Fix Flawfinder: format the BSON element type without snprintf

Moving the report of an unsupported BSON element type into
skip_unsupported_bson_element() moved its snprintf() call, which
Flawfinder then reported as a new CWE-134 finding. The two hexadecimal
digits are now computed directly; the message is unchanged.

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

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,6 +2,7 @@
 
 - [ ] The changes are described in detail, both the what and why.
 - [ ] If applicable, an [existing issue](https://github.com/nlohmann/json/issues) is referenced.
+- [ ] If applicable, a fixed [OSS-Fuzz](https://issues.oss-fuzz.com) issue is referenced as `OSS-Fuzz: <id>` (see [fuzz testing](https://github.com/nlohmann/json/blob/develop/tests/fuzzing.md#handling-oss-fuzz-reports)).
 - [ ] The [Code coverage](https://coveralls.io/github/nlohmann/json) remained at 100%. A test case for every new line of code.
 - [ ] If applicable, the [documentation](https://json.nlohmann.me) is updated.
 - [ ] The source code is amalgamated by running `make amalgamate`.

.github/SECURITY.md

@@ -9,12 +9,23 @@ identified a security vulnerability in this repository, please use the GitHub Se
 Until it is published, this draft security advisory will only be visible to the maintainers of this project. Other
 users and teams may be added once the advisory is created.
 
-We will send a response indicating the next steps in handling your report. After the initial reply to your report, we
+We will send a first response within 14 days, indicating the next steps in handling your report. After the initial
-will keep you informed of the progress towards a fix and full announcement and may ask for additional information or
+reply to your report, we will keep you informed of the progress towards a fix and full announcement and may ask for
-guidance.
+additional information or guidance.
 
 For vulnerabilities in third-party dependencies or modules, please report them directly to the respective maintainers.
 
+## Disclosure and credit
+
+Once a fix is released, we publish the security advisory and list the fixed vulnerability in the release notes. We
+credit the reporter in both, unless they ask not to be named.
+
+## Supported versions
+
+Security fixes are made on the `develop` branch and shipped with the next release. Only the latest release receives
+security fixes; they are not backported to older releases. A release stops receiving security fixes when the next
+release is published, so please update to the latest release to get them.
+
 ## Unofficial packages
 
 This project does not publish an official npm package. The npm package

.github/labeler.yml

@@ -37,13 +37,13 @@ labels:
   files:
     - "include/nlohmann/detail/input/binary_reader\\.hpp"
     - "include/nlohmann/detail/output/binary_writer\\.hpp"
-    - "tests/src/unit-(bson|cbor|msgpack|ubjson|bjdata|binary_formats)"
+    - "tests/src/unit-(bson|cbor|msgpack|ubjson|bjdata|bon8|binary_formats)"
-    - "tests/src/fuzzer-parse_(bson|cbor|msgpack|ubjson|bjdata)"
+    - "tests/src/fuzzer-parse_(bson|cbor|msgpack|ubjson|bjdata|bon8)"
     - "docs/mkdocs/docs/features/binary_formats/"
-    - "docs/mkdocs/docs/(api/basic_json|examples)/(to|from)_(bson|cbor|msgpack|ubjson|bjdata)"
+    - "docs/mkdocs/docs/(api/basic_json|examples)/(to|from)_(bson|cbor|msgpack|ubjson|bjdata|bon8)"
 
 - label: "aspect: binary formats"
-  title: "(?i)(bson|cbor|msgpack|messagepack|ubjson|bjdata|binary format)"
+  title: "(?i)(bson|cbor|msgpack|messagepack|ubjson|bjdata|bon8|binary format)"
 
 - label: "python"
   files:

.github/workflows/check_amalgamation.yml

@@ -3,6 +3,10 @@ name: "Check amalgamation"
 on:
   pull_request:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 

.github/workflows/cifuzz.yml

@@ -1,6 +1,10 @@
 name: CIFuzz
 on: [pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 

.github/workflows/codeql-analysis.yml

@@ -38,14 +38,14 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+      uses: github/codeql-action/init@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4.38.1
       with:
         languages: c-cpp
 
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+      uses: github/codeql-action/autobuild@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4.38.1
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+      uses: github/codeql-action/analyze@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4.38.1

.github/workflows/dependency-review.yml

@@ -9,6 +9,10 @@
 name: 'Dependency Review'
 on: [pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 

.github/workflows/flawfinder.yml

@@ -5,6 +5,10 @@
 
 name: flawfinder
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
@@ -43,6 +47,6 @@ jobs:
           output: 'flawfinder_results.sarif'
 
       - name: Upload analysis results to GitHub Security tab
-        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+        uses: github/codeql-action/upload-sarif@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4.38.1
         with:
           sarif_file: ${{github.workspace}}/flawfinder_results.sarif

.github/workflows/labeler.yml

@@ -4,6 +4,12 @@ on:
   pull_request_target:
     types: [opened, synchronize]
 
+# pull_request_target runs on the base branch, so github.ref would put all pull
+# requests into one group; group by pull request number instead
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 

.github/workflows/scorecards.yml

@@ -14,6 +14,10 @@ on:
   push:
     branches: ["develop"]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
@@ -76,6 +80,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+        uses: github/codeql-action/upload-sarif@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4.38.1
         with:
           sarif_file: results.sarif

.github/workflows/semgrep.yml

@@ -19,6 +19,10 @@ on:
   schedule:
     - cron: '23 2 * * 4'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
@@ -61,7 +65,7 @@ jobs:
 
       # Upload SARIF file generated in previous step
       - name: Upload SARIF file
-        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+        uses: github/codeql-action/upload-sarif@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4.38.1
         with:
           sarif_file: semgrep.sarif
         if: always()

.github/workflows/windows.yml

@@ -124,11 +124,11 @@ jobs:
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - name: Run CMake (Release)
-        run: cmake -S . -B build -G "Visual Studio 17 2022" -A ARM64 -DJSON_BuildTests=On -DCMAKE_CXX_FLAGS="/W4 /WX"
+        run: cmake -S . -B build -G "Visual Studio 18 2026" -A ARM64 -DJSON_BuildTests=On -DCMAKE_CXX_FLAGS="/W4 /WX"
         if: matrix.build_type == 'Release'
         shell: pwsh
       - name: Run CMake (Debug)
-        run: cmake -S . -B build -G "Visual Studio 17 2022" -A ARM64 -DJSON_BuildTests=On -DJSON_FastTests=ON -DCMAKE_CXX_FLAGS="/W4 /WX"
+        run: cmake -S . -B build -G "Visual Studio 18 2026" -A ARM64 -DJSON_BuildTests=On -DJSON_FastTests=ON -DCMAKE_CXX_FLAGS="/W4 /WX"
         if: matrix.build_type == 'Debug'
         shell: pwsh
       - name: Build

BUILD.bazel

@@ -71,7 +71,6 @@ cc_library(
     ],
     includes = ["include"],
     visibility = ["//visibility:public"],
-    alwayslink = True,
 )
 
 cc_library(

Makefile

@@ -36,6 +36,7 @@ all:
 	@echo "clean - remove built files"
 	@echo "doctest - compile example files and check their output"
 	@echo "fuzz_testing - prepare fuzz testing of the JSON parser"
+	@echo "fuzz_testing_bon8 - prepare fuzz testing of the BON8 parser"
 	@echo "fuzz_testing_bson - prepare fuzz testing of the BSON parser"
 	@echo "fuzz_testing_cbor - prepare fuzz testing of the CBOR parser"
 	@echo "fuzz_testing_msgpack - prepare fuzz testing of the MessagePack parser"
@@ -71,6 +72,14 @@ fuzz_testing:
 	find tests/data/json_tests -size -5k -name *json | xargs -I{} cp "{}" fuzz-testing/testcases
 	@echo "Execute: afl-fuzz -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer"
 
+fuzz_testing_bon8:
+	rm -fr fuzz-testing
+	mkdir -p fuzz-testing fuzz-testing/testcases fuzz-testing/out
+	$(MAKE) parse_bon8_fuzzer -C tests CXX=afl-clang++
+	mv tests/parse_bon8_fuzzer fuzz-testing/fuzzer
+	find tests/data -size -5k -name *.bon8 | xargs -I{} cp "{}" fuzz-testing/testcases
+	@echo "Execute: afl-fuzz -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer"
+
 fuzz_testing_bson:
 	rm -fr fuzz-testing
 	mkdir -p fuzz-testing fuzz-testing/testcases fuzz-testing/out

README.md

@@ -17,7 +17,7 @@
 [![GitHub Downloads](https://img.shields.io/github/downloads/nlohmann/json/total)](https://github.com/nlohmann/json/releases)
 [![GitHub Issues](https://img.shields.io/github/issues/nlohmann/json.svg)](https://github.com/nlohmann/json/issues)
 [![Average time to resolve an issue](https://isitmaintained.com/badge/resolution/nlohmann/json.svg)](https://isitmaintained.com/project/nlohmann/json "Average time to resolve an issue")
-[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/289/badge)](https://bestpractices.coreinfrastructure.org/projects/289)
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/289/badge)](https://www.bestpractices.dev/projects/289)
 [![OpenSSF Scorecard](https://api.scorecard.dev/projects/github.com/nlohmann/json/badge)](https://scorecard.dev/viewer/?uri=github.com/nlohmann/json)
 [![Backup Status](https://app.cloudback.it/badge/nlohmann/json)](https://cloudback.it)
 [![GitHub Sponsors](https://img.shields.io/badge/GitHub-Sponsors-ff69b4)](https://github.com/sponsors/nlohmann)
@@ -40,7 +40,7 @@
   - [Implicit conversions](#implicit-conversions)
   - [Conversions to/from arbitrary types](#arbitrary-types-conversions)
   - [Specializing enum conversion](#specializing-enum-conversion)
-  - [Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData)](#binary-formats-bson-cbor-messagepack-ubjson-and-bjdata)
+  - [Binary formats (BSON, CBOR, MessagePack, UBJSON, BJData, and BON8)](#binary-formats-bson-cbor-messagepack-ubjson-bjdata-and-bon8)
 - [Customers](#customers)
 - [Ecosystem](#ecosystem)
 - [Supported compilers](#supported-compilers)
@@ -63,7 +63,7 @@ There are myriads of [JSON](https://json.org) libraries out there, and each may
 
 - **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings. The library is also included in all popular [package managers](https://json.nlohmann.me/integration/package_managers/).
 
-- **Serious testing**. Our code is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289). See the [quality assurance](https://json.nlohmann.me/community/quality_assurance) overview documentation.
+- **Serious testing**. Our code is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [OpenSSF Best Practices](https://www.bestpractices.dev/projects/289). See the [quality assurance](https://json.nlohmann.me/community/quality_assurance) overview documentation.
 
 Other aspects were not so important to us:
 
@@ -128,7 +128,7 @@ There is also a [**docset**](https://github.com/Kapeli/Dash-User-Contributions/t
 - **JSON Pointer functions**: [flatten](https://json.nlohmann.me/api/basic_json/flatten), [unflatten](https://json.nlohmann.me/api/basic_json/unflatten)
 - **JSON Patch functions**: [patch](https://json.nlohmann.me/api/basic_json/patch), [patch_inplace](https://json.nlohmann.me/api/basic_json/patch_inplace), [diff](https://json.nlohmann.me/api/basic_json/diff), [merge_patch](https://json.nlohmann.me/api/basic_json/merge_patch)
 - **Static functions**: [meta](https://json.nlohmann.me/api/basic_json/meta), [get_allocator](https://json.nlohmann.me/api/basic_json/get_allocator)
-- **Binary formats**: [from_bjdata](https://json.nlohmann.me/api/basic_json/from_bjdata), [from_bson](https://json.nlohmann.me/api/basic_json/from_bson), [from_cbor](https://json.nlohmann.me/api/basic_json/from_cbor), [from_msgpack](https://json.nlohmann.me/api/basic_json/from_msgpack), [from_ubjson](https://json.nlohmann.me/api/basic_json/from_ubjson), [to_bjdata](https://json.nlohmann.me/api/basic_json/to_bjdata), [to_bson](https://json.nlohmann.me/api/basic_json/to_bson), [to_cbor](https://json.nlohmann.me/api/basic_json/to_cbor), [to_msgpack](https://json.nlohmann.me/api/basic_json/to_msgpack), [to_ubjson](https://json.nlohmann.me/api/basic_json/to_ubjson)
+- **Binary formats**: [from_bjdata](https://json.nlohmann.me/api/basic_json/from_bjdata), [from_bon8](https://json.nlohmann.me/api/basic_json/from_bon8), [from_bson](https://json.nlohmann.me/api/basic_json/from_bson), [from_cbor](https://json.nlohmann.me/api/basic_json/from_cbor), [from_msgpack](https://json.nlohmann.me/api/basic_json/from_msgpack), [from_ubjson](https://json.nlohmann.me/api/basic_json/from_ubjson), [to_bjdata](https://json.nlohmann.me/api/basic_json/to_bjdata), [to_bon8](https://json.nlohmann.me/api/basic_json/to_bon8), [to_bson](https://json.nlohmann.me/api/basic_json/to_bson), [to_cbor](https://json.nlohmann.me/api/basic_json/to_cbor), [to_msgpack](https://json.nlohmann.me/api/basic_json/to_msgpack), [to_ubjson](https://json.nlohmann.me/api/basic_json/to_ubjson)
 - **Non-member functions**: [operator<<](https://json.nlohmann.me/api/operator_ltlt/), [operator>>](https://json.nlohmann.me/api/operator_gtgt/), [to_string](https://json.nlohmann.me/api/basic_json/to_string)
 - **Literals**: [operator""_json](https://json.nlohmann.me/api/operator_literal_json)
 - **Helper classes**: [std::hash&lt;basic_json&gt;](https://json.nlohmann.me/api/basic_json/std_hash), [std::swap&lt;basic_json&gt;](https://json.nlohmann.me/api/basic_json/std_swap)
@@ -496,7 +496,7 @@ bool key(string_t& val);
 bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex);
 ```
 
-The return value of each function determines whether parsing should proceed.
+The return value of each function determines whether parsing should proceed. For `parse_error`, returning `true` [recovers from the error](https://json.nlohmann.me/features/parsing/error_recovery/): the parser repairs the input and continues.
 
 To implement your own SAX handler, proceed as follows:
 
@@ -504,7 +504,7 @@ To implement your own SAX handler, proceed as follows:
 2. Create an object of your SAX interface class, e.g. `my_sax`.
 3. Call `bool json::sax_parse(input, &my_sax)`; where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.
 
-Note the `sax_parse` function only returns a `bool` indicating the result of the last executed SAX event. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).
+Note the `sax_parse` function only returns a `bool` indicating whether the input was parsed without errors and no SAX event returned `false`. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).
 
 ### STL-like access
 
@@ -1110,9 +1110,9 @@ Other Important points:
 - When using `get<ENUM_TYPE>()`, undefined JSON values will default to the first pair specified in your map. Select this default pair carefully. If you desire an exception in this circumstance use `NLOHMANN_JSON_SERIALIZE_ENUM_STRICT()` which behaves identically except for throwing an exception on unrecognized values.
 - If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the map will be returned when converting to or from JSON.
 
-### Binary formats (BSON, CBOR, MessagePack, UBJSON, and BJData)
+### Binary formats (BSON, CBOR, MessagePack, UBJSON, BJData, and BON8)
 
-Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance over a network. Hence, the library supports [BSON](https://bsonspec.org) (Binary JSON), [CBOR](https://cbor.io) (Concise Binary Object Representation), [MessagePack](https://msgpack.org), [UBJSON](https://ubjson.org) (Universal Binary JSON Specification) and [BJData](https://neurojson.org/bjdata) (Binary JData) to efficiently encode JSON values to byte vectors and to decode such vectors.
+Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance over a network. Hence, the library supports [BSON](https://bsonspec.org) (Binary JSON), [CBOR](https://cbor.io) (Concise Binary Object Representation), [MessagePack](https://msgpack.org), [UBJSON](https://ubjson.org) (Universal Binary JSON Specification), [BJData](https://neurojson.org/bjdata) (Binary JData), and [BON8](https://github.com/hikoworks/hikogui/blob/main/docs/BON8.md) (Binary Object Notation 8) to efficiently encode JSON values to byte vectors and to decode such vectors.
 
 ```cpp
 // create a JSON value
@@ -1149,6 +1149,14 @@ std::vector<std::uint8_t> v_ubjson = json::to_ubjson(j);
 
 // roundtrip
 json j_from_ubjson = json::from_ubjson(v_ubjson);
+
+// serialize to BON8
+std::vector<std::uint8_t> v_bon8 = json::to_bon8(j);
+
+// 0x88, 0x63, 0x6F, 0x6D, 0x70, 0x61, 0x63, 0x74, 0xF9, 0x73, 0x63, 0x68, 0x65, 0x6D, 0x61, 0x90
+
+// roundtrip
+json j_from_bon8 = json::from_bon8(v_bon8);
 ```
 
 The library also supports binary types from BSON, CBOR (byte strings), and MessagePack (bin, ext, fixext). They are stored by default as `std::vector<std::uint8_t>` to be processed outside the library.

cmake/ci.cmake

@@ -300,10 +300,10 @@ add_custom_target(ci_test_skiplibraryversioncheck
 # Disable thread-local storage.
 ###############################################################################
 
-# Without thread-local storage, the copy constructor cannot bound its descent
+# Without thread-local storage, copying and comparing cannot bound their
-# and copies every object and array without the call stack. That path is
+# descent and handle every object and array without the call stack. Those paths
-# otherwise only reached by values nested deeper than the bound, so this target
+# are otherwise only reached by values nested deeper than the bound, so this
-# is what runs the whole test suite through it.
+# target is what runs the whole test suite through them.
 add_custom_target(ci_test_no_thread_local
     COMMAND ${CMAKE_COMMAND}
     -DCMAKE_BUILD_TYPE=Debug -GNinja
@@ -542,7 +542,7 @@ add_custom_target(ci_infer
 
 add_custom_target(ci_offline_testdata
     COMMAND mkdir -p ${PROJECT_BINARY_DIR}/build_offline_testdata/test_data
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_offline_testdata/test_data && ${GIT_TOOL} clone -c advice.detachedHead=false --branch v3.1.0 https://github.com/nlohmann/json_test_data.git --quiet --depth 1
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_offline_testdata/test_data && ${GIT_TOOL} clone -c advice.detachedHead=false --branch v3.2.0 https://github.com/nlohmann/json_test_data.git --quiet --depth 1
     COMMAND ${CMAKE_COMMAND}
         -DCMAKE_BUILD_TYPE=Debug -GNinja
         -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_TestDataDirectory=${PROJECT_BINARY_DIR}/build_offline_testdata/test_data/json_test_data
@@ -619,7 +619,7 @@ add_custom_target(ci_single_binaries
 add_custom_target(ci_benchmarks
     COMMAND ${CMAKE_COMMAND}
         -DCMAKE_BUILD_TYPE=Release -GNinja
-        -S${PROJECT_SOURCE_DIR}/benchmarks -B${PROJECT_BINARY_DIR}/build_benchmarks
+        -S${PROJECT_SOURCE_DIR}/tests/benchmarks -B${PROJECT_BINARY_DIR}/build_benchmarks
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_benchmarks --target json_benchmarks
     COMMAND cd ${PROJECT_BINARY_DIR}/build_benchmarks && ./json_benchmarks
     COMMENT "Run benchmarks"

cmake/download_test_data.cmake

@@ -1,5 +1,5 @@
 set(JSON_TEST_DATA_URL     https://github.com/nlohmann/json_test_data)
-set(JSON_TEST_DATA_VERSION 3.1.0)
+set(JSON_TEST_DATA_VERSION 3.2.0)
 
 include(ExternalProject)
 
@@ -77,7 +77,7 @@ if(CMAKE_CROSSCOMPILING)
 endif()
 if(NOT DEFINED LIBCPP_VERSION_OUTPUT_CACHED)
     try_run(RUN_RESULT_VAR COMPILE_RESULT_VAR
-        "${CMAKE_BINARY_DIR}" SOURCES "${CMAKE_SOURCE_DIR}/cmake/detect_libcpp_version.cpp"
+        "${CMAKE_BINARY_DIR}" SOURCES "${CMAKE_CURRENT_LIST_DIR}/detect_libcpp_version.cpp"
         RUN_OUTPUT_VARIABLE LIBCPP_VERSION_OUTPUT
         COMPILE_OUTPUT_VARIABLE LIBCPP_VERSION_COMPILE_OUTPUT
     )

cmake/scripts/gen_bazel_build_file.cmake

@@ -42,7 +42,6 @@ string(APPEND CONTENT [=[
     ],
     includes = ["include"],
     visibility = ["//visibility:public"],
-    alwayslink = True,
 )
 
 cc_library(

docs/docset/docSet.sql

@@ -48,6 +48,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_bjdata', 'Fu
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_bson', 'Function', 'api/basic_json/from_bson/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_cbor', 'Function', 'api/basic_json/from_cbor/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_msgpack', 'Function', 'api/basic_json/from_msgpack/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_bon8', 'Function', 'api/basic_json/from_bon8/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_ubjson', 'Function', 'api/basic_json/from_ubjson/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::front', 'Method', 'api/basic_json/front/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get', 'Method', 'api/basic_json/get/index.html');
@@ -121,6 +122,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_bjdata', 'Func
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_bson', 'Function', 'api/basic_json/to_bson/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_cbor', 'Function', 'api/basic_json/to_cbor/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_msgpack', 'Function', 'api/basic_json/to_msgpack/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_bon8', 'Function', 'api/basic_json/to_bon8/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_string', 'Method', 'api/basic_json/to_string/index.html');
 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');
@@ -171,6 +173,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats: BJData', 'Gui
 INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats: BSON', 'Guide', 'features/binary_formats/bson/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats: CBOR', 'Guide', 'features/binary_formats/cbor/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats: MessagePack', 'Guide', 'features/binary_formats/messagepack/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats: BON8', 'Guide', 'features/binary_formats/bon8/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats: UBJSON', 'Guide', 'features/binary_formats/ubjson/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('Binary Values', 'Guide', 'features/binary_values/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('Comments', 'Guide', 'features/comments/index.html');

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

@@ -18,7 +18,8 @@ ignore
 :   ignore tags
 
 store
-:   store tagged values as binary container with subtype (for bytes 0xd8..0xdb)
+:   store tagged byte strings (for bytes 0xd8..0xdb) as binary values with the tag as subtype; other tagged values are
+    read as if the tag were ignored. If several tags precede a byte string, only the innermost one is stored.
 
 ## Examples
 

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

@@ -104,6 +104,7 @@ Linear in the size of the input.
 - [from_msgpack](from_msgpack.md) create a JSON value from an input in MessagePack format
 - [from_bson](from_bson.md) create a JSON value from an input in BSON format
 - [from_ubjson](from_ubjson.md) create a JSON value from an input in UBJSON format
+- [from_bon8](from_bon8.md) create a JSON value from an input in BON8 format
 
 ## Version history
 

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

@@ -0,0 +1,108 @@
+# <small>nlohmann::basic_json::</small>from_bon8
+
+```cpp
+// (1)
+template<typename InputType>
+static basic_json from_bon8(InputType&& i,
+                            const bool strict = true,
+                            const bool allow_exceptions = true);
+// (2)
+template<typename IteratorType, typename SentinelType = IteratorType>
+static basic_json from_bon8(IteratorType first, SentinelType last,
+                            const bool strict = true,
+                            const bool allow_exceptions = true);
+```
+
+Deserializes a given input to a JSON value using the BON8 (Binary Object Notation 8) serialization format.
+
+1. Reads from a compatible input.
+2. Reads from an iterator range, or an iterator and a sentinel of a different type (C++20 ranges support).
+
+The exact mapping and its limitations are described on a [dedicated page](../../features/binary_formats/bon8.md).
+
+## Template parameters
+
+`InputType`
+:   A compatible input, for instance:
+
+    - an `std::istream` object
+    - a `FILE` pointer
+    - a C-style array of characters
+    - a pointer to a null-terminated string of single byte characters
+    - a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
+      (as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
+
+`IteratorType`
+:   a compatible iterator type
+
+`SentinelType`
+:   defaults to `IteratorType`; may be a different type comparable to `IteratorType` via `operator!=`, for instance.
+
+    - a custom sentinel type for C++20 ranges
+    - `std::default_sentinel_t`, when `IteratorType` is `std::counted_iterator`
+
+## Parameters
+
+`i` (in)
+:   an input in BON8 format convertible to an input adapter
+
+`first` (in)
+:   iterator to the start of the input
+
+`last` (in)
+:   iterator to the end of the input, or a sentinel value that compares equal to the end iterator with `operator!=`
+
+`strict` (in)
+:   whether to expect the input to be consumed until EOF (`#!cpp true` by default)
+
+`allow_exceptions` (in)
+:   whether to throw exceptions in case of a parse error (optional, `#!cpp true` by default)
+
+## Return value
+
+deserialized JSON value; in case of a parse error and `allow_exceptions` set to `#!cpp false`, the return value will be
+`value_t::discarded`. The latter can be checked with [`is_discarded`](is_discarded.md).
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+## Exceptions
+
+- Throws [parse_error.110](../../home/exceptions.md#jsonexceptionparse_error110) if the given input ends prematurely or
+  the end of the file was not reached when `strict` was set to true
+- Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if a parse error occurs, for instance
+  an invalid byte, a string that is not valid UTF-8, or an object key that is not a string
+
+## Complexity
+
+Linear in the size of the input.
+
+## Examples
+
+??? example
+
+    The example shows the deserialization of a byte vector in BON8 format to a JSON value.
+     
+    ```cpp
+    --8<-- "examples/from_bon8.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/from_bon8.output"
+    ```
+
+## See also
+
+- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value
+- [from_cbor](from_cbor.md) create a JSON value from an input in CBOR format
+- [from_msgpack](from_msgpack.md) create a JSON value from an input in MessagePack format
+- [from_bson](from_bson.md) create a JSON value from an input in BSON format
+- [from_ubjson](from_ubjson.md) create a JSON value from an input in UBJSON format
+- [from_bjdata](from_bjdata.md) create a JSON value from an input in BJData format
+
+## Version history
+
+- Added in version 3.13.0.

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

@@ -104,6 +104,7 @@ Linear in the size of the input.
 - [from_msgpack](from_msgpack.md) for the related MessagePack format
 - [from_ubjson](from_ubjson.md) for the related UBJSON format
 - [from_bjdata](from_bjdata.md) for the related BJData format
+- [from_bon8](from_bon8.md) for the related BON8 format
 
 ## Version history
 

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

@@ -80,8 +80,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   the end of the file was not reached when `strict` was set to true
 - Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if unsupported features from CBOR were
   used in the given input or if the input is not valid CBOR
-- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a string was expected as a map key,
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a map key is not a string (keys of other
-  but not found
+  types are not supported, as JSON object keys are always strings) or a string is malformed
 
 ## Complexity
 
@@ -110,6 +110,7 @@ Linear in the size of the input.
 - [from_bson](from_bson.md) create a JSON value from an input in BSON format
 - [from_ubjson](from_ubjson.md) create a JSON value from an input in UBJSON format
 - [from_bjdata](from_bjdata.md) create a JSON value from an input in BJData format
+- [from_bon8](from_bon8.md) create a JSON value from an input in BON8 format
 
 ## Version history
 

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

@@ -73,8 +73,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   the end of the file was not reached when `strict` was set to true
 - Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if unsupported features from
   MessagePack were used in the given input or if the input is not valid MessagePack
-- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a string was expected as a map key,
+- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a map key is not a string (keys of other
-  but not found
+  types are not supported, as JSON object keys are always strings) or a string is malformed
 
 ## Complexity
 
@@ -103,6 +103,7 @@ Linear in the size of the input.
 - [from_bson](from_bson.md) create a JSON value from an input in BSON format
 - [from_ubjson](from_ubjson.md) create a JSON value from an input in UBJSON format
 - [from_bjdata](from_bjdata.md) create a JSON value from an input in BJData format
+- [from_bon8](from_bon8.md) create a JSON value from an input in BON8 format
 
 ## Version history
 

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

@@ -104,6 +104,7 @@ Linear in the size of the input.
 - [from_msgpack](from_msgpack.md) create a JSON value from an input in MessagePack format
 - [from_bson](from_bson.md) create a JSON value from an input in BSON format
 - [from_bjdata](from_bjdata.md) create a JSON value from an input in BJData format
+- [from_bon8](from_bon8.md) create a JSON value from an input in BON8 format
 
 ## Version history
 

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

@@ -21,6 +21,10 @@ This overload is chosen if:
 - `ValueType` is not `basic_json`,
 - `json_serializer<ValueType>` has a `from_json()` method of the form `void from_json(const basic_json&, ValueType&)`
 
+`v` must not be `const`. Passing a `const` object is a compile-time error. For types such as arithmetic types, enums,
+and C arrays, the error is a `static_assert` that names the problem. For other types, the overload is not viable, and
+the compiler reports that no matching `get_to` was found.
+
 ## Template parameters
 
 `ValueType`
@@ -67,3 +71,4 @@ Depends on the `json_serializer<ValueType>::from_json()` implementation.
 ## Version history
 
 - Since version 3.3.0.
+- Added a `static_assert` with a clear message for `const` arguments in version 3.13.0.

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

@@ -290,11 +290,13 @@ Access to the JSON value
 ### Binary formats
 
 - [**from_bjdata**](from_bjdata.md) (_static_) - create a JSON value from an input in BJData format
+- [**from_bon8**](from_bon8.md) (_static_) - create a JSON value from an input in BON8 format
 - [**from_bson**](from_bson.md) (_static_) - create a JSON value from an input in BSON format
 - [**from_cbor**](from_cbor.md) (_static_) - create a JSON value from an input in CBOR format
 - [**from_msgpack**](from_msgpack.md) (_static_) - create a JSON value from an input in MessagePack format
 - [**from_ubjson**](from_ubjson.md) (_static_) - create a JSON value from an input in UBJSON format
 - [**to_bjdata**](to_bjdata.md) (_static_) - create a BJData serialization of a given JSON value
+- [**to_bon8**](to_bon8.md) (_static_) - create a BON8 serialization of a given JSON value
 - [**to_bson**](to_bson.md) (_static_) - create a BSON serialization of a given JSON value
 - [**to_cbor**](to_cbor.md) (_static_) - create a CBOR serialization of a given JSON value
 - [**to_msgpack**](to_msgpack.md) (_static_) - create a MessagePack serialization of a given JSON value

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

@@ -7,7 +7,8 @@ enum class input_format_t {
     msgpack,
     ubjson,
     bson,
-    bjdata
+    bjdata,
+    bon8
 };
 ```
 
