Merge deeply nested objects without recursing per nesting level (#5547)

* Merge deeply nested objects without recursing per nesting level

merge_patch() and update(j, true) merged a nested object by calling
themselves on it, once per nesting level. A value nested deeply enough -
50,000 levels of objects on an 8 MiB stack - exhausted the call stack
and terminated the process, although parse() accepts such values without
complaint.

Bound the descent the same way dump() does. The recursion now carries
the nesting level, and once merge_depth_limit() (128) levels have been
entered, update_members_iteratively() and merge_patch_iteratively()
finish the merge on an explicit stack. They still merge a nested object
completely before the next member, and in the same order, so the results,
including the parents JSON_DIAGNOSTICS reports paths from, are unchanged.
Values nested less deeply than the bound run the same code as before, so
the common case does not pay for the stack: merging only on it cost
10-14% in a first version.

The public signatures are unchanged. The recursive worker behind
merge_patch() has its own name rather than being a private overload, so
that &basic_json::merge_patch stays unambiguous.

Tests check every depth up to 300 against recursive reference
implementations of both operations, check the diagnostic paths past the
bound, and merge objects nested 100,000 levels deep.

Fixes #5545 for update(j, true), and #5393 for merge_patch().

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

* Use the shared recursion limit in update() and merge_patch()

merge_depth_limit() is gone in favor of detail::recursion_depth_limit().
The two identical function-local frame structs become one member struct,
merge_frame, with a constructor, so both loops emplace_back() their
frames. merge_patch_iteratively() copies the frame it works on out of the
stack and changes it only through stack.back().

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

* Build the update()/merge_patch() diagnostics test values instead of parsing them

Parsed values carry byte positions under JSON_DIAGNOSTIC_POSITIONS, which
the expected messages do not include.

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

---------

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

.github/CONTRIBUTING.md

@@ -158,6 +158,15 @@ make amalgamate
 Running `make amalgamate` will also apply automatic formatting to the source files using
 [`Artistic Style`](https://astyle.sourceforge.net/). This formatting may modify your source files in-place. Be certain to review and commit any changes to avoid unintended formatting diffs in commits.
 
+If you add, rename, or remove a header in `include/nlohmann`, also regenerate the header list in
+[`BUILD.bazel`](https://github.com/nlohmann/json/blob/develop/BUILD.bazel) (requires CMake) by executing:
+
+```shell
+make BUILD.bazel
+```
+
+The amalgamation check in CI fails if any of these generated files is out of date.
+
 ## Recommended documentation
 
 - The library’s [README file](https://github.com/nlohmann/json/blob/master/README.md) is an excellent starting point to

.github/labeler.yml

@@ -29,6 +29,27 @@ labels:
   files:
     - ".github/external_ci/.*"
 
+- label: "CI"
+  files:
+    - ".github/(dependabot|labeler)\\.yml"
+
+- label: "aspect: binary formats"
+  files:
+    - "include/nlohmann/detail/input/binary_reader\\.hpp"
+    - "include/nlohmann/detail/output/binary_writer\\.hpp"
+    - "tests/src/unit-(bson|cbor|msgpack|ubjson|bjdata|binary_formats)"
+    - "tests/src/fuzzer-parse_(bson|cbor|msgpack|ubjson|bjdata)"
+    - "docs/mkdocs/docs/features/binary_formats/"
+    - "docs/mkdocs/docs/(api/basic_json|examples)/(to|from)_(bson|cbor|msgpack|ubjson|bjdata)"
+
+- label: "aspect: binary formats"
+  title: "(?i)(bson|cbor|msgpack|messagepack|ubjson|bjdata|binary format)"
+
+- label: "python"
+  files:
+    - "\\.py$"
+    - "requirements[^/]*\\.txt$"
+
 - label: "S"
   size-below: 10
 - label: "M"

.github/workflows/check_amalgamation.yml

@@ -57,13 +57,16 @@ jobs:
           python3 -mvenv venv
           venv/bin/pip3 install -r $MAIN_DIR/tools/astyle/requirements.txt
 
-      - name: Regenerate amalgamation and formatting
+      - name: Regenerate amalgamation, formatting, and BUILD.bazel
         run: |
           cd $MAIN_DIR
 
           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 .
 
+          # the header list of the Bazel "json" target must match the files in include/
+          cmake -P cmake/scripts/gen_bazel_build_file.cmake
+
           ${{ github.workspace }}/venv/bin/astyle --project=tools/astyle/.astylerc --suffix=none --quiet \
             $INCLUDE_DIR/json.hpp $INCLUDE_DIR/json_fwd.hpp
 
@@ -87,7 +90,7 @@ jobs:
           mkdir -p ${{ github.workspace }}/patch
           git diff --patch --no-color > ${{ github.workspace }}/patch/amalgamation.patch
           if [ -s ${{ github.workspace }}/patch/amalgamation.patch ]; then
-            echo "The source code has not been amalgamated/formatted correctly. Diff:"
+            echo "The source code has not been amalgamated/formatted correctly or BUILD.bazel is out of date. Diff:"
             cat ${{ github.workspace }}/patch/amalgamation.patch
             echo "has_diff=true" >> "$GITHUB_OUTPUT"
           else

.github/workflows/codeql-analysis.yml

@@ -38,14 +38,14 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+      uses: github/codeql-action/init@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
       with:
         languages: c-cpp
 
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+      uses: github/codeql-action/autobuild@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+      uses: github/codeql-action/analyze@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0

.github/workflows/comment_check_amalgamation.yml

@@ -95,13 +95,13 @@ jobs:
               issue_number: issue_number,
               owner: context.repo.owner,
               repo: context.repo.repo,
-              body: '## 🔴 Amalgamation check failed! 🔴\nThe source code has not been amalgamated and/or formatted correctly.'
+              body: '## 🔴 Amalgamation check failed! 🔴\nThe source code has not been amalgamated and/or formatted correctly, or `BUILD.bazel` is out of date.'
                     + (hasPatch ? '\n\n📎 A ready-to-apply patch is attached to the [failed workflow run](' + runUrl + ') as the `amalgamation-patch` artifact.'
                                   + ' Download it, then apply it locally from the repository root with:'
                                   + '\n\n```shell\ngit apply amalgamation.patch\n```\n\n'
                                   + 'This does not require installing astyle yourself.'
                                 : '')
                     + (first ? '\n\n@' + author + ' Please read and follow the [Contribution Guidelines]'
-                               + '(https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#files-to-change).'
+                               + '(https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#amalgamate-the-source-code).'
                              : '')
               })

.github/workflows/flawfinder.yml

@@ -43,6 +43,6 @@ jobs:
           output: 'flawfinder_results.sarif'
 
       - name: Upload analysis results to GitHub Security tab
-        uses: github/codeql-action/upload-sarif@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
         with:
           sarif_file: ${{github.workspace}}/flawfinder_results.sarif

.github/workflows/scorecards.yml

@@ -76,6 +76,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
         with:
           sarif_file: results.sarif

.github/workflows/semgrep.yml

@@ -61,7 +61,7 @@ jobs:
 
       # Upload SARIF file generated in previous step
       - name: Upload SARIF file
-        uses: github/codeql-action/upload-sarif@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
         with:
           sarif_file: semgrep.sarif
         if: always()

.github/workflows/ubuntu.yml

@@ -100,7 +100,7 @@ jobs:
     container: ubuntu:focal
     strategy:
       matrix:
-        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_simdutf]
+        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_no_thread_local]
     steps:
       - name: Install build-essential
         run: apt-get update ; apt-get install -y build-essential unzip wget git libssl-dev

.github/workflows/windows.yml

@@ -158,6 +158,10 @@ jobs:
       # to fit: IMAGE_REL_AMD64_SECREL against `.debug_line'" because the
       # MinGW linker cannot relocate the debug sections this test produces.
       # The tests are only built and run here, so the debug info is not used.
+      # Do not add -O1 here to shrink the objects further: it does make them
+      # link, but the binaries clang 11.0.1 and clang 18.1.8 then produce crash
+      # before doctest prints its first line - 39 of 102 tests on clang 18.
+      # Keep the objects small by splitting the test files instead.
       - name: Run CMake
         run: cmake -S . -B build ^
              -DCMAKE_CXX_COMPILER="C:/Program Files/LLVM/bin/clang++.exe" ^

BUILD.bazel

@@ -30,8 +30,10 @@ cc_library(
         "include/nlohmann/detail/input/input_adapters.hpp",
         "include/nlohmann/detail/input/json_sax.hpp",
         "include/nlohmann/detail/input/lexer.hpp",
+        "include/nlohmann/detail/input/number_parse.hpp",
         "include/nlohmann/detail/input/parser.hpp",
         "include/nlohmann/detail/input/position_t.hpp",
+        "include/nlohmann/detail/input/string_scan.hpp",
         "include/nlohmann/detail/iterators/internal_iterator.hpp",
         "include/nlohmann/detail/iterators/iter_impl.hpp",
         "include/nlohmann/detail/iterators/iteration_proxy.hpp",
@@ -49,12 +51,14 @@ cc_library(
         "include/nlohmann/detail/meta/detected.hpp",
         "include/nlohmann/detail/meta/identity_tag.hpp",
         "include/nlohmann/detail/meta/is_sax.hpp",
+        "include/nlohmann/detail/meta/logic.hpp",
         "include/nlohmann/detail/meta/std_fs.hpp",
         "include/nlohmann/detail/meta/type_traits.hpp",
         "include/nlohmann/detail/meta/void_t.hpp",
         "include/nlohmann/detail/output/binary_writer.hpp",
         "include/nlohmann/detail/output/output_adapters.hpp",
         "include/nlohmann/detail/output/serializer.hpp",
+        "include/nlohmann/detail/recursion_depth_limit.hpp",
         "include/nlohmann/detail/string_concat.hpp",
         "include/nlohmann/detail/string_escape.hpp",
         "include/nlohmann/detail/string_utils.hpp",

CMakeLists.txt

@@ -59,6 +59,7 @@ option(JSON_LegacyDiscardedValueComparison "Enable legacy discarded value compar
 option(JSON_Install                        "Install CMake targets during install step." ${MAIN_PROJECT})
 option(JSON_MultipleHeaders                "Use non-amalgamated version of the library." ON)
 option(JSON_SystemInclude                  "Include as system headers (skip for clang-tidy)." OFF)
+option(JSON_StrictNulHandling              "Build with strict NUL-byte handling enabled." OFF)
 
 if (JSON_CI)
     include(ci)
@@ -108,6 +109,10 @@ if (JSON_Diagnostics)
     message(STATUS "Diagnostics enabled (JSON_DIAGNOSTICS=1)")
 endif()
 
+if (JSON_StrictNulHandling)
+    message(STATUS "Strict NUL-byte handling enabled (JSON_STRICT_NUL_HANDLING=1)")
+endif()
+
 if (JSON_Diagnostic_Positions)
     message(STATUS "Diagnostic positions enabled (JSON_DIAGNOSTIC_POSITIONS=1)")
 endif()
@@ -141,6 +146,7 @@ target_compile_definitions(
     $<$<BOOL:${JSON_Diagnostics}>:JSON_DIAGNOSTICS=1>
     $<$<BOOL:${JSON_Diagnostic_Positions}>:JSON_DIAGNOSTIC_POSITIONS=1>
     $<$<BOOL:${JSON_LegacyDiscardedValueComparison}>:JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1>
+    $<$<BOOL:${JSON_StrictNulHandling}>:JSON_STRICT_NUL_HANDLING=1>
 )
 
 target_include_directories(

FILES.md

@@ -250,12 +250,16 @@ Further documentation:
 
 ### `BUILD.bazel`
 
-The file can be updated by calling
+The build definition for [Bazel](https://bazel.build). The file is generated by
+`cmake/scripts/gen_bazel_build_file.cmake`, which derives the header list from the files in `include`; change the
+script rather than editing the file by hand. The file can be updated by calling
 
 ```shell
 make BUILD.bazel
 ```
 
+The "Check amalgamation" workflow fails if the file is out of date.
+
 ### `meson.build`
 
 The build definition for the [Meson](https://mesonbuild.com) build system.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef
+.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel
 
 ##########################################################################
 # configuration
@@ -30,8 +30,9 @@ 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 "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"
+	@echo "check-amalgamation - check whether sources have been amalgamated and BUILD.bazel is up to date"
 	@echo "clean - remove built files"
 	@echo "doctest - compile example files and check their output"
 	@echo "fuzz_testing - prepare fuzz testing of the JSON parser"
@@ -172,8 +173,13 @@ check-amalgamation:
 	@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)
 	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
 	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
+	@mv BUILD.bazel BUILD.bazel~
+	@$(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)
+	@mv BUILD.bazel~ BUILD.bazel
 
-BUILD.bazel: $(SRCS)
+# generate the Bazel BUILD file; phony, because a removed header would not trigger a rebuild
+BUILD.bazel:
 	cmake -P cmake/scripts/gen_bazel_build_file.cmake
 
 ##########################################################################

README.md

@@ -1421,7 +1421,7 @@ I deeply appreciate the help of the following people.
 6. [Joshua C. Randall](https://github.com/jrandall) fixed a bug in the floating-point serialization.
 7. [Aaron Burghardt](https://github.com/aburgh) implemented code to parse streams incrementally. Furthermore, he greatly improved the parser class by allowing the definition of a filter function to discard undesired elements while parsing.
 8. [Daniel Kopeček](https://github.com/dkopecek) fixed a bug in the compilation with GCC 5.0.
-9. [Florian Weber](https://github.com/Florianjw) fixed a bug in and improved the performance of the comparison operators.
+9. [Fiona Johanna Weber](https://github.com/Fiona-J-W) fixed a bug in and improved the performance of the comparison operators.
 10. [Eric Cornelius](https://github.com/EricMCornelius) pointed out a bug in the handling with NaN and infinity values. He also improved the performance of the string escaping.
 11. [易思龙](https://github.com/likebeta) implemented a conversion from anonymous enums.
 12. [kepkin](https://github.com/kepkin) patiently pushed forward the support for Microsoft Visual Studio.
@@ -1523,14 +1523,14 @@ I deeply appreciate the help of the following people.
 108. [Kevin Tonon](https://github.com/ktonon) overworked the C++11 compiler checks in CMake.
 109. [Axel Huebl](https://github.com/ax3l) simplified a CMake check and added support for the [Spack package manager](https://spack.io).
 110. [Carlos O'Ryan](https://github.com/coryan) fixed a typo.
-111. [James Upjohn](https://github.com/jammehcow) fixed a version number in the compilers section.
+111. [James Upjohn](https://github.com/jupjohn) fixed a version number in the compilers section.
 112. [Chuck Atkins](https://github.com/chuckatkins) adjusted the CMake files to the CMake packaging guidelines and provided documentation for the CMake integration.
 113. [Jan Schöppach](https://github.com/dns13) fixed a typo.
 114. [martin-mfg](https://github.com/martin-mfg) fixed a typo.
 115. [Matthias Möller](https://github.com/TinyTinni) removed the dependency from `std::stringstream`.
 116. [agrianius](https://github.com/agrianius) added code to use alternative string implementations.
 117. [Daniel599](https://github.com/Daniel599) allowed to use more algorithms with the `items()` function.
-118. [Julius Rakow](https://github.com/jrakow) fixed the Meson include directory and fixed the links to [cppreference.com](https://cppreference.com).
+118. [Julius Rakow](https://github.com/juliusrakow) fixed the Meson include directory and fixed the links to [cppreference.com](https://cppreference.com).
 119. [Sonu Lohani](https://github.com/sonulohani) fixed the compilation with MSVC 2015 in debug mode.
 120. [grembo](https://github.com/grembo) fixed the test suite and re-enabled several test cases.
 121. [Hyeon Kim](https://github.com/simnalamburt) introduced the macro `JSON_INTERNAL_CATCH` to control the exception handling inside the library.
@@ -1581,7 +1581,7 @@ I deeply appreciate the help of the following people.
 166. [Mark Beckwith](https://github.com/wythe) fixed a typo.
 167. [yann-morin-1998](https://github.com/yann-morin-1998) helped to reduce the CMake requirement to version 3.1.
 168. [Konstantin Podsvirov](https://github.com/podsvirov) maintains a package for the MSYS2 software distro.
-169. [remyabel](https://github.com/remyabel) added GNUInstallDirs to the CMake files.
+169. [remyabel](https://github.com/remyabel2) added GNUInstallDirs to the CMake files.
 170. [Taylor Howard](https://github.com/taylorhoward92) fixed a unit test.
 171. [Gabe Ron](https://github.com/Macr0Nerd) implemented the `to_string` method.
 172. [Watal M. Iwasaki](https://github.com/heavywatal) fixed a Clang warning.
@@ -1608,7 +1608,7 @@ I deeply appreciate the help of the following people.
 193. [Hubert Chathi](https://github.com/uhoreg) made CMake's version config file architecture-independent.
 194. [OmnipotentEntity](https://github.com/OmnipotentEntity) implemented the binary values for CBOR, MessagePack, BSON, and UBJSON.
 195. [ArtemSarmini](https://github.com/ArtemSarmini) fixed a compilation issue with GCC 10 and fixed a leak.
-196. [Evgenii Sopov](https://github.com/sea-kg) integrated the library to the wsjcpp package manager.
+196. [Evgenii Sopov](https://github.com/sea5kg) integrated the library to the wsjcpp package manager.
 197. [Sergey Linev](https://github.com/linev) fixed a compiler warning.
 198. [Miguel Magalhães](https://github.com/magamig) fixed the year in the copyright.
 199. [Gareth Sylvester-Bradley](https://github.com/garethsb-sony) fixed a compilation issue with MSVC.
@@ -1702,7 +1702,7 @@ I deeply appreciate the help of the following people.
 287. [NN](https://github.com/NN---) added the Visual Studio output directory to `.gitignore`.
 288. [Romain Reignier](https://github.com/romainreignier) improved the performance of the vector output adapter.
 289. [Mike](https://github.com/Mike-Leo-Smith) fixed the `std::iterator_traits`.
-290. [Richard Hozák](https://github.com/zxey) added macro `JSON_NO_ENUM` to disable default enum conversions.
+290. [Richard Hozák](https://github.com/richardhozak) added macro `JSON_NO_ENUM` to disable default enum conversions.
 291. [vakokako](https://github.com/vakokako) fixed tests when compiling with C++20.
 292. [Alexander “weej” Jones](https://github.com/alexweej) fixed an example in the README.
 293. [Eli Schwartz](https://github.com/eli-schwartz) added more files to the `include.zip` archive.
@@ -1727,7 +1727,7 @@ I deeply appreciate the help of the following people.
 312. [Gareth Sylvester-Bradley](https://github.com/garethsb) added `operator/=` and `operator/` to construct JSON pointers.
 313. [Michael Macnair](https://github.com/mykter) added support for afl-fuzz testing.
 314. [Berkus Decker](https://github.com/berkus) fixed a typo in the README.
-315. [Illia Polishchuk](https://github.com/effolkronium) improved the CMake testing.
+315. [Illia Polishchuk](https://github.com/ilqvya) improved the CMake testing.
 316. [Ikko Ashimine](https://github.com/eltociear) fixed a typo.
 317. [Raphael Grimm](https://github.com/barcode) added the possibility to define a custom base class.
 318. [tocic](https://github.com/tocic) fixed typos in the documentation.
@@ -1797,6 +1797,66 @@ I deeply appreciate the help of the following people.
 382. [bitFiedler](https://github.com/bitFiedler) made GDB pretty printer work with Python 3.8.
 383. [Gianfranco Costamagna](https://github.com/LocutusOfBorg) fixed a compiler warning.
 384. [risa2000](https://github.com/risa2000) made `std::filesystem::path` conversion to/from UTF-8 encoded string explicit.
+385. [AM](https://github.com/maqnouch) fixed typos in the README.
+386. [dmenendez-gruposantander](https://github.com/dmenendez-gruposantander) fixed typos in the comments of the examples.
+387. [Mihai Stan](https://github.com/mstan-xx) fixed comparisons against the literal `0`.
+388. [Matt Gumbel](https://github.com/intelmatt) fixed some `-Weffc++` warnings.
+389. [vimpunk](https://github.com/vimpunk) moved a lambda out of an unevaluated context to support older compilers.
+390. [Chris Harris](https://github.com/cjh1) fixed the compilation with GCC 4.8.
+391. [Palmer Dabbelt](https://github.com/palmer-dabbelt) generated and installed a pkg-config file.
+392. [Gus Pozuelo](https://github.com/ap-viavi) made `ordered_map` compatible with GCC 5.5, Clang 3.6, and Xcode 9.
+393. [AK](https://github.com/Lioncky) fixed an MSVC build error caused by the `min`/`max` macros from `windows.h`.
+394. [Sergiu Deitsch](https://github.com/sergiud) provided a fallback for missing `char8_t` support.
+395. [Xiaochuan Ye](https://github.com/XueSongTap) fixed `from_msgpack` for `std::byte` input by specializing `std::char_traits`.
+396. [Ville Vesilehto](https://github.com/thevilledev) fixed an overflow in the BJData size calculation and rejected overflowing negative integers in CBOR.
+397. [NmPassTHFan](https://github.com/nmpassthf) replaced the deprecated `std::is_trivial` for C++26.
+398. [Chris Ever](https://github.com/chirsz-ever) added the `ignore_trailing_commas` parser option.
+399. [Kuan-Fu Wu](https://github.com/kfwu1999) fixed the example code for `json_pointer` initialization.
+400. [David Kilzer](https://github.com/ddkilzer) added a missing header to the input adapters.
+401. [Miko](https://github.com/mikomikotaishi) added proper C++20 module support, simplified the module API, and fixed missing exports.
+402. [hitgirl](https://github.com/hitgil) fixed the CMake configuration when cross-compiling.
+403. [Devon Thomas](https://github.com/ThomaDevOSU) mentioned the Artistic Style formatting in the contribution guidelines.
+404. [Erik Hu](https://github.com/Erikhu1) made Coveralls upload errors non-fatal in the CI.
+405. [co63oc](https://github.com/co63oc) fixed typos.
+406. [DmitriBogdanov](https://github.com/DmitriBogdanov) fixed broken package manager links in the documentation.
+407. [Bander](https://github.com/banderzhm) improved the MSVC compatibility of the C++ modules.
+408. [Andy Choi](https://github.com/ccpong) removed an unnecessary `template` keyword before `get` in the README and the documentation.
+409. [SamareshSingh](https://github.com/ssam18) fixed single-element brace initialization to copy/move instead of wrapping in an array, fixed the `WITH_DEFAULT` macros for `ordered_map`, and handled moved events in `serve_header.py`.
+410. [Aditya](https://github.com/Lumowhisp) improved the documentation of the documentation generation.
+411. [cheese1](https://github.com/cheese1) clarified the README.
+412. [KhloodElhossiny](https://github.com/khloodelhossiny) enabled `std::string_view` keys in `operator[]`.
+413. [Charles Cabergs](https://github.com/cacharle) fixed a `-Wtautological-constant-out-of-range-compare` warning.
+414. [EALePain](https://github.com/EALePain) made the `std::tuple` conversion work with reference types such as `std::tie`.
+415. [koala_oishi](https://github.com/chibi-dogs) fixed grammatical wording in the README.
+416. [riccardoori11](https://github.com/riccardoori11) fixed a typo in the documentation.
+417. [Swastik Bose](https://github.com/VasuBhakt) fixed the parent pointers after `update()` with `JSON_DIAGNOSTICS` and fixed the Doxygen autolinking of requirements.
+418. [trdesilva](https://github.com/trdesilva) added `front`, `pop_front`, and `push_front` to `json_pointer`.
+419. [Akhilesh Arora](https://github.com/akhilesharora) fixed an incomplete-type error with `ordered_json`.
+420. [Hariom Phulre](https://github.com/hariomphulre) fixed the C++20 modules compilation with GCC.
+421. [Kirill Lokotkov](https://github.com/RUSLoker) fixed printing `long double` values.
+422. [George Sedov](https://github.com/radistmorse) added the `NLOHMANN_DEFINE_TYPE_*_WITH_NAMES` macros.
+423. [Caillin Nugent](https://github.com/nugentcaillin) added the `NLOHMANN_JSON_SERIALIZE_ENUM_STRICT` macro.
+424. [Cosmin D.](https://github.com/drcosmin) fixed `std::filesystem::path` conversions and added an MSVC workaround for `std::unique_ptr`.
+425. [Paul Dreik](https://github.com/pauldreik) fixed a test relying on implementation-specific behavior.
+426. [Daniel Falk](https://github.com/daniel-falk) added missing copyright notices to the SBOM.
+427. [Federico Sfriso](https://github.com/federicosfriso05-dotcom) added support for constructing JSON values from C++20 range views.
+428. [Luke Banicevic](https://github.com/banaboi) fixed corrupt BSON output for lengths exceeding `INT32_MAX`, cleaned up the BSON writer, and improved the documentation.
+429. [Patrick Armstrong](https://github.com/Patrick10199) updated the CBOR references and the half-precision float assertions.
+430. [Yash Bavadiya](https://github.com/xevrion) added checks to all BSON reads.
+431. [hum4nBeing](https://github.com/hum4nBeing) fixed the overflow handling of high-precision numbers in UBJSON.
+432. [tomatotomata](https://github.com/tomatotomata) added checks for reading CBOR tagged subtypes.
+433. [YingqiDuan](https://github.com/YingqiDuan) documented the BSON interoperability.
+434. [KBS](https://github.com/youdie006) documented the standards compliance and the strictness of `parse()` and `operator>>`.
+435. [Petr Bělohlávek](https://github.com/petrbel) added Clang 21 and 22 to the CI.
+436. [Dmitry Rantovov](https://github.com/darkdi) fixed the placement of a CBOR documentation block.
+437. [ljcjclljc](https://github.com/ljcjclljc) fixed the comparison of large unsigned integers with signed integers.
+438. [Sahil Kamate](https://github.com/sahilkamate03) fixed the handling of CBOR tags 0-5 and 21-23.
+439. [Krishnanand G](https://github.com/Krishnanand-G) made the UBJSON writer reject `use_type` without `use_size`.
+440. [whn](https://github.com/Whning0513) documented the lenient BSON input handling and corrected the complexity of `to_bson`.
+441. [elix3r](https://github.com/22elix3r) fixed `update()` with `merge_objects` when merging a primitive into an object.
+442. [Avionic Harshit](https://github.com/avionicharshit-byte) made `diff()` linear when an array shrinks.
+443. [Qatadaha Bin Matloob](https://github.com/qatcod) fixed comparisons between integers and floats and fixed unparsable BJData output.
+444. [Wu Shuwen](https://github.com/dajiaohuang) removed an unused include.
 
 Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.
 

cmake/ci.cmake

@@ -231,18 +231,20 @@ add_custom_target(ci_test_simdutf
 )
 
 ###############################################################################
-# Enable brace-init copy semantics.
+# Enable strict NUL-byte handling.
 ###############################################################################
 
-add_custom_target(ci_test_brace_init_copy_semantics
+add_custom_target(ci_test_strict_nul_handling
     COMMAND ${CMAKE_COMMAND}
     -DCMAKE_BUILD_TYPE=Debug -GNinja
-    -DJSON_BuildTests=ON -DJSON_FastTests=ON
-    -DCMAKE_CXX_FLAGS=-DJSON_BRACE_INIT_COPY_SEMANTICS=1
-    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_brace_init_copy_semantics
-    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_brace_init_copy_semantics
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_brace_init_copy_semantics && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
-    COMMENT "Compile and test with brace-init copy semantics enabled"
+    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_StrictNulHandling=ON
+    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_strict_nul_handling
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_strict_nul_handling
+    # unit-testsuites contains a fixture (a "1e308" test value) that relies on the
+    # legacy NUL-as-end-of-input behavior this macro disables; exclude it here, as
+    # it is expected to fail under strict NUL handling and is out of scope for it
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_strict_nul_handling && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure -E "test-testsuites"
+    COMMENT "Compile and test with strict NUL-byte handling enabled"
 )
 
 ###############################################################################
@@ -260,6 +262,59 @@ add_custom_target(ci_test_noglobaludls
     COMMENT "Compile and test with global UDLs disabled"
 )
 
+###############################################################################
+# Disable enum serialization.
+###############################################################################
+
+add_custom_target(ci_test_disableenumserialization
+    COMMAND ${CMAKE_COMMAND}
+    -DCMAKE_BUILD_TYPE=Debug -GNinja
+    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_DisableEnumSerialization=ON
+    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_disableenumserialization
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_disableenumserialization
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_disableenumserialization && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
+    COMMENT "Compile and test with enum serialization disabled"
+)
+
+###############################################################################
+# Skip the multiple-inclusion library version check.
+###############################################################################
+
+# tests/src/skip_library_version_check.cpp deliberately simulates a scenario
+# (mixing two differently-versioned inclusions of the library in one
+# translation unit) that unavoidably triggers the compiler's own "macro
+# redefined" warning, so -- unlike the ci_test_* targets above -- it is
+# compiled directly here, with a modest warning set, instead of being folded
+# into the library's own -Weverything/-Werror unit test matrix.
+add_custom_target(ci_test_skiplibraryversioncheck
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${PROJECT_BINARY_DIR}/skip_library_version_check
+    COMMAND ${CMAKE_CXX_COMPILER} -std=c++11 -Wall -Wextra
+        -I${PROJECT_SOURCE_DIR}/include
+        ${PROJECT_SOURCE_DIR}/tests/src/skip_library_version_check.cpp
+        -o ${PROJECT_BINARY_DIR}/skip_library_version_check/skip_library_version_check
+    COMMAND ${PROJECT_BINARY_DIR}/skip_library_version_check/skip_library_version_check
+    COMMENT "Compile and run a translation unit simulating a mismatched library version, with JSON_SKIP_LIBRARY_VERSION_CHECK defined"
+)
+
+###############################################################################
+# Disable thread-local storage.
+###############################################################################
+
+# Without thread-local storage, the copy constructor cannot bound its descent
+# and copies every object and array without the call stack. That path is
+# otherwise only reached by values nested deeper than the bound, so this target
+# is what runs the whole test suite through it.
+add_custom_target(ci_test_no_thread_local
+    COMMAND ${CMAKE_COMMAND}
+    -DCMAKE_BUILD_TYPE=Debug -GNinja
+    -DJSON_BuildTests=ON
+    -DCMAKE_CXX_FLAGS=-DJSON_NO_THREAD_LOCAL
+    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_no_thread_local
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_no_thread_local
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_no_thread_local && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
+    COMMENT "Compile and test without thread-local storage"
+)
+
 ###############################################################################
 # Coverage.
 ###############################################################################

cmake/scripts/gen_bazel_build_file.cmake

@@ -1,24 +1,58 @@
 # generate Bazel BUILD file
+#
+# usage: cmake -P cmake/scripts/gen_bazel_build_file.cmake (or: make BUILD.bazel)
+#
+# The header list of the "json" target is derived from the files in include/. Everything else is fixed text below,
+# so edit this script rather than BUILD.bazel.
 
-set(PROJECT_ROOT "${CMAKE_CURRENT_LIST_DIR}/../..")
+get_filename_component(PROJECT_ROOT "${CMAKE_CURRENT_LIST_DIR}/../.." ABSOLUTE)
 set(BUILD_FILE "${PROJECT_ROOT}/BUILD.bazel")
 
-file(GLOB_RECURSE HEADERS LIST_DIRECTORIES false RELATIVE "${PROJECT_ROOT}" "include/*.hpp")
+file(GLOB_RECURSE HEADERS LIST_DIRECTORIES false RELATIVE "${PROJECT_ROOT}" "${PROJECT_ROOT}/include/*.hpp")
+list(SORT HEADERS)
+
+set(CONTENT [=[
+load("@rules_cc//cc:cc_library.bzl", "cc_library")
+load("@rules_license//rules:license.bzl", "license")
+
+package(
+    default_applicable_licenses = [":license"],
+)
+
+exports_files([
+    "LICENSE.MIT",
+])
+
+license(
+    name = "license",
+    license_kinds = ["@rules_license//licenses/spdx:MIT"],
+    license_text = "LICENSE.MIT",
+)
 
-file(WRITE "${BUILD_FILE}" [=[
 cc_library(
     name = "json",
     hdrs = [
 ]=])
 
 foreach(header ${HEADERS})
-    file(APPEND "${BUILD_FILE}" "        \"${header}\",\n")
+    string(APPEND CONTENT "        \"${header}\",\n")
 endforeach()
 
-file(APPEND "${BUILD_FILE}" [=[
+string(APPEND CONTENT [=[
     ],
     includes = ["include"],
     visibility = ["//visibility:public"],
     alwayslink = True,
 )
+
+cc_library(
+    name = "singleheader-json",
+    hdrs = [
+        "single_include/nlohmann/json.hpp",
+    ],
+    includes = ["single_include"],
+    visibility = ["//visibility:public"],
+)
 ]=])
+
+file(WRITE "${BUILD_FILE}" "${CONTENT}")

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

@@ -90,6 +90,10 @@ Linear in the length of the input. The parser is a predictive LL(1) parser.
 
 A UTF-8 byte order mark is silently ignored.
 
+By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input, rather than as an ordinary (and,
+outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
+[`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
+
 ## Examples
 
 ??? example
@@ -111,6 +115,8 @@ A UTF-8 byte order mark is silently ignored.
 - [parse](parse.md) - deserialize from a compatible input
 - [sax_parse](sax_parse.md) - parse input using the SAX interface
 - [operator>>](../operator_gtgt.md) - deserialize from stream
+- [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
+  instead of treating it as end of input
 
 ## Version history
 
@@ -120,6 +126,8 @@ A UTF-8 byte order mark is silently ignored.
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
+- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
+  it as end of input; planned to become the default in version 4.0.0.
 
 !!! warning "Deprecation"
 

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

@@ -14,7 +14,11 @@ To store objects in C++, a type is defined by the template parameters explained
 ## Template parameters
 
 `ArrayType`
-:   container type to store arrays (e.g., `std::vector` or `std::list`)
+:   container type to store arrays. It must be a vector-like container: the library uses `operator[]`, `at()`, and
+    `resize()`, and requires random-access iterators. `#!cpp std::vector` and `#!cpp std::deque` qualify;
+    `#!cpp std::list` does not. See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#arraytype) for the full list of
+    requirements.
 
 `AllocatorType`
 :   the allocator to use for objects (e.g., `std::allocator`)
@@ -66,3 +70,4 @@ Arrays are stored as pointers in a `basic_json` type. That is, for any access to
 ## Version history
 
 - Added in version 1.0.0.
+- Made `capacity()` optional, so that array types such as `#!cpp std::deque` can be used, in version 3.13.0.

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

@@ -42,7 +42,9 @@ represent a byte array in modern C++.
     `value_type` must additionally be exactly one byte wide (e.g., `std::uint8_t`/`char`/`std::byte`): the binary
     serializers (CBOR, MessagePack, BSON, UBJSON) read and write the container's raw bytes via
     `reinterpret_cast`, which is only correct for byte-sized elements -- a container like
-    `#!cpp std::vector<std::intptr_t>` will not work as `BinaryType`.
+    `#!cpp std::vector<std::intptr_t>` will not work as `BinaryType`. The elements must be stored contiguously, and
+    the binary readers additionally require `resize()` and `operator[]`. See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#binarytype) for the full list.
 
 ## Notes
 
@@ -50,6 +52,11 @@ represent a byte array in modern C++.
 
 The default values for `BinaryType` is `#!cpp std::vector<std::uint8_t>`.
 
+#### Supported byte types
+
+`#!cpp std::vector<std::uint8_t>`, `#!cpp std::vector<char>`, and `#!cpp std::vector<std::byte>` are supported.
+Regardless of which of them is configured, [`dump`](dump.md) writes the bytes as the numbers 0..255.
+
 #### Custom BinaryType behavior
 
 When a custom `BinaryType` is configured (other than the default `#!cpp std::vector<std::uint8_t>`), you can assign
@@ -126,3 +133,6 @@ type `#!cpp binary_t*` must be dereferenced.
 ## Version history
 
 - Added in version 3.8.0. Changed the type of subtype to `std::uint64_t` in version 3.10.0.
+- Fixed [`dump`](dump.md), [`std::hash`](std_hash.md), and [`to_ubjson`](to_ubjson.md) for byte types that are not
+  integers (e.g., `#!cpp std::byte`) in version 3.13.0. `dump` now writes the bytes of a signed byte type (e.g.,
+  `#!cpp char`) as 0..255 rather than as negative numbers.

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

@@ -11,6 +11,14 @@ literals `#!json true` and `#!json false`.
 
 To store boolean values in C++, a type is defined by the template parameter  `BooleanType` which chooses the type to use.
 
+## Template parameters
+
+`BooleanType`
+:   the type to store booleans. As it is stored directly inside a `basic_json` value (in a union), it must be a
+    trivially default-constructible, trivially copyable, and trivially destructible type that is convertible to and
+    from `#!cpp bool`. See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#booleantype).
+
 ## Notes
 
 #### Default type

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

@@ -35,6 +35,10 @@ class basic_json;
 | `BinaryType`         | type for binary arrays                                                    | [`binary_t`](binary_t.md)                   |
 | `CustomBaseClass`    | extension point for user code                                             | [`json_base_class_t`](json_base_class_t.md) |
 
+The library imposes a number of requirements on these types that are not expressed as C++ concepts, such as the
+container operations `object_t` and `array_t` must provide, or the fact that `StringType` must be `char`-based. They
+are collected in [Template Parameter Requirements](../../features/types/template_parameters.md).
+
 ## Specializations
 
 - [**json**](../json.md) - default specialization

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

@@ -88,6 +88,8 @@ Strong exception safety: if an exception occurs, the original value stays intact
       do not belong to the same JSON value; example: `"iterators do not fit"`
     - Throws [`invalid_iterator.211`](../../home/exceptions.md#jsonexceptioninvalid_iterator211) if `first` or `last`
       are iterators into container for which insert is called; example: `"passed iterators may not belong to container"`
+    - Throws [`invalid_iterator.202`](../../home/exceptions.md#jsonexceptioninvalid_iterator202) if `first` or `last`
+      do not point to an array; example: `"iterators first and last must point to arrays"`
 4. The function can throw the following exceptions:
     - Throws [`type_error.309`](../../home/exceptions.md#jsonexceptiontype_error309) if called on JSON values other than
       arrays; example: `"cannot use insert() with string"`

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

@@ -21,8 +21,11 @@ The default value for `CustomBaseClass` is `void`. In this case, an
 
 #### Limitations
 
-The type `CustomBaseClass` has to be a default-constructible class.
+The type `CustomBaseClass` has to be a default-constructible, non-`final` class.
 `basic_json` only supports copy/move construction/assignment if `CustomBaseClass` does so as well.
+A `CustomBaseClass` with non-static data members forfeits `basic_json`'s
+[standard layout](https://en.cppreference.com/w/cpp/named_req/StandardLayoutType) guarantee. See
+[Template Parameter Requirements](../../features/types/template_parameters.md#custombaseclass).
 
 ## Examples
 

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

@@ -19,6 +19,12 @@ using json_serializer = JSONSerializer<T, SFINAE>;
 
 The default values for `json_serializer` is [`adl_serializer`](../adl_serializer/index.md).
 
+#### Requirements
+
+A custom serializer must provide `#!cpp static void to_json(basic_json&, T)` for every type it serializes, and either
+`#!cpp static void from_json(const basic_json&, T&)` or `#!cpp static T from_json(const basic_json&)` for every type it
+deserializes. See [Template Parameter Requirements](../../features/types/template_parameters.md#jsonserializer).
+
 ## Examples
 
 ??? example

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

@@ -20,6 +20,16 @@ used.
 To store floating-point numbers in C++, a type is defined by the template parameter `NumberFloatType` which chooses the
 type to use.
 
+## Template parameters
+
+`NumberFloatType`
+:   the type to store floating-point numbers. Parsing and serialization are implemented in terms of
+    `#!cpp std::strtof`/`#!cpp std::strtod`/`#!cpp std::strtold` and `#!cpp std::snprintf`, so the type must be
+    `#!cpp float`, `#!cpp double`, or `#!cpp long double`. The
+    [binary formats](../../features/binary_formats/index.md) additionally require `#!cpp float` or `#!cpp double`,
+    because they have no encoding for `#!cpp long double`. See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#numberfloattype).
+
 ## Notes
 
 #### Default type

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

@@ -20,6 +20,13 @@ used.
 To store integer numbers in C++, a type is defined by the template parameter `NumberIntegerType` which chooses the type
 to use.
 
+## Template parameters
+
+`NumberIntegerType`
+:   the type to store signed integers. It must be a **signed integral** type (`#!cpp std::is_integral`) with a
+    `#!cpp std::numeric_limits` specialization, and it is stored directly inside a `basic_json` value. See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#numberintegertype-and-numberunsignedtype).
+
 ## Notes
 
 #### Default type

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

@@ -20,6 +20,14 @@ used.
 To store unsigned integer numbers in C++, a type is defined by the template parameter `NumberUnsignedType` which chooses
 the type to use.
 
+## Template parameters
+
+`NumberUnsignedType`
+:   the type to store unsigned integers. It must be an **unsigned integral** type (`#!cpp std::is_integral`) with a
+    `#!cpp std::numeric_limits` specialization, and it must be able to represent the absolute value of every
+    [`number_integer_t`](number_integer_t.md) value. See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#numberintegertype-and-numberunsignedtype).
+
 ## Notes
 
 #### Default type

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

@@ -30,3 +30,5 @@ and [`default_object_comparator_t`](default_object_comparator_t.md) otherwise.
 - Added in version 3.0.0.
 - Changed to be conditionally defined as `#!cpp typename object_t::key_compare` or `default_object_comparator_t` in
   version 3.11.0.
+- Fixed the fallback to `default_object_comparator_t`, which previously failed to compile for object types without a
+  `key_compare` member type, in version 3.13.0.

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

@@ -18,7 +18,11 @@ To store objects in C++, a type is defined by the template parameters described
 ## Template parameters
 
 `ObjectType`
-:   the container to store objects (e.g., `std::map` or `std::unordered_map`)
+:   the container to store objects. Its template parameters must have the same order and meaning as those of
+    `std::map`; in particular, the third parameter is a comparator. `#!cpp std::unordered_map`, whose third parameter
+    is a hash function, therefore needs an adapter -- see
+    [Template Parameter Requirements](../../features/types/template_parameters.md#objecttype) for the full list of
+    requirements, an adapter example, and the containers that are known to work.
 
 `StringType`
 :   the type of the keys or names (e.g., `std::string`). The comparison function `std::less<StringType>` is used to
@@ -122,3 +126,4 @@ the object is silently converted as an array of key-value pairs, which is incorr
 ## Version history
 
 - Added in version 1.0.0.
+- Allowed object types whose `erase(iterator)` returns `#!cpp void` in version 3.13.0.

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

@@ -103,6 +103,10 @@ A UTF-8 byte order mark is silently ignored.
 Invalid Unicode escapes and unpaired surrogates in the input are reported as
 [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) with a detailed message.
 
+By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input, rather than as an ordinary (and,
+outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
+[`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
+
 ## Examples
 
 ??? example "Parsing from a character array"
@@ -236,6 +240,8 @@ Invalid Unicode escapes and unpaired surrogates in the input are reported as
 - [accept](accept.md) - check if the input is valid JSON
 - [sax_parse](sax_parse.md) - parse input using the SAX interface
 - [operator>>](../operator_gtgt.md) - deserialize from stream
+- [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
+  instead of treating it as end of input
 
 ## Version history
 
@@ -246,6 +252,8 @@ Invalid Unicode escapes and unpaired surrogates in the input are reported as
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
+- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
+  it as end of input; planned to become the default in version 4.0.0.
 
 !!! warning "Deprecation"
 

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

@@ -23,6 +23,11 @@ JSON class into byte-sized characters during deserialization.
     `StringType`. To work with wide-character data, convert it to/from UTF-8 at the boundary instead -- see the
     FAQ's [wide string handling](../../home/faq.md#wide-string-handling) section for a conversion recipe.
 
+    Beyond the character type, the library expects a substantial part of the `#!cpp std::string` interface (contiguous
+    null-terminated `data()`, `substr()`, `find()`, `append()`, ...). See
+    [Template Parameter Requirements](../../features/types/template_parameters.md#stringtype) for the full list and
+    for the string types that are known to work.
+
 ## Notes
 
 #### Default type
@@ -78,3 +83,5 @@ and an example.
 ## Version history
 
 - Added in version 1.0.0.
+- Removed the requirement that `string_t` be implicitly convertible from `#!cpp std::string`, which the BSON writer and
+  the UBJSON reader relied on, in version 3.13.0.

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

@@ -37,7 +37,14 @@ Linear in the size of the JSON value.
 ## Notes
 
 Empty objects and arrays are flattened by [`flatten()`](flatten.md) to `#!json null` values and cannot unflattened to
-their original type. Apart from this example, for a JSON value `j`, the following is always true:
+their original type.
+
+A flattened array and a flattened object whose keys are array indices are indistinguishable, because both are
+described by the same JSON pointers. A value is therefore restored as an array if and only if one of its keys is the
+reference token `0`, and as an object otherwise: `#!json {"2": 1}` is restored unchanged, whereas `#!json {"0": 1}` is
+restored as `#!json [1]`. This decision does not depend on the order in which the flattened object is iterated.
+
+Apart from these two cases, for a JSON value `j`, the following is always true:
 `#!cpp j == j.flatten().unflatten()`.
 
 ## Examples
@@ -63,3 +70,4 @@ their original type. Apart from this example, for a JSON value `j`, the followin
 ## Version history
 
 - Added in version 2.0.0.
+- Made the array/object decision independent of the object's iteration order in version 3.13.0.

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

@@ -14,6 +14,11 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_DIAGNOSTIC_POSITIONS**](json_diagnostic_positions.md) - access positions of elements
 - [**JSON_NOEXCEPTION**](json_noexception.md) - switch off exceptions
 
+## Parsing
+
+- [**JSON_STRICT_NUL_HANDLING**](json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input instead of
+  treating it as end of input
+
 ## Language support
 
 - [**JSON_HAS_CPP_11**<br>**JSON_HAS_CPP_14**<br>**JSON_HAS_CPP_17**<br>**JSON_HAS_CPP_20**](json_has_cpp_11.md) - set supported C++ standard
@@ -22,6 +27,7 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**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_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
 - [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
 - [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation

docs/mkdocs/docs/api/macros/json_brace_init_copy_semantics.md

@@ -38,6 +38,28 @@ The default value is `0` (disabled — existing behavior is preserved).
 
     This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no effect.
 
+!!! warning "Applies to every single-element list"
+
+    The macro does not only affect a single JSON value in braces. **Any** single-element braced list is treated as its
+    element, so it no longer creates a one-element array:
+
+    ```cpp
+    json j1 = {1};       // 1, not [1]
+    json j2 = {"text"};  // "text", not ["text"]
+    json j3 = {{1, 2}};  // [1,2], not [[1,2]]
+    ```
+
+    Code that relies on these producing arrays must use `json::array()` instead (see below). Lists with more than one
+    element, and a single `[string, value]` pair such as `{{"key", "value"}}`, which still creates an object, are not
+    affected. The library's own conversions are not affected either: for example, `std::tuple<int>{5}` still becomes
+    `[5]`.
+
+!!! note "ABI compatibility"
+
+    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_bics`), resulting in
+    distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
+    without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
+
 !!! tip "Workaround without the macro"
 
     To explicitly create a single-element array without enabling this macro, use `json::array()`:

docs/mkdocs/docs/api/macros/json_no_thread_local.md

@@ -0,0 +1,47 @@
+# JSON_NO_THREAD_LOCAL
+
+```cpp
+#define JSON_NO_THREAD_LOCAL
+```
+
+When defined, the library does not use `#!cpp thread_local` storage. This is relevant for the few environments whose
+toolchain does not support it.
+
+The copy constructor copies the first levels of a value by copying the containers, which copy their elements, and
+completes whatever is nested deeper than that without the call stack, so that copying a value cannot exhaust the stack
+however deeply it is nested. It counts the levels it has descended into in a `#!cpp thread_local` variable, as a counter
+shared between threads would be raced.
+
+Without that counter, no descent can be bounded safely, so objects and arrays are copied without the call stack right
+away. Copying keeps working exactly as it does otherwise - the same values come out, and deeply nested values are copied
+just as safely - but copying is slower, because the containers no longer copy themselves. Copying the benchmark
+documents takes 9% (`canada.json`) to 34% (`twitter.json`) longer; values built mostly from objects are affected the
+most.
+
+## Default definition
+
+By default, `#!cpp JSON_NO_THREAD_LOCAL` is not defined.
+
+```cpp
+#undef JSON_NO_THREAD_LOCAL
+```
+
+The library defines it by itself for Clang targeting MinGW, which does not survive the `#!cpp thread_local` storage:
+copying a value segfaults there, with both old and current Clang versions, while GCC targeting MinGW is unaffected.
+
+## Examples
+
+??? example
+
+    The code below forces the library not to use `#!cpp thread_local` storage.
+
+    ```cpp
+    #define JSON_NO_THREAD_LOCAL 1
+    #include <nlohmann/json.hpp>
+
+    ...
+    ```
+
+## Version history
+
+- Added in version 3.12.1.

