALIZE_ENUM_STRICT's from_json
+        // built its exception message with "..." + j.dump(), which does not compile
+        // when j.dump() returns a custom string_t (here alt_string) instead of
+        // std::string
+        alt_json doc;
+        doc = "red";
+        CHECK(doc.get<alt_color>() == alt_color::red);
+
+        alt_json _;
+        doc = "blue";
+        CHECK_THROWS_WITH_AS(_ = doc.get<alt_color>(), "[json.exception.out_of_range.410] enum value out of range for alt_color: \"blue\"", alt_json::out_of_range&);
+    }
 }

tests/src/unit-bson.cpp

@@ -797,7 +797,11 @@ TEST_CASE("regression test - BSON binary subtype rejects a value that doesn't fi
     CHECK(json::from_bson(json::to_bson(doc255))["b"].get_binary().subtype() == 255);
 
     CHECK_THROWS_AS(json::to_bson(json{{"b", json::binary({1, 2}, 256)}}), json::out_of_range);
-    CHECK_THROWS_WITH_AS(json::to_bson(json{{"b", json::binary({1, 2}, 300)}}), "[json.exception.out_of_range.415] subtype 300 is too large for the BSON binary subtype (max 255)", json::out_of_range);
+#if JSON_DIAGNOSTICS
+    CHECK_THROWS_WITH_AS(json::to_bson(json {{"b", json::binary({1, 2}, 300)}}), "[json.exception.out_of_range.415] (/b) subtype 300 is too large for the BSON binary subtype (max 255)", json::out_of_range);
+#else
+    CHECK_THROWS_WITH_AS(json::to_bson(json {{"b", json::binary({1, 2}, 300)}}), "[json.exception.out_of_range.415] subtype 300 is too large for the BSON binary subtype (max 255)", json::out_of_range);
+#endif
 }
 
 TEST_CASE("BSON input/output_adapters")
@@ -1805,6 +1809,21 @@ value = depth % 2 == 0 ? json{{"a", std::move(value)}, {"b", {1, "x"}}} :
         CHECK(output.empty());
     }
 
+    SECTION("a binary subtype that doesn't fit a byte is rejected before anything is written (#5675)")
+    {
+        // the offending value is nested, so this also covers that the check
+        // is not limited to a directly written value's own document
+        json const j = {{"a", {{"b", json::binary({1, 2}, 300)}}}};
+
+        std::vector<std::uint8_t> vector_output;
+        CHECK_THROWS_AS(json::to_bson(j, vector_output), json::out_of_range&);
+        CHECK(vector_output.empty());
+
+        std::string string_output;
+        CHECK_THROWS_AS(json::to_bson(j, string_output), json::out_of_range&);
+        CHECK(string_output.empty());
+    }
+
     SECTION("values nested too deeply for the call stack (#5392)")
     {
         // serializing recursed once per nesting level, and computed every

tests/src/unit-cbor.cpp

@@ -1830,10 +1830,51 @@ TEST_CASE("CBOR")
         SECTION("invalid string in map")
         {
             json _;
-            CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xa1, 0xff, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xa1, 0xff, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found a break stop code; last byte: 0xFF", json::parse_error&);
             CHECK(json::from_cbor(std::vector<uint8_t>({0xa1, 0xff, 0x01}), true, false).is_discarded());
         }
 
+        SECTION("non-string key (see #2766 and #3381)")
+        {
+            // only text strings map to JSON object keys; any other key is
+            // rejected with a message naming its type
+            const std::vector<std::pair<std::vector<std::uint8_t>, std::string>> cases =
+            {
+                {{0xA1, 0x01, 0x01}, "an unsigned integer; last byte: 0x01"},
+                {{0xA1, 0x20, 0x01}, "a negative integer; last byte: 0x20"},
+                {{0xA1, 0x41, 0x61, 0x01}, "a byte string; last byte: 0x41"},
+                {{0xA1, 0x80, 0x01}, "an array; last byte: 0x80"},
+                {{0xA1, 0xA0, 0x01}, "a map; last byte: 0xA0"},
+                {{0xA1, 0xC0, 0x61, 0x61, 0x01}, "a tag; last byte: 0xC0"},
+                {{0xA1, 0xF4, 0x01}, "a boolean; last byte: 0xF4"},
+                {{0xA1, 0xF5, 0x01}, "a boolean; last byte: 0xF5"},
+                {{0xA1, 0xF6, 0x01}, "null; last byte: 0xF6"},
+                {{0xA1, 0xF7, 0x01}, "undefined; last byte: 0xF7"},
+                {{0xA1, 0xF9, 0x3C, 0x00, 0x01}, "a floating-point number; last byte: 0xF9"},
+                {{0xA1, 0xFA, 0x3F, 0x80, 0x00, 0x00, 0x01}, "a floating-point number; last byte: 0xFA"},
+                {{0xA1, 0xFB, 0x3F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01}, "a floating-point number; last byte: 0xFB"},
+                {{0xA1, 0xE0, 0x01}, "a simple value; last byte: 0xE0"},
+                {{0xA1, 0xF8, 0x20, 0x01}, "a simple value; last byte: 0xF8"},
+                // indefinite-length map
+                {{0xBF, 0x01, 0x01, 0xFF}, "an unsigned integer; last byte: 0x01"},
+            };
+
+            for (const auto& c : cases)
+            {
+                CAPTURE(c.first)
+                const std::string expected = "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found " + c.second;
+                json _;
+                CHECK_THROWS_WITH_AS(_ = json::from_cbor(c.first), expected.c_str(), json::parse_error&);
+                CHECK(json::from_cbor(c.first, true, false).is_discarded());
+            }
+
+            // a key of major type 3 with a reserved length is still reported as
+            // a malformed string, and a missing key as the end of input
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xA1})), "[json.exception.parse_error.110] parse error at byte 2: syntax error while parsing CBOR string: unexpected end of input", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xA1, 0x7C, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x7C", json::parse_error&);
+        }
+
         SECTION("invalid UTF-8 in string (see #5529)")
         {
             // a two-character text string (major type 3) whose bytes are not
@@ -2284,7 +2325,7 @@ TEST_CASE("CBOR indefinite-length strings do not recurse per chunk")
     SECTION("a break marker outside an indefinite-length string is not a string")
     {
         // 0xFF only closes a string that was opened; on its own it is not one
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xA1, 0xFF, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xA1, 0xFF, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found a break stop code; last byte: 0xFF", json::parse_error&);
     }
 }
 

tests/src/unit-class_lexer.cpp

@@ -12,10 +12,14 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
+#include <array> // array
 #include <cfloat> // FLT_EVAL_METHOD
+#include <cstdint> // uint32_t, uint64_t
 #include <cstdlib> // strtod
+#include <cstring> // memcpy
 #include <sstream> // stringstream
 #include <string> // string
+#include <utility> // pair
 #include <vector> // vector
 
 namespace
@@ -666,7 +670,7 @@ TEST_CASE("parse_float_fast declines what it cannot convert exactly")
     // always safe: the caller then falls back to a slower, exact conversion.
     const auto fast = [](const std::string & s, double & out)
     {
-        return nlohmann::detail::parse_float_fast(s.data(), s.data() + s.size(), '.', out);
+        return nlohmann::detail::parse_float_fast(s.data(), s.data() + s.size(), out);
     };
     double out = 0;
 
