Merge branch 'develop' into claude/compile-time-docs

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

@@ -65,6 +65,7 @@ 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

@@ -363,7 +363,7 @@ std::cout << j_string << " == " << serialized_string << std::endl;
 
 [`.dump()`](https://json.nlohmann.me/api/basic_json/dump/) returns the originally stored string value.
 
-Note the library only supports UTF-8. When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace`, `json::error_handler_t::ignore`, or `json::error_handler_t::keep` are used as error handlers.
+Note the library only supports UTF-8. When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers.
 
 #### To/from streams (e.g., files, string streams)
 
@@ -1915,7 +1915,7 @@ The library supports **Unicode input** as follows:
 - [Unicode noncharacters](https://www.unicode.org/faq/private_use.html#nonchar1) will not be replaced by the library.
 - Invalid surrogates (e.g., incomplete pairs such as `\uDEAD`) will yield parse errors.
 - The strings stored in the library are UTF-8 encoded. When using the default string type (`std::string`), note that its length/size functions return the number of stored bytes rather than the number of characters or glyphs.
-- When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace`, `json::error_handler_t::ignore`, or `json::error_handler_t::keep` are used as error handlers.
+- When you store strings with different encodings in the library, calling [`dump()`](https://json.nlohmann.me/api/basic_json/dump/) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers.
 - To store wide strings (e.g., `std::wstring`), you need to convert them to a UTF-8 encoded `std::string` before, see [an example](https://json.nlohmann.me/home/faq/#wide-string-handling).
 
 ### Comments in JSON

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/dump.md

@@ -25,15 +25,10 @@ and `ensure_ascii` parameters.
     result consists of ASCII characters only.
 
 `error_handler` (in)
-:   how to react on decoding errors; there are four possible values (see [`error_handler_t`](error_handler_t.md)):
+:   how to react on decoding errors; there are three possible values (see [`error_handler_t`](error_handler_t.md):
-
+    `strict` (throws an exception in case a decoding error occurs; default), `replace` (replace invalid UTF-8 sequences
-    - `strict`: throw a [`type_error`](../../home/exceptions.md#type-errors) exception in case a decoding error occurs
+    with U+FFFD), and `ignore` (ignore invalid UTF-8 sequences during serialization; all valid bytes are copied to the
-      (default),
+    output unchanged, and invalid bytes are dropped)).
-    - `replace`: replace invalid UTF-8 sequences with U+FFFD (� REPLACEMENT CHARACTER),
-    - `ignore`: ignore invalid UTF-8 sequences during serialization; all valid bytes are copied to the output unchanged,
-      and invalid bytes are dropped, and
-    - `keep`: keep invalid UTF-8 sequences during serialization; all bytes are copied to the output unchanged, so the
-      result is not valid UTF-8.
     
 ## Return value
 
@@ -99,4 +94,3 @@ Binary values are serialized as an object containing two keys:
 - Indentation character `indent_char`, option `ensure_ascii` and exceptions added in version 3.0.0.
 - Error handlers added in version 3.4.0.
 - Serialization of binary values added in version 3.8.0.
-- Error handler value `keep` added in version 3.13.0.