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

@@ -0,0 +1,126 @@
+# JSON_STRICT_NUL_HANDLING
+
+```cpp
+#define JSON_STRICT_NUL_HANDLING /* value */
+```
+
+When defined to `1`, a `'\0'` (NUL) byte in JSON text input is rejected with `parse_error.101`, like any other
+unexpected byte, instead of being silently treated as end of input.
+
+The macro only affects the JSON text parser ([`parse`](../basic_json/parse.md), [`accept`](../basic_json/accept.md),
+[`sax_parse`](../basic_json/sax_parse.md), and [`operator>>`](../operator_gtgt.md)). There are three cases where a NUL
+byte is still not rejected:
+
+- The binary formats ([`from_bjdata`](../basic_json/from_bjdata.md), [`from_bson`](../basic_json/from_bson.md),
+  [`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
+  [`from_ubjson`](../basic_json/from_ubjson.md)) are never affected: there, `0x00` is ordinary data.
+- A bare `const char*` pointer has no length of its own, so its length is still determined with `strlen()`. The first
+  NUL byte therefore still marks the end of the input, and nothing after it is read.
+- One trailing `'\0'` at the end of a `char` array (e.g., a string literal) is trimmed; see the warning below.
+
+## Default definition
+
+The default value is `0` (disabled — existing behavior is preserved).
+
+```cpp
+#define JSON_STRICT_NUL_HANDLING 0
+```
+
+## Notes
+
+!!! note "Background"
+
+    By default, a `'\0'` byte anywhere in the input is treated the same as the real end of the input, rather than as
+    an ordinary (and, outside of a string, invalid) byte. Everything from that byte onward is silently ignored,
+    without a parse error - including further, otherwise well-formed JSON:
+
+    ```cpp
+    json::parse(std::string("123") + '\0');          // == 123, no error
+    json::parse(std::string("123") + '\0' + "true"); // == 123, the "true" is silently ignored too
+    ```
+
+    This falls out of the same convention used when no explicit input length is given at all: parsing from a
+    `const char*` already stops at the first NUL byte via `strlen()`, since a bare pointer has no length of its own.
+    The library applies that same NUL-terminated-C-string convention uniformly, rather than only when a length is
+    genuinely unavailable - so a `std::string`, iterator range, or container whose content happens to include a NUL
+    byte is affected the same way a raw `const char*` would be (see the
+    [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for a fuller explanation).
+
+    This was not fixed unconditionally, because doing so is backwards-incompatible for any caller who happens to
+    depend on the current behavior - even unknowingly, for instance because their input already contains trailing
+    padding they never noticed was being discarded (see [#5530](https://github.com/nlohmann/json/issues/5530)).
+    This macro instead offers an opt-in path to the corrected behavior ahead of version 4.0.0, where it is planned to
+    become the default.
+
+!!! warning "Opt-in only"
+
+    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
+    effect.
+
+    Enabling it also changes how a `char` array (including a string literal, e.g. `json::parse("123")`) is read: such
+    an array normally carries a trailing `'\0'` contributed by the compiler, not by the source text. With this macro
+    enabled, that one trailing byte is trimmed if present so that parsing a string literal keeps working; every other
+    byte in the array - including any `'\0'` that is not the very last element - is read as real data and rejected
+    like any other unexpected byte. Arrays of any other element type (`unsigned char`, `std::uint8_t`, ...), as used
+    for CBOR or MessagePack, are never affected by this trimming; their full extent - including a genuine trailing
+    `0x00` - is always preserved, in both states of this macro.
+
+!!! tip "Workaround without the macro"
+
+    To reject a NUL byte without enabling this macro, trim your input yourself before calling `parse()`:
+
+    ```cpp
+    s.resize(s.find('\0')); // drop everything from the first NUL onward, if any
+    json::parse(s);
+    ```
+
+## Examples
+
+??? example "Default behavior (macro not defined)"
+
+    Without the macro, a NUL byte silently ends parsing at that point:
+
+    ```cpp
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        json j = json::parse(std::string("123") + '\0' + "true");
+        // j is 123 -- the '\0' and everything after it is silently ignored
+    }
+    ```
+
+??? example "Opt-in strict handling (macro defined to 1)"
+
+    With the macro, a NUL byte is rejected like any other unexpected byte:
+
+    ```cpp
+    #define JSON_STRICT_NUL_HANDLING 1
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        json j = json::parse(std::string("123") + '\0' + "true");
+        // throws parse_error.101 -- the NUL byte is now invalid input,
+        // exactly like any other unexpected trailing byte
+
+        json ok = json::parse("123");
+        // ok is 123 -- parsing from a string literal still works
+    }
+    ```
+
+## See also
+
+- [FAQ: NUL bytes in the input](../../home/faq.md#nul-bytes-in-the-input)
+- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
+- [**accept**](../basic_json/accept.md) - check if the input is valid JSON
+- [**operator>>**](../operator_gtgt.md) - deserialize from stream
+
+## Version history
+
+- Added in version 3.13.0.
+- Planned to become the default (with the macro removed) in version 4.0.0.

docs/mkdocs/docs/api/macros/json_throw_user.md

@@ -12,9 +12,11 @@
 Controls how exceptions are handled by the library.
 
 1. This macro overrides [`#!cpp catch`](https://en.cppreference.com/w/cpp/language/try_catch) calls inside the library.
-   The argument is the type of the exception to catch. As of version 3.8.0, the library only catches `std::out_of_range`
-   exceptions internally to rethrow them as [`json::out_of_range`](../../home/exceptions.md#out-of-range) exceptions.
-   The macro is always followed by a scope.
+   The argument is the type of the exception to catch. The library uses it in a single place: to swallow any exception
+   escaping the parent-pointer check that [`JSON_DIAGNOSTICS`](json_diagnostics.md) adds to the class invariant. The
+   places where the library catches its own [`json::out_of_range`](../../home/exceptions.md#out-of-range) exceptions
+   use `JSON_INTERNAL_CATCH` instead, which `JSON_CATCH_USER` also overrides unless `JSON_INTERNAL_CATCH_USER` is
+   defined. The macro is always followed by a scope.
 2. This macro overrides `#!cpp throw` calls inside the library. The argument is the exception to be thrown. Note that
    `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield
    undefined behavior.

docs/mkdocs/docs/api/macros/json_use_implicit_conversions.md

@@ -24,6 +24,14 @@ By default, implicit conversions are enabled.
     You can prepare existing code by already defining `JSON_USE_IMPLICIT_CONVERSIONS` to `0` and replace any implicit
     conversions with calls to [`get`](../basic_json/get.md).
 
+!!! tip "Automatic migration"
+
+    The community-maintained clang-tidy check `modernize-nlohmann-json-explicit-conversions` rewrites implicit
+    conversions into explicit calls to [`get`](../basic_json/get.md); for example, `#!cpp int i = j;` becomes
+    `#!cpp int i = j.get<int>();`. The check is not part of clang-tidy itself, and it does not catch every case (for
+    example, constructing a `std::optional` from a JSON value), so review the result. See
+    [discussion #4610](https://github.com/nlohmann/json/discussions/4610) for how to build and use it.
+
 !!! hint "CMake option"
 
     Implicit conversions can also be controlled with the CMake option

docs/mkdocs/docs/api/operator_gtgt.md

@@ -72,6 +72,13 @@ input >> j2;  // parses the next value
 Note that reading concatenated values does **not** work for [JSON Lines](../features/parsing/json_lines.md)
 (newline-delimited JSON) input -- see that page for why and for the recommended alternative.
 
+By default, a `'\0'` (NUL) byte encountered while reading a value is treated as end of input, rather than as an
+ordinary (and, outside of a string, invalid) byte; see the [FAQ entry](../home/faq.md#nul-bytes-in-the-input) for
+details and the [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) macro to opt into rejecting it
+instead. Because `operator>>` only parses a single value and does not require the rest of the stream to be consumed,
+a NUL byte *after* a complete value has no effect on `operator>>` either way; it only matters while a value is still
+being read.
+
 !!! warning "Deprecation"
 
     This function replaces function `#!cpp std::istream& operator<<(basic_json& j, std::istream& i)` which has
@@ -98,7 +105,11 @@ Note that reading concatenated values does **not** work for [JSON Lines](../feat
 
 - [accept](basic_json/accept.md) - check if the input is valid JSON
 - [parse](basic_json/parse.md) - deserialize from a compatible input
+- [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
+  instead of treating it as end of input
 
 ## Version history
 
 - Added in version 1.0.0.
+- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
+  it as end of input; planned to become the default in version 4.0.0.

docs/mkdocs/docs/examples/custom_array_type.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+#include <map>
+
+#include <nlohmann/json.hpp>
+
+#include "custom_array_type.hpp"
+
+using custom_json = nlohmann::basic_json<std::map, custom_array_type>;
+
+int main()
+{
+    custom_json j = custom_json::array();
+    j.push_back(1);
+    j.push_back(2);
+    j.push_back(3);
+
+    std::cout << j.dump() << std::endl;
+    std::cout << std::boolalpha << (custom_json::parse(j.dump()) == j) << std::endl;
+}

docs/mkdocs/docs/examples/custom_array_type.hpp

@@ -0,0 +1,152 @@
+#pragma once
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+// A minimal, self-contained ArrayType built around a private std::vector.
+// See https://json.nlohmann.me/features/types/template_parameters/#arraytype
+template<class T, class Allocator = std::allocator<T>>
+class custom_array_type
+{
+    using vector_t = std::vector<T, Allocator>;
+    vector_t data_;
+
+  public:
+    using value_type = typename vector_t::value_type;
+    using size_type = typename vector_t::size_type;
+    using iterator = typename vector_t::iterator;
+    using const_iterator = typename vector_t::const_iterator;
+
+    custom_array_type() = default;
+    custom_array_type(const custom_array_type&) = default;
+    custom_array_type(custom_array_type&&) = default;
+    custom_array_type& operator=(const custom_array_type&) = default;
+    custom_array_type& operator=(custom_array_type&&) = default;
+
+    template<class InputIt>
+    custom_array_type(InputIt first, InputIt last) : data_(first, last) {}
+
+    custom_array_type(size_type count, const T& value) : data_(count, value) {}
+
+    iterator begin()
+    {
+        return data_.begin();
+    }
+    iterator end()
+    {
+        return data_.end();
+    }
+    const_iterator begin() const
+    {
+        return data_.begin();
+    }
+    const_iterator end() const
+    {
+        return data_.end();
+    }
+    const_iterator cbegin() const
+    {
+        return data_.cbegin();
+    }
+    const_iterator cend() const
+    {
+        return data_.cend();
+    }
+
+    bool empty() const
+    {
+        return data_.empty();
+    }
+    size_type size() const
+    {
+        return data_.size();
+    }
+    size_type max_size() const
+    {
+        return data_.max_size();
+    }
+    void clear()
+    {
+        data_.clear();
+    }
+    void resize(size_type n)
+    {
+        data_.resize(n);
+    }
+
+    T& operator[](size_type pos)
+    {
+        return data_[pos];
+    }
+    const T& operator[](size_type pos) const
+    {
+        return data_[pos];
+    }
+
+    T& back()
+    {
+        return data_.back();
+    }
+    const T& back() const
+    {
+        return data_.back();
+    }
+
+    void push_back(const T& value)
+    {
+        data_.push_back(value);
+    }
+    void push_back(T&& value)
+    {
+        data_.push_back(std::move(value));
+    }
+
+    template<class... Args>
+    void emplace_back(Args&& ... args)
+    {
+        data_.emplace_back(std::forward<Args>(args)...);
+    }
+
+    void pop_back()
+    {
+        data_.pop_back();
+    }
+
+    iterator insert(const_iterator pos, const T& value)
+    {
+        return data_.insert(pos, value);
+    }
+    iterator insert(const_iterator pos, size_type count, const T& value)
+    {
+        return data_.insert(pos, count, value);
+    }
+    template<class InputIt>
+    iterator insert(const_iterator pos, InputIt first, InputIt last)
+    {
+        return data_.insert(pos, first, last);
+    }
+
+    iterator erase(const_iterator pos)
+    {
+        return data_.erase(pos);
+    }
+    iterator erase(const_iterator first, const_iterator last)
+    {
+        return data_.erase(first, last);
+    }
+
+    void swap(custom_array_type& other)
+    {
+        data_.swap(other.data_);
+    }
+
+    friend bool operator==(const custom_array_type& lhs, const custom_array_type& rhs)
+    {
+        return lhs.data_ == rhs.data_;
+    }
+    friend bool operator<(const custom_array_type& lhs, const custom_array_type& rhs)
+    {
+        return lhs.data_ < rhs.data_;
+    }
+};

docs/mkdocs/docs/examples/custom_array_type.output

@@ -0,0 +1,2 @@
+[1,2,3]
+true

docs/mkdocs/docs/examples/custom_binary_type.cpp

@@ -0,0 +1,21 @@
+#include <cstdint>
+#include <iostream>
+#include <map>
+#include <string>
+#include <vector>
+
+#include <nlohmann/json.hpp>
+
+#include "custom_binary_type.hpp"
+
+using custom_json = nlohmann::basic_json<std::map, std::vector, std::string, bool,
+      std::int64_t, std::uint64_t, double, std::allocator,
+      nlohmann::adl_serializer, custom_binary_type>;
+
+int main()
+{
+    const auto j = custom_json::binary({0x01, 0x02, 0x03});
+
+    std::cout << j.dump() << std::endl;
+    std::cout << std::boolalpha << (custom_json::from_cbor(custom_json::to_cbor(j)) == j) << std::endl;
+}

docs/mkdocs/docs/examples/custom_binary_type.hpp

@@ -0,0 +1,112 @@
+#pragma once
+
+#include <cstdint>
+#include <initializer_list>
+#include <vector>
+
+// A minimal, self-contained BinaryType built around a private std::vector.
+// See https://json.nlohmann.me/features/types/template_parameters/#binarytype
+class custom_binary_type
+{
+    using vector_t = std::vector<std::uint8_t>;
+    vector_t data_;
+
+  public:
+    using value_type = vector_t::value_type;
+    using size_type = vector_t::size_type;
+    using iterator = vector_t::iterator;
+    using const_iterator = vector_t::const_iterator;
+
+    custom_binary_type() = default;
+    custom_binary_type(const custom_binary_type&) = default;
+    custom_binary_type(custom_binary_type&&) = default;
+    custom_binary_type& operator=(const custom_binary_type&) = default;
+    custom_binary_type& operator=(custom_binary_type&&) = default;
+
+    template<class InputIt>
+    custom_binary_type(InputIt first, InputIt last) : data_(first, last) {}
+
+    // so basic_json::binary({0x01, 0x02}) can build one directly
+    custom_binary_type(std::initializer_list<std::uint8_t> init) : data_(init) {}
+
+    size_type size() const
+    {
+        return data_.size();
+    }
+    bool empty() const
+    {
+        return data_.empty();
+    }
+    void clear()
+    {
+        data_.clear();
+    }
+    void resize(size_type n)
+    {
+        data_.resize(n);
+    }
+
+    // read-only is enough: the writers only ever read from a binary value
+    const std::uint8_t* data() const
+    {
+        return data_.data();
+    }
+
+    std::uint8_t& operator[](size_type pos)
+    {
+        return data_[pos];
+    }
+    std::uint8_t operator[](size_type pos) const
+    {
+        return data_[pos];
+    }
+
+    std::uint8_t& back()
+    {
+        return data_.back();
+    }
+    std::uint8_t back() const
+    {
+        return data_.back();
+    }
+
+    iterator begin()
+    {
+        return data_.begin();
+    }
+    iterator end()
+    {
+        return data_.end();
+    }
+    const_iterator begin() const
+    {
+        return data_.begin();
+    }
+    const_iterator end() const
+    {
+        return data_.end();
+    }
+    const_iterator cbegin() const
+    {
+        return data_.cbegin();
+    }
+    const_iterator cend() const
+    {
+        return data_.cend();
+    }
+
+    template<class InputIt>
+    iterator insert(const_iterator pos, InputIt first, InputIt last)
+    {
+        return data_.insert(pos, first, last);
+    }
+
+    friend bool operator==(const custom_binary_type& lhs, const custom_binary_type& rhs)
+    {
+        return lhs.data_ == rhs.data_;
+    }
+    friend bool operator<(const custom_binary_type& lhs, const custom_binary_type& rhs)
+    {
+        return lhs.data_ < rhs.data_;
+    }
+};

docs/mkdocs/docs/examples/custom_binary_type.output

@@ -0,0 +1,2 @@
+{"bytes":[1,2,3],"subtype":null}
+true

docs/mkdocs/docs/examples/custom_object_type.cpp

@@ -0,0 +1,26 @@
+#include <iostream>
+#include <type_traits>
+#include <vector>
+
+#include <nlohmann/json.hpp>
+
+#include "custom_object_type.hpp"
+
+using custom_json = nlohmann::basic_json<custom_object_type, std::vector>;
+
+int main()
+{
+    custom_json j;
+    j["pi"] = 3.141;
+    j["happy"] = true;
+    j["list"] = {1, 2, 3};
+
+    std::cout << j.dump(2) << std::endl;
+    std::cout << std::boolalpha << (custom_json::parse(j.dump()) == j) << std::endl;
+
+    // custom_object_type has no key_compare member, so object_comparator_t
+    // falls back to its default
+    std::cout << std::boolalpha
+              << std::is_same<custom_json::object_comparator_t, custom_json::default_object_comparator_t>::value
+              << std::endl;
+}

docs/mkdocs/docs/examples/custom_object_type.hpp

@@ -0,0 +1,144 @@
+#pragma once
+
+#include <map>
+#include <utility>
+
+// A minimal, self-contained ObjectType built around a private std::map.
+// key_compare is deliberately not exposed: when an ObjectType has no
+// key_compare member, the library falls back to its own default comparator.
+// See https://json.nlohmann.me/features/types/template_parameters/#objecttype
+template<class Key, class T, class Compare, class Allocator>
+class custom_object_type
+{
+    using map_t = std::map<Key, T, Compare, Allocator>;
+    map_t data_;
+
+  public:
+    using key_type = typename map_t::key_type;
+    using mapped_type = typename map_t::mapped_type;
+    using value_type = typename map_t::value_type;
+    using size_type = typename map_t::size_type;
+    using iterator = typename map_t::iterator;
+    using const_iterator = typename map_t::const_iterator;
+
+    custom_object_type() = default;
+    custom_object_type(const custom_object_type&) = default;
+    custom_object_type(custom_object_type&&) = default;
+    custom_object_type& operator=(const custom_object_type&) = default;
+    custom_object_type& operator=(custom_object_type&&) = default;
+
+    template<class InputIt>
+    custom_object_type(InputIt first, InputIt last) : data_(first, last) {}
+
+    iterator begin()
+    {
+        return data_.begin();
+    }
+    iterator end()
+    {
+        return data_.end();
+    }
+    const_iterator begin() const
+    {
+        return data_.begin();
+    }
+    const_iterator end() const
+    {
+        return data_.end();
+    }
+    const_iterator cbegin() const
+    {
+        return data_.cbegin();
+    }
+    const_iterator cend() const
+    {
+        return data_.cend();
+    }
+
+    bool empty() const
+    {
+        return data_.empty();
+    }
+    size_type size() const
+    {
+        return data_.size();
+    }
+    size_type max_size() const
+    {
+        return data_.max_size();
+    }
+    void clear()
+    {
+        data_.clear();
+    }
+
+    iterator find(const key_type& key)
+    {
+        return data_.find(key);
+    }
+    const_iterator find(const key_type& key) const
+    {
+        return data_.find(key);
+    }
+    size_type count(const key_type& key) const
+    {
+        return data_.count(key);
+    }
+
+    std::pair<iterator, bool> emplace(const key_type& key, const mapped_type& value)
+    {
+        return data_.emplace(key, value);
+    }
+
+    std::pair<iterator, bool> insert(const value_type& value)
+    {
+        return data_.insert(value);
+    }
+
+    template<class InputIt>
+    void insert(InputIt first, InputIt last)
+    {
+        data_.insert(first, last);
+    }
+
+    mapped_type& operator[](const key_type& key)
+    {
+        return data_[key];
+    }
+
+    mapped_type& at(const key_type& key)
+    {
+        return data_.at(key);
+    }
+    const mapped_type& at(const key_type& key) const
+    {
+        return data_.at(key);
+    }
+
+    iterator erase(iterator pos)
+    {
+        return data_.erase(pos);
+    }
+    iterator erase(iterator first, iterator last)
+    {
+        return data_.erase(first, last);
+    }
+    size_type erase(const key_type& key)
+    {
+        return data_.erase(key);
+    }
+
+    void swap(custom_object_type& other)
+    {
+        data_.swap(other.data_);
+    }
+
+    friend bool operator==(const custom_object_type& lhs, const custom_object_type& rhs)
+    {
+        return lhs.data_ == rhs.data_;
+    }
+    friend bool operator<(const custom_object_type& lhs, const custom_object_type& rhs)
+    {
+        return lhs.data_ < rhs.data_;
+    }
+};

docs/mkdocs/docs/examples/custom_object_type.output

@@ -0,0 +1,11 @@
+{
+  "happy": true,
+  "list": [
+    1,
+    2,
+    3
+  ],
+  "pi": 3.141
+}
+true
+true

docs/mkdocs/docs/examples/custom_string_type.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <map>
+#include <vector>
+
+#include <nlohmann/json.hpp>
+
+#include "custom_string_type.hpp"
+
+using custom_json = nlohmann::basic_json<std::map, std::vector, custom_string_type>;
+
+int main()
+{
+    custom_json j;
+    j["pi"] = 3.141;
+    j["happy"] = true;
+    j["list"] = {1, 2, 3};
+
+    std::cout << j.dump(2) << std::endl;
+    std::cout << std::boolalpha << (custom_json::parse(j.dump()) == j) << std::endl;
+}

docs/mkdocs/docs/examples/custom_string_type.hpp

@@ -0,0 +1,134 @@
+#pragma once
+
+#include <ostream>
+#include <string>
+
+// A minimal, self-contained StringType built around a private std::string.
+// Wraps rather than inherits, so it exposes exactly what the library needs
+// and nothing more of std::string's interface.
+//
+// Covers the "Always required" members, the extras needed for the binary
+// formats, and the extras needed for JSON Pointer / flatten / unflatten /
+// diff. Extending it further (e.g. for std::hash<basic_json> or to_bson) is
+// a matter of adding the extra members listed in the "Required for other
+// functionality" table.
+//
+// See https://json.nlohmann.me/features/types/template_parameters/#stringtype
+class custom_string_type
+{
+    std::string data_;
+
+  public:
+    using value_type = char;
+    using size_type = std::string::size_type;
+    using iterator = std::string::iterator;
+    using const_iterator = std::string::const_iterator;
+
+    static constexpr size_type npos = std::string::npos;
+
+    custom_string_type() = default;
+    custom_string_type(const custom_string_type&) = default;
+    custom_string_type(custom_string_type&&) = default;
+    custom_string_type& operator=(const custom_string_type&) = default;
+    custom_string_type& operator=(custom_string_type&&) = default;
+
+    // not explicit: the library relies on being able to hand it a string literal
+    custom_string_type(const char* s) : data_(s) {}
+    custom_string_type(const char* s, size_type count) : data_(s, count) {}
+    custom_string_type(size_type count, char ch) : data_(count, ch) {}
+
+    size_type size() const
+    {
+        return data_.size();
+    }
+    bool empty() const
+    {
+        return data_.empty();
+    }
+    void clear()
+    {
+        data_.clear();
+    }
+    void resize(size_type n)
+    {
+        data_.resize(n);
+    }
+    void resize(size_type n, char c)
+    {
+        data_.resize(n, c);
+    }
+    void reserve(size_type n)
+    {
+        data_.reserve(n);
+    }
+
+    // must stay null-terminated -- the parser hands this to std::strtoull &
+    // friends; std::string::data() has guaranteed that since C++11
+    const char* data() const
+    {
+        return data_.data();
+    }
+
+    void push_back(char c)
+    {
+        data_.push_back(c);
+    }
+
+    char& operator[](size_type pos)
+    {
+        return data_[pos];
+    }
+    char operator[](size_type pos) const
+    {
+        return data_[pos];
+    }
+
+    custom_string_type& append(const char* s, size_type count)
+    {
+        data_.append(s, count);
+        return *this;
+    }
+    custom_string_type& append(const custom_string_type& other)
+    {
+        data_.append(other.data_);
+        return *this;
+    }
+
+    size_type find_first_of(char c, size_type pos = 0) const
+    {
+        return data_.find_first_of(c, pos);
+    }
+
+    iterator begin()
+    {
+        return data_.begin();
+    }
+    iterator end()
+    {
+        return data_.end();
+    }
+    const_iterator begin() const
+    {
+        return data_.begin();
+    }
+    const_iterator end() const
+    {
+        return data_.end();
+    }
+
+    friend bool operator==(const custom_string_type& lhs, const custom_string_type& rhs)
+    {
+        return lhs.data_ == rhs.data_;
+    }
+    friend bool operator<(const custom_string_type& lhs, const custom_string_type& rhs)
+    {
+        return lhs.data_ < rhs.data_;
+    }
+
+    // not required by the library itself, but dump() returns a custom_string_type
+    // and this makes `std::cout << j.dump()` work as expected
+    friend std::ostream& operator<<(std::ostream& os, const custom_string_type& s)
+    {
+        return os << s.data_;
+    }
+};

docs/mkdocs/docs/examples/custom_string_type.output

@@ -0,0 +1,10 @@
+{
+  "happy": true,
+  "list": [
+    1,
+    2,
+    3
+  ],
+  "pi": 3.141
+}
+true

docs/mkdocs/docs/features/binary_formats/bjdata.md

@@ -116,18 +116,22 @@ The library uses the following mapping from JSON values types to BJData types ac
     ```
 
     Likewise, when a JSON object in the above form is serialized using
-    [`to_bjdata`](../../api/basic_json/to_bjdata.md), it is automatically converted into a compact BJData ND-array. When
-    the 1-dimensional vector stored in `"_ArraySize_"` contains a single integer or two integers with one being 1, a
-    regular 1-D optimized array is generated instead.
+    [`to_bjdata`](../../api/basic_json/to_bjdata.md), it is automatically converted into a compact BJData ND-array.
 
