Sourced from nlohmann_json's releases.

JSON for Modern C++ version 3.12.0

Release date: 2025-04-11 SHA-256: aaf127c04cb31c406e5b04a63f1ae89369fccde6d8fa7cdda1ed4f32dfc5de63 (json.hpp), b8cb0ef2dd7f57f18933997c9934bb1fa962594f701cd5a8d3c2c80541559372 (include.zip), 42f6e95cad6ec532fd372391373363b62a14af6d771056dbfc86160e6dfff7aa (json.tar.xz)

Summary

This release fixes some bugs found in the 3.11.3 release and adds some new features.

All changes are backward-compatible.

:moneybag: Note you can support this project via GitHub sponsors or PayPal.

Key updates and enhancements

• Diagnostic byte positions: A new macro, JSON_DIAGNOSTIC_POSITIONS, introduces member functions to query the byte positions of values in the input they were parsed from. When enabled, this information is also included in exceptions to help pinpoint errors. #4517 #4455 #4570 #4569 #4572 #4571 #4579 #4585 #4561
• Enhanced conversion macros: The conversion macros for arbitrary types now include several upgrades:
  • All macros are templated, supporting json, ordered_json, and any other basic_json specialization. #4597 #2528 #4377 #2532 #2843 #3810 #4608
  • Derived classes can now be seamlessly converted to/from JSON using the new NLOHMANN_DEFINE_DERIVED_TYPE_* macros. #4033 #2199 #4562
• Support for std::optional: The library now supports conversions from/to std::optional types when compiled with C++17. #1749 #4036
• Flexible string compatibility: Functions patch, diff, and flatten now work with arbitrary string types. #4536 #4134 #4613 #4019
• Binary format enhancements:
  • The BJData mapping now supports draft 3, including optimized binary array types. #4513 #4588
  • The BSON mapping has added support for unsigned 64-bit integers. #4590 #4535 #3894
  • The get_number function used in the binary format implementations has been optimized to read multiple bytes at once. #4391
• Multidimensional array conversion: Multidimensional C-style arrays can now be directly converted to JSON. #4262 #4248
• Filesystem paths in UTF-8: The conversions from/to std::filesystem::path are now encoded to UTF-8 strings by default on all operating systems. #4271 #4631
• CMake 4.0 support. By adjusting the CMake minimal version to 3.5, CMake 4.0 can be used without warning or error. #4709

Changes and fixes

• The iteration_proxy is now a std::forward_iterator instead of just an std::input_iterator. This allows more use cases when items() is fed into C++20 std::views. The iterator always satisfied all requirements for a forward iterator, but was exposed as only an input iterator by the used iterator tag. #4371 #4372
• Fix the conversion from enums with unsigned underlying type to JSON. #4236 #4237
• Fix GDB pretty printer which was broken since m_data added. #4343 #4309
• Update natvis to reflect 3.11.3 and the current structure of basic_json. #4451 #4438 #4438
• Fix crash when passing nullptr to parse function expecting FILE*. Instead, now an exception is thrown. #4485 #4487
• Fix number parsing such that integers are not parsed to float when EINTR set in errno. #4506
• Fix SAX output of number_float to be locale-independent. #4505 #4084
• Fix iterators to allow comparing default-initialized iterators. #4512 #4493
• Fix return value of get_ptr for unsigned integers. #4525 #4475
• Fix regression of #2755 and replace EOF with char_traits. #4532
• Fix extended diagnostics to not trigger an assertion. #4537 #3915
• Fix NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT throw an exception with an empty json #4507 #4508
• Modernize integer comparison. #4577 #4559
• Serialize empty tuple into [] instead of null. #4594 #4530

Warnings

The quality assurance page gives an overview of the warning flags used during the tests.

Compiler warnings

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Sourced from nlohmann_json's changelog.

Changelog

All notable changes to this project will be documented in this file. This project adheres to Semantic Versioning.

unreleased (2024-12-22)

Full Changelog

• Impossible de read json file create with nlohmann::ordered_json::dump #4556
• Error C2039 : 'json_sax_dom_callback_parser': is not a member of 'nlohmann::json_abi_v3_11_3::detail' #4529
• json_fwd.hpp don't define default template arguments for ordered_map #4518
• new repo version seems stop create any the ingress-nginx controller with opentelemetry-cpp.git #4515
• Error converting to/from scoped enumerations #4499
• Default initialized iterators are not comparable #4493
• Bug json.exception.type_error.302 #4492
• tests fail to build with clang-19 and libc++ due to unsupported std::char_traits #4490
• Brace-Initialization Fails with json::parse and Key Access on Linux #4488
• Crash when parsing nullptr #4485
• Namespace macros are not respected in many instances #4484
• ohos model to json string garbage characters #4481
• Missing newlines in deserialized string #4479
• Latest tag not available on NuGet #4478
• Invalid union access for get_ref/get_ptr with unsigned integer #4475
• /accesswallet #4469
• struct reflect json with error C2440 #4467
• Compiler error when using macro NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE #4463
• Issue when dumping a vector of derived classes #4462
• whit std::wstring compile error #4460
• Inconsisten operator[] #4458
• json parse enclosing json object with [] #4457
• [bug] nlohmann::json constructor behaves improperly #4450
• parse OOM #4449
• Library Cannot Parse JSON File It Wrote #4448
• Unexpected Integer Conversion of JSON Values on ARM64 #4447
• Structure declared in natvis file template doesn't seem to match current structure of basic_json<> #4438
• A lot of EOT in json file #4436
• CVE-2024-34062 #4429
• CVE-2024-39689 #4428
• CVE-2024-5569 #4427
• CVE-2024-37891 #4426
• Tornado vulnerabilities #4425
• CVE-2024-35195 #4424
• CVE-2024-22195, CVE-2024-34064 #4423
• CVE-2024-3651 #4422
• CVE-2024-22190 #4421
• CVE-2024-39705 #4420
• Failing to read complex Unicode string embedded in JSON #4417
• Unable to parse JSON string from snake case to camel case #4399
• Crashes when I try to use ‘json::at()’ on a properly structured, non null, and correctly constructed ‘.json’ file #4387
• JSON_BuildTests fail when JSON_DisableEnumSerialization is set to ON #4384
• JSON can't parse a simple data #4383

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