Clarify hash documentation after review

- Say "may hash differently" for null, false, and numbers, since a
  collision across types is possible.
- Name the storage types (signed integer, unsigned integer,
  floating-point number) instead of example literals.
- Explain that the hash survives converting an integer to
  number_float_t but not the lossy conversion back, and that unequal
  numbers may share a hash.
- State that the example hash values are illustrative only and vary by
  platform, compiler, compiler version, and library version.

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

.github/CONTRIBUTING.md

@@ -205,6 +205,9 @@ API of the 3.x.y version is broken. This includes:
 - Changing access specifiers.
 - Changing default arguments.
 
+What is and is not covered by this guarantee is described in the
+[roadmap](https://json.nlohmann.me/community/roadmap/#api-stability).
+
 Although these guidelines may seem restrictive, they are essential for maintaining the library’s utility.
 
 Breaking changes may be introduced when they are guarded with a feature macro such as

.github/external_ci/appveyor.yml

@@ -16,6 +16,9 @@ only_commits:
 
 environment:
   matrix:
+    # The Visual Studio 2017 jobs compile everything with /std:c++17, so they
+    # only build the C++17 variant of each test, split into two jobs each to
+    # stay below AppVeyor's 60-minute limit per job.
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       configuration: Debug
       platform: x86
@@ -34,7 +37,13 @@ environment:
       configuration: Release
       platform: x86
       CXX_FLAGS: "/permissive- /std:c++17 /utf-8 /W4 /WX"
-      CMAKE_OPTIONS: ""
+      CMAKE_OPTIONS: "-DJSON_TestStandards=17 -DJSON_TestShard=0/2"
+      GENERATOR: Visual Studio 15 2017
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      configuration: Release
+      platform: x86
+      CXX_FLAGS: "/permissive- /std:c++17 /utf-8 /W4 /WX"
+      CMAKE_OPTIONS: "-DJSON_TestStandards=17 -DJSON_TestShard=1/2"
       GENERATOR: Visual Studio 15 2017
 
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
@@ -55,7 +64,13 @@ environment:
       configuration: Release
       platform: x64
       CXX_FLAGS: "/permissive- /std:c++17 /Zc:__cplusplus /utf-8 /W4 /WX"
-      CMAKE_OPTIONS: ""
+      CMAKE_OPTIONS: "-DJSON_TestStandards=17 -DJSON_TestShard=0/2"
+      GENERATOR: Visual Studio 15 2017
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      configuration: Release
+      platform: x64
+      CXX_FLAGS: "/permissive- /std:c++17 /Zc:__cplusplus /utf-8 /W4 /WX"
+      CMAKE_OPTIONS: "-DJSON_TestStandards=17 -DJSON_TestShard=1/2"
       GENERATOR: Visual Studio 15 2017
 
 init:
@@ -66,15 +81,10 @@ install:
   - if "%platform%"=="x86"    set GENERATOR_PLATFORM=Win32
 
 before_build:
-  - cmake . -G "%GENERATOR%" -A "%GENERATOR_PLATFORM%" -DCMAKE_CXX_FLAGS="%CXX_FLAGS%" -DCMAKE_IGNORE_PATH="C:/Program Files/Git/usr/bin" -DJSON_BuildTests=On "%CMAKE_OPTIONS%"
+  - cmake . -G "%GENERATOR%" -A "%GENERATOR_PLATFORM%" -DCMAKE_CXX_FLAGS="%CXX_FLAGS%" -DCMAKE_IGNORE_PATH="C:/Program Files/Git/usr/bin" -DJSON_BuildTests=On %CMAKE_OPTIONS%
 
 build_script:
   - cmake --build . --config "%configuration%" --parallel 2
 
 test_script:
-  - if "%configuration%"=="Release" ctest -C "%configuration%" --parallel 2 --output-on-failure
+  - ctest -C "%configuration%" --parallel 2 --output-on-failure
-  # On Debug builds, skip test-unicode_all
-  # as it is extremely slow to run and cause
-  # occasional timeouts on AppVeyor.
-  # More info: https://github.com/nlohmann/json/pull/1570
-  - if "%configuration%"=="Debug" ctest --exclude-regex "test-unicode" -C "%configuration%" --parallel 2 --output-on-failure

.github/workflows/macos.yml

@@ -17,11 +17,11 @@ permissions:
   contents: read
 
 jobs:
-  macos-14:
+  macos-15:
-    runs-on: macos-14 # https://github.com/actions/runner-images/blob/main/images/macos/macos-14-Readme.md
+    runs-on: macos-15 # https://github.com/actions/runner-images/blob/main/images/macos/macos-15-Readme.md
     strategy:
       matrix:
-        xcode: ['15.0.1', '15.1', '15.2', '15.3', '15.4']
+        xcode: ['16.0', '16.1', '16.2', '16.3', '16.4', '26.0.1', '26.1.1', '26.2', '26.3']
     env:
       DEVELOPER_DIR: /Applications/Xcode_${{ matrix.xcode }}.app/Contents/Developer
 
@@ -36,11 +36,11 @@ jobs:
       - name: Test
         run: cd build ; ctest -j 10 --output-on-failure
 
-  macos-15:
+  macos-26:
-    runs-on: macos-15 # https://github.com/actions/runner-images/blob/main/images/macos/macos-15-Readme.md
+    runs-on: macos-26 # https://github.com/actions/runner-images/blob/main/images/macos/macos-26-arm64-Readme.md
     strategy:
       matrix:
-        xcode: ['16.0', '16.1', '16.2', '16.3', '16.4', '26.0.1']
+        xcode: ['26.4.1', '26.5', '26.6']
     env:
       DEVELOPER_DIR: /Applications/Xcode_${{ matrix.xcode }}.app/Contents/Developer
 
@@ -71,3 +71,38 @@ jobs:
         run: cmake --build build --parallel 10
       - name: Test
         run: cd build ; ctest -j 10 --output-on-failure
+
+  swiftpm:
+    runs-on: macos-15
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Check that Package.swift resolves without a deprecation warning
+        run: swift package dump-package
+      - name: Build the SwiftPM documentation example against this checkout
+        run: |
+          mkdir -p /tmp/json-swiftpm-consumer/Sources/MyLibrary
+          cp docs/mkdocs/docs/integration/swift/example.cpp /tmp/json-swiftpm-consumer/Sources/MyLibrary/example.cpp
+          cat > /tmp/json-swiftpm-consumer/Package.swift << EOF
+          // swift-tools-version: 5.9
+          import PackageDescription
+
+          let package = Package(
+              name: "MyPackage",
+              dependencies: [
+                  .package(path: "${{ github.workspace }}")
+              ],
+              targets: [
+                  .target(
+                      name: "MyLibrary",
+                      dependencies: [
+                          .product(name: "json", package: "json")
+                      ],
+                      publicHeadersPath: "."
+                  )
+              ]
+          )
+          EOF
+          cd /tmp/json-swiftpm-consumer
+          swift build

.github/workflows/ubuntu.yml

@@ -107,7 +107,7 @@ jobs:
     container: ubuntu:24.04
     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_disableenumserialization, ci_test_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_no_thread_local]
+        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_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_delete_deprecated_functions, ci_test_no_thread_local]
     steps:
       - name: Install build-essential
         run: apt-get update ; apt-get install -y build-essential unzip wget git
@@ -209,7 +209,7 @@ jobs:
     strategy:
       matrix:
         # older GCC docker images (4, 5, 6) fail to check out code
-        compiler: ['7', '8', '9', '10', '11', '12', '13', '14', '15', 'latest']
+        compiler: ['7', '8', '9', '10', '11', '12', '13', '14', '15', '16', 'latest']
     container: gcc:${{ matrix.compiler }}
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1

.github/workflows/windows.yml

@@ -178,7 +178,7 @@ jobs:
       - name: Build
         run: cmake --build build --parallel 10
       - name: Test
-        run: cd build ; ctest -j 10 -C Debug --exclude-regex "test-unicode" --output-on-failure
+        run: cd build ; ctest -j 10 -C Debug --output-on-failure
 
   clang-cl-12:
     runs-on: windows-2022
@@ -195,7 +195,7 @@ jobs:
       - name: Build
         run: cmake --build build --config Debug --parallel 10
       - name: Test
-        run: cd build ; ctest -j 10 -C Debug --exclude-regex "test-unicode" --output-on-failure
+        run: cd build ; ctest -j 10 -C Debug --output-on-failure
 
   ci_module_cpp20:
     runs-on: windows-2022

.inferconfig

@@ -1,5 +1,7 @@
 {
   "_comment": "Used by the ci_infer CMake target (#5715 item 4b). fail-on-issue makes CI fail on Infer findings; disable-issue-type is a type-level baseline for the ~174 pre-existing findings (all PULSE_UNNECESSARY_COPY*/PULSE_RESOURCE_LEAK/PULSE_CONST_REFABLE, mostly in test code) triaged in run https://github.com/nlohmann/json/actions/runs/35829411620 on commit 1054b2097, so CI fails only on a NEW issue type. Remove an entry here once its findings have been fixed or explicitly accepted.",
+  "_comment_pulse": "Pulse stops exploring paths after pulse-max-disjuncts (default 20). With the default, basic_json::replace_value() (destroy + assert_invariant) exceeds the limit, Pulse loses the stored type, and reports false NULLPTR_DEREFERENCE findings for get_ptr() results in tests/src/unit-pointer_access.cpp.",
+  "pulse-max-disjuncts": 40,
   "fail-on-issue": true,
   "disable-issue-type": [
     "PULSE_UNNECESSARY_COPY_ASSIGNMENT",

.reuse/dep5

@@ -1,36 +0,0 @@
-Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
-Upstream-Name: json
-Upstream-Contact: Niels Lohmann <mail@nlohmann.me>
-Source: https://github.com/nlohmann/json
-
-Files: *
-Copyright: 2013-2026 Niels Lohmann <https://nlohmann.me>
-License: MIT
-
-Files: include/nlohmann/thirdparty/hedley.hpp
-Copyright: 2016-2021 Evan Nemerson <evan@nemerson.com>
-License: CC0
-
-Files: include/nlohmann/detail/meta/cpp_future.hpp
-Copyright: 2013-2026 Niels Lohmann <https://nlohmann.me> and 2018 The Abseil Authors
-License: MIT AND Apache-2.0
-
-Files: tests/thirdparty/doctest/*
-Copyright: 2016-2023 Viktor Kirilov
-License: MIT
-
-Files: tests/thirdparty/fifo_map/*
-Copyright: 2015-2017 Niels Lohmann
-License: MIT
-
-Files: tests/thirdparty/imapdl/*
-Copyright: 2017 Georg Sauthoff <mail@gms.tf>
-License: GPL-3.0-only
-
-Files: tools/amalgamate/*
-Copyright: 2012 Erik Edlund <erik.edlund@32767.se>
-License: BSD-3-Clause
-
-Files: tools/gdb_pretty_printer/*
-Copyright: 2020 Hannes Domani <https://github.com/ssbssa>
-License: MIT

BUILD.bazel

@@ -80,6 +80,7 @@ cc_library(
     name = "singleheader-json",
     hdrs = [
         "single_include/nlohmann/json.hpp",
+        "single_include/nlohmann/json_fwd.hpp",
     ],
     includes = ["single_include"],
     visibility = ["//visibility:public"],

CITATION.cff

@@ -10,5 +10,5 @@ title: "JSON for Modern C++"
 version: 3.12.0
 date-released: 2025-04-07
 license: MIT
-repository-code: "https://github.com/nlohmann"
+repository-code: "https://github.com/nlohmann/json"
 url: https://json.nlohmann.me

CMakeLists.txt

@@ -42,8 +42,11 @@ endif()
 ## OPTIONS
 ##
 
+# Build the tests by default only for the main project and only if the tests
+# directory exists (the release archive json.tar.xz does not contain it).
 # VERSION_GREATER_EQUAL is not available in older CMake (< 3.7)
-if(${MAIN_PROJECT} AND (${CMAKE_VERSION} VERSION_EQUAL 3.13 OR ${CMAKE_VERSION} VERSION_GREATER 3.13))
+if(${MAIN_PROJECT} AND (${CMAKE_VERSION} VERSION_EQUAL 3.13 OR ${CMAKE_VERSION} VERSION_GREATER 3.13)
+   AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/tests/CMakeLists.txt")
     set(JSON_BuildTests_INIT ON)
 else()
     set(JSON_BuildTests_INIT OFF)
@@ -62,6 +65,7 @@ option(JSON_MultipleHeaders                "Use non-amalgamated version of the l
 option(JSON_SystemInclude                  "Include as system headers (skip for clang-tidy)." OFF)
 option(JSON_StrictNulHandling              "Build with strict NUL-byte handling enabled." OFF)
 option(JSON_StrictBinaryUTF8               "Build with UTF-8 checks in the CBOR, UBJSON, BJData, and BSON writers enabled." OFF)
+option(JSON_DeleteDeprecatedFunctions      "Delete the deprecated functions instead of only deprecating them." OFF)
 
 if (JSON_CI)
     include(ci)
@@ -123,6 +127,10 @@ if (JSON_StrictBinaryUTF8)
     message(STATUS "Strict UTF-8 checks in binary writers enabled (JSON_STRICT_BINARY_UTF8=1)")
 endif()
 
+if (JSON_DeleteDeprecatedFunctions)
+    message(STATUS "Deprecated functions are deleted (JSON_DELETE_DEPRECATED_FUNCTIONS=1)")
+endif()
+
 if (JSON_Diagnostic_Positions)
     message(STATUS "Diagnostic positions enabled (JSON_DIAGNOSTIC_POSITIONS=1)")
 endif()
@@ -159,6 +167,7 @@ target_compile_definitions(
     $<$<BOOL:${JSON_LegacyDiscardedValueComparison}>:JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1>
     $<$<BOOL:${JSON_StrictNulHandling}>:JSON_STRICT_NUL_HANDLING=1>
     $<$<BOOL:${JSON_StrictBinaryUTF8}>:JSON_STRICT_BINARY_UTF8=1>
+    $<$<BOOL:${JSON_DeleteDeprecatedFunctions}>:JSON_DELETE_DEPRECATED_FUNCTIONS=1>
 )
 
 target_include_directories(

FILES.md

@@ -196,19 +196,19 @@ Further documentation:
 
 ## REUSE
 
-### `.reuse/dep5`
+### `REUSE.toml`
 
 The file defines the licenses of certain third-party components in the repository. The root `Makefile` contains a target `reuse` that checks for compliance.
 
 Further documentation:
 
-- [DEP5](https://reuse.software/spec-3.2/#dep5-deprecated)
+- [REUSE.toml](https://reuse.software/spec-3.3/#reusetoml)
 - [reuse command-line tool](https://pypi.org/project/reuse/)
 - [documentation of linting](https://reuse.readthedocs.io/en/stable/man/reuse-lint.html)
 - [REUSE](http://reuse.software)
 
 > [!IMPORTANT]
-> The filename `.reuse/dep5` is predetermined by REUSE. Alternatively, a `REUSE.toml` file can be used.
+> The filename `REUSE.toml` is predetermined by REUSE. Alternatively, a `.reuse/dep5` file (deprecated) can be used.
 
 ### `.reuse/templates`
 

Makefile

@@ -7,6 +7,9 @@
 # find GNU sed to use `-i` parameter
 SED:=$(shell command -v gsed || which sed)
 
+# find GNU tar to use `--sort` and `--pax-option` parameters
+TAR:=$(shell command -v gtar || which tar)
+
 
 ##########################################################################
 # source files
@@ -174,8 +177,8 @@ ChangeLog.md:
 # archive is created according to the advices of <https://reproducible-builds.org/docs/archives/>.
 json.tar.xz:
 	mkdir json
-	rsync -R $(shell find LICENSE.MIT nlohmann_json.natvis CMakeLists.txt cmake/*.in include single_include -type f) json
+	rsync -R $(shell find LICENSE.MIT nlohmann_json.natvis CMakeLists.txt cmake/*.in include single_include src/modules -type f) json
-	gtar --sort=name --mtime="@$(shell git log -1 --pretty=%ct)" --owner=0 --group=0 --numeric-owner --pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime --create --file - json | xz --compress -9e --threads=2 - > json.tar.xz
+	$(TAR) --sort=name --mtime="@$(shell git log -1 --pretty=%ct)" --owner=0 --group=0 --numeric-owner --pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime --create --file - json | xz --compress -9e --threads=2 - > json.tar.xz
 	rm -fr json
 
 # We use `-X` to make the resulting ZIP file reproducible, see

Package.swift

@@ -6,7 +6,7 @@ import PackageDescription
 let package = Package(
     name: "nlohmann-json",
      platforms: [
-        .iOS(.v12), .macOS(.v10_13), .tvOS(.v12), .watchOS(.v4), .visionOS(.v1)
+        .iOS(.v12), .macOS(.v10_13), .tvOS(.v12), .watchOS(.v9), .visionOS(.v1)
     ],
     products: [
         .library(name: "json", targets: ["json"])

README.md

@@ -7,7 +7,7 @@
 [![Coverage Status](https://coveralls.io/repos/github/nlohmann/json/badge.svg?branch=develop)](https://coveralls.io/github/nlohmann/json?branch=develop)
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/5550/badge.svg)](https://scan.coverity.com/projects/nlohmann-json)
 [![Codacy Badge](https://app.codacy.com/project/badge/Grade/e0d1a9d5d6fd46fcb655c4cb930bb3e8)](https://app.codacy.com/gh/nlohmann/json/dashboard?utm_source=gh&utm_medium=referral&utm_content=&utm_campaign=Badge_grade)
-[![Fuzzing Status](https://oss-fuzz-build-logs.storage.googleapis.com/badges/json.svg)](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:json)
+[![Fuzzing Status](https://oss-fuzz-build-logs.storage.googleapis.com/badges/json.svg)](https://issues.oss-fuzz.com/issues?q=project:json)
 [![Try online](https://img.shields.io/badge/try-online-blue.svg)](https://wandbox.org/permlink/1mp10JbaANo6FUc7)
 [![Documentation](https://img.shields.io/badge/docs-mkdocs-blue.svg)](https://json.nlohmann.me)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/nlohmann/json/develop/LICENSE.MIT)
@@ -1202,15 +1202,18 @@ language bindings, format converters, and the like. See the curated [Ecosystem](
 
 Though it's 2026 already, the support for C++11 is still a bit sparse. Currently, the following compilers are known to work:
 
-- GCC 4.8 - 14.2 (and possibly later)
+- GCC 4.8 - 16.2 (and possibly later)
-- Clang 3.4 - 21.0 (and possibly later)
+- Clang 3.4 - 22.1 (and possibly later)
-- Apple Clang 9.1 - 16.0 (and possibly later)
+- Apple Clang 15.0 - 21.0 (and possibly later)
-- Intel C++ Compiler 17.0.2 (and possibly later)
+- Intel C++ Compiler Classic (icpc) 2021.10
-- Nvidia CUDA Compiler 11.0.221 (and possibly later)
+- Intel oneAPI DPC++/C++ Compiler (icpx) 2025.3 (and possibly later)
-- Microsoft Visual C++ 2015 / Build Tools 14.0.25123.0 (and possibly later)
+- NVIDIA CUDA Compiler (nvcc) 11.8 - 12.6 (and possibly later)
-- Microsoft Visual C++ 2017 / Build Tools 15.5.180.51428 (and possibly later)
+- NVIDIA HPC SDK C++ Compiler (nvc++) 25.5 (and possibly later)
-- Microsoft Visual C++ 2019 / Build Tools 16.3.1+1def00d3d (and possibly later)
+- Microsoft Visual C++ 2015 / MSVC 19.0 (and possibly later)
-- Microsoft Visual C++ 2022 / Build Tools 19.30.30709.0 (and possibly later)
+- Microsoft Visual C++ 2017 / MSVC 19.16 (and possibly later)
+- Microsoft Visual C++ 2019 / MSVC 19.29 (and possibly later)
+- Microsoft Visual C++ 2022 / MSVC 19.44 (and possibly later)
+- Microsoft Visual C++ 2026 / MSVC 19.51 (and possibly later)
 
 I would be happy to learn about other compilers/versions.
 
@@ -1401,7 +1404,7 @@ The library is compliant to version 3.3 of the [**REUSE specification**](https:/
 
 - Every source file contains an SPDX copyright header.
 - The full text of all licenses used in the repository can be found in the `LICENSES` folder.
-- File `.reuse/dep5` contains an overview of all files' copyrights and licenses.
+- File `REUSE.toml` contains an overview of all files' copyrights and licenses.
 - Run `pipx run reuse lint` to verify the project's REUSE compliance and `pipx run reuse spdx` to generate a SPDX SBOM.
 