-    An object is only converted if the annotation actually describes a packed array; otherwise it is serialized as a
-    regular JSON object. This requires all of the following:
+    When parsing, an ND-array whose dimension vector is empty, contains a single integer, contains two integers with the
+    first being 1, or contains a 0 is returned as a regular (possibly empty) array rather than an annotated object.
+
+    An object is only converted if the annotation describes a packed array that is parsed back into the same annotated
+    object; otherwise it is serialized as a regular JSON object, so the annotation is never lost in a round trip. This requires
+    all of the following:
 
     - `"_ArrayType_"` is one of `uint8`, `int8`, `uint16`, `int16`, `uint32`, `int32`, `uint64`, `int64`, `single`,
       `double`, `char`, or `byte`,
     - `"_ArraySize_"` is an array, since the dimensions are written as the ND-array header's length,
-    - every entry of `"_ArraySize_"` is a non-negative integer, and their product is representable as a `std::size_t`,
-    - `"_ArrayData_"` holds exactly that many elements, and
+    - `"_ArraySize_"` has at least two entries and is not a 1×N row vector (first entry 1), since other shapes are
+      parsed back as a regular array,
+    - every entry of `"_ArraySize_"` is a positive integer, and their product is representable as a `std::size_t`,
+    - `"_ArrayData_"` is an array holding exactly that many elements, and
     - every element of `"_ArrayData_"` is a number of the kind named by `"_ArrayType_"` (a floating-point number for
       `single` and `double`, an integer otherwise).
 

docs/mkdocs/docs/features/binary_formats/bson.md

@@ -109,15 +109,6 @@ The library maps BSON record types to JSON value types as follows:
     If BSON input must be validated for strict specification compliance, validate it separately before passing it to
     `from_bson()`.
 
-!!! warning "UTF-8 validation of string values"
-
-    The BSON specification requires `string` values (type `0x02`) to be valid UTF-8. This library validates the
-    bytes of every such string at decode time and rejects ill-formed UTF-8 with a
-    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with `allow_exceptions`
-    set to `false`, a discarded value), rather than only failing later when the resulting value is dumped. Element
-    (key) names and `binary` values (type `0x05`) are unaffected and are never validated, since they are read
-    byte-by-byte as a C string, or are not required to hold text, respectively.
-
 ??? example
 
     ```cpp

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

@@ -176,16 +176,6 @@ The library maps CBOR types to JSON value types as follows:
 
     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.
 
-!!! warning "UTF-8 validation of text strings"
-
-    [RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings
-    (major type 3) to be valid UTF-8. This library validates the bytes of every text string (object keys included) at
-    decode time and rejects ill-formed UTF-8 with a
-    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
-    `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is
-    dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold
-    text.
-
 !!! warning "Tagged items"
 
     Tagged items (0xC0..0xDB) will throw a parse error by default. They can be ignored by passing `cbor_tag_handler_t::ignore` to function `from_cbor`, in which case the tag is skipped and the enclosed data item is parsed on its own. They can be stored by passing `cbor_tag_handler_t::store` to function `from_cbor`. Note that no tag is ever interpreted: for instance, a text string tagged with tag 0 (date/time) stays a string.

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

@@ -136,14 +136,6 @@ 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 "UTF-8 validation of string values"
-
-    The MessagePack specification requires `str` values (`fixstr`, `str 8`, `str 16`, `str 32`) to be valid UTF-8.
-    This library validates the bytes of every such string (object keys included) at decode time and rejects
-    ill-formed UTF-8 with a [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or,
-    with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting
-    value is dumped. `bin`/`ext`/`fixext` values are unaffected and are never validated, since they are not required
-    to hold text.
 
 ??? example
 

docs/mkdocs/docs/features/macros.md

@@ -91,6 +91,13 @@ security reasons (e.g., Intel Software Guard Extensions (SGX)).
 
 See [full documentation of `JSON_NO_IO`](../api/macros/json_no_io.md).
 
+## `JSON_NO_THREAD_LOCAL`
+
+When defined, the library does not use `#!cpp thread_local` storage. Copying a value then always avoids the call stack
+rather than descending into a bounded number of levels first, which is slower but yields the same values.
+
+See [full documentation of `JSON_NO_THREAD_LOCAL`](../api/macros/json_no_thread_local.md).
+
 ## `JSON_SKIP_LIBRARY_VERSION_CHECK`
 
 When defined, the library will not create a compiler warning when a different version of the library was already
@@ -105,6 +112,19 @@ using the library with compilers that do not fully support C++11 and may only wo
 
 See [full documentation of `JSON_SKIP_UNSUPPORTED_COMPILER_CHECK`](../api/macros/json_skip_unsupported_compiler_check.md).
 
+## `JSON_STRICT_NUL_HANDLING`
+
+When defined to `1`, a `'\0'` (NUL) byte anywhere in the input is rejected with `parse_error.101`, like any other
+unexpected byte, instead of being silently treated as end of input (see the
+[FAQ entry](../home/faq.md#nul-bytes-in-the-input) for background). The default value is `0`, which preserves the
+existing behavior; this is planned to become the default in version 4.0.0.
+
+The strict handling can also be enabled with the CMake option
+[`JSON_StrictNulHandling`](../integration/cmake.md#json_strictnulhandling) (`OFF` by default) which sets
+`JSON_STRICT_NUL_HANDLING` accordingly.
+
+See [full documentation of `JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md).
+
 ## `JSON_THROW_USER(exception)`
 
 This macro overrides `#!cpp throw` calls inside the library. The argument is the exception to be thrown.

docs/mkdocs/docs/features/namespace.md

@@ -15,6 +15,9 @@ The complete default namespace name is derived as follows:
     - [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) defined non-zero appends `_diag`.
     - [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md)
       defined non-zero appends `_ldvcmp`.
+    - [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) defined non-zero appends `_dp`.
+    - [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) defined non-zero appends
+      `_bics`.
 - The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
   underscores. To omit the version component, see [Disabling the version component](#disabling-the-version-component)
   below.

docs/mkdocs/docs/features/object_order.md

@@ -51,7 +51,11 @@ If you do want to preserve the **insertion order**, you can use the type [`nlohm
     --8<-- "examples/ordered_json.output"
     ```
 
-Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).
+Alternatively, [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) also preserves the insertion order and, unlike [`ordered_map`](../api/ordered_map.md), keeps a lookup index, so it does not have the quadratic cost described below. It is used through a small adapter ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).
+
+If the order does not matter and you only want faster lookup, `boost::unordered_flat_map`, `absl::flat_hash_map`, `absl::node_hash_map`, and several other hash maps work through an adapter that restores the template argument order `basic_json` expects; see [Template Parameter Requirements](types/template_parameters.md#objecttype). Note these are *unordered*, not insertion-ordered.
+
+[`tsl::ordered_map`](https://github.com/Tessil/ordered-map) cannot be used: its iterators expose the mapped value as `const`, while `basic_json` needs to modify it in place.
 
 The [`ordered_map`](../api/ordered_map.md) behind `nlohmann::ordered_json` is deliberately minimal and has no lookup
 index, so every key access is a linear scan and building an object of `n` keys costs O(n²). This is unnoticeable at

docs/mkdocs/docs/features/types/index.md

@@ -79,7 +79,8 @@ template<
     class NumberFloatType = double,
     template<typename U> class AllocatorType = std::allocator,
     template<typename T, typename SFINAE = void> class JSONSerializer = adl_serializer,
-    class BinaryType = std::vector<std::uint8_t>
+    class BinaryType = std::vector<std::uint8_t>,
+    class CustomBaseClass = void
 >
 class basic_json;
 ```
@@ -106,6 +107,10 @@ using number_float_t = NumberFloatType;
 using binary_t = nlohmann::byte_container_with_subtype<BinaryType>;
 ```
 
+Not every type can be passed for these template arguments: the library uses the resulting types in ways that imply a
+number of requirements, for instance that `StringType` is `char`-based or that `ArrayType` is vector-like. These
+requirements are collected in [Template Parameter Requirements](template_parameters.md).
+
 