@@ -700,3 +704,614 @@ TEST_CASE("parse_float_fast declines what it cannot convert exactly")
     CHECK_FALSE(fast("1e23", out));
     CHECK_FALSE(fast("1e-23", out));
 }
+
+namespace
+{
+// arbitrary-precision unsigned integers, just enough to recompute the table of
+// powers of five (little-endian 32-bit limbs)
+using big_uint = std::vector<std::uint32_t>;
+
+void big_trim(big_uint& a)
+{
+    while (!a.empty() && a.back() == 0)
+    {
+        a.pop_back();
+    }
+}
+
+big_uint big_from(std::uint64_t high, std::uint64_t low)
+{
+    big_uint a = {static_cast<std::uint32_t>(low), static_cast<std::uint32_t>(low >> 32u),
+                  static_cast<std::uint32_t>(high), static_cast<std::uint32_t>(high >> 32u)
+                 };
+    big_trim(a);
+    return a;
+}
+
+big_uint big_mul(const big_uint& a, const big_uint& b)
+{
+    big_uint r(a.size() + b.size(), 0);
+    for (std::size_t i = 0; i < a.size(); ++i)
+    {
+        std::uint64_t carry = 0;
+        for (std::size_t j = 0; j < b.size(); ++j)
+        {
+            const std::uint64_t t = (static_cast<std::uint64_t>(a[i]) * b[j]) + r[i + j] + carry;
+            r[i + j] = static_cast<std::uint32_t>(t);
+            carry = t >> 32u;
+        }
+        r[i + b.size()] = static_cast<std::uint32_t>(carry);
+    }
+    big_trim(r);
+    return r;
+}
+
+big_uint big_shl(const big_uint& a, std::size_t s)
+{
+    big_uint r(s / 32, 0);
+    std::uint32_t carry = 0;
+    for (const std::uint32_t x : a)
+    {
+        const std::uint64_t t = static_cast<std::uint64_t>(x) << (s % 32);
+        r.push_back(static_cast<std::uint32_t>(t) | carry);
+        carry = static_cast<std::uint32_t>(t >> 32u);
+    }
+    r.push_back(carry);
+    big_trim(r);
+    return r;
+}
+
+// a + 1 (add) or a - 1 (!add, a > 0)
+big_uint big_step(big_uint a, bool add)
+{
+    for (auto& x : a)
+    {
+        const std::uint32_t old = x;
+        x = add ? x + 1 : x - 1;
+        if ((add && x > old) || (!add && x < old))
+        {
+            break;
+        }
+    }
+    if (add && (a.empty() || a.back() == 0))
+    {
+        a.push_back(1);
+    }
+    big_trim(a);
+    return a;
+}
+
+bool big_less_equal(const big_uint& a, const big_uint& b)
+{
+    if (a.size() != b.size())
+    {
+        return a.size() < b.size();
+    }
+    for (std::size_t i = a.size(); i-- > 0;)
+    {
+        if (a[i] != b[i])
+        {
+            return a[i] < b[i];
+        }
+    }
+    return true;
+}
+
+std::size_t big_bit_length(const big_uint& a)
+{
+    std::size_t n = a.size() * 32;
+    for (std::uint32_t top = a.back(); (top & 0x80000000u) == 0; top <<= 1u)
+    {
+        --n;
+    }
+    return n;
+}
+
+std::uint64_t bits_of(double d)
+{
+    std::uint64_t b = 0;
+    std::memcpy(&b, &d, sizeof(b));
+    return b;
+}
+
+bool eisel_lemire(const std::string& s, double& out)
+{
+    return nlohmann::detail::parse_float_eisel_lemire(s.data(), s.data() + s.size(), out);
+}
+
+// significant digits of a token, without trailing zeros
+std::size_t significant_digits(const std::string& s)
+{
+    std::string digits;
+    for (const char c : s)
+    {
+        if (c == 'e' || c == 'E')
+        {
+            break;
+        }
+        if (c >= '0' && c <= '9' && !(digits.empty() && c == '0'))
+        {
+            digits += c;
+        }
+    }
+    while (!digits.empty() && digits.back() == '0')
+    {
+        digits.pop_back();
+    }
+    return digits.size();
+}
+} // namespace
+
+TEST_CASE("Eisel-Lemire float conversion")
+{
+    SECTION("the table of powers of five")
+    {
+        // Recompute every entry the way fast_float's table_generation.py
+        // defines it, using only multiplications and comparisons: for q >= 0
+        // the most significant 128 bits of 5^q; for q < 0 floor(2^b / 5^-q) + 1
+        // for b = z + 127 (q >= -27), or that value for b = 2z + 128 cut to
+        // its most significant 128 bits (q < -27), where z is the bit length
+        // of 5^-q.
+        const auto& table = nlohmann::detail::pow5_128();
+        big_uint power5 = {1};
+        for (std::int64_t q = 0; q <= nlohmann::detail::pow5_128_largest_power; ++q)
+        {
+            const auto index = static_cast<std::size_t>(2 * (q - nlohmann::detail::pow5_128_smallest_power));
+            const big_uint entry = big_from(table[index], table[index + 1]);
+            const std::size_t bits = big_bit_length(power5);
+            if (bits <= 128)
+            {
+                CHECK(entry == big_shl(power5, 128 - bits));
+            }
+            else
+            {
+                // floor(5^q / 2^(bits - 128))
+                CHECK(big_less_equal(big_shl(entry, bits - 128), power5));
+                CHECK_FALSE(big_less_equal(big_shl(big_step(entry, true), bits - 128), power5));
+            }
+            power5 = big_mul(power5, {5});
+        }
+
+        power5 = {5};
+        for (std::int64_t q = -1; q >= nlohmann::detail::pow5_128_smallest_power; --q)
+        {
+            const auto index = static_cast<std::size_t>(2 * (q - nlohmann::detail::pow5_128_smallest_power));
+            const big_uint entry = big_from(table[index], table[index + 1]);
+            CHECK(big_bit_length(entry) == 128);
+            const std::size_t z = big_bit_length(power5);
+            const big_uint two_b = big_shl({1}, q >= -27 ? z + 127 : (2 * z) + 128);
+            // c = floor(2^b / p) + 1, stored as floor(c / 2^s):
+            // (entry * 2^s - 1) * p <= 2^b < ((entry + 1) * 2^s - 1) * p
+            const std::size_t s = q >= -27 ? 0 : z + 1;
+            CHECK(big_less_equal(big_mul(big_step(big_shl(entry, s), false), power5), two_b));
+            CHECK_FALSE(big_less_equal(big_mul(big_step(big_shl(big_step(entry, true), s), false), power5), two_b));
+            power5 = big_mul(power5, {5});
+        }
+    }
+
+    SECTION("128-bit products and leading zeros")
+    {
+        // whichever implementation the compiler gets (with or without a
+        // 128-bit integer type or a builtin)
+        std::uint64_t state = 42;
+        for (int i = 0; i < 10000; ++i)
+        {
+            state ^= state << 13u;
+            state ^= state >> 7u;
+            state ^= state << 17u;
+            const std::uint64_t a = state;
+            const std::uint64_t b = (state * 0x9E3779B97F4A7C15u) >> (i % 64);
+            const auto product = nlohmann::detail::full_multiplication(a, b);
+            CHECK(big_from(product.high, product.low) == big_mul(big_from(0, a), big_from(0, b)));
+
+            const int k = i % 64;
+            const std::uint64_t x = (std::uint64_t{1} << k) | (a & ((std::uint64_t{1} << k) - 1));
+            CHECK(nlohmann::detail::count_leading_zeros(x) == 63 - k);
+        }
+    }
+
+    SECTION("known values")
+    {
+        // Generated with Python, whose float() is correctly rounded:
+        //   cases = [<hard cases>, 2**53 + 2k + 1, 2**54 + 4k + 2, and exact midpoints
+        //            between neighbouring doubles, also 1e-60 above and below them]
+        //   print('{"%s", 0x%016xu},' % (s, struct.unpack('<Q', struct.pack('<d', float(s)))[0]))
+        const std::vector<std::pair<std::string, std::uint64_t>> known =
+        {
+            {"0", 0x0000000000000000u},
+            {"-0", 0x8000000000000000u},
+            {"0.0", 0x0000000000000000u},
+            {"-0.0", 0x8000000000000000u},
+            {"0e5", 0x0000000000000000u},
+            {"0.000e-9", 0x0000000000000000u},
+            {"1", 0x3ff0000000000000u},
+            {"-1", 0xbff0000000000000u},
+            {"0.1", 0x3fb999999999999au},
+            {"0.3", 0x3fd3333333333333u},
+            {"1.5", 0x3ff8000000000000u},
+            {"-2.5e-3", 0xbf647ae147ae147bu},
+            {"1e23", 0x44b52d02c7e14af6u},
+            {"1e22", 0x4480f0cf064dd592u},
+            {"8.98846567431158e307", 0x7fe0000000000000u},
+            {"2.2250738585072011e-308", 0x000fffffffffffffu},
+            {"2.2250738585072012e-308", 0x0010000000000000u},
+            {"2.2250738585072014e-308", 0x0010000000000000u},
+            {"4.9406564584124654e-324", 0x0000000000000001u},
+            {"2.4703282292062327e-324", 0x0000000000000000u},
+            {"2.4703282292062328e-324", 0x0000000000000001u},
+            {"1e-324", 0x0000000000000000u},
+            {"3e-324", 0x0000000000000001u},
+            {"1.7976931348623157e308", 0x7fefffffffffffffu},
+            {"1.7976931348623158e308", 0x7fefffffffffffffu},
+            {"1.7976931348623159e308", 0x7ff0000000000000u},
+            {"1e308", 0x7fe1ccf385ebc8a0u},
+            {"1e309", 0x7ff0000000000000u},
+            {"-1e400", 0xfff0000000000000u},
+            {"1e-400", 0x0000000000000000u},
+            {"9007199254740991", 0x433fffffffffffffu},
+            {"9007199254740992", 0x4340000000000000u},
+            {"9007199254740993", 0x4340000000000000u},
+            {"9007199254740995", 0x4340000000000002u},
+            {"18014398509481986", 0x4350000000000000u},
+            {"18014398509481990", 0x4350000000000002u},
+            {"7.2057594037927933e16", 0x4370000000000000u},
+            {"123456789012345678901234567890", 0x45f8ee90ff6c373eu},
+            {"1.000000000000000111", 0x3ff0000000000000u},
+            {"1.0000000000000001110223", 0x3ff0000000000000u},
+            {"1.00000000000000011102230246251565404236316680908203125", 0x3ff0000000000000u},
+            {"1.00000000000000011102230246251565404236316680908203126", 0x3ff0000000000001u},
+            {"0.00000000000000000000000000000000000000000000000000000000000001", 0x3310747ddddf22a8u},
+            {"100000000000000000000000000000000000000000000", 0x4911efc659cf7d4cu},
+            {"1234567890123456789", 0x43b12210f47de981u},
+            {"12345678901234567890", 0x43e56a95319d63e1u},
+            {"1234567890123456789.5", 0x43b12210f47de981u},
+            {"0.1234567890123456789012345", 0x3fbf9add3746f65fu},
+            {"4.4501477170144023e-308", 0x001fffffffffffffu},
+            {"2.4406961166466664e-309", 0x0001c14ae5310a48u},
+            {"5e-324", 0x0000000000000001u},
+            {"1.0e-307", 0x0031fa182c40c60du},
+            {"179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368", 0x7fefffffffffffffu},
+            {"4.9e-324", 0x0000000000000001u},
+            {"9007199254740993", 0x4340000000000000u},
+            {"18014398509481986", 0x4350000000000000u},
+            {"9007199254740995", 0x4340000000000002u},
+            {"18014398509481990", 0x4350000000000002u},
+            {"9007199254740997", 0x4340000000000002u},
+            {"18014398509481994", 0x4350000000000002u},
+            {"9007199254740999", 0x4340000000000004u},
+            {"18014398509481998", 0x4350000000000004u},
+            {"9007199254741001", 0x4340000000000004u},
+            {"18014398509482002", 0x4350000000000004u},
+            {"9007199254741003", 0x4340000000000006u},
+            {"18014398509482006", 0x4350000000000006u},
+            {"9007199254741005", 0x4340000000000006u},
+            {"18014398509482010", 0x4350000000000006u},
+            {"9007199254741007", 0x4340000000000008u},
+            {"18014398509482014", 0x4350000000000008u},
+            {"9007199254741009", 0x4340000000000008u},
+            {"18014398509482018", 0x4350000000000008u},
+            {"9007199254741011", 0x434000000000000au},
+            {"18014398509482022", 0x435000000000000au},
+            {"9007199254741013", 0x434000000000000au},
+            {"18014398509482026", 0x435000000000000au},
+            {"9007199254741015", 0x434000000000000cu},
+            {"18014398509482030", 0x435000000000000cu},
+            {"9007199254741017", 0x434000000000000cu},
+            {"18014398509482034", 0x435000000000000cu},
+            {"9007199254741019", 0x434000000000000eu},
+            {"18014398509482038", 0x435000000000000eu},
+            {"9007199254741021", 0x434000000000000eu},
+            {"18014398509482042", 0x435000000000000eu},
+            {"9007199254741023", 0x4340000000000010u},
+            {"18014398509482046", 0x4350000000000010u},
+            {"9007199254741025", 0x4340000000000010u},
+            {"18014398509482050", 0x4350000000000010u},
+            {"9007199254741027", 0x4340000000000012u},
+            {"18014398509482054", 0x4350000000000012u},
+            {"9007199254741029", 0x4340000000000012u},
+            {"18014398509482058", 0x4350000000000012u},
+            {"9007199254741031", 0x4340000000000014u},
+            {"18014398509482062", 0x4350000000000014u},
+            {"9007199254741033", 0x4340000000000014u},
+            {"18014398509482066", 0x4350000000000014u},
+            {"9007199254741035", 0x4340000000000016u},
+            {"18014398509482070", 0x4350000000000016u},
+            {"9007199254741037", 0x4340000000000016u},
+            {"18014398509482074", 0x4350000000000016u},
+            {"9007199254741039", 0x4340000000000018u},
+            {"18014398509482078", 0x4350000000000018u},
+            {"9007199254741041", 0x4340000000000018u},
+            {"18014398509482082", 0x4350000000000018u},
+            {"9007199254741043", 0x434000000000001au},
+            {"18014398509482086", 0x435000000000001au},
+            {"9007199254741045", 0x434000000000001au},
+            {"18014398509482090", 0x435000000000001au},
+            {"9007199254741047", 0x434000000000001cu},
+            {"18014398509482094", 0x435000000000001cu},
+            {"9007199254741049", 0x434000000000001cu},
+            {"18014398509482098", 0x435000000000001cu},
+            {"9007199254741051", 0x434000000000001eu},
+            {"18014398509482102", 0x435000000000001eu},
+            {"9007199254741053", 0x434000000000001eu},
+            {"18014398509482106", 0x435000000000001eu},
+            {"9007199254741055", 0x4340000000000020u},
+            {"18014398509482110", 0x4350000000000020u},
+            {"9007199254741057", 0x4340000000000020u},
+            {"18014398509482114", 0x4350000000000020u},
+            {"9007199254741059", 0x4340000000000022u},
+            {"18014398509482118", 0x4350000000000022u},
+            {"9007199254741061", 0x4340000000000022u},
+            {"18014398509482122", 0x4350000000000022u},
+            {"9007199254741063", 0x4340000000000024u},
+            {"18014398509482126", 0x4350000000000024u},
+            {"9007199254741065", 0x4340000000000024u},
+            {"18014398509482130", 0x4350000000000024u},
+            {"9007199254741067", 0x4340000000000026u},
+            {"18014398509482134", 0x4350000000000026u},
+            {"9007199254741069", 0x4340000000000026u},
+            {"18014398509482138", 0x4350000000000026u},
+            {"9007199254741071", 0x4340000000000028u},
+            {"18014398509482142", 0x4350000000000028u},
+            {"0.00000000000000000142055942108419951085063380808124102279024543292671443374397544090470546507276594638824462890625", 0x3c3a3466f662d406u},
+            {"0.000000000000000001420559421084199510850633808081241022790245432926714433743975440904705465072765946388244628906251", 0x3c3a3466f662d407u},
+            {"0.00000000000000000142055942108419951085063380808124102279024543292671443374397444090470546507276594638824462890625", 0x3c3a3466f662d406u},
+            {"8656.5250079159513916238211095333099365234375", 0x40c0e84333759a94u},
+            {"8656.52500791595139162382110953330993652343751", 0x40c0e84333759a94u},
+            {"8656.525007915951391623821109533309936523437499999999999999999", 0x40c0e84333759a93u},
+            {"13.07696731650454946560557800694368779659271240234375", 0x402a276842967ef0u},
+            {"13.076967316504549465605578006943687796592712402343751", 0x402a276842967ef0u},
+            {"13.07696731650454946560557800694368779659271240234374999999999", 0x402a276842967eefu},
+            {"74708253715391928", 0x437096ac2cc7ee5cu},
+            {"747082537153919281", 0x43a4bc5737f9e9f2u},
+            {"74708253715391927.99999999999999999999999999999999999999999999", 0x437096ac2cc7ee5bu},
+            {"1809802988.27203977108001708984375", 0x41daf7d9bb11691au},
+            {"1809802988.272039771080017089843751", 0x41daf7d9bb11691au},
+            {"1809802988.272039771080017089843749999999999999999999999999999", 0x41daf7d9bb116919u},
+            {"51.390809684186766759239617385901510715484619140625", 0x4049b2060d3e4568u},
+            {"51.3908096841867667592396173859015107154846191406251", 0x4049b2060d3e4569u},
+            {"51.39080968418676675923961738590151071548461914062499999999999", 0x4049b2060d3e4568u},
+            {"9999807412.59738445281982421875", 0x4202a0479da4c772u},
+            {"9999807412.597384452819824218751", 0x4202a0479da4c772u},
+            {"9999807412.597384452819824218749999999999999999999999999999999", 0x4202a0479da4c771u},
+            {"0.00000000023260971767101600534534272272645127367651785021962496102787554264068603515625", 0x3deff83a135dec10u},
+            {"0.000000000232609717671016005345342722726451273676517850219624961027875542640686035156251", 0x3deff83a135dec11u},
+            {"0.00000000023260971767101600534534272272645127367651785021962496102787544264068603515625", 0x3deff83a135dec10u},
+            {"0.000000000497610482021202508216234789619066523902457532813059515319764614105224609375", 0x3e01190730d1ec48u},
+            {"0.0000000004976104820212025082162347896190665239024575328130595153197646141052246093751", 0x3e01190730d1ec48u},
+            {"0.000000000497610482021202508216234789619066523902457532813059515319764514105224609375", 0x3e01190730d1ec47u},
+            {"0.0000000000291336422596533830691676779231223432149733287843673679162748157978057861328125", 0x3dc004321559736eu},
+            {"0.00000000002913364225965338306916767792312234321497332878436736791627481579780578613281251", 0x3dc004321559736fu},
+            {"0.0000000000291336422596533830691676779231223432149733287843673679162748057978057861328125", 0x3dc004321559736eu},
+            {"0.000000000000000039237155154865396441907405399546892080260012902422940561653064150959835387766361236572265625", 0x3c869e61cfa3b8a4u},
+            {"0.0000000000000000392371551548653964419074053995468920802600129024229405616530641509598353877663612365722656251", 0x3c869e61cfa3b8a5u},
+            {"0.000000000000000039237155154865396441907405399546892080260012902422940561653054150959835387766361236572265625", 0x3c869e61cfa3b8a4u},
+            {"0.00000000000000006496592863767266414092845207857846208631635335985395063307379359685000963509082794189453125", 0x3c92b9a3b219ee84u},
+            {"0.000000000000000064965928637672664140928452078578462086316353359853950633073793596850009635090827941894531251", 0x3c92b9a3b219ee85u},