 ## Contact

REUSE.toml

@@ -0,0 +1,52 @@
+version = 1
+SPDX-PackageName = "json"
+SPDX-PackageSupplier = "Niels Lohmann <mail@nlohmann.me>"
+SPDX-PackageDownloadLocation = "https://github.com/nlohmann/json"
+
+[[annotations]]
+path = "**"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2013-2026 Niels Lohmann <https://nlohmann.me>"
+SPDX-License-Identifier = "MIT"
+
+[[annotations]]
+path = "include/nlohmann/thirdparty/hedley.hpp"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2016-2021 Evan Nemerson <evan@nemerson.com>"
+SPDX-License-Identifier = "CC0"
+
+[[annotations]]
+path = "include/nlohmann/detail/meta/cpp_future.hpp"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2013-2026 Niels Lohmann <https://nlohmann.me> and 2018 The Abseil Authors"
+SPDX-License-Identifier = "MIT AND Apache-2.0"
+
+[[annotations]]
+path = "tests/thirdparty/doctest/**"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2016-2023 Viktor Kirilov"
+SPDX-License-Identifier = "MIT"
+
+[[annotations]]
+path = "tests/thirdparty/fifo_map/**"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2015-2017 Niels Lohmann"
+SPDX-License-Identifier = "MIT"
+
+[[annotations]]
+path = "tests/thirdparty/imapdl/**"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2017 Georg Sauthoff <mail@gms.tf>"
+SPDX-License-Identifier = "GPL-3.0-only"
+
+[[annotations]]
+path = "tools/amalgamate/**"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2012 Erik Edlund <erik.edlund@32767.se>"
+SPDX-License-Identifier = "BSD-3-Clause"
+
+[[annotations]]
+path = "tools/gdb_pretty_printer/**"
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2020 Hannes Domani <https://github.com/ssbssa>"
+SPDX-License-Identifier = "MIT"

cmake/ci.cmake

@@ -249,6 +249,20 @@ add_custom_target(ci_test_strict_nul_handling
     COMMENT "Compile and test with strict NUL-byte handling enabled"
 )
 
+###############################################################################
+# Delete the deprecated functions.
+###############################################################################
+
+add_custom_target(ci_test_delete_deprecated_functions
+    COMMAND ${CMAKE_COMMAND}
+    -DCMAKE_BUILD_TYPE=Debug -GNinja
+    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_DeleteDeprecatedFunctions=ON
+    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_delete_deprecated_functions
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_delete_deprecated_functions
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_delete_deprecated_functions && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
+    COMMENT "Compile and test with the deprecated functions deleted"
+)
+
 ###############################################################################
 # Disable global UDLs.
 ###############################################################################
@@ -362,7 +376,7 @@ add_custom_target(ci_test_coverage
 # Sanitizers.
 ###############################################################################
 
-set(CLANG_CXX_FLAGS_SANITIZER "-g -O1 -fsanitize=address -fsanitize=undefined -fsanitize=integer -fsanitize=nullability -fno-omit-frame-pointer -fno-sanitize-recover=all -fno-sanitize=unsigned-integer-overflow -fno-sanitize=unsigned-shift-base")
+set(CLANG_CXX_FLAGS_SANITIZER "-g -O1 -fsanitize=address -fsanitize=undefined -fsanitize=integer -fsanitize=nullability -fno-omit-frame-pointer -fno-sanitize-recover=all -fno-sanitize=unsigned-integer-overflow -fno-sanitize=unsigned-shift-base -fsanitize-ignorelist=${PROJECT_SOURCE_DIR}/cmake/clang_sanitizer_ignorelist.txt")
 
 add_custom_target(ci_test_clang_sanitizer
     COMMAND CXX=${CLANG_TOOL} CXXFLAGS=${CLANG_CXX_FLAGS_SANITIZER} ${CMAKE_COMMAND}
@@ -442,13 +456,14 @@ add_custom_target(ci_test_single_header
 # Valgrind.
 ###############################################################################
 
+# The Unicode test (~17M assertions) is too slow under Valgrind.
 add_custom_target(ci_test_valgrind
     COMMAND CXX=${GCC_TOOL} ${CMAKE_COMMAND}
         -DCMAKE_BUILD_TYPE=Debug -GNinja
         -DJSON_BuildTests=ON -DJSON_Valgrind=ON
         -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_valgrind
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_valgrind
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_valgrind && ${CMAKE_CTEST_COMMAND} -L valgrind --parallel ${N} --output-on-failure
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_valgrind && ${CMAKE_CTEST_COMMAND} -L valgrind --exclude-regex "test-unicode" --parallel ${N} --output-on-failure
     COMMENT "Compile and test with Valgrind"
 )
 
@@ -705,7 +720,7 @@ ci_get_cmake(4.0.0  CMAKE_4_0_0_BINARY)
 # the tests require CMake 3.13 or later, so they are excluded for CMake 3.5.0
 set(JSON_CMAKE_FLAGS_3_5_0 JSON_Diagnostics JSON_Diagnostic_Positions JSON_GlobalUDLs JSON_ImplicitConversions JSON_DisableEnumSerialization
     JSON_LegacyDiscardedValueComparison JSON_Install JSON_MultipleHeaders JSON_SystemInclude JSON_Valgrind
-    JSON_StrictNulHandling JSON_StrictBinaryUTF8)
+    JSON_StrictNulHandling JSON_StrictBinaryUTF8 JSON_DeleteDeprecatedFunctions)
 set(JSON_CMAKE_FLAGS_3_31_6 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
 set(JSON_CMAKE_FLAGS_4_0_0 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
 
@@ -773,7 +788,7 @@ foreach(COMPILER g++-4.8 g++-4.9 g++-5 g++-6 g++-7 g++-8 g++-9 g++-10 g++-11 cla
                 -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_compiler_${COMPILER}
                 ${ADDITIONAL_FLAGS}
             COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_compiler_${COMPILER}
-            COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_${COMPILER} && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode" --output-on-failure
+            COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_${COMPILER} && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
             COMMENT "Compile and test with ${COMPILER}"
         )
     endif()
@@ -787,7 +802,7 @@ add_custom_target(ci_test_compiler_default
         -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_compiler_default
         ${ADDITIONAL_FLAGS}
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_compiler_default --parallel ${N}
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_default && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode" -LE git_required --output-on-failure
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_default && ${CMAKE_CTEST_COMMAND} --parallel ${N} -LE git_required --output-on-failure
     COMMENT "Compile and test with default C++ compiler"
 )
 
@@ -825,7 +840,7 @@ add_custom_target(ci_icpc
         -DJSON_BuildTests=ON -DJSON_FastTests=ON
         -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_icpc
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_icpc
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_icpc && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode" --output-on-failure
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_icpc && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
     COMMENT "Compile and test with ICPC"
 )
 
@@ -836,7 +851,7 @@ add_custom_target(ci_icpx
         -DJSON_BuildTests=ON -DJSON_FastTests=ON
         -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_icpx
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_icpx
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_icpx && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode" --output-on-failure
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_icpx && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
     COMMENT "Compile and test with ICPX (Intel oneAPI DPC++/C++)"
 )
 
@@ -872,7 +887,7 @@ add_custom_target(ci_nvhpc
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_nvhpc
     # the pipes are escaped so the surrounding shell passes them to ctest verbatim
     # instead of treating them as shell pipe operators
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_nvhpc && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode\\|test-comparison_cpp20\\|test-comparison_legacy_cpp20\\|test-constructor1_cpp11\\|test-deserialization_cpp20" --output-on-failure
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_nvhpc && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-comparison_cpp20\\|test-comparison_legacy_cpp20\\|test-constructor1_cpp11\\|test-deserialization_cpp20" --output-on-failure
     COMMENT "Compile and test with NVIDIA HPC SDK (nvc++)"
 )
 

cmake/clang_sanitizer_ignorelist.txt

@@ -0,0 +1,8 @@
+# Sanitizer ignore list for ci_test_clang_sanitizer (-fsanitize-ignorelist).
+#
+# libstdc++ 14's <format> declares `_Scanner(basic_string_view<_CharT>, size_t __nargs = -1)`, so every std::format
+# call converts -1 to size_t, which -fsanitize=integer reports as implicit-integer-sign-change. This is
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119429, not a bug in this library. Only that check and only <format> are
+# excluded, so implicit sign changes in the library and the tests are still reported.
+[implicit-integer-sign-change]
+src:*/include/c++/*/format

cmake/scripts/gen_bazel_build_file.cmake

@@ -48,6 +48,7 @@ cc_library(
     name = "singleheader-json",
     hdrs = [
         "single_include/nlohmann/json.hpp",
+        "single_include/nlohmann/json_fwd.hpp",
     ],
     includes = ["single_include"],
     visibility = ["//visibility:public"],

cmake/scripts/gen_hedley_undef_check.cmake

@@ -64,7 +64,7 @@ if(MODE STREQUAL "undef")
     # recipe is self-contained and its output is byte-stable across reruns.
     # The embedded SPDX tags below are part of the *generated* file's
     # content, not a REUSE header for this .cmake script itself (which is
-    # already covered by the blanket "Files: *" rule in .reuse/dep5) -- keep
+    # already covered by the blanket path = "**" rule in REUSE.toml) -- keep
     # them wrapped in REUSE-IgnoreStart/End so `reuse lint` does not try to
     # parse "MIT\n")" as this file's own SPDX-License-Identifier value.
     # REUSE-IgnoreStart

docs/docset/docSet.sql

@@ -131,6 +131,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_string', 'Meth
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_ubjson', 'Function', 'api/basic_json/to_ubjson/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::value', 'Method', 'api/basic_json/value/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::value_t', 'Enum', 'api/basic_json/value_t/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::with_t', 'Type', 'api/basic_json/with_t/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::~basic_json', 'Method', 'api/basic_json/~basic_json/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('json', 'Class', 'api/json/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('json_pointer', 'Class', 'api/json_pointer/index.html');
@@ -219,6 +220,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('Supported Macros', 'Guide', '
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_ASSERT', 'Macro', 'api/macros/json_assert/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_BRACE_INIT_COPY_SEMANTICS', 'Macro', 'api/macros/json_brace_init_copy_semantics/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_CATCH_USER', 'Macro', 'api/macros/json_throw_user/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DELETE_DEPRECATED_FUNCTIONS', 'Macro', 'api/macros/json_delete_deprecated_functions/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DIAGNOSTICS', 'Macro', 'api/macros/json_diagnostics/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DIAGNOSTIC_POSITIONS', 'Macro', 'api/macros/json_diagnostic_positions/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DISABLE_ENUM_SERIALIZATION', 'Macro', 'api/macros/json_disable_enum_serialization/index.html');
@@ -249,6 +251,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('JSON_TRY_USER', 'Macro', 'api
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_USE_GLOBAL_UDLS', 'Macro', 'api/macros/json_use_global_udls/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_USE_IMPLICIT_CONVERSIONS', 'Macro', 'api/macros/json_use_implicit_conversions/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON', 'Macro', 'api/macros/json_use_legacy_discarded_value_comparison/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS', 'Macro', 'api/macros/json_use_objects_for_enum_keyed_maps/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_USE_SIMDUTF', 'Macro', 'api/macros/json_use_simdutf/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('Macros', 'Macro', 'api/macros/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE', 'Macro', 'api/macros/nlohmann_define_derived_type/index.html');

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

@@ -9,10 +9,10 @@ enum class cbor_tag_handler_t
 };
 ```
 
-This enumeration is used in the [`from_cbor`](from_cbor.md) function to choose how to treat tags:
+This enumeration is used in [`from_cbor`](from_cbor.md) and [`sax_parse`](sax_parse.md) to choose how to treat tags:
 
 error
-:   throw a `parse_error` exception in case of a tag
+:   report a parse error in case of a tag (the `from_cbor` overloads throw a `parse_error` exception by default)
 
 ignore
 :   ignore tags

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

@@ -8,7 +8,7 @@ static basic_json diff(const basic_json& source,
 Creates a [JSON Patch](http://jsonpatch.com) so that value `source` can be changed into the value `target` by calling
 [`patch`](patch.md) function.
 
-For two JSON values `source` and `target`, the following code yields always `#!cpp true`:
+For two JSON values `source` and `target`, the following code always yields `#!cpp true`:
 ```cpp
 source.patch(diff(source, target)) == target;
 ```
@@ -27,7 +27,7 @@ a JSON patch to convert the `source` to `target`
 
 ## Exception safety
 
-Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+Strong guarantee: `source` and `target` are never modified.
 
 ## Complexity
 

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

@@ -120,3 +120,12 @@ Linear in the size of the input.
 - 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.
 - Added `error_handler` parameter in version 3.13.0.
+
+!!! warning "Deprecation"
+
+    - Overload (2) replaces calls to `from_bjdata` with a pointer and a length as first two parameters, which has been
+      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      `#!cpp from_bjdata(ptr, len, ...);` with `#!cpp from_bjdata(ptr, ptr+len, ...);`.
+
+    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+    function.

docs/mkdocs/docs/api/basic_json/from_bon8.md

@@ -106,3 +106,12 @@ Linear in the size of the input.
 ## Version history
 
 - Added in version 3.13.0.
+
+!!! warning "Deprecation"
+
+    - Overload (2) replaces calls to `from_bon8` with a pointer and a length as first two parameters, which has been
+      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      `#!cpp from_bon8(ptr, len, ...);` with `#!cpp from_bon8(ptr, ptr+len, ...);`.
+
+    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+    function.

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

@@ -109,6 +109,9 @@ The class satisfies the following concept requirements:
 - **initializer_list_t** - type for initializer lists of `basic_json` values
 - [**input_format_t**](input_format_t.md) - type to choose the format to parse
 - [**json_sax_t**](../json_sax/index.md) - type for SAX events
+- [**with_object_t, with_array_t, with_string_t, with_boolean_t, with_integers_t, with_float_t, with_allocator_t,
+  with_json_serializer_t, with_binary_t, with_base_class_t**](with_t.md) - types to create a `basic_json` type with
+  one (or two) replaced template parameters
 
 ### Exceptions
 

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

@@ -55,6 +55,10 @@ This implementation does exactly follow this approach, as it uses double precisi
 smaller than `-1.79769313486232e+308` and values greater than `1.79769313486232e+308` will be stored as NaN internally
 and be serialized to `null`.
 
+During deserialization (from JSON text or any of the binary formats), a finite number that does not fit into
+`number_float_t` is rejected with [`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406), for
+example a double-precision number in a binary format when `number_float_t` is `#!cpp float`.
+
 ### Storage
 
 Floating-point number values are stored directly inside a `basic_json` type.

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

@@ -47,8 +47,9 @@ With the default values for `NumberIntegerType` (`std::int64_t`), the default va
 
 When the default type is used, the maximal integer number that can be stored is `9223372036854775807` (INT64_MAX) and
 the minimal integer number that can be stored is `-9223372036854775808` (INT64_MIN). Integer numbers that are out of
-range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers
+range will yield over/underflow when used in a constructor. During deserialization (from JSON text or any of the binary
-will automatically be stored as [`number_unsigned_t`](number_unsigned_t.md) or [`number_float_t`](number_float_t.md).
+formats), too large or small integer numbers will automatically be stored as [`number_unsigned_t`](number_unsigned_t.md)
+or [`number_float_t`](number_float_t.md).
 
 [RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
 > Note that when such software is used, numbers that are integers and are in the range [-2<sup>53</sup>+1, 2<sup>53</sup>-1] are

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

@@ -48,8 +48,9 @@ With the default values for `NumberUnsignedType` (`std::uint64_t`), the default
 
 When the default type is used, the maximal integer number that can be stored is `18446744073709551615` (UINT64_MAX) and
 the minimal integer number that can be stored is `0`. Integer numbers that are out of range will yield over/underflow
-when used in a constructor. During deserialization, too large or small integer numbers will automatically be stored
+when used in a constructor. During deserialization (from JSON text or any of the binary formats), too large or small
-as [`number_integer_t`](number_integer_t.md) or [`number_float_t`](number_float_t.md).
+integer numbers will automatically be stored as [`number_integer_t`](number_integer_t.md) or
+[`number_float_t`](number_float_t.md).
 
 [RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
 > Note that when such software is used, numbers that are integers and are in the range [-2<sup>53</sup>+1, 2<sup>53</sup>-1] are

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

@@ -8,7 +8,8 @@ static bool sax_parse(InputType&& i,
                       input_format_t format = input_format_t::json,
                       const bool strict = true,
                       const bool ignore_comments = false,
-                      const bool ignore_trailing_commas = false);
+                      const bool ignore_trailing_commas = false,
+                      const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error);
 
 // (2)
 template<class IteratorType, class SAX, class SentinelType = IteratorType>
@@ -17,13 +18,14 @@ static bool sax_parse(IteratorType first, SentinelType last,
                       input_format_t format = input_format_t::json,
                       const bool strict = true,
                       const bool ignore_comments = false,
-                      const bool ignore_trailing_commas = false);
+                      const bool ignore_trailing_commas = false,
+                      const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error);
 ```
 
 Read from input and generate SAX events
 
 1. Read from a compatible input.
-2. Read from a pair of character iterators, or an iterator and a sentinel of a different type (C++20 ranges support)
+2. Read from a pair of character iterators, or an iterator and a sentinel of a different type (C++20 ranges support).
     
     The value_type of the iterator must be an integral type with a size of 1, 2, or 4 bytes, which will be interpreted
     respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
@@ -82,6 +84,10 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
 :   whether trailing commas in arrays or objects should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
     (`#!cpp false`); (optional, `#!cpp false` by default)
 
+`tag_handler` (in)
+:   how to handle CBOR tags; see [`cbor_tag_handler_t`](cbor_tag_handler_t.md). Ignored for formats other than CBOR
+    (optional, `cbor_tag_handler_t::error` by default).
+
 `first` (in)
 :   iterator to the start of a character range
 
@@ -137,6 +143,7 @@ A UTF-8 byte order mark is silently ignored.
 - Added in version 3.2.0.
 - Ignoring comments via `ignore_comments` added in version 3.9.0.
 - Added `ignore_trailing_commas` in version 3.13.0.
+- Added `tag_handler` 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_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave a `#!cpp std::istream` positioned right