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

@@ -4,13 +4,12 @@
 enum class error_handler_t {
     strict,
     replace,
-    ignore,
+    ignore
-    keep
 };
 ```
 
 This enumeration is used in the [`dump`](dump.md) function to choose how to treat decoding errors while serializing a
-`basic_json` value. Four values are differentiated:
+`basic_json` value. Three values are differentiated:
 
 strict
 :   throw a `type_error` exception in case of invalid UTF-8
@@ -21,12 +20,6 @@ replace
 ignore
 :   ignore invalid UTF-8 sequences; all valid bytes are copied to the output unchanged, and invalid bytes are dropped
 
-keep
-:   keep invalid UTF-8 sequences; all bytes are copied to the output unchanged. Valid characters are still escaped as
-    usual (e.g., `"`, `\\`, and control characters), so the result has valid JSON syntax, but it is not valid UTF-8.
-    In particular, [`parse`](parse.md) rejects it, and with `ensure_ascii` set to `true`, the invalid bytes are the
-    only non-ASCII bytes of the output.
-
 ## Examples
 
 ??? example
@@ -47,4 +40,3 @@ keep
 ## Version history
 
 - Added in version 3.4.0.
-- Added value `keep` in version 3.13.0.

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,
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a map key is not a string (keys of other
-  but not found
+  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,
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a map key is not a string (keys of other
-  but not found
+  types are not supported, as JSON object keys are always strings) or a string is malformed
 
 ## Complexity
 

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 +1,69 @@
+# 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
+- [Compile times](../../integration/compile_times.md) - options to reduce compile times
+
+## Version history
+
+- Added in version 3.13.0.

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_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/examples/error_handler_t.cpp

@@ -1,4 +1,3 @@
-#include <iomanip>
 #include <iostream>
 #include <nlohmann/json.hpp>
 
@@ -22,12 +21,4 @@ int main()
               << "\nstring with ignored invalid characters: "
               << j_invalid.dump(-1, ' ', false, json::error_handler_t::ignore)
               << '\n';
-
-    // the invalid byte is kept; print the result byte-wise to make it visible
-    std::cout << "string with kept invalid characters:";
-    for (const unsigned char c : j_invalid.dump(-1, ' ', false, json::error_handler_t::keep))
-    {
-        std::cout << ' ' << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(c);
-    }
-    std::cout << '\n';
 }

docs/mkdocs/docs/examples/error_handler_t.output

@@ -1,4 +1,3 @@
 [json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9
 string with replaced invalid characters: "ä�ü"
 string with ignored invalid characters: "äü"
-string with kept invalid characters: 22 c3 a4 a9 c3 bc 22

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/serialization.md

@@ -64,7 +64,6 @@ serialization fails by default. The fourth argument of `dump` selects an
 - `strict` (default) — throw a [`type_error.316`](../home/exceptions.md#jsonexceptiontype_error316) exception.
 - `replace` — replace invalid bytes with the Unicode replacement character U+FFFD (`�`).
 - `ignore` — silently drop invalid bytes.
-- `keep` — copy invalid bytes to the output unchanged; the result is not valid UTF-8.
 
 ??? example
 

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
@@ -755,7 +762,6 @@ The `dump()` function only works with UTF-8 encoded strings; that is, if you ass
     - Pass an error handler as last parameter to the `dump()` function to avoid this exception:
         - `json::error_handler_t::replace` will replace invalid bytes sequences with `U+FFFD` 
         - `json::error_handler_t::ignore` will silently ignore invalid byte sequences
-        - `json::error_handler_t::keep` will copy invalid byte sequences to the output unchanged
 
 ### json.exception.type_error.317
 

docs/mkdocs/docs/home/faq.md

@@ -85,7 +85,7 @@ The library supports **Unicode input** as follows:
 - The library will not replace [Unicode noncharacters](http://www.unicode.org/faq/private_use.html#nonchar1).
 - Invalid surrogates (e.g., incomplete pairs such as `\uDEAD`) will yield parse errors.
 - The strings stored in the library are UTF-8 encoded. When using the default string type (`std::string`), note that its length/size functions return the number of stored bytes rather than the number of characters or glyphs.
-- When you store strings with different encodings in the library, calling [`dump()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a50ec80b02d0f3f51130d4abb5d1cfdc5.html#a50ec80b02d0f3f51130d4abb5d1cfdc5) may throw an exception unless `json::error_handler_t::replace`, `json::error_handler_t::ignore`, or `json::error_handler_t::keep` are used as error handlers.
+- When you store strings with different encodings in the library, calling [`dump()`](https://nlohmann.github.io/json/classnlohmann_1_1basic__json_a50ec80b02d0f3f51130d4abb5d1cfdc5.html#a50ec80b02d0f3f51130d4abb5d1cfdc5) may throw an exception unless `json::error_handler_t::replace` or `json::error_handler_t::ignore` are used as error handlers.
 
 In most cases, the parser is right to complain, because the input is not UTF-8 encoded. This is especially true for Microsoft Windows, where Latin-1 or ISO 8859-1 is often the standard encoding.
 

docs/mkdocs/docs/integration/compile_times.md

@@ -0,0 +1,149 @@
+# Compile times
+
+The library is header-only and makes heavy use of templates, so every translation unit that includes
+`<nlohmann/json.hpp>` pays for parsing the header and instantiating what it uses. This page lists the options to reduce
+that cost, ordered by how much they typically save.
+
+!!! info "Measurements"
+
+    The numbers below are medians of nine runs compiling a single translation unit with `-std=c++17 -c` against the
+    single-header version, with Apple clang and GCC 16 on macOS (Apple silicon). They show the order of magnitude to
+    expect; measure your own code before and after a change.
+
+## Include `json_fwd.hpp` in headers
+
+Header files that only need to *name* the `json` type — for function declarations, members held by pointer or
+reference, or friend declarations — can include `<nlohmann/json_fwd.hpp>` instead of `<nlohmann/json.hpp>`. It only
+forward-declares `basic_json`, `json`, `ordered_json`, `json_pointer`, and `adl_serializer`. The translation units that
+actually use the values then include `<nlohmann/json.hpp>`.
+
+```cpp title="person.hpp"
+#pragma once
+#include <nlohmann/json_fwd.hpp>
+
+struct person;
+void to_json(nlohmann::json& j, const person& p);
+void from_json(const nlohmann::json& j, person& p);
+```
+
+```cpp title="person.cpp"
+#include "person.hpp"
+#include <nlohmann/json.hpp>
+
+void to_json(nlohmann::json& j, const person& p) { /* ... */ }
+void from_json(const nlohmann::json& j, person& p) { /* ... */ }
+```
+
+| Compiler    | `json.hpp` (`-O0`) | `json_fwd.hpp` (`-O0`) | Change |
+|-------------|-------------------:|-----------------------:|-------:|
+| Apple clang |             704 ms |                 329 ms |   −53% |
+| GCC 16      |             779 ms |                 242 ms |   −69% |
+
+This is the most effective option, because it avoids the full header in every translation unit that includes
+*your* headers.
+
+## Opt out of the automatic user-defined string literals
+
+The user-defined string literals [`operator""_json`](../api/operator_literal_json.md) and
+[`operator""_json_pointer`](../api/operator_literal_json_pointer.md) are ordinary inline functions whose bodies call the
+parser. As `<nlohmann/json.hpp>` includes them by default, every translation unit instantiates the parser, even if it