+            {"0.00000000000000006496592863767266414092845207857846208631635335985395063307378359685000963509082794189453125", 0x3c92b9a3b219ee84u},
+            {"0.0000000000448169607439179753541822628688597626549217078917308754171244800090789794921875", 0x3dc8a36d2e8094dau},
+            {"0.00000000004481696074391797535418226286885976265492170789173087541712448000907897949218751", 0x3dc8a36d2e8094dau},
+            {"0.0000000000448169607439179753541822628688597626549217078917308754171244700090789794921875", 0x3dc8a36d2e8094d9u},
+            {"1800873890234250.875", 0x4319978a820cfe2cu},
+            {"1800873890234250.8751", 0x4319978a820cfe2cu},
+            {"1800873890234250.874999999999999999999999999999999999999999999", 0x4319978a820cfe2bu},
+            {"0.000023941132739153309216405436654628857695570331998169422149658203125", 0x3ef91aa61d42e0e0u},
+            {"0.0000239411327391533092164054366546288576955703319981694221496582031251", 0x3ef91aa61d42e0e1u},
+            {"0.000023941132739153309216405436654628857695570331998169422149658193125", 0x3ef91aa61d42e0e0u},
+            {"8339818978785937.5", 0x433da1056bb8ba92u},
+            {"8339818978785937.51", 0x433da1056bb8ba92u},
+            {"8339818978785937.499999999999999999999999999999999999999999999", 0x433da1056bb8ba91u},
+            {"283649145986385328", 0x438f7dcb29dae42eu},
+            {"2836491459863853281", 0x43c3ae9efa28ce9cu},
+            {"283649145986385327.9999999999999999999999999999999999999999999", 0x438f7dcb29dae42du},
+            {"0.0000000000000000004203729478287971874304476341685497759528753070014375965192388040492232903488911688327789306640625", 0x3c1f049ed78cb8a2u},
+            {"0.00000000000000000042037294782879718743044763416854977595287530700143759651923880404922329034889116883277893066406251", 0x3c1f049ed78cb8a3u},
+            {"0.0000000000000000004203729478287971874304476341685497759528753070014375965192387040492232903488911688327789306640625", 0x3c1f049ed78cb8a2u},
+            {"340031.78635183119331486523151397705078125", 0x4114c0ff25396a18u},
+            {"340031.786351831193314865231513977050781251", 0x4114c0ff25396a19u},
+            {"340031.7863518311933148652315139770507812499999999999999999999", 0x4114c0ff25396a18u},
+            {"0.0000000004543709717853330820053712055931242029538363880192264332436025142669677734375", 0x3dff3960f070bf76u},
+            {"0.00000000045437097178533308200537120559312420295383638801922643324360251426696777343751", 0x3dff3960f070bf76u},
+            {"0.0000000004543709717853330820053712055931242029538363880192264332436024142669677734375", 0x3dff3960f070bf75u},
+            {"0.0000000000007937958898451257082591244100968761704503924570008877026339177973568439483642578125", 0x3d6bede0b40e37c2u},
+            {"0.00000000000079379588984512570825912441009687617045039245700088770263391779735684394836425781251", 0x3d6bede0b40e37c3u},
+            {"0.0000000000007937958898451257082591244100968761704503924570008877026339176973568439483642578125", 0x3d6bede0b40e37c2u},
+            {"0.00000000000000068304843500200357021582520000166071595321259251644419041582523277611471712589263916015625", 0x3cc89c02848f8654u},
+            {"0.000000000000000683048435002003570215825200001660715953212592516444190415825232776114717125892639160156251", 0x3cc89c02848f8655u},
+            {"0.00000000000000068304843500200357021582520000166071595321259251644419041582513277611471712589263916015625", 0x3cc89c02848f8654u},
+            {"0.00000000147705080029041786940146712084494760863773166192913777194917201995849609375", 0x3e1960235bc34d06u},
+            {"0.000000001477050800290417869401467120844947608637731661929137771949172019958496093751", 0x3e1960235bc34d06u},
+            {"0.00000000147705080029041786940146712084494760863773166192913777194917101995849609375", 0x3e1960235bc34d05u},
+            {"2164972979236447104", 0x43be0b87743fb524u},
+            {"21649729792364471041", 0x43f2c734a8a7d136u},
+            {"2164972979236447103.999999999999999999999999999999999999999999", 0x43be0b87743fb523u},
+            {"13124633159586767", 0x4347506464a469e8u},
+            {"131246331595867671", 0x437d247d7dcd8461u},
+            {"13124633159586766.99999999999999999999999999999999999999999999", 0x4347506464a469e7u},
+            {"0.000000000000027605165650764659887597286048864477738779108113853499872902830247767269611358642578125", 0x3d1f14a5b417cb08u},
+            {"0.0000000000000276051656507646598875972860488644777387791081138534998729028302477672696113586425781251", 0x3d1f14a5b417cb09u},
+            {"0.000000000000027605165650764659887597286048864477738779108113853499872902820247767269611358642578125", 0x3d1f14a5b417cb08u},
+            {"0.01727792833395616796388072344825559412129223346710205078125", 0x3f91b14e248c42c8u},
+            {"0.017277928333956167963880723448255594121292233467102050781251", 0x3f91b14e248c42c9u},
+            {"0.01727792833395616796388072344825559412129223346710205078124999", 0x3f91b14e248c42c8u},
+            {"0.00000000000003096211381890547702500862566064822950373937142376501441276559489779174327850341796875", 0x3d216e1c61130b22u},
+            {"0.000000000000030962113818905477025008625660648229503739371423765014412765594897791743278503417968751", 0x3d216e1c61130b22u},
+            {"0.00000000000003096211381890547702500862566064822950373937142376501441276558489779174327850341796875", 0x3d216e1c61130b21u},
+            {"0.0000000000000683414954481284270259359974108983284531919182025472281338807079009711742401123046875", 0x3d333c86137e5170u},
+            {"0.00000000000006834149544812842702593599741089832845319191820254722813388070790097117424011230468751", 0x3d333c86137e5170u},
+            {"0.0000000000000683414954481284270259359974108983284531919182025472281338806979009711742401123046875", 0x3d333c86137e516fu},
+            {"3237539054990129.75", 0x4327010c9aa36664u},
+            {"3237539054990129.751", 0x4327010c9aa36664u},
+            {"3237539054990129.749999999999999999999999999999999999999999999", 0x4327010c9aa36663u},
+            {"0.0000000000000105429301486355911969397173440055240907798901443814809653076736140064895153045654296875", 0x3d07bd95dfb8a1eeu},
+            {"0.00000000000001054293014863559119693971734400552409077989014438148096530767361400648951530456542968751", 0x3d07bd95dfb8a1eeu},
+            {"0.0000000000000105429301486355911969397173440055240907798901443814809653076636140064895153045654296875", 0x3d07bd95dfb8a1edu},
+            {"9460.2061893763575426419265568256378173828125", 0x40c27a1a6469da1eu},
+            {"9460.20618937635754264192655682563781738281251", 0x40c27a1a6469da1fu},
+            {"9460.206189376357542641926556825637817382812499999999999999999", 0x40c27a1a6469da1eu},
+            {"465000373656610.53125", 0x42fa6ea56179c228u},
+            {"465000373656610.531251", 0x42fa6ea56179c229u},
+            {"465000373656610.5312499999999999999999999999999999999999999999", 0x42fa6ea56179c228u},
+            {"0.000000000107709773707743713401260815383950956818093214195641849073581397533416748046875", 0x3ddd9b66c974bb14u},
+            {"0.0000000001077097737077437134012608153839509568180932141956418490735813975334167480468751", 0x3ddd9b66c974bb14u},
+            {"0.000000000107709773707743713401260815383950956818093214195641849073581297533416748046875", 0x3ddd9b66c974bb13u},
+            {"0.012083347821554271152300064073870089487172663211822509765625", 0x3f88bf277dc215f4u},
+            {"0.0120833478215542711523000640738700894871726632118225097656251", 0x3f88bf277dc215f5u},
+            {"0.01208334782155427115230006407387008948717266321182250976562499", 0x3f88bf277dc215f4u},
+            {"2309804058391724800", 0x43c0070946d098e2u},
+            {"23098040583917248001", 0x43f408cb9884bf1au},
+            {"2309804058391724799.999999999999999999999999999999999999999999", 0x43c0070946d098e1u},
+            {"0.000000000078286047058220682019445698291671103911937290575906445155851542949676513671875", 0x3dd584e40ca80638u},
+            {"0.0000000000782860470582206820194456982916711039119372905759064451558515429496765136718751", 0x3dd584e40ca80638u},
+            {"0.000000000078286047058220682019445698291671103911937290575906445155851532949676513671875", 0x3dd584e40ca80637u},
+            {"2940024994425.709228515625", 0x4285643929d3cdacu},
+            {"2940024994425.7092285156251", 0x4285643929d3cdadu},
+            {"2940024994425.709228515624999999999999999999999999999999999999", 0x4285643929d3cdacu},
+            {"9503358.427352792583405971527099609375", 0x4162204fcdacdfc4u},
+            {"9503358.4273527925834059715270996093751", 0x4162204fcdacdfc4u},
+            {"9503358.427352792583405971527099609374999999999999999999999999", 0x4162204fcdacdfc3u},
+            {"0.00005589147834433423614399101542193903924271580763161182403564453125", 0x3f0d4da092aa5d6au},
+            {"0.000055891478344334236143991015421939039242715807631611824035644531251", 0x3f0d4da092aa5d6bu},
+            {"0.00005589147834433423614399101542193903924271580763161182403564452125", 0x3f0d4da092aa5d6au},
+            {"0.0000000164797038506435664295103900420409737126448135313694365322589874267578125", 0x3e51b1e8107bd640u},
+            {"0.00000001647970385064356642951039004204097371264481353136943653225898742675781251", 0x3e51b1e8107bd641u},
+            {"0.0000000164797038506435664295103900420409737126448135313694365322589774267578125", 0x3e51b1e8107bd640u},
+            {"73055.7873927834807545877993106842041015625", 0x40f1d5fc99292ce2u},
+            {"73055.78739278348075458779931068420410156251", 0x40f1d5fc99292ce3u},
+            {"73055.78739278348075458779931068420410156249999999999999999999", 0x40f1d5fc99292ce2u},
+            {"0.00000000002558172364455232122427880575336067736115508441940846751094795763492584228515625", 0x3dbc209d7509115au},
+            {"0.000000000025581723644552321224278805753360677361155084419408467510947957634925842285156251", 0x3dbc209d7509115bu},
+            {"0.00000000002558172364455232122427880575336067736115508441940846751094794763492584228515625", 0x3dbc209d7509115au},
+            {"0.000000000854497507560657937804791333430312443020238077906469698064029216766357421875", 0x3e0d5c3d540cc0d2u},
+            {"0.0000000008544975075606579378047913334303124430202380779064696980640292167663574218751", 0x3e0d5c3d540cc0d2u},
+            {"0.000000000854497507560657937804791333430312443020238077906469698064029116766357421875", 0x3e0d5c3d540cc0d1u},
+            {"26671499731071461376", 0x43f722433b19970eu},
+            {"266714997310714613761", 0x442cead409dffcd2u},
+            {"26671499731071461375.99999999999999999999999999999999999999999", 0x43f722433b19970eu},
+            {"0.0000000002725195963972150049060368088050545186395989816219298518262803554534912109375", 0x3df2ba37271cf5f2u},
+            {"0.00000000027251959639721500490603680880505451863959898162192985182628035545349121093751", 0x3df2ba37271cf5f2u},
+            {"0.0000000002725195963972150049060368088050545186395989816219298518262802554534912109375", 0x3df2ba37271cf5f1u},
+            {"0.0000000000377224663702246439557904325637937886957218314165629635681398212909698486328125", 0x3dc4bcf7157af68eu},
+            {"0.00000000003772246637022464395579043256379378869572183141656296356813982129096984863281251", 0x3dc4bcf7157af68fu},
+            {"0.0000000000377224663702246439557904325637937886957218314165629635681398112909698486328125", 0x3dc4bcf7157af68eu},
+            {"0.00000000000000009977342762593364154535842258994910996905560208471673566688053824691451154649257659912109375", 0x3c9cc1fac312e2a6u},
+            {"0.000000000000000099773427625933641545358422589949109969055602084716735666880538246914511546492576599121093751", 0x3c9cc1fac312e2a6u},
+            {"0.00000000000000009977342762593364154535842258994910996905560208471673566688052824691451154649257659912109375", 0x3c9cc1fac312e2a5u},
+            {"0.0000000003146248171139977444431948290159907662133509376189977047033607959747314453125", 0x3df59ef03588a228u},
+            {"0.00000000031462481711399774444319482901599076621335093761899770470336079597473144531251", 0x3df59ef03588a229u},
+            {"0.0000000003146248171139977444431948290159907662133509376189977047033606959747314453125", 0x3df59ef03588a228u},
+            {"488899209263030304", 0x439b23acf64c5e80u},
+            {"4888992092630303041", 0x43d0f64c19efbb10u},
+            {"488899209263030303.9999999999999999999999999999999999999999999", 0x439b23acf64c5e80u},
+            {"1.88357157350592807620870416940306313335895538330078125", 0x3ffe231bf23e21acu},
+            {"1.883571573505928076208704169403063133358955383300781251", 0x3ffe231bf23e21adu},
+            {"1.883571573505928076208704169403063133358955383300781249999999", 0x3ffe231bf23e21acu},
+            {"0.0000000216458400594294836451424756990254139044083103726734407246112823486328125", 0x3e573df694e72fb8u},
+            {"0.00000002164584005942948364514247569902541390440831037267344072461128234863281251", 0x3e573df694e72fb9u},
+            {"0.0000000216458400594294836451424756990254139044083103726734407246112723486328125", 0x3e573df694e72fb8u},
+            {"5107.79271041116453488939441740512847900390625", 0x40b3f3caef11cb26u},
+            {"5107.792710411164534889394417405128479003906251", 0x40b3f3caef11cb27u},
+            {"5107.792710411164534889394417405128479003906249999999999999999", 0x40b3f3caef11cb26u},
+            {"734059.8035226609208621084690093994140625", 0x412666d79b67527cu},
+            {"734059.80352266092086210846900939941406251", 0x412666d79b67527du},
+            {"734059.8035226609208621084690093994140624999999999999999999999", 0x412666d79b67527cu},
+            {"61431562016722684", 0x436b47f5c40021e0u},
+            {"614315620167226841", 0x43a10cf99a80152cu},
+            {"61431562016722683.99999999999999999999999999999999999999999999", 0x436b47f5c40021dfu},
+            {"2.0060840449445034305853141631814651191234588623046875", 0x40000c75cab08326u},
+            {"2.00608404494450343058531416318146511912345886230468751", 0x40000c75cab08326u},
+            {"2.006084044944503430585314163181465119123458862304687499999999", 0x40000c75cab08325u},
+            {"0.0000001760623599453036952716420489480075861621344301966018974781036376953125", 0x3e87a174e55262cau},
+            {"0.00000017606235994530369527164204894800758616213443019660189747810363769531251", 0x3e87a174e55262cbu},
+            {"0.0000001760623599453036952716420489480075861621344301966018974781035376953125", 0x3e87a174e55262cau},
+            {"0.833085849636964581588216560703585855662822723388671875", 0x3feaa8a3a7de6fb6u},
+            {"0.8330858496369645815882165607035858556628227233886718751", 0x3feaa8a3a7de6fb6u},
+            {"0.8330858496369645815882165607035858556628227233886718749999999", 0x3feaa8a3a7de6fb5u},
+            {"45031428.4182307310402393341064453125", 0x418579002358895au},
+            {"45031428.41823073104023933410644531251", 0x418579002358895bu},
+            {"45031428.41823073104023933410644531249999999999999999999999999", 0x418579002358895au},
+            {"5003361733758455296", 0x43d15be0bf39dd24u},
+            {"50033617337584552961", 0x4405b2d8ef08546cu},
+            {"5003361733758455295.999999999999999999999999999999999999999999", 0x43d15be0bf39dd23u},
+        };
+
+        for (const auto& c : known)
+        {
+            CAPTURE(c.first);
+            double out = 0;
+            if (eisel_lemire(c.first, out))
+            {
+                CHECK(bits_of(out) == c.second);
+            }
+            else
+            {
+                // only tokens with more than 19 significant digits are left to
+                // strtod: those whose value lies too close to a tie
+                CHECK(significant_digits(c.first) > 19);
+            }
+        }
+    }
+
+    SECTION("round trip")
+    {
+        // every double written by to_chars and read back, also with trailing
+        // digits that make the token longer than 19 digits
+        std::uint64_t state = 5295;
+        std::size_t declined = 0;
+        for (int i = 0; i < 200000; ++i)
+        {
+            state ^= state << 13u;
+            state ^= state >> 7u;
+            state ^= state << 17u;
+            std::uint64_t b = state;
+            if ((b & 0x7FF0000000000000u) == 0x7FF0000000000000u)
+            {
+                continue; // infinity or NaN
+            }
+            if (i % 4 == 0)
+            {
+                b &= 0x800FFFFFFFFFFFFFu; // subnormals
+            }
+            double d = 0;
+            std::memcpy(&d, &b, sizeof(d));
+
+            std::array<char, 64> buffer{};
+            const char* end = nlohmann::detail::to_chars(buffer.data(), buffer.data() + buffer.size(), d);
+            const std::string token(buffer.data(), static_cast<std::size_t>(end - buffer.data()));
+            CAPTURE(token);
+            double out = 0;
+            REQUIRE(eisel_lemire(token, out));
+            CHECK(bits_of(out) == b);
+
+            // insert digits before the exponent: the value moves by far less
+            // than the distance to the rounding boundary, so it must not change
+            std::string longer = token;
+            const std::size_t e = longer.find('e');
+            const std::size_t dot = longer.find('.');
+            const std::string extra = dot == std::string::npos ? ".000000000000000000001" : "000000000000000000001";
+            longer.insert(e == std::string::npos ? longer.size() : e, extra);
+            CAPTURE(longer);
+            if (eisel_lemire(longer, out))
+            {
+                CHECK(bits_of(out) == b);
+            }
+            else
+            {
+                // w and w + 1 round differently: only when the value is very
+                // close to a rounding boundary
+                ++declined;
+            }
+        }
+        CHECK(declined < 1000); // 107 of the 200,000
+    }
+
+    SECTION("used by the lexer")
+    {
+        // 17 significant digits: beyond Clinger's fast path
+        CHECK(bits_of(json::parse("-65.613616999999977").get<double>()) == bits_of(-65.613616999999977));
+        CHECK(bits_of(json::parse("2.2250738585072011e-308").get<double>()) == 0x000FFFFFFFFFFFFFu);
+        CHECK(bits_of(json::parse("4.9406564584124654e-324").get<double>()) == 1u);
+        json _;
+        CHECK_THROWS_WITH_AS(_ = json::parse("1.7976931348623159e308"),
+                             "[json.exception.out_of_range.406] number overflow parsing '1.7976931348623159e308'", json::out_of_range&);
+    }
+}