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

@@ -7,8 +7,14 @@ namespace std {
 ```
 
 Return a hash value for a JSON object. 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 `#!json null`, `#!cpp 0`, `#!cpp 0U`, and
+type of the JSON value is taken into account, so `#!json null`, `#!cpp false`, and numbers may hash differently from
-`#!cpp false`, etc.
+each other. Numbers that compare equal under [`operator==`](operator_eq.md) always hash equally, regardless of
+whether they are stored as signed integer, unsigned integer, or floating-point number.
+
+Numbers are hashed by their value converted to `number_float_t`. Converting an integer to `number_float_t` therefore
+keeps its hash, but converting a floating-point number to an integer type is lossy and can change it: `#!cpp 0.5`
+converts to `#!cpp 0`, which need not have the same hash. Unequal numbers can also share a hash value, for example two
+large integers that convert to the same `number_float_t`.
 
 ## Examples
 
@@ -26,7 +32,8 @@ type of the JSON value is taken into account to have different hash values for `
     --8<-- "examples/std_hash.output"
     ```
 
-    Note the output is platform-dependent.
+    The hash values shown are examples only. They depend on the platform, the compiler, and the compiler version, and
+    they can change between versions of this library. Do not persist them or rely on specific values.
 
 ## See also
 
@@ -36,3 +43,5 @@ type of the JSON value is taken into account to have different hash values for `
 
 - Added in version 1.0.0.
 - Extended for arbitrary basic_json types in version 3.10.5.
+- Numbers that compare equal hash equally since version 3.13.0; before, `#!cpp 0`, `#!cpp 0U`, and `#!cpp 0.0` had
+  different hash values.

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

@@ -68,6 +68,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key in `j` is
   not valid UTF-8 and `error_handler` is `strict` (the default only if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled)
+- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is
+  discarded; example: `"cannot serialize discarded value to BJData"`
 
 ## Complexity
 
@@ -120,3 +122,5 @@ Linear in the size of the JSON value `j`.
 - Added `error_handler` parameter in version 3.13.0. Its default, `keep`, writes the bytes of a string or object key
   that is not valid UTF-8 unchanged, as before; `strict` (the default if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
+- Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
+  array or object was silently skipped, producing invalid BJData.

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

@@ -58,6 +58,9 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key is
   not valid UTF-8 and `error_handler` is `strict` (the default only if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled)
+- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if a value nested in `j` is discarded
+  (the top-level value itself is covered by `type_error.317` above, since it must be an object); example:
+  `"cannot serialize discarded value to BSON"`
 
 ## Complexity
 
@@ -110,6 +113,8 @@ pass before anything is written.
 - Throws `out_of_range.412` and `out_of_range.415` since version 3.13.0.
 - Linear in the size of `j`, and no longer limited by the call stack for deeply nested values, since version 3.13.0.
 - `out_of_range.415` is now detected before anything is written, like the other exceptions above, since version 3.13.0.
+- Throws `type_error.321` for a discarded value nested in `j` since version 3.13.0; previously, it was silently
+  skipped, producing a document whose declared size did not match what was actually written.
 - Added `error_handler` parameter in version 3.13.0. Its default, `keep`, writes the bytes of a string or object key
   that is not valid UTF-8 unchanged, as before; `strict` (the default if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316` before anything

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

@@ -49,6 +49,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key in `j` is
   not valid UTF-8 and `error_handler` is `strict` (the default only if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled)
+- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is
+  discarded; example: `"cannot serialize discarded value to CBOR"`
 
 ## Complexity
 
@@ -86,3 +88,5 @@ Linear in the size of the JSON value `j`.
 - Added `error_handler` parameter in version 3.13.0. Its default, `keep`, writes the bytes of a string or object key
   that is not valid UTF-8 unchanged, as before; `strict` (the default if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
+- Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
+  array or object was silently skipped, producing invalid CBOR.

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

@@ -54,6 +54,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   `"subtype 70000 is too large for the MessagePack ext type (max 255)"`
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key in `j` is
   not valid UTF-8 and `error_handler` is `strict`
+- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is
+  discarded; example: `"cannot serialize discarded value to MessagePack"`
 
 ## Complexity
 
@@ -108,3 +110,5 @@ Linear in the size of the JSON value `j`.
 - Fixed in version 3.13.0 to serialize `number_integer_t`/`number_unsigned_t` pairs of different width correctly;
   before, integers could be serialized with the wrong value if `number_integer_t` was narrower than
   `number_unsigned_t`.
+- Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
+  array or object was silently skipped, producing invalid MessagePack.

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

@@ -61,6 +61,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key in `j` is
   not valid UTF-8 and `error_handler` is `strict` (the default only if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled)
+- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is
+  discarded; example: `"cannot serialize discarded value to UBJSON"`
 
 ## Complexity
 
@@ -112,3 +114,5 @@ Linear in the size of the JSON value `j`.
 - Added `error_handler` parameter in version 3.13.0. Its default, `keep`, writes the bytes of a string or object key
   that is not valid UTF-8 unchanged, as before; `strict` (the default if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
+- Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
+  array or object was silently skipped, producing invalid UBJSON.

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

@@ -0,0 +1,136 @@
+# <small>nlohmann::basic_json::</small>with_t
+
+Member alias templates `with_object_t`, `with_array_t`, `with_string_t`, `with_boolean_t`, `with_integers_t`,
+`with_float_t`, `with_allocator_t`, `with_json_serializer_t`, `with_binary_t`, and `with_base_class_t`.
+
+```cpp
+template<template<typename, typename, typename...> class ObjectType2>
+using with_object_t = basic_json<ObjectType2, ArrayType, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<template<typename, typename...> class ArrayType2>
+using with_array_t = basic_json<ObjectType, ArrayType2, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<class StringType2>
+using with_string_t = basic_json<ObjectType, ArrayType, StringType2, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<class BooleanType2>
+using with_boolean_t = basic_json<ObjectType, ArrayType, StringType, BooleanType2,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<class NumberIntegerType2, class NumberUnsignedType2>
+using with_integers_t = basic_json<ObjectType, ArrayType, StringType, BooleanType,
+      NumberIntegerType2, NumberUnsignedType2, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<class NumberFloatType2>
+using with_float_t = basic_json<ObjectType, ArrayType, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType2,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<template<typename> class AllocatorType2>
+using with_allocator_t = basic_json<ObjectType, ArrayType, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType2, JSONSerializer, BinaryType, CustomBaseClass>;
+
+template<template<typename, typename = void> class JSONSerializer2>
+using with_json_serializer_t = basic_json<ObjectType, ArrayType, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer2, BinaryType, CustomBaseClass>;
+
+template<class BinaryType2>
+using with_binary_t = basic_json<ObjectType, ArrayType, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType2, CustomBaseClass>;
+
+template<class CustomBaseClass2>
+using with_base_class_t = basic_json<ObjectType, ArrayType, StringType, BooleanType,
+      NumberIntegerType, NumberUnsignedType, NumberFloatType,
+      AllocatorType, JSONSerializer, BinaryType, CustomBaseClass2>;
+```
+
+These member alias templates make it easier to create a `basic_json` type that is identical to the current type except
+for one (or, in the case of `with_integers_t`, two) of its [template parameters](index.md#template-parameters).
+Spelling out all 11 template parameters of `basic_json` just to change a single one is verbose and error-prone; these
+aliases only require the replacement type(s).
+
+with_object_t&lt;ObjectType2&gt;
+:   replaces `ObjectType`
+
+with_array_t&lt;ArrayType2&gt;
+:   replaces `ArrayType`
+
+with_string_t&lt;StringType2&gt;
+:   replaces `StringType`
+
+with_boolean_t&lt;BooleanType2&gt;
+:   replaces `BooleanType`
+
+with_integers_t&lt;NumberIntegerType2, NumberUnsignedType2&gt;
+:   replaces both `NumberIntegerType` and `NumberUnsignedType`; the two are combined into a single alias because they
+    are usually changed together (for instance, when switching to fixed-width integer types)
+
+with_float_t&lt;NumberFloatType2&gt;
+:   replaces `NumberFloatType`
+
+with_allocator_t&lt;AllocatorType2&gt;
+:   replaces `AllocatorType`
+
+with_json_serializer_t&lt;JSONSerializer2&gt;
+:   replaces `JSONSerializer`
+
+with_binary_t&lt;BinaryType2&gt;
+:   replaces `BinaryType`
+
+with_base_class_t&lt;CustomBaseClass2&gt;
+:   replaces `CustomBaseClass`; see also [`json_base_class_t`](json_base_class_t.md)
+
+## Notes
+
+All other template parameters are kept unchanged, so the resulting type still uses, for instance, the same
+`ObjectType` unless `with_object_t` itself is used.
+
+The aliases are members of every `basic_json` specialization, including [`ordered_json`](../ordered_json.md), and the
+type they produce is again a `basic_json` specialization. They can therefore be chained to replace several template
+parameters at once:
+
+```cpp
+using my_json = nlohmann::json::with_integers_t<int, unsigned int>::with_float_t<float>;
+using my_ordered_json = nlohmann::ordered_json::with_string_t<std::wstring>;
+```
+
+The result is the same type as spelling out all template parameters, so the order of the chained aliases does not
+matter. For instance, `nlohmann::json::with_object_t<nlohmann::ordered_map>` is `nlohmann::ordered_json`.
+
+## Examples
+
+??? example
+
+    The following code shows how `with_object_t` can be used to create a JSON type that stores object elements in a
+    `std::map` and therefore keeps them sorted by key, unlike the default type which preserves insertion order
+    only when `nlohmann::ordered_json` is used.
+
+    ```cpp
+    --8<-- "examples/with_t.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/with_t.output"
+    ```
+
+## See also
+
+- [basic_json](index.md#template-parameters) - the template parameters that can be replaced
+- [json_base_class_t](json_base_class_t.md) - the type used for `CustomBaseClass`
+
+## Version history
+
+- Added in version 3.13.0.

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

@@ -58,6 +58,13 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_DISABLE_ENUM_SERIALIZATION**](json_disable_enum_serialization.md) - switch off default serialization/deserialization functions for enums
 - [**JSON_DISABLE_TUPLE_REFERENCE_CONVERSION**](json_disable_tuple_reference_conversion.md) - switch off conversion from a one-element tuple of a JSON reference
 - [**JSON_USE_IMPLICIT_CONVERSIONS**](json_use_implicit_conversions.md) - control implicit conversions
+- [**JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS**](json_use_objects_for_enum_keyed_maps.md) - opt in to storing maps with enum
+  keys as objects
+
+## Deprecated functions
+
+- [**JSON_DELETE_DEPRECATED_FUNCTIONS**](json_delete_deprecated_functions.md) - opt in to deleting the deprecated
+  functions ahead of their removal in version 4.0.0
 
 ## Comparison behavior
 

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

@@ -50,9 +50,11 @@ The default value is `0` (disabled — existing behavior is preserved).
     ```
 
     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
+    element, and a single `[string, value]` pair *written as a braced list*, such as `{{"key", "value"}}`, which still
-    affected. The library's own conversions are not affected either: for example, `std::tuple<int>{5}` still becomes
+    creates an object, are not affected. This exception is based on how the pair is written, not on the shape of its
-    `[5]`.
+    value: an existing JSON value that happens to be a two-element array with a string as its first element, such as
+    `json arr = {"key", 42};`, is still copied by `json j{arr};` rather than turned into an object. The library's own
+    conversions are not affected either: for example, `std::tuple<int>{5}` still becomes `[5]`.
 
 !!! note "ABI compatibility"
 

docs/mkdocs/docs/api/macros/json_delete_deprecated_functions.md

@@ -0,0 +1,96 @@
+# JSON_DELETE_DEPRECATED_FUNCTIONS
+
+```cpp
+#define JSON_DELETE_DEPRECATED_FUNCTIONS /* value */
+```
+
+When defined to `1`, all [deprecated functions](../../community/roadmap.md#removal-of-deprecated-functions) of the
+library are declared as deleted (`= delete`) instead of only being marked as deprecated. Code that still calls one of
+them no longer compiles. This way, you can find all calls that need to be replaced before version 4.0.0 removes these
+functions; the [migration guide](../../integration/migration_guide.md#replace-deprecated-functions) describes how.
+
+A deleted function, unlike a removed one, still takes part in overload resolution. A call that would select it
+therefore fails to compile instead of silently selecting another overload. This matters for the deprecated
+`from_*(ptr, len)` overloads of [`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
+[`from_ubjson`](../basic_json/from_ubjson.md), [`from_bjdata`](../basic_json/from_bjdata.md),
+[`from_bon8`](../basic_json/from_bon8.md), and [`from_bson`](../basic_json/from_bson.md): without them, a call like
+`from_cbor(ptr, len)` would compile, read `ptr` as a NUL-terminated string, and convert `len` to the `strict` parameter.
+
+The macro does not affect the deprecated legacy comparison of discarded values, which is controlled by
+[`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](json_use_legacy_discarded_value_comparison.md).
+
+## Default definition
+
+The default value is `0` (disabled, the deprecated functions can still be called, and the compiler warns about it).
+
+```cpp
+#define JSON_DELETE_DEPRECATED_FUNCTIONS 0
+```
+
+## Notes
+
+!!! info "CMake option"
+
+    The macro can also be set with the CMake option
+    [`JSON_DeleteDeprecatedFunctions`](../../integration/cmake.md#json_deletedeprecatedfunctions) (`OFF` by default).
+
+!!! warning "Opt-in only"
+
+    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
+    effect. Define it for the whole project to avoid different declarations of the same class in different
+    translation units.
+
+!!! note "ABI compatibility"
+
+    The macro only turns calls that compile into calls that do not; it does not change the layout or the behavior of
+    any type. Its value is therefore not encoded in the [namespace](../../features/namespace.md).
+
+## Examples
+
+??? example "Example: default behavior (macro not defined)"
+
+    Without the macro, the deprecated overload is called, and the compiler warns about it:
+
+    ```cpp
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        const std::vector<std::uint8_t> v = {0x82, 0x01, 0x02};
+        auto j = json::from_cbor(v.data(), v.size());
+        // warning: 'from_cbor' is deprecated: Since 3.8.0; use from_cbor(ptr, ptr + len)
+    }
+    ```
+
+??? example "Example: deleted deprecated functions (macro defined to 1)"
+
+    With the macro, the call does not compile:
+
+    ```cpp
+    #define JSON_DELETE_DEPRECATED_FUNCTIONS 1
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        const std::vector<std::uint8_t> v = {0x82, 0x01, 0x02};
+        auto j = json::from_cbor(v.data(), v.size());
+        // error: call to deleted function 'from_cbor'
+    }
+    ```
+
+## See also
+
+- [Roadmap: removal of deprecated functions](../../community/roadmap.md#removal-of-deprecated-functions) - the
+  deprecated functions and the version they were deprecated in
+- [Migration guide: replace deprecated functions](../../integration/migration_guide.md#replace-deprecated-functions) -
+  how to replace each deprecated function
+
+## Version history
+
+- Added in version 3.13.0.
+- Planned to be removed in version 4.0.0, which removes the deprecated functions. The deprecated `from_*(ptr, len)`
+  overloads stay deleted in version 4.0.0.

docs/mkdocs/docs/api/macros/json_disable_tuple_reference_conversion.md

@@ -112,3 +112,4 @@ The default value is `0` (disabled — existing behavior is preserved).
 ## 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_use_implicit_conversions.md

@@ -44,7 +44,7 @@ By default, implicit conversions are enabled.
 
 ## Examples
 
-??? example "Example: implicit conversion"
+??? example "Example: implicit and explicit conversions"
 
     This is an example for an implicit conversion:
 

docs/mkdocs/docs/api/macros/json_use_objects_for_enum_keyed_maps.md

@@ -0,0 +1,139 @@
+# JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+
+```cpp
+#define JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS /* value */
+```
+
+When defined to `1`, maps whose keys are enums (such as `std::map<E, T>` or `std::unordered_map<E, T>`) are stored as
+JSON objects, using the enum's own conversion for the keys. By default, they are stored as arrays of `[key, value]`
+pairs.
+
+## Default definition
+
+The default value is `0` (disabled — existing behavior is preserved).
+
+```cpp
+#define JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS 0
+```
+
+## Notes
+
+!!! note "Background"
+
+    JSON object keys are strings, so a map is only stored as an object if its keys can be converted to a string type.
+    Enums are not, even if [`NLOHMANN_JSON_SERIALIZE_ENUM`](nlohmann_json_serialize_enum.md) maps them to strings, so a
+    map with enum keys becomes an array of `[key, value]` pairs:
+
+    ```json
+    [["stopped", "aa"], ["completed", "bb"]]
+    ```
+
+    With this macro, the same map becomes an object
+    (see [#4378](https://github.com/nlohmann/json/issues/4378)):
+
+    ```json
+    {"completed": "bb", "stopped": "aa"}
+    ```
+
+!!! note "Maps with non-unique keys"
+
+    Maps that allow duplicate keys, such as `std::multimap<E, T>` or `std::unordered_multimap<E, T>`, are not affected
+    by the macro and are still stored as arrays of `[key, value]` pairs, as an object cannot hold duplicate keys.
+
+!!! note "Reading"
+
+    Reading is not affected by the macro: a map with enum keys can always be read from both an array of pairs and an
+    object. For the latter, each key is converted to the enum with its `from_json` function, e.g., the one defined by
+    [`NLOHMANN_JSON_SERIALIZE_ENUM`](nlohmann_json_serialize_enum.md). Data written without the macro can therefore
+    still be read after enabling it.
+
+!!! warning "Keys must serialize to distinct strings"
+
+    Each key is converted with the enum's `to_json` function. If a key is not converted to a string (for instance, an
+    enum without [`NLOHMANN_JSON_SERIALIZE_ENUM`](nlohmann_json_serialize_enum.md), which is stored as an integer, or an
+    enumerator mapped to `nullptr`), [`type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302) is thrown.
+    If two keys are converted to the same string (for instance, because
+    [`NLOHMANN_JSON_SERIALIZE_ENUM`](nlohmann_json_serialize_enum.md) maps an unlisted enumerator to the first entry),
+    [`type_error.318`](../../home/exceptions.md#jsonexceptiontype_error318) is thrown. In both cases, the target value
+    is not changed.
+
+!!! warning "Opt-in only"
+
+    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no effect.
+
+!!! note "ABI compatibility"
+
+    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_ekmo`), 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.
+
+## Examples
+
+??? example "Example: default behavior (macro not defined)"
+
+    Without the macro, a map with enum keys is stored as an array of pairs:
+
+    ```cpp
+    #include <map>
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    enum TaskState { TS_STOPPED, TS_RUNNING, TS_COMPLETED };
+
+    NLOHMANN_JSON_SERIALIZE_ENUM(TaskState, {
+        {TS_STOPPED, "stopped"},
+        {TS_RUNNING, "running"},
+        {TS_COMPLETED, "completed"},
+    })
+
+    int main()
+    {
+        std::map<TaskState, std::string> m = {{TS_STOPPED, "aa"}, {TS_COMPLETED, "bb"}};
+
+        json j = m;
+        // j is [["stopped","aa"],["completed","bb"]]
+    }
+    ```
+
+??? example "Example: objects for enum-keyed maps (macro defined to 1)"
+
+    With the macro, the same map is stored as an object:
+
+    ```cpp
+    #define JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS 1
+    #include <map>
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    enum TaskState { TS_STOPPED, TS_RUNNING, TS_COMPLETED };
+
+    NLOHMANN_JSON_SERIALIZE_ENUM(TaskState, {
+        {TS_STOPPED, "stopped"},
+        {TS_RUNNING, "running"},
+        {TS_COMPLETED, "completed"},
+    })
+
+    int main()
+    {
+        std::map<TaskState, std::string> m = {{TS_STOPPED, "aa"}, {TS_COMPLETED, "bb"}};
+
+        json j = m;
+        // j is {"completed":"bb","stopped":"aa"}
+
+        auto m2 = j.get<std::map<TaskState, std::string>>();
+        // m2 == m
+    }
+    ```
+
+## See also
+
+- [Specializing enum conversion](../../features/enum_conversion.md)
+- [**NLOHMANN_JSON_SERIALIZE_ENUM**](nlohmann_json_serialize_enum.md) - serialize/deserialize an enum
+- [**NLOHMANN_JSON_SERIALIZE_ENUM_STRICT**](nlohmann_json_serialize_enum_strict.md) - serialize/deserialize an enum with
+  exceptions
+
+## Version history
+
+- Added in version 3.13.0.

docs/mkdocs/docs/api/macros/nlohmann_json_serialize_enum.md

@@ -41,6 +41,9 @@ inline void from_json(const BasicJsonType& j, type& e);
       conversion. Select this default pair carefully. See example 1 below.
     - If an enum or JSON value is specified in multiple conversions, the first matching conversion from the top of the
       list will be returned when converting to or from JSON. See example 2 below.
+    - Maps with enum keys (e.g., `std::map<ENUM_TYPE, T>`) are stored as arrays of `[key, value]` pairs by default.
+      Define [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](json_use_objects_for_enum_keyed_maps.md) to store them as objects
+      with the converted keys. Such maps can be read from both forms.
 
 ## Examples
 
@@ -80,6 +83,7 @@ inline void from_json(const BasicJsonType& j, type& e);
 - [Specializing enum conversion](../../features/enum_conversion.md)
 - [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](./nlohmann_json_serialize_enum_strict.md)
 - [`JSON_DISABLE_ENUM_SERIALIZATION`](json_disable_enum_serialization.md)
+- [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](json_use_objects_for_enum_keyed_maps.md)
 
 ## Version history
 

docs/mkdocs/docs/api/macros/nlohmann_json_serialize_enum_strict.md

@@ -44,6 +44,9 @@ inline void from_json(const BasicJsonType& j, type& e);
       `"enum value out of range for <type>"`.
     - If an enum or JSON value is specified in multiple conversions, the first matching conversion from the top of the
       list will be returned when converting to or from JSON. See example 2 below.
+    - Maps with enum keys (e.g., `std::map<ENUM_TYPE, T>`) are stored as arrays of `[key, value]` pairs by default.
+      Define [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](json_use_objects_for_enum_keyed_maps.md) to store them as objects
+      with the converted keys. Such maps can be read from both forms.
 
 ## Examples
 
@@ -99,6 +102,7 @@ inline void from_json(const BasicJsonType& j, type& e);
 - [Specializing enum conversion](../../features/enum_conversion.md)
 - [`NLOHMANN_JSON_SERIALIZE_ENUM`](./nlohmann_json_serialize_enum.md)
 - [`JSON_DISABLE_ENUM_SERIALIZATION`](json_disable_enum_serialization.md)
+- [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](json_use_objects_for_enum_keyed_maps.md)
 
 ## Version history
 

docs/mkdocs/docs/community/quality_assurance.md

@@ -21,17 +21,18 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
       
         | Compiler                                     | Architecture | Operating System                  | CI        |
         |----------------------------------------------|--------------|-----------------------------------|-----------|
-        | AppleClang 15.0.0.15000040; Xcode 15.0.1     | arm64        | macOS 14.7.2 (Sonoma)             | GitHub    |
-        | AppleClang 15.0.0.15000100; Xcode 15.1       | arm64        | macOS 14.7.2 (Sonoma)             | GitHub    |
-        | AppleClang 15.0.0.15000100; Xcode 15.2       | arm64        | macOS 14.7.2 (Sonoma)             | GitHub    |
-        | AppleClang 15.0.0.15000309; Xcode 15.3       | arm64        | macOS 14.7.2 (Sonoma)             | GitHub    |
-        | AppleClang 15.0.0.15000309; Xcode 15.4       | arm64        | macOS 14.7.2 (Sonoma)             | GitHub    |
         | AppleClang 16.0.0.16000026; Xcode 16         | arm64        | macOS 15.2 (Sequoia)              | GitHub    |
         | AppleClang 16.0.0.16000026; Xcode 16.1       | arm64        | macOS 15.2 (Sequoia)              | GitHub    |
         | AppleClang 16.0.0.16000026; Xcode 16.2       | arm64        | macOS 15.2 (Sequoia)              | GitHub    |
         | AppleClang 17.0.0.17000013; Xcode 16.3       | arm64        | macOS 15.5 (Sequoia)              | GitHub    |
         | AppleClang 17.0.0.17000013; Xcode 16.4       | arm64        | macOS 15.5 (Sequoia)              | GitHub    |
         | AppleClang 17.0.0.17000319; Xcode 26.0.1     | arm64        | macOS 15.5 (Sequoia)              | GitHub    |
+        | AppleClang 17.0.0.17000404; Xcode 26.1.1     | arm64        | macOS 15.7.9 (Sequoia)            | GitHub    |
+        | AppleClang 17.0.0.17000603; Xcode 26.2       | arm64        | macOS 15.7.9 (Sequoia)            | GitHub    |
+        | AppleClang 17.0.0.17000604; Xcode 26.3       | arm64        | macOS 15.7.9 (Sequoia)            | GitHub    |
+        | AppleClang 21.0.0.21000099; Xcode 26.4.1     | arm64        | macOS 26.6.2 (Tahoe)              | GitHub    |
+        | AppleClang 21.0.0.21000101; Xcode 26.5       | arm64        | macOS 26.6.2 (Tahoe)              | GitHub    |
+        | AppleClang 21.0.0.21000101; Xcode 26.6       | arm64        | macOS 26.6.2 (Tahoe)              | GitHub    |
         | Clang 3.4.2                                  | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | Clang 3.5.2                                  | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | Clang 3.6.2                                  | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
@@ -89,7 +90,7 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
         | GNU 13.3.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | GNU 14.2.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | GNU 15.1.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
-        | GNU 16.1.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
+        | GNU 16.2.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | GNU 16.1.0                                   | arm64        | Ubuntu 24.04                      | GitHub    |
         | icpc (ICC) 2021.10.0 20230609                | x86_64       | Ubuntu 22.04 LTS                  | GitHub    |
         | icpx (Intel oneAPI DPC++/C++) 2025.3.2       | x86_64       | Ubuntu 24.04 LTS                  | GitHub    |

docs/mkdocs/docs/community/roadmap.md

@@ -25,9 +25,7 @@ work items are tracked in the [GitHub milestones](https://github.com/nlohmann/js
 
 ## What the project will not do
 
-- **Break the public API of version 3.x.** See the
+- **Break the public API of version 3.x.** See [API stability](#api-stability) for what this covers.
-  [contribution guidelines](https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#break-the-public-api)
-  for what counts as a breaking change.
 - **Require a newer C++ standard than C++11.**
 - **Break JSON conformance** or enable non-standard extensions by default.
 - **Add dependencies** or require a build step. The library remains header-only, and the single header
@@ -35,6 +33,32 @@ work items are tracked in the [GitHub milestones](https://github.com/nlohmann/js
 - **Trade simplicity for speed or memory efficiency.** Performance improvements are welcome, but the library is not
   meant to compete with the fastest JSON libraries, see [Design goals](../home/design_goals.md).
 
+## API stability
+
+Releases follow [semantic versioning](https://semver.org): a minor or patch release of version 3.x does not break code
+that uses the public API. In particular, a 3.x release does not:
+
+- change the signature of a function (its parameter types, return type, number of parameters, or the const-ness of a
+  member function);
+- remove or rename a function or class;
+- change which exceptions a function throws, or the [exception ids](../home/exceptions.md);
+- change access specifiers or default arguments.
+
+Exceptions to these rules, for instance when fixing a bug requires changing the exception a function throws, are
+documented in the [release notes](../home/releases.md).
+
+The following are **not** part of the public API and may change in any release, including patch releases:
+
+- The text of exception messages returned by `what()`. Use the [exception id](../home/exceptions.md) to tell errors
+  apart.
+- The ABI, including `sizeof(basic_json)` and the memory layout of its values. Recompile your code when you upgrade the
+  library. The [versioned inline namespace](../features/namespace.md) turns mixing versions into a link error.
+- Everything in namespace `nlohmann::detail`, and macros and type traits that are not documented in the
+  [API reference](../api/basic_json/index.md).
+
+Changes that would break the public API are only added behind a macro whose default keeps the 3.x behavior, see
+[Version 4.0](#version-40).
+
 ## Version 4.0
 
 There is no release date for version 4.0 yet. Proposals that need a major version, for instance stricter type
@@ -64,6 +88,8 @@ The following macros guard changes that are planned to become the default in ver
 | [`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md)                                  | `0`         | `1`: reading from a stream does not consume the character after a number                                                      | –                                                                                                                  | 3.13.0 |
 | [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md)                                          | `0`         | `1`: a NUL byte in the input is a parse error instead of the end of input                                                     | [`JSON_StrictNulHandling`](../integration/cmake.md#json_strictnulhandling)                                         | 3.13.0 |
 | [`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md)                                            | `0`         | `1`: `to_cbor`, `to_ubjson`, `to_bjdata`, and `to_bson` throw for strings that are not valid UTF-8 by default                 | [`JSON_StrictBinaryUTF8`](../integration/cmake.md#json_strictbinaryutf8)                                           | 3.13.0 |
+| [`JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md)            | `0`         | `1`: a `basic_json` value can no longer be created from a one-element tuple of a reference to it, such as `std::forward_as_tuple(j)`| [`JSON_DisableTupleReferenceConversion`](../integration/cmake.md#json_disabletuplereferenceconversion)             | 3.13.0 |
+| [`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md)                          | `0`         | removed: the deprecated functions are removed (see below); the `from_*(ptr, len)` overloads stay deleted                      | [`JSON_DeleteDeprecatedFunctions`](../integration/cmake.md#json_deletedeprecatedfunctions)                         | 3.13.0 |
 
 For example, the following makes a 3.x release behave like version 4.0 with respect to these changes:
 
@@ -75,6 +101,8 @@ For example, the following makes a 3.x release behave like version 4.0 with resp
 #define JSON_PRECISE_STREAM_POSITION 1
 #define JSON_STRICT_NUL_HANDLING 1
 #define JSON_STRICT_BINARY_UTF8 1
+#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 1
+#define JSON_DELETE_DEPRECATED_FUNCTIONS 1
 #include <nlohmann/json.hpp>
 ```
 
@@ -84,8 +112,13 @@ way to achieve this.
 ### Removal of deprecated functions
 
 Version 4.0 will remove all deprecated functions. Compiling with deprecation warnings enabled shows which of them your
-code still uses. The [migration guide](../integration/migration_guide.md#replace-deprecated-functions) shows how to
+code still uses. Defining [`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md) to
-replace each of them.
+`1` turns these warnings into errors, as the deprecated functions are then deleted. The
+[migration guide](../integration/migration_guide.md#replace-deprecated-functions) shows how to replace each of them.
+
+The `from_*` overloads taking a pointer and a length are not removed in version 4.0, but stay deleted. Without them, a
+call like `from_cbor(ptr, len)` would still compile: it would read `ptr` as a NUL-terminated string and convert `len`
+to the `strict` parameter.
 
 | Deprecated                                                                                                                                                                                                                                         | Since  | Migration                                                                        |
 |----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|----------------------------------------------------------------------------------|
@@ -97,6 +130,7 @@ replace each of them.
 | [`json_pointer::operator string_t`](../api/json_pointer/operator_string_t.md)                                                                                                                                                                      | 3.11.0 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
 | [`json_pointer`](../api/json_pointer/index.md) with a `basic_json` type as template argument, and the overloads of `value`, `contains`, `operator[]`, and `at` accepting such a pointer                                                           | 3.11.0 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
 | Comparing a [`json_pointer`](../api/json_pointer/index.md) with a string via [`operator==`](../api/json_pointer/operator_eq.md) or [`operator!=`](../api/json_pointer/operator_ne.md)                                                              | 3.11.2 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
+| [`from_bjdata`](../api/basic_json/from_bjdata.md) and [`from_bon8`](../api/basic_json/from_bon8.md) with `(ptr, len)`                                                                                                                              | 3.13.0 | [Parsing](../integration/migration_guide.md#parsing)                             |
 
 The deprecated legacy comparison of discarded values is controlled by a macro and therefore listed in the table above.
 