@@ -31,6 +32,9 @@ bson
 bjdata
 :   BJData (Binary JData)
 
+bon8
+:   BON8 (Binary Object Notation 8)
+
 ## Examples
 
 ??? example

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

@@ -5,7 +5,7 @@ class parse_error : public exception;
 ```
 
 The library throws this exception when a parse error occurs. Parse errors can occur during the deserialization of
-JSON text, BSON, CBOR, MessagePack, UBJSON, as well as when using JSON Patch.
+JSON text, BJData, BON8, BSON, CBOR, MessagePack, UBJSON, as well as when using JSON Patch.
 
 Member `byte` holds the byte index of the last read character in the input file (see note below).
 

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

@@ -65,11 +65,14 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
 :   SAX event listener (must not be null)
 
 `format` (in)
-:    the format to parse (JSON, CBOR, MessagePack, or UBJSON) (optional, `input_format_t::json` by default), see
+:    the format to parse (JSON, BJData, BON8, BSON, CBOR, MessagePack, or UBJSON) (optional, `input_format_t::json` by
+     default), see
      [`input_format_t`](input_format_t.md) for more information
 
 `strict` (in)
-:   whether the input has to be consumed completely (optional, `#!cpp true` by default)
+:   whether the input has to be consumed completely (optional, `#!cpp true` by default); when `#!cpp false` and the
+    input is a `#!cpp std::istream`, the character that terminates a number is consumed unless
+    [`JSON_PRECISE_STREAM_POSITION`](../macros/json_precise_stream_position.md) is defined to `1`; see [`operator>>`](../operator_gtgt.md#notes)
 
 `ignore_comments` (in)
 :   whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
@@ -87,7 +90,9 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
 
 ## Return value
 
-return value of the last processed SAX event
+`#!cpp true` if the input was parsed without errors and no SAX event returned `#!cpp false`; `#!cpp false` otherwise.
+In particular, the result is `#!cpp false` for input with errors, even if the SAX parser recovered from all of them
+(see [error recovery](../../features/parsing/error_recovery.md)).
 
 ## Exception safety
 
@@ -135,7 +140,10 @@ A UTF-8 byte order mark is silently ignored.
 - Ignoring comments via `ignore_comments` added in version 3.9.0.
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
+- Recovering from parse errors (see [`parse_error`](../json_sax/parse_error.md)) added 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
+  after the parsed value when `strict` is `#!cpp false`.
 
 !!! warning "Deprecation"
 

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

@@ -84,6 +84,7 @@ Linear in the size of the JSON value `j`.
 - [to_msgpack](to_msgpack.md) create a MessagePack serialization of a JSON value
 - [to_bson](to_bson.md) create a BSON serialization of a JSON value
 - [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
+- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value
 
 ## Version history
 

docs/mkdocs/docs/api/basic_json/to_bon8.md

@@ -0,0 +1,76 @@
+# <small>nlohmann::basic_json::</small>to_bon8
+
+```cpp
+// (1)
+static std::vector<std::uint8_t> to_bon8(const basic_json& j);
+
+// (2)
+static void to_bon8(const basic_json& j, detail::output_adapter<std::uint8_t> o);
+static void to_bon8(const basic_json& j, detail::output_adapter<char> o);
+```
+
+Serializes a given JSON value `j` to a byte vector using the BON8 (Binary Object Notation 8) serialization format. BON8
+is a compact binary serialization format that stores strings as UTF-8 without a length prefix.
+
+1. Returns a byte vector containing the BON8 serialization.
+2. Writes the BON8 serialization to an output adapter.
+
+The exact mapping and its limitations are described on a [dedicated page](../../features/binary_formats/bon8.md).
+
+## Parameters
+
+`j` (in)
+:   JSON value to serialize
+
+`o` (in)
+:   output adapter to write serialization to
+
+## Return value
+
+1. BON8 serialization as a byte vector
+2. (none)
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value `j`, which is never modified.
+With (2), the bytes written before the exception remain in the output adapter.
+
+## Exceptions
+
+- Throws [out_of_range.407](../../home/exceptions.md#jsonexceptionout_of_range407) if `j` contains an unsigned integer
+  above 9223372036854775807, which BON8 cannot represent
+- Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if `j` contains a string that is not
+  valid UTF-8
+
+## Complexity
+
+Linear in the size of the JSON value `j`.
+
+## Examples
+
+??? example
+
+    The example shows the serialization of a JSON value to a byte vector in BON8 format.
+     
+    ```cpp
+    --8<-- "examples/to_bon8.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/to_bon8.output"
+    ```
+
+## See also
+
+- [from_bon8](from_bon8.md) create a JSON value from an input in BON8 format
+- [to_cbor](to_cbor.md) create a CBOR serialization of a JSON value
+- [to_msgpack](to_msgpack.md) create a MessagePack serialization of a JSON value
+- [to_bson](to_bson.md) create a BSON serialization of a JSON value
+- [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
+- [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
+
+## Version history
+
+- Added in version 3.13.0.

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

@@ -46,9 +46,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Complexity
 
-Proportional to the size of the JSON value `j` multiplied by its maximum nesting
+Linear in the size of the JSON value `j`. The length prefixes of all nested documents and arrays are computed in one
-depth, `O(n × d)`. BSON length prefixes are computed recursively before nested
+pass before anything is written.
-values are written.
 
 ## Examples
 
@@ -73,7 +72,9 @@ values are written.
 - [to_msgpack](to_msgpack.md) create a MessagePack serialization of a JSON value
 - [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
 - [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
+- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value
 
 ## Version history
 
 - Added in version 3.4.0.
+- Linear in the size of `j`, and no longer limited by the call stack for deeply nested values, since version 3.13.0.

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

@@ -62,6 +62,7 @@ Linear in the size of the JSON value `j`.
 - [to_bson](to_bson.md) create a BSON serialization of a JSON value
 - [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
 - [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
+- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value
 
 ## Version history
 

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

@@ -34,6 +34,15 @@ The exact mapping and its limitations are described on a [dedicated page](../../
 
 Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
 
+## Exceptions
+
+- Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a string, binary
+  value, array, or object exceeds 4294967295, the maximum MessagePack can store; example:
+  `"MessagePack length 4294967296 exceeds maximum of 4294967295"`
+- Throws [`out_of_range.415`](../../home/exceptions.md#jsonexceptionout_of_range415) if the subtype of a binary value
+  exceeds 255, the maximum of the MessagePack ext type; example:
+  `"subtype 70000 is too large for the MessagePack ext type (max 255)"`
+
 ## Complexity
 
 Linear in the size of the JSON value `j`.
@@ -61,7 +70,9 @@ Linear in the size of the JSON value `j`.
 - [to_bson](to_bson.md) create a BSON serialization of a JSON value
 - [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
 - [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
+- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value
 
 ## Version history
 
 - Added in version 2.0.9.
+- Throws `out_of_range.412` and `out_of_range.415` since version 3.13.0.

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

@@ -77,6 +77,7 @@ Linear in the size of the JSON value `j`.
 - [to_msgpack](to_msgpack.md) create a MessagePack serialization of a JSON value
 - [to_bson](to_bson.md) create a BSON serialization of a JSON value
 - [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
+- [to_bon8](to_bon8.md) create a BON8 serialization of a JSON value
 
 ## Version history
 

docs/mkdocs/docs/api/json_sax/index.md

@@ -7,7 +7,8 @@ struct json_sax;
 
 This class describes the SAX interface used by [sax_parse](../basic_json/sax_parse.md). Each function is called in
 different situations while the input is parsed. The boolean return value informs the parser whether to continue
-processing the input.
+processing the input; for [`parse_error`](parse_error.md), it decides whether to
+[recover from the error](../../features/parsing/error_recovery.md).
 
 ## Template parameters
 

docs/mkdocs/docs/api/json_sax/parse_error.md

@@ -21,7 +21,14 @@ A parse error occurred.
 
 ## Return value
 
-Whether parsing should proceed (**must return `#!cpp false`**).
+Whether to recover from the error:
+
+- `#!cpp false` stops parsing.
+- `#!cpp true` recovers from the error: the error is repaired and parsing continues. If that is not possible, which
+  happens in the binary formats when the end of the item with the error is unknown, the value read so far is completed
+  and parsing stops. See [error recovery](../../features/parsing/error_recovery.md) for how errors are repaired.
+
+Either way, [`sax_parse`](../basic_json/sax_parse.md) returns `#!cpp false`.
 
 ## Examples
 
@@ -39,6 +46,22 @@ Whether parsing should proceed (**must return `#!cpp false`**).
     --8<-- "examples/sax_parse.output"
     ```
 
+??? example
+
+    The example below shows how a SAX parser recovers from errors.
+
+    ```cpp
+    --8<-- "examples/sax_parse__error_recovery.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/sax_parse__error_recovery.output"
+    ```
+
 ## Version history
 
 - Added in version 3.2.0.
+- Returning `#!cpp true` recovers from the error since version 3.13.0; before, parsing stopped, but the result of
+  [`sax_parse`](../basic_json/sax_parse.md) could be wrong.

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

@@ -16,6 +16,8 @@ header. See also the [macro overview page](../../features/macros.md).
 
 ## Parsing
 
+- [**JSON_PRECISE_STREAM_POSITION**](json_precise_stream_position.md) - opt in to leaving an input stream positioned
+  right after a parsed number
 - [**JSON_STRICT_NUL_HANDLING**](json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input instead of
   treating it as end of input
 

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

@@ -7,16 +7,16 @@
 When defined, the library does not use `#!cpp thread_local` storage. This is relevant for the few environments whose
 toolchain does not support it.
 
-The copy constructor copies the first levels of a value by copying the containers, which copy their elements, and
+Copying a value and comparing two values both descend into the first levels by letting the containers copy or compare
-completes whatever is nested deeper than that without the call stack, so that copying a value cannot exhaust the stack
+themselves, and finish whatever is nested deeper than that without the call stack, so that neither can exhaust the stack
-however deeply it is nested. It counts the levels it has descended into in a `#!cpp thread_local` variable, as a counter
+however deeply the values are nested. Each counts the levels it has descended into in a `#!cpp thread_local` variable, as
-shared between threads would be raced.
+a counter shared between threads would be raced.
 
-Without that counter, no descent can be bounded safely, so objects and arrays are copied without the call stack right
+Without those counters, no descent can be bounded safely, so objects and arrays are copied and compared without the call
-away. Copying keeps working exactly as it does otherwise - the same values come out, and deeply nested values are copied
+stack right away. Both keep working exactly as they do otherwise - the same values come out, the same comparisons hold,
-just as safely - but copying is slower, because the containers no longer copy themselves. Copying the benchmark
+and deeply nested values are handled just as safely - but both are slower, because the containers no longer copy or
-documents takes 9% (`canada.json`) to 34% (`twitter.json`) longer; values built mostly from objects are affected the
+compare themselves. Copying the benchmark documents takes 9% (`canada.json`) to 34% (`twitter.json`) longer, and
-most.
+comparing two equal ones 10% (`citm_catalog.json`) to 90% (`canada.json`) longer.
 
 ## Default definition
 
@@ -28,6 +28,7 @@ By default, `#!cpp JSON_NO_THREAD_LOCAL` is not defined.
 
 The library defines it by itself for Clang targeting MinGW, which does not survive the `#!cpp thread_local` storage:
 copying a value segfaults there, with both old and current Clang versions, while GCC targeting MinGW is unaffected.
+Copying and comparing fall back to working without the call stack there, as they do whenever the macro is defined.
 
 ## Examples
 

docs/mkdocs/docs/api/macros/json_precise_stream_position.md

@@ -0,0 +1,131 @@
+# JSON_PRECISE_STREAM_POSITION
+
+```cpp
+#define JSON_PRECISE_STREAM_POSITION /* value */
+```
+
+When defined to `1`, [`operator>>`](../operator_gtgt.md) and [`sax_parse`](../basic_json/sax_parse.md) with
+`strict = false` leave a `#!cpp std::istream` positioned right after the parsed value for every value type. By default,
+the character that terminates a number is consumed as well.
+
+The macro only affects reading from a `#!cpp std::istream` when the rest of the stream is not required to be consumed.
+[`parse`](../basic_json/parse.md), [`accept`](../basic_json/accept.md), and all other inputs (strings, iterators,
+containers, `#!cpp FILE*`) are never affected.
+
+## Default definition
+
+The default value is `0` (disabled — existing behavior is preserved).
+
+```cpp
+#define JSON_PRECISE_STREAM_POSITION 0
+```
+
+## Notes
+
+!!! note "Background"
+
+    A number is the only JSON value whose end can be detected solely by reading the character that follows it. By
+    default, that character is consumed and not put back, so the stream is left one byte too far after a number, and
+    only after a number:
+
+    ```cpp
+    std::istringstream input("1true");
+    json j;
+    input >> j;  // j == 1, but the stream now starts at "rue"
+    ```
+
+    With this macro, the character is only looked at and left in the stream, so the stream starts at `true`. This
+    does not require the stream buffer to support putting a character back.
+
+    This was not changed unconditionally, because code can depend on the consumed character, even unknowingly (see
+    [#5340](https://github.com/nlohmann/json/issues/5340)). Both of the following work by default only because the
+    character after each number is swallowed, and behave differently with this macro:
+
+    ```cpp
+    std::istringstream input("1,2,3");
+    json j1, j2, j3;
+    input >> j1 >> j2 >> j3;  // default: 1, 2, 3
+                              // with the macro: throws parse_error.101 at the ','
+    ```
+
+    ```cpp
+    std::istringstream input("42\nfoo");
+    json j;
+    std::string line;
+    input >> j;
+    std::getline(input, line);  // default: "foo"
+                                // with the macro: "" (like after reading an int with >>)
+    ```
+
+    In both cases, the behavior with the macro is what you already get today when the value is not a number: `"a","b"`
+    fails at the `,`, and `std::getline` after `{}` returns an empty string. This macro offers an opt-in path to
+    the consistent behavior ahead of version 4.0.0, where it is planned to become the default.
+
+!!! warning "Opt-in only"
+
+    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
+    effect.
+
+!!! note "ABI compatibility"
+
+    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_psp`), resulting in
+    distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
+    without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
+
+!!! tip "Workaround without the macro"
+
+    Separate the values in the stream with whitespace. The character consumed after a number is then the separator,
+    and whitespace before the next value is skipped anyway.
+
+## Examples
+
+??? example "Default behavior (macro not defined)"
+
+    Without the macro, the character after a number is consumed:
+
+    ```cpp
+    #include <iostream>
+    #include <sstream>
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        std::istringstream input("1true");
+        json j1, j2;
+        input >> j1;  // j1 == 1
+        input >> j2;  // throws parse_error.101: the stream now starts at "rue"
+    }
+    ```
+
+??? example "Opt-in precise stream position (macro defined to 1)"
+
+    With the macro, the stream is positioned right after the number:
+
+    ```cpp
+    #define JSON_PRECISE_STREAM_POSITION 1
+    #include <iostream>
+    #include <sstream>
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        std::istringstream input("1true");
+        json j1, j2;
+        input >> j1;  // j1 == 1
+        input >> j2;  // j2 == true
+    }
+    ```
+
+## See also
+
+- [**operator>>**](../operator_gtgt.md) - deserialize from stream
+- [**sax_parse**](../basic_json/sax_parse.md) - generate SAX events
+
+## 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_strict_nul_handling.md

@@ -11,9 +11,9 @@ The macro only affects the JSON text parser ([`parse`](../basic_json/parse.md),
 [`sax_parse`](../basic_json/sax_parse.md), and [`operator>>`](../operator_gtgt.md)). There are three cases where a NUL
 byte is still not rejected:
 
-- The binary formats ([`from_bjdata`](../basic_json/from_bjdata.md), [`from_bson`](../basic_json/from_bson.md),
+- The binary formats ([`from_bjdata`](../basic_json/from_bjdata.md), [`from_bon8`](../basic_json/from_bon8.md),
-  [`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
+  [`from_bson`](../basic_json/from_bson.md), [`from_cbor`](../basic_json/from_cbor.md),
-  [`from_ubjson`](../basic_json/from_ubjson.md)) are never affected: there, `0x00` is ordinary data.
+  [`from_msgpack`](../basic_json/from_msgpack.md), [`from_ubjson`](../basic_json/from_ubjson.md)) are never affected: there, `0x00` is ordinary data.
 - A bare `const char*` pointer has no length of its own, so its length is still determined with `strlen()`. The first
   NUL byte therefore still marks the end of the input, and nothing after it is read.
 - One trailing `'\0'` at the end of a `char` array (e.g., a string literal) is trimmed; see the warning below.
@@ -65,6 +65,12 @@ The default value is `0` (disabled — existing behavior is preserved).
     for CBOR or MessagePack, are never affected by this trimming; their full extent - including a genuine trailing
     `0x00` - is always preserved, in both states of this macro.
 
+!!! note "ABI compatibility"
+
+    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_snul`), resulting in
+    distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
+    without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
+
 !!! tip "Workaround without the macro"
 
     To reject a NUL byte without enabling this macro, trim your input yourself before calling `parse()`:

docs/mkdocs/docs/api/macros/nlohmann_define_derived_type.md

@@ -57,7 +57,8 @@ Summary:
 :   name of the base type (class, struct) `type` is derived from
 
 `member` (in)
-:   name of the member variable to serialize/deserialize; up to 63 members can be given as a comma-separated list
+:   name of the member variable to serialize/deserialize; up to 63 members can be given as a comma-separated
+    list, which may also be empty
 
 ## Default definition
 
@@ -127,6 +128,20 @@ void to_json(BasicJsonType& j, const B& b) {
     - Macros 4, 5, and 6 have the same prerequisites of [NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE](nlohmann_define_type_non_intrusive.md).
     - Serialization/deserialization of base types must be defined.
 
+!!! info "Derived types without own members"
+
+    The member list may be empty. The macro then generates a `to_json`/`from_json` pair that only delegates to
+    the base type, so `type` serializes exactly like `base_type`:
+
+    ```cpp
+    struct derived : base
+    {
+        NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE(derived, base)
+    };
+    ```
+
+    The `WITH_NAMES` variants do not support this.
+
 !!! warning "Implementation limits"
 
     See Implementation limits for [NLOHMANN_DEFINE_TYPE_INTRUSIVE](nlohmann_define_type_intrusive.md) and

docs/mkdocs/docs/api/macros/nlohmann_define_type_intrusive.md

@@ -33,7 +33,8 @@ Summary:
 :   name of the type (class, struct) to serialize/deserialize
 
 `member` (in)
-:   name of the member variable to serialize/deserialize; up to 63 members can be given as a comma-separated list
+:   name of the member variable to serialize/deserialize; up to 63 members can be given as a comma-separated
+    list, which may also be empty
 
 ## Default definition
 
@@ -58,6 +59,20 @@ See the examples below for the concrete generated code.
 
 [GetNonDefNonCopy]: ../../features/arbitrary_types.md#how-can-i-use-get-for-non-default-constructiblenon-copyable-types
 
+!!! info "Types without members"
+
+    The member list may be empty. The macro then generates a `to_json` that produces an empty JSON object
+    `#!json {}`, and a `from_json` that reads no members:
+
+    ```cpp
+    struct marker
+    {
+        NLOHMANN_DEFINE_TYPE_INTRUSIVE(marker)
+    };
+    ```
+
+    The `WITH_NAMES` variants do not support this.
+
 !!! warning "Implementation limits"
 
     - The current implementation is limited to at most 63 member variables. If you want to serialize/deserialize types

docs/mkdocs/docs/api/macros/nlohmann_define_type_non_intrusive.md

@@ -33,7 +33,8 @@ Summary:
 :   name of the type (class, struct) to serialize/deserialize
 
 `member` (in)
-:   name of the (public) member variable to serialize/deserialize; up to 63 members can be given as a comma-separated list
+:   name of the (public) member variable to serialize/deserialize; up to 63 members can be given as a
+    comma-separated list, which may also be empty
 
 ## Default definition
 
@@ -59,6 +60,18 @@ See the examples below for the concrete generated code.
 
 [GetNonDefNonCopy]: ../../features/arbitrary_types.md#how-can-i-use-get-for-non-default-constructiblenon-copyable-types
 
+!!! info "Types without members"
+
+    The member list may be empty. The macro then generates a `to_json` that produces an empty JSON object
+    `#!json {}`, and a `from_json` that reads no members:
+
+    ```cpp
+    struct marker {};
+    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(marker)
+    ```
+
+    The `WITH_NAMES` variants do not support this.
+
 !!! warning "Implementation limits"
 
     - The current implementation is limited to at most 63 member variables. If you want to serialize/deserialize types

docs/mkdocs/docs/api/operator_gtgt.md

@@ -67,7 +67,9 @@ input >> j2;  // parses the next value
     Only numbers are affected. Values ending in a self-delimiting character do not read past themselves, so
     `truefalse`, `[1][2]`, `{"a":1}{"b":2}`, and `"a""b"` can be read back to back without a separator.
 
-    This is tracked in [#5340](https://github.com/nlohmann/json/issues/5340).
+    Define [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) to `1` to leave the terminating character in the stream
+    instead, so that the stream is positioned right after the value for every value type and no separator is
+    needed. This is tracked in [#5340](https://github.com/nlohmann/json/issues/5340).
 
 Note that reading concatenated values does **not** work for [JSON Lines](../features/parsing/json_lines.md)
 (newline-delimited JSON) input -- see that page for why and for the recommended alternative.
@@ -107,9 +109,12 @@ being read.
 - [parse](basic_json/parse.md) - deserialize from a compatible input
 - [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
   instead of treating it as end of input
+- [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) - opt in to leaving the stream positioned right after a number
 
 ## Version history
 
 - Added in version 1.0.0.
 - `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
   it as end of input; planned to become the default in version 4.0.0.
+- `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave the character that terminates a number in
+  the stream; planned to become the default in version 4.0.0.

docs/mkdocs/docs/community/assurance_case.md

@@ -0,0 +1,70 @@
+# Assurance case
+
+This page argues why the library meets its security requirements. It describes the threats the library faces, where the
+trust boundaries lie, and how the library's design and the [quality assurance](quality_assurance.md) counter these
+threats. To report a vulnerability, see the [security policy](security_policy.md).
+
+## Threat model
+
+The library parses, stores, and serializes JSON values in memory. It does not open network connections, does not open
+files (it only reads from streams or `std::FILE*` handles that the caller has already opened), does not read environment
+variables, and does not implement cryptography or handle credentials.
+
+The primary threat is therefore **untrusted input**: JSON text or binary data (BJData, BSON, CBOR, MessagePack, UBJSON)
+that an attacker controls, passed to [`parse`](../api/basic_json/parse.md), [`accept`](../api/basic_json/accept.md),
+[`sax_parse`](../api/basic_json/sax_parse.md), or one of the `from_*` functions such as
+[`from_cbor`](../api/basic_json/from_cbor.md). Such input may try to
+
+- make the library read or write out of bounds (malformed lengths, truncated input, invalid UTF-8),
+- trigger undefined behavior (integer overflow in sizes or numbers, invalid casts),
+- exhaust memory (huge announced sizes), or
+- exhaust the call stack (deeply nested arrays and objects).
+
+## Trust boundaries
+
+- **Untrusted:** all serialized input read by the parser, the SAX interface, and the binary readers. The library must
+  handle every possible input by either producing a value or throwing a [`parse_error`](../home/exceptions.md#parse-errors)
+  (or returning `false` when exceptions are disabled for the call).
+- **Trusted:** the C++ code that calls the library. Calling a function with violated preconditions, for instance
+  accessing an array with [`operator[]`](../api/basic_json/operator%5B%5D.md) out of range, is a programming error and
+  not a security boundary. Such preconditions are checked with [runtime assertions](../features/assertions.md) in debug
+  builds; functions such as [`at`](../api/basic_json/at.md) offer checked access with exceptions.
+
+## Secure design
+
+- **Strict parsing.** The parser accepts exactly the JSON grammar of [RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259).
+  Extensions such as [comments](../features/comments.md) and [trailing commas](../features/trailing_commas.md) must be
+  enabled explicitly. Invalid UTF-8 is rejected.
+- **Errors are reported, not ignored.** Malformed input results in a [`parse_error`](../home/exceptions.md#parse-errors)
+  with the byte position of the error. Binary readers do not trust announced sizes: strings and binary values grow
+  only as bytes are actually read, arrays reserve at most a fixed number of elements up front, and sizes that no
+  container can hold are rejected.
+- **Memory is owned by values.** Each `basic_json` value owns its content, and there is no manual memory management in
+  user code. The destructor does not recurse, so destroying a deeply nested value does not exhaust the stack.