tests/src/unit-class_parser.cpp

@@ -645,6 +645,30 @@ TEST_CASE("parser class")
                 // carries a compiler-appended trailing '\0') still works,
                 // even though a NUL byte is now rejected everywhere else
                 CHECK(json::parse("123") == json(123));
+
+                // regression test for issue #5658: the same holds for wide,
+                // UTF-16, UTF-32, and (C++20) UTF-8 string literals, whose
+                // compiler-appended trailing '\0' is not of type `char`
+                CHECK(json::parse(L"[1]") == json({1}));
+                CHECK(json::accept(L"[1]"));
+                CHECK(json::parse(u"[1]") == json({1}));
+                CHECK(json::accept(u"[1]"));
+                CHECK(json::parse(U"[1]") == json({1}));
+                CHECK(json::accept(U"[1]"));
+#if defined(__cpp_char8_t)
+                CHECK(json::parse(u8"[1]") == json({1}));
+                CHECK(json::accept(u8"[1]"));
+#endif
+
+                // a NUL byte inside such a literal, as opposed to the single
+                // compiler-appended trailing one, is still rejected
+                {
+                    json _; // NOLINT(readability-identifier-naming)
+                    CHECK_THROWS_WITH_AS(_ = json::parse(L"[1\0]"),
+                                         "[json.exception.parse_error.101] parse error at line 1, column 3: syntax error while parsing array - invalid literal; last read: '1<U+0000>'; expected ']'",
+                                         json::parse_error&);
+                    CHECK_FALSE(json::accept(L"[1\0]"));
+                }
             }
 #endif
         }
@@ -1966,6 +1990,102 @@ TEST_CASE("parser class")
             }
         }
 
+        SECTION("no callback for the content of a discarded container (#5643)")
+        {
+            // discarding a container at its start event must also hide
+            // everything inside it from the callback: none of the nested
+            // keys, values, or nested containers' own start/end events may
+            // be reported
+            std::vector<std::string> log;
+            bool first = true;
+            const json j = json::parse(R"({"skip": {"k1": 1, "k2": [2, {"k3": 3}]}, "keep": 1})",
+                                       [&](int depth, json::parse_event_t event, json & parsed)
+            {
+                static const char* const names[] = {"object_start", "object_end", "array_start", "array_end", "key", "value"};
+                log.push_back(std::to_string(depth) + " " + names[static_cast<int>(event)] + " " + parsed.dump());
+
+                if (depth == 1 && event == json::parse_event_t::object_start && first)
+                {
+                    // discard "skip" right at its object_start event
+                    first = false;
+                    return false;
+                }
+                return true;
+            });
+
+            CHECK(log == std::vector<std::string>
+            {
+                "0 object_start <discarded>",
+                "1 key \"skip\"",
+                "1 object_start <discarded>",
+                "1 key \"keep\"",
+                "1 value 1",
+                "0 object_end {\"keep\":1}"
+            });
+            CHECK(j == json({{"keep", 1}}));
+        }
+
+        SECTION("callback still called inside a container whose key was rejected (#5643)")
+        {
+            // rejecting a key does not discard its value's container at the
+            // container's own start event, so the callback is still called
+            // for that container's content; only storing the container
+            // under the rejected key is skipped
+            // (documented for parser_callback_t: "the callback is still
+            // called for the associated value, but its return value has no
+            // further effect")
+            const auto record = [](std::vector<std::string>& log, int depth, json::parse_event_t event, const json & parsed)
+            {
+                static const char* const names[] = {"object_start", "object_end", "array_start", "array_end", "key", "value"};
+                log.push_back(std::to_string(depth) + " " + names[static_cast<int>(event)] + " " + parsed.dump());
+            };
+
+            std::vector<std::string> log_object;
+            const json j_object = json::parse(R"({"skip": {"k1": 1}, "keep": 2})",
+                                              [&](int depth, json::parse_event_t event, json & parsed)
+            {
+                record(log_object, depth, event, parsed);
+                return !(event == json::parse_event_t::key && parsed == json("skip"));
+            });
+
+            CHECK(log_object == std::vector<std::string>
+            {
+                "0 object_start <discarded>",
+                "1 key \"skip\"",
+                "1 object_start <discarded>",
+                "2 key \"k1\"",
+                "2 value 1",
+                "1 key \"keep\"",
+                "1 value 2",
+                "0 object_end {\"keep\":2}"
+            });
+            CHECK(j_object == json({{"keep", 2}}));
+
+            // same for a rejected key whose value is an array rather than an object
+            std::vector<std::string> log_array;
+            const json j_array = json::parse(R"({"skip": [1, {"k1": 2}], "keep": 2})",
+                                             [&](int depth, json::parse_event_t event, json & parsed)
+            {
+                record(log_array, depth, event, parsed);
+                return !(event == json::parse_event_t::key && parsed == json("skip"));
+            });
+
+            CHECK(log_array == std::vector<std::string>
+            {
+                "0 object_start <discarded>",
+                "1 key \"skip\"",
+                "1 array_start <discarded>",
+                "2 value 1",
+                "2 object_start <discarded>",
+                "3 key \"k1\"",
+                "3 value 2",
+                "1 key \"keep\"",
+                "1 value 2",
+                "0 object_end {\"keep\":2}"
+            });
+            CHECK(j_array == json({{"keep", 2}}));
+        }
+
         SECTION("special cases")
         {
             // the following test cases cover the situation in which an empty

tests/src/unit-comparison.cpp

@@ -17,6 +17,7 @@
 
 #include <algorithm>
 
+#include <cctype>
 #include <cstdint>
 #include <map>
 #include <string>
@@ -825,6 +826,64 @@ Json nest(Json j, const std::size_t depth)
     }
     return j;
 }
+
+// a std::map comparator with state: case-insensitive, unless constructed
+// case-sensitive. Used to check that copying an object copies the original's
+// comparator rather than default-constructing a new one (see #5649).
+struct key_case_less
+{
+    key_case_less() = default;
+    explicit key_case_less(const bool cs) noexcept : case_sensitive(cs) {}
+
+    bool operator()(const std::string& a, const std::string& b) const
+    {
+        if (case_sensitive)
+        {
+            return a < b;
+        }
+        return std::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end(),
+                                            [](unsigned char x, unsigned char y)
+        {
+            return std::tolower(x) < std::tolower(y);
+        });
+    }
+
+    bool case_sensitive = false;
+};
+
+template<class Key, class Value, class /*Compare*/, class Allocator>
+using key_case_map = std::map<Key, Value, key_case_less, Allocator>;
+using key_case_json = nlohmann::basic_json<key_case_map>;
+
+// the innermost value of a chain of single-element arrays
+template<typename Json>
+const Json& innermost(const Json& j)
+{
+    const Json* p = &j;
+    while (p->is_array())
+    {
+        p = &(*p)[0];
+    }
+    return *p;
+}
+
+// orders keys case-insensitively, so "key" and "KEY" compare equivalent
+// (neither less than the other) although they are not equal
+struct case_insensitive_less
+{
+    bool operator()(const std::string& a, const std::string& b) const
+    {
+        return std::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end(),
+                                            [](unsigned char x, unsigned char y)
+        {
+            return std::tolower(x) < std::tolower(y);
+        });
+    }
+};
+
+template<class Key, class Value, class /*Compare*/, class Allocator>
+using case_insensitive_map = std::map<Key, Value, case_insensitive_less, Allocator>;
+using ci_json = nlohmann::basic_json<case_insensitive_map>;
 } // namespace
 
 TEST_CASE("equality of objects whose entries have no fixed order")
@@ -872,6 +931,74 @@ TEST_CASE("equality of objects whose entries have no fixed order")
     }
 }
 
+TEST_CASE("copying an object preserves its comparator's state")
+{
+    // Past the iterative deep copy's nesting bound, an object copy used to be
+    // built with a default-constructed comparator instead of a copy of the
+    // original's. For an object type whose comparator carries state - here, a
+    // std::map that compares keys case-sensitively only when created that way
+    // - this reordered the copy's keys and could even drop entries that the
+    // original's comparator kept distinct (see #5649).
+    key_case_json object = key_case_json::object_t(key_case_less(true)); // case-sensitive
+    object["b"] = 1;
+    object["B"] = 2;
+    object["a"] = 3;
+    REQUIRE(object.dump() == R"({"B":2,"a":3,"b":1})");
+
+    for (const std::size_t depth : std::vector<std::size_t> {0, 127, 128, 200})
+    {
+        CAPTURE(depth);
+
+        key_case_json original = object;
+        for (std::size_t i = 0; i < depth; ++i)
+        {
+            original = key_case_json::array({std::move(original)});
+        }
+
+        {
+            const key_case_json copy = original; // NOLINT(performance-unnecessary-copy-initialization)
+            CHECK(innermost(copy).size() == 3);
+            CHECK(innermost(copy).dump() == R"({"B":2,"a":3,"b":1})");
+            CHECK(copy == original);
+        }
+
+        {
+            key_case_json copy = key_case_json::array();
+            copy = original;
+            CHECK(innermost(copy).size() == 3);
+            CHECK(innermost(copy).dump() == R"({"B":2,"a":3,"b":1})");
+            CHECK(copy == original);
+        }
+    }
+}
+
+TEST_CASE("equality of an object whose comparator treats different keys as equivalent")
+{
+    // https://github.com/nlohmann/json/issues/5655: past the nesting bound,
+    // the entries are compared without the call stack, and a key that finds
+    // no counterpart at the same position is looked up with find(), which
+    // uses the object's own comparator. A case-insensitive comparator then
+    // finds "KEY" for "key" and must not accept that pair as a match - the
+    // object type's own operator==, like std::map's, compares keys with ==.
+    ci_json a = ci_json::object();
+    a["key"] = 1;
+    ci_json b = ci_json::object();
+    b["KEY"] = 1;
+
+    // sanity check: the object type's own comparison already disagrees
+    CHECK_FALSE(a.get_ref<const ci_json::object_t&>() == b.get_ref<const ci_json::object_t&>());
+
+    for (const std::size_t depth : std::vector<std::size_t> {0, 127, 128, 200})
+    {
+        CAPTURE(depth);
+
+        const ci_json x = nest(a, depth);
+        const ci_json y = nest(b, depth);
+        CHECK_FALSE(x == y);
+        CHECK(x != y);
+    }
+}
+
 TEST_CASE("containers are compared element by element")
 {
     // Containers nested deeper than a bound are compared without the call

tests/src/unit-constructor1.cpp

@@ -1648,6 +1648,20 @@ TEST_CASE("constructors")
                         CHECK_THROWS_WITH_AS(json(j.cbegin(), j.cbegin()), "[json.exception.invalid_iterator.204] iterators out of range", json::invalid_iterator&);
                     }
                 }
+
+                SECTION("binary")
+                {
+                    {
+                        json j = json::binary({1, 2, 3});
+                        CHECK_THROWS_WITH_AS(json(j.end(), j.end()), "[json.exception.invalid_iterator.204] iterators out of range", json::invalid_iterator&);
+                        CHECK_THROWS_WITH_AS(json(j.begin(), j.begin()), "[json.exception.invalid_iterator.204] iterators out of range", json::invalid_iterator&);
+                    }
+                    {
+                        json const j = json::binary({1, 2, 3});
+                        CHECK_THROWS_WITH_AS(json(j.cend(), j.cend()), "[json.exception.invalid_iterator.204] iterators out of range", json::invalid_iterator&);
+                        CHECK_THROWS_WITH_AS(json(j.cbegin(), j.cbegin()), "[json.exception.invalid_iterator.204] iterators out of range", json::invalid_iterator&);
+                    }
+                }
             }
         }
     }

tests/src/unit-conversions.cpp

@@ -1358,6 +1358,14 @@ TEST_CASE("value conversion")
         CHECK(json(value_1).get<c_enum>() == value_1);
         CHECK(json(cpp_enum::value_1).get<cpp_enum>() == cpp_enum::value_1);
     }
+
+    SECTION("get an enum with underlying type bool (#5671)")
+    {
+        enum class bool_enum : bool { off, on };
+
+        CHECK(json(bool_enum::off).get<bool_enum>() == bool_enum::off);
+        CHECK(json(bool_enum::on).get<bool_enum>() == bool_enum::on);
+    }
 #endif
 
     SECTION("more involved conversions")
@@ -1740,6 +1748,12 @@ TEST_CASE("Strict JSON to enum mapping")
 
         // conversion of unmapped enum -> exception thrown
         CHECK_THROWS_WITH_AS(json(strict_cards::andere), "[json.exception.out_of_range.410] enum value out of range for strict_cards", json::out_of_range&);
+
+        // invalid UTF-8 -> out_of_range.410, not the type_error.316 thrown while building the
+        // message (regression test for #5667); such strings can reach get<Enum>() unvalidated,
+        // e.g. from from_cbor()/from_msgpack() (#5529)
+        const json j_invalid_utf8 = "\xFF";
+        CHECK_THROWS_WITH_AS(_ = j_invalid_utf8.get<strict_cards>(), "[json.exception.out_of_range.410] enum value out of range for strict_cards: \"\xEF\xBF\xBD\"", json::out_of_range&);
     }
 
     SECTION("traditional enum")
@@ -1826,6 +1840,21 @@ TEST_CASE("std::u8string")
 #endif
 #endif
 
+#if !defined(JSON_NOEXCEPTION)
+namespace
+{
+// a type whose to_json reports an error by throwing, used below to check that
+// converting a std::optional<T> to JSON propagates an exception thrown while
+// converting its contained value instead of calling std::terminate (#5642)
+struct throwing_to_json_type {};
+
+[[noreturn]] void to_json(json& /*unused*/, const throwing_to_json_type& /*unused*/)
+{
+    throw std::runtime_error("cannot serialize throwing_to_json_type");
+}
+}  // namespace
+#endif
+
 TEST_CASE("std::optional")
 {
     SECTION("null")
@@ -1908,6 +1937,23 @@ TEST_CASE("std::optional")
         CHECK(json(opt_object) == j_object);
         CHECK(std::map<std::string, std::optional<int>>(j_object) == opt_object);
     }
+
+#if !defined(JSON_NOEXCEPTION)
+    SECTION("exception from contained value's to_json propagates (#5642)")
+    {
+        // to_json(BasicJsonType&, const std::optional<T>&) must not be
+        // noexcept: it calls T's to_json, which may throw (a user-defined
+        // to_json that reports an error, or std::bad_alloc for T =
+        // std::string/vector/json). Before the fix, this called
+        // std::terminate() instead of letting the exception propagate.
+        const std::optional<throwing_to_json_type> opt = throwing_to_json_type{};
+        CHECK_THROWS_WITH_AS(json(opt), "cannot serialize throwing_to_json_type", std::runtime_error&);
+
+        // the conversion is noexcept exactly when converting the contained value is
+        static_assert(!std::is_nothrow_constructible<json, const std::optional<throwing_to_json_type>&>::value, "");
+        static_assert(std::is_nothrow_constructible<json, const std::optional<int>&>::value, "");
+    }
+#endif
 }
 #endif
 

tests/src/unit-custom-array-type.cpp

@@ -117,6 +117,22 @@ TEST_CASE("array type without capacity()")
         CHECK(nested.flatten().unflatten() == nested);
     }
 