docs/mkdocs/docs/examples/json_base_class_t.cpp

@@ -13,19 +13,7 @@ class visitor_adaptor_with_metadata
     void do_visit(const Ptr& ptr, const Fnc& fnc) const;
 };
 
-using json = nlohmann::basic_json <
+using json = nlohmann::json::with_base_class_t<visitor_adaptor_with_metadata>;
-             std::map,
-             std::vector,
-             std::string,
-             bool,
-             std::int64_t,
-             std::uint64_t,
-             double,
-             std::allocator,
-             nlohmann::adl_serializer,
-             std::vector<std::uint8_t>,
-             visitor_adaptor_with_metadata
-             >;
 
 template <class Fnc>
 void visitor_adaptor_with_metadata::visit(const Fnc& fnc) const

docs/mkdocs/docs/examples/std_hash.cpp

@@ -11,6 +11,7 @@ int main()
               << "hash(false) = " << std::hash<json> {}(json(false)) << '\n'
               << "hash(0) = " << std::hash<json> {}(json(0)) << '\n'
               << "hash(0U) = " << std::hash<json> {}(json(0U)) << '\n'
+              << "hash(0.0) = " << std::hash<json> {}(json(0.0)) << '\n'
               << "hash(\"\") = " << std::hash<json> {}(json("")) << '\n'
               << "hash({}) = " << std::hash<json> {}(json::object()) << '\n'
               << "hash([]) = " << std::hash<json> {}(json::array()) << '\n'

docs/mkdocs/docs/examples/std_hash.output

@@ -1,8 +1,9 @@
 hash(null) = 2654435769
 hash(false) = 2654436030
-hash(0) = 2654436095
+hash(0) = 2654436221
-hash(0U) = 2654436156
+hash(0U) = 2654436221
-hash("") = 6142509191626859748
+hash(0.0) = 2654436221
+hash("") = 11160318156688833227
 hash({}) = 2654435832
 hash([]) = 2654435899
-hash({"hello": "world"}) = 4469488738203676328
+hash({"hello": "world"}) = 3701319991624763853

docs/mkdocs/docs/examples/with_t.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+#include <map>
+#include <nlohmann/json.hpp>
+
+// a JSON type that stores objects in a std::map (which keeps keys sorted)
+// instead of the default ordered associative container
+using sorted_json = nlohmann::json::with_object_t<std::map>;
+
+int main()
+{
+    sorted_json j;
+    j["c"] = 1;
+    j["a"] = 2;
+    j["b"] = 3;
+
+    // keys are sorted, because std::map is used to store the object
+    std::cout << j.dump() << std::endl;
+}

docs/mkdocs/docs/examples/with_t.output

@@ -0,0 +1 @@
+{"a":2,"b":3,"c":1}

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

@@ -131,6 +131,7 @@ The library maps CBOR types to JSON value types as follows:
 | Byte string            | binary          | 0x59       |
 | Byte string            | binary          | 0x5A       |
 | Byte string            | binary          | 0x5B       |
+| Byte string            | binary          | 0x5F       |
 | UTF-8 string           | string          | 0x60..0x77 |
 | UTF-8 string           | string          | 0x78       |
 | UTF-8 string           | string          | 0x79       |
@@ -156,6 +157,9 @@ The library maps CBOR types to JSON value types as follows:
 | Single-Precision Float | number_float    | 0xFA       |
 | Double-Precision Float | number_float    | 0xFB       |
 
+Indefinite-length UTF-8 strings (0x7F) and byte strings (0x5F) are supported. Each chunk must be a definite-length
+string of the same major type, as required by [RFC 8949, Section 3.2.3](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.2.3).
+
 !!! warning "Incomplete mapping"
 
     The mapping is **incomplete** in the sense that not all CBOR types can be converted to a JSON value. The following CBOR types are not supported and will yield parse errors:
@@ -168,9 +172,9 @@ The library maps CBOR types to JSON value types as follows:
 !!! warning "Negative integer overflow"
 
     CBOR negative integers (major type 1) are decoded as `-1 - n`. If the encoded magnitude `n` is too large for the
-    result to fit into `number_integer_t` (`std::int64_t` by default), parsing fails with a
+    result to fit into `number_integer_t` (`std::int64_t` by default), the result is stored as `number_float_t`, like
-    [`parse_error.112`](../../home/exceptions.md#jsonexceptionparse_error112) exception rather than overflowing
+    a too small integer in JSON text. For example, `-18446744073709551616` (`0x3B` followed by eight `0xFF` bytes) is
-    silently.
+    stored as `-1.8446744073709552e+19`.
 
 !!! warning "Object keys"
 

docs/mkdocs/docs/features/enum_conversion.md

@@ -58,6 +58,23 @@ assert(jPi.get<TaskState>() == TS_INVALID );
     --8<-- "examples/nlohmann_json_serialize_enum.output"
     ```
 
+## Maps with enum keys
+
+By default, maps with enum keys, such as `std::map<TaskState, std::string>`, are stored as arrays of `[key, value]`
+pairs, because JSON object keys must be strings. Define
+[`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md) before including the
+library to store them as objects, with the keys converted by the enum's `to_json()` function:
+
+```cpp
+std::map<TaskState, std::string> m = {{TS_STOPPED, "aa"}, {TS_COMPLETED, "bb"}};
+
+json j = m;
+// default:                                   [["stopped","aa"],["completed","bb"]]
+// with JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS: {"completed":"bb","stopped":"aa"}
+```
+
+Either form can be read back, with or without the macro.
+
 ## Notes
 
 Just as in [Arbitrary Type Conversions](arbitrary_types.md) above,

docs/mkdocs/docs/features/macros.md

@@ -23,6 +23,17 @@ This macro overrides [`#!cpp catch`](https://en.cppreference.com/w/cpp/language/
 
 See [full documentation of `JSON_CATCH_USER(exception)`](../api/macros/json_throw_user.md).
 
+## `JSON_DELETE_DEPRECATED_FUNCTIONS`
+
+When defined to `1`, all deprecated functions are declared as deleted instead of only being marked as deprecated, so
+code that still calls them no longer compiles. This way, you can find all calls that need to be replaced before version
+4.0.0 removes these functions.
+
+The macro can also be set with the CMake option
+[`JSON_DeleteDeprecatedFunctions`](../integration/cmake.md#json_deletedeprecatedfunctions) (`OFF` by default).
+
+See [full documentation of `JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md).
+
 ## `JSON_DIAGNOSTICS`
 
 This macro enables extended diagnostics for exception messages. Possible values are `1` to enable or `0` to disable
@@ -86,7 +97,8 @@ See [full documentation of `JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json
 ## `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`
 
 When defined to `1`, a JSON value can no longer be created from a one-element `std::tuple` holding a reference to a JSON
-value, such as the result of `std::forward_as_tuple(j)`. This lets `std::tuple` convert such tuples element-wise.
+value, such as the result of `std::forward_as_tuple(j)`. This lets `std::tuple` convert such tuples element-wise. This
+is planned to become the default in version 4.0.0.
 
 See [full documentation of `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md).
 
@@ -198,6 +210,13 @@ default.
 
 See [full documentation of `JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md).
 
+## `JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`
+
+When defined to `1`, maps with enum keys (e.g., `std::map<E, T>`) are stored as objects, using the enum's conversion for
+the keys, instead of arrays of `[key, value]` pairs. It is switched off (`0`) by default.
+
+See [full documentation of `JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md).
+
 ## `JSON_USE_SIMDUTF`
 
 When defined, UTF-8 validation of JSON strings read from contiguous byte input is delegated to the

docs/mkdocs/docs/features/namespace.md

@@ -21,6 +21,8 @@ The complete default namespace name is derived as follows:
     - [`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md) defined non-zero appends `_psp`.
     - [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md) defined non-zero appends `_snul`.
     - [`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md) defined non-zero appends `_sbu8`.
+    - [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md) defined non-zero
+      appends `_ekmo`.
 - 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/home/exceptions.md

@@ -331,9 +331,6 @@ An unexpected byte was read in a [binary format](../features/binary_formats/inde
     [json.exception.parse_error.112] parse error at byte 15: syntax error while parsing BSON binary: byte array length cannot be negative, is -1
     ```
     ```
-    [json.exception.parse_error.112] parse error at byte 9: syntax error while parsing CBOR value: negative integer overflow
-    ```
-    ```
     [json.exception.parse_error.112] parse error at byte 5: syntax error while parsing BSON document: document size 6 does not match the number of bytes read (5)
     ```
 
@@ -599,6 +596,9 @@ During implicit or explicit value conversion, the JSON type must be compatible w
     [json.exception.type_error.302] type must be string, but is object
     ```
 
+This exception is also thrown with [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md)
+if a key of a map with enum keys is not converted to a string, for instance, because the enum is stored as an integer.
+
 ### json.exception.type_error.303
 
 To retrieve a reference to a value stored in a `basic_json` object with `get_ref`, the type of the reference must match the value type. For instance, for a JSON array, the `ReferenceType` must be `array_t &`.
@@ -791,6 +791,33 @@ The dynamic type of the object cannot be represented in the requested serializat
 
     Encapsulate the JSON value in an object. That is, instead of serializing `#!json true`, serialize `#!json {"value": true}`
 
+### json.exception.type_error.318
+
+With [`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md), a map with enum
+keys is stored as an object. This exception is thrown if two of its keys are converted to the same string, so one of the
+entries would be lost. This happens, for instance, if [`NLOHMANN_JSON_SERIALIZE_ENUM`](../api/macros/nlohmann_json_serialize_enum.md)
+does not list an enumerator and it is therefore converted like the first listed one.
+
+!!! failure "Example message"
+
+    ```
+    [json.exception.type_error.318] duplicate object key 'red'
+    ```
+
+### json.exception.type_error.321
+
+A discarded value (one created by [`parse()`](../api/basic_json/parse.md) with a callback that returns `false` for the
+value, or by default-constructing a [`basic_json`](../api/basic_json/index.md) with
+[`value_t::discarded`](../api/basic_json/value_t.md)) was passed to a binary serialization function, either directly or
+nested in an array or object. There is no way to represent a discarded value in CBOR, MessagePack, UBJSON, BJData, or BSON.
+
+!!! failure "Example message"
+
+    Serializing `#!json [1, 2]` to CBOR, where the second element was discarded by a parser callback:
+    ```
+    [json.exception.type_error.321] cannot serialize discarded value to CBOR
+    ```
+
 ## Out of range
 
 This exception is thrown in case a library function is called on an input parameter that exceeds the expected range, for instance, in the case of array indices or nonexisting object keys.
@@ -863,13 +890,18 @@ The JSON Patch operations 'remove' and 'add' cannot be applied to the root eleme
 
 ### json.exception.out_of_range.406
 
-A parsed number could not be stored as without changing it to NaN or INF.
+A parsed number could not be stored without changing it to NaN or INF. For the binary formats, this happens when a
+finite floating-point number does not fit into [`number_float_t`](../api/basic_json/number_float_t.md), for example a
+double-precision number when `number_float_t` is `#!cpp float`.
 
-!!! failure "Example message"
+!!! failure "Example messages"
 
     ```
     number overflow parsing '10E1000'
     ```
+    ```
+    [json.exception.out_of_range.406] syntax error while parsing CBOR value: number overflow
+    ```
 
 ### json.exception.out_of_range.407
 

docs/mkdocs/docs/integration/cmake.md

@@ -126,12 +126,18 @@ automatically download a release as a dependency at configure time.
 
 ### `JSON_BuildTests`
 
-Build the unit tests when [`BUILD_TESTING`](https://cmake.org/cmake/help/latest/command/enable_testing.html) is enabled. This option is `ON` by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.
+Build the unit tests when [`BUILD_TESTING`](https://cmake.org/cmake/help/latest/command/enable_testing.html) is enabled. This option is `ON` by default if the library's CMake project is the top project and the `tests` directory exists (the release archive `json.tar.xz` does not contain it). That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.
 
 ### `JSON_CI`
 
 Enable CI build targets. The exact targets are used during the several CI steps and are subject to change without notice. This option is `OFF` by default.
 
+### `JSON_DeleteDeprecatedFunctions`
+
+Delete the deprecated functions instead of only deprecating them by defining the macro
+[`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md). This option is `OFF` by
+default.
+
 ### `JSON_Diagnostics`
 
 Enable [extended diagnostic messages](../home/exceptions.md#extended-diagnostic-messages) by defining macro [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md). This option is `OFF` by default.

docs/mkdocs/docs/integration/migration_guide.md

@@ -14,6 +14,13 @@ deprecations are annotated with
 [`HEDLEY_DEPRECATED_FOR`](https://nemequ.github.io/hedley/api-reference.html#HEDLEY_DEPRECATED_FOR) to report which
 function to use instead.
 
+!!! tip "Find all calls of deprecated functions"
+
+    Define [`JSON_DELETE_DEPRECATED_FUNCTIONS`](../api/macros/json_delete_deprecated_functions.md) to `1` (or set the
+    CMake option [`JSON_DeleteDeprecatedFunctions`](cmake.md#json_deletedeprecatedfunctions)) to delete all deprecated
+    functions. Every remaining call then fails to compile, even if deprecation warnings are disabled, so your code is
+    ready for version 4.0.0 once it compiles with the macro.
+
 ### Parsing
 
 - Function `friend std::istream& operator<<(basic_json&, std::istream&)` is deprecated since 3.0.0. Please use
@@ -41,8 +48,10 @@ function to use instead.
   [`from_ubjson`](../api/basic_json/from_ubjson.md), and [`from_bson`](../api/basic_json/from_bson.md)) via initializer
   lists is deprecated since 3.8.0. Instead, pass two iterators; for instance, call `from_cbor(ptr, ptr+len)` instead of
   `from_cbor({ptr, len})`. Likewise, passing a pointer and a length as two separate arguments to `from_cbor`,
-  `from_msgpack`, `from_ubjson`, and `from_bson` is deprecated since 3.8.0; call `from_cbor(ptr, ptr+len)` instead of
+  `from_msgpack`, `from_ubjson`, and `from_bson` is deprecated since 3.8.0, and to
-  `from_cbor(ptr, len)`.
+  [`from_bjdata`](../api/basic_json/from_bjdata.md) and [`from_bon8`](../api/basic_json/from_bon8.md) since 3.13.0; call
+  `from_cbor(ptr, ptr+len)` instead of `from_cbor(ptr, len)`. These overloads will not be removed in version 4.0.0, but
+  deleted, so a call like `from_cbor(ptr, len)` cannot compile and convert `len` to the `strict` parameter.
 
     === "Deprecated"
   

docs/mkdocs/mkdocs.yml

@@ -232,6 +232,7 @@ nav:
           - 'update': api/basic_json/update.md
           - 'value': api/basic_json/value.md
           - 'value_t': api/basic_json/value_t.md
+          - 'with_t': api/basic_json/with_t.md
       - byte_container_with_subtype:
           - 'Overview': api/byte_container_with_subtype/index.md
           - '(constructor)': api/byte_container_with_subtype/byte_container_with_subtype.md
@@ -292,6 +293,7 @@ nav:
           - 'JSON_BRACE_INIT_COPY_SEMANTICS': api/macros/json_brace_init_copy_semantics.md
           - 'JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER': api/macros/json_throw_user.md
           - 'JSON_DIAGNOSTICS': api/macros/json_diagnostics.md
+          - 'JSON_DELETE_DEPRECATED_FUNCTIONS': api/macros/json_delete_deprecated_functions.md
           - 'JSON_DIAGNOSTIC_POSITIONS': api/macros/json_diagnostic_positions.md
           - 'JSON_DISABLE_ENUM_SERIALIZATION': api/macros/json_disable_enum_serialization.md
           - 'JSON_DISABLE_TUPLE_REFERENCE_CONVERSION': api/macros/json_disable_tuple_reference_conversion.md
@@ -313,6 +315,7 @@ nav:
           - '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
+          - 'JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS': api/macros/json_use_objects_for_enum_keyed_maps.md
           - 'JSON_USE_SIMDUTF': api/macros/json_use_simdutf.md
           - 'NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_derived_type.md
           - 'NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_type_intrusive.md

docs/mkdocs/requirements.txt

@@ -6,7 +6,7 @@ mkdocs-material==9.7.7                             # theme for mkdocs
 mkdocs-material-extensions==1.3.1                   # extensions
 mkdocs-minify-plugin==0.8.0                         # plugin "minify"
 mkdocs-redirects==1.2.3                             # plugin "redirects"
-mkdocs-htmlproofer-plugin==1.5.0                    # plugin "htmlproofer"
+mkdocs-htmlproofer-plugin==1.6.0                    # plugin "htmlproofer"
 mkdocs-llmstxt==0.5.0                               # plugin "llmstxt"
 
 PyYAML==6.0.3                                       # linter

docs/mkdocs/scripts/mermaid/package-lock.json

@@ -1454,9 +1454,9 @@
       }
     },
     "node_modules/source-map-js": {
-      "version": "1.2.1",
+      "version": "1.2.2",
-      "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.1.tgz",
+      "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.2.tgz",
-      "integrity": "sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==",
+      "integrity": "sha512-KGj/8Y43x35aZVDtt+J4mK1hoLGHULMYfSkODJNQjNDC3oW1PqPoxMwo0pLUsWM/UEGzON/NxeHywEfNXNP3Vw==",
       "license": "BSD-3-Clause",
       "engines": {
         "node": ">=0.10.0"

include/nlohmann/detail/abi_macros.hpp

@@ -50,6 +50,10 @@
     #define JSON_STRICT_BINARY_UTF8 0
 #endif
 
+#ifndef JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+    #define JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -92,14 +96,20 @@
     #define NLOHMANN_JSON_ABI_TAG_STRICT_BINARY_UTF8
 #endif
 
+#if JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+    #define NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS _ekmo
+#else
+    #define NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS
+#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, d, e, f, g) json_abi ## a ## b ## c ## d ## e ## f ## g
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h) json_abi ## a ## b ## c ## d ## e ## f ## g ## h
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f, g) \
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f, g, h) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g)
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
@@ -109,7 +119,8 @@
             NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
             NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION,           \
             NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING,               \
-            NLOHMANN_JSON_ABI_TAG_STRICT_BINARY_UTF8)
+            NLOHMANN_JSON_ABI_TAG_STRICT_BINARY_UTF8,                \
+            NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

include/nlohmann/detail/conversions/from_json.hpp

@@ -172,7 +172,7 @@ inline void from_json(const BasicJsonType& j, EnumType& e)
           typename BasicJsonType::number_unsigned_t, underlying_type>::type;
     value_type val;
     get_arithmetic_value(j, val);
-    e = static_cast<EnumType>(static_cast<underlying_type>(val));
+    e = static_cast<EnumType>(bool_aware_static_cast<underlying_type>(val));
 }
 #endif  // JSON_DISABLE_ENUM_SERIALIZATION
 
@@ -530,11 +530,40 @@ void from_json_pair_array_to_map(const BasicJsonType& j, MapType& m)
     }
 }
 
+// read a map with enum keys from an object, using the enum's own from_json for
+// the keys (e.g., from NLOHMANN_JSON_SERIALIZE_ENUM); this is the form written
+// with JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+template<typename BasicJsonType, typename Map>
+inline bool from_json_enum_keyed_object(const BasicJsonType& j, Map& m, std::true_type /*key is enum*/)
+{
+    if (!j.is_object())
+    {
+        return false;
+    }
+    m.clear();
+    for (const auto& p : *j.template get_ptr<const typename BasicJsonType::object_t*>())
+    {
+        m.emplace(BasicJsonType(p.first).template get<typename Map::key_type>(), p.second.template get<typename Map::mapped_type>());
+    }
+    return true;
+}
+
+template<typename BasicJsonType, typename Map>
+inline bool from_json_enum_keyed_object(const BasicJsonType& /*j*/, Map& /*m*/, std::false_type /*key is enum*/)
+{
+    return false;
+}
+
 template < typename BasicJsonType, typename Key, typename Value, typename Compare, typename Allocator,
            typename = enable_if_t < !std::is_constructible <
                                         typename BasicJsonType::string_t, Key >::value >>
 void from_json(const BasicJsonType& j, std::map<Key, Value, Compare, Allocator>& m)
 {
+    // NOLINTNEXTLINE(modernize-type-traits) we use C++11
+    if (from_json_enum_keyed_object(j, m, std::is_enum<Key> {}))
+    {
+        return;
+    }
     from_json_pair_array_to_map(j, m);
 }
 
@@ -543,6 +572,11 @@ template < typename BasicJsonType, typename Key, typename Value, typename Hash,
                                         typename BasicJsonType::string_t, Key >::value >>
 void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Hash, KeyEqual, Allocator>& m)
 {
+    // NOLINTNEXTLINE(modernize-type-traits) we use C++11
+    if (from_json_enum_keyed_object(j, m, std::is_enum<Key> {}))
+    {
+        return;
+    }
     from_json_pair_array_to_map(j, m);
 }
 

include/nlohmann/detail/conversions/to_chars.hpp

@@ -308,8 +308,8 @@ boundaries compute_boundaries(FloatType value)
 //
 //      -e <= 60   or   e >= -60 := alpha
 
-constexpr int kAlpha = -60;
+JSON_INLINE_VARIABLE constexpr int kAlpha = -60;
-constexpr int kGamma = -32;
+JSON_INLINE_VARIABLE constexpr int kGamma = -32;
 
 struct cached_power // c = f * 2^e ~= 10^k
 {

include/nlohmann/detail/conversions/to_json.hpp

@@ -13,7 +13,6 @@
     #include <optional> // optional
 #endif
 
-#include <algorithm> // copy
 #include <iterator> // begin, end
 #include <memory> // allocator_traits
 #include <string> //  basic_string, char_traits
@@ -23,6 +22,7 @@
 #include <valarray> // valarray
 #include <vector> // vector
 
+#include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/iterators/iteration_proxy.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/meta/std_fs.hpp>
@@ -38,10 +38,14 @@ namespace detail
 //////////////////
 
 /*
- * Note all external_constructor<>::construct functions need to call
+ * Note all external_constructor<>::construct functions need to store the new
- * j.m_data.m_value.destroy(j.m_data.m_type) to avoid a memory leak in case j contains an
+ * value with j.replace_value(), which destroys the old one to avoid a memory
- * allocated value (e.g., a string). See bug issue
+ * leak in case j contains an allocated value (e.g., a string). See bug issue
  * https://github.com/nlohmann/json/issues/2865 for more information.
+ *
+ * A value that has to be allocated is created before the old one is destroyed:
+ * were it the other way around, an exception while creating the new value would
+ * leave j with the type of the new value, but the pointer to the destroyed old one.
  */
 
 template<value_t> struct external_constructor;
@@ -52,10 +56,7 @@ struct external_constructor<value_t::boolean>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::boolean_t b) noexcept
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        j.replace_value(value_t::boolean, b);
-        j.m_data.m_type = value_t::boolean;
-        j.m_data.m_value = b;
-        j.assert_invariant();
     }
 };
 
@@ -65,19 +66,15 @@ struct external_constructor<value_t::string>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, const typename BasicJsonType::string_t& s)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(s);
-        j.m_data.m_type = value_t::string;
+        j.replace_value(value_t::string, value);
-        j.m_data.m_value = s;
-        j.assert_invariant();
     }
 