+- **Bounded recursion.** The JSON parser and the binary readers keep their state in explicit stacks instead of
+  recursing per nesting level. Operations that walk a value, such as [`dump`](../api/basic_json/dump.md), copying,
+  comparison, hashing, and [`merge_patch`](../api/basic_json/merge_patch.md), recurse only up to a fixed depth and
+  continue with an explicit stack below it. Some operations, such as [`diff`](../api/basic_json/diff.md),
+  [`flatten`](../api/basic_json/flatten.md), and the binary writers, still recurse once per nesting level; work on them
+  is in progress. Applications that process untrusted input can limit its nesting depth with a
+  [parser callback](../features/parsing/parser_callbacks.md).
+- **Invariants are checked.** The class invariant (for instance, that the pointer for the stored type is never null) is
+  checked with runtime assertions throughout the test suite.
+
+## Common weaknesses
+
+The following table maps the relevant classes of the [Common Weakness Enumeration](https://cwe.mitre.org) to the
+measures that counter them. The measures are described in detail in [Quality assurance](quality_assurance.md).
+
+| Weakness                                                                  | Countermeasures                                                                                  |
+|---------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|
+| Out-of-bounds read/write ([CWE-125](https://cwe.mitre.org/data/definitions/125.html), [CWE-787](https://cwe.mitre.org/data/definitions/787.html)) | bounds checks on all reads from the input; AddressSanitizer and Valgrind on the test suite; OSS-Fuzz      |
+| Integer overflow ([CWE-190](https://cwe.mitre.org/data/definitions/190.html)) | UndefinedBehaviorSanitizer with integer overflow detection; Clang-Tidy; Cppcheck                 |
+| Use after free, double free ([CWE-416](https://cwe.mitre.org/data/definitions/416.html), [CWE-415](https://cwe.mitre.org/data/definitions/415.html)) | ownership of all memory by values; AddressSanitizer and Valgrind; Clang Static Analyzer          |
+| Memory leaks ([CWE-401](https://cwe.mitre.org/data/definitions/401.html)) | Valgrind (Memcheck) on the test suite                                                            |
+| Uncontrolled recursion ([CWE-674](https://cwe.mitre.org/data/definitions/674.html)) | iterative parser, binary readers, and destructor; bounded recursion in value operations; tests with deeply nested inputs |
+| Uncontrolled resource consumption ([CWE-400](https://cwe.mitre.org/data/definitions/400.html)) | allocations based on announced sizes are capped; OSS-Fuzz with memory limits                     |
+| Undefined behavior in general ([CWE-758](https://cwe.mitre.org/data/definitions/758.html)) | UndefinedBehaviorSanitizer; runtime assertions; Clang-Tidy, Cppcheck, Clang Static Analyzer, Infer |
+
+In addition, every line of the library is covered by the unit tests, and all parsers are fuzz-tested around the clock
+by [OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json).

docs/mkdocs/docs/community/governance.md

@@ -91,6 +91,31 @@ activities include (but are not limited to):
 Users who continue to engage with the project and its community will often find themselves becoming more and more
 involved. Such users may then go on to become contributors, as described above.
 
+## Access to project resources
+
+The project's resources are the [GitHub repository](https://github.com/nlohmann/json) with its settings, CI workflows
+and secrets, and the documentation at [json.nlohmann.me](https://json.nlohmann.me), which is built and deployed from
+the repository. Currently, the project lead is the only person with write or admin access to them.
+
+### Granting access
+
+Write or admin access is only granted by the project lead, and only to a contributor whose track record in the project
+the project lead has reviewed first. The role is assigned manually and is the lowest one that is needed for the task.
+Access is removed when it is no longer needed. GitHub requires two-factor authentication for everyone who can modify the
+repository.
+
+### Secrets
+
+The CI workflows mostly use the token that GitHub creates for each workflow run. It is read-only by default, and each
+workflow requests only the additional permissions it needs. The few other credentials, such as the token for
+[Semgrep](https://semgrep.dev), are stored as encrypted GitHub Actions secrets:
+
+- Only people with admin access can create, change, or delete them. Their values cannot be read back, not even by
+  admins.
+- They are not passed to workflows that run for pull requests from forks.
+- They must never be committed to the repository or printed in logs.
+- They are rotated whenever someone with admin access leaves the project, and immediately if a leak is suspected.
+
 ## Support
 
 All participants in the community are encouraged to provide support for new users within the project management

docs/mkdocs/docs/community/index.md

@@ -5,4 +5,6 @@
 - [Contribution Guidelines](contribution_guidelines.md) - guidelines how to contribute to this project
 - [Governance](governance.md) - the governance model of this project
 - [Quality Assurance](quality_assurance.md) - how the quality of this project is assured
+- [Roadmap](roadmap.md) - what the project will and will not do
 - [Security Policy](security_policy.md) - the security policy of the project
+- [Assurance Case](assurance_case.md) - why the library meets its security requirements

docs/mkdocs/docs/community/quality_assurance.md

@@ -164,6 +164,9 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
 - [x] The parser is tested against extensive correctness suites for JSON compliance.
 - [x] In addition, the library is continuously fuzz-tested at [OSS-Fuzz](https://google.github.io/oss-fuzz/) where the
   library is checked against billions of inputs.
+- [x] Every crash reported by OSS-Fuzz is fixed together with a unit test that reproduces it, and the fix references
+  the OSS-Fuzz issue. The round-trip checks of the fuzzer drivers are also part of the unit tests. See the
+  [fuzz testing documentation](https://github.com/nlohmann/json/blob/develop/tests/fuzzing.md#handling-oss-fuzz-reports).
 
 ## Static analysis
 
@@ -197,6 +200,25 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
 - [x] The test suite is executed with [Sanitizers](https://github.com/google/sanitizers) (address sanitizer, undefined
   behavior sanitizer, integer overflow detection, nullability violations).
 
+## Dependencies
+
+!!! success "Requirement: No vulnerable dependencies"
+
+    The library has no dependencies besides the C++ standard library. The tools used to build, test, and document it
+    are kept free of known vulnerabilities.
+
+- [x] GitHub Actions are pinned to a commit hash, and the Python packages used by the documentation and the tools are
+  pinned to exact versions.
+- [x] [Dependabot](https://docs.github.com/en/code-security/dependabot) checks these dependencies daily and proposes
+  updates as pull requests.
+- [x] Every pull request is checked with the
+  [dependency review action](https://github.com/actions/dependency-review-action). A pull request that adds a
+  dependency with a known vulnerability of any severity fails this check and is not merged.
+- [x] Vulnerability alerts for dependencies are fixed or dismissed with a documented reason before the next release.
+  No release is made while such an alert is open.
+- [x] Third-party code included in the repository for testing, such as [doctest](https://github.com/doctest/doctest),
+  is updated manually.
+
 ## Style check
 
 !!! success "Requirement: Common code style"

docs/mkdocs/docs/community/roadmap.md

@@ -0,0 +1,43 @@
+# Roadmap
+
+This page describes what the project intends to do, and what it does not intend to do, over the next year. Concrete
+work items are tracked in the [GitHub milestones](https://github.com/nlohmann/json/milestones) and the
+[issue tracker](https://github.com/nlohmann/json/issues).
+
+## What the project will do
+
+- **Keep the C++11 baseline.** The library will continue to compile with every
+  [supported C++11 compiler](https://github.com/nlohmann/json/blob/develop/README.md#supported-compilers). Features of
+  later standards are only used when they are guarded by the `JSON_HAS_CPP_*` macros.
+- **Stay conformant to JSON.** The parser and serializer follow [RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259).
+  Extensions such as [comments](../features/comments.md) or [trailing commas](../features/trailing_commas.md) remain
+  opt-in.
+- **Keep the 3.x public API stable.** Releases follow [semantic versioning](https://semver.org). Changes that would
+  break existing code are only added behind a feature macro, so users can opt in and test their code before a next
+  major release.
+- **Support a broad range of compilers and platforms.** The [CI](quality_assurance.md) keeps testing old and new
+  versions of GCC, Clang, MSVC, and other compilers on Linux, macOS, and Windows.
+- **Keep the quality assurance up.** Every change keeps the test coverage at 100%, passes the static and dynamic
+  analysis, and is fuzz-tested by OSS-Fuzz, see [Quality assurance](quality_assurance.md).
+- **Harden the library against hostile input.** Handling deeply nested values without exhausting the call stack is
+  ongoing work.
+- **Fix bugs and security issues** reported through the issue tracker and the [security policy](security_policy.md).
+
+## What the project will not do
+
+- **Break the public API of version 3.x.** See the
+  [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
+  `json.hpp` remains a complete distribution.
+- **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).
+
+## Version 4.0
+
+There is no decision yet on whether or when a version 4.0 with breaking changes will be released. Proposals that need
+a major version, for instance stricter type conversions, are collected in issue
+[#3453](https://github.com/nlohmann/json/issues/3453). Until then, such changes are only added as opt-in behavior
+behind feature macros.

docs/mkdocs/docs/examples/from_bon8.cpp

@@ -0,0 +1,21 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create byte vector
+    std::vector<std::uint8_t> v = {0x89, 0x63, 0x6f, 0x6d, 0x70, 0x61, 0x63, 0x74,
+                                   0xf9, 0x66, 0x6f, 0x72, 0x6d, 0x61, 0x74, 0xff,
+                                   0x42, 0x4f, 0x4e, 0x38, 0xff, 0x73, 0x63, 0x68,
+                                   0x65, 0x6d, 0x61, 0x90
+                                  };
+
+    // deserialize it with BON8
+    json j = json::from_bon8(v);
+
+    // print the deserialized JSON value
+    std::cout << std::setw(2) << j << std::endl;
+}

docs/mkdocs/docs/examples/from_bon8.output

@@ -0,0 +1,5 @@
+{
+  "compact": true,
+  "format": "BON8",
+  "schema": 0
+}

docs/mkdocs/docs/examples/sax_parse__error_recovery.cpp

@@ -0,0 +1,43 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// a SAX parser that creates a JSON value like json::parse does, but that
+// recovers from parse errors instead of stopping at the first one
+class recovering_parser : public nlohmann::detail::json_sax_dom_parser<json>
+{
+  public:
+    explicit recovering_parser(json& result)
+        : nlohmann::detail::json_sax_dom_parser<json>(result, false)
+    {}
+
+    bool parse_error(std::size_t position,
+                     const std::string& /*last_token*/,
+                     const json::exception& ex)
+    {
+        std::cout << "byte " << position << ": " << ex.what() << '\n';
+
+        // repair the input and continue
+        return true;
+    }
+};
+
+int main()
+{
+    // JSON text with several mistakes that ends too early
+    const std::string text = R"({
+    "name": "Hello World",
+    "tags": ["a" "b",],
+    "valid": tru,
+    "size": 1.,
+    "nested": {"x": 1)";
+
+    json result;
+    recovering_parser sax(result);
+    const bool valid = json::sax_parse(text, &sax);
+
+    std::cout << "\nvalid JSON: " << std::boolalpha << valid << '\n'
+              << std::setw(4) << result << std::endl;
+}

docs/mkdocs/docs/examples/sax_parse__error_recovery.output

@@ -0,0 +1,19 @@
+byte 49: [json.exception.parse_error.101] parse error at line 3, column 20: syntax error while parsing array - unexpected string literal; expected ']'
+byte 51: [json.exception.parse_error.101] parse error at line 3, column 22: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+byte 70: [json.exception.parse_error.101] parse error at line 4, column 17: syntax error while parsing value - invalid literal; last read: '"valid": tru,'
+byte 86: [json.exception.parse_error.101] parse error at line 5, column 15: syntax error while parsing value - invalid number; expected digit after '.'; last read: '1.,'
+byte 109: [json.exception.parse_error.101] parse error at line 6, column 22: syntax error while parsing object - unexpected end of input; expected '}'
+
+valid JSON: false
+{
+    "name": "Hello World",
+    "nested": {
+        "x": 1
+    },
+    "size": 1,
+    "tags": [
+        "a",
+        "b"
+    ],
+    "valid": null
+}

docs/mkdocs/docs/examples/to_bon8.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    // create a JSON value
+    json j = R"({"compact": true, "format": "BON8", "schema": 0})"_json;
+
+    // serialize it to BON8
+    std::vector<std::uint8_t> v = json::to_bon8(j);
+
+    // print the vector content
+    for (auto& byte : v)
+    {
+        std::cout << "0x" << std::hex << std::setw(2) << std::setfill('0') << (int)byte << " ";
+    }
+    std::cout << std::endl;
+}

docs/mkdocs/docs/examples/to_bon8.output

@@ -0,0 +1 @@
+0x89 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0xf9 0x66 0x6f 0x72 0x6d 0x61 0x74 0xff 0x42 0x4f 0x4e 0x38 0xff 0x73 0x63 0x68 0x65 0x6d 0x61 0x90 

docs/mkdocs/docs/features/arbitrary_types.md

@@ -215,6 +215,24 @@ For _derived_ classes and structs, use the following macros
     nlohmann::ordered_json j = p; // keys appear in declaration order: name, address, age
     ```
 
+!!! note "Zero-member types"
+
+    All 12 `NLOHMANN_DEFINE_TYPE_*`/`NLOHMANN_DEFINE_DERIVED_TYPE_*` macros (excluding the `WITH_NAMES` variants)
+    also accept types with no member variables to serialize, producing/accepting an empty JSON object `{}`
+    (or, for the derived-type macros, just the base class's own JSON representation):
+
+    ```cpp
+    namespace ns {
+        struct marker {
+            bool operator==(const marker&) const { return true; }
+            NLOHMANN_DEFINE_TYPE_INTRUSIVE(marker)
+        };
+    }
+
+    ns::marker m{};
+    nlohmann::json j = m; // {}
+    ```
+
 !!! note "No macro for non-default-constructible types"
 
     There is currently no `NLOHMANN_DEFINE_TYPE_*`-style macro for types that are not

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

@@ -208,6 +208,16 @@ The library maps BJData types to JSON value types as follows:
 
     The mapping is **complete** in the sense that any BJData value can be converted to a JSON value.
 
+!!! info "Round trips"
+
+    A value returned by [`from_bjdata`](../../api/basic_json/from_bjdata.md) can be serialized with
+    [`to_bjdata`](../../api/basic_json/to_bjdata.md) using any combination of options and parsed back into an equal
+    value, and serializing that value again with the same options produces the same bytes. The exception is binary
+    values: they are only written as an optimized binary array (`[$B`) if Draft 3 is enabled and both `use_size` and
+    `use_type` are set. Otherwise, they are written as arrays of integers and parsed back as such (see the notes on
+    binary values above), and serializing such an array again may choose different, but equally valid, type markers.
+    The bytes can then differ, but parsing them again yields the same value.
+
 ??? example
 
     ```cpp

docs/mkdocs/docs/features/binary_formats/bon8.md

@@ -0,0 +1,159 @@
+# BON8
+
+BON8 (Binary Object Notation 8) is a compact binary serialization format for JSON values. It uses the byte values that
+cannot begin a UTF-8 character as type markers, so strings are stored as plain UTF-8 without a length prefix: a string
+ends at the first byte that cannot continue it. Integers from -10 to 39, `true`, `false`, `null`, and the floating-point
+values -1.0, 0.0, and 1.0 take a single byte, and arrays and objects with up to four elements need no terminator.
+
+!!! abstract "References"
+
+    - [BON8 specification](https://github.com/hikoworks/hikogui/blob/main/docs/BON8.md)
+    - [Reference implementation](https://github.com/hikoworks/hikogui/blob/main/src/hikogui/codec/BON8.hpp) in HikoGUI
+
+## Serialization
+
+The library uses the following mapping from JSON values types to BON8 types according to the BON8 specification:
+
+| JSON value type | value/range                                  | BON8 type                     | first byte |
+|-----------------|----------------------------------------------|-------------------------------|------------|
+| null            | `null`                                       | null                          | 0xFA       |
+| boolean         | `true`                                       | true                          | 0xF9       |
+| boolean         | `false`                                      | false                         | 0xF8       |
+| number_integer  | -9223372036854775808..-2147483649            | int64                         | 0x8D       |
+| number_integer  | -2147483648..-33818507                       | int32                         | 0x8C       |
+| number_integer  | -33818506..-264075                           | 4-byte negative integer       | 0xF0..0xF7 |
+| number_integer  | -264074..-1931                               | 3-byte negative integer       | 0xE0..0xEF |
+| number_integer  | -1930..-11                                   | 2-byte negative integer       | 0xC2..0xDF |
+| number_integer  | -10..-1                                      | 1-byte negative integer       | 0xB8..0xC1 |
+| number_integer  | 0..39                                        | 1-byte positive integer       | 0x90..0xB7 |
+| number_integer  | 40..3879                                     | 2-byte positive integer       | 0xC2..0xDF |
+| number_integer  | 3880..528167                                 | 3-byte positive integer       | 0xE0..0xEF |
+| number_integer  | 528168..67637031                             | 4-byte positive integer       | 0xF0..0xF7 |
+| number_integer  | 67637032..2147483647                         | int32                         | 0x8C       |
+| number_integer  | 2147483648..9223372036854775807              | int64                         | 0x8D       |
+| number_unsigned | 0..39                                        | 1-byte positive integer       | 0x90..0xB7 |
+| number_unsigned | 40..3879                                     | 2-byte positive integer       | 0xC2..0xDF |
+| number_unsigned | 3880..528167                                 | 3-byte positive integer       | 0xE0..0xEF |
+| number_unsigned | 528168..67637031                             | 4-byte positive integer       | 0xF0..0xF7 |
+| number_unsigned | 67637032..2147483647                         | int32                         | 0x8C       |
+| number_unsigned | 2147483648..9223372036854775807              | int64                         | 0x8D       |
+| number_float    | `-1.0`                                       | -1.0                          | 0xFB       |
+| number_float    | `0.0`                                        | 0.0                           | 0xFC       |
+| number_float    | `1.0`                                        | 1.0                           | 0xFD       |
+| number_float    | *any other value representable by a float*   | binary32                      | 0x8E       |
+| number_float    | *any value NOT representable by a float*     | binary64                      | 0x8F       |
+| string          | *empty*                                      | end of string                 | 0xFF       |
+| string          | *non-empty*                                  | UTF-8 string                  | 0x00..0x7F, 0xC2..0xF4 |
+| array           | *size*: 0..4                                 | array with count              | 0x80..0x84 |
+| array           | *size*: 5 or more                            | array (terminated by 0xFE)    | 0x85       |
+| object          | *size*: 0..4                                 | object with count             | 0x86..0x8A |
+| object          | *size*: 5 or more                            | object (terminated by 0xFE)   | 0x8B       |
+| binary          | *size*: 0..4                                 | array with count              | 0x80..0x84 |
+| binary          | *size*: 5 or more                            | array (terminated by 0xFE)    | 0x85       |
+
+An integer that takes 2 to 4 bytes starts with a UTF-8 lead byte (0xC2..0xF7) that is followed by a byte that cannot
+continue a UTF-8 character: 0x00..0x7F for positive and 0xC0..0xFF for negative integers. A string is terminated by
+0xFF only if it is empty, if another string follows it, or if it is the last value of the message; otherwise, the first
+byte of the next value ends it.
+
+!!! success "Complete mapping"
+
+    Except for the values listed below, any JSON value can be converted to a BON8 value.
+
+    Any BON8 output created by `to_bon8` can be successfully parsed by `from_bon8`.
+
+!!! warning "Unsupported values"
+
+    The following values can **not** be converted to a BON8 value:
+
+      - unsigned integers above 9223372036854775807, because BON8 has no unsigned 64-bit integer type
+        ([out_of_range.407](../../home/exceptions.md#jsonexceptionout_of_range407))
+      - strings that are not valid UTF-8, because the end of a string is determined from its encoding
+        ([type_error.316](../../home/exceptions.md#jsonexceptiontype_error316))
+
+!!! info "NaN/infinity handling"
+
+    `-0.0`, `Infinity`, and `-Infinity` are serialized as binary32 (type 0x8E, 5 bytes total). `NaN` is serialized as
+    the binary32 value 0x7F800001 that the specification recommends. This is in contrast to the
+    [dump](../../api/basic_json/dump.md) function which serializes NaN or Infinity to `null`.
+
+!!! warning "Binary values"
+
+    BON8 has no binary type. Binary values are serialized as arrays of integers (0..255), so they are read back as
+    arrays. The subtype is not serialized.
+
+!!! info "Canonical representation"
+
+    The output follows the specification's canonical representation rules: every value uses the shortest encoding,
+    floating-point numbers use binary32 whenever that loses no precision, and object keys are sorted by their UTF-8
+    code units. There are two exceptions:
+
+    - Strings are not normalized to Unicode Normalization Form C (NFC).
+    - Object keys are written in the order of the object type, which is sorted for `json`, but not for
+      [`ordered_json`](../../api/ordered_json.md).
+
+??? example
+
+    ```cpp
+    --8<-- "examples/to_bon8.cpp"
+    ```
+
+    Output:
+
+    ```c
+    --8<-- "examples/to_bon8.output"
+    ```
+
+## Deserialization
+
+The library maps BON8 types to JSON value types as follows:
+
+| BON8 type                     | JSON value type | first byte             |
+|-------------------------------|-----------------|------------------------|
+| UTF-8 string                  | string          | 0x00..0x7F             |
+| array with count              | array           | 0x80..0x84             |
+| array (terminated by 0xFE)    | array           | 0x85                   |
+| object with count             | object          | 0x86..0x8A             |
+| object (terminated by 0xFE)   | object          | 0x8B                   |
+| int32                         | number_unsigned or number_integer | 0x8C |
+| int64                         | number_unsigned or number_integer | 0x8D |
+| binary32                      | number_float    | 0x8E                   |
+| binary64                      | number_float    | 0x8F                   |
+| 1-byte positive integer       | number_unsigned | 0x90..0xB7             |
+| 1-byte negative integer       | number_integer  | 0xB8..0xC1             |
+| UTF-8 string                  | string          | 0xC2..0xF4, followed by 0x80..0xBF |
+| 2- to 4-byte positive integer | number_unsigned | 0xC2..0xF7, followed by 0x00..0x7F |
+| 2- to 4-byte negative integer | number_integer  | 0xC2..0xF7, followed by 0xC0..0xFF |
+| false                         | `false`         | 0xF8                   |
+| true                          | `true`          | 0xF9                   |
+| null                          | `null`          | 0xFA                   |
+| -1.0                          | number_float    | 0xFB                   |
+| 0.0                           | number_float    | 0xFC                   |
+| 1.0                           | number_float    | 0xFD                   |
+| empty string                  | string          | 0xFF                   |
+
+Non-negative integers are read as number_unsigned, negative integers as number_integer.
+
+!!! info
+
+    Values that do not use the canonical representation, such as integers with a longer encoding than necessary,
+    arrays and objects with up to four elements that are terminated by 0xFE, unsorted object keys, or a 0xFF after a
+    string that would also end without it, are accepted. A second 0xFF is not a terminator but an empty string.
+
+    Strings must be valid UTF-8, and the last string of a message must be terminated by 0xFF.
+
+!!! info
+
+    Any BON8 output created by `to_bon8` can be successfully parsed by `from_bon8`.
+
+??? example
+
+    ```cpp
+    --8<-- "examples/from_bon8.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/from_bon8.output"
+    ```

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

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

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

@@ -174,11 +174,34 @@ The library maps CBOR types to JSON value types as follows:
 
 !!! warning "Object keys"
 
-    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected.
+    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps
+    with keys other than text strings (major type 3) are rejected with a
+    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with `allow_exceptions` set
+    to `false`, a discarded value) naming the type of the key that was found, for instance:
+
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found an unsigned integer; last byte: 0x01
+    ```
+
+    This applies to the [SAX interface](../parsing/sax_interface.md) as well, as the key is read before it is passed
+    on. This is a deliberate restriction of the library's JSON value model, not an oversight: formats built on CBOR
+    maps with integer keys, such as COSE ([RFC 9052](https://www.rfc-editor.org/rfc/rfc9052.html)) or CWT
+    ([RFC 8392](https://www.rfc-editor.org/rfc/rfc8392.html)), cannot be read with this library and need a
+    general-purpose CBOR library instead.
+
+!!! warning "UTF-8 validation of text strings"
+
+    [RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings
+    (major type 3) to be valid UTF-8. This library validates the bytes of every text string (object keys included) at
+    decode time and rejects ill-formed UTF-8 with a
+    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
+    `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is
+    dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold
+    text.
 