+never parses anything itself.
+
+Define [`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md) for the whole project and include
+`<nlohmann/json_literals.hpp>` only in the files that use the literals:
+
+```cmake
+target_compile_definitions(my_target PRIVATE JSON_NO_AUTOMATIC_UDLS)
+```
+
+```cpp
+#include <nlohmann/json.hpp>
+#include <nlohmann/json_literals.hpp> // only where "..."_json is used
+```
+
+The saving applies to translation units that do not parse JSON, for example ones that define types and their
+conversions or only pass `json` values around:
+
+| Compiler    | Translation unit | Default (`-O0` / `-O2`) | `JSON_NO_AUTOMATIC_UDLS` (`-O0` / `-O2`) | Change      |
+|-------------|------------------|------------------------:|-----------------------------------------:|------------:|
+| Apple clang | model            |         776 ms / 846 ms |                          629 ms / 692 ms | −19% / −18% |
+| GCC 16      | model            |       1022 ms / 1120 ms |                          882 ms / 965 ms | −14% / −14% |
+| Apple clang | parsing          |       992 ms / 1815 ms |                        1006 ms / 1823 ms |   +1% / 0% |
+| GCC 16      | parsing          |      2018 ms / 3420 ms |                        1990 ms / 3454 ms |   −1% / +1% |
+
+Translation units that include only the header save up to a third. Translation units that parse anyway instantiate
+the parser regardless and see no difference.
+
+## Instantiate `basic_json` once
+
+Each translation unit instantiates the member functions of `nlohmann::json` it uses. An explicit instantiation
+declaration tells the compiler that the non-template members are instantiated elsewhere, so it can skip them:
+
+```cpp title="json_instance.hpp"
+#pragma once
+#include <nlohmann/json.hpp>
+
+extern template class nlohmann::basic_json<>;
+```
+
+```cpp title="json_instance.cpp"
+#include "json_instance.hpp"
+
+template class nlohmann::basic_json<>;
+```
+
+Include `json_instance.hpp` instead of `<nlohmann/json.hpp>` and compile and link `json_instance.cpp` once.
+
+| Compiler    | Translation unit    | Default (`-O0` / `-O2`) | `extern template` (`-O0` / `-O2`) | Change      |
+|-------------|---------------------|------------------------:|----------------------------------:|------------:|
+| Apple clang | parsing             |        992 ms / 1815 ms |                  953 ms / 1625 ms |  −4% / −10% |
+| GCC 16      | parsing             |       2018 ms / 3420 ms |                 1522 ms / 2728 ms | −25% / −20% |
+| Apple clang | `json_instance.cpp` |                       — |                 2166 ms / 4660 ms |           — |
+| GCC 16      | `json_instance.cpp` |                       — |                5085 ms / 10616 ms |           — |
+
+Notes:
+
+- The saving grows with the number of translation units that use `json`, while the instantiation translation unit is
+  compiled only once (and is rarely recompiled, as it does not depend on your code).
+- Member function templates (such as `get<T>()`, `parse(InputType&&)`, or `value(key, default)`) are not covered by
+  the explicit instantiation and are still instantiated where they are used.
+- The declaration covers exactly `nlohmann::json`. Add the same lines for `nlohmann::ordered_json`
+  (`nlohmann::basic_json<nlohmann::ordered_map>`) or your own `basic_json` specializations if you use them.
+
+## Use C++20 modules
+
+With a toolchain that supports named modules, `import nlohmann.json;` compiles the library once into a module and
+avoids parsing the header in every translation unit. See [Modules](../features/modules.md) for requirements and known
+issues. Module support is experimental and currently depends heavily on the compiler version.
+
+## Use precompiled headers
+
+Build systems can precompile `<nlohmann/json.hpp>` together with other stable headers, for example with CMake's
+[`target_precompile_headers`](https://cmake.org/cmake/help/latest/command/target_precompile_headers.html):
+
+```cmake
+target_precompile_headers(my_target PRIVATE <nlohmann/json.hpp>)
+```
+
+This removes the cost of parsing the header, but not of instantiating templates in each translation unit, so it
+combines well with the options above.
+
+## Options without effect on compile times
+
+Some configuration macros change what the library declares, but do not measurably change compile times:
+
+| Macro                                                                  | Apple clang, model (`-O0` / `-O2`) | GCC 16, model (`-O0` / `-O2`) |
+|------------------------------------------------------------------------|-----------------------------------:|------------------------------:|
+| default                                                                |                    776 ms / 846 ms |             1022 ms / 1120 ms |
+| [`JSON_NO_IO`](../api/macros/json_no_io.md)                            |                    764 ms / 836 ms |             1022 ms / 1117 ms |
+| [`JSON_USE_GLOBAL_UDLS`](../api/macros/json_use_global_udls.md)`=0`    |                    763 ms / 852 ms |             1019 ms / 1106 ms |
+
+`JSON_USE_GLOBAL_UDLS` only controls *where* the literals are declared; to avoid their cost, use
+`JSON_NO_AUTOMATIC_UDLS` instead.
+
+## See also
+
+- [`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md) - do not include the user-defined string
+  literals automatically
+- [Modules](../features/modules.md) - C++20 module support
+- [Header only](index.md) - including the library

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 (see [Compile times](compile_times.md)), 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

@@ -106,6 +106,7 @@ nav:
       - integration/cmake.md
       - integration/package_managers.md
       - integration/pkg-config.md
+      - integration/compile_times.md
   - API Documentation:
       - basic_json:
           - 'Overview': api/basic_json/index.md
@@ -293,6 +294,7 @@ 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/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/lexer.hpp

@@ -206,7 +206,6 @@ 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_)
     {}
 
@@ -222,8 +221,7 @@ class lexer : public lexer_base<BasicJsonType>
     // locales
     /////////////////////
 
-    /// return the locale-dependent decimal point
+    /// return the decimal point of the current locale
-    JSON_HEDLEY_PURE
     static char get_decimal_point() noexcept
     {
         const auto* loc = localeconv();
@@ -1092,9 +1090,10 @@ 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
+    @note The scanner is independent of the current locale: token_buffer
-          locale's decimal point is used instead of `.` to work with the
+          always holds `.`. Only the std::strtod fallback of convert_number()
-          locale-dependent converters.
+          depends on the locale, and it looks up the decimal point right
+          before converting (see 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 +1182,7 @@ scan_number_zero:
         {
             case '.':
             {
-                add(decimal_point_char);
+                add(current);
                 decimal_point_position = token_buffer.size() - 1;
                 goto scan_number_decimal1;
             }
@@ -1220,7 +1219,7 @@ scan_number_any1:
 
             case '.':
             {
-                add(decimal_point_char);
+                add(current);
                 decimal_point_position = token_buffer.size() - 1;
                 goto scan_number_decimal1;
             }
@@ -1462,9 +1461,9 @@ scan_number_done:
 
         // 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
+        // answer - so this loop is skipped for all but a few tokens. The
-        // token_buffer holds the locale's decimal point, so the fraction is
+        // fraction is located through decimal_point_position rather than by