+    SECTION("insert(pos, initializer_list) compiles and works without reserve()")
+    {
+        // std::deque has no reserve() either; insert(pos, ilist) must not
+        // require it (regression test for #5656, which also covers an ilist
+        // that refers to elements of the array being inserted into)
+        deque_json j = deque_json::array();
+        j.push_back("a");
+        j.push_back("b");
+        j.push_back("c");
+
+        const deque_json& cj = j;
+        auto it = j.insert(j.begin(), {cj[0], cj[1]});
+        CHECK(*it == deque_json("a"));
+        CHECK(j == deque_json({"a", "b", "a", "b", "c"}));
+    }
+
     SECTION("references stay valid while the array grows")
     {
         deque_json j = deque_json::array();

tests/src/unit-custom-base-class.cpp

@@ -6,9 +6,11 @@
 // SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
 // SPDX-License-Identifier: MIT
 
+#include <algorithm>
 #include <set>
 #include <sstream>
 #include <string>
+#include <vector>
 
 #include "doctest_compatibility.h"
 
@@ -180,6 +182,76 @@ TEST_CASE("JSON Node Metadata")
             CHECK(val.metadata().at(1)  == 2);
         }
     }
+    SECTION("member swap")
+    {
+        using json = json_with_metadata<int>;
+        json a = 1;
+        a.metadata() = 100;
+        json b = 2;
+        b.metadata() = 200;
+
+        a.swap(b);
+
+        CHECK(a.get<int>()  == 2);
+        CHECK(b.get<int>()  == 1);
+        CHECK(a.metadata()  == 200);
+        CHECK(b.metadata()  == 100);
+    }
+    SECTION("nonmember swap")
+    {
+        using json = json_with_metadata<int>;
+        json a = 1;
+        a.metadata() = 100;
+        json b = 2;
+        b.metadata() = 200;
+
+        using std::swap;
+        swap(a, b);
+
+        CHECK(a.get<int>()  == 2);
+        CHECK(b.get<int>()  == 1);
+        CHECK(a.metadata()  == 200);
+        CHECK(b.metadata()  == 100);
+    }
+    SECTION("std::swap")
+    {
+        using json = json_with_metadata<int>;
+        json a = 1;
+        a.metadata() = 100;
+        json b = 2;
+        b.metadata() = 200;
+
+        std::swap(a, b);
+
+        CHECK(a.get<int>()  == 2);
+        CHECK(b.get<int>()  == 1);
+        CHECK(a.metadata()  == 200);
+        CHECK(b.metadata()  == 100);
+    }
+    SECTION("std::sort keeps metadata attached to its value")
+    {
+        // std::sort mixes swap() with moves; each value's metadata must
+        // travel with it, just as it does for copy, move, and assignment
+        using json = json_with_metadata<int>;
+        std::vector<json> values;
+        for (int v :
+                {
+                    5, 3, 9, 1, 7, 2, 8, 4, 6, 0, 15, 13, 19, 11, 17, 12, 18, 14, 16, 10,
+                    25, 23, 29, 21, 27, 22, 28, 24, 26, 20, 35, 33
+                })
+        {
+            json value = v;
+            value.metadata() = v;
+            values.push_back(value);
+        }
+
+        std::sort(values.begin(), values.end());
+
+        for (const auto& value : values)
+        {
+            CHECK(value.metadata() == value.get<int>());
+        }
+    }
 }
 
 // Test extending nlohmann::json by using a custom base class.

tests/src/unit-deserialization.cpp

@@ -388,6 +388,37 @@ TEST_CASE("deserialization")
             }));
         }
 
+        SECTION("stream with eofbit in its exception mask (issue #5646)")
+        {
+            // reaching EOF while parsing a value that fills the whole input
+            // (e.g., a number, or any value under strict parsing) makes
+            // get_character() call std::istream::clear() to record eofbit;
+            // with eofbit in the exception mask, that clear() itself throws
+            // std::ios_base::failure - it must propagate to the caller instead
+            // of ~input_stream_adapter() throwing a second exception while the
+            // first is still unwinding, which would call std::terminate
+            json _;
+
+            std::istringstream is1("1");
+            is1.exceptions(std::ios::eofbit);
+            CHECK_THROWS_AS(_ = json::parse(is1), std::ios_base::failure&);
+
+            // the same holds for the common std::ifstream::exceptions(failbit |
+            // badbit | eofbit) pattern, because only eofbit ends up set
+            std::istringstream is2("1");
+            is2.exceptions(std::ios::failbit | std::ios::badbit | std::ios::eofbit);
+            CHECK_THROWS_AS(_ = json::parse(is2), std::ios_base::failure&);
+        }
+
+        SECTION("stream without a streambuf (issue #5646)")
+        {
+            // std::istream(nullptr) has badbit set and rdbuf() == nullptr;
+            // get_character() must not dereference that null streambuf
+            std::istream is(nullptr);
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::parse(is), "[json.exception.parse_error.101] parse error: attempting to parse an empty input; check that your input string or stream contains the expected JSON", json::parse_error&);
+        }
+
         SECTION("string")
         {
             json::string_t const s = R"(["foo",1,2,3,false,{"one":1})";

tests/src/unit-diagnostics.cpp

@@ -17,6 +17,10 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
+#include <map>
+#include <unordered_map>
+#include <sstream>
+
 TEST_CASE("Better diagnostics")
 {
     SECTION("empty JSON Pointer")
@@ -101,6 +105,12 @@ TEST_CASE("Regression tests for extended diagnostics")
         CHECK_THROWS_WITH_AS(j.unflatten(), "[json.exception.type_error.315] (/~1foo) values in object must be primitive", json::type_error);
     }
 
+    SECTION("Regression test for issue #5675 - to_bson: out_of_range.415 has no diagnostics context")
+    {
+        json const j = {{"a", {{"b", json::binary({1, 2}, 300)}}}};
+        CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.out_of_range.415] (/a/b) subtype 300 is too large for the BSON binary subtype (max 255)", json::out_of_range);
+    }
+
     SECTION("Regression test for issue #2838 - Assertion failure when inserting into arrays with JSON_DIAGNOSTICS set")
     {
         // void push_back(basic_json&& val)
@@ -331,6 +341,28 @@ TEST_CASE("Regression tests for extended diagnostics")
         }
     }
 
+    SECTION("Regression test for issue #5668 - wrong path for std::map/unordered_map with non-string keys")
+    {
+        // a map with non-string keys is read from an array of [key, value] arrays;
+        // element 2 of "m" is not an array, so the path must point at "m/2", not "m"
+        json j;
+        j["outer"]["m"] = json::array({json::array({1, 2}), json::array({3, 4}), 5});
+
+        SECTION("std::map")
+        {
+            CHECK_THROWS_WITH_AS((j["outer"]["m"].get<std::map<int, int>>()),
+                                 "[json.exception.type_error.302] (/outer/m/2) type must be array, "
+                                 "but is number", json::type_error);
+        }
+
+        SECTION("std::unordered_map")
+        {
+            CHECK_THROWS_WITH_AS((j["outer"]["m"].get<std::unordered_map<int, int>>()),
+                                 "[json.exception.type_error.302] (/outer/m/2) type must be array, "
+                                 "but is number", json::type_error);
+        }
+    }
+
     SECTION("Regression test - swap(array_t&)/swap(object_t&) must update JSON_DIAGNOSTICS parent pointers")
     {
         // swap(array_t&)
@@ -461,6 +493,21 @@ TEST_CASE("Regression tests for extended diagnostics")
             CHECK(copy == j);
         }
     }
+
+    SECTION("Regression test for issue #5652 - operator>> leaves a partial value in its target on a parse error")
+    {
+        json j = "old value";
+        std::istringstream is("[1, x");
+        CHECK_THROWS_WITH_AS(is >> j, "[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - invalid literal; last read: '1, x'", json::parse_error);
+
+        // j must be left unchanged, as json::parse() guarantees for its result
+        CHECK(j == "old value");
+
+        // copying j must not trigger assert_invariant(): a failed parse must
+        // not leave array/object elements without a parent pointer
+        json const copy = j; // NOLINT(performance-unnecessary-copy-initialization)
+        CHECK(copy == j);
+    }
 }
 
 TEST_CASE("Better diagnostics past the descent bound of update() and merge_patch()")

tests/src/unit-disabled_exceptions.cpp

@@ -46,6 +46,24 @@ TEST_CASE("Tests with disabled exceptions")
         CHECK(*sax_no_exception::error_string == "[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - invalid literal; last read: 'x'");
         delete sax_no_exception::error_string; // NOLINT(cppcoreguidelines-owning-memory)
     }
+
+    SECTION("growing an ordered_json object")
+    {
+        auto j = nlohmann::ordered_json::object();
+        for (int i = 0; i < 100; ++i)
+        {
+            j[std::to_string(i)] = {{"nested", i}};
+        }
+
+        CHECK(j.size() == 100);
+        int i = 0;
+        for (const auto& element : j.items())
+        {
+            CHECK(element.key() == std::to_string(i));
+            CHECK(element.value()["nested"] == i);
+            ++i;
+        }
+    }
 }
 
 DOCTEST_GCC_SUPPRESS_WARNING_POP

tests/src/unit-element_access1.cpp

@@ -147,6 +147,24 @@ TEST_CASE("element access 1")
                 CHECK(j_const[7] == json({1, 2, 3}));
             }
 
+            SECTION("SIZE_MAX index (#5647)")
+            {
+                // idx + 1 must not be computed for idx == SIZE_MAX: it wraps to 0,
+                // which would empty the array and then write out of bounds instead
+                // of growing it; reject it like an oversized resize() would and
+                // leave the array unchanged
+                const auto max_idx = (std::numeric_limits<json::size_type>::max)();
+                const std::string expected = "array index " + std::to_string(max_idx) + " exceeds size_type";
+                const json j_before = j; // NOLINT(performance-unnecessary-copy-initialization)
+
+                CHECK_THROWS_WITH_AS(j[max_idx] = 1, expected.c_str(), std::length_error&);
+                CHECK(j == j_before);
+
+                json j_empty = json::array();
+                CHECK_THROWS_WITH_AS(j_empty[max_idx] = 1, expected.c_str(), std::length_error&);
+                CHECK(j_empty == json::array());
+            }
+
             SECTION("access on non-array type")
             {
                 SECTION("null")

tests/src/unit-element_access2.cpp

@@ -16,6 +16,40 @@
 // build test with C++14
 // JSON_HAS_CPP_14
 
+// used to check at compile time (via is_detected) whether a call is well-formed; see
+// https://github.com/nlohmann/json/issues/5657
+//
+// note: an integer *literal* (rather than a std::declval<T>() of integral type T) is required to
+// reproduce the bug, because only a null pointer constant--an integer literal with value zero, not
+// merely a runtime value that happens to be zero--implicitly converts to a null const char*; that is
+// why can_call_*_with_0 below hard-code the literal 0 instead of taking it as a template argument
+template<typename BasicJsonType, typename T>
+using can_call_find = decltype(std::declval<BasicJsonType>().find(std::declval<T>()));
+
+template<typename BasicJsonType, typename T>
+using can_call_count = decltype(std::declval<BasicJsonType>().count(std::declval<T>()));
+
+template<typename BasicJsonType, typename T>
+using can_call_contains = decltype(std::declval<BasicJsonType>().contains(std::declval<T>()));
+
+template<typename BasicJsonType, typename KeyType, typename ValueType>
+using can_call_value = decltype(std::declval<BasicJsonType>().value(std::declval<KeyType>(), std::declval<ValueType>()));
+
+template<typename BasicJsonType>
+using can_call_find_with_0 = decltype(std::declval<BasicJsonType>().find(0));
+
+template<typename BasicJsonType>
+using can_call_count_with_0 = decltype(std::declval<BasicJsonType>().count(0));
+
+template<typename BasicJsonType>
+using can_call_contains_with_0 = decltype(std::declval<BasicJsonType>().contains(0));
+
+template<typename BasicJsonType>
+using can_call_contains_with_0L = decltype(std::declval<BasicJsonType>().contains(0L));
+
+template<typename BasicJsonType>
+using can_call_value_with_0 = decltype(std::declval<BasicJsonType>().value(0, 1));
+
 TEST_CASE_TEMPLATE("element access 2", Json, nlohmann::json, nlohmann::ordered_json) // NOLINT(readability-math-missing-parentheses, bugprone-throwing-static-initialization)
 {
     SECTION("object")
@@ -1493,6 +1527,53 @@ TEST_CASE_TEMPLATE("element access 2", Json, nlohmann::json, nlohmann::ordered_j
             }
         }
     }
+
+    SECTION("integral keys for object lookup are rejected at compile time")
+    {
+        // https://github.com/nlohmann/json/issues/5657: an integer literal like 0 is a null pointer
+        // constant, which used to convert to a null const char* and from there--via undefined
+        // behavior in the std::string constructor--to key_type, so contains(0), find(0), and
+        // count(0) used to compile and then crash instead of failing to compile
+        using nlohmann::detail::is_detected;
+
+        CHECK_FALSE(is_detected<can_call_find_with_0, Json&>::value);
+        CHECK_FALSE(is_detected<can_call_find_with_0, const Json&>::value);
+        CHECK_FALSE(is_detected<can_call_count_with_0, Json&>::value);
+        CHECK_FALSE(is_detected<can_call_contains_with_0, Json&>::value);
+        // value(0, ...) is only affected in C++11, where the comparator is not transparent; with a
+        // transparent comparator (C++14 and later), int is already rejected for lacking a
+        // comparison with the key type, independently of this fix
+        CHECK_FALSE(is_detected<can_call_value_with_0, const Json&>::value);
+
+        // another integral literal type must be rejected as well, not just int
+        CHECK_FALSE(is_detected<can_call_contains_with_0L, Json&>::value);
+
+        // the valid overloads must remain callable
+        CHECK(is_detected<can_call_find, Json&, const char*>::value);
+        CHECK(is_detected<can_call_find, Json&, std::string>::value);
+        CHECK(is_detected<can_call_count, Json&, const char*>::value);
+        CHECK(is_detected<can_call_contains, Json&, const char*>::value);
+        CHECK(is_detected<can_call_contains, Json&, typename Json::json_pointer>::value);
+        CHECK(is_detected<can_call_value, const Json&, const char*, int>::value);
+        CHECK(is_detected<can_call_value, const Json&, typename Json::json_pointer, int>::value);
+
+#ifdef JSON_HAS_CPP_17
+        CHECK(is_detected<can_call_find, Json&, std::string_view>::value);
+        CHECK(is_detected<can_call_count, Json&, std::string_view>::value);
+        CHECK(is_detected<can_call_contains, Json&, std::string_view>::value);
+#endif
+
+        // the neighboring size_type overloads for array access are unaffected by the new
+        // integral-key overloads above (at(), operator[](), and erase() take a size_type)
+        Json arr = {10, 20, 30};
+        const Json arr_const = arr;
+        CHECK(arr.at(0) == 10);
+        CHECK(arr_const.at(0) == 10);
+        CHECK(arr[0] == 10);
+        CHECK(arr_const[0] == 10);
+        arr.erase(0);
+        CHECK(arr.size() == 2);
+    }
 }
 