 !!! warning "Tagged items"
 
-    Tagged items (0xC0..0xDB) will throw a parse error by default. They can be ignored by passing `cbor_tag_handler_t::ignore` to function `from_cbor`, in which case the tag is skipped and the enclosed data item is parsed on its own. They can be stored by passing `cbor_tag_handler_t::store` to function `from_cbor`. Note that no tag is ever interpreted: for instance, a text string tagged with tag 0 (date/time) stays a string.
+    Tagged items (0xC0..0xDB) will throw a parse error by default. They can be ignored by passing `cbor_tag_handler_t::ignore` to function `from_cbor`, in which case the tag is skipped and the enclosed data item is parsed on its own. Passing `cbor_tag_handler_t::store` to function `from_cbor` stores tagged byte strings (for bytes 0xd8..0xdb) as binary values with the tag as subtype; other tagged values are read as if the tag were ignored. If several tags precede a byte string, only the innermost one is stored. Note that no tag is ever interpreted: for instance, a text string tagged with tag 0 (date/time) stays a string.
 
 ??? example
 

docs/mkdocs/docs/features/binary_formats/index.md

@@ -4,6 +4,7 @@ Though JSON is a ubiquitous data format, it is not a very compact format suitabl
 a network. Hence, the library supports
 
 - [BJData](bjdata.md) (Binary JData),
+- [BON8](bon8.md) (Binary Object Notation 8),
 - [BSON](bson.md) (Binary JSON),
 - [CBOR](cbor.md) (Concise Binary Object Representation),
 - [MessagePack](messagepack.md), and
@@ -18,6 +19,7 @@ to efficiently encode JSON values to byte vectors and to decode such vectors.
 | Format      | Serialization                                 | Deserialization                              |
 |-------------|-----------------------------------------------|----------------------------------------------|
 | BJData      | complete                                      | complete                                     |
+| BON8        | incomplete: no unsigned integers above int64  | complete                                     |
 | BSON        | incomplete: top-level value must be an object | incomplete, but all JSON types are supported |
 | CBOR        | complete                                      | incomplete, but all JSON types are supported |
 | MessagePack | complete                                      | complete                                     |
@@ -28,6 +30,7 @@ to efficiently encode JSON values to byte vectors and to decode such vectors.
 | Format      | Binary values | Binary subtypes |
 |-------------|---------------|-----------------|
 | BJData      | not supported | not supported   |
+| BON8        | not supported | not supported   |
 | BSON        | supported     | supported       |
 | CBOR        | supported     | supported       |
 | MessagePack | supported     | supported       |
@@ -42,6 +45,7 @@ See [binary values](../binary_values.md) for more information.
 | BJData             | 53.2 %      | 91.1 %       | 78.1 %            | 96.6 %        |
 | BJData (size)      | 58.6 %      | 92.1 %       | 86.7 %            | 97.4 %        |
 | BJData (size+type) | 58.6 %      | 92.1 %       | 86.5 %            | 97.4 %        |
+| BON8               | 50.5 %      | 83.8 %       | 63.5 %            | 87.5 %        |
 | BSON               | 85.8 %      | 95.2 %       | 95.8 %            | 106.7 %       |
 | CBOR               | 50.5 %      | 86.3 %       | 68.4 %            | 88.0 %        |
 | MessagePack        | 50.5 %      | 86.0 %       | 68.5 %            | 87.9 %        |

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

@@ -65,6 +65,8 @@ specification:
       - arrays with more than 4294967295 elements
       - objects with more than 4294967295 elements
 
+    Serializing such a value throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412).
+
 !!! info "NaN/infinity handling"
 
     `NaN`, `Infinity`, and `-Infinity` are serialized as a MessagePack float 32 (type 0xCA, 5 bytes total),
@@ -136,6 +138,29 @@ The library maps MessagePack types to JSON value types as follows:
 
     Any MessagePack output created by `to_msgpack` can be successfully parsed by `from_msgpack`.
 
+!!! warning "Object keys"
+
+    MessagePack allows map keys of any type, whereas JSON only allows strings as keys in object values. Like the
+    JSON-compatible [profile](https://github.com/msgpack/msgpack/blob/master/spec.md#profile) sketched in the
+    MessagePack specification, this library restricts map keys to `str` values. Maps with keys of any other type are
+    rejected with a [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
+    `allow_exceptions` set to `false`, a discarded value) naming the type of the key that was found, for instance:
+
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found nil; last byte: 0xC0
+    ```
+
+    This applies to the [SAX interface](../parsing/sax_interface.md) as well, as the key is read before it is passed
+    on. Such input needs a general-purpose MessagePack library instead.
+
+!!! warning "UTF-8 validation of string values"
+
+    The MessagePack specification requires `str` values (`fixstr`, `str 8`, `str 16`, `str 32`) to be valid UTF-8.
+    This library validates the bytes of every such string (object keys included) at decode time and rejects
+    ill-formed UTF-8 with a [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or,
+    with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting
+    value is dumped. `bin`/`ext`/`fixext` values are unaffected and are never validated, since they are not required
+    to hold text.
 
 ??? example
 

docs/mkdocs/docs/features/binary_values.md

@@ -187,6 +187,41 @@ as an array of uint8 values. The library implements this translation.
     }
     ```
 
+### BON8
+
+[BON8](binary_formats/bon8.md) neither supports binary values nor subtypes. The library serializes binary values as an
+array of integers.
+
+??? example
+
+    Code:
+
+    ```cpp
+    // create a binary value of subtype 42 (will be ignored in BON8)
+    json j;
+    j["binary"] = json::binary({0xCA, 0xFE, 0xBA, 0xBE}, 42);
+
+    // convert to BON8
+    auto v = json::to_bon8(j);
+    ```
+
+    `v` is a `std::vector<std::uint8_t>` with the following 16 elements:
+
+    ```c
+    0x87                                     // object with 1 member
+        0x62 0x69 0x6E 0x61 0x72 0x79        // "binary"
+        0x84                                 // array with 4 elements
+            0xC3 0x22 0xC3 0x56 0xC3 0x12 0xC3 0x16  // content (each byte as a 2-byte integer)
+    ```
+
+    Note that the subtype is lost, and deserializing `v` would yield the following value:
+
+    ```json
+    {
+      "binary": [202, 254, 186, 190]
+    }
+    ```
+
 ### BSON
 
 [BSON](binary_formats/bson.md) supports binary values and subtypes. If a subtype is given, it is used and added as an

docs/mkdocs/docs/features/index.md

@@ -35,8 +35,8 @@ C++ types, and finally serialize it again.
 - [Serialization](serialization.md) — turn a value back into JSON text with [`dump`](../api/basic_json/dump.md),
   including pretty-printing and handling of non-ASCII and invalid UTF-8.
 - [Binary formats](binary_formats/index.md) — encode values more compactly as
-  [BJData](binary_formats/bjdata.md), [BSON](binary_formats/bson.md), [CBOR](binary_formats/cbor.md),
+  [BJData](binary_formats/bjdata.md), [BON8](binary_formats/bon8.md), [BSON](binary_formats/bson.md),
-  [MessagePack](binary_formats/messagepack.md), or [UBJSON](binary_formats/ubjson.md).
+  [CBOR](binary_formats/cbor.md), [MessagePack](binary_formats/messagepack.md), or [UBJSON](binary_formats/ubjson.md).
 - [Binary values](binary_values.md) — store and exchange raw byte sequences.
 
 ## How values are stored and configured

docs/mkdocs/docs/features/macros.md

@@ -93,11 +93,21 @@ See [full documentation of `JSON_NO_IO`](../api/macros/json_no_io.md).
 
 ## `JSON_NO_THREAD_LOCAL`
 
-When defined, the library does not use `#!cpp thread_local` storage. Copying a value then always avoids the call stack
+When defined, the library does not use `#!cpp thread_local` storage. Copying a value and comparing two values then
-rather than descending into a bounded number of levels first, which is slower but yields the same values.
+always avoid the call stack rather than descending into a bounded number of levels first, which is slower but yields the
+same values and the same comparisons.
 
 See [full documentation of `JSON_NO_THREAD_LOCAL`](../api/macros/json_no_thread_local.md).
 
+## `JSON_PRECISE_STREAM_POSITION`
+
+When defined to `1`, [`operator>>`](../api/operator_gtgt.md) and non-strict
+[`sax_parse`](../api/basic_json/sax_parse.md) leave an input stream positioned right after the parsed value, instead of
+also consuming the character that terminates a number. The default value is `0`, which preserves the existing behavior;
+this is planned to become the default in version 4.0.0.
+
+See [full documentation of `JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md).
+
 ## `JSON_SKIP_LIBRARY_VERSION_CHECK`
 
 When defined, the library will not create a compiler warning when a different version of the library was already

docs/mkdocs/docs/features/namespace.md

@@ -18,6 +18,8 @@ The complete default namespace name is derived as follows:
     - [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) defined non-zero appends `_dp`.
     - [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) defined non-zero appends
       `_bics`.
+    - [`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`.
 - The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
   underscores. To omit the version component, see [Disabling the version component](#disabling-the-version-component)
   below.

docs/mkdocs/docs/features/parsing/error_recovery.md

@@ -0,0 +1,121 @@
+# Error Recovery
+
+By default, parsing stops at the first error. With the [SAX interface](sax_interface.md), you can instead ask the
+parser to *recover*: to repair the error and continue, so that you get as much as possible out of malformed input, for
+instance a file that was cut off, JSON edited by hand, or the output of a language model.
+
+## Recovering from errors
+
+The SAX parser's [`parse_error`](../../api/json_sax/parse_error.md) function is called for every error. Its return value
+decides what happens next:
+
+- `#!cpp false` stops parsing. This is what the SAX parsers of the library do, so [`parse`](../../api/basic_json/parse.md)
+  and [`accept`](../../api/basic_json/accept.md) never recover.
+- `#!cpp true` repairs the error and continues parsing.
+
+When recovering, the SAX parser still receives well-formed events: every `start_object` or `start_array` is followed by
+the matching `end_object` or `end_array`, and every `key` is followed by exactly one value. A SAX parser that creates a
+JSON value, such as the one in the example below, therefore gets a complete value. Parsing always ends, and
+[`sax_parse`](../../api/basic_json/sax_parse.md) returns `#!cpp false` for input that is not valid JSON, even if every
+error was repaired. Each token is reported at most once, and the SAX parser can stop at any error by returning
+`#!cpp false`.
+
+!!! example
+
+    The example below derives a SAX parser from the library's parser for `json` values (`json_sax_dom_parser`),
+    and recovers from all errors.
+
+    ```cpp
+    --8<-- "examples/sax_parse__error_recovery.cpp"
+    ```
+    
+    Output:
+    
+    ```
+    --8<-- "examples/sax_parse__error_recovery.output"
+    ```
+
+## How errors are repaired
+
+Each error is repaired with the smallest local edit: a missing separator is inserted, a stray token is removed, what can
+be read of a broken string or number is kept, and a value that cannot be read at all becomes `#!json null`.
+
+| Mistake                   | Repair                                                                         | Example                                  | Result                     |
+|---------------------------|--------------------------------------------------------------------------------|------------------------------------------|----------------------------|
+| missing `,` or `:`        | inserted                                                                       | `#!json [1 2]`, `#!json {"a" 1}`         | `[1,2]`, `{"a":1}`         |
+| missing value             | `#!json null` for an object key or between commas in an array                  | `#!json {"a":}`, `#!json [1,,2]`         | `{"a":null}`, `[1,null,2]` |
+| trailing comma            | removed                                                                        | `#!json [1,2,]`                          | `[1,2]`                    |
+| broken string             | invalid escapes and bytes are replaced (see below); a line break ends the string | `#!json ["a\qb"]`                        | `["aqb"]`                  |
+| broken number             | the longest valid beginning is kept                                            | `#!json [1., 2e+]`                       | `[1,2]`                    |
+| unreadable value          | `#!json null`                                                                  | `#!json [1, NaN, tru]`                   | `[1,null,null]`            |
+| number too large          | passed as infinity, together with its text                                     | `#!json [1e999]`                         | infinity (see below)       |
+| stray `:`                 | removed                                                                        | `#!json ["a":1]`                         | `["a",1]`                  |
+| member without a key      | skipped up to the next `,` or `}`                                              | `#!json {1:2, "b":3}`                    | `{"b":3}`                  |
+| wrong closing bracket     | closes the innermost array or object                                           | `#!json {"a":[1,2}, "b":3}`              | `{"a":[1,2],"b":3}`        |
+| input ends too early      | all open arrays and objects are closed                                         | `#!json {"a":[1,2`                       | `{"a":[1,2]}`              |
+| text before the value     | skipped                                                                        | `#!json )]}'{"a":1}`                     | `{"a":1}`                  |
+
+In a string, an unknown escape like `\q` stands for the escaped character (`q`), as in JavaScript. An invalid `\u`
+escape, a lone surrogate, and ill-formed UTF-8 are each replaced by U+FFFD (REPLACEMENT CHARACTER), and control
+characters are kept. A string without its closing quote ends at the next line break or at the end of the input.
+
+The input after the top-level value is not repaired: as without recovery, it is reported as an error, and parsing stops.
+
+## Binary formats
+
+The binary formats ([BJData](../binary_formats/bjdata.md), [BON8](../binary_formats/bon8.md),
+[BSON](../binary_formats/bson.md), [CBOR](../binary_formats/cbor.md), [MessagePack](../binary_formats/messagepack.md),
+and [UBJSON](../binary_formats/ubjson.md)) have no delimiters to find the next value by. So what can be repaired depends
+on whether the end of the item with the error is known, a distinction that
+[RFC 8949, Section 5.3](https://www.rfc-editor.org/rfc/rfc8949.html#section-5.3) makes for CBOR, too.
+
+If the item is complete, but cannot be passed on as it is, it is replaced, and parsing continues after it:
+
+| Mistake                                                             | Formats                                 | Repair                                                                  |
+|---------------------------------------------------------------------|-----------------------------------------|-------------------------------------------------------------------------|
+| tag                                                                 | CBOR                                    | ignored                                                                 |
+| simple value other than `false`, `true`, and `null`, like undefined | CBOR                                    | `#!json null`                                                           |
+| negative integer below the range of `number_integer_t`              | CBOR                                    | the nearest floating-point number                                       |
+| string that is not valid UTF-8                                      | BJData, BSON, CBOR, MessagePack, UBJSON | each ill-formed sequence becomes U+FFFD                                 |
+| character (`C`) that is not ASCII                                   | BJData, UBJSON                          | U+FFFD                                                                  |
+| invalid high-precision number (`H`)                                 | BJData, UBJSON                          | the longest valid beginning is kept, as for JSON text, or `#!json null` |
+| high-precision number too large                                     | BJData, UBJSON                          | passed as infinity, together with its text                              |
+| object key that is not a string                                     | BON8, CBOR, MessagePack                 | the member is skipped                                                   |
+| element of a type the library does not read, like ObjectId or date  | BSON                                    | `#!json null`                                                           |
+| string without its terminator                                       | BSON                                    | kept                                                                    |
+| document whose size does not match its content                      | BSON                                    | kept                                                                    |
+
+CBOR tags and simple values are repaired as [RFC 8949, Section 6.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-6.1)
+suggests for converting CBOR to JSON. Note that [`sax_parse`](../../api/basic_json/sax_parse.md) has no parameter for
+CBOR tags, so every tag is an error there; when recovering, tags are ignored like with
+[`cbor_tag_handler_t::ignore`](../../api/basic_json/cbor_tag_handler_t.md).
+
+After any other error, the end of the item is unknown: the input ended, a byte is not a valid type marker, or a size
+cannot be right. Parsing then stops, and the value read so far is completed: a key that waits for its value gets
+`#!json null`, and all open arrays and objects are closed. This keeps everything before the error of an input that was
+cut off. The exception is BSON, which stores the size of every document: an element whose end is unknown gets
+`#!json null`, the rest of its document is skipped, and parsing continues after the document.
+
+## Limitations
+
+- A repair is a guess. For example, `#!json {"a" "b": 1}` could be meant as `#!json {"a": "b"}` or as
+  `#!json {"a": null, "b": 1}`; it is repaired to the former. Treat recovered values as a best effort, and check the
+  reported errors.
+- A closing bracket always closes the innermost array or object. If a bracket is missing rather than wrong, the
+  repair differs from the intention: `#!json {"a": {"b": [1, 2}, "c": 3}` is repaired to
+  `#!json {"a": {"b": [1, 2], "c": 3}}`, although `#!json {"a": {"b": [1, 2]}, "c": 3}` may have been meant.
+- Keys without quotes, and strings in single quotes, are not supported; such members are skipped.
+- In the binary formats, a member that is skipped because its key is not a string is lost, and so are the elements of a
+  BSON document after one whose end is unknown.
+- A number that is too large for `number_float_t` is passed as positive or negative infinity. The SAX parser's
+  `number_float` also gets the number's text, but a JSON value cannot store it, and
+  [`dump`](../../api/basic_json/dump.md) serializes infinity as `#!json null`.
+- When parsing is not strict (see [`sax_parse`](../../api/basic_json/sax_parse.md)), a repair may read parts of the
+  input after the value, for instance of the next value in a stream of concatenated values.
+
+## See also
+
+- [SAX interface](sax_interface.md) - implement a custom SAX handler
+- [`parse_error`](../../api/json_sax/parse_error.md) - the SAX event for parse errors
+- [`sax_parse`](../../api/basic_json/sax_parse.md) - generate SAX events
+- [parsing and exceptions](parse_exceptions.md) - control error handling

docs/mkdocs/docs/features/parsing/index.md

@@ -41,7 +41,8 @@ document followed by trailing bytes" is accepted rather than rejected. If you ar
 reject any input that is not exactly one JSON document, prefer `parse`.
 
 When using `operator>>` to read several concatenated values this way, a value that is a number must be followed by
-whitespace, because `operator>>` consumes the character that terminates a number — see the
+whitespace, because `operator>>` consumes the character that terminates a number, unless
+[`JSON_PRECISE_STREAM_POSITION`](../../api/macros/json_precise_stream_position.md) is defined to `1` — see the
 [`operator>>` notes](../../api/operator_gtgt.md#notes) for details and examples.
 
 ## SAX vs. DOM parsing
@@ -64,7 +65,7 @@ You can influence a DOM parse without switching to the SAX interface by passing
 When the input is not valid JSON, the `parse` function throws an exception by default. If exceptions are undesired or
 unavailable, the parser can instead return a discarded value, or [`accept`](../../api/basic_json/accept.md) can be used
 to only check whether an input is valid JSON. See [parsing and exceptions](parse_exceptions.md) for the available
-options.
+options. To get as much as possible out of malformed input, a SAX parser can [recover from errors](error_recovery.md).
 
 ## See also
 
@@ -75,3 +76,4 @@ options.
 - [parser callbacks](parser_callbacks.md) - influence the parsing by a callback function
 - [SAX interface](sax_interface.md) - implement a custom SAX handler
 - [parsing and exceptions](parse_exceptions.md) - control error handling
+- [error recovery](error_recovery.md) - get as much as possible out of malformed input

docs/mkdocs/docs/features/parsing/parse_exceptions.md

@@ -64,7 +64,8 @@ bool parse_error(std::size_t position,
                  const json::exception& ex);
 ```
 
-The return value indicates whether the parsing should continue, so the function should usually return `#!cpp false`.
+The return value decides whether to stop parsing (`#!cpp false`) or to repair the error and continue
+(`#!cpp true`); see [error recovery](error_recovery.md) for the latter.
 