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::string_t&& s)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(std::move(s));
-        j.m_data.m_type = value_t::string;
+        j.replace_value(value_t::string, value);
-        j.m_data.m_value = std::move(s);
-        j.assert_invariant();
     }
 
     template < typename BasicJsonType, typename CompatibleStringType,
@@ -85,10 +82,8 @@ struct external_constructor<value_t::string>
                              int > = 0 >
     static void construct(BasicJsonType& j, const CompatibleStringType& str)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(j.template create<typename BasicJsonType::string_t>(str));
-        j.m_data.m_type = value_t::string;
+        j.replace_value(value_t::string, value);
-        j.m_data.m_value.string = j.template create<typename BasicJsonType::string_t>(str);
-        j.assert_invariant();
     }
 };
 
@@ -98,19 +93,15 @@ struct external_constructor<value_t::binary>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, const typename BasicJsonType::binary_t& b)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(b);
-        j.m_data.m_type = value_t::binary;
+        j.replace_value(value_t::binary, value);
-        j.m_data.m_value = typename BasicJsonType::binary_t(b);
-        j.assert_invariant();
     }
 
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::binary_t&& b)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(std::move(b));
-        j.m_data.m_type = value_t::binary;
+        j.replace_value(value_t::binary, value);
-        j.m_data.m_value = typename BasicJsonType::binary_t(std::move(b));
-        j.assert_invariant();
     }
 };
 
@@ -120,10 +111,7 @@ struct external_constructor<value_t::number_float>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::number_float_t val) noexcept
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        j.replace_value(value_t::number_float, val);
-        j.m_data.m_type = value_t::number_float;
-        j.m_data.m_value = val;
-        j.assert_invariant();
     }
 };
 
@@ -133,10 +121,7 @@ struct external_constructor<value_t::number_unsigned>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::number_unsigned_t val) noexcept
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        j.replace_value(value_t::number_unsigned, val);
-        j.m_data.m_type = value_t::number_unsigned;
-        j.m_data.m_value = val;
-        j.assert_invariant();
     }
 };
 
@@ -146,10 +131,7 @@ struct external_constructor<value_t::number_integer>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::number_integer_t val) noexcept
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        j.replace_value(value_t::number_integer, val);
-        j.m_data.m_type = value_t::number_integer;
-        j.m_data.m_value = val;
-        j.assert_invariant();
     }
 };
 
@@ -159,21 +141,15 @@ struct external_constructor<value_t::array>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, const typename BasicJsonType::array_t& arr)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(arr);
-        j.m_data.m_type = value_t::array;
+        j.replace_value(value_t::array, value);
-        j.m_data.m_value = arr;
-        j.set_parents();
-        j.assert_invariant();
     }
 
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::array_t&& arr)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(std::move(arr));
-        j.m_data.m_type = value_t::array;
+        j.replace_value(value_t::array, value);
-        j.m_data.m_value = std::move(arr);
-        j.set_parents();
-        j.assert_invariant();
     }
 
     template < typename BasicJsonType, typename CompatibleArrayType,
@@ -187,39 +163,23 @@ struct external_constructor<value_t::array>
         using std::begin;
         using std::end;
 
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(j.template create<typename BasicJsonType::array_t>(begin(arr), end(arr)));
-        j.m_data.m_type = value_t::array;
+        j.replace_value(value_t::array, value);
-        j.m_data.m_value.array = j.template create<typename BasicJsonType::array_t>(begin(arr), end(arr));
-        j.set_parents();
-        j.assert_invariant();
     }
 
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, const std::vector<bool>& arr)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(j.template create<typename BasicJsonType::array_t>(arr.begin(), arr.end()));
-        j.m_data.m_type = value_t::array;
+        j.replace_value(value_t::array, value);
-        j.m_data.m_value = value_t::array;
-        j.m_data.m_value.array->reserve(arr.size());
-        for (const bool x : arr)
-        {
-            j.m_data.m_value.array->push_back(x);
-            j.set_parent(j.m_data.m_value.array->back());
-        }
-        j.assert_invariant();
     }
 
     template<typename BasicJsonType, typename T,
              enable_if_t<std::is_convertible<T, BasicJsonType>::value, int> = 0>
     static void construct(BasicJsonType& j, const std::valarray<T>& arr)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(j.template create<typename BasicJsonType::array_t>(std::begin(arr), std::end(arr)));
-        j.m_data.m_type = value_t::array;
+        j.replace_value(value_t::array, value);
-        j.m_data.m_value = value_t::array;
-        j.m_data.m_value.array->resize(arr.size());
-        std::copy(std::begin(arr), std::end(arr), j.m_data.m_value.array->begin());
-        j.set_parents();
-        j.assert_invariant();
     }
 
 #if JSON_HAS_RANGE_VIEW_CONVERSION
@@ -227,18 +187,15 @@ struct external_constructor<value_t::array>
              enable_if_t<is_compatible_range_view<std::remove_cvref_t<CompatibleArrayType>>::value, int> = 0>
     static void construct(BasicJsonType& j, CompatibleArrayType && arr)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        // no range constructor: a view's begin() and end() may have different
-        j.m_data.m_type = value_t::array;
+        // types, and the view may only be iterable once
-        j.m_data.m_value = value_t::array;
+        typename BasicJsonType::array_t elements;
         for (auto&& x : std::forward<CompatibleArrayType>(arr))
         {
-            j.m_data.m_value.array->push_back(x);
+            elements.push_back(x);
         }
-        // set the parents only once all elements are in place: a push_back
+        const typename BasicJsonType::json_value value(std::move(elements));
-        // that reallocates moves the earlier elements, which does not keep
+        j.replace_value(value_t::array, value);
-        // their parent pointers
-        j.set_parents();
-        j.assert_invariant();
     }
 #endif
 };
@@ -249,21 +206,15 @@ struct external_constructor<value_t::object>
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, const typename BasicJsonType::object_t& obj)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(obj);
-        j.m_data.m_type = value_t::object;
+        j.replace_value(value_t::object, value);
-        j.m_data.m_value = obj;
-        j.set_parents();
-        j.assert_invariant();
     }
 
     template<typename BasicJsonType>
     static void construct(BasicJsonType& j, typename BasicJsonType::object_t&& obj)
     {
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(std::move(obj));
-        j.m_data.m_type = value_t::object;
+        j.replace_value(value_t::object, value);
-        j.m_data.m_value = std::move(obj);
-        j.set_parents();
-        j.assert_invariant();
     }
 
     template < typename BasicJsonType, typename CompatibleObjectType,
@@ -273,11 +224,8 @@ struct external_constructor<value_t::object>
         using std::begin;
         using std::end;
 
-        j.m_data.m_value.destroy(j.m_data.m_type);
+        const typename BasicJsonType::json_value value(j.template create<typename BasicJsonType::object_t>(begin(obj), end(obj)));
-        j.m_data.m_type = value_t::object;
+        j.replace_value(value_t::object, value);
-        j.m_data.m_value.object = j.template create<typename BasicJsonType::object_t>(begin(obj), end(obj));
-        j.set_parents();
-        j.assert_invariant();
     }
 };
 
@@ -286,9 +234,20 @@ struct external_constructor<value_t::object>
 /////////////
 
 #ifdef JSON_HAS_CPP_17
+// whether storing the value of a std::optional<T> cannot throw; MSVC 2017
+// evaluates std::is_nothrow_assignable as true even if T's to_json throws, so
+// the exception would call std::terminate (#5642)
+#if defined(_MSC_VER) && !defined(__clang__) && _MSC_VER < 1920
+    template<typename BasicJsonType, typename T>
+    using is_nothrow_optional_to_json = std::false_type;
+#else
+    template<typename BasicJsonType, typename T>
+    using is_nothrow_optional_to_json = std::is_nothrow_assignable<BasicJsonType&, const T&>;
+#endif
+
 template<typename BasicJsonType, typename T,
          enable_if_t<std::is_constructible<BasicJsonType, T>::value, int> = 0>
-void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept(std::is_nothrow_assignable<BasicJsonType&, const T&>::value)
+void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept(is_nothrow_optional_to_json<BasicJsonType, T>::value)
 {
     if (opt.has_value())
     {
@@ -364,7 +323,7 @@ inline void to_json(BasicJsonType& j, EnumType e) noexcept
 {
     using underlying_type = typename std::underlying_type<EnumType>::type;
     static constexpr value_t integral_value_t = std::is_unsigned<underlying_type>::value ? value_t::number_unsigned : value_t::number_integer;
-    external_constructor<integral_value_t>::construct(j, static_cast<underlying_type>(e));
+    external_constructor<integral_value_t>::construct(j, bool_aware_static_cast<underlying_type>(e));
 }
 #endif  // JSON_DISABLE_ENUM_SERIALIZATION
 
@@ -384,6 +343,9 @@ template < typename BasicJsonType, typename CompatibleArrayType,
                          !is_basic_json<CompatibleArrayType>::value
 #if JSON_HAS_RANGE_VIEW_CONVERSION
     && !is_compatible_range_view<CompatibleArrayType>::value
+#endif
+#if JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+    && !is_enum_keyed_map<CompatibleArrayType>::value
 #endif
                          ,
                          int > = 0 >
@@ -438,6 +400,33 @@ inline void to_json(BasicJsonType& j, const CompatibleObjectType& obj)
     external_constructor<value_t::object>::construct(j, obj);
 }
 
+#if JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+// store a map with enum keys as an object, using the enum's own to_json for the
+// keys (e.g., from NLOHMANN_JSON_SERIALIZE_ENUM); without the macro, such maps
+// are stored as arrays of [key, value] pairs
+template < typename BasicJsonType, typename EnumKeyedMap,
+           enable_if_t < is_enum_keyed_map<EnumKeyedMap>::value&& !is_basic_json<EnumKeyedMap>::value, int > = 0 >
+inline void to_json(BasicJsonType& j, const EnumKeyedMap& map)
+{
+    typename BasicJsonType::object_t obj;
+    for (const auto& p : map)
+    {
+        BasicJsonType key = p.first;
+        if (JSON_HEDLEY_UNLIKELY(!key.is_string()))
+        {
+            JSON_THROW(type_error::create(302, concat("type must be string, but is ", key.type_name()), &key));
+        }
+
+        auto& key_string = *key.template get_ptr<typename BasicJsonType::string_t*>();
+        if (JSON_HEDLEY_UNLIKELY(!obj.emplace(key_string, BasicJsonType(p.second)).second))
+        {
+            JSON_THROW(type_error::create(318, concat("duplicate object key '", key_string, "'"), &key));
+        }
+    }
+    external_constructor<value_t::object>::construct(j, std::move(obj));
+}
+#endif
+
 template<typename BasicJsonType>
 inline void to_json(BasicJsonType& j, typename BasicJsonType::object_t&& obj)
 {

include/nlohmann/detail/hash.hpp

@@ -35,8 +35,10 @@ std::size_t hash_iteratively(const BasicJsonType& j);
 @brief hash a JSON value
 
 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
+type of the JSON value is taken into account, so null, false, and numbers may
-null, 0, 0U, and false, etc.
+hash differently from each other, but any two numbers that compare equal
+under operator== hash equally regardless of which of number_integer,
+number_unsigned, or number_float actually holds the value.
 
 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
@@ -55,8 +57,6 @@ template<typename BasicJsonType>
 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;
-    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
     using number_float_t = typename BasicJsonType::number_float_t;
 
     const auto type = static_cast<std::size_t>(j.type());
@@ -113,21 +113,24 @@ std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)
         }
 
         case BasicJsonType::value_t::number_integer:
-        {
-            const auto h = std::hash<number_integer_t> {}(j.template get<number_integer_t>());
-            return combine(type, h);
-        }
-
         case BasicJsonType::value_t::number_unsigned:
-        {
-            const auto h = std::hash<number_unsigned_t> {}(j.template get<number_unsigned_t>());
-            return combine(type, h);
-        }
-
         case BasicJsonType::value_t::number_float:
         {
-            const auto h = std::hash<number_float_t> {}(j.template get<number_float_t>());
+            // operator== compares numbers by their mathematical value across
-            return combine(type, h);
+            // number_integer, number_unsigned, and number_float, so equal
+            // numbers of different internal types (0, 0U, 0.0) must hash the
+            // same. Two equal numbers have the same value, which converts to
+            // the same number_float_t, so all numbers share one type tag and
+            // hash that converted value. Adding zero turns -0.0 (equal to 0)
+            // into 0.0, as std::hash need not map both to the same hash.
+            // The converse does not hold: converting a number_float_t value
+            // to an integer type is lossy, so the result can hash
+            // differently, and unequal numbers that convert to the same
+            // number_float_t (e.g., 2^53 and 2^53 + 1) share a hash.
+            const auto number_type = static_cast<std::size_t>(BasicJsonType::value_t::number_float);
+            const auto value = j.template get<number_float_t>() + static_cast<number_float_t>(0);
+            const auto h = std::hash<number_float_t> {}(value);
+            return combine(number_type, h);
         }
 
         case BasicJsonType::value_t::binary:

include/nlohmann/detail/input/lexer.hpp

@@ -2021,6 +2021,39 @@ scan_number_done:
         // read the next character and ignore whitespace
         skip_whitespace();
 
+        return scan_after_whitespace();
+    }
+
+    /*!
+    @brief scan the next token when the caller expects a separator (':' or
+           ',') most of the time
+
+    After an object key the next token is almost always ':', after a value
+    inside an object or array almost always ','. Testing for that character
+    first is a compare and a well-predicted branch, where the switch in
+    scan_after_whitespace() is an indirect jump through a table. Anything else
+    goes through the switch, so the result is the same as scan()'s.
+
+    May only be called after scan() has run once (the BOM check is skipped).
+    */
+    token_type scan_expecting(token_type expected_type)
+    {
+        JSON_ASSERT(expected_type == token_type::name_separator || expected_type == token_type::value_separator);
+        JSON_ASSERT(position.chars_read_total > 0);
+        const char_int_type expected_char = static_cast<unsigned char>((expected_type == token_type::name_separator) ? ':' : ',');
+        skip_whitespace();
+        if (JSON_HEDLEY_LIKELY(current == expected_char))
+        {
+            return expected_type;
+        }
+        return scan_after_whitespace();
+    }
+
+  private:
+    /// the part of scan() after the leading whitespace: skip comments and
+    /// scan the token that starts with current
+    token_type scan_after_whitespace()
+    {
         // ignore comments
         while (ignore_comments && current == '/')
         {
@@ -2100,7 +2133,6 @@ scan_number_done:
         }
     }
 
-  private:
     /// input adapter
     InputAdapterType ia;
 

include/nlohmann/detail/input/parser.hpp

@@ -260,7 +260,7 @@ class parser
                         }
 
                         // parse separator (:)
-                        if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
+                        if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                         {
                             return sax->parse_error(m_lexer.get_position(),
                                                     m_lexer.get_token_string(),
@@ -423,7 +423,7 @@ class parser
             {
                 // comma -> next value
                 // or end of array (ignore_trailing_commas = true)
-                if (get_token() == token_type::value_separator)
+                if (get_token_expecting(token_type::value_separator))
                 {
                     // parse a new value
                     get_token();
@@ -463,7 +463,7 @@ class parser
 
             // comma -> next value
             // or end of object (ignore_trailing_commas = true)
-            if (get_token() == token_type::value_separator)
+            if (get_token_expecting(token_type::value_separator))
             {
                 get_token();
 
@@ -484,7 +484,7 @@ class parser
                     }
 
                     // parse separator (:)
-                    if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
+                    if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                     {
                         return sax->parse_error(m_lexer.get_position(),
                                                 m_lexer.get_token_string(),
@@ -528,6 +528,13 @@ class parser
         return last_token = m_lexer.scan();
     }
 
+    /// get next token from lexer; true if it is the separator @a expected_type
+    /// (name_separator or value_separator), which it usually is
+    bool get_token_expecting(token_type expected_type)
+    {
+        return (last_token = m_lexer.scan_expecting(expected_type)) == expected_type;
+    }
+
     std::string exception_message(const token_type expected, const std::string& context)
     {
         std::string error_msg = "syntax error ";

include/nlohmann/detail/json_pointer.hpp

@@ -81,9 +81,13 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_string_t/
     JSON_HEDLEY_DEPRECATED_FOR(3.11.0, to_string())
     operator string_t() const
+#if JSON_DELETE_DEPRECATED_FUNCTIONS
+        = delete;
+#else
     {
         return to_string();
     }
+#endif
 
 #ifndef JSON_NO_IO
     /// @brief write string representation of the JSON pointer to stream
@@ -1022,9 +1026,13 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_eq/
     JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer))
     bool operator==(const string_t& rhs) const
+#if JSON_DELETE_DEPRECATED_FUNCTIONS
+        = delete;
+#else
     {
         return *this == json_pointer(rhs);
     }
+#endif
 
     /// @brief 3-way compares two JSON pointers
     template<typename RefStringTypeRhs>
@@ -1102,18 +1110,26 @@ template<typename RefStringTypeLhs,
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
 inline bool operator==(const json_pointer<RefStringTypeLhs>& lhs,
                        const StringType& rhs)
+#if JSON_DELETE_DEPRECATED_FUNCTIONS
+    = delete;
+#else
 {
     return lhs == json_pointer<RefStringTypeLhs>(rhs);
 }
+#endif
 
 template<typename RefStringTypeRhs,
          typename StringType = typename json_pointer<RefStringTypeRhs>::string_t>
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator==(json_pointer, json_pointer))
 inline bool operator==(const StringType& lhs,
                        const json_pointer<RefStringTypeRhs>& rhs)
+#if JSON_DELETE_DEPRECATED_FUNCTIONS
+    = delete;
+#else
 {
     return json_pointer<RefStringTypeRhs>(lhs) == rhs;
 }
+#endif
 
 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator!=(const json_pointer<RefStringTypeLhs>& lhs,
@@ -1127,18 +1143,26 @@ template<typename RefStringTypeLhs,
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator!=(json_pointer, json_pointer))
 inline bool operator!=(const json_pointer<RefStringTypeLhs>& lhs,
                        const StringType& rhs)
+#if JSON_DELETE_DEPRECATED_FUNCTIONS
+    = delete;
+#else
 {
     return !(lhs == rhs);
 }
+#endif
 
 template<typename RefStringTypeRhs,
          typename StringType = typename json_pointer<RefStringTypeRhs>::string_t>
 JSON_HEDLEY_DEPRECATED_FOR(3.11.2, operator!=(json_pointer, json_pointer))
 inline bool operator!=(const StringType& lhs,
                        const json_pointer<RefStringTypeRhs>& rhs)
+#if JSON_DELETE_DEPRECATED_FUNCTIONS
+    = delete;
+#else
 {
     return !(lhs == rhs);
 }
+#endif
 
 template<typename RefStringTypeLhs, typename RefStringTypeRhs>
 inline bool operator<(const json_pointer<RefStringTypeLhs>& lhs,

include/nlohmann/detail/json_ref.hpp

@@ -34,6 +34,7 @@ class json_ref
 
     json_ref(std::initializer_list<json_ref> init)
         : owned_value(init)
+        , braced_list(true)
     {}
 
     template <
@@ -69,9 +70,17 @@ class json_ref
         return &** this;
     }
 
+    /// whether the value was written as a braced list, such as {"key", 1},
+    /// rather than given as a value
+    bool is_braced_list() const noexcept
+    {
+        return braced_list;
+    }
+
   private:
     mutable value_type owned_value = nullptr;
     value_type const* value_ref = nullptr;
+    bool braced_list = false;
 };
 
 }  // namespace detail

include/nlohmann/detail/macro_scope.hpp

@@ -888,6 +888,10 @@
     #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif
 
+#ifndef JSON_DELETE_DEPRECATED_FUNCTIONS
+    #define JSON_DELETE_DEPRECATED_FUNCTIONS 0
+#endif
+
 #ifndef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
     #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
 #endif

include/nlohmann/detail/macro_unscope.hpp

@@ -43,6 +43,8 @@
     #undef JSON_PRECISE_STREAM_POSITION
     #undef JSON_STRICT_NUL_HANDLING
     #undef JSON_STRICT_BINARY_UTF8
+    #undef JSON_DELETE_DEPRECATED_FUNCTIONS
+    #undef JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
 #endif
 
 #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

include/nlohmann/detail/meta/type_traits.hpp

@@ -438,6 +438,30 @@ template<typename BasicJsonType, typename CompatibleObjectType>
 struct is_compatible_object_type
     : is_compatible_object_type_impl<BasicJsonType, CompatibleObjectType> {};
 
+template<typename T>
+using insert_result_t = decltype(std::declval<T&>().insert(std::declval<const value_type_t<T>&>()));
+
+template<typename T>
+using insert_result_second_t = decltype(std::declval<T&>().insert(std::declval<const value_type_t<T>&>()).second);
+
+// a map-like type (std::map, std::unordered_map, ...) whose keys are enums; see
+// JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+template<typename T, typename = void>
+struct is_enum_keyed_map : std::false_type {};
+
+template<typename T>
+struct is_enum_keyed_map <
+    T, enable_if_t < is_detected<mapped_type_t, T>::value&&
+    is_detected<key_type_t, T>::value >>
+{
+    // maps with non-unique keys (std::multimap, std::unordered_multimap, ...)
+    // are excluded, because an object cannot hold duplicate keys; they are
+    // detected by insert() returning an iterator instead of a pair<iterator, bool>
+    // NOLINTNEXTLINE(modernize-type-traits) we use C++11
+    static constexpr bool value = std::is_enum<typename T::key_type>::value &&
+                                  !(is_detected<insert_result_t, T>::value && !is_detected<insert_result_second_t, T>::value);
+};
+
 template<typename BasicJsonType, typename ConstructibleObjectType,
          typename = void>
 struct is_constructible_object_type_impl : std::false_type {};
@@ -882,6 +906,21 @@ T conditional_static_cast(U value)
     return value;
 }
 
+// like conditional_static_cast, but converts to bool by comparing with zero,
+// because MSVC 2015 warns about any conversion to bool (C4800), even with an
+// explicit cast; used for enums whose underlying type is bool
+template < typename T, typename U, enable_if_t < !std::is_same<T, bool>::value, int > = 0 >
+T bool_aware_static_cast(U value)
+{
+    return conditional_static_cast<T>(value);
+}
+
+template<typename T, typename U, enable_if_t<std::is_same<T, bool>::value, int> = 0>
+bool bool_aware_static_cast(U value)
+{
+    return value != U();
+}
+
 template<typename... Types>
 using all_integral = conjunction<std::is_integral<Types>...>;
 

include/nlohmann/detail/output/binary_writer.hpp

@@ -127,6 +127,7 @@ class binary_writer
     @throw type_error.316 if a string value or an object key is not valid
            UTF-8
     @throw type_error.317 if @a j is not an object
+    @throw type_error.321 if a value nested in @a j is discarded
     */
     void write_bson(const BasicJsonType& j)
     {
@@ -158,6 +159,7 @@ class binary_writer
     @param[in] j  JSON value to serialize
     @throw type_error.316 if a string value or an object key is not valid
            UTF-8
+    @throw type_error.321 if @a j or a value nested in it is discarded
     */
     void write_cbor(const BasicJsonType& j)
     {
@@ -322,7 +324,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                break;
+                throw_on_discarded(j, "CBOR");
         }
     }
 
@@ -382,6 +384,7 @@ class binary_writer
 
     /*!
     @param[in] j  JSON value to serialize
+    @throw type_error.321 if @a j or a value nested in it is discarded
     */
     void write_msgpack(const BasicJsonType& j)
     {
@@ -655,7 +658,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                break;
+                throw_on_discarded(j, "MessagePack");
         }
     }
 
@@ -668,6 +671,7 @@ class binary_writer
     @param[in] bjdata_version  which BJData version to use, default is draft2
     @throw type_error.316 if a string value or an object key is not valid
            UTF-8
+    @throw type_error.321 if @a j or a value nested in it is discarded
     */
     void write_ubjson(const BasicJsonType& j, const bool use_count,
                       const bool use_type, const bool add_prefix = true,
@@ -901,7 +905,7 @@ class binary_writer
 
             case value_t::discarded:
             default:
-                break;
+                throw_on_discarded(j, use_bjdata ? "BJData" : "UBJSON");
         }
     }
 