-        // located through decimal_point_position rather than by searching '.'.
+        // searching '.'.
         if (lead_zero != 0)
         {
             JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
@@ -1482,8 +1481,8 @@ scan_number_done:
     @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
+    scan_number() state machine or by the contiguous fast path) and holds '.'
-    locale decimal point in place of '.'. Integers are parsed first and fall
+    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.
 
@@ -1563,7 +1562,7 @@ 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.
+        // locale-aware strtof/strtod/strtold.
         if (parse_float_from_chars(num_begin, num_end, value_float))
         {
             return token_type::value_float;
@@ -1572,26 +1571,75 @@ scan_number_done:
         // 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))
+                && parse_float_fast(num_begin, num_end, value_float))
         {
             return token_type::value_float;
         }
 
-        char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+        convert_float_locale_aware();
-        strtof(value_float, token_buffer.data(), &endptr);
-
-        // we checked the number format before
-        JSON_ASSERT(endptr == token_buffer.data() + token_buffer.size());
-
         return token_type::value_float;
     }
 
+    /*!
+    @brief convert the float in token_buffer 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.
+    */
+    void convert_float_locale_aware()
+    {
+        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_buffer[decimal_point_position] = static_cast<typename string_t::value_type>(decimal_point);
+            }
+
+            char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            strtof(value_float, token_buffer.data(), &endptr);
+
+            if (substitute)
+            {
+                // get_string() hands the token to the SAX interface with '.'
+                token_buffer[decimal_point_position] = '.';
+            }
+
+            if (JSON_HEDLEY_LIKELY(endptr == token_buffer.data() + token_buffer.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;
+        }
+    }
+
     /*!
     @brief contiguous fast path for scanning a number
 
     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 +1755,11 @@ scan_number_done:
         }
 #endif
 
-        // materialize the token exactly as scan_number() would, substituting the
+        // materialize the token exactly as scan_number() would. reset() already
-        // locale decimal point so convert_number()'s strtof fallback stays valid.
+        // cleared token_buffer, so append() fills it (assign() is avoided
-        // reset() already cleared token_buffer, so append() fills it (assign() is
+        // because custom string_t types need not provide it)
-        // 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)
+        decimal_point_position = dot_index;
-        {
-            token_buffer[dot_index] = static_cast<typename string_t::value_type>(decimal_point_char);
-            decimal_point_position = dot_index;
-        }
 
         ia.bulk_skip(len - 1);
         position.chars_read_total += (len - 1);
@@ -1983,11 +2026,7 @@ 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)
+        // a number token holds '.' regardless of the locale (#4084)
-        if (decimal_point_char != '.' && decimal_point_position != std::string::npos)
-        {
-            token_buffer[decimal_point_position] = '.';
-        }
         return token_buffer;
     }
 
@@ -2283,9 +2322,7 @@ scan_number_done:
     number_unsigned_t value_unsigned = 0;
     number_float_t value_float = 0;
 
-    /// the decimal point
+    /// the position of the decimal point in token_buffer
-    const char_int_type decimal_point_char = '.';
-    /// the position of the decimal point in the input
     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

@@ -118,14 +118,12 @@ 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]  first  pointer to the first character of the number
-@param[in]  last           pointer past the last character
+@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[out] out            the parsed value on success
 @return true if the value was parsed exactly; false to fall back to strtod
 */
-template<typename DecimalPointType>
+inline bool parse_float_fast(const char* first, const char* last, double& out) noexcept
-bool parse_float_fast(const char* first, const char* last, DecimalPointType decimal_point, 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 +134,6 @@ 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 +172,7 @@ 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 +257,8 @@ 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>
+template<typename FloatType>
-bool parse_float_fast(const char* /*first*/, const char* /*last*/, DecimalPointType /*decimal_point*/, FloatType& /*out*/) noexcept
+bool parse_float_fast(const char* /*first*/, const char* /*last*/, FloatType& /*out*/) noexcept
 {
     return false;
 }
@@ -273,9 +270,7 @@ 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
+consumes the entire token ([first, last)). An under-/overflow (result_out_of_range) also declines, so
-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
 the caller's strtod fallback supplies the well-defined ±inf/0 result the parser
 expects (side-stepping the P4168 divergence between implementations).
 

include/nlohmann/detail/macro_scope.hpp

@@ -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/output/serializer.hpp

@@ -48,8 +48,7 @@ enum class error_handler_t
 {
     strict,  ///< throw a type_error exception in case of invalid UTF-8
     replace, ///< replace invalid UTF-8 sequences with U+FFFD
-    ignore,  ///< ignore invalid UTF-8 sequences
+    ignore   ///< ignore invalid UTF-8 sequences
-    keep     ///< keep invalid UTF-8 sequences; their bytes are copied unchanged
 };
 
 template<typename BasicJsonType>
@@ -1020,47 +1019,6 @@ class serializer
                             break;
                         }
 
-                        case error_handler_t::keep:
-                        {
-                            // drop whatever the incomplete sequence left in
-                            // the buffer (only copied if !EnsureAscii) and copy
-                            // the ill-formed bytes from the input instead
-                            bytes = bytes_after_last_accept;
-
-                            if (undumped_chars > 0)
-                            {
-                                // the pending bytes of the incomplete sequence
-                                // are ill-formed; the current byte may be OK for
-                                // itself, so we would like to read it again
-                                for (std::size_t j = i - undumped_chars; j < i; ++j)
-                                {
-                                    string_buffer[bytes++] = s[j];
-                                }
-                                --i;
-                            }
-                            else
-                            {
-                                // the current byte cannot start any sequence
-                                string_buffer[bytes++] = s[i];
-                            }
-
-                            // write buffer and reset index; there must be 13 bytes
-                            // left, as this is the maximal number of bytes to be
-                            // written ("\uxxxx\uxxxx\0") for one code point
-                            if (string_buffer.size() - bytes < 13)
-                            {
-                                put_buffer(string_buffer, bytes);
-                                bytes = 0;
-                            }
-
-                            bytes_after_last_accept = bytes;