 #if !defined(JSON_NOEXCEPTION)

tests/src/unit-json_patch.cpp

@@ -1752,6 +1752,58 @@ TEST_CASE("JSON patch - diff emits array removals in descending index order")
     }
 }
 
+TEST_CASE("JSON patch - diff() takes the fast path for non-reorderable object types (regression #5639)")
+{
+    // #5465 added an order check to diff()'s object handling so a
+    // member-by-member diff is only used when it would also reproduce
+    // target's member *order* -- needed for ordered_json, whose object_t
+    // keeps insertion order and whose patch() "add" op appends a new
+    // member at the end. For json's default object_t (std::map, which
+    // orders members by key regardless of insertion history), that check
+    // could still fail: a new key that sorts before an existing common key
+    // makes target's iteration interleave the new key between common keys,
+    // even though nothing else about the object changed. That sent the
+    // whole object through the slow (remove-every-member,
+    // re-add-every-member) path instead of the minimal one.
+    SECTION("json: added key sorts before an existing common key")
+    {
+        const json source = {{"a", 1}, {"c", {{"x", 1}, {"y", 2}}}};
+        const json target = {{"a", 1}, {"b", 0}, {"c", {{"x", 1}, {"y", 2}}}};
+
+        const json patch = json::diff(source, target);
+
+        // only the new key is added; "a" and "c" are left alone instead of
+        // being removed and re-added
+        const json expected = R"([{"op": "add", "path": "/b", "value": 0}])"_json;
+        CHECK(patch == expected);
+        CHECK(source.patch(patch) == target);
+    }
+
+    SECTION("ordered_json: reordering behavior from #5465 is unchanged")
+    {
+        using nlohmann::ordered_json;
+
+        // same key/value shape as the json case above, but for ordered_json
+        // the *target*'s member order must be reproduced, so the slow path
+        // is still required here.
+        ordered_json source;
+        source["a"] = 1;
+        source["c"] = ordered_json{{"x", 1}, {"y", 2}};
+
+        ordered_json target;
+        target["a"] = 1;
+        target["b"] = 0;
+        target["c"] = ordered_json{{"x", 1}, {"y", 2}};
+
+        const ordered_json patch = ordered_json::diff(source, target);
+
+        // unlike the json case: every member is still removed and re-added
+        // so the result ends up in target's order (2 removes + 3 adds)
+        CHECK(patch.size() == 5);
+        CHECK(source.patch(patch) == target);
+    }
+}
+
 TEST_CASE("JSON patch - every operation on ordered_json")
 {
     using nlohmann::ordered_json;

tests/src/unit-json_pointer.cpp

@@ -380,6 +380,26 @@ TEST_CASE("JSON pointers")
 
             DOCTEST_MSVC_SUPPRESS_WARNING_POP
 
+            {
+                // contains() must not throw for an empty reference token if the current
+                // value is an array (cf. #5395) -- at() still reports out_of_range.404
+                json j_nested = {{"a", {1, 2}}};
+                const json& j_nested_const = j_nested;
+                json::json_pointer const jp("/a/");
+                std::string const throw_msg = "[json.exception.out_of_range.404] unresolved reference token ''";
+
+                CHECK_THROWS_WITH_AS(j_nested.at(jp), throw_msg.c_str(), json::out_of_range&);
+                CHECK_THROWS_WITH_AS(j_nested_const.at(jp), throw_msg.c_str(), json::out_of_range&);
+
+                CHECK(j_nested.contains(json::json_pointer("/a/1")));
+                CHECK(!j_nested.contains(jp));
+                CHECK(!j_nested_const.contains(jp));
+
+                // same for an empty reference token on a top-level array
+                CHECK(!j.contains(json::json_pointer("/")));
+                CHECK(!j_const.contains(json::json_pointer("/")));
+            }
+
             CHECK_THROWS_WITH_AS(j.at("/one"_json_pointer) = 1,
                                  "[json.exception.parse_error.109] parse error: array index 'one' is not a number", json::parse_error&);
             CHECK_THROWS_WITH_AS(j_const.at("/one"_json_pointer) == 1,
@@ -858,6 +878,25 @@ TEST_CASE("JSON pointers")
         }
     }
 
+    SECTION("value(json_pointer, default) with ordered_json #5664")
+    {
+        // ordered_json's transparent object comparator made value()'s
+        // is_comparable_with_object_key check (which passes the pointer as
+        // a reference) instantiate the deprecated json_pointer/string
+        // comparison; this must compile without relying on it. The
+        // deprecation warning itself is not observable here, since the
+        // unit test build disables -Wdeprecated-declarations (see
+        // cmake/clang_flags.cmake); it was checked manually instead.
+        const nlohmann::ordered_json j = {{"n", 1}, {"s", "text"}};
+        const nlohmann::ordered_json::json_pointer ptr_n("/n");
+        const nlohmann::ordered_json::json_pointer ptr_s("/s");
+        const nlohmann::ordered_json::json_pointer ptr_missing("/missing");
+
+        CHECK(j.value(ptr_n, 0) == 1);
+        CHECK(j.value(ptr_s, std::string("x")) == "text");
+        CHECK(j.value(ptr_missing, 42) == 42);
+    }
+
     // build with C++20
     // JSON_HAS_CPP_20
 #if defined(__cpp_char8_t)

tests/src/unit-locale-cpp.cpp

@@ -12,7 +12,12 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
+#include <array>
 #include <clocale>
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
 
 struct ParserImpl final: public nlohmann::json_sax<json>
 {
@@ -175,3 +180,208 @@ TEST_CASE("locale-dependent test (LC_NUMERIC=de_DE)")
         MESSAGE("locale de_DE is not usable");
     }
 }
+
+namespace
+{
+// records the numbers of a flat array and switches LC_NUMERIC to the given
+// locale once the array opens - after the lexer was constructed, but before
+// any number in the array is lexed
+struct LocaleSwitchingSax final: public nlohmann::json_sax<json>
+{
+    explicit LocaleSwitchingSax(const char* switch_to)
+        : locale_after_open(switch_to)
+    {}
+
+    bool null() override
+    {
+        return true;
+    }
+    bool boolean(bool /*val*/) override
+    {
+        return true;
+    }
+    bool number_integer(json::number_integer_t /*val*/) override
+    {
+        return true;
+    }
+    bool number_unsigned(json::number_unsigned_t /*val*/) override
+    {
+        return true;
+    }
+    bool number_float(json::number_float_t val, const json::string_t& s) override
+    {
+        values.push_back(val);
+        strings.push_back(s);
+        return true;
+    }
+    bool string(json::string_t& /*val*/) override
+    {
+        return true;
+    }
+    bool binary(json::binary_t& /*val*/) override
+    {
+        return true;
+    }
+    bool start_object(std::size_t /*val*/) override
+    {
+        return true;
+    }
+    bool key(json::string_t& /*val*/) override
+    {
+        return true;
+    }
+    bool end_object() override
+    {
+        return true;
+    }
+    bool start_array(std::size_t /*val*/) override
+    {
+        switched = std::setlocale(LC_NUMERIC, locale_after_open.c_str()) != nullptr;
+        return true;
+    }
+    bool end_array() override
+    {
+        return true;
+    }
+    bool parse_error(std::size_t /*val*/, const std::string& /*val*/, const nlohmann::detail::exception& /*val*/) override
+    {
+        return false;
+    }
+
+    std::string locale_after_open;
+    bool switched = false;
+    std::vector<json::number_float_t> values {}; // NOLINT(readability-redundant-member-init)
+    std::vector<json::string_t> strings {}; // NOLINT(readability-redundant-member-init)
+};
+} // namespace
+
+TEST_CASE("locale changes between lexer construction and number conversion (#5198)")
+{
+    // The numbers are chosen so that the conversion also takes the strtod
+    // fallback, which honors the locale that is current at conversion time:
+    // too many significant digits for Clinger's fast path, an underflow that
+    // std::from_chars rejects, and a plain value.
+    const std::vector<std::string> numbers = {"3.14159265358979323846", "1.5e-400", "12.34", "-0.000123456789012345678"};
+    std::string text = "[";
+    for (const auto& n : numbers)
+    {
+        text += (text.size() == 1 ? "" : ",") + n;
+    }
+    text += "]";
+
+    using long_double_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, long double>;
+
+    // reference values, parsed without a locale switch
+    REQUIRE(std::setlocale(LC_NUMERIC, "C") != nullptr);
+    const json expected = json::parse(text);
+    const long_double_json expected_ld = long_double_json::parse(text);
+
+    const std::array<std::pair<const char*, const char*>, 2> transitions =
+    {
+        {
+            {"C", "de_DE"},
+            {"de_DE", "C"}
+        }
+    };
+
+    for (const auto& transition : transitions)
+    {
+        CAPTURE(transition.first);
+        CAPTURE(transition.second);
+
+        if (std::setlocale(LC_NUMERIC, transition.first) == nullptr)
+        {
+            MESSAGE("locale is not usable");
+            continue;
+        }
+
+        // SAX parsing
+        {
+            LocaleSwitchingSax sax(transition.second);
+            CHECK(json::sax_parse(text, &sax));
+            if (sax.switched)
+            {
+                CHECK(sax.values == expected.get<std::vector<json::number_float_t>>());
+                CHECK(sax.strings == numbers);
+            }
+        }
+
+        // DOM parsing with a callback
+        {
+            bool switched = false;
+            const auto cb = [&](int /*depth*/, json::parse_event_t event, json& /*parsed*/) noexcept
+            {
+                if (event == json::parse_event_t::array_start)
+                {
+                    switched = std::setlocale(LC_NUMERIC, transition.second) != nullptr;
+                }
+                return true;
+            };
+            const json j = json::parse(text, cb);
+            if (switched)
+            {
+                CHECK(j == expected);
+            }
+        }
+
+        // a long double goes through std::strtold unless std::from_chars supports it
+        {
+            bool switched = false;
+            const auto cb = [&](int /*depth*/, long_double_json::parse_event_t event, long_double_json& /*parsed*/) noexcept
+            {
+                if (event == long_double_json::parse_event_t::array_start)
+                {
+                    switched = std::setlocale(LC_NUMERIC, transition.second) != nullptr;
+                }
+                return true;
+            };
+            const long_double_json j = long_double_json::parse(text, cb);
+            if (switched)
+            {
+                CHECK(j == expected_ld);
+            }
+        }
+    }
+
+    CHECK(std::setlocale(LC_NUMERIC, "C") != nullptr);
+}
+
+TEST_CASE("locale with a multi-byte decimal point")
+{
+    // Some locales use a decimal point that is not a single character, e.g.
+    // U+066B ARABIC DECIMAL SEPARATOR (two bytes in UTF-8). It cannot be
+    // substituted in place for '.', so the strtod fallback stops early. The
+    // conversion must still terminate rather than retry forever.
+    const std::array<const char*, 6> names = {{"ar_EG.UTF-8", "ar_SA.UTF-8", "fa_IR.UTF-8", "ps_AF.UTF-8", "ar_EG", "fa_IR"}};
+    bool tested = false;
+    for (const char* name : names)
+    {
+        if (std::setlocale(LC_NUMERIC, name) == nullptr)
+        {
+            continue;
+        }
+        const std::string decimal_point = std::localeconv()->decimal_point;
+        if (decimal_point.size() < 2)
+        {
+            continue;
+        }
+        CAPTURE(name);
+        tested = true;
+
+        // too many significant digits for Clinger's fast path, and an underflow
+        // that std::from_chars rejects: both reach the strtod fallback
+        json j;
+        CHECK_NOTHROW(j = json::parse("[3.14159265358979323846, 1.5e-400, -0.000123456789012345678]"));
+        CHECK(j.is_array());
+        CHECK(json::accept("3.14159265358979323846"));
+
+        // a value the locale-independent paths convert is not affected
+        CHECK(json::parse("12.5") == 12.5);
+    }
+    if (!tested)
+    {
+        MESSAGE("no locale with a multi-byte decimal point is usable");
+    }
+
+    CHECK(std::setlocale(LC_NUMERIC, "C") != nullptr);
+}

tests/src/unit-modifiers.cpp

@@ -155,6 +155,18 @@ TEST_CASE("modifiers")
                 CHECK(j == json(json::value_t::binary));
                 CHECK(j == json(k.type()));
             }
+
+            SECTION("filled binary with subtype")
+            {
+                json j = json::binary({1, 2, 3, 4, 5}, 42);
+                json const k = j;
+
+                j.clear();
+                CHECK(!j.empty());
+                CHECK(!j.get_binary().has_subtype());
+                CHECK(j == json(json::value_t::binary));
+                CHECK(j == json(k.type()));
+            }
         }
 
         SECTION("number (integer)")
@@ -761,6 +773,34 @@ TEST_CASE("modifiers")
             }
         }
 
+        SECTION("initializer list referring to the array's own elements (#5656)")
+        {
+            SECTION("sufficient capacity (no reallocation)")
+            {
+                json j_own = json::array();
+                j_own.get_ref<json::array_t&>().reserve(8);
+                j_own.push_back("a");
+                j_own.push_back("b");
+                j_own.push_back("c");
+
+                const json& j_own_cref = j_own;
+                auto it = j_own.insert(j_own.begin(), {j_own_cref[0], j_own_cref[1]});
+                CHECK(*it == json("a"));
+                CHECK(j_own == json({"a", "b", "a", "b", "c"}));
+            }
+
+            SECTION("insufficient capacity (reallocation)")
+            {
+                json j_own = {"a", "b", "c"};
+                j_own.get_ref<json::array_t&>().shrink_to_fit();
+
+                const json& j_own_cref = j_own;
+                auto it = j_own.insert(j_own.begin(), {j_own_cref[2]});
+                CHECK(*it == json("c"));
+                CHECK(j_own == json({"c", "a", "b", "c"}));
+            }
+        }
+
         SECTION("invalid iterator")
         {
             // pass iterator to a different array

tests/src/unit-msgpack.cpp

@@ -1551,10 +1551,69 @@ TEST_CASE("MessagePack")
         SECTION("invalid string in map")
         {
             json _;
-            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(std::vector<uint8_t>({0x81, 0xff, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack string: expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0xFF", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(std::vector<uint8_t>({0x81, 0xff, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found an integer; last byte: 0xFF", json::parse_error&);
             CHECK(json::from_msgpack(std::vector<uint8_t>({0x81, 0xff, 0x01}), true, false).is_discarded());
         }
 