 ## Objects
 

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

@@ -0,0 +1,747 @@
+# Template Parameter Requirements
+
+Class [`basic_json`](../../api/basic_json/index.md) is configurable through eleven template parameters. The library
+never formally states what a type passed for one of these parameters has to provide -- the requirements are implied by
+the way the library uses the resulting [`object_t`](../../api/basic_json/object_t.md),
+[`array_t`](../../api/basic_json/array_t.md), [`string_t`](../../api/basic_json/string_t.md), etc. This page collects
+these requirements so they do not have to be discovered by trial and error. Each section lists the concrete types
+that are known to work for that parameter and the ones that do not, checked against Boost 1.83, Abseil 20250127.0,
+Folly, EASTL 3.21, `ankerl::unordered_dense`, `phmap`, `gtl`, `robin_hood`, `tsl::ordered_map`, and Qt 6.
+
+## How to read this page
+
+Requirements are split into two groups:
+
+- **Always required** -- needed to instantiate `basic_json` at all, or needed by functions that virtually every program
+  uses (construction, element access, [`dump`](../../api/basic_json/dump.md)).
+- **Required for ...** -- only needed when a particular part of the API is instantiated. Member function templates are
+  only instantiated when they are used, so a type may be perfectly usable even though it does not satisfy these
+  requirements, as long as the corresponding functions are never called.
+
+!!! warning "Requirements are not checked"
+
+    Three requirements are checked with a `#!cpp static_assert`: the array iterator category, the width of
+    [`BinaryType`](#binarytype)'s `value_type`, and [`NumberUnsignedType`](#numberintegertype-and-numberunsignedtype)
+    being at least as wide as [`NumberIntegerType`](#numberintegertype-and-numberunsignedtype). The rest are not
+    diagnosed with dedicated error messages, and violating most of them results in a compiler error somewhere inside
+    the library. Four violations are not caught at compile time at all:
+
+    - A [`StringType`](#stringtype) whose `data()` is not null-terminated compiles and silently misparses numbers,
+      because the lexer hands the buffer to `#!cpp std::strtoull`/`#!cpp std::strtoll`/`#!cpp std::strtod`.
+    - A stateful [`AllocatorType`](#allocatortype) compiles and silently ignores its state: allocation, deallocation,
+      and [`get_allocator()`](../../api/basic_json/get_allocator.md) each use a different default-constructed instance.
+    - The two [cross-specialization conversions](#cross-specialization-conversions) below. These abort on an assertion
+      in a normal build, and only fail silently under `#!cpp NDEBUG`.
+
+## Overview
+
+| Template parameter                                                | Default                           | Notable substitutes                                                   |
+|-------------------------------------------------------------------|-----------------------------------|-----------------------------------------------------------------------|
+| [`ObjectType`](#objecttype)                                       | `std::map`                        | [`nlohmann::ordered_map`](../../api/ordered_map.md), Abseil hash maps |
+| [`ArrayType`](#arraytype)                                         | `std::vector`                     | `#!cpp std::deque`                                                    |
+| [`StringType`](#stringtype)                                       | `std::string`                     | `std::string`-like types over `char`                                  |
+| [`BooleanType`](#booleantype)                                     | `bool`                            | none worth using                                                      |
+| [`NumberIntegerType`](#numberintegertype-and-numberunsignedtype)  | `std::int64_t`                    | any signed integer type                                               |
+| [`NumberUnsignedType`](#numberintegertype-and-numberunsignedtype) | `std::uint64_t`                   | any unsigned integer type at least as wide as `NumberIntegerType`     |
+| [`NumberFloatType`](#numberfloattype)                             | `double`                          | `float` (`long double`: no binary formats)                            |
+| [`AllocatorType`](#allocatortype)                                 | `std::allocator`                  | stateless allocators                                                  |
+| [`JSONSerializer`](#jsonserializer)                               | `adl_serializer`                  | serializers with the same interface                                   |
+| [`BinaryType`](#binarytype)                                       | `#!cpp std::vector<std::uint8_t>` | `#!cpp std::vector<char>`                                             |
+| [`CustomBaseClass`](#custombaseclass)                             | `void`                            | any default-constructible class                                       |
+
+!!! warning "Third-party containers and incomplete types"
+
+    `object_t` is instantiated inside the definition of `basic_json` -- it is probed for a `key_compare` member to
+    form [`object_comparator_t`](../../api/basic_json/object_comparator_t.md) -- i.e. while `basic_json` is still an
+    incomplete type. `#!cpp std::map` is required by the standard to support incomplete mapped types; most
+    third-party maps are not, and inspecting the mapped type at class scope (for instance with
+    `#!cpp std::is_trivially_move_assignable`) makes them unusable as `ObjectType`, no matter how their template
+    arguments are adapted. This rules out `absl::btree_map`, `phmap::btree_map`, `gtl::btree_map`,
+    `robin_hood::unordered_node_map`, `folly::F14FastMap`, and `eastl::hash_map`.
+
+    `array_t` is only *named* in the class definition and is not instantiated until `basic_json` is complete, so an
+    `ArrayType` that inspects its value type at class scope is generally fine -- `boost::container::small_vector` and
+    `static_vector` both reject incomplete value types yet work here. `absl::InlinedVector` is the exception: the
+    `#!cpp std::is_trivially_move_assignable<basic_json>` it evaluates while instantiating itself re-enters the
+    library's own trait machinery mid-instantiation.
+
+!!! note "Folly requires C++20"
+
+    Folly's headers use `#!cpp consteval` and `#!cpp std::type_identity`, so any `basic_json` specialization that
+    names a Folly type has to be compiled as C++20 or later, whatever the rest of the library supports.
+
+## `ObjectType`
+
+`ObjectType` is instantiated as
+
+```cpp
+using object_t = ObjectType<StringType,                                    // key_type
+                            basic_json,                                    // mapped_type
+                            default_object_comparator_t,                   // key_compare
+                            AllocatorType<std::pair<const StringType,
+                                                    basic_json>>>;         // allocator_type
+```
+
+i.e., the template arguments follow the order and meaning of `std::map`.
+
+### Always required
+
+- The template must be usable with **four** type arguments in the order shown above. The third argument is a
+  **comparator**; containers that expect something else in this position (e.g., a hash function) need an alias template
+  or wrapper -- see [Notes](#notes).
+- An optional member type `key_compare`. If it is present it becomes
+  [`object_comparator_t`](../../api/basic_json/object_comparator_t.md); otherwise
+  [`default_object_comparator_t`](../../api/basic_json/default_object_comparator_t.md) is used.
+- Member types `key_type`, `mapped_type`, `value_type`, and `iterator`.
+- `value_type` must behave like `#!cpp std::pair<const key_type, mapped_type>`; the library accesses `.first` and
+  `.second` on it.
+- `iterator` must be default-constructible and satisfy
+  [LegacyBidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator). The type returned
+  by `cbegin()`/`cend()` must satisfy the same requirements.
+- Constructors: default, copy, move, and from an iterator range `(first, last)`.
+- Member functions `begin()`, `end()`, `cbegin()`, `cend()`, `empty()`, `size()`, `max_size()`, `clear()`,
+  `find(key)`, `count(key)`, `emplace(key, value)`, `insert(value_type)`, `insert(first, last)`, `operator[](key)`,
+  `erase(iterator)`, and `erase(first, last)`. `erase(iterator)` may return the following iterator or `#!cpp void`;
+  in the latter case the library computes the successor itself, before erasing.
+- `erase(key)` is **optional**: if the container does not provide one, the library falls back to `find(key)` followed
+  by `erase(iterator)`.
+- `at(key)` is required only by [`to_ubjson`](../../api/basic_json/to_ubjson.md) and
+  [`to_bjdata`](../../api/basic_json/to_bjdata.md), but every container tried here provides it.
+- `emplace` and `insert(value_type)` must return `#!cpp std::pair<iterator, bool>` and must have **unique-key**
+  semantics; multimaps cannot be used.
+- The type must be swappable (via `std::swap` or an ADL `swap`).
+- The comparison operators `==` and `<`; `!=`, `<=`, `>`, and `>=` are derived from them. Where the library uses
+  three-way comparison (C++20), `==` and `<=>` are required **instead** -- the six two-way operators do not satisfy
+  it. They implement [`basic_json`'s comparison operators](../../api/basic_json/operator_eq.md).
+
+### Required for heterogeneous key lookup
+
+The overloads of [`at`](../../api/basic_json/at.md), [`operator[]`](../../api/basic_json/operator%5B%5D.md),
+[`find`](../../api/basic_json/find.md), [`contains`](../../api/basic_json/contains.md),
+[`count`](../../api/basic_json/count.md), [`erase`](../../api/basic_json/erase.md), and
+[`value`](../../api/basic_json/value.md) that accept a key type other than `object_t::key_type` require
+
+- a **transparent** comparator, i.e. [`object_comparator_t`](../../api/basic_json/object_comparator_t.md) has a member
+  type `is_transparent` (this is why the default comparator is `#!cpp std::less<>` since C++14), and
+- corresponding heterogeneous `find`, `count`, `erase`, and `operator[]` overloads on the container.
+
+### Notes
+
+#### `std::unordered_map` needs an adapter
+
+`#!cpp std::unordered_map` cannot be passed directly: its third template parameter is a hash function, but
+`basic_json` passes a comparator in that position. An alias template or wrapper that restores the expected argument
+order makes it usable:
+
+```cpp
+template<class Key, class T, class IgnoredCompare, class Allocator>
+struct unordered_map_object
+    : std::unordered_map<Key, T, std::hash<Key>, std::equal_to<Key>, Allocator>
+{
+    using base_t = std::unordered_map<Key, T, std::hash<Key>, std::equal_to<Key>, Allocator>;
+    using base_t::base_t;
+};
+
+using unordered_json = nlohmann::basic_json<unordered_map_object>;
+```
+
+Whether `#!cpp std::unordered_map` can be instantiated at all depends on the standard library: `object_t` is formed
+while `basic_json` is still incomplete (see the warning above), and libstdc++ 9 needs the size of the mapped type to
+instantiate the hash map's node type, so the adapter does not compile there. Newer libstdc++ versions, and the hash
+maps listed below, do not have that problem.
+
+The adapter above works verbatim for Abseil's, Boost's, `phmap`'s and `gtl`'s hash maps, which all place the hash
+function third and take a `#!cpp std::pair<const Key, T>` allocator fifth. Two need a different adapter:
+
+- `ankerl::unordered_dense` expects an allocator over `#!cpp std::pair<Key, T>` (non-const key), so the allocator has
+  to be rebound to that or dropped.
+- `robin_hood`'s fifth parameter is the non-type `MaxLoadFactor100`, so its adapter must drop the allocator entirely.
+
+None of these hash maps defines `key_compare`, so all of them additionally rely on `object_comparator_t` falling back
+to [`default_object_comparator_t`](../../api/basic_json/default_object_comparator_t.md); see
+[`object_comparator_t`](../../api/basic_json/object_comparator_t.md).
+
+#### Abseil hash maps
+
+`absl::flat_hash_map` and `absl::node_hash_map` tolerate an incomplete value type, but they take a hash function as
+their third template argument. The same adapter as for `#!cpp std::unordered_map` makes them usable:
+
+```cpp
+template<class Key, class T, class IgnoredCompare, class Allocator>
+struct flat_hash_object
+    : absl::flat_hash_map<Key, T, absl::Hash<Key>, std::equal_to<Key>, Allocator>
+{
+    using base_t = absl::flat_hash_map<Key, T, absl::Hash<Key>, std::equal_to<Key>, Allocator>;
+    using base_t::base_t;
+};
+
+using flat_hash_json = nlohmann::basic_json<flat_hash_object>;
+```
+
+`absl::node_hash_map` keeps references to the mapped values valid across insertions; `absl::flat_hash_map` does not,
+which makes it behave like [`ordered_json`](../../api/ordered_json.md) with respect to
+[iterator invalidation](../../api/basic_json/index.md#iterator-invalidation). Both expose a `capacity()` member
+function, so [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md) treats them conservatively and keeps the
+parent pointers correct either way.
+
+#### Iteration order
+
+The library never relies on the container's iteration order for correctness; it does determine the order in which
+object keys are serialized by [`dump`](../../api/basic_json/dump.md) and visited by
+[`items`](../../api/basic_json/items.md). See [Object Order](../object_order.md).
+
+#### `capacity()` marks a container as insertion-ordered
+
+With [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md) enabled, the library detects insertion-ordered maps by
+probing for a `capacity()` member function (`nlohmann::ordered_map` inherits it from `std::vector`) and refreshes all
+parent pointers after every insertion. An `ObjectType` that happens to have a `capacity()` member is therefore treated
+conservatively -- this is correct, but slower.
+
+#### Key order and duplicate keys
+
+The library does not sort or de-duplicate keys itself; the behavior described in
+[`object_t`](../../api/basic_json/object_t.md) is entirely the behavior of the chosen container.
+
+!!! tip "Reference implementation"
+
+    `docs/mkdocs/docs/examples/custom_object_type.hpp` wraps a private `#!cpp std::map` and satisfies every
+    requirement above. It does not define `key_compare`, so `object_comparator_t` falls back to
+    [`default_object_comparator_t`](../../api/basic_json/default_object_comparator_t.md) -- a good starting point for
+    a custom `ObjectType`.
+
+    ```cpp
+    --8<-- "examples/custom_object_type.hpp"
+    ```
+
+??? example "Compiling and using it"
+
+    ```cpp
+    --8<-- "examples/custom_object_type.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/custom_object_type.output"
+    ```
+
+### Compatible containers
+
+| Container                                                                        | Notes                                                                         |
+|----------------------------------------------------------------------------------|-------------------------------------------------------------------------------|
+| `#!cpp std::map` (default)                                                       |                                                                               |
+| [`nlohmann::ordered_map`](../../api/ordered_map.md)                              | used by [`ordered_json`](../../api/ordered_json.md); keeps insertion order    |
+| [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map)                     | keeps insertion order; adapter puts `fifo_map_compare` in the comparator slot |
+| `boost::container::map`, `boost::container::flat_map`                            | no adapter needed                                                             |
+| `#!cpp std::unordered_map`                                                       | through the adapter above; not with libstdc++ 9, see the note                 |
+| `boost::unordered_map`, `boost::unordered_flat_map`, `boost::unordered_node_map` | through the adapter above                                                     |
+| `absl::flat_hash_map`, `absl::node_hash_map`                                     | through the adapter above; `flat_hash_map` moves mapped values on rehash      |
+| `phmap::flat_hash_map`, `phmap::node_hash_map`, `gtl::flat_hash_map`             | through the adapter above                                                     |
+| `ankerl::unordered_dense::map` and `segmented_map`                               | adapter must rebind or drop the allocator                                     |
+| `robin_hood::unordered_flat_map`                                                 | adapter must drop the allocator                                               |
+| `folly::F14NodeMap`                                                              | through the adapter above; requires C++20, see the note above                 |
+| `folly::sorted_vector_map`                                                       | alias must drop the allocator, whose value type it disagrees on               |
+
+### Containers that cannot be used
+
+| Container                                                                | Reason                                                                                                              |
+|--------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------|
+| `absl::btree_map`, `phmap::btree_map`, `gtl::btree_map`                  | require a complete mapped type                                                                                      |
+| `robin_hood::unordered_node_map`, `folly::F14FastMap`, `eastl::hash_map` | require a complete mapped type                                                                                      |
+| `eastl::map`                                                             | EASTL iterators do not work with `#!cpp std::iterator_traits`                                                       |
+| `tsl::ordered_map`                                                       | its iterators expose the mapped value as `#!cpp const`                                                              |
+| `QMap`                                                                   | no `value_type` member type                                                                                         |
+| `QHash`                                                                  | its `value_type` is the mapped type rather than a key/value pair, and its iterators dereference to the mapped value |
+| `#!cpp std::multimap`, `#!cpp std::unordered_multimap`                   | `emplace` does not return `#!cpp std::pair<iterator, bool>`                                                         |
+
+## `ArrayType`
+
+`ArrayType` is instantiated as
+
+```cpp
+using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
+```
+
+### Always required
+
+- The template must be usable with **two** type arguments (value type and allocator).
+- Member types `value_type` and `iterator`.
+- Constructors: default, copy, and move; and from an iterator range `(first, last)`.
+- Member functions `begin()`, `end()`, `cbegin()`, `cend()`, `empty()`, `size()`, `max_size()`, `clear()`,
+  `operator[](size_type)`, `back()`, `push_back()`, `emplace_back()`, `pop_back()`, `resize()`,
+  `insert()` (single element, count, and range), `erase(pos)`, and `erase(first, last)`.
+  `basic_json::insert(pos, initializer_list)` goes through the range overload, so no initializer-list `insert` is
+  needed. `at(size_type)` is **not** required: [`basic_json::at(size_type)`](../../api/basic_json/at.md) checks the
+  index itself and then uses `operator[]`.
+- `iterator` must be default-constructible, and it as well as the type returned by `cbegin()`/`cend()` must satisfy
+  [LegacyRandomAccessIterator](https://en.cppreference.com/w/cpp/named_req/RandomAccessIterator).
+  A `#!cpp static_assert` only checks for
+  [LegacyBidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator), but
+  [`dump`](../../api/basic_json/dump.md) (`cend() - 1`),
+  [`erase(idx)`](../../api/basic_json/erase.md) (`begin() + idx`), and the random-access operations of
+  [`basic_json::iterator`](../../api/basic_json/begin.md) require random access.
+- The comparison operators, as for [`ObjectType`](#objecttype): `==` and `<`, or `==` and `<=>` under C++20.
+
+### Required for individual functions
+
+- A member type `value_type`, for [`to_bson`](../../api/basic_json/to_bson.md) of an array.
+- A constructor from `(count, value)`, for
+  [`basic_json(size_type, const basic_json&)`](../../api/basic_json/basic_json.md).
+- Swappability, via `#!cpp std::swap` or an ADL `swap`, for [`swap(array_t&)`](../../api/basic_json/swap.md).
+
+!!! note "`capacity()` is optional"
+
+    With [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md) enabled, the library reads `array_t::capacity()`
+    to find out whether adding an element reallocated the array and moved its elements, which would invalidate the
+    parent pointers. An array type without a `capacity()` member function is handled conservatively: the parent
+    pointers of all elements are refreshed after every insertion, which makes adding *n* elements cost O(*n*²). Only
+    diagnostics builds pay this; without them `capacity()` is never called.
+
+!!! tip "Reference implementation"
+
+    `docs/mkdocs/docs/examples/custom_array_type.hpp` wraps a private `#!cpp std::vector` and satisfies every
+    requirement above -- a good starting point for a custom `ArrayType`.
+
+    ```cpp
+    --8<-- "examples/custom_array_type.hpp"
+    ```
+
+??? example "Compiling and using it"
+
+    ```cpp
+    --8<-- "examples/custom_array_type.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/custom_array_type.output"
+    ```
+
+### Compatible containers
+
+| Container                                               | Notes                                                                                     |
+|---------------------------------------------------------|-------------------------------------------------------------------------------------------|
+| `#!cpp std::vector` (default)                           |                                                                                           |
+| `#!cpp std::deque`                                      | references survive appends, but not insertions elsewhere; see the `capacity()` note above |
+| `#!cpp std::pmr::vector`                                | through an alias, as the allocator comes from `AllocatorType` instead                     |
+| `boost::container::vector`, `deque`, `devector`         |                                                                                           |
+| `boost::container::stable_vector`                       | the only one tried that keeps references valid across *every* insertion                   |
+| `boost::container::small_vector`, `folly::small_vector` | through an alias that fixes the inline capacity                                           |
+| `boost::container::static_vector`                       | through the same kind of alias, for arrays that stay within the fixed capacity            |
+| `folly::fbvector`                                       | requires C++20, see the note above                                                        |
+
+### Containers that cannot be used
+
+| Container                           | Reason                                                                                        |
+|-------------------------------------|-----------------------------------------------------------------------------------------------|
+| `#!cpp std::list`                   | no `operator[]`, and no random-access iterators                                               |
+| `eastl::vector`, `QList`, `QVector` | no `max_size()`; they handle the incomplete value type fine                                   |
+| `absl::InlinedVector`               | requires a complete value type, see the note above                                            |
+| `absl::FixedArray`                  | the size is fixed at construction, so `resize`, `push_back`, `insert` and `erase` are missing |
+
+## `StringType`
+
+`StringType` is used **both** for JSON string values and for the keys of JSON objects
+(`string_t` and `object_t::key_type`).
+
+### Always required
+
+- A member type `value_type` that is one byte wide and `char`-compatible. The library stores and processes UTF-8
+  encoded `char` data and hands `data()` to `#!cpp std::strtoull`/`#!cpp std::strtoll`.
+  `#!cpp std::wstring`, `#!cpp std::u16string`, and `#!cpp std::u32string` are **not** valid choices; see the FAQ on
+  [wide string handling](../../home/faq.md#wide-string-handling).
+- Constructors: default, copy, move, from `#!cpp const char*` (which must not be `#!cpp explicit`), from
+  `#!cpp (const char*, size_type)`, and from `#!cpp (size_type, char)`; and copy or move assignment.
+- Member functions `size()`, `clear()`, `resize(n, c)`, `data()`, `push_back(char)`, and `operator[]`
+  (const and non-const, returning references). `c_str()` and `back()` are **not** required.
+- `data()` must return a pointer to a contiguous, **null-terminated** buffer -- the parser hands it to
+  `#!cpp std::strtoull`. A type whose `data()` is not null-terminated does not fail to compile; it silently
+  misparses numbers.
+- `append(const char*, size_type)`, used by [`dump`](../../api/basic_json/dump.md), and `append(const StringType&)`,
+  used by the CBOR reader for indefinite-length strings. The library's internal string concatenation additionally has
+  to append a `#!cpp char` and a `#!cpp const char*`; for each it selects between `append(arg)`, `#!cpp operator+=`,
+  `append(first, last)`, and `append(data, size)`.
+- The comparison operator `==` against another `StringType`, and `<` for use as a key of the chosen
+  [`ObjectType`](#objecttype) (with the default comparator, `#!cpp std::less<>` must be able to compare two
+  `StringType` values, and a `StringType` with the key types used for lookup). `!=` is never applied to a
+  `StringType`, and `==` against `#!cpp const char*` is resolved by the implicit `#!cpp const char*` constructor.
+
+### Required for the binary formats
+
+- `resize(n)`, used by the readers to make room for a block of bytes.
+- Non-const `operator[]`, into which the readers `#!cpp std::memcpy` those bytes. A non-`#!cpp const` `data()` would
+  serve just as well, but `#!cpp std::string` has only had one since C++17, and the library still supports C++11.
+
+### Required for JSON Pointer, `flatten`, and `diff`
+
+- A static member `npos` and the member function `find_first_of(char, size_type)` -- together with `data()`,
+  `reserve(n)`, and `append(const char*, size_type)` they implement the escaping and unescaping of reference tokens
+  described in RFC 6901. Neither `find(const StringType&, size_type)`, nor `substr(pos, count)`, nor
+  `replace(pos, count, const StringType&)` is required.
+- `empty()`.
+- `begin()` and `end()` -- used by
+  [`operator[](const json_pointer&)`](../../api/basic_json/operator%5B%5D.md) to decide whether a reference token
+  denotes an array index.
+
+### Required for other functionality
+
+| Functionality                                                                                                                     | Additional requirement                                                                                                                                                                       |
+|-----------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| [`diff`](../../api/basic_json/diff.md), [`items`](../../api/basic_json/items.md), [`std::hash`](../../api/basic_json/std_hash.md) | conversion of a `#!cpp std::size_t` to `StringType`: either assignability from the result of `#!cpp std::to_string`, or an ADL overload `#!cpp void int_to_string(StringType&, std::size_t)` |
+| [`std::hash<basic_json>`](../../api/basic_json/std_hash.md)                                                                       | additionally a specialization of `#!cpp std::hash<StringType>`                                                                                                                               |
+| [`to_bson`](../../api/basic_json/to_bson.md)                                                                                      | `find(value_type)` and `npos`                                                                                                                                                                |
+| [`parse`](../../api/basic_json/parse.md) from a `string_t`                                                                        | the input adapters must accept it; otherwise pass a character range                                                                                                                          |
+| `#!cpp operator<<(std::ostream&, const json_pointer&)`                                                                            | streamability to `#!cpp std::ostream`                                                                                                                                                        |
+| exception messages                                                                                                                | `data()` and `size()`, or `begin()` and `end()`                                                                                                                                              |
+
+### Compatible types
+
+| Type                                                            | Notes                                                                                                                                                                                                                                         |
+|-----------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `#!cpp std::string` (default)                                   |                                                                                                                                                                                                                                               |
+| `#!cpp std::basic_string` with a custom **stateless** allocator |                                                                                                                                                                                                                                               |
+| `#!cpp std::pmr::string`                                        | see the warning below before relying on the memory resource                                                                                                                                                                                   |
+| `boost::container::string`                                      | needs a user-supplied `#!cpp std::hash` specialization (Boost provides `boost::hash` instead)                                                                                                                                                 |
+| `folly::fbstring`                                               | requires C++20, see the note above                                                                                                                                                                                                            |
+| `eastl::string`                                                 | needs a user-supplied `#!cpp std::hash` and an ADL `int_to_string` (it is not assignable from a `#!cpp std::string`); [`parse`](../../api/basic_json/parse.md) does not accept it directly -- pass a character range or a `#!cpp std::string` |
+| a custom string class in a user-defined namespace               | if the requirements above are met                                                                                                                                                                                                             |
+
+### Types that cannot be used
+
+| Type                                                                 | Reason                                                                                                  |
+|----------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------|
+| `#!cpp std::wstring`, `#!cpp std::u16string`, `#!cpp std::u32string` | the character type is not one byte wide                                                                 |
+| `#!cpp std::u8string`                                                | one byte wide, but `#!cpp char8_t` is not `#!cpp char`-compatible                                       |
+| `absl::Cord`                                                         | no `value_type`, and the storage is not contiguous                                                      |
+| `QString`                                                            | no `append(const char*, size_type)`; its `QChar` is also two bytes wide, though that is never diagnosed |
+
+!!! warning "A `std::pmr::string` mostly does not use the memory resource you choose"
+
+    `basic_json` cannot be given an allocator or a memory resource. `AllocatorType` is default-constructed at every
+    allocation and has to be stateless (see [`AllocatorType`](#allocatortype)), and string values the library creates
+    are constructed with their own default allocator. So:
+
+    - Every string the library itself produces -- from [`parse`](../../api/basic_json/parse.md), from
+      [`dump`](../../api/basic_json/dump.md), or by default construction -- allocates from
+      `#!cpp std::pmr::get_default_resource()`.
+    - **Copying** an arena-backed string into a value silently drops its memory resource: the copy lands on the
+      default resource, because `#!cpp std::pmr::polymorphic_allocator` does not propagate on copy construction.
+      Nothing warns about this.
+    - **Moving** one in does keep it, and later growth still allocates from that arena -- but it does not survive a
+      copy of the enclosing `basic_json`.
+    - Passing `#!cpp std::pmr::polymorphic_allocator` as `AllocatorType` does not work around any of this; it does
+      not compile.
+
+    Apart from moving a string in, the only way to redirect these allocations is the process-global
+    `#!cpp std::pmr::set_default_resource()`.
+
+!!! tip "Reference implementation"
+
+    `docs/mkdocs/docs/examples/custom_string_type.hpp` wraps a private `#!cpp std::string` and satisfies every
+    requirement above -- a good starting point for a custom `StringType`. The unit test
+    `tests/src/unit-alt-string.cpp` contains a more thorough variant, `alt_string`, exercised against a larger part
+    of the API.
+
+    ```cpp
+    --8<-- "examples/custom_string_type.hpp"
+    ```
+
+??? example "Compiling and using it"
+
+    ```cpp
+    --8<-- "examples/custom_string_type.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/custom_string_type.output"
+    ```
+
+## `BooleanType`
+
+`boolean_t` is stored **directly** inside `basic_json`, as a member of an anonymous union.
+
+### Always required
+
+- A literal type that is trivially default-constructible, trivially copyable, and trivially destructible; otherwise the
+  union's special member functions are deleted.
+- **Implicitly** convertible from `#!cpp bool` -- an `#!cpp explicit` constructor is not enough, because the
+  `to_json` overload for a custom `BooleanType` is constrained on `#!cpp std::is_convertible` -- and contextually
+  convertible to `#!cpp bool` (here an `#!cpp explicit operator bool` is fine).
+- Comparison operators `==`, `!=`, `<`, `<=`, `>`, `>=` (or `<=>`).
+- Convertible from and to `#!cpp bool` through the serializer, because
+  [`get<bool>()`](../../api/basic_json/get.md) is used internally.
+
+There is little reason to use anything other than `#!cpp bool` here.
+
+### Compatible types
+
+`#!cpp bool` is the only usable choice. Another trivially copyable type that is implicitly convertible to and from
+`#!cpp bool` -- `#!cpp std::uint8_t`, say -- does compile, and JSON booleans still round-trip, but the type then
+serves as both `boolean_t` and an ordinary integer: `basic_json` can no longer be constructed or assigned from a
+`#!cpp std::uint8_t` at all (the boolean and unsigned-integer `to_json` overloads become ambiguous), and
+[`get<std::uint8_t>()`](../../api/basic_json/get.md) on a number throws
+[`type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302) instead of returning the value.
+
+## `NumberIntegerType` and `NumberUnsignedType`
+
+Both types are stored **directly** inside `basic_json`'s union.
+
+### Always required
+
+- `#!cpp std::is_integral` must be satisfied: `NumberIntegerType` must be a **signed** integer type,
+  `NumberUnsignedType` an **unsigned** integer type. Class types are not supported -- among others, the constructors
+  taking integer values are constrained on `#!cpp std::is_integral`.
+- Trivially default-constructible, trivially copyable, and trivially destructible (union member).
+- `#!cpp std::numeric_limits` must be specialized for both types.
+- `NumberUnsignedType` must be able to represent the absolute value of every `NumberIntegerType` value; serialization
+  of negative numbers converts the value to `NumberUnsignedType`. A `#!cpp static_assert` requires it to be at least as
+  wide as `NumberIntegerType`, which is what that amounts to for the standard integer types.
+- Both types must fit into the internal 64-character number buffer used by
+  [`dump`](../../api/basic_json/dump.md), which is the case for all standard integer types.
+- [`std::hash<basic_json>`](../../api/basic_json/std_hash.md) additionally requires `#!cpp std::hash` specializations.
+
+### Notes
+
+The number types influence what the parser accepts: an integer literal that does not round-trip through the chosen type
+is stored as [`number_float_t`](../../api/basic_json/number_float_t.md) instead. Choosing types narrower than 64 bits
+therefore silently changes parse results rather than raising an error. See
+[Number Handling](number_handling.md) for details.
+
+### Compatible types
+
+| Type pair                                                                                    | Support                                                                                                                                                                                          |
+|----------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `#!cpp std::int64_t` / `#!cpp std::uint64_t` (default)                                       | full                                                                                                                                                                                             |
+| `#!cpp std::int32_t` / `#!cpp std::uint32_t`, `#!cpp long long` / `#!cpp unsigned long long` | full; narrower types change which literals the parser can represent                                                                                                                              |
+| any other pair of standard signed/unsigned integer types                                     | full                                                                                                                                                                                             |
+| class types, enumerations                                                                    | not usable; `#!cpp std::is_integral` must hold                                                                                                                                                   |
+| `#!cpp bool`, or a type already used for another member of the union                         | not usable; `#!cpp std::is_integral<bool>` is in fact `#!cpp true`, but the `get_impl_ptr` overloads for `boolean_t`, `number_integer_t`, `number_unsigned_t` and `number_float_t` would collide |
+
+## `NumberFloatType`
+
+`number_float_t` is stored **directly** inside `basic_json`'s union.
+
+### Always required
+
+- Trivially default-constructible, trivially copyable, and trivially destructible (union member).
+- `#!cpp std::numeric_limits` must be specialized; `max_digits10` is used to size the conversion.
+- `#!cpp std::isfinite` must be applicable to the type.
+
+### Required for parsing and serialization
+
+`NumberFloatType` must be one of `#!cpp float`, `#!cpp double`, or `#!cpp long double`:
+
+- The [parser](../parsing/index.md) converts number literals with `#!cpp std::strtof`, `#!cpp std::strtod`, or
+  `#!cpp std::strtold`; the library provides overloads for exactly these three types.
+- [`dump`](../../api/basic_json/dump.md) falls back to `#!cpp std::snprintf` with the `%g` and `%Lg` conversion
+  specifiers, for which the library likewise provides only `#!cpp double` and `#!cpp long double` overloads
+  (`#!cpp float` is promoted to `#!cpp double`).
+
+If `#!cpp std::numeric_limits<NumberFloatType>` describes an IEEE 754 binary32 or binary64 number, `dump` uses the
+Grisu2 algorithm, which produces the shortest representation that round-trips. Otherwise the `snprintf` fallback with
+`max_digits10` digits is used.
+
+### Required for the binary formats
+
+`NumberFloatType` must be `#!cpp float` or `#!cpp double`. The writers for
+[CBOR, MessagePack, UBJSON, BJData, and BSON](../binary_formats/index.md) map a floating-point value onto an IEEE 754
+binary32 or binary64 field and have no encoding for `#!cpp long double`.
+
+### Compatible types
+
+| Type                     | Support                                                                                                               |
+|--------------------------|-----------------------------------------------------------------------------------------------------------------------|
+| `#!cpp double` (default) | full; short round-trip output through Grisu2                                                                          |
+| `#!cpp float`            | full; short round-trip output through Grisu2                                                                          |
+| `#!cpp long double`      | `dump` and `parse` only; the binary format writers do not compile, as they only handle IEEE 754 binary32 and binary64 |
+| any other type           | not usable                                                                                                            |
+
+## `AllocatorType`
+
+`AllocatorType` is instantiated with **one** argument, for each of `object_t`, `array_t`, `string_t`, `binary_t`,
+`basic_json`, and `#!cpp std::pair<const StringType, basic_json>`.
+
+### Always required
+
+- The template must be usable with exactly one type argument. The library instantiates `AllocatorType<T>` directly and
+  never uses `#!cpp std::allocator_traits<...>::rebind_alloc`.
+- It must satisfy the [Allocator](https://en.cppreference.com/w/cpp/named_req/Allocator) named requirement so that
+  `#!cpp std::allocator_traits` can be used with it.
+- It must be **default-constructible and stateless**. Objects are allocated with a default-constructed allocator and
+  deallocated with a *different* default-constructed allocator, and
+  [`get_allocator()`](../../api/basic_json/get_allocator.md) returns a default-constructed instance. Allocators
+  carrying state are not supported, so there is no way to tell a `basic_json` where to allocate from; see the note
+  under [`StringType`](#stringtype) for what that means in practice. A stateful allocator is **not diagnosed**: it
+  compiles and silently ignores the state.
+- It must support **incomplete types**: `AllocatorType<basic_json>` is instantiated inside the definition of
+  `basic_json` itself.
+- `#!cpp std::allocator_traits<AllocatorType<basic_json>>::pointer` becomes
+  [`basic_json::pointer`](../../api/basic_json/index.md#container-types), and iterators are constructed from raw
+  `#!cpp basic_json*` values. The `pointer` type must therefore be a plain pointer; fancy pointers are not supported.
+
+### Compatible types
+
+| Type                                                              | Support                                |
+|-------------------------------------------------------------------|----------------------------------------|
+| `#!cpp std::allocator` (default)                                  | full                                   |
+| a custom stateless allocator template                             | full                                   |
+| stateful allocators, e.g. `#!cpp std::pmr::polymorphic_allocator` | not usable; see the requirements above |
+
+## `JSONSerializer`
+
+`JSONSerializer` is instantiated as `JSONSerializer<T, void>` and defaults to
+[`adl_serializer`](../../api/adl_serializer/index.md).
+
+### Always required
+
+- The template must accept **two** type arguments. It does not have to give the second one a default -- `basic_json`
+  declares the parameter as `#!cpp template<typename T, typename SFINAE = void> class JSONSerializer`, so uses such as
+  `#!cpp JSONSerializer<T>` inside the library supply `#!cpp void` themselves. The second parameter exists so that
+  partial specializations can be constrained by SFINAE.
+- For every type `T` that is converted **to** a JSON value, a static member function
+  `#!cpp static void to_json(basic_json&, T)` must exist.
+- For every type `T` that is converted **from** a JSON value, either
+  `#!cpp static void from_json(const basic_json&, T&)` or `#!cpp static T from_json(const basic_json&)` must exist.
+  The latter form is required for types that are not default-constructible; see
+  [Arbitrary Types Conversions](../arbitrary_types.md).
+- To support the [converting constructor](../../api/basic_json/basic_json.md) between different `basic_json`
+  specializations, `to_json` must be available for `boolean_t`, `number_integer_t`, `number_unsigned_t`,
+  `number_float_t`, `string_t`, `object_t`, `array_t`, and `binary_t` of the *source* specialization.
+
+### Compatible types
+
+| Type                                                                      | Support                                                           |
+|---------------------------------------------------------------------------|-------------------------------------------------------------------|
+| [`nlohmann::adl_serializer`](../../api/adl_serializer/index.md) (default) | full                                                              |
+| a class template deriving from `adl_serializer`                           | full; the usual way to change behavior while keeping the defaults |
+| an unrelated template with the same interface                             | full, but it has to handle every type the library converts        |
+
+## `BinaryType`
+
+`BinaryType` is not a JSON type; it is used for the byte strings of the
+[binary formats](../binary_formats/index.md). It is wrapped as
+
+```cpp
+using binary_t = nlohmann::byte_container_with_subtype<BinaryType>;
+```
+
+### Always required
+
+- A non-`final` class type -- [`byte_container_with_subtype`](../../api/byte_container_with_subtype/index.md) derives
+  from it publicly.
+- A member type `value_type` that is **exactly one byte** wide (e.g., `#!cpp std::uint8_t`, `#!cpp char`, or
+  `#!cpp std::byte`). Readers and writers reinterpret the container's storage as raw bytes, so a wider `value_type` is
+  rejected with a `#!cpp static_assert`.
+- Contiguous storage: the binary readers `#!cpp std::memcpy` into `#!cpp &binary[n]`, the writers `reinterpret_cast`
+  `data()`. `#!cpp data() + n` would do for the readers too, but they share one helper with
+  [`StringType`](#stringtype), whose non-`#!cpp const` `data()` is C++17 and later only.
+- Default-constructible, copy-constructible, and move-constructible.
+- Member functions `size()`, `empty()`, `data()`, `resize()`, `operator[]`, `back()`, `begin()`, `end()`, `cbegin()`,
+  and `cend()` with random-access iterators, and `insert(pos, first, last)`, which the CBOR reader uses to join the
+  chunks of an indefinite-length byte string. `push_back()` is **not** required.
+- Comparison operators: `==` is used by
+  [`byte_container_with_subtype`](../../api/byte_container_with_subtype/index.md), the relational operators by
+  [`basic_json`'s comparison operators](../../api/basic_json/operator_le.md).
+
+### Required for individual functions
+
+- `clear()`, for [`basic_json::clear()`](../../api/basic_json/clear.md).
+
+`max_size()`, `at()`, `reserve()`, `erase()`, `pop_back()`, and `emplace_back()` are **not** used at all.
+
+See [`binary_t`](../../api/basic_json/binary_t.md) for how a non-default `BinaryType` changes the meaning of assigning
+such a container to a `basic_json` value.
+
+!!! tip "Reference implementation"
+
+    `docs/mkdocs/docs/examples/custom_binary_type.hpp` wraps a private `#!cpp std::vector<std::uint8_t>` and satisfies
+    every requirement above -- a good starting point for a custom `BinaryType`.
+
+    ```cpp
+    --8<-- "examples/custom_binary_type.hpp"
+    ```
+
+??? example "Compiling and using it"
+
+    ```cpp
+    --8<-- "examples/custom_binary_type.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/custom_binary_type.output"
+    ```
+
+### Compatible containers
+
+| Container                                                                                   | Notes                                                                     |
+|---------------------------------------------------------------------------------------------|---------------------------------------------------------------------------|
+| `#!cpp std::vector<std::uint8_t>` (default)                                                 |                                                                           |
+| `#!cpp std::vector<char>`, `#!cpp std::vector<std::byte>`                                   | `dump()` writes the bytes as 0..255 whichever is used                     |
+| `boost::container::vector<std::uint8_t>`, `boost::container::small_vector<std::uint8_t, N>` |                                                                           |
+| `absl::InlinedVector<std::uint8_t, N>`                                                      | usable here, unlike as an `ArrayType`, because the value type is complete |
+| `eastl::vector<std::uint8_t>`                                                               | usable here, unlike as an `ArrayType`, because `max_size()` is not needed |
+| `folly::fbvector<std::uint8_t>`                                                             | requires C++20, see the note above                                        |
+
+### Containers that cannot be used
+
+| Container                                            | Reason                                                                                                                                                                                             |
+|------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `QByteArray`                                         | no `empty()` (it spells that `isEmpty()`); its `insert` takes an index rather than an iterator; and it converts to `string_t`, which makes `to_json` ambiguous between a string and a binary value |
+| `#!cpp std::string`                                  | `binary_t::container_type` and `string_t` would be the same type, so the two [`swap`](../../api/basic_json/swap.md) overloads collide and `basic_json` cannot be instantiated at all               |
+| `#!cpp std::deque<std::uint8_t>`                     | storage is not contiguous, so there is no `data()`                                                                                                                                                 |
+| containers whose `value_type` is wider than one byte | see above -- accepted by the compiler, wrong at runtime                                                                                                                                            |
+
+## `CustomBaseClass`
+
+`CustomBaseClass` is an extension point: unless it is `#!cpp void` (the default, which selects the empty
+`nlohmann::json_default_base`), `basic_json` publicly derives from it.
+
+### Always required
+
+- A non-`final`, default-constructible class type.
+- `basic_json` is copy-/move-constructible and copy-/move-assignable only if `CustomBaseClass` is.
+
+### Notes
+
+`basic_json` is documented to be a
+[StandardLayoutType](https://en.cppreference.com/w/cpp/named_req/StandardLayoutType). Because `basic_json` has
+non-static data members of its own, a `CustomBaseClass` with non-static data members forfeits this guarantee.
+
+Note the namespace of `CustomBaseClass` becomes an associated namespace of `basic_json` for the purpose of
+argument-dependent lookup.
+
+See [`json_base_class_t`](../../api/basic_json/json_base_class_t.md) for an example.
+
+### Compatible types
+
+| Type                                         | Support                                                                    |
+|----------------------------------------------|----------------------------------------------------------------------------|
+| `#!cpp void` (default)                       | an empty base class is used; no effect on `basic_json`                     |
+| any default-constructible, non-`final` class | full; see [`json_base_class_t`](../../api/basic_json/json_base_class_t.md) |
+
+## Cross-specialization conversions
+
+Converting a value from one `basic_json` specialization into another (see the
+[converting constructor](../../api/basic_json/basic_json.md)) imposes two additional requirements that are not
+diagnosed at compile time. With assertions enabled they abort on the `#!cpp JSON_ASSERT` at the end of the converting
+constructor; under `#!cpp NDEBUG` they fail **silently** at runtime:
+
+- The target `string_t` must be directly constructible from the source `string_t`. Otherwise the string is converted to
+  an array of character codes.
+- The target `object_t::key_type` must be directly constructible from the source object's key type. Otherwise the
+  object is converted to an array of key/value pairs.
+
+See [issue #3425](https://github.com/nlohmann/json/issues/3425), [`string_t`](../../api/basic_json/string_t.md), and
+[`object_t`](../../api/basic_json/object_t.md).
+
+## See also
+
+- [Types](index.md) -- overview of how JSON values are stored
+- [Number Handling](number_handling.md) -- how the number types affect parsing and serialization
+- [Object Order](../object_order.md) -- using an insertion-ordered `ObjectType`
+- [`basic_json`](../../api/basic_json/index.md) -- API documentation of the class template