 ??? example
 

docs/mkdocs/docs/features/parsing/sax_interface.md

@@ -60,7 +60,8 @@ bool key(string_t& val);
 bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex);
 ```
 
-The return value of each function determines whether parsing should proceed.
+The return value of each function determines whether parsing should proceed. For `parse_error`, returning
+`#!cpp true` [recovers from the error](error_recovery.md).
 
 To implement your own SAX handler, proceed as follows:
 
@@ -68,7 +69,7 @@ To implement your own SAX handler, proceed as follows:
 2. Create an object of your SAX interface class, e.g. `my_sax`.
 3. Call `#!cpp bool json::sax_parse(input, &my_sax);` where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.
 
-Note the `sax_parse` function only returns a `#!cpp bool` indicating the result of the last executed SAX event. It does not return `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file `json_sax.hpp`.
+Note the `sax_parse` function only returns a `#!cpp bool` indicating whether the input was parsed without errors and no SAX event returned `#!cpp false`. It does not return `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file `json_sax.hpp`.
 
 ## See also
 

docs/mkdocs/docs/features/serialization.md

@@ -117,7 +117,7 @@ For the [{fmt}](https://github.com/fmtlib/fmt) library, the library ships a
 ## Serializing to other formats
 
 Besides JSON text, a value can also be serialized to the more compact [binary formats](binary_formats/index.md)
-(BJData, BSON, CBOR, MessagePack, UBJSON).
+(BJData, BON8, BSON, CBOR, MessagePack, UBJSON).
 
 ## See also
 

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

@@ -547,7 +547,7 @@ Grisu2 algorithm, which produces the shortest representation that round-trips. O
 ### Required for the binary formats
 
 `NumberFloatType` must be `#!cpp float` or `#!cpp double`. The writers for
-[CBOR, MessagePack, UBJSON, BJData, and BSON](../binary_formats/index.md) map a floating-point value onto an IEEE 754
+[CBOR, MessagePack, UBJSON, BJData, BON8, and BSON](../binary_formats/index.md) map a floating-point value onto an IEEE 754
 binary32 or binary64 field and have no encoding for `#!cpp long double`.
 
 ### Compatible types
@@ -562,7 +562,11 @@ binary32 or binary64 field and have no encoding for `#!cpp long double`.
 ## `AllocatorType`
 
 `AllocatorType` is instantiated with **one** argument, for each of `object_t`, `array_t`, `string_t`, `binary_t`,
-`basic_json`, and `#!cpp std::pair<const StringType, basic_json>`.
+`basic_json`, `#!cpp std::pair<const StringType, basic_json>`, and `#!cpp std::pair<StringType, basic_json>`.
+
+`AllocatorType` is not the only allocator a `basic_json` uses. It allocates the JSON values themselves, but most
+temporary storage is allocated with `#!cpp std::allocator`. This includes the parser's stacks and the stacks that
+process deeply nested values without recursion.
 
 ### Always required
 

docs/mkdocs/docs/home/architecture.md

@@ -1,34 +1,125 @@
 # Architecture
 
-!!! info
+This page gives a high-level overview of the library's architecture. It should help new contributors to get an idea of
-
+the used concepts and where to make changes.
-    This page is still under construction. Its goal is to provide a high-level overview of the library's architecture.
-    This should help new contributors to get an idea of the used concepts and where to make changes.
 
 ## Overview
 
-The main structure is class [nlohmann::basic_json](../api/basic_json/index.md).
+The library is built around a single class template, [`nlohmann::basic_json`](../api/basic_json/index.md). A
+`basic_json` value is a node in a tree of JSON values. All other components either create such a tree from an input
+(parsing), write a tree to an output (serialization), or give access to it (iterators, JSON Pointer, conversions).
 
-- public API
+```mermaid
-- container interface
+flowchart LR
-- iterators
+    input[/"input<br>(string, stream,<br>iterator range, file)"/]
+    ia["input adapter"]
+    lexer["lexer"]
+    parser["parser"]
+    breader["binary_reader"]
+    sax["SAX interface"]
+    value[("basic_json<br>value tree")]
+    serializer["serializer"]
+    bwriter["binary_writer"]
+    oa["output adapter"]
+    output[/"output<br>(string, stream,<br>vector)"/]
 
-## Template specializations
+    input --> ia
+    ia --> lexer --> parser --> sax
+    ia --> breader --> sax
+    sax --> value
+    value --> serializer --> oa
+    value --> bwriter --> oa
+    oa --> output
+```
 
-- describe template parameters of `basic_json`
+- **JSON text** is read by an [input adapter](#input-adapters), tokenized by the lexer, and turned into SAX events by
-- [`json`](../api/json.md)
+  the parser.
-- [`ordered_json`](../api/ordered_json.md) via [`ordered_map`](../api/ordered_map.md)
+- **Binary formats** (BJData, BSON, CBOR, MessagePack, UBJSON) are read by an input adapter and turned into the same SAX
+  events by the `binary_reader`.
+- A [SAX consumer](#sax-interface) receives the events. The one used by [`parse`](../api/basic_json/parse.md) builds a
+  `basic_json` value tree.
+- The `serializer` (JSON text) or the `binary_writer` (binary formats) writes a value tree to an
+  [output adapter](#output-adapters).
+
+## Source layout
+
+The public headers are in [`include/nlohmann`](https://github.com/nlohmann/json/tree/develop/include/nlohmann):
+
+- [`json.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json.hpp) defines class [`basic_json`](../api/basic_json/index.md).
+- [`json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json_fwd.hpp) contains forward declarations.
+- [`adl_serializer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/adl_serializer.hpp), [`byte_container_with_subtype.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/byte_container_with_subtype.hpp), and [`ordered_map.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/ordered_map.hpp) define
+  [`adl_serializer`](../api/adl_serializer/index.md),
+  [`byte_container_with_subtype`](../api/byte_container_with_subtype/index.md), and
+  [`ordered_map`](../api/ordered_map.md).
+
+Everything else lives in [`detail/`](https://github.com/nlohmann/json/tree/develop/include/nlohmann/detail) and namespace `nlohmann::detail`, which is not part of the public API. Paths
+below are relative to `include/nlohmann`.
+
+| Component | Location |
+|-----------|----------|
+| Value type enumeration | [`detail/value_t.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/value_t.hpp) |
+| Input adapters | [`detail/input/input_adapters.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/input_adapters.hpp) |
+| Lexer | [`detail/input/lexer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/lexer.hpp), [`detail/input/number_parse.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/number_parse.hpp), [`detail/input/string_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/string_scan.hpp) |
+| Parser | [`detail/input/parser.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/parser.hpp) |
+| SAX interface and DOM builders | [`detail/input/json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp) |
+| Binary format readers | [`detail/input/binary_reader.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/binary_reader.hpp) |
+| JSON serializer | [`detail/output/serializer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/output/serializer.hpp), [`detail/conversions/to_chars.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/conversions/to_chars.hpp) |
+| Binary format writers | [`detail/output/binary_writer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/output/binary_writer.hpp) |
+| Output adapters | [`detail/output/output_adapters.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/output/output_adapters.hpp) |
+| Iterators | [`detail/iterators/`](https://github.com/nlohmann/json/tree/develop/include/nlohmann/detail/iterators) |
+| Conversions from/to arbitrary types | [`detail/conversions/from_json.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/conversions/from_json.hpp), [`detail/conversions/to_json.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/conversions/to_json.hpp) |
+| JSON Pointer | [`detail/json_pointer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/json_pointer.hpp) |
+| Exceptions | [`detail/exceptions.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/exceptions.hpp) |
+| Type traits and C++ feature backports | [`detail/meta/`](https://github.com/nlohmann/json/tree/develop/include/nlohmann/detail/meta) |
+| Macros | [`detail/macro_scope.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/macro_scope.hpp), [`detail/macro_unscope.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/macro_unscope.hpp), [`detail/abi_macros.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/abi_macros.hpp) |
+
+The single-header version [`single_include/nlohmann/json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp)
+is generated from these files with `make amalgamate` and must not be edited by hand.
+
+## Template parameters
+
+[`basic_json`](../api/basic_json/index.md) is parameterized by the types it uses to store values and to convert from and to other types:
+
+| Template parameter   | Default                     | Used for                                                          |
+|----------------------|-----------------------------|-------------------------------------------------------------------|
+| `ObjectType`         | `std::map`                  | objects, see [`object_t`](../api/basic_json/object_t.md)          |
+| `ArrayType`          | `std::vector`               | arrays, see [`array_t`](../api/basic_json/array_t.md)             |
+| `StringType`         | `std::string`               | strings and object keys, see [`string_t`](../api/basic_json/string_t.md) |
+| `BooleanType`        | `bool`                      | Booleans, see [`boolean_t`](../api/basic_json/boolean_t.md)       |
+| `NumberIntegerType`  | `std::int64_t`              | signed integers, see [`number_integer_t`](../api/basic_json/number_integer_t.md) |
+| `NumberUnsignedType` | `std::uint64_t`             | unsigned integers, see [`number_unsigned_t`](../api/basic_json/number_unsigned_t.md) |
+| `NumberFloatType`    | `double`                    | floating-point numbers, see [`number_float_t`](../api/basic_json/number_float_t.md) |
+| `AllocatorType`      | `std::allocator`            | allocating objects, arrays, strings, and binary values            |
+| `JSONSerializer`     | `adl_serializer`            | conversions from/to other types, see [`adl_serializer`](../api/adl_serializer/index.md) |
+| `BinaryType`         | `std::vector<std::uint8_t>` | binary values, see [`binary_t`](../api/basic_json/binary_t.md)  |
+| `CustomBaseClass`    | `void`                      | an optional base class, see [`json_base_class_t`](../api/basic_json/json_base_class_t.md) |
+
+The library provides two specializations:
+
+- [`json`](../api/json.md) uses all default template arguments.
+- [`ordered_json`](../api/ordered_json.md) uses [`ordered_map`](../api/ordered_map.md) as `ObjectType` to keep the
+  insertion order of object keys.
+
+The requirements on the template arguments are listed in
+[Template Parameter Requirements](../features/types/template_parameters.md).
 
 ## Value storage
 
-Values are stored as a tagged union of [value_t](../api/basic_json/value_t.md) and json_value.
+Each [`basic_json`](../api/basic_json/index.md) value stores its content as a tagged union: an enumeration [`value_t`](../api/basic_json/value_t.md)
+names the type of the value, and a union `json_value` holds the value itself. Both are members of the nested struct
+`data`, which is the only data member `m_data` of `basic_json`:
 
 ```cpp
-/// the type of the current element
+struct data
-value_t m_type = value_t::null;
+{
+    /// the type of the current element
+    value_t m_type = value_t::null;
 
-/// the value of the current element
+    /// the value of the current element
-json_value m_value = {};
+    json_value m_value = {};
+};
+
+data m_data = {};
 ```
 
 with
@@ -68,42 +159,83 @@ union json_value {
 };
 ```
 
-## Parsing inputs (deserialization)
+Objects, arrays, strings, and binary values are allocated on the heap with `AllocatorType`, and the union only stores a
+pointer to them. This keeps a `basic_json` value small: one pointer-sized union and one byte for the type. The class
+maintains the invariant that the pointer matching `m_type` is never null; `assert_invariant()` checks it with
+[runtime assertions](../features/assertions.md).
 
-Input is read via **input adapters** that abstract a source with a common interface:
+## Input adapters
+
+Input is read via **input adapters** that abstract a source. Every input adapter provides this interface:
 
 ```cpp
-/// read a single character
+/// the type of the characters in the input
-std::char_traits<char>::int_type get_character() noexcept;
+using char_type = ...;
 
-/// read multiple characters to a destination buffer and
+/// read a single character; returns std::char_traits<char_type>::eof() at the end of the input
-/// returns the number of characters successfully read
+typename std::char_traits<char_type>::int_type get_character();
+
+/// read up to count * sizeof(T) bytes into dest and return the number of bytes read
+/// (used by the binary readers)
 template<class T>
 std::size_t get_elements(T* dest, std::size_t count = 1);
 ```
 
-List examples of input adapters.
+The lexer detects two optional extensions at compile time. Only `iterator_input_adapter` provides them, and only for
+random-access input of single-byte characters:
 
-## SAX Interface
+- `supports_seek`, `get_consumed_count()`, and `copy_consumed_range()` let the lexer reconstruct already consumed input
+  for error messages instead of copying every character it reads.
+- `supports_bulk_scan`, `bulk_data()`, `bulk_remaining()`, and `bulk_skip()` let the lexer scan strings directly in
+  contiguous memory, several bytes at a time.
 
-TODO
+The function `input_adapter` picks the right adapter for the argument passed to `parse`, `accept`, `sax_parse`, or the
+`from_*` functions:
 
-## Writing outputs (serialization)
+- `iterator_input_adapter` reads from an iterator range, which also covers strings, containers, and pointers.
+- `wide_string_input_adapter` reads from ranges of `wchar_t`, `char16_t`, or `char32_t` and converts them to UTF-8.
+  It cannot be used for binary formats; its `get_elements()` throws.
+- `input_stream_adapter` reads from a `std::istream`.
+- `file_input_adapter` reads from a `std::FILE*`.
+
+## SAX interface
+
+The parser does not build values itself. It reports what it reads as events to a [SAX](../features/parsing/sax_interface.md)
+consumer, which implements the interface [`json_sax`](../api/json_sax/index.md): `null`, `boolean`, `number_integer`,
+`number_unsigned`, `number_float`, `string`, `binary`, `start_object`, `key`, `end_object`, `start_array`, `end_array`,
+and `parse_error`.
+
+The library comes with two consumers in `detail/input/json_sax.hpp`:
+
+- `json_sax_dom_parser` builds a [`basic_json`](../api/basic_json/index.md) value tree. [`parse`](../api/basic_json/parse.md) uses it.
+- `json_sax_dom_callback_parser` does the same, but calls a [parser callback](../features/parsing/parser_callbacks.md)
+  for each event, which can skip values. `parse` uses it when a callback is given.
+
+The `binary_reader` emits the same events for binary formats, so [`sax_parse`](../api/basic_json/sax_parse.md) works
+with a user-defined consumer for JSON and for all binary formats alike.
+
+## Output adapters
 
 Output is written via **output adapters**:
 
 ```cpp
-template<typename T>
 void write_character(CharType c);
 
-template<typename CharType>
 void write_characters(const CharType* s, std::size_t length);
 ```
 
-List examples of output adapters.
+The `serializer` (used by [`dump`](../api/basic_json/dump.md) and [`operator<<`](../api/operator_ltlt.md)) and the
+`binary_writer` (used by the `to_*` functions) write to one of these adapters:
+
+- `output_vector_adapter` appends to a `std::vector`.
+- `output_stream_adapter` writes to a `std::ostream`.
+- `output_string_adapter` appends to a string.
 
 ## Value conversion
 
+Values are converted from and to other types with the `JSONSerializer` template parameter. The default,
+[`adl_serializer`](../api/adl_serializer/index.md), calls the free functions
+
 ```cpp
 template<class T>
 void to_json(basic_json& j, const T& t);
@@ -112,13 +244,23 @@ template<class T>
 void from_json(const basic_json& j, T& t);
 ```
 
+found by argument-dependent lookup. The library defines them for standard types in `detail/conversions`; users add them
+for their own types, see [Arbitrary Type Conversions](../features/arbitrary_types.md). The
+[serialization macros](../features/macros.md) generate these functions.
+
 ## Additional features
 
-- JSON Pointers
+- [JSON Pointer](../features/json_pointer.md) (class `json_pointer`) addresses values inside a tree. It is also the
-- Binary formats
+  basis of [JSON Patch](../features/json_patch.md).
-- Custom base class
+- [Binary formats](../features/binary_formats/index.md) are read by `binary_reader` and written by `binary_writer`.
-- Conversion macros
+- A [custom base class](../api/basic_json/json_base_class_t.md) can add members to every [`basic_json`](../api/basic_json/index.md) value.
+- [Serialization macros](../features/macros.md) generate `to_json` and `from_json` functions for user-defined types.
 
 ## Details namespace
 
-- C++ feature backports
+Namespace `nlohmann::detail` contains all implementation details. It is not part of the public API and may change in any
+release. Besides the components above, it contains:
+
+- type traits to detect the capabilities of user-defined types (`detail/meta/type_traits.hpp`),
+- backports of C++14/17 features to C++11 (`detail/meta/cpp_future.hpp`), and
+- helpers such as `string_concat` and `string_escape`.

docs/mkdocs/docs/home/design_goals.md

@@ -6,7 +6,7 @@ There are myriads of [JSON](https://json.org) libraries out there, and each may
 
 - **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.
 
-- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).
+- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [OpenSSF Best Practices](https://www.bestpractices.dev/projects/289).
 
 Other aspects were not so important to us:
 

docs/mkdocs/docs/home/exceptions.md

@@ -340,15 +340,23 @@ An unexpected byte was read in a [binary format](../features/binary_formats/inde
 ### json.exception.parse_error.113
 
 A string could not be read from a [binary format](../features/binary_formats/index.md): either a value that is not a
-string was read where one was required (for instance as a map key), or the string's length specification is invalid.
+string was read where one was required (for instance as a map key), the string's length specification is invalid, or
+the string's bytes are not valid UTF-8.
+
+CBOR and MessagePack allow map keys of any type, but JSON object keys are always strings. Maps with keys of any other
+type (for instance integers or `null`) are therefore not supported; see the notes on
+[CBOR](../features/binary_formats/cbor.md) and [MessagePack](../features/binary_formats/messagepack.md).
 
 !!! failure "Example messages"
 