+        SECTION("non-string key (see #3381)")
+        {
+            // only strings map to JSON object keys; any other key is rejected
+            // with a message naming its type
+            const std::vector<std::pair<std::vector<std::uint8_t>, std::string>> cases =
+            {
+                {{0x81, 0xC0, 0x01}, "nil; last byte: 0xC0"},
+                {{0x81, 0xC2, 0x01}, "a boolean; last byte: 0xC2"},
+                {{0x81, 0xC3, 0x01}, "a boolean; last byte: 0xC3"},
+                {{0x81, 0xCA, 0x3F, 0x80, 0x00, 0x00, 0x01}, "a float; last byte: 0xCA"},
+                {{0x81, 0xCB, 0x3F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01}, "a float; last byte: 0xCB"},
+                {{0x81, 0xC4, 0x00, 0x01}, "a bin; last byte: 0xC4"},
+                {{0x81, 0xC5, 0x00, 0x00, 0x01}, "a bin; last byte: 0xC5"},
+                {{0x81, 0xC6, 0x00, 0x00, 0x00, 0x00, 0x01}, "a bin; last byte: 0xC6"},
+                {{0x81, 0xC7, 0x00, 0x01, 0x01}, "an ext; last byte: 0xC7"},
+                {{0x81, 0xC8, 0x00, 0x00, 0x01, 0x01}, "an ext; last byte: 0xC8"},
+                {{0x81, 0xC9, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01}, "an ext; last byte: 0xC9"},
+                {{0x81, 0xD4, 0x01, 0x00, 0x01}, "an ext; last byte: 0xD4"},
+                {{0x81, 0xD5, 0x01, 0x00, 0x00, 0x01}, "an ext; last byte: 0xD5"},
+                {{0x81, 0xD6, 0x01, 0x00, 0x00, 0x00, 0x00, 0x01}, "an ext; last byte: 0xD6"},
+                {{0x81, 0xD7, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01}, "an ext; last byte: 0xD7"},
+                {{0x81, 0xD8, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01}, "an ext; last byte: 0xD8"},
+                {{0x81, 0xCC, 0x01, 0x01}, "an integer; last byte: 0xCC"},
+                {{0x81, 0xCD, 0x00, 0x01, 0x01}, "an integer; last byte: 0xCD"},
+                {{0x81, 0xCE, 0x00, 0x00, 0x00, 0x01, 0x01}, "an integer; last byte: 0xCE"},
+                {{0x81, 0xCF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01}, "an integer; last byte: 0xCF"},
+                {{0x81, 0xD0, 0x01, 0x01}, "an integer; last byte: 0xD0"},
+                {{0x81, 0xD1, 0x00, 0x01, 0x01}, "an integer; last byte: 0xD1"},
+                {{0x81, 0xD2, 0x00, 0x00, 0x00, 0x01, 0x01}, "an integer; last byte: 0xD2"},
+                {{0x81, 0xD3, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01}, "an integer; last byte: 0xD3"},
+                {{0x81, 0x00, 0x01}, "an integer; last byte: 0x00"},
+                {{0x81, 0x7F, 0x01}, "an integer; last byte: 0x7F"},
+                {{0x81, 0xE0, 0x01}, "an integer; last byte: 0xE0"},
+                {{0x81, 0x80, 0x01}, "a map; last byte: 0x80"},
+                {{0x81, 0x8F, 0x01}, "a map; last byte: 0x8F"},
+                {{0x81, 0xDE, 0x00, 0x00, 0x01}, "a map; last byte: 0xDE"},
+                {{0x81, 0xDF, 0x00, 0x00, 0x00, 0x00, 0x01}, "a map; last byte: 0xDF"},
+                {{0x81, 0x90, 0x01}, "an array; last byte: 0x90"},
+                {{0x81, 0x9F, 0x01}, "an array; last byte: 0x9F"},
+                {{0x81, 0xDC, 0x00, 0x00, 0x01}, "an array; last byte: 0xDC"},
+                {{0x81, 0xDD, 0x00, 0x00, 0x00, 0x00, 0x01}, "an array; last byte: 0xDD"},
+            };
+
+            for (const auto& c : cases)
+            {
+                CAPTURE(c.first)
+                const std::string expected = "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found " + c.second;
+                json _;
+                CHECK_THROWS_WITH_AS(_ = json::from_msgpack(c.first), expected.c_str(), json::parse_error&);
+                CHECK(json::from_msgpack(c.first, true, false).is_discarded());
+            }
+
+            json _;
+            // the unused byte 0xC1 is still reported as a malformed string
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(std::vector<uint8_t>({0x81, 0xC1, 0x01})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack string: expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0xC1", json::parse_error&);
+            // a missing key is still reported as the end of input
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(std::vector<uint8_t>({0x81})), "[json.exception.parse_error.110] parse error at byte 2: syntax error while parsing MessagePack string: unexpected end of input", json::parse_error&);
+        }
+
         SECTION("invalid UTF-8 in string (see #5529)")
         {
             // a fixstr of length 2 (0xA0 | 2) whose bytes are not valid UTF-8
@@ -2416,3 +2475,60 @@ TEST_CASE("MessagePack lengths beyond UINT32_MAX cannot be serialized")
     }
 #endif
 }
+
+TEST_CASE("MessagePack numbers use the active union member (see #5644)")
+{
+    // when number_integer_t is narrower than number_unsigned_t, to_msgpack()
+    // used to read the union member that was not the active one, writing
+    // wrong bytes for some values; std::int64_t/std::uint64_t (the default
+    // types, where both members have the same width) were not affected
+    using int32_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int32_t, std::uint64_t, double>;
+    using int16_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int16_t, std::uint64_t, double>;
+
+    SECTION("number_integer_t = std::int32_t")
+    {
+        SECTION("6442450944 (uint 64; the low 32 bits used to be sign-extended)")
+        {
+            const int32_json j = 6442450944ULL;
+            CHECK(j.is_number_unsigned());
+
+            std::vector<uint8_t> const expected{0xcf, 0x00, 0x00, 0x00, 0x01, 0x80, 0x00, 0x00, 0x00};
+            const auto result = int32_json::to_msgpack(j);
+            CHECK(result == expected);
+            CHECK(int32_json::from_msgpack(result) == j);
+        }
+
+        SECTION("4294967496 (uint 64; the low 32 bits used to be the whole value)")
+        {
+            const int32_json j = 4294967496ULL;
+            CHECK(j.is_number_unsigned());
+
+            std::vector<uint8_t> const expected{0xcf, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0xc8};
+            const auto result = int32_json::to_msgpack(j);
+            CHECK(result == expected);
+            CHECK(int32_json::from_msgpack(result) == j);
+        }
+    }
+
+    SECTION("number_integer_t = std::int16_t, 98304 (uint 32)")
+    {
+        const int16_json j = 98304ULL;
+        CHECK(j.is_number_unsigned());
+
+        std::vector<uint8_t> const expected{0xce, 0x00, 0x01, 0x80, 0x00};
+        const auto result = int16_json::to_msgpack(j);
+        CHECK(result == expected);
+        CHECK(int16_json::from_msgpack(result) == j);
+    }
+
+    SECTION("default types (std::int64_t/std::uint64_t) are unaffected")
+    {
+        const json j = 4294967496ULL;
+        CHECK(j.is_number_unsigned());
+
+        std::vector<uint8_t> const expected{0xcf, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0xc8};
+        const auto result = json::to_msgpack(j);
+        CHECK(result == expected);
+        CHECK(json::from_msgpack(result) == j);
+    }
+}

tests/src/unit-no_automatic_udls.cpp

@@ -0,0 +1,108 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+// This translation unit checks JSON_NO_AUTOMATIC_UDLS, which keeps
+// <nlohmann/json.hpp> from including <nlohmann/json_literals.hpp> and thereby
+// leaves out the user-defined string literals operator""_json and
+// operator""_json_pointer (see #5294), and that including
+// <nlohmann/json_literals.hpp> afterwards brings them back.
+#define JSON_NO_AUTOMATIC_UDLS 1
+
+#include "doctest_compatibility.h"
+
+#include <cstddef>
+#include <utility>
+
+#include <nlohmann/json.hpp>
+using json = nlohmann::json;
+
+// An argument type whose associated namespace is the library namespace, so
+// argument-dependent lookup of a literal operator called by its function name
+// also searches the inline namespaces nlohmann::literals::json_literals.
+NLOHMANN_JSON_NAMESPACE_BEGIN
+struct no_automatic_udls_probe
+{
+    operator const char* () const // NOLINT(google-explicit-constructor,hicpp-explicit-conversions)
+    {
+        return "";
+    }
+};
+NLOHMANN_JSON_NAMESPACE_END
+
+namespace
+{
+// The calls below use a dependent argument, so a literal operator that is not
+// declared at all is a substitution failure rather than a hard error: lookup is
+// deferred to the point of instantiation, where it considers the declarations
+// visible from here (the global using-declarations of JSON_USE_GLOBAL_UDLS) plus
+// argument-dependent lookup (the literals in the library namespace).
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    template<typename T>
+    using json_udl_t = decltype(operator""_json(std::declval<T>(), std::size_t()));
+
+    template<typename T>
+    using json_pointer_udl_t = decltype(operator""_json_pointer(std::declval<T>(), std::size_t()));
+#else
+    // GCC 4.8 requires a space between "" and suffix
+    template<typename T>
+    using json_udl_t = decltype(operator"" _json(std::declval<T>(), std::size_t()));
+
+    template<typename T>
+    using json_pointer_udl_t = decltype(operator"" _json_pointer(std::declval<T>(), std::size_t()));
+#endif
+
+template<typename T>
+using has_json_udl = nlohmann::detail::is_detected<json_udl_t, T>;
+
+template<typename T>
+using has_json_pointer_udl = nlohmann::detail::is_detected<json_pointer_udl_t, T>;
+} // namespace
+
+TEST_CASE("JSON_NO_AUTOMATIC_UDLS")
+{
+    SECTION("literals are not declared")
+    {
+        // global namespace (JSON_USE_GLOBAL_UDLS defaults to 1)
+        CHECK_FALSE(has_json_udl<const char*>::value);
+        CHECK_FALSE(has_json_pointer_udl<const char*>::value);
+
+        // nlohmann::literals::json_literals
+        CHECK_FALSE(has_json_udl<nlohmann::no_automatic_udls_probe>::value);
+        CHECK_FALSE(has_json_pointer_udl<nlohmann::no_automatic_udls_probe>::value);
+    }
+
+    SECTION("the rest of the library keeps working")
+    {
+        const json j = json::parse(R"({"foo": {"bar": 42}})");
+        CHECK(j.dump() == R"({"foo":{"bar":42}})");
+
+        const json::json_pointer ptr("/foo/bar");
+        CHECK(j.at(ptr) == 42);
+        CHECK(j.contains(ptr));
+    }
+}
+
+// the literals can still be added where they are needed
+#include <nlohmann/json_literals.hpp>
+
+TEST_CASE("JSON_NO_AUTOMATIC_UDLS with <nlohmann/json_literals.hpp>")
+{
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
+    SECTION("global namespace")
+    {
+        CHECK("[1,2]"_json == json({1, 2}));
+        CHECK("/a/0"_json_pointer == json::json_pointer("/a/0"));
+    }
+#endif
+
+    SECTION("nlohmann::literals::json_literals")
+    {
+        using namespace nlohmann::literals::json_literals; // NOLINT(google-build-using-namespace)
+        CHECK(R"({"a":[42]})"_json.at("/a/0"_json_pointer) == 42);
+    }
+}

tests/src/unit-ordered_map.cpp

@@ -11,6 +11,97 @@
 #include <nlohmann/json.hpp>
 using nlohmann::ordered_map;
 