-                            undumped_chars = 0;
-
-                            // continue processing the string
-                            state = UTF8_ACCEPT;
-                            break;
-                        }
-
                         default:            // LCOV_EXCL_LINE
                             JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
                     }
@@ -1106,15 +1064,6 @@ class serializer
                     break;
                 }
 
-                case error_handler_t::keep:
-                {
-                    // write all accepted bytes
-                    put_buffer(string_buffer, bytes_after_last_accept);
-                    // copy the bytes of the incomplete sequence unchanged
-                    put_string(s, s.size() - undumped_chars, s.size());
-                    break;
-                }
-
                 case error_handler_t::replace:
                 {
                     // write all accepted bytes

include/nlohmann/json.hpp

@@ -6423,55 +6423,6 @@ 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 +6557,6 @@ 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 +6564,12 @@ 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
+    #include <nlohmann/json_literals.hpp>
+#endif
+
 #endif  // INCLUDE_NLOHMANN_JSON_HPP_

include/nlohmann/json_literals.hpp

@@ -0,0 +1,83 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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
+
+#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.
+
+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/
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    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)
+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/
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    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
+
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
+    #if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+        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
+
+#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_

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.hpp

@@ -3327,10 +3327,6 @@ void templated_json_throw(ExceptionType exception)
     #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif
 
-#ifndef JSON_USE_GLOBAL_UDLS
-    #define JSON_USE_GLOBAL_UDLS 1
-#endif
-
 #if JSON_HAS_THREE_WAY_COMPARISON
     #include <compare> // partial_ordering
 #endif
@@ -8605,14 +8601,12 @@ 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]  first  pointer to the first character of the number
-@param[in]  last           pointer past the last character
+@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[out] out            the parsed value on success
 @return true if the value was parsed exactly; false to fall back to strtod
 */
-template<typename DecimalPointType>
+inline bool parse_float_fast(const char* first, const char* last, double& out) noexcept
-bool parse_float_fast(const char* first, const char* last, DecimalPointType decimal_point, 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
@@ -8623,7 +8617,6 @@ 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
@@ -8662,7 +8655,7 @@ 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))
             {
@@ -8747,8 +8740,8 @@ 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>
+template<typename FloatType>
-bool parse_float_fast(const char* /*first*/, const char* /*last*/, DecimalPointType /*decimal_point*/, FloatType& /*out*/) noexcept
+bool parse_float_fast(const char* /*first*/, const char* /*last*/, FloatType& /*out*/) noexcept
 {
     return false;
 }
@@ -8760,9 +8753,7 @@ 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
+consumes the entire token ([first, last)). An under-/overflow (result_out_of_range) also declines, so
-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
 the caller's strtod fallback supplies the well-defined ±inf/0 result the parser
 expects (side-stepping the P4168 divergence between implementations).
 
@@ -9303,7 +9294,6 @@ 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_)
     {}
 
@@ -9319,8 +9309,7 @@ class lexer : public lexer_base<BasicJsonType>
     // locales
     /////////////////////
 
-    /// return the locale-dependent decimal point
+    /// return the decimal point of the current locale
-    JSON_HEDLEY_PURE
     static char get_decimal_point() noexcept
     {
         const auto* loc = localeconv();
@@ -10189,9 +10178,10 @@ 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
+    @note The scanner is independent of the current locale: token_buffer
-          locale's decimal point is used instead of `.` to work with the
+          always holds `.`. Only the std::strtod fallback of convert_number()
-          locale-dependent converters.
+          depends on the locale, and it looks up the decimal point right
+          before converting (see 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.
     {
@@ -10280,7 +10270,7 @@ scan_number_zero:
         {
             case '.':
             {
-                add(decimal_point_char);
+                add(current);
                 decimal_point_position = token_buffer.size() - 1;
                 goto scan_number_decimal1;
             }
@@ -10317,7 +10307,7 @@ scan_number_any1:
 
             case '.':
             {
-                add(decimal_point_char);
+                add(current);
                 decimal_point_position = token_buffer.size() - 1;
                 goto scan_number_decimal1;
             }
@@ -10559,9 +10549,9 @@ scan_number_done:
 
         // 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
+        // answer - so this loop is skipped for all but a few tokens. The
-        // token_buffer holds the locale's decimal point, so the fraction is
+        // fraction is located through decimal_point_position rather than by
-        // located through decimal_point_position rather than by searching '.'.
+        // searching '.'.
         if (lead_zero != 0)
         {
             JSON_ASSERT(has_dot != 0); // an integer "0" cannot reach the limit
@@ -10579,8 +10569,8 @@ scan_number_done:
     @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
+    scan_number() state machine or by the contiguous fast path) and holds '.'
-    locale decimal point in place of '.'. Integers are parsed first and fall
+    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.
 
@@ -10660,7 +10650,7 @@ 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.
+        // locale-aware strtof/strtod/strtold.
         if (parse_float_from_chars(num_begin, num_end, value_float))
         {
             return token_type::value_float;
@@ -10669,26 +10659,75 @@ scan_number_done:
         // 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))
+                && parse_float_fast(num_begin, num_end, value_float))
         {
             return token_type::value_float;
         }
 
-        char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+        convert_float_locale_aware();
-        strtof(value_float, token_buffer.data(), &endptr);
-
-        // we checked the number format before
-        JSON_ASSERT(endptr == token_buffer.data() + token_buffer.size());
-
         return token_type::value_float;
     }
 
+    /*!
+    @brief convert the float in token_buffer 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.
+    */
+    void convert_float_locale_aware()
+    {
+        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_buffer[decimal_point_position] = static_cast<typename string_t::value_type>(decimal_point);
+            }
+
+            char* endptr = nullptr; // NOLINT(misc-const-correctness,cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+            strtof(value_float, token_buffer.data(), &endptr);
+
+            if (substitute)