docs/mkdocs/docs/home/exceptions.md

@@ -340,8 +340,7 @@ An unexpected byte was read in a [binary format](../features/binary_formats/inde
 ### json.exception.parse_error.113
 
 A string could not be read from a [binary format](../features/binary_formats/index.md): either a value that is not a
-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.
+string was read where one was required (for instance as a map key), or the string's length specification is invalid.
 
 !!! failure "Example messages"
 
@@ -357,9 +356,6 @@ the string's bytes are not valid UTF-8.
     ```
     [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing BJData string: string length must not be negative
     ```
-    ```
-    [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR string: invalid string: ill-formed UTF-8 byte
-    ```
 
 ### json.exception.parse_error.114
 
@@ -974,6 +970,21 @@ A JSON Patch `move` operation's `"from"` location is a proper prefix of its `"pa
 
     This exception was added in version 3.13.0. Before that, this situation could succeed with a corrupted result: for an array target, removing the "from" element before the "add" step shifted subsequent indices, so "path" silently re-resolved to a different element than intended.
 
+### json.exception.out_of_range.415
+
+MessagePack's ext type and BSON's binary subtype are each stored in a single byte. This exception is thrown when serializing a
+[`byte_container_with_subtype`](../api/byte_container_with_subtype/index.md) whose subtype exceeds 255.
+
+!!! failure "Example message"
+
+    ```
+    [json.exception.out_of_range.415] subtype 70000 is too large for the MessagePack ext type (max 255)
+    ```
+
+!!! note
+
+    This exception was added in version 3.13.0. Before that, subtypes above 255 were silently truncated modulo 256 instead of raising an error.
+
 ## Further exceptions
 
 This exception is thrown in case of errors that cannot be classified with the

docs/mkdocs/docs/home/faq.md

@@ -90,6 +90,54 @@ The library supports **Unicode input** as follows:
 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.
 
 
+### NUL bytes in the input
+
+!!! question "Questions"
+
+    - Why does `json::parse()` silently ignore part of my input?
+    - Why does a `std::string`/buffer with extra data after the JSON text parse without error, while a similar-looking string with extra text does not?
+
+A `'\0'` (NUL) byte anywhere in the input is treated the same as the real end of the input, rather than as an ordinary (and, outside of a string, invalid) byte. Everything from that byte onward is silently ignored, without a parse error — including further, otherwise well-formed JSON:
+
+```cpp
+json::parse(std::string("123") + '\0');          // == 123, no error
+json::parse(std::string("123") + '\0' + "true"); // == 123, the "true" is silently ignored too
+```
+
+This is different from any other unexpected trailing byte, which *does* raise [`parse_error.101`](../home/exceptions.md#jsonexceptionparse_error101):
+
+```cpp
+json::parse("123x"); // throws parse_error.101: unexpected additional data
+```
+
+This falls out of the same convention used when no explicit input length is given at all: `json::parse(const char*)` already stops at the first NUL byte via `strlen()`, since a bare pointer has no length of its own. The library applies that same NUL-terminated-C-string convention uniformly, rather than only when a length is genuinely unavailable — so a `std::string`, iterator range, or container whose content happens to include a NUL byte is affected the same way a raw `const char*` would be.
+
+If your input may contain a trailing or embedded NUL that is **not** meant to signal the end of the JSON text — for instance, a fixed-size, zero-padded buffer — trim it yourself before calling `parse()`, since the library will otherwise silently stop there instead of raising an error:
+
+```cpp
+s.resize(s.find('\0')); // drop everything from the first NUL onward, if any
+json::parse(s);
+```
+
+**Opt-in strict handling (since version 3.13.0)**
+
+Manually trimming every input is easy to forget. If you define [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md) to `1` before including the library, a `'\0'` byte is instead rejected like any other unexpected byte and raises `parse_error.101`, instead of being treated as end of input:
+
+```cpp
+#define JSON_STRICT_NUL_HANDLING 1
+#include <nlohmann/json.hpp>
+
+json::parse(std::string("123") + '\0'); // throws parse_error.101 instead of silently returning 123
+```
+
+This macro defaults to `0` (disabled, preserving the behavior described above) to avoid breaking existing code that may depend on it, even unknowingly; it is planned to become the default in version 4.0.0. See [its documentation](../api/macros/json_strict_nul_handling.md) for details, including how it also affects `char` arrays such as string literals.
+
+Note that this is unrelated to an *unescaped* NUL byte occurring **inside** a quoted JSON string, which is a different, already-invalid case and is correctly rejected either way:
+
+```cpp
+json::parse(std::string("\"") + '\0' + "\""); // throws parse_error.101: control character U+0000 (NUL) must be escaped to \u0000
+```
+
 ### Wide string handling
 
 !!! question

docs/mkdocs/docs/integration/cmake.md

@@ -198,6 +198,11 @@ Use the non-amalgamated version of the library. This option is `ON` by default.
 
 Treat the library headers like system headers (i.e., adding `SYSTEM` to the [`target_include_directories`](https://cmake.org/cmake/help/latest/command/target_include_directories.html) call) to check for this library by tools like Clang-Tidy. This option is `OFF` by default.
 
+### `JSON_StrictNulHandling`
+
+Reject a `'\0'` (NUL) byte in the input instead of treating it as end of input, by defining the macro
+[`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md). This option is `OFF` by default.
+
 ### `JSON_Valgrind`
 
 Execute the test suite with [Valgrind](https://valgrind.org). This option is `OFF` by default. Depends on `JSON_BuildTests`.

docs/mkdocs/docs/integration/migration_guide.md

@@ -176,6 +176,12 @@ You can prepare existing code by already defining
 conversions with calls to [`get`](../api/basic_json/get.md), [`get_to`](../api/basic_json/get_to.md),
 [`get_ref`](../api/basic_json/get_ref.md), or [`get_ptr`](../api/basic_json/get_ptr.md).
 
+!!! tip "Automatic migration"
+
+    The community-maintained clang-tidy check `modernize-nlohmann-json-explicit-conversions` rewrites most implicit
+    conversions into calls to [`get`](../api/basic_json/get.md). It is not part of clang-tidy itself; see
+    [discussion #4610](https://github.com/nlohmann/json/discussions/4610) for how to build and use it.
+
 === "Deprecated"
 
       ```cpp

docs/mkdocs/mkdocs.yml

@@ -98,6 +98,7 @@ nav:
       - Types:
           - features/types/index.md
           - features/types/number_handling.md
+          - features/types/template_parameters.md
   - Integration:
       - integration/index.md
       - integration/migration_guide.md
@@ -291,8 +292,10 @@ nav:
           - 'JSON_HAS_THREE_WAY_COMPARISON': api/macros/json_has_three_way_comparison.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
           - 'JSON_SKIP_LIBRARY_VERSION_CHECK': api/macros/json_skip_library_version_check.md
           - 'JSON_SKIP_UNSUPPORTED_COMPILER_CHECK': api/macros/json_skip_unsupported_compiler_check.md
+          - 'JSON_STRICT_NUL_HANDLING': api/macros/json_strict_nul_handling.md
           - 'JSON_USE_GLOBAL_UDLS': api/macros/json_use_global_udls.md
           - 'JSON_USE_IMPLICIT_CONVERSIONS': api/macros/json_use_implicit_conversions.md
           - 'JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON': api/macros/json_use_legacy_discarded_value_comparison.md

docs/mkdocs/requirements.txt

@@ -1,7 +1,7 @@
 wheel==0.48.0
 
 mkdocs==1.6.1                                       # documentation framework
-mkdocs-git-revision-date-localized-plugin==1.5.4    # plugin "git-revision-date-localized"
+mkdocs-git-revision-date-localized-plugin==1.6.0    # plugin "git-revision-date-localized"
 mkdocs-material==9.7.7                             # theme for mkdocs
 mkdocs-material-extensions==1.3.1                   # extensions
 mkdocs-minify-plugin==0.8.0                         # plugin "minify"

include/nlohmann/detail/abi_macros.hpp

@@ -34,6 +34,10 @@
     #define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
 #endif
 
+#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
+    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -52,20 +56,27 @@
     #define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON
 #endif
 
+#if JSON_BRACE_INIT_COPY_SEMANTICS
+    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS _bics
+#else
+    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
+#endif
+
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
     #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif
 
 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c) json_abi ## a ## b ## c
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
-            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS)
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

include/nlohmann/detail/conversions/to_json.hpp

@@ -471,6 +471,30 @@ inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<
     j = { std::get<Idx>(t)... };
 }
 
+#if JSON_BRACE_INIT_COPY_SEMANTICS
+// JSON_BRACE_INIT_COPY_SEMANTICS makes a one-element braced list copy its
+// element instead of wrapping it, which would serialize std::tuple<int>{5} as 5
+// rather than [5]. Build what the default deduction builds instead: an object
+// if the element is a [string, value] pair, a one-element array otherwise.
+template<typename BasicJsonType, typename Tuple>
+inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<0> /*unused*/)
+{
+    BasicJsonType element(std::get<0>(t));
+    // same test as the initializer-list constructor, including the cast that
+    // keeps a string type constructible from 0 from selecting operator[](key)
+    const bool is_member = element.is_array() && element.size() == 2
+                           && element[static_cast<typename BasicJsonType::size_type>(0)].is_string();
+    if (is_member)
+    {
+        j = BasicJsonType::object({std::move(element)});
+    }
+    else
+    {
+        j = BasicJsonType::array({std::move(element)});
+    }
+}
+#endif
+
 template<typename BasicJsonType, typename Tuple>
 inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& /*unused*/, index_sequence<> /*unused*/)
 {

include/nlohmann/detail/exceptions.hpp

@@ -101,7 +101,10 @@ class exception : public std::exception
                     {
                         if (&element.second == current)
                         {
-                            tokens.emplace_back(element.first.c_str());
+                            // data() is null-terminated, so a key containing
+                            // a null byte is cut short here rather than
+                            // truncating the whole message at what()
+                            tokens.emplace_back(element.first.data());
                             break;
                         }
                     }

include/nlohmann/detail/hash.hpp

@@ -11,8 +11,10 @@
 #include <cstdint> // uint8_t
 #include <cstddef> // size_t
 #include <functional> // hash
+#include <vector> // vector
 
 #include <nlohmann/detail/abi_macros.hpp>
+#include <nlohmann/detail/recursion_depth_limit.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -26,6 +28,9 @@ inline std::size_t combine(std::size_t seed, std::size_t h) noexcept
     return seed;
 }
 
+template<typename BasicJsonType>
+std::size_t hash_iteratively(const BasicJsonType& j);
+
 /*!
 @brief hash a JSON value
 
@@ -33,12 +38,21 @@ The hash function tries to rely on std::hash where possible. Furthermore, the
 type of the JSON value is taken into account to have different hash values for
 null, 0, 0U, and false, etc.
 
+Hashing an array or an object hashes its elements, which used to call this
+function again once per nesting level, so a value nested deeply enough
+exhausted the call stack and terminated the process. The descent is bounded
+here: once @ref recursion_depth_limit levels have been entered, @ref
+hash_iteratively hashes what is left without the call stack. A value nested
+less deeply than that - all but a vanishing minority - is hashed exactly as
+before, without allocating.
+
 @tparam BasicJsonType basic_json specialization
 @param j JSON value to hash
+@param depth nesting level of @a j, counted from the value passed by the caller
 @return hash value of j
 */
 template<typename BasicJsonType>
-std::size_t hash(const BasicJsonType& j)
+std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)
 {
     using string_t = typename BasicJsonType::string_t;
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -56,22 +70,32 @@ std::size_t hash(const BasicJsonType& j)
 
         case BasicJsonType::value_t::object:
         {
+            if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
+            {
+                return hash_iteratively(j);
+            }
+
             auto seed = combine(type, j.size());
             for (const auto& element : j.items())
             {
                 const auto h = std::hash<string_t> {}(element.key());
                 seed = combine(seed, h);
-                seed = combine(seed, hash(element.value()));
+                seed = combine(seed, hash(element.value(), depth + 1));
             }
             return seed;
         }
 
         case BasicJsonType::value_t::array:
         {
+            if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
+            {
+                return hash_iteratively(j);
+            }
+
             auto seed = combine(type, j.size());
             for (const auto& element : j)
             {
-                seed = combine(seed, hash(element));
+                seed = combine(seed, hash(element, depth + 1));
             }
             return seed;
         }
@@ -114,7 +138,9 @@ std::size_t hash(const BasicJsonType& j)
             seed = combine(seed, static_cast<std::size_t>(j.get_binary().subtype()));
             for (const auto byte : j.get_binary())
             {
-                seed = combine(seed, std::hash<std::uint8_t> {}(byte));
+                // the cast is needed for binary types whose value type is not
+                // an integer (e.g., std::byte)
+                seed = combine(seed, std::hash<std::uint8_t> {}(static_cast<std::uint8_t>(byte)));
             }
             return seed;
         }
@@ -125,5 +151,77 @@ std::size_t hash(const BasicJsonType& j)
     }
 }
 
+/// an array or object whose elements @ref hash_iteratively is hashing
+template<typename BasicJsonType>
+struct hash_frame
+{
+    hash_frame(const BasicJsonType* value_, std::size_t seed_) noexcept
+        : value(value_), position(value_->cbegin()), seed(seed_)
+    {}
+
+    const BasicJsonType* value;
+    typename BasicJsonType::const_iterator position;
+    std::size_t seed;
+};
+
+/*!
+@brief hash the array or object @a j without the call stack
+
+Computes the same value as @ref hash, keeping the arrays and objects it has
+entered on an explicit stack instead of descending into them. Only reached for
+values nested deeper than @ref recursion_depth_limit.
+
+@tparam BasicJsonType basic_json specialization
+@param j array or object to hash
+@return hash value of j
+*/
+template<typename BasicJsonType>
+std::size_t hash_iteratively(const BasicJsonType& j)
+{
+    using string_t = typename BasicJsonType::string_t;
+
+    std::vector<hash_frame<BasicJsonType>> stack;
+    stack.emplace_back(&j, combine(static_cast<std::size_t>(j.type()), j.size()));
+
+    while (true)
+    {
+        // a copy, as entering an element below can reallocate the stack; the
+        // frame itself is only changed through stack.back()
+        const hash_frame<BasicJsonType> frame = stack.back();
+
+        if (frame.position == frame.value->cend())
+        {
+            // all elements are hashed: fold this value's hash into its parent's
+            // seed, exactly where the recursive version returns it
+            const std::size_t h = frame.seed;
+            stack.pop_back();
+            if (stack.empty())
+            {
+                return h;
+            }
+            stack.back().seed = combine(stack.back().seed, h);
+            continue;
+        }
+
+        if (frame.value->is_object())
+        {
+            stack.back().seed = combine(stack.back().seed, std::hash<string_t> {}(frame.position.key()));
+        }
+
+        // advance before entering the element, which pushes onto the stack
+        const BasicJsonType& element = *frame.position;
+        ++stack.back().position;
+
+        if (element.is_structured())
+        {
+            stack.emplace_back(&element, combine(static_cast<std::size_t>(element.type()), element.size()));
+        }
+        else
+        {
+            stack.back().seed = combine(stack.back().seed, hash(element));
+        }
+    }
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/input/binary_reader.hpp

@@ -32,7 +32,6 @@
 #include <nlohmann/detail/meta/is_sax.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/string_concat.hpp>
-#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -433,21 +432,7 @@ class binary_reader
                                     exception_message(input_format_t::bson, concat("string length must be at least 1, is ", std::to_string(len)), "string"), nullptr));
         }
 
-        if (JSON_HEDLEY_UNLIKELY(!get_string(input_format_t::bson, len - static_cast<NumberType>(1), result)))
-        {
-            return false;
-        }
-
-        if (JSON_HEDLEY_UNLIKELY(get() != 0x00))
-        {
-            auto last_token = get_token_string();
-            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
-                                    exception_message(input_format_t::bson,
-                                            "BSON string is not null-terminated",
-                                            "string"), nullptr));
-        }
-
-        return true;
+        return get_string(input_format_t::bson, len - static_cast<NumberType>(1), result) && get() != char_traits<char_type>::eof();
     }
 
     /*!
@@ -565,6 +550,8 @@ class binary_reader
         }
     }
 
+
+
     //////////
     // CBOR //
     //////////
@@ -3159,7 +3146,10 @@ class binary_reader
                                number_string,
                                out_of_range::create(406, concat("number overflow parsing '", number_string, '\''), nullptr));
                 }
-                return sax->number_float(parsed_float, std::move(number_string));
+                // number_string is a std::string, while the SAX interface takes a
+                // string_t; convert explicitly, as the two are only implicitly
+                // convertible for some string types
+                return sax->number_float(parsed_float, string_t(number_string.data(), number_string.size()));
             }
             case token_type::uninitialized:
             case token_type::literal_true:
@@ -3314,28 +3304,7 @@ class binary_reader
                     const NumberType len,
                     string_t& result)
     {
-        // get_bytes() appends to result, and CBOR indefinite-length strings
-        // collect all their chunks in the same result; validating only the
-        // newly read bytes keeps the check linear in the input size
-        const std::size_t old_size = result.size();
-        if (JSON_HEDLEY_UNLIKELY(!get_bytes(format, len, "string", result)))
-        {
-            return false;
-        }
-
-        // RFC 8949 (CBOR) §3.1 and the MessagePack/BSON/UBJSON specifications
-        // all require text strings to be valid UTF-8; reject anything else
-        // right here so malformed input is caught at decode time instead of
-        // only surfacing later as a type_error.316 when the value is dumped
-        // (which would defeat allow_exceptions=false / strict discarding).
-        if (JSON_HEDLEY_UNLIKELY(!is_valid_utf8(result, old_size)))
-        {
-            return sax->parse_error(chars_read, get_token_string(),
-                                    parse_error::create(113, chars_read,
-                                            exception_message(format, "invalid string: ill-formed UTF-8 byte", "string"), nullptr));
-        }
-
-        return true;
+        return get_bytes(format, len, "string", result);
     }
 
     /*!