+#include <stdexcept>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+// The EDG front end (Intel icpc, NVIDIA nvc++) considers the defaulted move
+// constructor of std::pair<const Key, T> noexcept even if copying Key can
+// throw. std::vector then moves such elements itself when it grows (and calls
+// std::terminate if a key copy throws), so ordered_map leaves growing to it.
+#if defined(__EDG__)
+    #define JSON_TEST_PAIR_MOVE_IS_NOEXCEPT
+#endif
+
+namespace
+{
+// number of copies made of counted values
+int value_copies = 0;
+
+// a mapped type that counts its copies; moving from it leaves -1 behind
+struct counted // NOLINT(cppcoreguidelines-special-member-functions,hicpp-special-member-functions)
+{
+    int payload = 0;
+
+    counted() = default;
+    explicit counted(int p) noexcept : payload(p) {}
+    counted(const counted& other) : payload(other.payload)
+    {
+        ++value_copies;
+    }
+    counted(counted&& other) noexcept : payload(other.payload)
+    {
+        other.payload = -1;
+    }
+    counted& operator=(const counted&) = delete;
+    counted& operator=(counted&& other) noexcept
+    {
+        payload = other.payload;
+        other.payload = -1;
+        return *this;
+    }
+};
+
+#if !defined(JSON_NOEXCEPTION) && !defined(JSON_TEST_PAIR_MOVE_IS_NOEXCEPT)
+// number of throwing_key copies that still succeed; the next one throws
+// (a negative value means that copies never throw)
+int key_copies_until_throw = -1;
+
+// a key type whose copy constructor can be made to throw
+struct throwing_key // NOLINT(cppcoreguidelines-special-member-functions,hicpp-special-member-functions)
+{
+    int id = 0;
+
+    explicit throwing_key(int i) noexcept : id(i) {}
+    throwing_key(const throwing_key& other) : id(other.id)
+    {
+        if (key_copies_until_throw == 0)
+        {
+            throw std::runtime_error("key copy failed");
+        }
+        if (key_copies_until_throw > 0)
+        {
+            --key_copies_until_throw;
+        }
+    }
+    throwing_key& operator=(const throwing_key&) = delete;
+
+    friend bool operator==(const throwing_key& lhs, const throwing_key& rhs) noexcept
+    {
+        return lhs.id == rhs.id;
+    }
+};
+#endif
+
+// a mapped type that cannot be default-constructed
+struct no_default
+{
+    explicit no_default(int v) noexcept : value(v) {}
+    int value;
+};
+
+// ordered_json must keep moving its values when an object grows
+using ordered_object_t = nlohmann::ordered_json::object_t;
+#if !defined(JSON_TEST_PAIR_MOVE_IS_NOEXCEPT)
+    static_assert(!std::is_nothrow_move_constructible<ordered_object_t::value_type>::value, "std::vector would move the elements itself");
+#endif
+static_assert(std::is_copy_constructible<ordered_object_t::key_type>::value, "keys must be copyable");
+static_assert(std::is_default_constructible<ordered_object_t::mapped_type>::value, "values must be default-constructible");
+static_assert(std::is_nothrow_move_assignable<ordered_object_t::mapped_type>::value, "values must be nothrow move-assignable");
+} // namespace
+
 TEST_CASE("ordered_map")
 {
     SECTION("constructor")
@@ -313,3 +404,270 @@ TEST_CASE("ordered_map")
         }
     }
 }
+
+TEST_CASE("ordered_map growth")
+{
+    SECTION("values are moved, not copied, when the storage grows")
+    {
+        ordered_map<std::string, counted> om;
+        std::size_t growths = 0;
+        value_copies = 0;
+
+        // inserts 100 elements with the given function and counts the growths
+        const auto fill = [&om, &growths](void (*insert)(ordered_map<std::string, counted>&, int))
+        {
+            for (int i = 0; i < 100; ++i)
+            {
+                const auto old_capacity = om.capacity();
+                insert(om, i);
+                if (om.capacity() > old_capacity)
+                {
+                    ++growths;
+                }
+            }
+        };
+
+        // checks that the elements are in insertion order with their values
+        const auto check_contents = [&om]
+        {
+            CHECK(om.size() == 100);
+            int i = 0;
+            for (const auto& element : om)
+            {
+                CHECK(element.first == std::to_string(i));
+                CHECK(element.second.payload == i);
+                ++i;
+            }
+        };
+
+        SECTION("emplace")
+        {
+            fill([](ordered_map<std::string, counted>& m, int i)
+            {
+                m.emplace(std::to_string(i), counted(i));
+            });
+            CHECK(growths >= 3);
+            CHECK(value_copies == 0);
+            check_contents();
+        }
+
+        SECTION("operator[]")
+        {
+            fill([](ordered_map<std::string, counted>& m, int i)
+            {
+                m[std::to_string(i)] = counted(i);
+            });
+            CHECK(growths >= 3);
+            CHECK(value_copies == 0);
+            check_contents();
+        }
+
+        SECTION("insert(value_type&&)")
+        {
+            fill([](ordered_map<std::string, counted>& m, int i)
+            {
+                m.insert({std::to_string(i), counted(i)});
+            });
+            CHECK(growths >= 3);
+            CHECK(value_copies == 0);
+            check_contents();
+        }
+
+        SECTION("insert(const value_type&)")
+        {
+            fill([](ordered_map<std::string, counted>& m, int i)
+            {
+                const std::pair<const std::string, counted> value(std::to_string(i), counted(i));
+                m.insert(value);
+            });
+            CHECK(growths >= 3);
+            // only the inserted values are copied
+            CHECK(value_copies == 100);
+            check_contents();
+        }
+
+        SECTION("insert(first, last)")
+        {
+            std::vector<std::pair<const std::string, counted>> values;
+            values.reserve(100);
+            for (int i = 0; i < 100; ++i)
+            {
+                values.emplace_back(std::to_string(i), counted(i));
+            }
+            value_copies = 0;
+
+            om.insert(values.cbegin(), values.cend());
+            // only the inserted values are copied
+            CHECK(value_copies == 100);
+            check_contents();
+        }
+    }
+
+    SECTION("elements keep their order and values over many growths")
+    {
+        ordered_map<std::string, counted> om;
+        for (int i = 0; i < 1000; ++i)
+        {
+            om.emplace(std::to_string(i), counted(i));
+        }
+
+        CHECK(om.size() == 1000);
+        int i = 0;
+        for (const auto& element : om)
+        {
+            CHECK(element.first == std::to_string(i));
+            CHECK(element.second.payload == i);
+            ++i;
+        }
+    }
+
+    SECTION("arguments may refer to elements of the full container")
+    {
+        SECTION("moving a value out of the container")
+        {
+            ordered_map<std::string, counted> om;
+            om.reserve(4);
+            while (om.size() < om.capacity())
+            {
+                const auto i = static_cast<int>(om.size());
+                om.emplace(std::to_string(i), counted(i));
+            }
+            const auto size = om.size();
+
+            om.emplace("new", std::move(om.at("0")));
+            CHECK(om.size() == size + 1);
+            CHECK(om.at("new").payload == 0);
+            CHECK(om.at("0").payload == -1);
+        }
+
+        SECTION("using a value as key")
+        {
+            ordered_map<std::string, std::string> om;
+            om.reserve(4);
+            while (om.size() < om.capacity())
+            {
+                const auto i = std::to_string(om.size());
+                om.emplace("k" + i, "v" + i);
+            }
+            const auto size = om.size();
+
+            om.emplace(om.at("k0"), std::string("x"));
+            CHECK(om.size() == size + 1);
+            CHECK(om.at("k0") == "v0");
+            CHECK(om.at("v0") == "x");
+        }
+
+        SECTION("ordered_json")
+        {
+            auto j = nlohmann::ordered_json::object();
+            auto& object = j.get_ref<nlohmann::ordered_json::object_t&>();
+            object.reserve(4);
+            while (object.size() < object.capacity())
+            {
+                const auto i = std::to_string(object.size());
+                j[i] = "a value that is too long for the small string optimization " + i;
+            }
+            const auto size = j.size();
+
+            j.emplace("new", std::move(j["0"]));
+            CHECK(j.size() == size + 1);
+            CHECK(j["new"] == "a value that is too long for the small string optimization 0");
+            CHECK(j["0"].is_null());
+        }
+    }
+
+#if !defined(JSON_NOEXCEPTION) && !defined(JSON_TEST_PAIR_MOVE_IS_NOEXCEPT)
+    SECTION("the container is unchanged if growing it throws")
+    {
+        ordered_map<throwing_key, counted> om;
+        om.reserve(4);
+        while (om.size() < om.capacity())
+        {
+            const auto i = static_cast<int>(om.size());
+            om.emplace(throwing_key(i), counted(i));
+        }
+        const auto size = om.size();
+        const auto capacity = om.capacity();
+
+        // checks that the elements are unchanged
+        const auto check_unchanged = [&om, size, capacity]
+        {
+            CHECK(om.size() == size);
+            CHECK(om.capacity() == capacity);
+            int i = 0;
+            for (const auto& element : om)
+            {
+                CHECK(element.first.id == i);
+                CHECK(element.second.payload == i);
+                ++i;
+            }
+        };
+
+        SECTION("emplace")
+        {
+            // growing copies the existing keys and then the new one; let each of these copies throw
+            for (std::size_t k = 0; k <= size; ++k)
+            {
+                counted value(100);
+                key_copies_until_throw = static_cast<int>(k);
+                CHECK_THROWS_AS(om.emplace(throwing_key(100), std::move(value)), std::runtime_error);
+                key_copies_until_throw = -1;
+
+                check_unchanged();
+                CHECK(value.payload == 100); // NOLINT(bugprone-use-after-move,hicpp-invalid-access-moved)
+            }
+
+            om.emplace(throwing_key(100), counted(100));
+            CHECK(om.size() == size + 1);
+            CHECK(om.capacity() > capacity);
+            CHECK(om.at(throwing_key(100)).payload == 100);
+        }
+
+        SECTION("insert(const value_type&)")
+        {
+            const std::pair<const throwing_key, counted> value(throwing_key(100), counted(100));
+            value_copies = 0;
+
+            key_copies_until_throw = static_cast<int>(size / 2);
+            CHECK_THROWS_AS(om.insert(value), std::runtime_error);
+            key_copies_until_throw = -1;
+
+            check_unchanged();
+            CHECK(value_copies == 0);
+        }
+    }
+#endif
+
+    SECTION("elements that std::vector moves, or that cannot be moved back")
+    {
+        SECTION("nothrow move-constructible elements")
+        {
+            ordered_map<int, counted> om;
+            value_copies = 0;
+            for (int i = 0; i < 100; ++i)
+            {
+                om.emplace(i, counted(i));
+            }
+            CHECK(om.size() == 100);
+            CHECK(value_copies == 0);
+        }
+
+        SECTION("mapped type without default constructor")
+        {
+            ordered_map<std::string, no_default> om;
+            for (int i = 0; i < 100; ++i)
+            {
+                om.emplace(std::to_string(i), no_default(i));
+            }
+
+            CHECK(om.size() == 100);
+            int i = 0;
+            for (const auto& element : om)
+            {
+                CHECK(element.first == std::to_string(i));
+                CHECK(element.second.value == i);
+                ++i;
+            }
+        }
+    }
+}

tests/src/unit-precise-stream-position.cpp

@@ -234,4 +234,33 @@ TEST_CASE("JSON_PRECISE_STREAM_POSITION")
         CHECK(j == json(1));
         CHECK(remaining(is) == "true");
     }
+
+    SECTION("stream with eofbit in its exception mask (issue #5646)")
+    {
+        // with JSON_PRECISE_STREAM_POSITION, get_character() peeks via
+        // sb->sgetc() rather than consuming via sb->sbumpc(), but it still
+        // calls std::istream::clear() to record eofbit once the streambuf is
+        // exhausted; with eofbit in the exception mask, that clear() itself
+        // throws std::ios_base::failure, which must propagate to the caller
+        // instead of ~input_stream_adapter() throwing a second exception
+        // while the first is still unwinding (which would call std::terminate)
+        json _;
+
+        std::istringstream is1("1");
+        is1.exceptions(std::ios::eofbit);
+        CHECK_THROWS_AS(_ = json::parse(is1), std::ios_base::failure&);
+
+        std::istringstream is2("1");
+        is2.exceptions(std::ios::failbit | std::ios::badbit | std::ios::eofbit);
+        CHECK_THROWS_AS(_ = json::parse(is2), std::ios_base::failure&);
+    }
+
+    SECTION("stream without a streambuf (issue #5646)")
+    {
+        // std::istream(nullptr) has badbit set and rdbuf() == nullptr;
+        // get_character() must not dereference that null streambuf
+        std::istream is(nullptr);
+        json _;
+        CHECK_THROWS_WITH_AS(_ = json::parse(is), "[json.exception.parse_error.101] parse error: attempting to parse an empty input; check that your input string or stream contains the expected JSON", json::parse_error&);
+    }
 }

tests/src/unit-regression1.cpp

@@ -1018,7 +1018,7 @@ TEST_CASE("regression tests 1")
         };
 
         json _;
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(vec), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x98", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(vec), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found an array; last byte: 0x98", json::parse_error&);
 
         // related test case: nonempty UTF-8 string (indefinite length)
         std::vector<uint8_t> const vec1 {0x7f, 0x61, 0x61};
@@ -1065,7 +1065,7 @@ TEST_CASE("regression tests 1")
         };
 
         json _;
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(vec1), "[json.exception.parse_error.113] parse error at byte 13: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xB4", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(vec1), "[json.exception.parse_error.113] parse error at byte 13: syntax error while parsing CBOR object key: only string keys are supported, but found a map; last byte: 0xB4", json::parse_error&);
 
         // related test case: double-precision
         std::vector<uint8_t> const vec2
@@ -1077,7 +1077,7 @@ TEST_CASE("regression tests 1")
             0x96, 0x96, 0xb4, 0xb4, 0xfa, 0x94, 0x94, 0x61,
             0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0xfb
         };
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(vec2), "[json.exception.parse_error.113] parse error at byte 13: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xB4", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(vec2), "[json.exception.parse_error.113] parse error at byte 13: syntax error while parsing CBOR object key: only string keys are supported, but found a map; last byte: 0xB4", json::parse_error&);
     }
 
     SECTION("issue #452 - Heap-buffer-overflow (OSS-Fuzz issue 585)")

tools/amalgamate/CHANGES.md

@@ -8,3 +8,6 @@ The following changes have been made to the code with respect to <https://github
   - membership check
   - made function from `_is_within`
   - removed unused variable `actual_path`
+- Added the optional config key `external`: include paths listed there are kept as
+  `#include` directives instead of being inlined (the first directive per path; the
+  repeated ones are commented out).

tools/amalgamate/README.md

@@ -57,6 +57,11 @@ Python v.2.7.0 or higher is required.
    amalgamation. Have a look at `test/source.c.json` and `test/include.h.json`
    to see two examples.
 
+   The optional `external` list names include paths that are kept as `#include`
+   directives instead of being inlined, e.g. `["nlohmann/json.hpp"]` for a header
+   that includes another amalgamated header. Only the first directive for each
+   of these paths is kept; the repeated ones are commented out.
+
  * The `-s, --source` option should specify the path to the source directory.
    This is useful for supporting separate source and build directories.
 

tools/amalgamate/amalgamate.py

@@ -62,6 +62,10 @@ class Amalgamation(object):
         return None
 
     def __init__(self, args):
+        # include paths that are kept as #include directives instead of
+        # being inlined (e.g. a header amalgamated on its own)
+        self.external = []
+        self.included_external = []
         with open(args.config, 'r') as f:
             config = json.loads(f.read())
             for key in config:
@@ -220,11 +224,14 @@ class TranslationUnit(object):
         while include_match:
             if not _is_within(include_match, skippable_contexts):
                 include_path = include_match.group("path")
-                search_same_dir = include_match.group(1) == '"'
-                found_included_path = self.amalgamation.find_included_file(
-                    include_path, self.file_dir if search_same_dir else None)
-                if found_included_path:
-                    includes.append((include_match, found_included_path))
+                if include_path in self.amalgamation.external:
+                    includes.append((include_match, None))
+                else:
+                    search_same_dir = include_match.group(1) == '"'
+                    found_included_path = self.amalgamation.find_included_file(
+                        include_path, self.file_dir if search_same_dir else None)
+                    if found_included_path:
+                        includes.append((include_match, found_included_path))
 
             include_match = self.include_pattern.search(self.content,
                                                         include_match.end())
@@ -235,6 +242,17 @@ class TranslationUnit(object):
         for include in includes:
             include_match, found_included_path = include
             tmp_content += self.content[prev_end:include_match.start()]
+            if found_included_path is None:
+                # an external header: keep the first directive and comment
+                # out the repeated ones
+                include_path = include_match.group("path")
+                if include_path in self.amalgamation.included_external:
+                    tmp_content += "// {0}".format(include_match.group(0))
+                else:
+                    self.amalgamation.included_external.append(include_path)
+                    tmp_content += include_match.group(0)
+                prev_end = include_match.end()
+                continue
             tmp_content += "// {0}\n".format(include_match.group(0))
             if found_included_path not in self.amalgamation.included_files:
                 t = TranslationUnit(found_included_path, self.amalgamation, False)

tools/amalgamate/config_json_view.json

@@ -0,0 +1,9 @@
+{
+	"project": "JSON for Modern C++",
+	"target": "single_include/nlohmann/json_view.hpp",
+	"sources": [
+		"include/nlohmann/json_view.hpp"
+	],
+	"include_paths": ["include"],
+	"external": ["nlohmann/json.hpp"]
+}

tools/generate_natvis/nlohmann_json.natvis.j2

@@ -36,31 +36,5 @@
         </Expand>
     </Type>
 
-    <!-- Fallback for when the basic_json entry above does not match: json_default_base is the (empty) default
-         base class of basic_json, and base class visualizers are inherited by derived types and evaluated
-         against the derived object, so m_data is accessible here. The class lives in {{ ns }} after
-         3.12.0 (#5238) and in {{ ns }}::detail up to 3.12.0, so both names are listed. -->
-{% for default_base in ['json_default_base', 'detail::json_default_base'] %}
-    <Type Name="{{ ns }}::{{ default_base }}">
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::null">null</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
-        <DisplayString Condition="m_data.m_type == {{ ns }}::detail::value_t::discarded">discarded</DisplayString>
-        <Expand>
-            <ExpandedItem Condition="m_data.m_type == {{ ns }}::detail::value_t::object">
-                *(m_data.m_value.object),view(simple)
-            </ExpandedItem>
-            <ExpandedItem Condition="m_data.m_type == {{ ns }}::detail::value_t::array">
-                *(m_data.m_value.array),view(simple)
-            </ExpandedItem>
-        </Expand>
-    </Type>
-
-{% endfor %}
 {% endfor %}
 </AutoVisualizer>