+            {
+                // get_string() hands the token to the SAX interface with '.'
+                token_buffer[decimal_point_position] = '.';
+            }
+
+            if (JSON_HEDLEY_LIKELY(endptr == token_buffer.data() + token_buffer.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;
+        }
+    }
+
     /*!
     @brief contiguous fast path for scanning a number
 
     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
@@ -10804,16 +10843,11 @@ scan_number_done:
         }
 #endif
 
-        // materialize the token exactly as scan_number() would, substituting the
+        // materialize the token exactly as scan_number() would. reset() already
-        // locale decimal point so convert_number()'s strtof fallback stays valid.
+        // cleared token_buffer, so append() fills it (assign() is avoided
-        // reset() already cleared token_buffer, so append() fills it (assign() is
+        // because custom string_t types need not provide it)
-        // 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)
+        decimal_point_position = dot_index;
-        {
-            token_buffer[dot_index] = static_cast<typename string_t::value_type>(decimal_point_char);
-            decimal_point_position = dot_index;
-        }
 
         ia.bulk_skip(len - 1);
         position.chars_read_total += (len - 1);
@@ -11080,11 +11114,7 @@ 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)
+        // a number token holds '.' regardless of the locale (#4084)
-        if (decimal_point_char != '.' && decimal_point_position != std::string::npos)
-        {
-            token_buffer[decimal_point_position] = '.';
-        }
         return token_buffer;
     }
 
@@ -11380,9 +11410,7 @@ scan_number_done:
     number_unsigned_t value_unsigned = 0;
     number_float_t value_float = 0;
 
-    /// the decimal point
+    /// the position of the decimal point in token_buffer
-    const char_int_type decimal_point_char = '.';
-    /// the position of the decimal point in the input
     std::size_t decimal_point_position = std::string::npos;
 
     /// whether the caller (e.g. accept()/json_sax_acceptor) only needs the
@@ -14059,6 +14087,80 @@ 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
 
@@ -14303,7 +14405,7 @@ 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;
                     }
@@ -14804,6 +14906,98 @@ 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
 
@@ -14966,7 +15160,7 @@ 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;
                     }
@@ -23931,8 +24125,7 @@ enum class error_handler_t
 {
     strict,  ///< throw a type_error exception in case of invalid UTF-8
     replace, ///< replace invalid UTF-8 sequences with U+FFFD
-    ignore,  ///< ignore invalid UTF-8 sequences
+    ignore   ///< ignore invalid UTF-8 sequences
-    keep     ///< keep invalid UTF-8 sequences; their bytes are copied unchanged
 };
 
 template<typename BasicJsonType>
@@ -24903,47 +25096,6 @@ class serializer
                             break;
                         }
 
-                        case error_handler_t::keep:
-                        {
-                            // drop whatever the incomplete sequence left in
-                            // the buffer (only copied if !EnsureAscii) and copy
-                            // the ill-formed bytes from the input instead
-                            bytes = bytes_after_last_accept;
-
-                            if (undumped_chars > 0)
-                            {
-                                // the pending bytes of the incomplete sequence
-                                // are ill-formed; the current byte may be OK for
-                                // itself, so we would like to read it again
-                                for (std::size_t j = i - undumped_chars; j < i; ++j)
-                                {
-                                    string_buffer[bytes++] = s[j];
-                                }
-                                --i;
-                            }
-                            else
-                            {
-                                // the current byte cannot start any sequence
-                                string_buffer[bytes++] = s[i];
-                            }
-
-                            // write buffer and reset index; there must be 13 bytes
-                            // left, as this is the maximal number of bytes to be
-                            // written ("\uxxxx\uxxxx\0") for one code point
-                            if (string_buffer.size() - bytes < 13)
-                            {
-                                put_buffer(string_buffer, bytes);
-                                bytes = 0;
-                            }
-
-                            bytes_after_last_accept = bytes;
-                            undumped_chars = 0;
-
-                            // continue processing the string
-                            state = UTF8_ACCEPT;
-                            break;
-                        }
-
                         default:            // LCOV_EXCL_LINE
                             JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
                     }
@@ -24989,15 +25141,6 @@ class serializer
                     break;
                 }
 
-                case error_handler_t::keep:
-                {
-                    // write all accepted bytes
-                    put_buffer(string_buffer, bytes_after_last_accept);
-                    // copy the bytes of the incomplete sequence unchanged
-                    put_string(s, s.size() - undumped_chars, s.size());
-                    break;
-                }
-
                 case error_handler_t::replace:
                 {
                     // write all accepted bytes
@@ -32357,55 +32500,6 @@ 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
 
 ///////////////////////
@@ -32540,17 +32634,6 @@ 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>
 //     __ _____ _____ _____
 //  __|  |   __|     |   | |  JSON for Modern C++
@@ -32579,7 +32662,6 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 #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
@@ -32772,4 +32854,97 @@ 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
+// #include <nlohmann/json_literals.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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
+
+// #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.
+
+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/
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    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)
+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/
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    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
+
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
+    #if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+        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
+
+#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
+
+#endif
+
 #endif  // INCLUDE_NLOHMANN_JSON_HPP_

single_include/nlohmann/json_literals.hpp

@@ -0,0 +1,83 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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
+
+#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.
+
+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/
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    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)
+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/
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    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
+
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
+    #if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+        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