@@ -921,6 +925,17 @@ class binary_writer
     }
 
   private:
+    /*!
+    @brief throws because @a j is discarded and cannot be serialized
+    @throw type_error.321 always
+    */
+    JSON_HEDLEY_NO_RETURN static void throw_on_discarded(const BasicJsonType& j, const char* format_name)
+    {
+        static_cast<void>(j); // unused when JSON_NOEXCEPTION is defined
+        static_cast<void>(format_name);
+        JSON_THROW(type_error::create(321, concat("cannot serialize discarded value to ", format_name), &j));
+    }
+
     //////////
     // BSON //
     //////////
@@ -1172,6 +1187,7 @@ class binary_writer
            into a byte, before anything is written
     @throw type_error.316 if @a j is a string that is not valid UTF-8, before
            anything is written
+    @throw type_error.321 if @a j is discarded
     */
     std::size_t calc_bson_value_size(const BasicJsonType& j)
     {
@@ -1198,10 +1214,12 @@ class binary_writer
             case value_t::null:
                 return 0ul;
 
+            case value_t::discarded:
+                throw_on_discarded(j, "BSON");
+
             // LCOV_EXCL_START
             case value_t::object:
             case value_t::array:
-            case value_t::discarded:
             default:
                 JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert)
                 return 0ul;
@@ -1238,10 +1256,12 @@ class binary_writer
             case value_t::null:
                 return write_bson_null(name);
 
+            case value_t::discarded:
+                throw_on_discarded(j, "BSON");
+
             // LCOV_EXCL_START
             case value_t::object:
             case value_t::array:
-            case value_t::discarded:
             default:
                 JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert)
                 return;
@@ -1308,6 +1328,8 @@ class binary_writer
            byte, before anything is written
     @throw type_error.316 if a string value or a key is not valid UTF-8,
            before anything is written
+    @throw type_error.321 if a value nested in @a document is discarded,
+           before anything is written
     */
     std::size_t calc_bson_sizes(const BasicJsonType& document, std::vector<std::size_t>& nested_sizes)
     {

include/nlohmann/ordered_map.hpp

@@ -259,6 +259,9 @@ public:
 
         for (auto it = first; std::next(it, elements_affected) != Container::end(); ++it)
         {
+            // false positive: Infer's model of std::string keeps the buffer of a
+            // moved-from string, so it assumes a buffer is destroyed twice
+            // @infer-ignore USE_AFTER_DELETE
             it->~value_type(); // destroy but keep allocation
             new (&*it) value_type{std::move(*std::next(it, elements_affected))}; // "move" next element to it
         }

single_include/nlohmann/json_fwd.hpp

@@ -67,6 +67,10 @@
     #define JSON_STRICT_BINARY_UTF8 0
 #endif
 
+#ifndef JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+    #define JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -109,14 +113,20 @@
     #define NLOHMANN_JSON_ABI_TAG_STRICT_BINARY_UTF8
 #endif
 
+#if JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+    #define NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS _ekmo
+#else
+    #define NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS
+#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, d, e, f, g) json_abi ## a ## b ## c ## d ## e ## f ## g
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h) json_abi ## a ## b ## c ## d ## e ## f ## g ## h
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f, g) \
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f, g, h) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g)
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
@@ -126,7 +136,8 @@
             NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
             NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION,           \
             NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING,               \
-            NLOHMANN_JSON_ABI_TAG_STRICT_BINARY_UTF8)
+            NLOHMANN_JSON_ABI_TAG_STRICT_BINARY_UTF8,                \
+            NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

tests/CMakeLists.txt

@@ -8,6 +8,7 @@ set(JSON_SIMDUTF_VERSION 9.1.0 CACHE STRING "The simdutf version used by JSON_Te
 
 set(JSON_32bitTest     AUTO CACHE STRING "Enable the 32bit unit test (ON/OFF/AUTO/ONLY).")
 set(JSON_TestStandards "" CACHE STRING "The list of standards to test explicitly.")
+set(JSON_TestShard     "" CACHE STRING "Build only a part of the unit tests, given as <index>/<count> (e.g. 0/2), to split them across CI jobs with a time limit.")
 
 # using an env var, since this will also affect targets executing cmake (such as "ci_test_compiler_default")
 if (NOT "" STREQUAL "$ENV{JSON_FORCED_GLOBAL_COMPILE_OPTIONS}")
@@ -134,12 +135,17 @@ json_test_set_test_options(test-disabled_exceptions
         #$<$<CXX_COMPILER_ID:MSVC>:/EH>
 )
 
-# raise timeout of expensive Unicode test
-json_test_set_test_options(test-unicode4 TEST_PROPERTIES TIMEOUT 3000)
-
 # only the #972 regression test needs thirdparty/fifo_map on its include path
 json_test_set_test_options(test-regression1 LINK_LIBRARIES fifo_map_include)
 
+# GCC's false -Warray-bounds error with JSON_DIAGNOSTICS only shows up when optimizing (#5742).
+# -O3 makes the optimizer-driven warnings of the ci_test_gcc flag set (-Winline,
+# -Wsuggest-attribute=...) fire on the library's inline functions; they are not
+# what this test checks, so turn them off for it.
+json_test_set_test_options(test-diagnostics-optimized
+    COMPILE_OPTIONS $<$<CXX_COMPILER_ID:GNU>:-O3 -Werror=array-bounds -Wno-inline -Wno-suggest-attribute=pure -Wno-suggest-attribute=const>
+)
+
 #############################################################################
 # add unit tests
 #############################################################################
@@ -288,6 +294,33 @@ elseif(NOT json_32bit_test)
     list(FILTER files EXCLUDE REGEX src/unit-32bit.cpp)
 endif()
 
+# with JSON_TestShard=<index>/<count>, keep every <count>-th unit test file,
+# starting at <index> (the glob is sorted, so the split is stable)
+set(test_shard_index 0)
+if(NOT "${JSON_TestShard}" STREQUAL "")
+    if(NOT JSON_TestShard MATCHES "^([0-9]+)/([1-9][0-9]*)$")
+        message(FATAL_ERROR "JSON_TestShard must be <index>/<count>, e.g. 0/2, not '${JSON_TestShard}'.")
+    endif()
+    set(test_shard_index ${CMAKE_MATCH_1})
+    set(test_shard_count ${CMAKE_MATCH_2})
+    if(NOT test_shard_index LESS test_shard_count)
+        message(FATAL_ERROR "JSON_TestShard: the index must be less than the count, not '${JSON_TestShard}'.")
+    endif()
+    list(LENGTH files test_file_count)
+    set(shard_files "")
+    set(file_position 0)
+    foreach(file ${files})
+        math(EXPR file_shard "${file_position} % ${test_shard_count}")
+        if(file_shard EQUAL test_shard_index)
+            list(APPEND shard_files ${file})
+        endif()
+        math(EXPR file_position "${file_position} + 1")
+    endforeach()
+    set(files ${shard_files})
+    list(LENGTH files shard_file_count)
+    message(STATUS "Test shard ${JSON_TestShard}: ${shard_file_count} of ${test_file_count} unit test files")
+endif()
+
 foreach(file ${files})
     json_test_add_test_for(${file} MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force})
 endforeach()
@@ -305,6 +338,9 @@ if(json_32bit_test_only)
     return()
 endif()
 
+# the following variants of single test files are only built in the first shard
+if(test_shard_index EQUAL 0)
+
 # test legacy comparison of discarded values
 json_test_set_test_options(test-comparison_legacy
     COMPILE_DEFINITIONS JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1
@@ -332,6 +368,8 @@ json_test_add_test_for(src/unit-diagnostic-positions.cpp
     MAIN test_main CXX_STANDARDS ${test_cxx_standards} ${test_force}
 )
 
+endif()
+
 # *DO NOT* use json_test_set_test_options() below this line
 
 #############################################################################

tests/abi/config/default.cpp

@@ -48,6 +48,10 @@ TEST_CASE("default namespace")
         expected += "_sbu8";
 #endif
 
+#if JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+        expected += "_ekmo";
+#endif
+
         expected += "_v" STRINGIZE(NLOHMANN_JSON_VERSION_MAJOR);
         expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_MINOR);
         expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_PATCH) "::basic_json";

tests/abi/config/noversion.cpp

@@ -49,6 +49,10 @@ TEST_CASE("default namespace without version component")
         expected += "_sbu8";
 #endif
 
+#if JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
+        expected += "_ekmo";
+#endif
+
         expected += "::basic_json";
 
         // fallback for Clang

tests/fuzzing.md

@@ -3,6 +3,14 @@
 Each parser of the library (JSON, BJData, BON8, BSON, CBOR, MessagePack, and UBJSON) can be fuzz tested. Currently,
 [libFuzzer](https://llvm.org/docs/LibFuzzer.html) and [afl++](https://github.com/AFLplusplus/AFLplusplus) are supported.
 
+## What the fuzzers check
+
+Each fuzzer driver (`tests/src/fuzzer-parse_*.cpp`) parses its input twice: once with `allow_exceptions = false` and
+once with exceptions. Both calls must agree. Where parsing with exceptions fails, the call without exceptions must
+return a discarded value (or throw the same kind of non-parse error), and it must never throw a `parse_error`. Where
+parsing succeeds, both calls must return the same value. The drivers then serialize the value, parse the result back,
+and check that nothing was lost. The drivers check all of this with `assert`, so they refuse to build with `NDEBUG`.
+
 ## Corpus creation
 
 For most effective fuzzing, a [corpus](https://llvm.org/docs/LibFuzzer.html#corpus) should be provided. A corpus is a
@@ -54,6 +62,9 @@ Then pass the corpus directory as command-line argument (assuming it is located
 The fuzzer should be able to run indefinitely without crashing. In case of a crash, the tested input is dumped into
 a file starting with `crash-`.
 
+To also detect memory leaks, build with AddressSanitizer (`FUZZER_ENGINE="-fsanitize=fuzzer,address"`): libFuzzer then
+runs LeakSanitizer by default (`-detect_leaks=1`). LeakSanitizer is not available with Apple Clang on macOS.
+
 ## afl++
 
 To use afl++, you need to pass `-fsanitize=fuzzer` as `FUZZER_ENGINE`. It will be replaced by a `libAFLDriver.a` to
@@ -76,7 +87,9 @@ directory `out`.
 
 The library is further fuzz-tested 24/7 by Google's [OSS-Fuzz project](https://github.com/google/oss-fuzz). It uses
 the same `fuzzers` target as above and also relies on the `FUZZER_ENGINE` variable. See the used
-[build script](https://github.com/google/oss-fuzz/blob/master/projects/json/build.sh) for more information.
+[build script](https://github.com/google/oss-fuzz/blob/master/projects/json/build.sh) for more information. Its default
+`address` sanitizer includes LeakSanitizer, so OSS-Fuzz and the CIFuzz workflow (`.github/workflows/cifuzz.yml`) report
+memory leaks, too.
 
 In case the build at OSS-Fuzz fails, an issue will be created automatically.
 

tests/src/fuzzer-parse_bjdata.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = from_bjdata(data, allow_exceptions = false)
 - j1 = from_bjdata(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - vec2 = to_bjdata(j1, use_size = false, use_type = false)
 - vec3 = to_bjdata(j1, use_size = true, use_type = false)
 - vec4 = to_bjdata(j1, use_size = true, use_type = true)
@@ -59,6 +61,13 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 // 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)
@@ -69,11 +78,37 @@ static bool is_value_stable(const json& lhs, const json& rhs)
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    std::vector<uint8_t> const vec1(data, data + size);
+
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::from_bjdata(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
-        std::vector<uint8_t> const vec1(data, data + size);
         json const j1 = json::from_bjdata(vec1);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -107,14 +142,17 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::type_error&)
     {
         // type errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors may happen if provided sizes are excessive
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/fuzzer-parse_bon8.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = from_bon8(data, allow_exceptions = false)
 - j1 = from_bon8(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - vec = to_bon8(j1)
 - j2 = from_bon8(vec)
 - assert(to_bon8(j2) == vec)
@@ -34,6 +36,13 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 namespace
 {
 // the serialization of the value read from @a input, or the error message
@@ -61,11 +70,37 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
         assert(read_bon8(std::vector<uint8_t>(data, data + size)) == read_bon8(stream));
     }
 
+    std::vector<uint8_t> const vec1(data, data + size);
+
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::from_bon8(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
-        std::vector<uint8_t> const vec1(data, data + size);
         json const j1 = json::from_bon8(vec1);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -87,14 +122,17 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::type_error&)
     {
         // type errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors may happen if provided sizes are excessive
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/fuzzer-parse_bson.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = from_bson(data, allow_exceptions = false)
 - j1 = from_bson(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - vec = to_bson(j1)
 - j2 = from_bson(vec)
 - assert(to_bson(j2) == vec)
@@ -29,14 +31,47 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    std::vector<uint8_t> const vec1(data, data + size);
+
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::from_bson(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
-        std::vector<uint8_t> const vec1(data, data + size);
         json const j1 = json::from_bson(vec1);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -58,14 +93,17 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::type_error&)
     {
         // type errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/fuzzer-parse_cbor.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = from_cbor(data, allow_exceptions = false)
 - j1 = from_cbor(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - vec = to_cbor(j1)
 - j2 = from_cbor(vec)
 - assert(to_cbor(j2) == vec)
@@ -29,14 +31,47 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    std::vector<uint8_t> const vec1(data, data + size);
+
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::from_cbor(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
-        std::vector<uint8_t> const vec1(data, data + size);
         json const j1 = json::from_cbor(vec1);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -58,14 +93,17 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::type_error&)
     {
         // type errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/fuzzer-parse_json.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = parse(data, allow_exceptions = false)
 - j1 = parse(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - s1 = serialize(j1)
 - j2 = parse(s1)
 - s2 = serialize(j2)
@@ -30,13 +32,45 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::parse(data, data + size, nullptr, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
         json const j1 = json::parse(data, data + size);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -63,10 +97,12 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors may happen if provided sizes are excessive
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/fuzzer-parse_msgpack.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = from_msgpack(data, allow_exceptions = false)
 - j1 = from_msgpack(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - vec = to_msgpack(j1)
 - j2 = from_msgpack(vec)
 - assert(to_msgpack(j2) == vec)
@@ -29,14 +31,47 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    std::vector<uint8_t> const vec1(data, data + size);
+
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::from_msgpack(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
-        std::vector<uint8_t> const vec1(data, data + size);
         json const j1 = json::from_msgpack(vec1);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -58,14 +93,17 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::type_error&)
     {
         // type errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors may happen if provided sizes are excessive
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/fuzzer-parse_ubjson.cpp

@@ -10,7 +10,9 @@
 This file implements a parser test suitable for fuzz testing. Given a byte
 array data, it performs the following steps:
 
+- j0 = from_ubjson(data, allow_exceptions = false)
 - j1 = from_ubjson(data)
+- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
 - vec2 = to_ubjson(j1, use_size = false, use_type = false)
 - vec3 = to_ubjson(j1, use_size = true, use_type = false)
 - vec4 = to_ubjson(j1, use_size = true, use_type = true)
@@ -38,14 +40,47 @@ drivers.
 
 using json = nlohmann::json;
 
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
+
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    std::vector<uint8_t> const vec1(data, data + size);
+
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
+    bool noexcept_threw = false;
+    try
+    {
+        j_noexcept = json::from_ubjson(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
+    // whether step 1 succeeded; if not, the catch blocks below check that
+    // step 0 failed, too
+    bool parsed = false;
+
     try
     {
         // step 1: parse input
-        std::vector<uint8_t> const vec1(data, data + size);
         json const j1 = json::from_ubjson(vec1);
+        parsed = true;
+
+        // without exceptions, the same input must give the same value
+        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
 
         try
         {
@@ -77,14 +112,17 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     catch (const json::parse_error&)
     {
         // parse errors are ok, because input may be random bytes
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::type_error&)
     {
         // type errors can occur during parsing, too
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
     catch (const json::out_of_range&)
     {
         // out of range errors may happen if provided sizes are excessive
+        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
     }
 
     // return 0 - non-zero return values are reserved for future use

tests/src/test_utils.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <array> // array
 #include <cstdint> // uint8_t
 #include <cstddef> // size_t
 #include <fstream> // ifstream, ios
@@ -43,6 +44,33 @@ T next_integer_sample(T i, T last, T stride)
     return n < last ? n : last;
 }
 
+// UTF-8 continuation bytes in [lo, hi] that stand in for all of them in the
+// ill-formed UTF-8 tests. Both the lexer's range checks and the serializer's
+// decoder (detail::decode) only distinguish the classes 0x80..0x8F, 0x90..0x9F,
+// and 0xA0..0xBF, so the first and last byte of each class within [lo, hi]
+// exercise every behavior while a test sweeps another byte position through
+// all 256 values (#5418). Define JSON_TEST_UTF8_EXHAUSTIVE to get every byte.
+inline std::vector<int> utf8_continuation_bytes(int lo, int hi)
+{
+    std::vector<int> result;
+#ifdef JSON_TEST_UTF8_EXHAUSTIVE
+    for (int byte = lo; byte <= hi; ++byte)
+    {
+        result.push_back(byte);
+    }
+#else
+    static const std::array<int, 6> class_ends = {{0x80, 0x8F, 0x90, 0x9F, 0xA0, 0xBF}};
+    for (const int byte : class_ends)
+    {
+        if (lo <= byte && byte <= hi)
+        {
+            result.push_back(byte);
+        }
+    }
+#endif
+    return result;
+}
+
 inline std::vector<std::uint8_t> read_binary_file(const std::string& filename)
 {
     std::ifstream file(filename, std::ios::binary);

tests/src/unit-allocator.cpp

@@ -12,6 +12,11 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
+#include <valarray>
+#if JSON_HAS_RANGES
+    #include <ranges>
+#endif
+
 namespace
 {
 // special test case to check if memory is leaked if constructor throws
@@ -48,14 +53,7 @@ TEST_CASE("bad_alloc")
     SECTION("bad_alloc")
     {
         // create JSON type using the throwing allocator
-        using bad_json = nlohmann::basic_json<std::map,
+        using bad_json = nlohmann::json::with_allocator_t<bad_allocator>;
-              std::vector,
-              std::string,
-              bool,
-              std::int64_t,
-              std::uint64_t,
-              double,
-              bad_allocator>;
 
         // creating an object should throw
         CHECK_THROWS_AS(bad_json(bad_json::value_t::object), std::bad_alloc&);
@@ -129,14 +127,7 @@ void my_allocator_clean_up(T* p)
 TEST_CASE("controlled bad_alloc")
 {
     // create JSON type using the throwing allocator
-    using my_json = nlohmann::basic_json<std::map,
+    using my_json = nlohmann::json::with_allocator_t<my_allocator>;
-          std::vector,
-          std::string,
-          bool,
-          std::int64_t,
-          std::uint64_t,
-          double,
-          my_allocator>;
 
     SECTION("class json_value")
     {
@@ -521,6 +512,10 @@ struct countdown_allocator : std::allocator<T>
 
 TEST_CASE("converting a deeply nested value from another specialization fails cleanly (#5650)")
 {
+    // MSVC 2015's debug STL constructs the containers' debug proxies through
+    // the allocator in noexcept constructors, so a failing construction crashes
+    // the program there instead of throwing std::bad_alloc. Nothing to check.
+#if !(defined(_MSC_VER) && _MSC_VER < 1910 && defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
     using countdown_json = nlohmann::basic_json<std::map,
           std::vector,
           std::string,
@@ -558,6 +553,7 @@ TEST_CASE("converting a deeply nested value from another specialization fails cl
         }
     }
     CHECK(failures > 0);
+#endif
 }
 
 namespace
@@ -588,17 +584,265 @@ TEST_CASE("bad my_allocator::construct")
 {
     SECTION("my_allocator::construct doesn't forward")
     {
-        using bad_alloc_json = nlohmann::basic_json<std::map,
+        using bad_alloc_json = nlohmann::json::with_allocator_t<allocator_no_forward>;
-              std::vector,
-              std::string,
-              bool,
-              std::int64_t,
-              std::uint64_t,
-              double,
-              allocator_no_forward>;
 