include/nlohmann/detail/input/input_adapters.hpp

@@ -762,6 +762,21 @@ contiguous_bytes_input_adapter input_adapter(CharT b)
 template<typename T, std::size_t N>
 auto input_adapter(T (&array)[N]) -> decltype(input_adapter(array, array + N)) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
 {
+#if JSON_STRICT_NUL_HANDLING
+    // A `char` array from string-literal initialization (e.g. json::parse("123"))
+    // carries a trailing '\0' contributed by the compiler, not by the source
+    // text; drop exactly that one byte so it is not mistaken for real trailing
+    // data. Every other element type (unsigned char, std::uint8_t, ...) keeps
+    // the full extent unconditionally, since a trailing zero byte there is
+    // genuine data (e.g. CBOR/MessagePack). This intentionally does not
+    // strlen()-scan the array (as the pointer overload above does for a
+    // null-delimited string): for a `char` array that is not NUL-terminated
+    // within its bounds, that would read past the end of the array.
+    if (std::is_same<typename std::remove_cv<T>::type, char>::value && N > 0 && array[N - 1] == 0)
+    {
+        return input_adapter(array, array + N - 1);
+    }
+#endif
     return input_adapter(array, array + N);
 }
 

include/nlohmann/detail/input/json_sax.hpp

@@ -8,11 +8,11 @@
 
 #pragma once
 
-#include <algorithm> // min
+#include <algorithm> // find_if, min
 #include <cstddef>
 #include <string> // string
 #include <type_traits> // enable_if_t
-#include <utility> // move
+#include <utility> // move, pair
 #include <vector> // vector
 
 #include <nlohmann/detail/exceptions.hpp>
@@ -278,7 +278,7 @@ class json_sax_dom_parser
 
         if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
         {
-            JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
+            return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
         }
 
         return true;
@@ -327,7 +327,7 @@ class json_sax_dom_parser
 
         if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
         {
-            JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
+            return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
         }
 
         if (len != detail::unknown_size())
@@ -611,7 +611,7 @@ class json_sax_dom_callback_parser
             // check object limit
             if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
             {
-                JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
+                return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
             }
         }
         return true;
@@ -631,7 +631,17 @@ class json_sax_dom_callback_parser
         // add discarded value at the given key and store the reference for later
         if (keep && ref_stack.back())
         {
-            object_element = &(ref_stack.back()->m_data.m_value.object->operator[](val) = discarded);
+            auto& obj = *ref_stack.back()->m_data.m_value.object;
+            const auto it = obj.find(val);
+            if (it != obj.end())
+            {
+                // this is a duplicate key (legal in JSON); remember its
+                // current value so it can be restored later if the new
+                // value is rejected by the callback, instead of being
+                // erased together with the discarded placeholder
+                duplicate_key_stash.emplace_back(&(it->second), it->second);
+            }
+            object_element = &(obj[val] = discarded);
         }
 
         return true;
@@ -643,13 +653,18 @@ class json_sax_dom_callback_parser
         {
             if (!callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::object_end, *ref_stack.back()))
             {
-                // discard object
-                *ref_stack.back() = discarded;
+                // discard object, unless this slot holds a duplicate key's
+                // previous value pending restoration, in which case that
+                // value is restored instead of being discarded
+                if (!resolve_duplicate_key_stash(ref_stack.back(), true))
+                {
+                    *ref_stack.back() = discarded;
 
 #if JSON_DIAGNOSTIC_POSITIONS
-                // Set start/end positions for discarded object.
-                handle_diagnostic_positions_for_json_value(*ref_stack.back());
+                    // Set start/end positions for discarded object.
+                    handle_diagnostic_positions_for_json_value(*ref_stack.back());
 #endif
+                }
             }
             else
             {
@@ -663,6 +678,10 @@ class json_sax_dom_callback_parser
 #endif
 
                 ref_stack.back()->set_parents();
+                // this object is finally, definitively kept; drop any
+                // pending duplicate-key stash entry for its slot since it
+                // can no longer be restored
+                resolve_duplicate_key_stash(ref_stack.back(), false);
             }
         }
 
@@ -711,7 +730,7 @@ class json_sax_dom_callback_parser
             // check array limit
             if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
             {
-                JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
+                return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
             }
 
             if (len != detail::unknown_size())
@@ -743,16 +762,25 @@ class json_sax_dom_callback_parser
 #endif
 
                 ref_stack.back()->set_parents();
+                // this array is finally, definitively kept; drop any
+                // pending duplicate-key stash entry for its slot since it
+                // can no longer be restored
+                resolve_duplicate_key_stash(ref_stack.back(), false);
             }
             else
             {
-                // discard array
-                *ref_stack.back() = discarded;
+                // discard array, unless this slot holds a duplicate key's
+                // previous value pending restoration, in which case that
+                // value is restored instead of being discarded
+                if (!resolve_duplicate_key_stash(ref_stack.back(), true))
+                {
+                    *ref_stack.back() = discarded;
 
 #if JSON_DIAGNOSTIC_POSITIONS
-                // Set start/end positions for discarded array.
-                handle_diagnostic_positions_for_json_value(*ref_stack.back());
+                    // Set start/end positions for discarded array.
+                    handle_diagnostic_positions_for_json_value(*ref_stack.back());
 #endif
+                }
             }
         }
 
@@ -869,6 +897,35 @@ class json_sax_dom_callback_parser
     }
 #endif
 
+    /// if there is a pending duplicate-key stash entry for this exact slot,
+    /// remove it from the stash; if restore_value is true, the stashed
+    /// previous value is moved back into the slot first (use this when the
+    /// new value at that slot was rejected); otherwise the stash entry is
+    /// simply dropped (use this when the new value was accepted, so it
+    /// correctly supersedes the old one and no restore should ever happen
+    /// for this slot again)
+    /// @return whether a matching stash entry was found (and processed)
+    bool resolve_duplicate_key_stash(BasicJsonType* slot, bool restore_value)
+    {
+        const auto it = std::find_if(duplicate_key_stash.begin(), duplicate_key_stash.end(),
+                                     [slot](const std::pair<BasicJsonType*, BasicJsonType>& entry)
+        {
+            return entry.first == slot;
+        });
+
+        if (it == duplicate_key_stash.end())
+        {
+            return false;
+        }
+
+        if (restore_value)
+        {
+            *slot = std::move(it->second);
+        }
+        duplicate_key_stash.erase(it);
+        return true;
+    }
+
     /*!
     @brief the key the value now being handled will be stored under
 
@@ -887,7 +944,9 @@ class json_sax_dom_callback_parser
     }
 
     /*!
-    @brief remove the discarded value the callback rejected from its parent
+    @brief remove the discarded value the callback rejected from its parent,
+    unless it is a duplicate key's slot with a stashed previous value, in
+    which case that previous value is restored instead
 
     A rejected value can only ever be the one most recently added to @a parent:
     the last element of an array, or the placeholder key() stored under @a key
@@ -902,7 +961,7 @@ class json_sax_dom_callback_parser
     @param[in,out] parent  the container to remove the rejected value from
     @param[in] key  the key the value was stored under; unused for arrays
     */
-    static void remove_discarded_value(BasicJsonType& parent, const string_t& key)
+    void remove_discarded_value(BasicJsonType& parent, const string_t& key)
     {
         if (parent.is_array())
         {
@@ -918,7 +977,12 @@ class json_sax_dom_callback_parser
             const auto it = object.find(key);
             if (it != object.end() && it->second.is_discarded())
             {
-                object.erase(it);
+                // a duplicate key's slot has a stashed previous value that
+                // must be restored instead of being erased
+                if (!resolve_duplicate_key_stash(&it->second, true))
+                {
+                    object.erase(it);
+                }
             }
         }
     }
@@ -1020,6 +1084,16 @@ class json_sax_dom_callback_parser
 
         JSON_ASSERT(object_element);
         *object_element = std::move(value);
+        if (!skip_callback)
+        {
+            // this scalar value finally, definitively replaces whatever was
+            // at this slot; drop any pending duplicate-key stash entry for
+            // it since it can no longer be restored (a container value at
+            // this slot is resolved later, in end_object()/end_array(),
+            // since skip_callback is true for the placeholder handling that
+            // happens here for those)
+            resolve_duplicate_key_stash(object_element, false);
+        }
         return {true, object_element};
     }
 
@@ -1039,6 +1113,12 @@ class json_sax_dom_callback_parser
     std::vector<string_t> container_key_stack {}; // NOLINT(readability-redundant-member-init)
     /// helper to hold the reference for the next object element
     BasicJsonType* object_element = nullptr;
+    /// stash of (slot pointer, previous value) for object members that
+    /// already existed when key() was called again for the same key
+    /// (duplicate keys); used to restore the previous value if the new
+    /// value is later rejected by the callback, instead of erasing the
+    /// member entirely
+    std::vector<std::pair<BasicJsonType*, BasicJsonType>> duplicate_key_stash {};
     /// whether a syntax error occurred
     bool errored = false;
     /// callback function

include/nlohmann/detail/input/lexer.hpp

@@ -952,7 +952,9 @@ class lexer : public lexer_base<BasicJsonType>
                         case '\n':
                         case '\r':
                         case char_traits<char_type>::eof():
+#if !JSON_STRICT_NUL_HANDLING
                         case '\0':
+#endif
                             return true;
 
                         default:
@@ -970,8 +972,10 @@ class lexer : public lexer_base<BasicJsonType>
                 {
                     switch (get())
                     {
-                        case char_traits<char_type>::eof():
+#if !JSON_STRICT_NUL_HANDLING
                         case '\0':
+#endif
+                        case char_traits<char_type>::eof():
                         {
                             error_message = "invalid comment; missing closing '*/'";
                             return false;
@@ -2153,9 +2157,12 @@ scan_number_done:
             case '9':
                 return scan_number_dispatch(std::integral_constant<bool, bulk_scan> {});
 
-            // end of input (the null byte is needed when parsing from
-            // string literals)
+#if !JSON_STRICT_NUL_HANDLING
             case '\0':
+#endif
+            // end of input; by default, a null byte is also treated as end of
+            // input for backwards compatibility (see JSON_STRICT_NUL_HANDLING
+            // to opt into rejecting a null byte in the input instead)
             case char_traits<char_type>::eof():
                 return token_type::end_of_input;
 

include/nlohmann/detail/iterators/iter_impl.hpp

@@ -88,8 +88,13 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
 
     iter_impl() = default;
     ~iter_impl() = default;
-    iter_impl(iter_impl&&) noexcept = default;
-    iter_impl& operator=(iter_impl&&) noexcept = default;
+    // the exception specification is left to be computed rather than declared:
+    // an array or object type whose iterator is not nothrow move constructible
+    // (std::deque's is not before libstdc++ 11) would make a declared noexcept
+    // differ from the implicit one, which deletes the function -- and is an
+    // error outright with older compilers
+    iter_impl(iter_impl&&) = default; // NOLINT(hicpp-noexcept-move,performance-noexcept-move-constructor,cppcoreguidelines-noexcept-move-operations)
+    iter_impl& operator=(iter_impl&&) = default; // NOLINT(hicpp-noexcept-move,performance-noexcept-move-constructor,cppcoreguidelines-noexcept-move-operations)
 
     /*!
     @brief constructor for a given JSON instance

include/nlohmann/detail/json_pointer.hpp

@@ -17,6 +17,7 @@
 #endif  // JSON_NO_IO
 #include <limits> // max
 #include <numeric> // accumulate
+#include <set> // set
 #include <string> // string
 #include <utility> // move
 #include <vector> // vector
@@ -71,7 +72,7 @@ class json_pointer
                                string_t{},
                                [](const string_t& a, const string_t& b)
         {
-            return detail::concat(a, '/', detail::escape(b));
+            return detail::concat<string_t>(a, '/', detail::escape(b));
         });
     }
 
@@ -265,7 +266,7 @@ class json_pointer
             JSON_THROW(detail::parse_error::create(109, 0, detail::concat("array index '", s, "' is not a number"), nullptr));
         }
 
-        const char* p = s.c_str();
+        const char* p = s.data();
         char* p_end = nullptr; // NOLINT(misc-const-correctness)
         errno = 0; // strtoull doesn't reset errno
         const unsigned long long res = std::strtoull(p, &p_end, 10); // NOLINT(runtime/int)
@@ -300,19 +301,35 @@ class json_pointer
     }
 
   private:
+    /*!
+    @brief the reference token sequences that denote arrays
+
+    @ref unflatten collects the pointer prefixes that have a reference token 0
+    among their children; @ref get_and_create creates arrays exactly below
+    those prefixes and objects everywhere else. Deciding this up front keeps
+    the result independent of the order in which the flattened object is
+    iterated, which is unspecified for some object types.
+    */
+    using array_parents_t = std::set<std::vector<string_t>>;
+
     /*!
     @brief create and return a reference to the pointed to value
 
     @complexity Linear in the number of reference tokens.
 
+    @throw parse_error.106 if an array index begins with '0'
     @throw parse_error.109 if array index is not a number
     @throw type_error.313 if value cannot be unflattened
     */
     template<typename BasicJsonType>
-    BasicJsonType& get_and_create(BasicJsonType& j) const
+    BasicJsonType& get_and_create(BasicJsonType& j, const array_parents_t& array_parents) const
     {
         auto* result = &j;
 
+        // the reference tokens that have been consumed so far; used to look up
+        // whether the value to be created below is an array or an object
+        std::vector<string_t> prefix;
+
         // in case no reference tokens exist, return a reference to the JSON value
         // j which will be overwritten by a primitive value
         for (const auto& reference_token : reference_tokens)
@@ -321,10 +338,11 @@ class json_pointer
             {
                 case detail::value_t::null:
                 {
-                    if (reference_token == "0")
+                    if (array_parents.find(prefix) != array_parents.end())
                     {
-                        // start a new array if the reference token is 0
-                        result = &result->operator[](0);
+                        // some reference token below this position is 0, so the
+                        // value is an array
+                        result = &result->operator[](array_index<BasicJsonType>(reference_token));
                     }
                     else
                     {
@@ -364,6 +382,8 @@ class json_pointer
                 default:
                     JSON_THROW(detail::type_error::create(313, "invalid value to unflatten", &j));
             }
+
+            prefix.push_back(reference_token);
         }
 
         return *result;
@@ -837,7 +857,8 @@ class json_pointer
         {
             // use the text between the beginning of the reference token
             // (start) and the last slash (slash).
-            auto reference_token = reference_string.substr(start, slash - start);
+            const auto count = (slash == string_t::npos ? reference_string.size() : slash) - start;
+            auto reference_token = string_t(reference_string.data() + start, count);
 
             // check reference tokens are properly escaped
             for (std::size_t pos = reference_token.find_first_of('~');
@@ -953,6 +974,24 @@ class json_pointer
 
         BasicJsonType result;
 
+        // collect the pointer prefixes that have a reference token 0 among
+        // their children; the values below them are arrays, all others are
+        // objects (see array_parents_t)
+        array_parents_t array_parents;
+        for (const auto& element : *value.m_data.m_value.object)
+        {
+            json_pointer ptr(element.first);
+            std::vector<string_t> prefix;
+            for (auto& reference_token : ptr.reference_tokens)
+            {
+                if (reference_token == "0")
+                {
+                    array_parents.insert(prefix);
+                }
+                prefix.push_back(std::move(reference_token));
+            }
+        }
+
         // iterate the JSON object values
         for (const auto& element : *value.m_data.m_value.object)
         {
@@ -965,7 +1004,7 @@ class json_pointer
             // that if the JSON pointer is "" (i.e., points to the whole value),
             // function get_and_create returns a reference to the result itself.
             // An assignment will then create a primitive value.
-            json_pointer(element.first).get_and_create(result) = element.second;
+            json_pointer(element.first).get_and_create(result, array_parents) = element.second;
         }
 
         return result;

include/nlohmann/detail/macro_scope.hpp

@@ -186,6 +186,15 @@
     #define JSON_NO_UNIQUE_ADDRESS
 #endif
 
+// Clang targeting MinGW does not survive the thread_local storage the copy
+// constructor uses to bound its descent: every test that copies a value
+// segfaults with clang 11.0.1 and clang 18.1.8, while the same tests pass with
+// GCC targeting MinGW and with every other toolchain the library is tested on.
+// Copying works the same way without the counter, only more slowly.
+#if !defined(JSON_NO_THREAD_LOCAL) && defined(__clang__) && defined(__MINGW32__)
+    #define JSON_NO_THREAD_LOCAL 1
+#endif
+
 // disable documentation warnings on clang
 #if defined(__clang__)
     #pragma clang diagnostic push
@@ -804,6 +813,6 @@ void templated_json_throw(ExceptionType exception)
     #define JSON_USE_GLOBAL_UDLS 1
 #endif
 
-#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
-    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
+#ifndef JSON_STRICT_NUL_HANDLING
+    #define JSON_STRICT_NUL_HANDLING 0
 #endif

include/nlohmann/detail/macro_unscope.hpp

@@ -26,7 +26,7 @@
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_USE_GLOBAL_UDLS
-#undef JSON_BRACE_INIT_COPY_SEMANTICS
+#undef JSON_STRICT_NUL_HANDLING
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH
@@ -44,6 +44,7 @@
     #undef JSON_HAS_STD_FORMAT
     #undef JSON_HAS_STATIC_RTTI
     #undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+    #undef JSON_BRACE_INIT_COPY_SEMANTICS
 #endif
 
 #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

include/nlohmann/detail/meta/type_traits.hpp

@@ -172,17 +172,18 @@ struct has_to_json < BasicJsonType, T, enable_if_t < !is_basic_json<T>::value >>
 template<typename T>
 using detect_key_compare = typename T::key_compare;
 
-template<typename T>
-struct has_key_compare : std::integral_constant<bool, is_detected<detect_key_compare, T>::value> {};
-
-// obtains the actual object key comparator
+// obtains the actual object key comparator: object_t::key_compare if the
+// object type defines it, and default_object_comparator_t otherwise
+//
+// note detected_or_t is used rather than std::conditional, because the latter
+// names both of its type arguments eagerly; object_t::key_compare would then
+// be a hard error for an object type that does not define it
 template<typename BasicJsonType>
 struct actual_object_comparator
 {
     using object_t = typename BasicJsonType::object_t;
     using object_comparator_t = typename BasicJsonType::default_object_comparator_t;
-    using type = typename std::conditional < has_key_compare<object_t>::value,
-          typename object_t::key_compare, object_comparator_t>::type;
+    using type = detected_or_t<object_comparator_t, detect_key_compare, object_t>;
 };
 
 template<typename BasicJsonType>
@@ -778,6 +779,22 @@ using has_erase_with_key_type = typename std::conditional <
                                 std::true_type,
                                 std::false_type >::type;
 
+template<typename ObjectType, typename IteratorType>
+using detect_erase_with_iterator = decltype(std::declval<ObjectType&>().erase(std::declval<IteratorType>()));
+
+// type trait to check if erase(iterator) returns void instead of the following
+// iterator, as the object types that do not compute a successor the caller may
+// not need do
+template<typename ObjectType, typename IteratorType>
+using erase_returns_void = is_detected_exact<void, detect_erase_with_iterator, ObjectType, IteratorType>;
+
+template<typename T>
+using detect_capacity = decltype(std::declval<const T&>().capacity());
+
+// type trait to check if a type has a capacity() member function
+template<typename T>
+struct has_capacity : std::integral_constant<bool, is_detected<detect_capacity, T>::value> {};
+
 // a naive helper to check if a type is an ordered_map (exploits the fact that
 // ordered_map inherits capacity() from std::vector)
 template <typename T>

include/nlohmann/detail/output/output_adapters.hpp

@@ -13,6 +13,7 @@
 #include <iterator> // back_inserter
 #include <memory> // shared_ptr, make_shared
 #include <string> // basic_string
+#include <utility> // move
 #include <vector> // vector
 
 #ifndef JSON_NO_IO
@@ -44,22 +45,32 @@ template<typename CharType> struct output_adapter_protocol
 template<typename CharType>
 using output_adapter_t = std::shared_ptr<output_adapter_protocol<CharType>>;
 
-/// output adapter for byte vectors
+/// @brief non-virtual output sink writing into a std::vector
+///
+/// This sink is not part of the virtual output_adapter_protocol hierarchy: it is
+/// passed to binary_writer by value as a template parameter, so
+/// write_character()/write_characters() are ordinary (inlinable) calls with no
+/// vtable lookup and no shared_ptr. It is used for the common
+/// `to_cbor`/`to_msgpack`/... into a std::vector. output_vector_adapter below
+/// wraps this same sink to provide the virtual interface.
 template<typename CharType, typename AllocatorType = std::allocator<CharType>>
-class output_vector_adapter : public output_adapter_protocol<CharType>
+class output_vector_sink
 {
   public:
-    explicit output_vector_adapter(std::vector<CharType, AllocatorType>& vec) noexcept
+    explicit output_vector_sink(std::vector<CharType, AllocatorType>& vec) noexcept
         : v(vec)
     {}
 
-    void write_character(CharType c) override
+    void write_character(CharType c)
     {
         v.push_back(c);
     }
 
-    JSON_HEDLEY_NON_NULL(2)
-    void write_characters(const CharType* s, std::size_t length) override
+    // no JSON_HEDLEY_NON_NULL here: binary_writer legitimately passes a null
+    // pointer with length 0 for empty strings/binary values. Appending an empty
+    // range is a no-op; the type-erased path tolerates this via the (unattributed)
+    // virtual base, and the concrete sink must do the same.
+    void write_characters(const CharType* s, std::size_t length)
     {
         v.insert(v.end(), s, s + length);
     }
@@ -68,6 +79,34 @@ class output_vector_adapter : public output_adapter_protocol<CharType>
     std::vector<CharType, AllocatorType>& v;
 };
 
+/// output adapter for byte vectors
+///
+/// The appending itself lives in output_vector_sink; this class only adds the
+/// virtual output_adapter_protocol interface on top of it, so both the
+/// type-erased and the templated path share one implementation.
+template<typename CharType, typename AllocatorType = std::allocator<CharType>>
+class output_vector_adapter : public output_adapter_protocol<CharType>
+{
+  public:
+    explicit output_vector_adapter(std::vector<CharType, AllocatorType>& vec) noexcept
+        : sink(vec)
+    {}
+
+    void write_character(CharType c) override
+    {
+        sink.write_character(c);
+    }
+
+    JSON_HEDLEY_NON_NULL(2)
+    void write_characters(const CharType* s, std::size_t length) override
+    {
+        sink.write_characters(s, length);
+    }
+
+  private:
+    output_vector_sink<CharType, AllocatorType> sink;
+};
+
 #ifndef JSON_NO_IO
 /// output adapter for output streams
 template<typename CharType>
@@ -118,6 +157,39 @@ class output_string_adapter : public output_adapter_protocol<CharType>
     StringType& str;
 };
 
+/// @brief output sink forwarding to a type-erased output adapter
+///
+/// Wraps the polymorphic output_adapter_t so the same binary_writer template can
+/// also target arbitrary adapters (output streams, strings, user-provided
+/// adapters) via the `output_adapter`-based overloads. Each write still goes
+/// through one virtual call, exactly as before; only the concrete sinks above
+/// avoid it.
+template<typename CharType>
+class output_adapter_sink
+{
+  public:
+    explicit output_adapter_sink(output_adapter_t<CharType> adapter)
+        : oa(std::move(adapter))
+    {
+        JSON_ASSERT(oa);
+    }
+
+    void write_character(CharType c)
+    {
+        oa->write_character(c);
+    }
+
+    // no JSON_HEDLEY_NON_NULL: forwards (null, 0) for empty payloads, exactly as
+    // the type-erased path already did before this sink existed
+    void write_characters(const CharType* s, std::size_t length)
+    {
+        oa->write_characters(s, length);
+    }
+
+  private:
+    output_adapter_t<CharType> oa;
+};
+
 template<typename CharType, typename StringType = std::basic_string<CharType>>
 class output_adapter
 {

include/nlohmann/detail/output/serializer.hpp

@@ -30,8 +30,8 @@
 #include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/output/binary_writer.hpp>
 #include <nlohmann/detail/output/output_adapters.hpp>
+#include <nlohmann/detail/recursion_depth_limit.hpp>
 #include <nlohmann/detail/string_concat.hpp>
-#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -58,6 +58,8 @@ class serializer
     using number_integer_t = typename BasicJsonType::number_integer_t;
     using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
     using binary_char_t = typename BasicJsonType::binary_t::value_type;
+    static constexpr std::uint8_t UTF8_ACCEPT = 0;
+    static constexpr std::uint8_t UTF8_REJECT = 1;
 
   public:
     /*!
@@ -132,7 +134,7 @@ class serializer
 
     Serializing a container descends into its elements, so a value nested deeply
     enough used to exhaust the call stack and terminate the process with no
-    exception to catch. The descent is bounded here: once @ref dump_depth_limit
+    exception to catch. The descent is bounded here: once @ref recursion_depth_limit
     levels have been entered, @ref dump_iteratively writes out what is left
     without the call stack. A value nested less deeply than that - all but a
     vanishing minority - is written by exactly the code that always wrote it.
@@ -147,7 +149,7 @@ class serializer
         {
             case value_t::object:
             {
-                if (JSON_HEDLEY_UNLIKELY(depth >= dump_depth_limit()))
+                if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
                 {
                     dump_iteratively(val, current_indent);
                     return;
@@ -222,7 +224,7 @@ class serializer
 
             case value_t::array:
             {
-                if (JSON_HEDLEY_UNLIKELY(depth >= dump_depth_limit()))
+                if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
                 {
                     dump_iteratively(val, current_indent);
                     return;
@@ -407,19 +409,12 @@ class serializer
     }
 
   private:
-    /// the number of levels @ref dump_internal descends into before it hands
-    /// over to @ref dump_iteratively
-    static constexpr std::size_t dump_depth_limit()
-    {
-        return 128;
-    }
-
     /*!
     @brief write out @a val and everything below it without the call stack
 
     Emits the same bytes as @ref dump_internal, keeping the containers it has
     entered on an explicit stack instead of descending into them. Only reached
-    for values nested deeper than @ref dump_depth_limit, which is why it is not
+    for values nested deeper than @ref recursion_depth_limit, which is why it is not
     written for speed: walking every value this way measured up to 20% slower on
     object-heavy documents than letting the compiler drive the descent.
     */
@@ -1060,7 +1055,7 @@ class serializer
             {
                 case error_handler_t::strict:
                 {
-                    JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", hex_bytes(static_cast<std::uint8_t>(s.back() | 0))), nullptr));
+                    JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", hex_bytes(static_cast<std::uint8_t>(s[s.size() - 1] | 0))), nullptr));
                 }
 
                 case error_handler_t::ignore:
@@ -1321,6 +1316,19 @@ class serializer
         pos += 6;
     }
 
+    /*!
+    @brief convert a single element of a binary value to its byte value
+
+    The elements of a binary value are dumped as the numbers 0..255, regardless
+    of the value type of the configured BinaryType: that type may be signed
+    (`char`), unsigned (`std::uint8_t`), or not an integer at all
+    (`std::byte`), none of which @ref dump_integer can handle uniformly.
+    */
+    static std::uint8_t to_byte_value(binary_char_t x) noexcept
+    {
+        return static_cast<std::uint8_t>(x);
+    }
+
     // templates to avoid warnings about useless casts
     template <typename NumberType, enable_if_t<std::is_signed<NumberType>::value, int> = 0>
     bool is_negative_number(NumberType x)
@@ -1342,8 +1350,10 @@ class serializer
     an arbitrary number, and the three digits it takes at most are written
     straight into the write buffer.
 