+
+#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/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

@@ -666,7 +666,7 @@ 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;
 

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-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

tests/src/unit-no_automatic_udls.cpp

@@ -0,0 +1,97 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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).
+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()));
+
+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>")
+{
+    SECTION("global namespace")
+    {
+        CHECK("[1,2]"_json == json({1, 2}));
+        CHECK("/a/0"_json_pointer == json::json_pointer("/a/0"));
+    }
+
+    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-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)")

tests/src/unit-regression2.cpp

@@ -766,15 +766,6 @@ TEST_CASE("regression tests 2")
         CHECK(j == k);
     }
 
-    SECTION("issue #4552 - UTF-8 invalid characters are not always ignored when dumping with error_handler_t::ignore")
-    {
-        json node;
-        node["test"] = "test\334\005";
-        CHECK(node.dump(-1, ' ', false, json::error_handler_t::ignore) == "{\"test\":\"test\\u0005\"}");
-        CHECK(node.dump(-1, ' ', false, json::error_handler_t::keep) == "{\"test\":\"test\334\\u0005\"}");
-        CHECK(node.dump(-1, ' ', true, json::error_handler_t::keep) == "{\"test\":\"test\334\\u0005\"}");
-    }
-
 }
 
 TEST_CASE("regression test - parser callback must not lose a duplicate key's prior value")

tests/src/unit-serialization.cpp

@@ -92,8 +92,6 @@ TEST_CASE("serialization")
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"äü\"");
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"ä\xEF\xBF\xBDü\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"\\u00e4\\ufffd\\u00fc\"");
-            CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"ä\xA9ü\"");
-            CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"\\u00e4\xA9\\u00fc\"");
         }
 
         SECTION("invalid character (regression guard for shared UTF-8 decoder, see #5529)")
@@ -116,8 +114,6 @@ TEST_CASE("serialization")
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123\"");
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd\"");
-            CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"123\xC2\"");
-            CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"123\xC2\"");
         }
 
         SECTION("unexpected character")
@@ -130,39 +126,6 @@ TEST_CASE("serialization")
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123456\"");
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\x34\x35\x36\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd456\"");
-            CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"123\xF1\xB0\x34\x35\x36\"");
-            CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"123\xF1\xB0\x34\x35\x36\"");
-        }
-
-        SECTION("keep: valid characters are still escaped")
-        {
-            // an invalid byte followed by characters that must be escaped
-            const json j = "\xC2\"\\\n\xFF\x05";
-            CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == "\"\xC2\\\"\\\\\\n\xFF\\u0005\"");
-            CHECK(j.dump(-1, ' ', true, json::error_handler_t::keep) == "\"\xC2\\\"\\\\\\n\xFF\\u0005\"");
-        }
-
-        SECTION("keep: truncated multibyte sequences")
-        {
-            CHECK(json("\xF0\x9F\x98").dump(-1, ' ', false, json::error_handler_t::keep) == "\"\xF0\x9F\x98\"");
-            CHECK(json("\xF0\x9F\x98").dump(-1, ' ', true, json::error_handler_t::keep) == "\"\xF0\x9F\x98\"");
-            CHECK(json("\xF0\x9F\x98" "a").dump(-1, ' ', false, json::error_handler_t::keep) == "\"\xF0\x9F\x98" "a\"");
-            CHECK(json("\xF0\x9F\x98" "a").dump(-1, ' ', true, json::error_handler_t::keep) == "\"\xF0\x9F\x98" "a\"");
-        }
-
-        SECTION("keep: long string with many invalid bytes")
-        {
-            // exceeds the internal string buffer several times
-            std::string input;
-            std::string expected = "\"";
-            for (int i = 0; i < 2000; ++i)
-            {
-                input += "\xFF\xE2\x82\n\xC3\xA4";
-                expected += "\xFF\xE2\x82\\n\xC3\xA4";
-            }
-            expected += "\"";
-            const json j = input;
-            CHECK(j.dump(-1, ' ', false, json::error_handler_t::keep) == expected);
         }
 
         SECTION("U+FFFD Substitution of Maximal Subparts")

tests/src/unit-unicode2.cpp

@@ -14,7 +14,6 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
-#include <algorithm>
 #include <fstream>
 #include <sstream>
 #include <iostream>
@@ -76,11 +75,8 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     static std::string s_replaced2;
     static std::string s_replaced_ascii;
     static std::string s_replaced2_ascii;
-    static std::string s_kept;
-    static std::string s_kept2;
-    static std::string s_kept_ascii;
 
-    // dumping with ignore/replace/keep must not throw in any case
+    // dumping with ignore/replace must not throw in any case
     s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored2 = j2.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored_ascii = j.dump(-1, ' ', true, json::error_handler_t::ignore);
@@ -89,9 +85,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
     s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
     s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
-    s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept2 = j2.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept_ascii = j.dump(-1, ' ', true, json::error_handler_t::keep);
 
     if (success_expected)
     {
@@ -101,7 +94,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
         // all dumps should agree on the string
         CHECK(s_strict == s_ignored);
         CHECK(s_strict == s_replaced);
-        CHECK(s_strict == s_kept);
     }
     else
     {
@@ -113,20 +105,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
 
         // check that replace string contains a replacement character
         CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
-
-        // ignore drops the invalid bytes, keep copies them
-        CHECK(s_ignored != s_kept);
-        CHECK(s_ignored_ascii != s_kept_ascii);
-
-        // unless a byte needs escaping, keep copies the input unchanged
-        const bool needs_escaping = std::any_of(json_string.begin(), json_string.end(), [](char c)
-        {
-            return static_cast<unsigned char>(c) < 0x20 || c == '"' || c == '\\';
-        });
-        if (!needs_escaping)
-        {
-            CHECK(s_kept == "\"" + json_string + "\"");
-        }
     }
 
     // check that prefix and suffix are preserved
@@ -138,8 +116,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     CHECK(s_replaced2.substr(s_replaced2.size() - 4, 3) == "xyz");
     CHECK(s_replaced2_ascii.substr(1, 3) == "abc");
     CHECK(s_replaced2_ascii.substr(s_replaced2_ascii.size() - 4, 3) == "xyz");
-    CHECK(s_kept2.substr(1, 3) == "abc");
-    CHECK(s_kept2.substr(s_kept2.size() - 4, 3) == "xyz");
 }
 
 void check_utf8string(bool success_expected, int byte1, int byte2, int byte3, int byte4);

tests/src/unit-unicode3.cpp

@@ -14,7 +14,6 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
-#include <algorithm>
 #include <fstream>
 #include <sstream>
 #include <iostream>
@@ -76,11 +75,8 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     static std::string s_replaced2;
     static std::string s_replaced_ascii;
     static std::string s_replaced2_ascii;
-    static std::string s_kept;
-    static std::string s_kept2;
-    static std::string s_kept_ascii;
 
-    // dumping with ignore/replace/keep must not throw in any case