         bad_alloc_json j;
         j["test"] = bad_alloc_json::array_t();
         j["test"].push_back("should not leak");
     }
 }
+
+namespace
+{
+std::size_t counting_allocator_allocations = 0;
+std::size_t counting_allocator_deallocations = 0;
+
+template<class T>
+struct counting_allocator : std::allocator<T>
+{
+    using std::allocator<T>::allocator;
+
+    T* allocate(std::size_t n)
+    {
+        ++counting_allocator_allocations;
+        return std::allocator<T>::allocate(n);
+    }
+
+    void deallocate(T* p, std::size_t n)
+    {
+        ++counting_allocator_deallocations;
+        std::allocator<T>::deallocate(p, n);
+    }
+
+    template <class U>
+    struct rebind
+    {
+        using other = counting_allocator<U>;
+    };
+};
+} // namespace
+
+TEST_CASE("destructor performs no allocation, only deallocation")
+{
+    // see https://github.com/nlohmann/json/issues/4842 and
+    // https://github.com/nlohmann/json/issues/5135: destroying nested
+    // arrays/objects used to allocate a temporary stack (first with
+    // std::allocator, later - after #4842 - with the provided allocator).
+    // Since that stack could itself throw bad_alloc from inside the
+    // noexcept destructor (#5135), destroy() no longer allocates anything:
+    // it only ever frees what is already there.
+    using counting_json = nlohmann::basic_json<std::map,
+          std::vector,
+          std::string,
+          bool,
+          std::int64_t,
+          std::uint64_t,
+          double,
+          counting_allocator>;
+
+    SECTION("array")
+    {
+        auto* j = new counting_json({1, {2, {3, 4}}, 5}); // NOLINT(cppcoreguidelines-owning-memory)
+        const auto allocations_before = counting_allocator_allocations;
+        const auto deallocations_before = counting_allocator_deallocations;
+        delete j; // NOLINT(cppcoreguidelines-owning-memory)
+        CHECK(counting_allocator_allocations == allocations_before);
+        CHECK(counting_allocator_deallocations > deallocations_before);
+    }
+
+    SECTION("object")
+    {
+        auto* j = new counting_json({{"a", {{"b", {1, 2}}}}, {"c", 3}}); // NOLINT(cppcoreguidelines-owning-memory)
+        const auto allocations_before = counting_allocator_allocations;
+        const auto deallocations_before = counting_allocator_deallocations;
+        delete j; // NOLINT(cppcoreguidelines-owning-memory)
+        CHECK(counting_allocator_allocations == allocations_before);
+        CHECK(counting_allocator_deallocations > deallocations_before);
+    }
+
+    SECTION("mixed tree of empty/non-empty arrays and objects")
+    {
+        auto* j = new counting_json( // NOLINT(cppcoreguidelines-owning-memory)
+        {
+            {"empty_obj", counting_json::object()},
+            {"empty_arr", counting_json::array()},
+            {"nested", {{"a", counting_json::array({1, 2, counting_json::object()})}, {"b", 3}}},
+            {"tail", counting_json::array({counting_json::array({1}), 2, counting_json::array({3})})}
+        });
+        const auto allocations_before = counting_allocator_allocations;
+        const auto deallocations_before = counting_allocator_deallocations;
+        delete j; // NOLINT(cppcoreguidelines-owning-memory)
+        CHECK(counting_allocator_allocations == allocations_before);
+        CHECK(counting_allocator_deallocations > deallocations_before);
+    }
+}
+
+// the no-exceptions CI job skips every CHECK_THROWS_AS, which would leave
+// next_construct_fails set for the next allocation outside a check
+#if !defined(JSON_NOEXCEPTION)
+TEST_CASE("a failed allocation leaves the value unchanged")
+{
+    // create JSON type using the throwing allocator
+    using my_json = nlohmann::basic_json<std::map,
+          std::vector,
+          std::string,
+          bool,
+          std::int64_t,
+          std::uint64_t,
+          double,
+          my_allocator>;
+
+    // Each of these creates a string, array, object, or binary value. The
+    // value must be created before the type is changed: otherwise, a failed
+    // creation left a value of the new type without anything behind it (an
+    // assertion in its destructor, a null pointer everywhere else) or, when
+    // an old value was destroyed first, with a pointer to that destroyed one.
+
+    SECTION("creating a binary value")
+    {
+        const std::vector<std::uint8_t> bytes = {1, 2, 3};
+        my_json _;
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(_ = my_json::binary(bytes), std::bad_alloc&);
+        next_construct_fails = true;
+        CHECK_THROWS_AS(_ = my_json::binary(bytes, 42), std::bad_alloc&);
+        next_construct_fails = true;
+        CHECK_THROWS_AS(_ = my_json::binary(std::vector<std::uint8_t>(bytes)), std::bad_alloc&);
+        next_construct_fails = true;
+        CHECK_THROWS_AS(_ = my_json::binary(std::vector<std::uint8_t>(bytes), 42), std::bad_alloc&);
+        next_construct_fails = false;
+    }
+
+    SECTION("turning a null value into an array or object")
+    {
+        my_json j;
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j[0], std::bad_alloc&);
+        CHECK(j.is_null());
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j["key"], std::bad_alloc&);
+        CHECK(j.is_null());
+
+#ifdef JSON_HAS_CPP_17
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j[std::string_view("key")], std::bad_alloc&);
+        CHECK(j.is_null());
+#endif
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j.push_back(my_json(1)), std::bad_alloc&);
+        CHECK(j.is_null());
+
+        const my_json one = 1;
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j.push_back(one), std::bad_alloc&);
+        CHECK(j.is_null());
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j.push_back(my_json::object_t::value_type("key", 1)), std::bad_alloc&);
+        CHECK(j.is_null());
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j.emplace_back(1), std::bad_alloc&);
+        CHECK(j.is_null());
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j.emplace("key", 1), std::bad_alloc&);
+        CHECK(j.is_null());
+
+        const my_json object = {{"key", 1}};
+        next_construct_fails = true;
+        CHECK_THROWS_AS(j.update(object), std::bad_alloc&);
+        CHECK(j.is_null());
+
+        next_construct_fails = false;
+    }
+
+    // With iterator debugging, VS 2015's containers construct a proxy with the
+    // allocator in constructors that cannot report its failure, so a failing
+    // allocator crashes this section there (SIGSEGV with VS 2015 Debug x86).
+#if !(defined(_MSC_VER) && _MSC_VER < 1910 && defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
+    SECTION("converting into an existing value")
+    {
+        // to_json replaces the value it is given; the old one must survive a
+        // failed creation of the new one
+        my_json j = "old";
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::string("new")), std::bad_alloc&);
+        CHECK(j == "old");
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::vector<int> {1, 2}), std::bad_alloc&);
+        CHECK(j == "old");
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::vector<bool> {true, false}), std::bad_alloc&);
+        CHECK(j == "old");
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::map<std::string, int> {{"a", 1}}), std::bad_alloc&);
+        CHECK(j == "old");
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, my_json::binary_t({1, 2})), std::bad_alloc&);
+        CHECK(j == "old");
+
+        // the overloads for lvalues of the value types, for the value types
+        // themselves, and for the remaining compatible types
+        const std::string string = "new";
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, string), std::bad_alloc&);
+        CHECK(j == "old");
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, "new"), std::bad_alloc&);
+        CHECK(j == "old");
+
+        // to_json only moves a binary value that it converted from another
+        // container type, which my_json's std::vector<std::uint8_t> is not
+        using binary_constructor = nlohmann::detail::external_constructor<nlohmann::detail::value_t::binary>;
+        next_construct_fails = true;
+        CHECK_THROWS_AS(binary_constructor::construct(j, my_json::binary_t({1, 2})), std::bad_alloc&);
+        CHECK(j == "old");
+
+        my_json::array_t array = {1, 2};
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, array), std::bad_alloc&);
+        CHECK(j == "old");
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::move(array)), std::bad_alloc&);
+        CHECK(j == "old");
+
+        my_json::object_t object = {{"a", 1}};
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, object), std::bad_alloc&);
+        CHECK(j == "old");
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::move(object)), std::bad_alloc&);
+        CHECK(j == "old");
+
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, std::valarray<int> {1, 2}), std::bad_alloc&);
+        CHECK(j == "old");
+
+#if JSON_HAS_RANGES && !defined(__MINGW32__)
+        const std::vector<int> numbers = {1, 2};
+        next_construct_fails = true;
+        CHECK_THROWS_AS(nlohmann::to_json(j, numbers | std::views::filter([](int /*unused*/)
+        {
+            return true;
+        })), std::bad_alloc&);
+        CHECK(j == "old");
+#endif
+
+        next_construct_fails = false;
+        nlohmann::to_json(j, std::vector<int> {1, 2});
+        CHECK(j == my_json({1, 2}));
+    }
+#endif
+}
+#endif

tests/src/unit-alt-string.cpp

@@ -163,16 +163,7 @@ void int_to_string(alt_string& target, std::size_t value)
     target = std::to_string(value).c_str();
 }
 
-using alt_json = nlohmann::basic_json <
+using alt_json = nlohmann::json::with_string_t<alt_string>;
-                 std::map,
-                 std::vector,
-                 alt_string,
-                 bool,
-                 std::int64_t,
-                 std::uint64_t,
-                 double,
-                 std::allocator,
-                 nlohmann::adl_serializer >;
 
 bool operator<(const char* op1, const alt_string& op2) noexcept
 {

tests/src/unit-binary_formats.cpp

@@ -11,10 +11,15 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
+#include <cmath>
 #include <fstream>
+#include <limits>
+#include <map>
+#include <string>
+#include <vector>
 #include "make_test_data_available.hpp"
 
-TEST_CASE("Binary Formats" * doctest::skip())
+TEST_CASE("Binary Formats")
 {
     SECTION("canada.json")
     {
@@ -142,48 +147,6 @@ TEST_CASE("Binary Formats" * doctest::skip())
         CHECK((100.0 * double(ubjson_3_size) / double(json_size)) == Approx(84.963));
     }
 
-    SECTION("jeopardy.json")
-    {
-        const auto* filename = TEST_DATA_DIRECTORY "/jeopardy/jeopardy.json";
-        json j = json::parse(std::ifstream(filename));
-
-        const auto json_size = j.dump().size();
-        const auto bjdata_1_size = json::to_bjdata(j).size();
-        const auto bjdata_2_size = json::to_bjdata(j, true).size();
-        const auto bjdata_3_size = json::to_bjdata(j, true, true).size();
-        const auto bon8_size = json::to_bon8(j).size();
-        const auto bson_size = json::to_bson({{"", j}}).size(); // wrap array in object for BSON
-        const auto cbor_size = json::to_cbor(j).size();
-        const auto msgpack_size = json::to_msgpack(j).size();
-        const auto ubjson_1_size = json::to_ubjson(j).size();
-        const auto ubjson_2_size = json::to_ubjson(j, true).size();
-        const auto ubjson_3_size = json::to_ubjson(j, true, true).size();
-
-        CHECK(json_size == 52508728);
-        CHECK(bjdata_1_size == 50710965);
-        CHECK(bjdata_2_size == 51144830);
-        CHECK(bjdata_3_size == 51144830);
-        CHECK(bon8_size == 45942080);
-        CHECK(bson_size == 56008520);
-        CHECK(cbor_size == 46187320);
-        CHECK(msgpack_size == 46158575);
-        CHECK(ubjson_1_size == 50710965);
-        CHECK(ubjson_2_size == 51144830);
-        CHECK(ubjson_3_size == 49861422);
-
-        CHECK((100.0 * double(json_size) / double(json_size)) == Approx(100.0));
-        CHECK((100.0 * double(bjdata_1_size) / double(json_size)) == Approx(96.576));
-        CHECK((100.0 * double(bjdata_2_size) / double(json_size)) == Approx(97.402));
-        CHECK((100.0 * double(bjdata_3_size) / double(json_size)) == Approx(97.402));
-        CHECK((100.0 * double(bon8_size) / double(json_size)) == Approx(87.494));
-        CHECK((100.0 * double(bson_size) / double(json_size)) == Approx(106.665));
-        CHECK((100.0 * double(cbor_size) / double(json_size)) == Approx(87.961));
-        CHECK((100.0 * double(msgpack_size) / double(json_size)) == Approx(87.906));
-        CHECK((100.0 * double(ubjson_1_size) / double(json_size)) == Approx(96.576));
-        CHECK((100.0 * double(ubjson_2_size) / double(json_size)) == Approx(97.402));
-        CHECK((100.0 * double(ubjson_3_size) / double(json_size)) == Approx(94.958));
-    }
-
     SECTION("sample.json")
     {
         const auto* filename = TEST_DATA_DIRECTORY "/json_testsuite/sample.json";
@@ -224,3 +187,183 @@ TEST_CASE("Binary Formats" * doctest::skip())
         CHECK((100.0 * double(ubjson_3_size) / double(json_size)) == Approx(89.450));
     }
 }
+
+// jeopardy.json is 52 MB and produces ~500 MB of serialization output, so it
+// is kept apart from the cheap corpus files above (#5418)
+TEST_CASE("Binary Formats (jeopardy.json)" * doctest::skip())
+{
+    const auto* filename = TEST_DATA_DIRECTORY "/jeopardy/jeopardy.json";
+    json j = json::parse(std::ifstream(filename));
+
+    const auto json_size = j.dump().size();
+    const auto bjdata_1_size = json::to_bjdata(j).size();
+    const auto bjdata_2_size = json::to_bjdata(j, true).size();
+    const auto bjdata_3_size = json::to_bjdata(j, true, true).size();
+    const auto bon8_size = json::to_bon8(j).size();
+    const auto bson_size = json::to_bson({{"", j}}).size(); // wrap array in object for BSON
+    const auto cbor_size = json::to_cbor(j).size();
+    const auto msgpack_size = json::to_msgpack(j).size();
+    const auto ubjson_1_size = json::to_ubjson(j).size();
+    const auto ubjson_2_size = json::to_ubjson(j, true).size();
+    const auto ubjson_3_size = json::to_ubjson(j, true, true).size();
+
+    CHECK(json_size == 52508728);
+    CHECK(bjdata_1_size == 50710965);
+    CHECK(bjdata_2_size == 51144830);
+    CHECK(bjdata_3_size == 51144830);
+    CHECK(bon8_size == 45942080);
+    CHECK(bson_size == 56008520);
+    CHECK(cbor_size == 46187320);
+    CHECK(msgpack_size == 46158575);
+    CHECK(ubjson_1_size == 50710965);
+    CHECK(ubjson_2_size == 51144830);
+    CHECK(ubjson_3_size == 49861422);
+
+    CHECK((100.0 * double(json_size) / double(json_size)) == Approx(100.0));
+    CHECK((100.0 * double(bjdata_1_size) / double(json_size)) == Approx(96.576));
+    CHECK((100.0 * double(bjdata_2_size) / double(json_size)) == Approx(97.402));
+    CHECK((100.0 * double(bjdata_3_size) / double(json_size)) == Approx(97.402));
+    CHECK((100.0 * double(bon8_size) / double(json_size)) == Approx(87.494));
+    CHECK((100.0 * double(bson_size) / double(json_size)) == Approx(106.665));
+    CHECK((100.0 * double(cbor_size) / double(json_size)) == Approx(87.961));
+    CHECK((100.0 * double(msgpack_size) / double(json_size)) == Approx(87.906));
+    CHECK((100.0 * double(ubjson_1_size) / double(json_size)) == Approx(96.576));
+    CHECK((100.0 * double(ubjson_2_size) / double(json_size)) == Approx(97.402));
+    CHECK((100.0 * double(ubjson_3_size) / double(json_size)) == Approx(94.958));
+}
+
+namespace
+{
+// the binary formats as function pointers for "Binary formats with narrow number types";
+// named functions rather than lambdas, because clang 3.5 cannot convert a lambda
+// to a function pointer in the braced initializer of the format table
+using narrow_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int32_t, std::uint32_t, float>;
+using bytes = std::vector<std::uint8_t>;
+
+bytes encode_cbor(const json& j)
+{
+    return json::to_cbor(j);
+}
+narrow_json decode_cbor(const bytes& v, bool allow_exceptions)
+{
+    return narrow_json::from_cbor(v, true, allow_exceptions);
+}
+
+bytes encode_msgpack(const json& j)
+{
+    return json::to_msgpack(j);
+}
+narrow_json decode_msgpack(const bytes& v, bool allow_exceptions)
+{
+    return narrow_json::from_msgpack(v, true, allow_exceptions);
+}
+
+bytes encode_ubjson(const json& j)
+{
+    return json::to_ubjson(j);
+}
+narrow_json decode_ubjson(const bytes& v, bool allow_exceptions)
+{
+    return narrow_json::from_ubjson(v, true, allow_exceptions);
+}
+
+bytes encode_bjdata(const json& j)
+{
+    return json::to_bjdata(j);
+}
+narrow_json decode_bjdata(const bytes& v, bool allow_exceptions)
+{
+    return narrow_json::from_bjdata(v, true, allow_exceptions);
+}
+
+// BSON can only store numbers as object members
+bytes encode_bson(const json& j)
+{
+    return json::to_bson(json{{"a", j}});
+}
+narrow_json decode_bson(const bytes& v, bool allow_exceptions)
+{
+    const auto result = narrow_json::from_bson(v, true, allow_exceptions);
+    return result.is_discarded() ? result : result.at("a");
+}
+
+bytes encode_bon8(const json& j)
+{
+    return json::to_bon8(j);
+}
+narrow_json decode_bon8(const bytes& v, bool allow_exceptions)
+{
+    return narrow_json::from_bon8(v, true, allow_exceptions);
+}
+
+} // namespace
+
+TEST_CASE("Binary formats with narrow number types")
+{
+    // Numbers that do not fit the number types are handled like the lexer
+    // handles them in JSON text: an integer that fits neither integer type is
+    // stored as a floating-point number, and a finite floating-point number
+    // that overflows number_float_t is rejected with out_of_range.406.
+    struct binary_format
+    {
+        const char* name;
+        bytes (*encode)(const json&);
+        narrow_json (*decode)(const bytes&, bool);
+    };
+
+    const std::vector<binary_format> formats =
+    {
+        {"CBOR", encode_cbor, decode_cbor},
+        {"MessagePack", encode_msgpack, decode_msgpack},
+        {"UBJSON", encode_ubjson, decode_ubjson},
+        {"BJData", encode_bjdata, decode_bjdata},
+        {"BSON", encode_bson, decode_bson},
+        {"BON8", encode_bon8, decode_bon8},
+    };
+
+    for (const auto& format : formats)
+    {
+        const std::string name = format.name;
+        INFO("format := ", name);
+        const auto roundtrip = [&format](const json & j)
+        {
+            return format.decode(format.encode(j), true);
+        };
+
+        // integers that fit keep their type
+        CHECK(roundtrip(json(-5)).is_number_integer());
+        CHECK(roundtrip(json(-5)).get<std::int32_t>() == -5);
+        CHECK(roundtrip(json(3000000000u)).is_number_unsigned());
+        CHECK(roundtrip(json(3000000000u)).get<std::uint32_t>() == 3000000000u);
+
+        // integers that fit neither integer type are stored as float
+        CHECK(roundtrip(json(5000000000u)).is_number_float());
+        CHECK(roundtrip(json(5000000000u)).get<float>() == 5000000000.0f);
+        if (name != "BON8") // BON8 cannot encode integers above INT64_MAX
+        {
+            CHECK(roundtrip(json(10000000000000000000u)).is_number_float());
+            CHECK(roundtrip(json(10000000000000000000u)).get<float>() == 10000000000000000000.0f);
+        }
+        CHECK(roundtrip(json(-3000000000LL)).is_number_float());
+        CHECK(roundtrip(json(-3000000000LL)).get<float>() == -3000000000.0f);
+        CHECK(roundtrip(json(-5000000000LL)).is_number_float());
+        CHECK(roundtrip(json(-5000000000LL)).get<float>() == -5000000000.0f);
+
+        // floating-point numbers that fit
+        CHECK(roundtrip(json(1.5)).get<float>() == 1.5f);
+        const auto just_above_max = std::nextafter(static_cast<double>((std::numeric_limits<float>::max)()),
+                                    std::numeric_limits<double>::infinity());
+        CHECK(roundtrip(json(just_above_max)).get<float>() == (std::numeric_limits<float>::max)());
+
+        // infinity and NaN are passed on
+        CHECK(std::isinf(roundtrip(json(std::numeric_limits<double>::infinity())).get<float>()));
+        CHECK(std::isnan(roundtrip(json(std::numeric_limits<double>::quiet_NaN())).get<float>()));
+
+        // finite floating-point numbers that overflow number_float_t are rejected
+        const std::string message = "[json.exception.out_of_range.406] syntax error while parsing " + name
+                                    + " value: number overflow";
+        CHECK_THROWS_WITH_AS(roundtrip(json(1e300)), message.c_str(), narrow_json::out_of_range&);
+        CHECK_THROWS_WITH_AS(roundtrip(json(-1e300)), message.c_str(), narrow_json::out_of_range&);
+        CHECK(format.decode(format.encode(json(1e300)), false).is_discarded());
+    }
+}

tests/src/unit-bjdata.cpp

@@ -9,6 +9,14 @@
 #include "doctest_compatibility.h"
 
 #define JSON_TESTS_PRIVATE
+// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
+// line *before* including json.hpp, since the library #undefs it once the header
+// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
+// tests of deprecated functions are skipped if these functions are deleted
+#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
+    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+#endif
+
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
@@ -106,10 +114,59 @@ TEST_CASE("BJData")
     {
         SECTION("discarded")
         {
-            // discarded values are not serialized
+            // a discarded value cannot be serialized to BJData
             json const j = json::value_t::discarded;
-            const auto result = json::to_bjdata(j);
+            CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] cannot serialize discarded value to BJData", json::type_error&);
-            CHECK(result.empty());
+        }
+
+        SECTION("discarded values nested in a container")
+        {
+            json const discarded = json::value_t::discarded;
+
+            SECTION("in an array")
+            {
+                json const j = {1, discarded, 2};
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] (/1) cannot serialize discarded value to BJData", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] cannot serialize discarded value to BJData", json::type_error&);
+#endif
+            }
+
+            SECTION("as an object value")
+            {
+                json j;
+                j["a"] = 1;
+                j["b"] = discarded;
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] (/b) cannot serialize discarded value to BJData", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] cannot serialize discarded value to BJData", json::type_error&);
+#endif
+            }
+
+            SECTION("nested deeper (array in object in array)")
+            {
+                json inner_array = {1, discarded};
+                json middle_object;
+                middle_object["x"] = inner_array;
+                json const j = {middle_object};
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] (/0/x/1) cannot serialize discarded value to BJData", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j), "[json.exception.type_error.321] cannot serialize discarded value to BJData", json::type_error&);
+#endif
+            }
+
+            SECTION("optimized array of all-discarded elements")
+            {
+                json const j = {discarded, discarded};
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j, true, true), "[json.exception.type_error.321] (/0) cannot serialize discarded value to BJData", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_bjdata(j, true, true), "[json.exception.type_error.321] cannot serialize discarded value to BJData", json::type_error&);
+#endif
+            }
         }
 
         SECTION("null")
@@ -1229,6 +1286,32 @@ TEST_CASE("BJData")
                     CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vec2), "[json.exception.parse_error.115] parse error at byte 5: syntax error while parsing BJData high-precision number: invalid number text: 1A", json::parse_error);
                     std::vector<uint8_t> const vec3 = {'H', 'i', 2, '1', '.'};
                     CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vec3), "[json.exception.parse_error.115] parse error at byte 5: syntax error while parsing BJData high-precision number: invalid number text: 1.", json::parse_error);
+                    // Reject NULs where they are read, including trailing NULs and payloads cut off after one.
+                    SECTION("NUL in high-precision number (issue #5753)")
+                    {
+                        for (const auto& vec : std::vector<std::vector<uint8_t>>
+                    {
+                        {'H', 'i', 3, '1', 0, 'x'},
+                        {'H', 'i', 2, '1', 0},
+                        {'H', 'i', 3, '1', 0}
+                    })
+                        {
+                            CAPTURE(vec)
+                            CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vec), "[json.exception.parse_error.115] parse error at byte 5: syntax error while parsing BJData high-precision number: invalid number text; last byte: 0x00", json::parse_error);
+                            CHECK(json::from_bjdata(vec, true, false).is_discarded());
+                            CHECK(json::from_bjdata(vec, false, false).is_discarded());
+                        }
+
+                        std::vector<uint8_t> const nested = {'[', 'H', 'i', 3, '1', 0, 'x', ']'};
+                        CHECK_THROWS_WITH_AS(_ = json::from_bjdata(nested), "[json.exception.parse_error.115] parse error at byte 6: syntax error while parsing BJData high-precision number: invalid number text; last byte: 0x00", json::parse_error);
+                        CHECK(json::from_bjdata(nested, true, false).is_discarded());
+
+                        std::vector<uint8_t> const valid = {'H', 'i', 1, '1'};
+                        const auto j = json::from_bjdata(valid);
+                        CHECK(j.is_number_unsigned());
+                        CHECK(j == json(1));
+                    }
+
                     std::vector<uint8_t> const vec_overflow = {'H', 'i', 5, '1', 'e', '4', '0', '0'};
                     CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vec_overflow), "[json.exception.out_of_range.406] number overflow parsing '1e400'", json::out_of_range);
                     std::vector<uint8_t> const vec4 = {'H', 2, '1', '0'};
@@ -4490,3 +4573,79 @@ TEST_CASE("BJData roundtrips" * doctest::skip())
         }
     }
 }
+
+TEST_CASE("issue #5648 - from_bjdata(ptr, len) must read len bytes, not treat ptr as a C string")
+{
+    // to_bjdata() encodes the integer 0 as the two bytes 'i' 0x00 (a BJData
+    // type marker followed by the value byte 0x00), so the packed data
+    // below contains a 0x00 byte before its end.
+    const json j = {{"a", 0}};
+    const std::vector<std::uint8_t> packed = json::to_bjdata(j);
+    bool contains_nul = false;
+    for (const auto byte : packed)
+    {
+        contains_nul |= (byte == 0x00);
+    }
+    REQUIRE(contains_nul);
+
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+    // before the fix, from_bjdata had no (ptr, len) overload, so this call
+    // bound to from_bjdata(InputType&&, bool strict) instead: ptr was read
+    // as a NUL-terminated C string (stopping at the embedded 0x00 byte), and
+    // len was silently converted to the strict flag. The deprecated
+    // overload added for this issue forwards to from_bjdata(ptr, ptr + len,
+    // ...) instead, like from_ubjson's deprecated (ptr, len) overload does.
+    json result;
+    CHECK_NOTHROW(result = json::from_bjdata(packed.data(), packed.size()));
+    CHECK(result == j);
+
+    // len must not collapse into the strict flag either
+    CHECK(json::from_bjdata(packed.data(), packed.size(), false) == j);
+#endif
+}
+
+TEST_CASE("BJData large strings and binaries (chunked reader)")
+{
+    // Strings share get_ubjson_string() -> get_string() -> get_bytes() with
+    // plain UBJSON. Binary values are different: only a Draft 3 optimized
+    // array (type marker 'B') is read back as a binary value, through
+    // get_binary() -> get_bytes() (see parse_ubjson_internal()'s "If BJData
+    // type marker is 'B'" branch); Draft 2 (the default) writes a binary
+    // value as a plain array of uint8_t numbers instead (see the "round trip
+    // of a binary value is value-stable, not byte-stable" test above), which
+    // never reaches get_bytes(). Both reads happen in bounded chunks
+    // (binary_reader.hpp, chunk_size == 4096); check lengths around and
+    // beyond that size, for both vector (iterator) and pointer inputs.
+    for (const std::size_t len :
+            {
+                std::size_t{0}, std::size_t{1}, std::size_t{4095}, std::size_t{4096},
+                std::size_t{4097}, std::size_t{8192}, std::size_t{100000}
+            })
+    {
+        CAPTURE(len)
+
+        // string
+        const json j_string = std::string(len, 'x');
+        const std::vector<std::uint8_t> v_string = json::to_bjdata(j_string);
+        CHECK(json::from_bjdata(v_string) == j_string);
+        // pointer input exercises the std::memcpy fast path
+        CHECK(json::from_bjdata(reinterpret_cast<const char*>(v_string.data()),
+                                reinterpret_cast<const char*>(v_string.data()) + v_string.size()) == j_string);
+
+        // binary, forced into the Draft 3 optimized ('B' marker) encoding
+        const json j_binary = json::binary(std::vector<std::uint8_t>(len, 0xCD));
+        const std::vector<std::uint8_t> v_binary = json::to_bjdata(j_binary, true, true, json::bjdata_version_t::draft3);
+        CHECK(json::from_bjdata(v_binary) == j_binary);
+        CHECK(json::from_bjdata(reinterpret_cast<const char*>(v_binary.data()),
+                                reinterpret_cast<const char*>(v_binary.data()) + v_binary.size()) == j_binary);
+
+        // a truncated payload must still be reported as an error
+        if (len > 16)
+        {
+            std::vector<std::uint8_t> truncated = v_string;
+            truncated.resize(truncated.size() - 8);
+            json _;
+            CHECK_THROWS_AS(_ = json::from_bjdata(truncated), json::parse_error);
+        }
+    }
+}

tests/src/unit-bon8.cpp

@@ -8,6 +8,14 @@
 
 #include "doctest_compatibility.h"
 
+// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
+// line *before* including json.hpp, since the library #undefs it once the header
+// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
+// tests of deprecated functions are skipped if these functions are deleted
+#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
+    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+#endif
+
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
@@ -1014,6 +1022,36 @@ TEST_CASE("BON8 roundtrips" * doctest::skip())
     }
 }
 
+TEST_CASE("issue #5648 - from_bon8(ptr, len) must read len bytes, not treat ptr as a C string")
+{
+    // to_bon8() encodes the integer 40 as the two bytes 0xC2 0x00 (a BON8
+    // lead byte followed by a continuation byte of 0x00), so the packed data
+    // below contains a 0x00 byte before its end.
+    const json j = {{"a", 40}, {"b", "x"}};
+    const std::vector<std::uint8_t> packed = json::to_bon8(j);
+    bool contains_nul = false;
+    for (const auto byte : packed)
+    {
+        contains_nul |= (byte == 0x00);
+    }
+    REQUIRE(contains_nul);
+
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+    // before the fix, from_bon8 had no (ptr, len) overload, so this call
+    // bound to from_bon8(InputType&&, bool strict) instead: ptr was read as
+    // a NUL-terminated C string (stopping at the embedded 0x00 byte), and
+    // len was silently converted to the strict flag. The deprecated
+    // overload added for this issue forwards to from_bon8(ptr, ptr + len,
+    // ...) instead, like from_cbor's deprecated (ptr, len) overload does.
+    json result;
+    CHECK_NOTHROW(result = json::from_bon8(packed.data(), packed.size()));
+    CHECK(result == j);
+
+    // len must not collapse into the strict flag either
+    CHECK(json::from_bon8(packed.data(), packed.size(), false) == j);
+#endif
+}
+
 #ifdef JSON_HAS_CPP_17
 TEST_CASE("BON8 with std::byte")
 {

tests/src/unit-brace-init-copy-semantics.cpp

@@ -72,6 +72,28 @@ TEST_CASE("JSON_BRACE_INIT_COPY_SEMANTICS")
         CHECK(j7 == json::array({1, 2}));
     }
 
+    SECTION("single-element brace initialization copies a pair-shaped array value (#5662)")
+    {
+        // a JSON value that happens to be a 2-element array whose first
+        // element is a string must still be copied, not turned into an
+        // object; only a braced list written in the source, such as the
+        // inner {"key", "value"} of {{"key", "value"}}, describes an object
+        json const pair_shaped = json::array({"key", 42});
+
+        json const j1{pair_shaped};
+        CHECK(j1.is_array());
+        CHECK(j1 == pair_shaped);
+
+        json const j2 = {pair_shaped};
+        CHECK(j2.is_array());
+        CHECK(j2 == pair_shaped);
+
+        // the same holds for an rvalue of the same shape
+        json const j3{json::array({"key", 42})};
+        CHECK(j3.is_array());
+        CHECK(j3 == pair_shaped);
+    }
+
     SECTION("what the macro does not change")
     {
         // lists with more than one element are unaffected

tests/src/unit-bson.cpp

@@ -8,6 +8,14 @@
 
 #include "doctest_compatibility.h"
 
+// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
+// line *before* including json.hpp, since the library #undefs it once the header
+// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
+// tests of deprecated functions are skipped if these functions are deleted
+#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
+    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+#endif
+
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
@@ -141,6 +149,54 @@ TEST_CASE("BSON")
             json const j = std::vector<int> {1, 2, 3, 4, 5, 6, 7};
             CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is array", json::type_error&);
         }
+
+        SECTION("discarded")
+        {
+            json const j = json::value_t::discarded;
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is discarded", json::type_error&);
+        }
+    }
+
+    SECTION("discarded values nested in a container cannot be serialized to BSON")
+    {
+        json const discarded = json::value_t::discarded;
+
+        SECTION("as an object value")
+        {
+            json j;
+            j["a"] = 1;
+            j["b"] = discarded;
+#if JSON_DIAGNOSTICS
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.321] (/b) cannot serialize discarded value to BSON", json::type_error&);
+#else
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.321] cannot serialize discarded value to BSON", json::type_error&);
+#endif
+        }
+
+        SECTION("in an array that is an object value")
+        {
+            json j;
+            j["a"] = json::array({1, discarded, 2});
+#if JSON_DIAGNOSTICS
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.321] (/a/1) cannot serialize discarded value to BSON", json::type_error&);
+#else
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.321] cannot serialize discarded value to BSON", json::type_error&);
+#endif
+        }
+
+        SECTION("nested deeper (array in object in object)")
+        {
+            json inner_array = {1, discarded};
+            json middle_object;
+            middle_object["x"] = inner_array;
+            json j;
+            j["outer"] = middle_object;
+#if JSON_DIAGNOSTICS
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.321] (/outer/x/1) cannot serialize discarded value to BSON", json::type_error&);
+#else
+            CHECK_THROWS_WITH_AS(json::to_bson(j), "[json.exception.type_error.321] cannot serialize discarded value to BSON", json::type_error&);
+#endif
+        }
     }
 
     SECTION("keys containing code-point U+0000 cannot be serialized to BSON")
@@ -1261,8 +1317,10 @@ TEST_CASE("BSON input that cannot be read is discarded by every overload")
     CHECK_THROWS_AS(_ = json::from_bson(input.begin(), input.end()), json::parse_error&);
     CHECK(json::from_bson(input, true, false).is_discarded());
     CHECK(json::from_bson(input.begin(), input.end(), true, false).is_discarded());
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
     CHECK(json::from_bson(input.data(), input.size(), true, false).is_discarded());
     CHECK(json::from_bson({input.data(), input.size()}, true, false).is_discarded());
+#endif
 }
 
 TEST_CASE("BSON SAX parsing stops at every event")
@@ -1740,6 +1798,7 @@ TEST_CASE("BSON roundtrips" * doctest::skip())
                 CHECK(j1 == j2);
             }
 
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
             {
                 INFO_WITH_TEMP(filename + ": uint8_t* and size");
                 // parse JSON file
@@ -1754,6 +1813,7 @@ TEST_CASE("BSON roundtrips" * doctest::skip())
                 // compare parsed JSON values
                 CHECK(j1 == j2);
             }
+#endif
 
             {
                 INFO_WITH_TEMP(filename + ": output to output adapters");
@@ -1933,3 +1993,47 @@ TEST_CASE("Invalid document size handling")
         CHECK(json::from_bson(v, true, false).is_discarded());
     }
 }
+
+TEST_CASE("BSON large strings and binaries (chunked reader)")
+{
+    // get_bson_string()/get_bson_binary() both read through get_string()/
+    // get_binary(), which read in bounded chunks (binary_reader.hpp,
+    // chunk_size == 4096); make sure roundtripping is correct for lengths
+    // around and beyond that chunk size, for both vector (iterator) and
+    // pointer inputs. BSON only accepts an object at the top level, so the
+    // string/binary value is wrapped in one.
+    for (const std::size_t len :
+            {
+                std::size_t{0}, std::size_t{1}, std::size_t{4095}, std::size_t{4096},
+                std::size_t{4097}, std::size_t{8192}, std::size_t{100000}
+            })
+    {
+        CAPTURE(len)
+
+        // string
+        const json j_string = {{"k", std::string(len, 'x')}};
+        const std::vector<std::uint8_t> v_string = json::to_bson(j_string);
+        CHECK(json::from_bson(v_string) == j_string);
+        // pointer input exercises the std::memcpy fast path
+        CHECK(json::from_bson(reinterpret_cast<const char*>(v_string.data()),
+                              reinterpret_cast<const char*>(v_string.data()) + v_string.size()) == j_string);
+
+        // binary (BSON binary values always carry a subtype, so give one
+        // explicitly; otherwise from_bson() would round-trip to subtype 0
+        // rather than back to the original "no subtype" value)
+        const json j_binary = {{"k", json::binary(std::vector<std::uint8_t>(len, 0xCD), std::uint8_t{0})}};
+        const std::vector<std::uint8_t> v_binary = json::to_bson(j_binary);
+        CHECK(json::from_bson(v_binary) == j_binary);
+        CHECK(json::from_bson(reinterpret_cast<const char*>(v_binary.data()),
+                              reinterpret_cast<const char*>(v_binary.data()) + v_binary.size()) == j_binary);
+
+        // a truncated payload must still be reported as an error
+        if (len > 16)
+        {
+            std::vector<std::uint8_t> truncated = v_string;
+            truncated.resize(truncated.size() - 8);
+            json _;
+            CHECK_THROWS_AS(_ = json::from_bson(truncated), json::parse_error);
+        }
+    }
+}

tests/src/unit-cbor.cpp

@@ -8,6 +8,14 @@
 
 #include "doctest_compatibility.h"
 
+// capture whether JSON_DELETE_DEPRECATED_FUNCTIONS was enabled on the command
+// line *before* including json.hpp, since the library #undefs it once the header
+// has been fully processed (see include/nlohmann/detail/macro_unscope.hpp); the
+// tests of deprecated functions are skipped if these functions are deleted
+#if defined(JSON_DELETE_DEPRECATED_FUNCTIONS) && (JSON_DELETE_DEPRECATED_FUNCTIONS == 1)
+    #define JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
+#endif
+
 #include <nlohmann/json.hpp>
 using nlohmann::json;
 
@@ -30,10 +38,49 @@ TEST_CASE("CBOR")
     {
         SECTION("discarded")
         {
-            // discarded values are not serialized
+            // a discarded value cannot be serialized to CBOR
             json const j = json::value_t::discarded;
-            const auto result = json::to_cbor(j);
+            CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] cannot serialize discarded value to CBOR", json::type_error&);
-            CHECK(result.empty());
+        }
+
+        SECTION("discarded values nested in a container")
+        {
+            json const discarded = json::value_t::discarded;
+
+            SECTION("in an array")
+            {
+                json const j = {1, discarded, 2};
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] (/1) cannot serialize discarded value to CBOR", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] cannot serialize discarded value to CBOR", json::type_error&);
+#endif
+            }
+
+            SECTION("as an object value")
+            {
+                json j;
+                j["a"] = 1;
+                j["b"] = discarded;
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] (/b) cannot serialize discarded value to CBOR", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] cannot serialize discarded value to CBOR", json::type_error&);
+#endif
+            }
+
+            SECTION("nested deeper (array in object in array)")
+            {
+                json inner_array = {1, discarded};
+                json middle_object;
+                middle_object["x"] = inner_array;
+                json const j = {middle_object};
+#if JSON_DIAGNOSTICS
+                CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] (/0/x/1) cannot serialize discarded value to CBOR", json::type_error&);
+#else
+                CHECK_THROWS_WITH_AS(json::to_cbor(j), "[json.exception.type_error.321] cannot serialize discarded value to CBOR", json::type_error&);
+#endif
+            }
         }
 
         SECTION("NaN")
@@ -1652,7 +1699,7 @@ TEST_CASE("CBOR")
             CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xA1, 0x61, 0X61})), "[json.exception.parse_error.110] parse error at byte 4: syntax error while parsing CBOR value: unexpected end of input", json::parse_error&);
             CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0xBF, 0x61, 0X61})), "[json.exception.parse_error.110] parse error at byte 4: syntax error while parsing CBOR value: unexpected end of input", json::parse_error&);
             CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x5F})), "[json.exception.parse_error.110] parse error at byte 2: syntax error while parsing CBOR binary: unexpected end of input", json::parse_error&);
-            CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x5F, 0x00})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR binary: expected length specification (0x40-0x5B) or indefinite binary array type (0x5F); last byte: 0x00", json::parse_error&);
+            CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x5F, 0x00})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR binary: expected length specification (0x40-0x5B); last byte: 0x00", json::parse_error&);
             CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x41})), "[json.exception.parse_error.110] parse error at byte 2: syntax error while parsing CBOR binary: unexpected end of input", json::parse_error&);
 
             CHECK(json::from_cbor(std::vector<uint8_t>({0x18}), true, false).is_discarded());
@@ -2215,8 +2262,10 @@ TEST_CASE("CBOR input that cannot be read is discarded by every overload")
     CHECK_THROWS_AS(_ = json::from_cbor(input.begin(), input.end()), json::parse_error&);
     CHECK(json::from_cbor(input, true, false).is_discarded());
     CHECK(json::from_cbor(input.begin(), input.end(), true, false).is_discarded());
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
     CHECK(json::from_cbor(input.data(), input.size(), true, false).is_discarded());
     CHECK(json::from_cbor({input.data(), input.size()}, true, false).is_discarded());
+#endif
 
     // a string that ends early, read through iterators that are not
     // contiguous and have to be copied from one element at a time
@@ -2256,22 +2305,21 @@ TEST_CASE("CBOR indefinite-length strings do not recurse per chunk")
 {
     // Reading an indefinite-length string or byte array used to call itself
     // once per chunk, so a payload of repeated 0x7F (or 0x5F) bytes exhausted
-    // the call stack before any of the input was rejected. The open levels are
+    // the call stack before any of the input was rejected. Nested indefinite
-    // counted now, and the levels below prove the reader still reads the same
+    // chunks are now rejected at the second byte, without recursing.
-    // values and reports the same errors at the same byte offsets.
     json _;
 
-    SECTION("many open levels are reported, not crashed on")
+    SECTION("nested levels are rejected, not crashed on")
     {
         const std::vector<uint8_t> input(200000, 0x7F);
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 200001: syntax error while parsing CBOR string: unexpected end of input", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: indefinite-length string is not allowed inside indefinite-length string; last byte: 0x7F", json::parse_error&);
         CHECK(json::from_cbor(input, true, false).is_discarded());
     }
 
-    SECTION("many open levels are reported, not crashed on (binary)")
+    SECTION("nested levels are rejected, not crashed on (binary)")
     {
         const std::vector<uint8_t> input(200000, 0x5F);
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 200001: syntax error while parsing CBOR binary: unexpected end of input", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR binary: indefinite-length binary array is not allowed inside indefinite-length binary array; last byte: 0x5F", json::parse_error&);
         CHECK(json::from_cbor(input, true, false).is_discarded());
     }
 
@@ -2279,22 +2327,22 @@ TEST_CASE("CBOR indefinite-length strings do not recurse per chunk")
     {
         CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0xFF})) == json(""));
         CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x61, 0x61, 0xFF})) == json("a"));
-        // nested indefinite-length strings are concatenated across levels
+        // empty and nonempty definite-length chunks concatenate in order
-        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x7F, 0x61, 0x61, 0xFF, 0x61, 0x62, 0xFF})) == json("ab"));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x61, 'a', 0x60, 0x61, 'b', 0x61, 'c', 0xFF})) == json("abc"));
-        CHECK(json::from_cbor(std::vector<uint8_t>({0x7F, 0x7F, 0x7F, 0x61, 0x7A, 0xFF, 0xFF, 0xFF})) == json("z"));
         CHECK(json::from_cbor(std::vector<uint8_t>({0xA1, 0x7F, 0x61, 0x61, 0xFF, 0x01})) == json({{"a", 1}}));
     }
 
     SECTION("chunks are still concatenated (binary)")
     {
         CHECK(json::from_cbor(std::vector<uint8_t>({0x5F, 0x41, 0x61, 0xFF})) == json::binary({0x61}));
-        CHECK(json::from_cbor(std::vector<uint8_t>({0x5F, 0x5F, 0x41, 0x61, 0xFF, 0x41, 0x62, 0xFF})) == json::binary({0x61, 0x62}));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x5F, 0xFF})) == json::binary({}));
+        CHECK(json::from_cbor(std::vector<uint8_t>({0x5F, 0x41, 0x61, 0x40, 0x41, 0x62, 0x41, 0x63, 0xFF})) == json::binary({0x61, 0x62, 0x63}));
     }
 
     SECTION("a chunk that is not a string is still rejected")
     {
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x7F, 0x7F, 0x00})), "[json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x00", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x7F, 0x00})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B); last byte: 0x00", json::parse_error&);
-        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x5F, 0x5F, 0x00})), "[json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR binary: expected length specification (0x40-0x5B) or indefinite binary array type (0x5F); last byte: 0x00", json::parse_error&);
+        CHECK_THROWS_WITH_AS(_ = json::from_cbor(std::vector<uint8_t>({0x5F, 0x00})), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR binary: expected length specification (0x40-0x5B); last byte: 0x00", json::parse_error&);
     }
 
     SECTION("a break marker outside an indefinite-length string is not a string")
@@ -2613,12 +2661,14 @@ TEST_CASE("CBOR roundtrips" * doctest::skip())
                 CHECK(j1 == j2);
             }
 
+#ifndef JSON_TEST_DEPRECATED_FUNCTIONS_DELETED
             {
                 INFO_WITH_TEMP(filename + ": uint8_t* and size");
                 json j2;
                 CHECK_NOTHROW(j2 = json::from_cbor({packed.data(), packed.size()}));
                 CHECK(j1 == j2);
             }
+#endif
 
             {
                 INFO_WITH_TEMP(filename + ": output to output adapters");
@@ -2845,9 +2895,17 @@ TEST_CASE("examples from RFC 8949 Appendix A")
     {
         const auto packed = utils::read_binary_file(TEST_DATA_DIRECTORY "/binary_data/cbor_binary.cbor");
         json j;
-        CHECK_NOTHROW(j = json::from_cbor(packed));
+        // the fixture's tail contains nested indefinite-length byte strings.
+        CHECK_THROWS_WITH_AS(j = json::from_cbor(packed), "[json.exception.parse_error.113] parse error at byte 513: syntax error while parsing CBOR binary: indefinite-length binary array is not allowed inside indefinite-length binary array; last byte: 0x5F", json::parse_error&);
 
-        const auto expected = utils::read_binary_file(TEST_DATA_DIRECTORY "/binary_data/cbor_binary.out");
+        // keep the byte-for-byte decoding check for its valid prefix: the first
+        // 512 encoded bytes contain 468 payload bytes in definite-length chunks.
+        auto valid_prefix = packed;
+        valid_prefix.resize(512);
+        valid_prefix.push_back(0xFF);
+        auto expected = utils::read_binary_file(TEST_DATA_DIRECTORY "/binary_data/cbor_binary.out");
+        expected.resize(468);
+        CHECK_NOTHROW(j = json::from_cbor(valid_prefix));
         CHECK(j == json::binary(expected));
 
         // 0xd8
@@ -3185,7 +3243,8 @@ TEST_CASE("Tagged values")
         // CBOR encodes negative integers as: result = -1 - n
         // For type 0x3B, n is an 8-byte uint64_t. Valid range for n with
         // the default int64_t is [0, INT64_MAX], producing results in [INT64_MIN, -1].
-        // When n > INT64_MAX, the result exceeds int64_t range and is rejected.
+        // When n > INT64_MAX, the result exceeds int64_t range and is stored
+        // as a floating-point number, as the lexer does for JSON text.
 
         SECTION("n = 0 is valid (result = -1)")
         {
@@ -3206,33 +3265,34 @@ TEST_CASE("Tagged values")
             CHECK(result.get<int64_t>() == (std::numeric_limits<int64_t>::min)());
         }
 
-        SECTION("n = INT64_MAX + 1 is rejected (overflow)")
+        SECTION("n = INT64_MAX + 1 is stored as float")
         {
             // n = INT64_MAX + 1 (0x8000000000000000)
-            // result = -1 - n = -9223372036854775809, which exceeds int64_t range
+            // result = -1 - n = -9223372036854775809, which exceeds int64_t range;
+            // the nearest double is -9223372036854775808.0
             const std::vector<uint8_t> input = {0x3B, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
-            json _;
+            const auto result = json::from_cbor(input);
-            CHECK_THROWS_WITH_AS(_ = json::from_cbor(input),
+            CHECK(result.is_number_float());
-                                 "[json.exception.parse_error.112] parse error at byte 9: syntax error while parsing CBOR value: negative integer overflow",
+            CHECK(result.get<double>() == -9223372036854775808.0);
-                                 json::parse_error);
+            CHECK(result == json::parse("-9223372036854775809"));
         }
 
-        SECTION("n = UINT64_MAX is rejected (overflow)")
+        SECTION("n = UINT64_MAX is stored as float")
         {
             // n = UINT64_MAX (0xFFFFFFFFFFFFFFFF)
             // result = -1 - n = -18446744073709551616, which exceeds int64_t range
             const std::vector<uint8_t> input = {0x3B, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
-            json _;
+            const auto result = json::from_cbor(input);
-            CHECK_THROWS_WITH_AS(_ = json::from_cbor(input),
+            CHECK(result.is_number_float());
-                                 "[json.exception.parse_error.112] parse error at byte 9: syntax error while parsing CBOR value: negative integer overflow",
+            CHECK(result.get<double>() == -18446744073709551616.0);
-                                 json::parse_error);
+            CHECK(result == json::parse("-18446744073709551616"));
         }
 
-        SECTION("overflow with allow_exceptions=false returns discarded")
+        SECTION("overflow with allow_exceptions=false is not an error")
         {
             const std::vector<uint8_t> input = {0x3B, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
             const auto result = json::from_cbor(input, true, false);
-            CHECK(result.is_discarded());
+            CHECK(result.is_number_float());
         }
     }