     ```
-    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found an unsigned integer; last byte: 0x01
     ```
     ```
-    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack string: expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0xFF
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack object key: only string keys are supported, but found nil; last byte: 0xC0
+    ```
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x7C
     ```
     ```
     [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing UBJSON char: byte after 'C' must be in range 0x00..0x7F; last byte: 0x82
@@ -356,6 +364,9 @@ string was read where one was required (for instance as a map key), or the strin
     ```
     [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing BJData string: string length must not be negative
     ```
+    ```
+    [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR string: invalid string: ill-formed UTF-8 byte
+    ```
 
 ### json.exception.parse_error.114
 
@@ -928,19 +939,25 @@ A JSON Patch `add` operation cannot be applied because the target location's par
 
 ### json.exception.out_of_range.412
 
-BSON stores the length of documents, arrays, strings, and binary values in a signed 32-bit integer. This exception is thrown when a value is too large to be described by such a length field.
+BSON stores the length of documents, arrays, strings, and binary values in a signed 32-bit integer, and MessagePack
+stores the length of strings, binary values, arrays, and objects in at most an unsigned 32-bit integer. This exception
+is thrown when a value is too large to be described by such a length field.
 
-!!! failure "Example message"
+!!! failure "Example messages"
 
     ```
     BSON length 2147483661 exceeds maximum of 2147483647
     ```
+    ```
+    MessagePack length 4294967296 exceeds maximum of 4294967295
+    ```
 
 !!! note
 
-    This exception was added in version 3.13.0. Before that, the length was silently truncated, and
+    This exception was added in version 3.13.0. Before that, the BSON length was silently truncated, and
     [`to_bson`](../api/basic_json/to_bson.md) produced documents with negative length prefixes that
-    [`from_bson`](../api/basic_json/from_bson.md) rejected.
+    [`from_bson`](../api/basic_json/from_bson.md) rejected; [`to_msgpack`](../api/basic_json/to_msgpack.md) wrote such
+    a value without any length, producing output that could not be read back.
 
 ### json.exception.out_of_range.413
 

docs/mkdocs/includes/glossary.md

@@ -5,6 +5,7 @@
 *[ASCII]: American Standard Code for Information Interchange
 *[BDFL]: Benevolent Dictator for Life
 *[BJData]: Binary JData
+*[BON8]: Binary Object Notation 8
 *[BSON]: Binary JSON
 *[CBOR]: Concise Binary Object Representation
 *[CC0]: Creative Commons Zero

docs/mkdocs/mkdocs.yml

@@ -63,6 +63,7 @@ nav:
       - Binary Formats:
           - features/binary_formats/index.md
           - features/binary_formats/bjdata.md
+          - features/binary_formats/bon8.md
           - features/binary_formats/bson.md
           - features/binary_formats/cbor.md
           - features/binary_formats/messagepack.md
@@ -86,6 +87,7 @@ nav:
       - features/object_order.md
       - Parsing:
           - features/parsing/index.md
+          - features/parsing/error_recovery.md
           - features/parsing/json_lines.md
           - features/parsing/parse_exceptions.md
           - features/parsing/parser_callbacks.md
@@ -142,6 +144,7 @@ nav:
           - 'flatten': api/basic_json/flatten.md
           - 'format_as': api/basic_json/format_as.md
           - 'from_bjdata': api/basic_json/from_bjdata.md
+          - 'from_bon8': api/basic_json/from_bon8.md
           - 'from_bson': api/basic_json/from_bson.md
           - 'from_cbor': api/basic_json/from_cbor.md
           - 'from_msgpack': api/basic_json/from_msgpack.md
@@ -213,6 +216,7 @@ nav:
           - 'swap': api/basic_json/swap.md
           - 'std::swap<basic_json>': api/basic_json/std_swap.md
           - 'to_bjdata': api/basic_json/to_bjdata.md
+          - 'to_bon8': api/basic_json/to_bon8.md
           - 'to_bson': api/basic_json/to_bson.md
           - 'to_cbor': api/basic_json/to_cbor.md
           - 'to_msgpack': api/basic_json/to_msgpack.md
@@ -293,6 +297,7 @@ nav:
           - 'JSON_NOEXCEPTION': api/macros/json_noexception.md
           - 'JSON_NO_IO': api/macros/json_no_io.md
           - 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md
+          - 'JSON_PRECISE_STREAM_POSITION': api/macros/json_precise_stream_position.md
           - 'JSON_SKIP_LIBRARY_VERSION_CHECK': api/macros/json_skip_library_version_check.md
           - 'JSON_SKIP_UNSUPPORTED_COMPILER_CHECK': api/macros/json_skip_unsupported_compiler_check.md
           - 'JSON_STRICT_NUL_HANDLING': api/macros/json_strict_nul_handling.md
@@ -317,7 +322,9 @@ nav:
       - community/contribution_guidelines.md
       - community/quality_assurance.md
       - community/governance.md
+      - community/roadmap.md
       - community/security_policy.md
+      - community/assurance_case.md
 
 # Extras
 extra:
@@ -409,7 +416,7 @@ plugins:
       markdown_description: >
         JSON for Modern C++ is a C++11 header-only library implementing a JSON
         value type with an STL-like API, JSON Pointer/Patch, CBOR/MessagePack/
-        BSON/UBJSON/BJData binary format support, and a SAX-style parser interface.
+        BSON/UBJSON/BJData/BON8 binary format support, and a SAX-style parser interface.
       sections:
         Home:
           - index.md

include/nlohmann/detail/abi_macros.hpp

@@ -38,6 +38,14 @@
     #define JSON_BRACE_INIT_COPY_SEMANTICS 0
 #endif
 
+#ifndef JSON_PRECISE_STREAM_POSITION
+    #define JSON_PRECISE_STREAM_POSITION 0
+#endif
+
+#ifndef JSON_STRICT_NUL_HANDLING
+    #define JSON_STRICT_NUL_HANDLING 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -62,21 +70,35 @@
     #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
 #endif
 
+#if JSON_PRECISE_STREAM_POSITION
+    #define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION _psp
+#else
+    #define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION
+#endif
+
+#if JSON_STRICT_NUL_HANDLING
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING _snul
+#else
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING
+#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) json_abi ## a ## b ## c ## d
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f) json_abi ## a ## b ## c ## d ## e ## f
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
-            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
+            NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION,           \
+            NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

include/nlohmann/detail/input/input_adapters.hpp

@@ -34,7 +34,7 @@ namespace detail
 {
 
 /// the supported input formats
-enum class input_format_t { json, cbor, msgpack, ubjson, bson, bjdata };
+enum class input_format_t { json, cbor, msgpack, ubjson, bson, bjdata, bon8 };
 
 ////////////////////
 // input adapters //
@@ -101,6 +101,11 @@ class input_stream_adapter
         // maintain ifstream flags, except eof
         if (is != nullptr)
         {
+#if JSON_PRECISE_STREAM_POSITION
+            // consume the character last returned by get_character() unless it
+            // was given back with release_lookahead()
+            commit_lookahead();
+#endif
             is->clear(is->rdstate() & std::ios::eofbit);
         }
     }
@@ -114,6 +119,58 @@ class input_stream_adapter
     input_stream_adapter& operator=(input_stream_adapter&) = delete;
     input_stream_adapter& operator=(input_stream_adapter&&) = delete;
 
+#if JSON_PRECISE_STREAM_POSITION
+    input_stream_adapter(input_stream_adapter&& rhs) noexcept
+        : is(rhs.is), sb(rhs.sb), lookahead(rhs.lookahead)
+    {
+        rhs.is = nullptr;
+        rhs.sb = nullptr;
+        rhs.lookahead = false;
+    }
+
+    // Whether the character last returned by get_character() can be given back
+    // to the input with release_lookahead().
+    static constexpr bool supports_lookahead = true;
+
+    // std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
+    // ensure that std::char_traits<char>::eof() and the character 0xFF do not
+    // end up as the same value, e.g., 0xFFFFFFFF.
+    //
+    // The character is peeked rather than consumed: it is only stepped over
+    // once the next character is requested, or when the adapter is destroyed.
+    // Until then, release_lookahead() can leave it in the input.
+    std::char_traits<char>::int_type get_character()
+    {
+        if (lookahead)
+        {
+            // step over the character returned by the previous call
+            sb->sbumpc();
+        }
+
+        auto res = sb->sgetc();
+        // set eof manually, as we don't use the istream interface.
+        if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
+        {
+            // there is nothing to step over next time
+            lookahead = false;
+            is->clear(is->rdstate() | std::ios::eofbit);
+        }
+        else
+        {
+            lookahead = true;
+        }
+        return res;
+    }
+
+    // Leave the character last returned by get_character() in the input, so
+    // that the next read from the stream - by this adapter or by the caller
+    // once parsing is done - sees it again. Unlike putting a consumed
+    // character back, this cannot fail.
+    void release_lookahead() noexcept
+    {
+        lookahead = false;
+    }
+#else
     input_stream_adapter(input_stream_adapter&& rhs) noexcept
         : is(rhs.is), sb(rhs.sb)
     {
@@ -124,6 +181,9 @@ class input_stream_adapter
     // std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
     // ensure that std::char_traits<char>::eof() and the character 0xFF do not
     // end up as the same value, e.g., 0xFFFFFFFF.
+    //
+    // The character is consumed, so the character that terminates a number
+    // stays consumed after parsing; see JSON_PRECISE_STREAM_POSITION.
     std::char_traits<char>::int_type get_character()
     {
         auto res = sb->sbumpc();
@@ -134,10 +194,14 @@ class input_stream_adapter
         }
         return res;
     }
+#endif
 
     template<class T>
     std::size_t get_elements(T* dest, std::size_t count = 1)
     {
+#if JSON_PRECISE_STREAM_POSITION
+        commit_lookahead();
+#endif
         auto res = static_cast<std::size_t>(sb->sgetn(reinterpret_cast<char*>(dest), static_cast<std::streamsize>(count * sizeof(T))));
         if (JSON_HEDLEY_UNLIKELY(res < count * sizeof(T)))
         {
@@ -147,9 +211,27 @@ class input_stream_adapter
     }
 
   private:
+#if JSON_PRECISE_STREAM_POSITION
+    // Step over the character last returned by get_character(). The character
+    // has already been peeked successfully, so for every streambuf with a get
+    // area this is a pointer increment that cannot fail.
+    void commit_lookahead()
+    {
+        if (lookahead)
+        {
+            lookahead = false;
+            sb->sbumpc();
+        }
+    }
+#endif
+
     /// the associated input stream
     std::istream* is = nullptr;
     std::streambuf* sb = nullptr;
+#if JSON_PRECISE_STREAM_POSITION
+    /// whether get_character() peeked a character that is not consumed yet
+    bool lookahead = false;
+#endif
 };
 #endif  // JSON_NO_IO
 

include/nlohmann/detail/input/json_sax.hpp

@@ -131,7 +131,9 @@ struct json_sax
     @param[in] position    the position in the input where the error occurs
     @param[in] last_token  the last read token
     @param[in] ex          an exception object describing the error
-    @return whether parsing should proceed (must return false)
+    @return whether to recover from the error: false stops parsing; true
+            repairs the error and continues, or, if that is not possible,
+            stops after completing the value read so far
     */
     virtual bool parse_error(std::size_t position,
                              const std::string& last_token,
@@ -186,9 +188,12 @@ a pointer to the respective array or object for each recursion depth.
 After successful parsing, the value that is passed by reference to the
 constructor contains the parsed value.
 
-@tparam BasicJsonType  the JSON type
+@tparam BasicJsonType     the JSON type
+@tparam InputAdapterType  the input adapter of the lexer that can be passed to
+                          the constructor to record diagnostic positions; it
+                          does not matter if no lexer is passed
 */
-template<typename BasicJsonType, typename InputAdapterType>
+template<typename BasicJsonType, typename InputAdapterType = string_input_adapter_type>
 class json_sax_dom_parser
 {
   public:
@@ -505,7 +510,7 @@ class json_sax_dom_parser
     lexer_t* m_lexer_ref = nullptr;
 };
 
-template<typename BasicJsonType, typename InputAdapterType>
+template<typename BasicJsonType, typename InputAdapterType = string_input_adapter_type>
 class json_sax_dom_callback_parser
 {
   public:

include/nlohmann/detail/input/lexer.hpp

@@ -11,6 +11,7 @@
 #include <array> // array
 #include <clocale> // localeconv
 #include <cstddef> // size_t
+#include <cstdint> // uint8_t
 #include <cstdio> // snprintf
 #include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
 #include <initializer_list> // initializer_list
@@ -127,6 +128,25 @@ constexpr bool input_adapter_supports_seek(std::false_type /*detected*/)
     return false;
 }
 
+// Detect whether an input adapter reads with one character of lookahead that
+// can be left in the input (see input_stream_adapter::supports_lookahead,
+// which is only defined with JSON_PRECISE_STREAM_POSITION), detected like
+// supports_seek above.
+template<typename InputAdapterType>
+using detect_supports_lookahead = decltype(InputAdapterType::supports_lookahead);
+
+template<typename InputAdapterType>
+constexpr bool input_adapter_supports_lookahead(std::true_type /*detected*/)
+{
+    return InputAdapterType::supports_lookahead;
+}
+
+template<typename InputAdapterType>
+constexpr bool input_adapter_supports_lookahead(std::false_type /*detected*/)
+{
+    return false;
+}
+
 // Detect whether an input adapter exposes a contiguous byte block that the
 // lexer can scan directly (see iterator_input_adapter::supports_bulk_scan).
 // Adapters without the flag - file, stream, wide-string, user-defined - fall
@@ -167,6 +187,12 @@ class lexer : public lexer_base<BasicJsonType>
     static constexpr bool lazy_token_string =
         input_adapter_supports_seek<InputAdapterType>(is_detected<detect_supports_seek, InputAdapterType> {});
 
+    /// whether a simulated unget can be passed on to the input adapter, which
+    /// then leaves the character in the input; see
+    /// input_adapter_supports_lookahead
+    static constexpr bool can_release_lookahead =
+        input_adapter_supports_lookahead<InputAdapterType>(is_detected<detect_supports_lookahead, InputAdapterType> {});
+
     /// whether string scanning may bulk-consume runs of ordinary characters
     /// directly from a contiguous input buffer (SWAR fast path). This requires
     /// the token to be reconstructible lazily (lazy_token_string), so bypassing
@@ -428,8 +454,16 @@ class lexer : public lexer_base<BasicJsonType>
                             if (0xD800 <= codepoint1 && codepoint1 <= 0xDBFF)
                             {
                                 // expect next \uxxxx entry
-                                if (JSON_HEDLEY_LIKELY(get() == '\\' && get() == 'u'))
+                                if (JSON_HEDLEY_LIKELY(get() == '\\'))
                                 {
+                                    if (JSON_HEDLEY_UNLIKELY(get() != 'u'))
+                                    {
+                                        // current is the character escaped by the backslash
+                                        error_message = "invalid string: surrogate U+D800..U+DBFF must be followed by U+DC00..U+DFFF";
+                                        string_error_resume = resume_kind::escaped_character;
+                                        return token_type::parse_error;
+                                    }
+
                                     const int codepoint2 = get_codepoint();
 
                                     if (JSON_HEDLEY_UNLIKELY(codepoint2 == -1))
@@ -454,7 +488,11 @@ class lexer : public lexer_base<BasicJsonType>
                                     }
                                     else
                                     {
+                                        // the second escape was read completely and is a
+                                        // code point of its own
                                         error_message = "invalid string: surrogate U+D800..U+DBFF must be followed by U+DC00..U+DFFF";
+                                        string_error_resume = resume_kind::after_escape;
+                                        string_error_codepoint = codepoint2;
                                         return token_type::parse_error;
                                     }
                                 }
@@ -468,7 +506,9 @@ class lexer : public lexer_base<BasicJsonType>
                             {
                                 if (JSON_HEDLEY_UNLIKELY(0xDC00 <= codepoint1 && codepoint1 <= 0xDFFF))
                                 {
+                                    // the escape was read completely
                                     error_message = "invalid string: surrogate U+DC00..U+DFFF must follow U+D800..U+DBFF";
+                                    string_error_resume = resume_kind::after_escape;
                                     return token_type::parse_error;
                                 }
                             }
@@ -1898,6 +1938,21 @@ scan_number_done:
         uncapture_char(std::integral_constant<bool, lazy_token_string> {});
     }
 
+    /// adapter without lookahead: nothing to do (see release_lookahead)
+    void release_lookahead_impl(std::false_type /*can_release*/) const noexcept {}
+
+    /// adapter with lookahead: leave the character in the input instead
+    void release_lookahead_impl(std::true_type /*can_release*/)
+    {
+        if (next_unget)
+        {
+            // the character is read from the input again rather than replayed
+            // from current, so the adapter must not step over it
+            next_unget = false;
+            ia.release_lookahead();
+        }
+    }
+
     /// seekable adapter: nothing was captured, so nothing to undo
     void uncapture_char(std::true_type /*lazy*/) const noexcept {}
 
@@ -1961,6 +2016,31 @@ scan_number_done:
         return position;
     }
 
+    /*!
+    @brief pass a pending simulated unget on to the input
+
+    unget() only rewinds the lexer's own bookkeeping, so the character that
+    terminated the last token (e.g. the character after a number) would still
+    be stepped over when the input adapter is done. Callers that hand the
+    input back to the user afterwards - operator>> and non-strict sax_parse -
+    call this once when scanning is done, so that the input is positioned
+    right after the value.
+
+    Adapters without lookahead (see input_adapter_supports_lookahead) are not
+    handed back to the user, so this is a no-op for them. Without
+    JSON_PRECISE_STREAM_POSITION, no adapter has lookahead, so this is always a
+    no-op and the terminating character stays consumed.
+
+    Scanning may continue after this call: @a next_unget is cleared, and the
+    character is read from the input again instead of being replayed from
+    @a current. A pending unget of EOF needs no special case, because reaching
+    EOF leaves no lookahead to release.
+    */
+    void release_lookahead()
+    {
+        release_lookahead_impl(std::integral_constant<bool, can_release_lookahead> {});
+    }
+
 #if JSON_DIAGNOSTIC_POSITIONS
     /// return the offset of the first character of the last read token; unlike
     /// the token's parsed value, this accounts for escape sequences
@@ -2173,6 +2253,564 @@ scan_number_done:
         }
     }
 
+    /////////////////////
+    // error recovery
+    /////////////////////
+
+    /*!
+    @brief make the best of the token that scan() rejected
+
+    Called by the parser after scan() returned token_type::parse_error and the
+    SAX parser asked to recover from the error (see #3989). Keeps what can be
+    read of the token and skips the rest:
+
+    - A string keeps its characters. An unknown escape stands for the escaped
+      character itself (as in JavaScript), an invalid `\u` escape and ill-formed
+      UTF-8 become U+FFFD, and a control character is kept. A line break or the
+      end of the input ends a string that lacks its closing quote.
+    - A number keeps its longest valid prefix, e.g. `1` for `1.` or `1e+`.
+    - A block comment that is not closed runs to the end of the input.
+    - Anything else is skipped.
+
+    The rest of an invalid token is skipped up to the next delimiter
+    (whitespace, a structural character, or a quote). A delimiter that the
+    invalid token consumed is returned to the input, so that the next scan()
+    reads it.
+
+    @return token_type::value_string or a number token type if a string or a
+            number could be read, token_type::end_of_input for a block comment
+            that is not closed, token_type::uninitialized otherwise
+    */
+    token_type recover_token()
+    {
+        const resume_kind resume = string_error_resume;
+        const int codepoint = string_error_codepoint;
+        string_error_resume = resume_kind::character;
+        string_error_codepoint = -1;
+
+        if (error_message_starts_with("invalid string"))
+        {
+            return recover_string(resume, codepoint);
+        }
+
+        if (error_message_starts_with("invalid number"))
+        {
+            return recover_number();
+        }
+
+        if (error_message_starts_with("invalid comment; missing"))
+        {
+            // the comment runs to the end of the input
+            return token_type::end_of_input;
+        }
+
+        skip_to_delimiter();
+        return token_type::uninitialized;
+    }
+
+    /*!
+    @brief return the token that scan() read last to the input, so that the
+           next scan() reads it again
+
+    Called by the parser when recovering from an error. The token must be a
+    single character (',', ':', '[', ']', '{', or '}') or the end of the
+    input, and scan() must have read it last.
+    */
+    void unget_token()
+    {
+        JSON_ASSERT(!next_unget);
+        unget();
+    }
+
+    /*!
+    @brief let the token string for the next error begin at the current character
+
+    The token string of an error reaches back to the beginning of the last
+    string or number. After an error, the parser calls this function so that
+    the next error does not report (and, with many errors, copy) everything
+    read since then.
+    */
+    void restart_token_string()
+    {
+        restart_token_string_impl(std::integral_constant<bool, lazy_token_string> {});
+    }
+
+  private:
+    /// how recover_string() continues after the error scan_string() reported
+    enum class resume_kind : std::uint8_t
+    {
+        /// current is the next character of the string (or the end of input)
+        character,
+        /// current is the character escaped by the preceding backslash
+        escaped_character,
+        /// current is the last character of a complete escape
+        after_escape
+    };
+
+    /// whether error_message begins with @a prefix
+    bool error_message_starts_with(const char* prefix) const noexcept
+    {
+        const char* message = error_message;
+        while (*prefix != '\0')
+        {
+            if (*message++ != *prefix++)
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /// whether current ends an invalid token (see recover_token())
+    bool current_is_delimiter() const noexcept
+    {
+        switch (current)
+        {
+            case ' ':
+            case '\t':
+            case '\n':
+            case '\r':
+            case '[':
+            case ']':
+            case '{':
+            case '}':
+            case ',':
+            case ':':
+            case '\"':
+#if !JSON_STRICT_NUL_HANDLING
+            case '\0':
+#endif
+            case char_traits<char_type>::eof():
+                return true;
+
+            case '/':
+                return ignore_comments;
+
+            default:
+                return false;
+        }
+    }
+
+    /// skip the rest of an invalid token and return its delimiter to the input
+    void skip_to_delimiter()
+    {
+        while (!current_is_delimiter())
+        {
+            get();
+        }
+
+        if (current != char_traits<char_type>::eof())
+        {
+            unget();
+        }
+    }
+
+    /// append U+FFFD REPLACEMENT CHARACTER to token_buffer
+    void add_replacement_character()
+    {
+        add(0xEF);
+        add(0xBF);
+        add(0xBD);
+    }
+
+    /// append the UTF-8 encoding of @a codepoint (not a surrogate) to token_buffer
+    void add_codepoint(const int codepoint)
+    {
+        JSON_ASSERT(0x00 <= codepoint && codepoint <= 0x10FFFF);
+        const auto cp = static_cast<unsigned int>(codepoint);
+        if (cp < 0x80)
+        {
+            add(static_cast<char_int_type>(cp));
+        }
+        else if (cp <= 0x7FF)
+        {
+            add(static_cast<char_int_type>(0xC0u | (cp >> 6u)));
+            add(static_cast<char_int_type>(0x80u | (cp & 0x3Fu)));
+        }
+        else if (cp <= 0xFFFF)
+        {
+            add(static_cast<char_int_type>(0xE0u | (cp >> 12u)));
+            add(static_cast<char_int_type>(0x80u | ((cp >> 6u) & 0x3Fu)));
+            add(static_cast<char_int_type>(0x80u | (cp & 0x3Fu)));
+        }
+        else
+        {
+            add(static_cast<char_int_type>(0xF0u | (cp >> 18u)));
+            add(static_cast<char_int_type>(0x80u | ((cp >> 12u) & 0x3Fu)));
+            add(static_cast<char_int_type>(0x80u | ((cp >> 6u) & 0x3Fu)));
+            add(static_cast<char_int_type>(0x80u | (cp & 0x3Fu)));
+        }
+    }
+
+    /// append a code point read from a `\u` escape; a surrogate becomes U+FFFD
+    void add_escaped_codepoint(const int codepoint)
+    {
+        if (0xD800 <= codepoint && codepoint <= 0xDFFF)
+        {
+            add_replacement_character();
+        }
+        else
+        {
+            add_codepoint(codepoint);
+        }
+    }
+
+    /*!
+    @brief remove an incomplete UTF-8 sequence from the end of token_buffer
+
+    next_byte_in_range() adds the bytes of a sequence as it checks them, so
+    when it rejects a byte, the beginning of the sequence is already in
+    token_buffer, which otherwise holds only complete sequences.
+
+    @return whether an incomplete sequence was removed
+    */
+    bool remove_incomplete_utf8_sequence()
+    {
+        std::size_t lead = token_buffer.size();
+        std::size_t continuation_bytes = 0;
+        while (lead > 0 && continuation_bytes < 3
+                && (static_cast<unsigned char>(token_buffer[lead - 1]) & 0xC0u) == 0x80u)
+        {
+            --lead;
+            ++continuation_bytes;
+        }
+        if (lead == 0)
+        {
+            return false;
+        }
+
+        const auto lead_byte = static_cast<unsigned char>(token_buffer[lead - 1]);
+        const std::size_t expected = (lead_byte >= 0xF0) ? 3 : (lead_byte >= 0xE0) ? 2 : (lead_byte >= 0xC0) ? 1 : 0;
+        if (continuation_bytes >= expected)
+        {
+            return false;
+        }
+
+        token_buffer.resize(lead - 1);
+        return true;
+    }
+
+    /*!
+    @brief read the UTF-8 sequence that begins with current, which is not ASCII
+    @return whether the next character must be read; false if current still
+            needs to be handled, because it does not belong to the sequence
+    */
+    bool recover_utf8_sequence()
+    {
+        // the number of continuation bytes and the range of the first one;
+        // see the ranges in scan_string()
+        std::size_t count = 0;
+        char_int_type low = 0x80;
+        char_int_type high = 0xBF;
+        if (current >= 0xC2 && current <= 0xDF)
+        {
+            count = 1;
+        }
+        else if (current >= 0xE0 && current <= 0xEF)
+        {
+            count = 2;
+            low = (current == 0xE0) ? 0xA0 : 0x80;
+            high = (current == 0xED) ? 0x9F : 0xBF;
+        }
+        else if (current >= 0xF0 && current <= 0xF4)
+        {
+            count = 3;
+            low = (current == 0xF0) ? 0x90 : 0x80;
+            high = (current == 0xF4) ? 0x8F : 0xBF;
+        }
+        else
+        {
+            // an ill-formed byte
+            add_replacement_character();
+            return true;
+        }
+
+        const std::size_t start = token_buffer.size();
+        add(current);
+        for (std::size_t i = 0; i < count; ++i)
+        {
+            get();
+            if (current < low || current > high)
+            {
+                token_buffer.resize(start);
+                add_replacement_character();
+                return false;
+            }
+            add(current);
+            low = 0x80;
+            high = 0xBF;
+        }
+        return true;
+    }
+
+    /*!
+    @brief read the low surrogate that must follow the high surrogate @a high
+    @return whether the next character must be read; false if current still
+            needs to be handled
+    */
+    bool recover_low_surrogate(int high)
+    {
+        while (true)
+        {
+            if (get() != '\\')
+            {
+                add_replacement_character();
+                return false;
+            }
+            if (get() != 'u')
+            {
+                add_replacement_character();
+                // not 'u', so this does not come back here
+                return recover_escape();
+            }
+
+            const int low = get_codepoint();
+            if (low == -1)
+            {
+                add_replacement_character();
+                return false;
+            }
+            if (0xDC00 <= low && low <= 0xDFFF)
+            {
+                add_codepoint(static_cast<int>((static_cast<unsigned int>(high) << 10u)
+                                               + static_cast<unsigned int>(low) - 0x35FDC00u));
+                return true;
+            }
+
+            // high has no low surrogate
+            add_replacement_character();
+            if (low < 0xD800 || low > 0xDBFF)
+            {
+                add_codepoint(low);
+                return true;
+            }
+            // another high surrogate
+            high = low;
+        }
+    }
+
+    /*!
+    @brief read the escape whose backslash was read; current is the escaped character
+    @return whether the next character must be read; false if current still
+            needs to be handled
+    */
+    bool recover_escape()
+    {
+        switch (current)
+        {
+            case '\"':
+                add('\"');
+                return true;
+            case '\\':
+                add('\\');
+                return true;
+            case '/':
+                add('/');
+                return true;
+            case 'b':
+                add('\b');
+                return true;
+            case 'f':
+                add('\f');
+                return true;
+            case 'n':
+                add('\n');
+                return true;
+            case 'r':
+                add('\r');
+                return true;
+            case 't':
+                add('\t');
+                return true;
+
+            case 'u':
+            {
+                const int codepoint = get_codepoint();
+                if (codepoint == -1)
+                {
+                    add_replacement_character();
+                    return false;
+                }
+                if (0xD800 <= codepoint && codepoint <= 0xDBFF)
+                {
+                    return recover_low_surrogate(codepoint);
+                }
+                add_escaped_codepoint(codepoint);
+                return true;
+            }
+
+            // an unknown escape stands for the escaped character
+            default:
+                return false;
+        }
+    }
+
+    /*!
+    @brief read the rest of a string after scan_string() rejected it
+
+    token_buffer holds what scan_string() read before the error. See
+    recover_token() for how errors are repaired.
+
+    @param[in] resume     how to continue, see resume_kind
+    @param[in] codepoint  for a high surrogate followed by an escape of another
+                          code point: that code point; -1 otherwise
+    */
+    token_type recover_string(const resume_kind resume, const int codepoint)
+    {
+        // whether the next character must be read before it can be handled
+        bool fetch = false;
+
+        if (error_message_starts_with("invalid string: surrogate")
+                || error_message_starts_with("invalid string: '\\u'"))
+        {
+            add_replacement_character();
+        }
+        else if (error_message_starts_with("invalid string: ill-formed UTF-8")
+                 && remove_incomplete_utf8_sequence())
+        {
+            add_replacement_character();
+        }
+
+        switch (resume)
+        {
+            case resume_kind::escaped_character:
+                fetch = recover_escape();
+                break;
+            case resume_kind::after_escape:
+                if (0xD800 <= codepoint && codepoint <= 0xDBFF)
+                {
+                    fetch = recover_low_surrogate(codepoint);
+                }
+                else
+                {
+                    if (codepoint != -1)
+                    {
+                        add_escaped_codepoint(codepoint);
+                    }
+                    fetch = true;
+                }
+                break;
+            case resume_kind::character:
+            default:
+                break;
+        }
+
+        while (true)
+        {
+            if (fetch)
+            {
+                get();
+            }
+            fetch = true;
+
+            switch (current)
+            {
+                case '\"':
+                // a line break or the end of the input ends a string that
+                // lacks its closing quote
+                case '\n':
+                case '\r':
+                case char_traits<char_type>::eof():
+                    return token_type::value_string;
+
+#if !JSON_STRICT_NUL_HANDLING
+                case '\0':
+                    // the end of the input, see scan()
+                    unget();
+                    return token_type::value_string;
+#endif
+
+                case '\\':
+                    get();
+                    fetch = recover_escape();
+                    break;
+
+                default:
+                    if (current < 0x80)
+                    {
+                        // including control characters
+                        add(current);
+                    }
+                    else