-    Any byte type that is not a plain unsigned byte is left to @ref dump_integer,
-    whose representation of it may differ.
+    Any byte type that is not a plain unsigned byte is converted to its
+    @ref to_byte_value "byte value" and left to @ref dump_integer, so a signed
+    or non-integral BinaryType::value_type (`char`, `std::byte`, ...) still
+    dumps as 0..255.
     */
     template<typename ByteType>
     void dump_byte(const ByteType value)
@@ -1356,7 +1366,7 @@ class serializer
     template<typename ByteType>
     void dump_byte(const ByteType value, std::false_type /*is_plain_byte*/)
     {
-        dump_integer(value);
+        dump_integer(to_byte_value(value));
     }
 
     template<typename ByteType>
@@ -1402,8 +1412,7 @@ class serializer
     template < typename NumberType, detail::enable_if_t <
                    std::is_integral<NumberType>::value ||
                    std::is_same<NumberType, number_unsigned_t>::value ||
-                   std::is_same<NumberType, number_integer_t>::value ||
-                   std::is_same<NumberType, binary_char_t>::value,
+                   std::is_same<NumberType, number_integer_t>::value,
                    int > = 0 >
     void dump_integer(NumberType x)
     {
@@ -1583,6 +1592,62 @@ class serializer
         }
     }
 
+    /*!
+    @brief check whether a string is UTF-8 encoded
+
+    The function checks each byte of a string whether it is UTF-8 encoded. The
+    result of the check is stored in the @a state parameter. The function must
+    be called initially with state 0 (accept). State 1 means the string must
+    be rejected, because the current byte is not allowed. If the string is
+    completely processed, but the state is non-zero, the string ended
+    prematurely; that is, the last byte indicated more bytes should have
+    followed.
+
+    @param[in,out] state  the state of the decoding
+    @param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
+    @param[in] byte       next byte to decode
+    @return               new state
+
+    @note The function has been edited: a std::array is used.
+
+    @copyright Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
+    @sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
+    */
+    static std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept
+    {
+        static const std::array<std::uint8_t, 400> utf8d =
+        {
+            {
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F
+                7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF
+                8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF
+                0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF
+                0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF
+                0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
+                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
+                1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
+                1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
+                1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8
+            }
+        };
+
+        JSON_ASSERT(static_cast<std::size_t>(byte) < utf8d.size());
+        const std::uint8_t type = utf8d[byte];
+
+        codep = (state != UTF8_ACCEPT)
+                ? (byte & 0x3fu) | (codep << 6u)
+                : (0xFFu >> type) & (byte);
+
+        const std::size_t index = 256u + (static_cast<size_t>(state) * 16u) + static_cast<size_t>(type);
+        JSON_ASSERT(index < utf8d.size());
+        state = utf8d[index];
+        return state;
+    }
+
     /*
      * Overload to make the compiler happy while it is instantiating
      * dump_integer for number_unsigned_t.

include/nlohmann/detail/recursion_depth_limit.hpp

@@ -0,0 +1,35 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <cstddef> // size_t
+
+#include <nlohmann/detail/abi_macros.hpp>
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+/*!
+@brief the number of nesting levels an operation recurses into
+
+Operations that walk a value (serializing, hashing, merging, ...) recurse once
+per nesting level, which is fastest, but a value nested deeply enough would
+exhaust the call stack. So they recurse only this many levels deep and finish
+whatever lies below with an explicit stack. All of them share this limit.
+
+@sa https://github.com/nlohmann/json/issues/5387
+*/
+constexpr std::size_t recursion_depth_limit() noexcept
+{
+    return 128;
+}
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/string_escape.hpp

@@ -8,50 +8,56 @@
 
 #pragma once
 
+#include <cstddef> // size_t
+
 #include <nlohmann/detail/abi_macros.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
 
-/*!
-@brief replace all occurrences of a substring by another string
-
-@param[in,out] s  the string to manipulate; changed so that all
-               occurrences of @a f are replaced with @a t
-@param[in]     f  the substring to replace with @a t
-@param[in]     t  the string to replace @a f
-
-@pre The search string @a f must not be empty. **This precondition is
-enforced with an assertion.**
-
-@since version 2.0.0
-*/
-template<typename StringType>
-inline void replace_substring(StringType& s, const StringType& f,
-                              const StringType& t)
-{
-    JSON_ASSERT(!f.empty());
-    for (auto pos = s.find(f);                // find the first occurrence of f
-            pos != StringType::npos;          // make sure f was found
-            s.replace(pos, f.size(), t),      // replace with t, and
-            pos = s.find(f, pos + t.size()))  // find the next occurrence of f
-    {}
-}
-
 /*!
  * @brief string escaping as described in RFC 6901 (Sect. 4)
  * @param[in] s string to escape
  * @return    escaped string
  *
  * Note the order of escaping "~" to "~0" and "/" to "~1" is important.
+ *
+ * The string is rebuilt in a single pass, appending whole runs between the
+ * characters that need escaping. Scanning with find_first_of() keeps the
+ * common case -- nothing to escape -- as fast as a single search, while
+ * repeated replace() calls would move the tail of the string once per
+ * escaped character.
  */
 template<typename StringType>
-inline StringType escape(StringType s)
+inline StringType escape(const StringType& s)
 {
-    replace_substring(s, StringType{"~"}, StringType{"~0"});
-    replace_substring(s, StringType{"/"}, StringType{"~1"});
-    return s;
+    auto next_special = [&s](std::size_t from)
+    {
+        const auto tilde = s.find_first_of('~', from);
+        const auto slash = s.find_first_of('/', from);
+        return tilde < slash ? tilde : slash; // npos is the largest value
+    };
+
+    auto pos = next_special(0);
+    if (pos == StringType::npos)
+    {
+        return s;
+    }
+
+    StringType result;
+    result.reserve(s.size() + 2);
+
+    std::size_t run = 0;
+    while (pos != StringType::npos)
+    {
+        result.append(s.data() + run, pos - run);
+        result.append(s[pos] == '~' ? "~0" : "~1", 2);
+        run = pos + 1;
+        pos = next_special(run);
+    }
+    result.append(s.data() + run, s.size() - run);
+    return result;
 }
 
 /*!
@@ -60,12 +66,43 @@ inline StringType escape(StringType s)
  * @return    unescaped string
  *
  * Note the order of escaping "~1" to "/" and "~0" to "~" is important.
+ *
+ * Rebuilt in a single pass, see @ref escape. A "~" that is followed by
+ * neither "0" nor "1" is passed through unchanged; @ref json_pointer rejects
+ * such input before it gets here.
  */
 template<typename StringType>
 inline void unescape(StringType& s)
 {
-    replace_substring(s, StringType{"~1"}, StringType{"/"});
-    replace_substring(s, StringType{"~0"}, StringType{"~"});
+    auto pos = s.find_first_of('~', 0);
+    if (pos == StringType::npos)
+    {
+        return;
+    }
+
+    StringType result;
+    result.reserve(s.size());
+
+    std::size_t run = 0;
+    while (pos != StringType::npos)
+    {
+        result.append(s.data() + run, pos - run);
+
+        const auto next = pos + 1;
+        if (next < s.size() && (s[next] == '0' || s[next] == '1'))
+        {
+            result.append(s[next] == '0' ? "~" : "/", 1);
+            run = pos + 2;
+        }
+        else
+        {
+            result.append("~", 1);
+            run = pos + 1;
+        }
+        pos = s.find_first_of('~', run);
+    }
+    result.append(s.data() + run, s.size() - run);
+    s = result;
 }
 
 }  // namespace detail

include/nlohmann/detail/string_utils.hpp

@@ -8,13 +8,10 @@
 
 #pragma once
 
-#include <array> // array
 #include <cstddef> // size_t
-#include <cstdint> // uint8_t, uint32_t
 #include <string> // string, to_string
 
 #include <nlohmann/detail/abi_macros.hpp>
-#include <nlohmann/detail/macro_scope.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -36,102 +33,5 @@ StringType to_string(std::size_t value)
     return result;
 }
 
-///////////////////
-// UTF-8 decoding //
-///////////////////
-
-// UTF-8 decoder states used by decode() below
-static constexpr std::uint8_t UTF8_ACCEPT = 0;
-static constexpr std::uint8_t UTF8_REJECT = 1;
-
-/*!
-@brief process a byte of a UTF-8 sequence
-
-This is a single-byte step of a "shift-based" UTF-8 decoder originally
-written by Björn Hoehrmann. See
-http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
-
-This decoder is the single source of truth for UTF-8 validation in this
-library: it is used both by the serializer (to escape and, in strict mode,
-reject ill-formed UTF-8 when dumping a string) and by the binary readers
-(to reject ill-formed UTF-8 in CBOR/MessagePack/BSON/UBJSON text strings at
-decode time; see @ref is_valid_utf8 below).
-
-@param[in,out] state  the current decoder state
-@param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
-@param[in] byte       next byte to decode
-@return               new state
-
-@note Original source: http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
-@sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
-*/
-inline std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept
-{
-    static const std::array<std::uint8_t, 400> utf8d =
-    {
-        {
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F
-            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F
-            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF
-            8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF
-            0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF
-            0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF
-            0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
-            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
-            1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
-            1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
-            1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8
-        }
-    };
-
-    JSON_ASSERT(static_cast<std::size_t>(byte) < utf8d.size());
-    const std::uint8_t type = utf8d[byte];
-
-    codep = (state != UTF8_ACCEPT)
-            ? (byte & 0x3fu) | (codep << 6u)
-            : (0xFFu >> type) & (byte);
-
-    const std::size_t index = 256u + (static_cast<std::size_t>(state) * 16u) + static_cast<std::size_t>(type);
-    JSON_ASSERT(index < utf8d.size());
-    state = utf8d[index];
-    return state;
-}
-
-/*!
-@brief check whether a string consists solely of valid UTF-8
-
-Used by the CBOR/MessagePack/BSON/UBJSON binary readers to reject text
-strings that are not valid UTF-8 at decode time (RFC 8949 §3.1 and the
-MessagePack/BSON specifications all require text strings to be UTF-8), so
-that malformed input is caught immediately instead of only surfacing later
-as a type_error.316 when the resulting value is dumped.
-
-@param[in] s      the string to check
-@param[in] first  index of the first byte to check; the bytes before it are
-                  assumed to have been validated already and to end on a
-                  code point boundary
-@return whether @a s (from index @a first on) is valid UTF-8
-*/
-template<typename StringType>
-inline bool is_valid_utf8(const StringType& s, const std::size_t first = 0) noexcept
-{
-    std::uint8_t state = UTF8_ACCEPT;
-    std::uint32_t codepoint = 0;
-
-    for (std::size_t i = first; i < s.size(); ++i)
-    {
-        decode(state, codepoint, static_cast<std::uint8_t>(s[i]));
-        if (state == UTF8_REJECT)
-        {
-            return false;
-        }
-    }
-
-    return state == UTF8_ACCEPT;
-}
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

nlohmann_json.natvis

@@ -215,6 +215,126 @@
         </Expand>
     </Type>
 
+    <!-- Namespace nlohmann::json_abi_dp -->
+    <Type Name="nlohmann::json_abi_dp::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_dp::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_dp_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_dp_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_dp_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_bics -->
+    <Type Name="nlohmann::json_abi_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
     <!-- Namespace nlohmann::json_abi_diag_ldvcmp -->
     <Type Name="nlohmann::json_abi_diag_ldvcmp::basic_json&lt;*&gt;">
         <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp::detail::value_t::null">null</DisplayString>
@@ -275,4 +395,604 @@
         </Expand>
     </Type>
 
+    <!-- Namespace nlohmann::json_abi_diag_dp -->
+    <Type Name="nlohmann::json_abi_diag_dp::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_dp::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_dp_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_diag_dp_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_dp_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_bics -->
+    <Type Name="nlohmann::json_abi_diag_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_diag_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_ldvcmp_dp -->
+    <Type Name="nlohmann::json_abi_ldvcmp_dp::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_ldvcmp_dp::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_ldvcmp_dp_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_ldvcmp_dp_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_ldvcmp_dp_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_ldvcmp_bics -->
+    <Type Name="nlohmann::json_abi_ldvcmp_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_ldvcmp_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_ldvcmp_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_ldvcmp_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_ldvcmp_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_dp_bics -->
+    <Type Name="nlohmann::json_abi_dp_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_dp_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_dp_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_dp_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_dp_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_dp_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_ldvcmp_dp -->
+    <Type Name="nlohmann::json_abi_diag_ldvcmp_dp::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_ldvcmp_dp::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_ldvcmp_dp_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_ldvcmp_bics -->
+    <Type Name="nlohmann::json_abi_diag_ldvcmp_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_ldvcmp_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_ldvcmp_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_dp_bics -->
+    <Type Name="nlohmann::json_abi_diag_dp_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_dp_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_dp_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_diag_dp_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_dp_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_dp_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_ldvcmp_dp_bics -->
+    <Type Name="nlohmann::json_abi_ldvcmp_dp_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_ldvcmp_dp_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_ldvcmp_dp_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_ldvcmp_dp_bics -->
+    <Type Name="nlohmann::json_abi_diag_ldvcmp_dp_bics::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_ldvcmp_dp_bics::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Namespace nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0 -->
+    <Type Name="nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::basic_json&lt;*&gt;">
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::null">null</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::object">{*(m_data.m_value.object)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::array">{*(m_data.m_value.array)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::string">{*(m_data.m_value.string)}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::boolean">{m_data.m_value.boolean}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::number_integer">{m_data.m_value.number_integer}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::number_unsigned">{m_data.m_value.number_unsigned}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::number_float">{m_data.m_value.number_float}</DisplayString>
+        <DisplayString Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::discarded">discarded</DisplayString>
+        <Expand>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::object">
+                *(m_data.m_value.object),view(simple)
+            </ExpandedItem>
+            <ExpandedItem Condition="m_data.m_type == nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::detail::value_t::array">
+                *(m_data.m_value.array),view(simple)
+            </ExpandedItem>
+        </Expand>
+    </Type>
+
+    <!-- Skip the pair first/second members in the treeview while traversing a map.
+         Only works in VS 2015 Update 2 and beyond using the new visualization -->
+    <Type Name="std::pair&lt;*, nlohmann::json_abi_diag_ldvcmp_dp_bics_v3_12_0::basic_json&lt;*&gt;&gt;" IncludeView="MapHelper">
+        <DisplayString>{second}</DisplayString>
+        <Expand>
+            <ExpandedItem>second</ExpandedItem>
+        </Expand>
+    </Type>
+
 </AutoVisualizer>

single_include/nlohmann/json_fwd.hpp

@@ -52,6 +52,10 @@
     #define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
 #endif
 
+#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
+    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -70,20 +74,27 @@
     #define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON
 #endif
 
+#if JSON_BRACE_INIT_COPY_SEMANTICS
+    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS _bics
+#else
+    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
+#endif
+
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
     #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif
 
 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c) json_abi ## a ## b ## c
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
-            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS)
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

tests/CMakeLists.txt

@@ -75,7 +75,12 @@ target_compile_options(test_main PUBLIC
     #                              is annotated JSON_HEDLEY_NO_RETURN (it always throws), which
     #                              makes MSVC flag the code following its call in binary_reader.hpp
     #                              as unreachable for that instantiation, in both Debug and Release
-    $<$<CXX_COMPILER_ID:MSVC>:/W4;/wd4566;/wd4996;/wd4702>
+    #       Disable warning C4503: decorated name length exceeded, name was truncated; the deep
+    #                              copy support added for #5387 pushes the mangled name of
+    #                              std::allocator_traits<...>::construct for the custom-base-class
+    #                              test's map type past VS2015's limit. The name is only used for
+    #                              debug info, so truncation does not affect the build.
+    $<$<CXX_COMPILER_ID:MSVC>:/W4;/wd4566;/wd4996;/wd4702;/wd4503>
     # https://github.com/nlohmann/json/issues/1114
     $<$<CXX_COMPILER_ID:MSVC>:/bigobj> $<$<BOOL:${MINGW}>:-Wa,-mbig-obj>
 

tests/abi/config/CMakeLists.txt

@@ -14,6 +14,20 @@ add_test(
     NAME test-abi_config_noversion
     COMMAND abi_config_noversion ${DOCTEST_TEST_FILTER})
 
+# test default and no version namespace with all ABI tags enabled, so the
+# expected tag order is checked regardless of the JSON_* CMake options
+foreach(test default noversion)
+    add_executable(abi_config_${test}_all_tags ${test}.cpp)
+    target_compile_definitions(abi_config_${test}_all_tags PRIVATE
+        JSON_DIAGNOSTICS=1
+        JSON_DIAGNOSTIC_POSITIONS=1
+        JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1)
+    target_link_libraries(abi_config_${test}_all_tags PRIVATE abi_compat_main)
+    add_test(
+        NAME test-abi_config_${test}_all_tags
+        COMMAND abi_config_${test}_all_tags ${DOCTEST_TEST_FILTER})
+endforeach()
+
 # test custom namespace
 add_executable(abi_config_custom custom.cpp)
 target_link_libraries(abi_config_custom PRIVATE abi_compat_main)

tests/abi/config/default.cpp

@@ -24,12 +24,16 @@ TEST_CASE("default namespace")
         expected += "_diag";
 #endif
 
+#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+        expected += "_ldvcmp";
+#endif
+
 #if JSON_DIAGNOSTIC_POSITIONS
         expected += "_dp";
 #endif
 
-#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
-        expected += "_ldvcmp";
+#if JSON_BRACE_INIT_COPY_SEMANTICS
+        expected += "_bics";
 #endif
 
         expected += "_v" STRINGIZE(NLOHMANN_JSON_VERSION_MAJOR);

tests/abi/config/noversion.cpp

@@ -25,12 +25,16 @@ TEST_CASE("default namespace without version component")
         expected += "_diag";
 #endif
 
+#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+        expected += "_ldvcmp";
+#endif
+
 #if JSON_DIAGNOSTIC_POSITIONS
         expected += "_dp";
 #endif
 
-#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
-        expected += "_ldvcmp";
+#if JSON_BRACE_INIT_COPY_SEMANTICS
+        expected += "_bics";
 #endif
 
         expected += "::basic_json";

tests/src/fuzzer-parse_bjdata.cpp

@@ -21,16 +21,50 @@ array data, it performs the following steps:
 - j4 = from_bjdata(vec3)
 - assert(j1 == j4)
 
+Re-serializing j2/j3/j4 with the same use_size/use_type settings is checked
+for value-stability rather than byte-exact stability: from_bjdata(to_bjdata(j2))
+must equal j2 (and likewise for j3, j4). Byte-exact stability does not hold in
+general, because a BJData value can lose type fidelity across a round trip
+(e.g. a binary_t value serialized without the optimized "$U#" array header is
+parsed back as a plain array of numbers, see #5398 and the discussion on
+PR #5494) - the numeric value is preserved, but the writer's smallest-type
+selection for the now-plain numbers may legitimately pick a different, but
+equally valid, single-byte type marker than the dedicated binary-data writer
+would have. Both encodings are valid BJData and both decode to the same
+value, so this is not treated as a round-trip failure here.
+
+"Value-stable" is checked by comparing dump()s rather than with operator==
+directly: a BJData/UBJSON payload can decode to a non-finite double (NaN or
++-Infinity), and IEEE 754 NaN is never equal to itself, so operator== would
+report two structurally-identical trees as different whenever a NaN is
+involved -- not a round-trip bug, just NaN's ordinary (non-)reflexivity.
+dump() serializes any non-finite double the same deterministic way (as JSON
+`null`, since JSON itself cannot represent NaN/Infinity), so comparing
+dumps is stable under exactly the same values that break operator==.
+
 The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
+// value-stable comparison for the round-trip checks below; see the note
+// above on why this compares dump()s rather than the json values directly
+static bool is_value_stable(const json& lhs, const json& rhs)
+{
+    return lhs.dump() == rhs.dump();
+}
+
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
@@ -56,10 +90,12 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
             json const j3 = json::from_bjdata(vec3);
             json const j4 = json::from_bjdata(vec4);
 
-            // serializations must match
-            assert(json::to_bjdata(j2, false, false) == vec2);
-            assert(json::to_bjdata(j3, true, false) == vec3);
-            assert(json::to_bjdata(j4, true, true) == vec4);
+            // re-serializing must be value-stable (see the notes above on
+            // why byte-exact stability is not guaranteed in general, and
+            // why this compares dump()s rather than the values directly)
+            assert(is_value_stable(json::from_bjdata(json::to_bjdata(j2, false, false)), j2));
+            assert(is_value_stable(json::from_bjdata(json::to_bjdata(j3, true, false)), j3));
+            assert(is_value_stable(json::from_bjdata(json::to_bjdata(j4, true, true)), j4));
         }
         catch (const json::parse_error&)
         {

tests/src/fuzzer-parse_bson.cpp

@@ -19,10 +19,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_cbor.cpp

@@ -19,10 +19,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_json.cpp

@@ -20,10 +20,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_msgpack.cpp

@@ -19,10 +19,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_ubjson.cpp

@@ -25,10 +25,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html