+    // dumping with ignore/replace must not throw in any case
     s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored2 = j2.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored_ascii = j.dump(-1, ' ', true, json::error_handler_t::ignore);
@@ -89,9 +85,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
     s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
     s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
-    s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept2 = j2.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept_ascii = j.dump(-1, ' ', true, json::error_handler_t::keep);
 
     if (success_expected)
     {
@@ -101,7 +94,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
         // all dumps should agree on the string
         CHECK(s_strict == s_ignored);
         CHECK(s_strict == s_replaced);
-        CHECK(s_strict == s_kept);
     }
     else
     {
@@ -113,20 +105,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
 
         // check that replace string contains a replacement character
         CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
-
-        // ignore drops the invalid bytes, keep copies them
-        CHECK(s_ignored != s_kept);
-        CHECK(s_ignored_ascii != s_kept_ascii);
-
-        // unless a byte needs escaping, keep copies the input unchanged
-        const bool needs_escaping = std::any_of(json_string.begin(), json_string.end(), [](char c)
-        {
-            return static_cast<unsigned char>(c) < 0x20 || c == '"' || c == '\\';
-        });
-        if (!needs_escaping)
-        {
-            CHECK(s_kept == "\"" + json_string + "\"");
-        }
     }
 
     // check that prefix and suffix are preserved
@@ -138,8 +116,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     CHECK(s_replaced2.substr(s_replaced2.size() - 4, 3) == "xyz");
     CHECK(s_replaced2_ascii.substr(1, 3) == "abc");
     CHECK(s_replaced2_ascii.substr(s_replaced2_ascii.size() - 4, 3) == "xyz");
-    CHECK(s_kept2.substr(1, 3) == "abc");
-    CHECK(s_kept2.substr(s_kept2.size() - 4, 3) == "xyz");
 }
 
 void check_utf8string(bool success_expected, int byte1, int byte2, int byte3, int byte4);

tests/src/unit-unicode4.cpp

@@ -14,7 +14,6 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
-#include <algorithm>
 #include <fstream>
 #include <sstream>
 #include <iostream>
@@ -76,11 +75,8 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     static std::string s_replaced2;
     static std::string s_replaced_ascii;
     static std::string s_replaced2_ascii;
-    static std::string s_kept;
-    static std::string s_kept2;
-    static std::string s_kept_ascii;
 
-    // dumping with ignore/replace/keep must not throw in any case
+    // dumping with ignore/replace must not throw in any case
     s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored2 = j2.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored_ascii = j.dump(-1, ' ', true, json::error_handler_t::ignore);
@@ -89,9 +85,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
     s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
     s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
-    s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept2 = j2.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept_ascii = j.dump(-1, ' ', true, json::error_handler_t::keep);
 
     if (success_expected)
     {
@@ -101,7 +94,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
         // all dumps should agree on the string
         CHECK(s_strict == s_ignored);
         CHECK(s_strict == s_replaced);
-        CHECK(s_strict == s_kept);
     }
     else
     {
@@ -113,20 +105,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
 
         // check that replace string contains a replacement character
         CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
-
-        // ignore drops the invalid bytes, keep copies them
-        CHECK(s_ignored != s_kept);
-        CHECK(s_ignored_ascii != s_kept_ascii);
-
-        // unless a byte needs escaping, keep copies the input unchanged
-        const bool needs_escaping = std::any_of(json_string.begin(), json_string.end(), [](char c)
-        {
-            return static_cast<unsigned char>(c) < 0x20 || c == '"' || c == '\\';
-        });
-        if (!needs_escaping)
-        {
-            CHECK(s_kept == "\"" + json_string + "\"");
-        }
     }
 
     // check that prefix and suffix are preserved
@@ -138,8 +116,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     CHECK(s_replaced2.substr(s_replaced2.size() - 4, 3) == "xyz");
     CHECK(s_replaced2_ascii.substr(1, 3) == "abc");
     CHECK(s_replaced2_ascii.substr(s_replaced2_ascii.size() - 4, 3) == "xyz");
-    CHECK(s_kept2.substr(1, 3) == "abc");
-    CHECK(s_kept2.substr(s_kept2.size() - 4, 3) == "xyz");
 }
 
 void check_utf8string(bool success_expected, int byte1, int byte2, int byte3, int byte4);

tests/src/unit-unicode5.cpp

@@ -14,7 +14,6 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
-#include <algorithm>
 #include <fstream>
 #include <sstream>
 #include <iostream>
@@ -76,11 +75,8 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     static std::string s_replaced2;
     static std::string s_replaced_ascii;
     static std::string s_replaced2_ascii;
-    static std::string s_kept;
-    static std::string s_kept2;
-    static std::string s_kept_ascii;
 
-    // dumping with ignore/replace/keep must not throw in any case
+    // dumping with ignore/replace must not throw in any case
     s_ignored = j.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored2 = j2.dump(-1, ' ', false, json::error_handler_t::ignore);
     s_ignored_ascii = j.dump(-1, ' ', true, json::error_handler_t::ignore);
@@ -89,9 +85,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     s_replaced2 = j2.dump(-1, ' ', false, json::error_handler_t::replace);
     s_replaced_ascii = j.dump(-1, ' ', true, json::error_handler_t::replace);
     s_replaced2_ascii = j2.dump(-1, ' ', true, json::error_handler_t::replace);
-    s_kept = j.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept2 = j2.dump(-1, ' ', false, json::error_handler_t::keep);
-    s_kept_ascii = j.dump(-1, ' ', true, json::error_handler_t::keep);
 
     if (success_expected)
     {
@@ -101,7 +94,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
         // all dumps should agree on the string
         CHECK(s_strict == s_ignored);
         CHECK(s_strict == s_replaced);
-        CHECK(s_strict == s_kept);
     }
     else
     {
@@ -113,20 +105,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
 
         // check that replace string contains a replacement character
         CHECK(s_replaced.find("\xEF\xBF\xBD") != std::string::npos);
-
-        // ignore drops the invalid bytes, keep copies them
-        CHECK(s_ignored != s_kept);
-        CHECK(s_ignored_ascii != s_kept_ascii);
-
-        // unless a byte needs escaping, keep copies the input unchanged
-        const bool needs_escaping = std::any_of(json_string.begin(), json_string.end(), [](char c)
-        {
-            return static_cast<unsigned char>(c) < 0x20 || c == '"' || c == '\\';
-        });
-        if (!needs_escaping)
-        {
-            CHECK(s_kept == "\"" + json_string + "\"");
-        }
     }
 
     // check that prefix and suffix are preserved
@@ -138,8 +116,6 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     CHECK(s_replaced2.substr(s_replaced2.size() - 4, 3) == "xyz");
     CHECK(s_replaced2_ascii.substr(1, 3) == "abc");
     CHECK(s_replaced2_ascii.substr(s_replaced2_ascii.size() - 4, 3) == "xyz");
-    CHECK(s_kept2.substr(1, 3) == "abc");
-    CHECK(s_kept2.substr(s_kept2.size() - 4, 3) == "xyz");
 }
 
 void check_utf8string(bool success_expected, int byte1, int byte2, int byte3, int byte4);