+                    {
+                        fetch = recover_utf8_sequence();
+                    }
+                    break;
+            }
+        }
+    }
+
+    /*!
+    @brief keep the longest valid prefix of a number that scan_number() rejected
+
+    token_buffer holds the characters scan_number() accepted before the error,
+    so the prefix ends at its last digit.
+    */
+    token_type recover_number()
+    {
+        // only size(), operator[], and resize() are used, which every string
+        // type the library supports provides
+        std::size_t length = token_buffer.size();
+        while (length != 0 && (token_buffer[length - 1] < '0' || token_buffer[length - 1] > '9'))
+        {
+            --length;
+        }
+        token_buffer.resize(length);
+
+        if (length == 0)
+        {
+            skip_to_delimiter();
+            return token_type::uninitialized;
+        }
+
+        if (decimal_point_position >= length)
+        {
+            decimal_point_position = std::string::npos;
+        }
+
+        std::size_t exponent = std::string::npos;
+        for (std::size_t i = 0; i < length; ++i)
+        {
+            if (token_buffer[i] == 'e' || token_buffer[i] == 'E')
+            {
+                exponent = i;
+                break;
+            }
+        }
+        const std::size_t mantissa_end = (exponent == std::string::npos) ? length : exponent;
+        token_type number_type = token_type::value_unsigned;
+        if (decimal_point_position != std::string::npos || exponent != std::string::npos)
+        {
+            number_type = token_type::value_float;
+        }
+        else if (token_buffer[0] == '-')
+        {
+            number_type = token_type::value_integer;
+        }
+
+        const token_type result = convert_number(number_type, mantissa_end);
+        skip_to_delimiter();
+        return result;
+    }
+
+    /// seekable adapter: the token string begins at current, which was consumed
+    void restart_token_string_impl(std::true_type /*lazy*/) noexcept
+    {
+        const std::size_t consumed = ia.get_consumed_count();
+        token_string_start = (consumed > 0 && current != char_traits<char_type>::eof()) ? consumed - 1 : consumed;
+    }
+
+    /// streaming adapter: the token string begins at current; a character
+    /// that was put back is copied again when it is read again
+    void restart_token_string_impl(std::false_type /*lazy*/)
+    {
+        token_string.clear();
+        if (!next_unget && current != char_traits<char_type>::eof())
+        {
+            token_string.push_back(char_traits<char_type>::to_char_type(current));
+        }
+    }
+
   private:
     /// input adapter
     InputAdapterType ia;
@@ -2213,6 +2851,13 @@ scan_number_done:
     /// a description of occurred lexer errors
     const char* error_message = "";
 
+    /// how recover_token() continues a string that scan_string() rejected;
+    /// set only on the error paths that need more than error_message
+    resume_kind string_error_resume = resume_kind::character;
+    /// the code point of the second escape when a high surrogate is followed
+    /// by an escape that is not a low surrogate; -1 otherwise
+    int string_error_codepoint = -1;
+
     // number values
     number_integer_t value_integer = 0;
     number_unsigned_t value_unsigned = 0;

include/nlohmann/detail/input/parser.hpp

@@ -98,15 +98,24 @@ class parser
         if (callback)
         {
             json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
-            sax_parse_internal(&sdp);
+            sax_parse_internal<false>(&sdp);
 
-            // in strict mode, input must be completely read
+            if (strict)
-            if (strict && (get_token() != token_type::end_of_input))
             {
-                sdp.parse_error(m_lexer.get_position(),
+                // in strict mode, input must be completely read
-                                m_lexer.get_token_string(),
+                if (get_token() != token_type::end_of_input)
-                                parse_error::create(101, m_lexer.get_position(),
+                {
-                                                    exception_message(token_type::end_of_input, "value"), nullptr));
+                    sdp.parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(),
+                                                        exception_message(token_type::end_of_input, "value"), nullptr));
+                }
+            }
+            else
+            {
+                // the caller keeps using the input: position it right after
+                // the value by leaving the character that terminated it
+                m_lexer.release_lookahead();
             }
 
             // in case of an error, return a discarded value
@@ -126,14 +135,22 @@ class parser
         else
         {
             json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
-            sax_parse_internal(&sdp);
+            sax_parse_internal<false>(&sdp);
 
-            // in strict mode, input must be completely read
+            if (strict)
-            if (strict && (get_token() != token_type::end_of_input))
             {
-                sdp.parse_error(m_lexer.get_position(),
+                // in strict mode, input must be completely read
-                                m_lexer.get_token_string(),
+                if (get_token() != token_type::end_of_input)
-                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
+                {
+                    sdp.parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
+                }
+            }
+            else
+            {
+                // see above
+                m_lexer.release_lookahead();
             }
 
             // in case of an error, return a discarded value
@@ -156,32 +173,86 @@ class parser
     bool accept(const bool strict = true)
     {
         json_sax_acceptor<BasicJsonType> sax_acceptor;
-        return sax_parse(&sax_acceptor, strict);
+        return sax_parse_impl<false>(&sax_acceptor, strict);
     }
 
+    /*!
+    @brief public SAX interface
+
+    If the SAX parser's parse_error() returns true, the parser recovers from
+    the error: it repairs the input and continues (see #3989).
+
+    @param[in] sax     the SAX parser
+    @param[in] strict  whether to expect the last token to be EOF
+    @return whether the input was parsed without errors and no SAX event
+            returned false
+    */
     template<typename SAX>
     JSON_HEDLEY_NON_NULL(2)
     bool sax_parse(SAX* sax, const bool strict = true)
     {
-        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
+        return sax_parse_impl<true>(sax, strict);
-        const bool result = sax_parse_internal(sax);
-
-        // strict mode: next byte must be EOF
-        if (result && strict && (get_token() != token_type::end_of_input))
-        {
-            return sax->parse_error(m_lexer.get_position(),
-                                    m_lexer.get_token_string(),
-                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
-        }
-
-        return result;
     }
 
   private:
-    template<typename SAX>
+    /// what sax_parse_internal() does after an object key was expected
+    enum class next_step : std::uint8_t
+    {
+        /// stop parsing
+        stop,
+        /// parse a value that begins with last_token
+        parse_value,
+        /// evaluate the state of the innermost container, which reads
+        /// last_token again
+        evaluate_state
+    };
+
+    template<bool AllowRecovery, typename SAX>
+    JSON_HEDLEY_NON_NULL(2)
+    bool sax_parse_impl(SAX* sax, const bool strict)
+    {
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
+        const bool result = sax_parse_internal<AllowRecovery>(sax);
+
+        if (result)
+        {
+            if (strict)
+            {
+                // strict mode: next byte must be EOF; after recovering from an
+                // error, the end of the input may already have been read
+                if (last_token != token_type::end_of_input && get_token() != token_type::end_of_input)
+                {
+                    // the value is complete, so there is nothing to recover
+                    static_cast<void>(report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr),
+                                                   std::integral_constant<bool, AllowRecovery> {}));
+                    return false;
+                }
+            }
+            else
+            {
+                // the caller keeps using the input: position it right after
+                // the value by leaving the character that terminated it
+                m_lexer.release_lookahead();
+            }
+        }
+
+        return result && !error_reported;
+    }
+
+    /*!
+    @brief parse a JSON value and pass it to a SAX parser
+
+    @tparam AllowRecovery  whether to recover from an error if the SAX parser's
+                           parse_error() returns true; false for the SAX parsers
+                           of parse() and accept(), which never do, so that no
+                           code for recovering is generated for them
+    */
+    template<bool AllowRecovery, typename SAX>
     JSON_HEDLEY_NON_NULL(2)
     bool sax_parse_internal(SAX* sax)
     {
+        const std::integral_constant<bool, AllowRecovery> allow_recovery{};
+
         // stack to remember the hierarchy of structured values we are parsing
         // true = array; false = object
         std::vector<bool> states;
@@ -212,12 +283,18 @@ class parser
                             break;
                         }
 
-                        // parse key
+                        // remember we are now inside an object
+                        states.push_back(false);
+
+                        // parse key (the steps of parse_key(), which are
+                        // repeated here and below for speed)
                         if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                         {
-                            return sax->parse_error(m_lexer.get_position(),
+                            if (!continue_after(key_error(sax, allow_recovery, false), skip_to_state_evaluation))
-                                                    m_lexer.get_token_string(),
+                            {
-                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr));
+                                return false;
+                            }
+                            continue;
                         }
                         if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
                         {
@@ -227,14 +304,13 @@ class parser
                         // parse separator (:)
                         if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
                         {
-                            return sax->parse_error(m_lexer.get_position(),
+                            if (!continue_after(key_error(sax, allow_recovery, true), skip_to_state_evaluation))
-                                                    m_lexer.get_token_string(),
+                            {
-                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr));
+                                return false;
+                            }
+                            continue;
                         }
 
-                        // remember we are now inside an object
-                        states.push_back(false);
-
                         // parse values
                         get_token();
                         continue;
@@ -270,9 +346,11 @@ class parser
 
                         if (JSON_HEDLEY_UNLIKELY(!std::isfinite(res)))
                         {
-                            return sax->parse_error(m_lexer.get_position(),
+                            if (!overflow_error(sax, res, allow_recovery))
-                                                    m_lexer.get_token_string(),
+                            {
-                                                    out_of_range::create(406, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr));
+                                return false;
+                            }
+                            break;
                         }
 
                         if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, m_lexer.get_string())))
@@ -340,23 +418,63 @@ class parser
                     case token_type::parse_error:
                     {
                         // using "uninitialized" to avoid an "expected" message
-                        return sax->parse_error(m_lexer.get_position(),
+                        if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::uninitialized, "value"), nullptr), allow_recovery))
-                                                m_lexer.get_token_string(),
+                        {
-                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::uninitialized, "value"), nullptr));
+                            return false;
+                        }
+
+                        // recover: keep what can be read of the token
+                        recover_token();
+                        if (last_token != token_type::uninitialized)
+                        {
+                            // a string or a number
+                            continue;
+                        }
+                        if (states.empty())
+                        {
+                            // look for the value after the garbage
+                            if (!skip_to_value())
+                            {
+                                return false;
+                            }
+                            continue;
+                        }
+                        // nothing could be read
+                        if (JSON_HEDLEY_UNLIKELY(!sax->null()))
+                        {
+                            return false;
+                        }
+                        break;
                     }
                     case token_type::end_of_input:
                     {
                         if (JSON_HEDLEY_UNLIKELY(m_lexer.get_position().chars_read_total == 1))
                         {
-                            return sax->parse_error(m_lexer.get_position(),
+                            // there is nothing to recover
-                                                    m_lexer.get_token_string(),
+                            static_cast<void>(report_error(sax, parse_error::create(101, m_lexer.get_position(),
-                                                    parse_error::create(101, m_lexer.get_position(),
+                                                           "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr), allow_recovery));
-                                                            "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
+                            return false;
                         }
 
-                        return sax->parse_error(m_lexer.get_position(),
+                        if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr), allow_recovery))
-                                                m_lexer.get_token_string(),
+                        {
-                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr));
+                            return false;
+                        }
+
+                        // recover: the input ends where a value is missing
+                        if (states.empty())
+                        {
+                            // there is no value
+                            return false;
+                        }
+                        if (!recover_missing_value(sax, states))
+                        {
+                            return false;
+                        }
+                        // the state evaluation reads the token again
+                        m_lexer.unget_token();
+                        skip_to_state_evaluation = true;
+                        continue;
                     }
                     case token_type::uninitialized:
                     case token_type::end_array:
@@ -366,9 +484,35 @@ class parser
                     case token_type::literal_or_value:
                     default: // the last token was unexpected
                     {
-                        return sax->parse_error(m_lexer.get_position(),
+                        if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr), allow_recovery))
-                                                m_lexer.get_token_string(),
+                        {
-                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr));
+                            return false;
+                        }
+
+                        // recover
+                        if (states.empty())
+                        {
+                            // look for the value after the garbage
+                            if (!skip_to_value())
+                            {
+                                return false;
+                            }
+                            continue;
+                        }
+                        if (last_token == token_type::name_separator)
+                        {
+                            // a stray ':'; the value may follow
+                            get_token();
+                            continue;
+                        }
+                        if (!recover_missing_value(sax, states))
+                        {
+                            return false;
+                        }
+                        // the state evaluation reads the token again
+                        m_lexer.unget_token();
+                        skip_to_state_evaluation = true;
+                        continue;
                     }
                 }
             }
@@ -418,9 +562,30 @@ class parser
                     continue;
                 }
 
-                return sax->parse_error(m_lexer.get_position(),
+                if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_array, "array"), nullptr), allow_recovery))
-                                        m_lexer.get_token_string(),
+                {
-                                        parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_array, "array"), nullptr));
+                    return false;
+                }
+
+                // recover
+                if (last_token == token_type::end_of_input)
+                {
+                    // the input ends inside the array
+                    return close_containers(sax, states);
+                }
+                if (last_token == token_type::end_object)
+                {
+                    // a wrong closing bracket closes the innermost container
+                    if (JSON_HEDLEY_UNLIKELY(!sax->end_array()))
+                    {
+                        return false;
+                    }
+                    states.pop_back();
+                    skip_to_state_evaluation = true;
+                }
+                // otherwise, a missing ',' (or a stray ':', which value
+                // parsing drops): the next value begins here
+                continue;
             }
 
             // states.back() is false -> object
@@ -437,11 +602,12 @@ class parser
                     // parse key
                     if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                     {
-                        return sax->parse_error(m_lexer.get_position(),
+                        if (!continue_after(key_error(sax, allow_recovery, false), skip_to_state_evaluation))
-                                                m_lexer.get_token_string(),
+                        {
-                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr));
+                            return false;
+                        }
+                        continue;
                     }
-
                     if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
                     {
                         return false;
@@ -450,9 +616,11 @@ class parser
                     // parse separator (:)
                     if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
                     {
-                        return sax->parse_error(m_lexer.get_position(),
+                        if (!continue_after(key_error(sax, allow_recovery, true), skip_to_state_evaluation))
-                                                m_lexer.get_token_string(),
+                        {
-                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr));
+                            return false;
+                        }
+                        continue;
                     }
 
                     // parse values
@@ -479,12 +647,479 @@ class parser
                 continue;
             }
 
-            return sax->parse_error(m_lexer.get_position(),
+            if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_object, "object"), nullptr), allow_recovery))
-                                    m_lexer.get_token_string(),
+            {
-                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_object, "object"), nullptr));
+                return false;
+            }
+
+            // recover
+            if (last_token == token_type::end_of_input)
+            {
+                // the input ends inside the object
+                return close_containers(sax, states);
+            }
+            if (last_token == token_type::end_array)
+            {
+                // a wrong closing bracket closes the innermost container
+                if (JSON_HEDLEY_UNLIKELY(!sax->end_object()))
+                {
+                    return false;
+                }
+                states.pop_back();
+                skip_to_state_evaluation = true;
+                continue;
+            }
+            if (!continue_after(recover_member(sax, allow_recovery), skip_to_state_evaluation))
+            {
+                return false;
+            }
         }
     }
 
+    /*!
+    @brief continue sax_parse_internal() after a recovery
+    @return whether to continue parsing
+    */
+    bool continue_after(const next_step step, bool& skip_to_state_evaluation)
+    {
+        if (step == next_step::evaluate_state)
+        {
+            // the state evaluation reads the token again
+            m_lexer.unget_token();
+            skip_to_state_evaluation = true;
+        }
+        return step != next_step::stop;
+    }
+
+    /// the parser for parse() and accept() never recovers: stop parsing
+    static std::false_type continue_after(std::false_type /*step*/, bool& /*skip_to_state_evaluation*/) noexcept
+    {
+        return {};
+    }
+
+    /*!
+    @brief parse an object key and the name separator (:) after it
+
+    last_token is the token where the key is expected. sax_parse_internal()
+    repeats these steps rather than calling this function, which is used
+    when recovering from an error.
+
+    @return next_step::parse_value if the value follows, with last_token its
+            first token; next_step::evaluate_state if the object's state is
+            to be evaluated after recovering from an error; next_step::stop
+            to stop parsing
+    */
+    template<typename SAX>
+    next_step parse_key(SAX* sax)
+    {
+        const std::true_type allow_recovery{};
+
+        if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
+        {
+            return key_error(sax, allow_recovery, false);
+        }
+
+        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
+        {
+            return next_step::stop;
+        }
+
+        // parse separator (:)
+        if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
+        {
+            return key_error(sax, allow_recovery, true);
+        }
+
+        // the value begins with the next token
+        get_token();
+        return next_step::parse_value;
+    }
+
+    /*!
+    @brief report a number that is too large for number_float_t, and recover
+           from the error by passing the value on; the SAX parser gets the
+           number's text as well
+
+    This is a separate function, as reading other numbers is measurably
+    slower if the error is handled where they are read.
+
+    @param[in] sax    the SAX parser
+    @param[in] value  the value that is not finite
+    @return whether to continue parsing
+    */
+    template<typename SAX, typename AllowRecovery>
+    bool overflow_error(SAX* sax, const number_float_t value, AllowRecovery allow_recovery)
+    {
+        if (!report_error(sax, out_of_range::create(406, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr), allow_recovery))
+        {
+            return false;
+        }
+        return sax->number_float(value, m_lexer.get_string());
+    }
+
+    /*!
+    @brief report a missing key, or a missing name separator (:) after the
+           key; the parser for parse() and accept() never recovers
+
+    @param[in] key_read  whether the key was read, so that the name separator
+                         is missing
+    @return std::false_type, see report_error()
+    */
+    template<typename SAX>
+    std::false_type key_error(SAX* sax, std::false_type allow_recovery, const bool key_read)
+    {
+        return report_error(sax, parse_error::create(101, m_lexer.get_position(), key_read
+                            ? exception_message(token_type::name_separator, "object separator")
+                            : exception_message(token_type::value_string, "object key"), nullptr), allow_recovery);
+    }
+
+    /*!
+    @brief report a missing key, or a missing name separator (:) after the
+           key, and recover from it
+
+    @param[in] key_read  whether the key was read, so that the name separator
+                         is missing
+    */
+    template<typename SAX>
+    next_step key_error(SAX* sax, std::true_type allow_recovery, const bool key_read)
+    {
+        if (!key_read)
+        {
+            if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr), allow_recovery))
+            {
+                return next_step::stop;
+            }
+            return recover_key(sax);
+        }
+
+        if (!report_error(sax, parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr), allow_recovery))
+        {
+            return next_step::stop;
+        }
+        return recover_name_separator(sax);
+    }
+
+    /////////////////////
+    // error recovery
+    /////////////////////
+
+    /*
+    The functions below repair an error after the SAX parser's parse_error()
+    returned true (see #3989). Each mistake is repaired by the smallest local
+    edit: a missing ',' or ':' is inserted, a stray token is removed, what can
+    be read of an invalid string or number is kept (see
+    lexer::recover_token()), a missing value becomes null, a wrong closing
+    bracket closes the innermost container, and the end of the input closes
+    all of them. The events stay balanced, and every key() is followed by
+    exactly one value.
+
+    A repair hands a token to the state evaluation, by returning it to the
+    lexer (lexer::unget_token()) so that the state evaluation reads it again,
+    only if it is ',', ']', '}', or the end of the input. The state evaluation
+    hands a token to value or key parsing only if it is none of them, so a
+    token is never handed back and forth. Every other step reads a token or
+    closes a container, so parsing always ends.
+    */
+
+    /*!
+    @brief report an error to the SAX parser; the parser for parse() and
+           accept() never recovers
+
+    @return std::false_type rather than false: its value is known where the
+            function is called even if the call is not inlined, so the code
+            for recovering is not generated
+    */
+    template<typename SAX, typename Exception>
+    std::false_type report_error(SAX* sax, const Exception& ex, std::false_type /*allow_recovery*/)
+    {
+        error_reported = true;
+        static_cast<void>(sax->parse_error(m_lexer.get_position(), m_lexer.get_token_string(), ex));
+        return {};
+    }
+
+    /*!
+    @brief report an error to the SAX parser
+    @return whether to recover from the error
+    */
+    template<typename SAX, typename Exception>
+    bool report_error(SAX* sax, const Exception& ex, std::true_type /*allow_recovery*/)
+    {
+        const std::size_t position = m_lexer.get_position().chars_read_total;
+        if (error_reported && position == last_error_position && last_token == last_error_token)
+        {
+            // a repair handed on the token of the error it repaired; the
+            // token was reported already, and the SAX parser asked to recover
+            return true;
+        }
+
+        error_reported = true;
+        last_error_position = position;
+        last_error_token = last_token;
+
+        if (!sax->parse_error(m_lexer.get_position(), m_lexer.get_token_string(), ex))
+        {
+            return false;
+        }
+
+        // the token string of the next error begins here
+        m_lexer.restart_token_string();
+        return true;
+    }
+
+    /*!
+    @brief keep what can be read of the token that the lexer rejected
+
+    The error was reported for the rejected token, so it is not reported again
+    for the token it is repaired to (see lexer::recover_token()).
+    */
+    token_type recover_token()
+    {
+        last_token = m_lexer.recover_token();
+        last_error_position = m_lexer.get_position().chars_read_total;
+        last_error_token = last_token;
+        return last_token;
+    }
+
+    /// pass the end events of all open containers
+    template<typename SAX>
+    bool close_containers(SAX* sax, std::vector<bool>& states)
+    {
+        while (!states.empty())
+        {
+            const bool is_array = states.back();
+            states.pop_back();
+            if (JSON_HEDLEY_UNLIKELY(is_array ? !sax->end_array() : !sax->end_object()))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /*!
+    @brief read tokens until one begins a value, skipping everything before
+           the top-level value
+    @return whether a value begins with last_token
+    */
+    bool skip_to_value()
+    {
+        while (true)
+        {
+            switch (get_token())
+            {
+                case token_type::begin_array:
+                case token_type::begin_object:
+                case token_type::literal_false:
+                case token_type::literal_null:
+                case token_type::literal_true:
+                case token_type::value_float:
+                case token_type::value_integer:
+                case token_type::value_string:
+                case token_type::value_unsigned:
+                    return true;
+
+                case token_type::end_of_input:
+                    return false;
+
+                case token_type::parse_error:
+                    recover_token();
+                    if (last_token != token_type::uninitialized)
+                    {
+                        return true;
+                    }
+                    break;
+
+                case token_type::uninitialized:
+                case token_type::end_array:
+                case token_type::end_object:
+                case token_type::name_separator:
+                case token_type::value_separator:
+                case token_type::literal_or_value:
+                default:
+                    break;
+            }
+        }
+    }
+
+    /*!
+    @brief skip the rest of an object member that cannot be read
+
+    Reads tokens, beginning with last_token, until a ',', '}', or ']' that is
+    not inside a container that begins in the skipped tokens, or the end of
+    the input.
+    */
+    void skip_member()
+    {
+        std::size_t depth = 0;
+        while (true)
+        {
+            switch (last_token)
+            {
+                case token_type::begin_array:
+                case token_type::begin_object:
+                    ++depth;
+                    break;
+
+                case token_type::end_array:
+                case token_type::end_object:
+                    if (depth == 0)
+                    {
+                        return;
+                    }
+                    --depth;
+                    break;
+
+                case token_type::value_separator:
+                    if (depth == 0)
+                    {
+                        return;
+                    }
+                    break;
+
+                case token_type::end_of_input:
+                    return;
+
+                case token_type::parse_error:
+                    recover_token();
+                    break;
+
+                case token_type::uninitialized:
+                case token_type::literal_true:
+                case token_type::literal_false:
+                case token_type::literal_null:
+                case token_type::value_string:
+                case token_type::value_unsigned:
+                case token_type::value_integer:
+                case token_type::value_float:
+                case token_type::name_separator:
+                case token_type::literal_or_value:
+                default:
+                    break;
+            }
+            get_token();
+        }
+    }
+
+    /*!
+    @brief pass a value where it is missing
+
+    last_token is ',', ']', '}', or the end of the input, where a value was
+    expected. In an object, the key gets null; in an array, a ',' where a
+    value is missing stands for null (as in JavaScript), while an array that
+    ends there just ends.
+    */
+    template<typename SAX>
+    bool recover_missing_value(SAX* sax, const std::vector<bool>& states)
+    {
+        JSON_ASSERT(!states.empty());
+        if (!states.back() || last_token == token_type::value_separator)
+        {
+            return sax->null();
+        }
+        return true;
+    }
+
+    /// recover from a missing key; last_token is where it was expected
+    template<typename SAX>
+    next_step recover_key(SAX* sax)
+    {
+        switch (last_token)
+        {
+            case token_type::value_separator:
+            case token_type::end_object:
+            case token_type::end_array:
+            case token_type::end_of_input:
+                // no member: the object's state handles the token
+                return next_step::evaluate_state;
+
+            case token_type::parse_error:
+                recover_token();
+                if (last_token == token_type::value_string)
+                {
+                    // a key that could be repaired
+                    return parse_key(sax);
+                }
+                skip_member();
+                return next_step::evaluate_state;
+
+            case token_type::uninitialized:
+            case token_type::literal_true:
+            case token_type::literal_false:
+            case token_type::literal_null:
+            case token_type::value_string:
+            case token_type::value_unsigned:
+            case token_type::value_integer:
+            case token_type::value_float:
+            case token_type::begin_array:
+            case token_type::begin_object:
+            case token_type::name_separator:
+            case token_type::literal_or_value:
+            default:
+                // a member without a key
+                skip_member();
+                return next_step::evaluate_state;
+        }
+    }
+
+    /// recover from a missing name separator (:) after the key; last_token
+    /// is where it was expected
+    template<typename SAX>
+    next_step recover_name_separator(SAX* sax)
+    {
+        switch (last_token)
+        {
+            case token_type::value_separator:
+            case token_type::end_object:
+            case token_type::end_array:
+            case token_type::end_of_input:
+                // the value is missing as well
+                return sax->null() ? next_step::evaluate_state : next_step::stop;
+
+            case token_type::uninitialized:
+            case token_type::literal_true:
+            case token_type::literal_false:
+            case token_type::literal_null:
+            case token_type::value_string:
+            case token_type::value_unsigned:
+            case token_type::value_integer:
+            case token_type::value_float:
+            case token_type::begin_array:
+            case token_type::begin_object:
+            case token_type::name_separator:
+            case token_type::parse_error:
+            case token_type::literal_or_value:
+            default:
+                // a missing ':'; the value begins here
+                return next_step::parse_value;
+        }
+    }
+
+    /// recover from a token after an object member that is neither ',' nor
+    /// '}' (nor ']' or the end of the input, which the caller handles)
+    template<typename SAX>
+    next_step recover_member(SAX* sax, std::true_type /*allow_recovery*/)
+    {
+        if (last_token == token_type::parse_error)
+        {
+            recover_token();
+        }
+        if (last_token == token_type::value_string)
+        {
+            // a missing ','; the next key begins here
+            return parse_key(sax);
+        }
+        skip_member();
+        return next_step::evaluate_state;
+    }
+
+    /// the parser for parse() and accept() never recovers (and does not come
+    /// here, as report_error() returned false)
+    template<typename SAX>
+    std::false_type recover_member(SAX* /*sax*/, std::false_type /*allow_recovery*/) const noexcept
+    {
+        return {};
+    }
+
     /// get next token from lexer
     token_type get_token()
     {
@@ -531,6 +1166,12 @@ class parser
     const bool allow_exceptions = true;
     /// whether trailing commas in objects and arrays should be ignored (true) or signaled as errors (false)
     const bool ignore_trailing_commas = false;
+    /// whether an error was reported to the SAX parser
+    bool error_reported = false;
+    /// the position of the last reported error
+    std::size_t last_error_position = 0;
+    /// the token of the last reported error
+    token_type last_error_token = token_type::uninitialized;
 };
 
 }  // namespace detail

include/nlohmann/detail/input/string_scan.hpp

@@ -201,6 +201,43 @@ inline std::size_t validate_one_utf8(const unsigned char* data, std::size_t avai
     return 0; // invalid, incomplete, or must be diagnosed by the byte path
 }
 
+// Return the length of the longest prefix of [data, data+n) that consists of
+// ASCII characters and complete well-formed UTF-8 sequences; n if all of it is
+// valid UTF-8. Unlike scalar_string_bulk_run(), quotes, escapes, and control
+// characters are ordinary characters here. ASCII is skipped 8 bytes at a time.
+inline std::size_t valid_utf8_prefix(const unsigned char* data, std::size_t n) noexcept
+{
+    constexpr std::uint64_t high = 0x8080808080808080ull;
+    std::size_t pos = 0;
+    while (pos < n)
+    {
+        if (pos + 8 <= n)
+        {
+            std::uint64_t word = 0;
+            std::memcpy(&word, data + pos, sizeof(word));
+            if ((word & high) == 0)
+            {
+                pos += 8;
+                continue;
+            }
+        }
+
+        if (data[pos] < 0x80u)
+        {
+            ++pos;
+            continue;
+        }
+
+        const std::size_t seq = validate_one_utf8(data + pos, n - pos);
+        if (seq == 0)
+        {
+            break; // ill-formed or truncated
+        }
+        pos += seq;
+    }
+    return pos;
+}
+
 // Scalar (C++11) computation of the bulk run length: the number of leading
 // bytes in [data, data+n) that are ordinary ASCII or complete well-formed UTF-8
 // sequences, stopping before the first byte that needs individual handling (the

include/nlohmann/detail/macro_scope.hpp

@@ -596,16 +596,62 @@ void templated_json_throw(ExceptionType exception)
 
 #define NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(...) template<typename BasicJsonType, nlohmann::detail::enable_if_t<nlohmann::detail::is_basic_json<BasicJsonType>::value, int> = 0> __VA_ARGS__
 
+// Helpers used to dispatch the NLOHMANN_DEFINE_TYPE_*/NLOHMANN_DEFINE_DERIVED_TYPE_*
+// macros below between a zero-member and a one-or-more-member implementation
+// (issue #4041, e.g. NLOHMANN_DEFINE_TYPE_INTRUSIVE(Type) with no further
+// arguments). NLOHMANN_JSON_TYPE_BODY(Prefix, ...) expands to the macro name
+// Prefix##EMPTY when __VA_ARGS__ is a single argument (Type alone) and to
+// Prefix##MEMBERS for two or more (Type, member...). It reuses the existing
+// 64-slot NLOHMANN_JSON_GET_MACRO dispatch with one extra trailing sentinel
+// token appended so its own trailing "..." is never left completely empty at
+// the lowest supported argument count -- invoking a variadic macro so that
+// "..." matches nothing is only granted unconditionally by the standard since
+// C++20, and pre-C++20 compilers may reject it under -pedantic regardless of
+// what the macro body does.
+//
+// The EMPTY/MEMBERS suffixes are pasted onto Prefix right in the slot table:
+// operands of ## are not macro-expanded, so the dispatch keeps working even if
+// user code defines macros named EMPTY or MEMBERS. Producing the bare suffix
+// first and pasting it later would let such a macro replace it.
+//
+// NLOHMANN_JSON_DERIVED_TYPE_BODY(Prefix, ...) answers the same question for
+// the derived-type macros, whose fixed prefix is Type,BaseType. It drops the
+// leading Type and defers to NLOHMANN_JSON_TYPE_BODY rather than shifting the
+// slot table by one: NLOHMANN_JSON_GET_MACRO only resolves 64 positional
+// arguments, so dispatching on Type,BaseType,member... directly would run out
+// one slot early and cap the derived-type macros at 62 members instead of the
+// 63 that NLOHMANN_JSON_PASTE supports.
+#define NLOHMANN_JSON_TYPE_BODY(Prefix, ...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_GET_MACRO(__VA_ARGS__, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, \
+        Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## MEMBERS, Prefix ## EMPTY, \
+        NLOHMANN_JSON_TYPE_BODY_SENTINEL))
+
+#define NLOHMANN_JSON_DERIVED_TYPE_BODY_(Prefix, Type, ...) NLOHMANN_JSON_TYPE_BODY(Prefix, __VA_ARGS__)
+#define NLOHMANN_JSON_DERIVED_TYPE_BODY(Prefix, ...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY_(Prefix, __VA_ARGS__))
+
 /*!
 @brief macro
 @def NLOHMANN_DEFINE_TYPE_INTRUSIVE
 @since version 3.9.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/
 */
-#define NLOHMANN_DEFINE_TYPE_INTRUSIVE(Type, ...)  \
+#define NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_MEMBERS(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_EMPTY(Type)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type&) { nlohmann_json_j = BasicJsonType::object(); }) \
+    /* NOLINTNEXTLINE(bugprone-macro-parentheses) Type is used as a declarator type, not in an expression */ \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType&, Type&) noexcept { })
+
+#define NLOHMANN_DEFINE_TYPE_INTRUSIVE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_TYPE_BODY(NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_NAME, __VA_ARGS__)) })
@@ -616,10 +662,15 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.11.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/
 */
-#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Type, ...)  \
+#define NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_MEMBERS(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) })
 
+// identical to NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_EMPTY: with no members there is nothing to default
+#define NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_EMPTY(Type) NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_EMPTY(Type)
+
+#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_TYPE_BODY(NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT_WITH_NAME, __VA_ARGS__)) })
@@ -630,9 +681,14 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.11.3
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/
 */
-#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE(Type, ...)  \
+#define NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_MEMBERS(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_EMPTY(Type)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type&) { nlohmann_json_j = BasicJsonType::object(); })
+
+#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_TYPE_BODY(NLOHMANN_JSON_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) })
 
@@ -642,10 +698,17 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.9.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/
 */
-#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Type, ...)  \
+#define NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_MEMBERS(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_EMPTY(Type)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type&) { nlohmann_json_j = BasicJsonType::object(); }) \
+    /* NOLINTNEXTLINE(bugprone-macro-parentheses) Type is used as a declarator type, not in an expression */ \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType&, Type&) noexcept { })
+
+#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_TYPE_BODY(NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_NAME, __VA_ARGS__)) })
@@ -656,10 +719,15 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.11.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/
 */
-#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, ...)  \
+#define NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_MEMBERS(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) })
 
+// identical to NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_EMPTY: with no members there is nothing to default
+#define NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_EMPTY(Type) NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_EMPTY(Type)
+
+#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_TYPE_BODY(NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT_WITH_NAME, __VA_ARGS__)) })
@@ -670,9 +738,14 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.11.3
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/
 */
-#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE(Type, ...)  \
+#define NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_MEMBERS(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_EMPTY(Type)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type&) { nlohmann_json_j = BasicJsonType::object(); })
+
+#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_TYPE_BODY(NLOHMANN_JSON_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES(Type, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) })
 
@@ -682,10 +755,17 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.12.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/
 */
-#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE(Type, BaseType, ...)  \
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_MEMBERS(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_EMPTY(Type, BaseType)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); }) \
+    /* NOLINTNEXTLINE(bugprone-macro-parentheses) Type/BaseType are used as declarator types, not in expressions */ \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); })
+
+#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY(NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_NAME, __VA_ARGS__)) })
@@ -696,10 +776,15 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.12.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/
 */
-#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT(Type, BaseType, ...)  \
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_MEMBERS(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType&>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) })
 
+// identical to NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_EMPTY: with no members there is nothing to default
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_EMPTY(Type, BaseType) NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_EMPTY(Type, BaseType)
+
+#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY(NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType&>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT_WITH_NAME, __VA_ARGS__)) })
@@ -710,9 +795,14 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.12.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/
 */
-#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE(Type, BaseType, ...)  \
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_MEMBERS(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_EMPTY(Type, BaseType)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); })
+
+#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY(NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(friend void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) })
 
@@ -723,10 +813,17 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.12.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/
 */
-#define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE(Type, BaseType, ...)  \
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_MEMBERS(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_EMPTY(Type, BaseType)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); }) \
+    /* NOLINTNEXTLINE(bugprone-macro-parentheses) Type/BaseType are used as declarator types, not in expressions */ \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); })
+
+#define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY(NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_NAME, __VA_ARGS__)) })
@@ -737,10 +834,15 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.12.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/
 */
-#define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT(Type, BaseType, ...)  \
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_MEMBERS(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT, __VA_ARGS__)) })
 
+// identical to NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_EMPTY: with no members there is nothing to default
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_EMPTY(Type, BaseType) NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_EMPTY(Type, BaseType)
+
+#define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY(NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) }) \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void from_json(const BasicJsonType& nlohmann_json_j, Type& nlohmann_json_t) { nlohmann::from_json(nlohmann_json_j, static_cast<BaseType&>(nlohmann_json_t)); const Type nlohmann_json_default_obj{}; NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_FROM_WITH_DEFAULT_WITH_NAME, __VA_ARGS__)) })
@@ -751,9 +853,14 @@ void templated_json_throw(ExceptionType exception)
 @since version 3.12.0
 @sa https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/
 */
-#define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE(Type, BaseType, ...)  \
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_MEMBERS(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_PASTE(NLOHMANN_JSON_TO, __VA_ARGS__)) })
 
+#define NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_EMPTY(Type, BaseType)  \
+    NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); })
+
+#define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DERIVED_TYPE_BODY(NLOHMANN_JSON_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_, __VA_ARGS__)(__VA_ARGS__))
+
 #define NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES(Type, BaseType, ...)  \
     NLOHMANN_JSON_BASIC_TYPE_TEMPLATE(void to_json(BasicJsonType& nlohmann_json_j, const Type& nlohmann_json_t) { nlohmann::to_json(nlohmann_json_j, static_cast<const BaseType &>(nlohmann_json_t)); NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_DOUBLE_PASTE(NLOHMANN_JSON_TO_WITH_NAME, __VA_ARGS__)) })
 
@@ -812,7 +919,3 @@ void templated_json_throw(ExceptionType exception)
 #ifndef JSON_USE_GLOBAL_UDLS
     #define JSON_USE_GLOBAL_UDLS 1
 #endif
-
-#ifndef JSON_STRICT_NUL_HANDLING
-    #define JSON_STRICT_NUL_HANDLING 0
-#endif

include/nlohmann/detail/macro_unscope.hpp

@@ -26,7 +26,6 @@
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_USE_GLOBAL_UDLS
-#undef JSON_STRICT_NUL_HANDLING
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH
@@ -45,6 +44,8 @@
     #undef JSON_HAS_STATIC_RTTI
     #undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
     #undef JSON_BRACE_INIT_COPY_SEMANTICS
+    #undef JSON_PRECISE_STREAM_POSITION
+    #undef JSON_STRICT_NUL_HANDLING
 #endif
 
 #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

include/nlohmann/detail/output/serializer.hpp

@@ -32,6 +32,7 @@
 #include <nlohmann/detail/output/output_adapters.hpp>
 #include <nlohmann/detail/recursion_depth_limit.hpp>
 #include <nlohmann/detail/string_concat.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -58,8 +59,6 @@ class serializer
     using number_integer_t = typename BasicJsonType::number_integer_t;
     using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
     using binary_char_t = typename BasicJsonType::binary_t::value_type;
-    static constexpr std::uint8_t UTF8_ACCEPT = 0;
-    static constexpr std::uint8_t UTF8_REJECT = 1;
 
   public:
     /*!
@@ -1592,62 +1591,6 @@ class serializer
         }
     }
 
-    /*!
-    @brief check whether a string is UTF-8 encoded
-
-    The function checks each byte of a string whether it is UTF-8 encoded. The
-    result of the check is stored in the @a state parameter. The function must
-    be called initially with state 0 (accept). State 1 means the string must
-    be rejected, because the current byte is not allowed. If the string is
-    completely processed, but the state is non-zero, the string ended
-    prematurely; that is, the last byte indicated more bytes should have
-    followed.
-
-    @param[in,out] state  the state of the decoding
-    @param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
-    @param[in] byte       next byte to decode
-    @return               new state
-
-    @note The function has been edited: a std::array is used.
-
-    @copyright Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
-    @sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
-    */
-    static std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept
-    {
-        static const std::array<std::uint8_t, 400> utf8d =
-        {
-            {
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F
-                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F
-                7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF
-                8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF
-                0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF
-                0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF
-                0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
-                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
-                1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
-                1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
-                1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8
-            }
-        };
-
-        JSON_ASSERT(static_cast<std::size_t>(byte) < utf8d.size());
-        const std::uint8_t type = utf8d[byte];
-
-        codep = (state != UTF8_ACCEPT)
-                ? (byte & 0x3fu) | (codep << 6u)
-                : (0xFFu >> type) & (byte);
-
-        const std::size_t index = 256u + (static_cast<size_t>(state) * 16u) + static_cast<size_t>(type);
-        JSON_ASSERT(index < utf8d.size());
-        state = utf8d[index];
-        return state;
-    }
-
     /*
      * Overload to make the compiler happy while it is instantiating
      * dump_integer for number_unsigned_t.

include/nlohmann/detail/string_utils.hpp

@@ -8,10 +8,14 @@
 
 #pragma once
 
+#include <array> // array
 #include <cstddef> // size_t
+#include <cstdint> // uint8_t, uint32_t
 #include <string> // string, to_string
+#include <utility> // move
 
 #include <nlohmann/detail/abi_macros.hpp>
+#include <nlohmann/detail/macro_scope.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -33,5 +37,175 @@ StringType to_string(std::size_t value)
     return result;
 }
 
+///////////////////
+// UTF-8 decoding //
+///////////////////
+
+// UTF-8 decoder states used by decode() below
+static constexpr std::uint8_t UTF8_ACCEPT = 0;
+static constexpr std::uint8_t UTF8_REJECT = 1;
+
+/*!
+@brief process a byte of a UTF-8 sequence
+
+This is a single-byte step of a "shift-based" UTF-8 decoder originally
+written by Björn Hoehrmann. See
+http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
+
+This decoder is the single source of truth for UTF-8 validation in this
+library: it is used both by the serializer (to escape and, in strict mode,
+reject ill-formed UTF-8 when dumping a string) and by the binary readers
+(to reject ill-formed UTF-8 in CBOR/MessagePack/BSON/UBJSON text strings at
+decode time; see @ref is_valid_utf8 below).
+
+@param[in,out] state  the current decoder state
+@param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
+@param[in] byte       next byte to decode
+@return               new state
+
+@note Original source: http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
+@sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
+*/
+inline std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept
+{
+    static const std::array<std::uint8_t, 400> utf8d =
+    {
+        {
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F
+            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF
+            8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF
+            0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF
+            0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF
+            0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
+            1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
+            1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
+            1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8
+        }
+    };
+
+    JSON_ASSERT(static_cast<std::size_t>(byte) < utf8d.size());
+    const std::uint8_t type = utf8d[byte];
+
+    codep = (state != UTF8_ACCEPT)
+            ? (byte & 0x3fu) | (codep << 6u)
+            : (0xFFu >> type) & (byte);
+
+    const std::size_t index = 256u + (static_cast<std::size_t>(state) * 16u) + static_cast<std::size_t>(type);
+    JSON_ASSERT(index < utf8d.size());
+    state = utf8d[index];
+    return state;
+}
+
+/*!
+@brief check whether a string consists solely of valid UTF-8
+
+Used by the CBOR/MessagePack/BSON/UBJSON binary readers to reject text
+strings that are not valid UTF-8 at decode time (RFC 8949 §3.1 and the
+MessagePack/BSON specifications all require text strings to be UTF-8), so
+that malformed input is caught immediately instead of only surfacing later
+as a type_error.316 when the resulting value is dumped.
+
+@param[in] s      the string to check
+@param[in] first  index of the first byte to check; the bytes before it are
+                  assumed to have been validated already and to end on a
+                  code point boundary
+@return whether @a s (from index @a first on) is valid UTF-8
+*/
+template<typename StringType>
+inline bool is_valid_utf8(const StringType& s, const std::size_t first = 0) noexcept
+{
+    std::uint8_t state = UTF8_ACCEPT;
+    std::uint32_t codepoint = 0;
+
+    for (std::size_t i = first; i < s.size(); ++i)
+    {
+        decode(state, codepoint, static_cast<std::uint8_t>(s[i]));
+        if (state == UTF8_REJECT)
+        {
+            return false;
+        }
+    }
+
+    return state == UTF8_ACCEPT;
+}
+
+/*!
+@brief append U+FFFD REPLACEMENT CHARACTER, encoded in UTF-8
+@param[in,out] s  the string to append to
+*/
+template<typename StringType>
+inline void append_replacement_character(StringType& s)
+{
+    s.push_back(static_cast<typename StringType::value_type>(0xEFu));
+    s.push_back(static_cast<typename StringType::value_type>(0xBFu));
+    s.push_back(static_cast<typename StringType::value_type>(0xBDu));
+}
+
+/*!
+@brief replace ill-formed UTF-8 with U+FFFD REPLACEMENT CHARACTER
+
+Each maximal subpart of an ill-formed sequence becomes one U+FFFD, as the
+Unicode Standard recommends (Section 3.9, "U+FFFD Substitution of Maximal
+Subparts"), and as the parser for JSON text does when it recovers from errors.
+
+@param[in,out] s  the string to repair
+@param[in] first  index of the first byte to repair; the bytes before it are
+                  assumed to be valid UTF-8 that ends on a code point boundary
+*/
+template<typename StringType>
+inline void replace_invalid_utf8(StringType& s, const std::size_t first = 0)
+{
+    StringType result = s;
+    result.resize(first);
+
+    std::uint8_t state = UTF8_ACCEPT;
+    std::uint32_t codepoint = 0;
+    // the first byte of the sequence being decoded
+    std::size_t sequence_start = first;
+
+    std::size_t i = first;
+    while (i < s.size())
+    {
+        switch (decode(state, codepoint, static_cast<std::uint8_t>(s[i])))
+        {
+            case UTF8_ACCEPT:
+                for (++i; sequence_start < i; ++sequence_start)
+                {
+                    result.push_back(s[sequence_start]);
+                }
+                break;
+
+            case UTF8_REJECT:
+                append_replacement_character(result);
+                // the byte that made the sequence ill-formed begins the next
+                // one, unless it began this one
+                if (i == sequence_start)
+                {
+                    ++i;
+                }
+                state = UTF8_ACCEPT;
+                sequence_start = i;
+                break;
+
+            default: // in the middle of a sequence
+                ++i;
+                break;
+        }
+    }
+
+    // a sequence that the string ends in the middle of
+    if (state != UTF8_ACCEPT)
+    {
+        append_replacement_character(result);
+    }
+
+    s = std::move(result);
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/json.hpp

@@ -143,7 +143,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     friend class ::nlohmann::detail::iter_impl;
     template<typename BasicJsonType, typename CharType, typename OutputSinkType>
     friend class ::nlohmann::detail::binary_writer;
-    template<typename BasicJsonType, typename InputType, typename SAX>
+    template<typename BasicJsonType, typename InputType, typename SAX, bool AllowRecovery>
     friend class ::nlohmann::detail::binary_reader;
     template<typename BasicJsonType, typename InputAdapterType>
     friend class ::nlohmann::detail::json_sax_dom_parser;
@@ -924,6 +924,31 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     }
 #endif
 
+    /*!
+    @brief whether a descent must stop here and finish without the call stack
+
+    @a may_descend says whether the operator descends at all; it is a constant
+    at every call site, and is passed rather than tested by the caller so that
+    the test does not become a constant condition there, which MSVC reports as
+    C4127.
+
+    The comparison operators use this rather than @ref nesting_depth_guard::okay,
+    because they are written as a macro and a macro cannot use the preprocessor
+    the way the guard's constructor does; @ref copy_structured, which can, asks
+    the guard instead and never calls this.
+    */
+    static bool nesting_depth_exhausted(bool may_descend = true) noexcept
+    {
+#ifdef JSON_NO_THREAD_LOCAL
+        // without a count of its own per thread, a descent cannot be bounded
+        // without racing another one, so none is made
+        static_cast<void>(may_descend);
+        return true;
+#else
+        return !may_descend || nesting_depth() >= nesting_depth_limit();
+#endif
+    }
+
     /*!
     @brief counts one level of a bounded descent for as long as it runs, and
            reports whether the descent was still within the limit when it began
@@ -978,7 +1003,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     using copy_worklist_t = std::vector<std::pair<const basic_json*, basic_json*>>;
 
     /// scratch space to build the key skeleton of an object copy in one go
-    using copy_scratch_t = std::vector<std::pair<typename object_t::key_type, basic_json>>;
+    using copy_scratch_value_t = std::pair<typename object_t::key_type, basic_json>;
+    using copy_scratch_t = std::vector<copy_scratch_value_t, AllocatorType<copy_scratch_value_t>>;
 
     /// @brief copy everything of @a src into @a dst but its type and value
     static void copy_metadata(const basic_json& src, basic_json& dst)
@@ -1243,6 +1269,289 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     }
 
 
+    /// the result of comparing two values, including values that cannot be
+    /// ordered at all, such as a discarded value or a NaN
+    enum class compare_result { less, equal, greater, unordered };
+
+#if JSON_HAS_THREE_WAY_COMPARISON
+    /// @brief the ordering that @a result stands for
+    static std::partial_ordering to_partial_ordering(compare_result result) noexcept // *NOPAD*
+    {
+        switch (result)
+        {
+            case compare_result::less:
+                return std::partial_ordering::less;
+            case compare_result::greater:
+                return std::partial_ordering::greater;
+            case compare_result::equal:
+                return std::partial_ordering::equivalent;
+            case compare_result::unordered:
+            default:
+                return std::partial_ordering::unordered;
+        }
+    }
+#endif
+
+    /*!
+    @brief compare two values that are not both an array or both an object
+
+    Such a pair is compared by the operators themselves, which cannot descend
+    into it and therefore cannot recurse.
+
+    That holds for a pair whose types differ as much as for a pair of leaves: an
+    array and an object are told apart by their types alone, because an operator
+    only ever descends into two values of the same type. So `==` reports them as
+    unequal without looking inside either, and an ordering falls back to the
+    order of the types - an object sorts before an array - exactly as it does
+    for a value that is not nested deeply enough to get here.
+    */
+    template<bool Ordered>
+    static compare_result compare_leaves(const_reference lhs, const_reference rhs) noexcept
+    {
+        if (lhs == rhs)
+        {
+            return compare_result::equal;
+        }
+
+        return order_leaves(lhs, rhs, std::integral_constant<bool, Ordered> {});
+    }
+
+    /*!
+    @brief compare two object keys
+
+    An object compares its entries as pairs of a key and a value, so its keys
+    are compared exactly as std::pair compares them: with < where the objects
+    are being ordered, and with == where they are only checked for equality.
+    Note that this is not the object's own comparator, which for a vector-backed
+    object type such as nlohmann::ordered_map tells equality rather than order.
+    */
+    static compare_result compare_keys(const typename object_t::key_type& lhs,
+                                       const typename object_t::key_type& rhs,
+                                       std::true_type /*ordered*/)
+    {
+        if (lhs < rhs)
+        {
+            return compare_result::less;
+        }
+
+        if (rhs < lhs)
+        {
+            return compare_result::greater;
+        }
+
+        return compare_result::equal;
+    }
+
+    /// @brief check two object keys for equality
+    static compare_result compare_keys(const typename object_t::key_type& lhs,
+                                       const typename object_t::key_type& rhs,
+                                       std::false_type /*ordered*/)
+    {
+        return lhs == rhs ? compare_result::equal : compare_result::unordered;
+    }
+
+    /// @brief tell apart two values that are not equal
+    /// @note only instantiated where the values are being ordered, as a key or
+    ///       string type is not required to be ordered to be compared for equality
+    static compare_result order_leaves(const_reference lhs, const_reference rhs, std::true_type /*ordered*/) noexcept
+    {
+        if (lhs < rhs)
+        {
+            return compare_result::less;
+        }
+
+        if (rhs < lhs)
+        {
+            return compare_result::greater;
+        }
+
+        return compare_result::unordered;
+    }
+
+    /// @brief report two values as not equal without ordering them
+    static compare_result order_leaves(const_reference /*lhs*/, const_reference /*rhs*/, std::false_type /*ordered*/) noexcept
+    {
+        return compare_result::unordered;
+    }
+
+    /*!
+    @brief compare @a lhs and @a rhs without descending into them
+
+    Reached once a comparison has descended @ref nesting_depth_limit levels, so
+    that comparing values cannot exhaust the call stack however deeply they are
+    nested. The two values are walked in lockstep on an explicit stack and
+    compared lexicographically, element by element in the order the containers
+    enumerate them - which is how the container types this library ships compare
+    themselves: a std::map enumerates its entries in key order, and
+    nlohmann::ordered_map in insertion order. An object type that enumerates its
+    entries in an unspecified order, such as std::unordered_map, compares them
+    pairwise instead; the difference could only ever show below the bound.
+
+    Note that the stack this walks with is allocated, while the comparison
+    operators are noexcept and the container comparison this replaces allocated
+    nothing. Failing that allocation therefore ends the process rather than
+    throwing. It only arises for values nested past the bound, and only when
+    memory has run out - where the same comparison used to exhaust the call
+    stack instead - but it is a way to fail that the operators did not have.
+    */
+    template<bool Ordered>
+    static compare_result compare_iteratively(const_reference lhs, const_reference rhs,
+            const bool unordered_compares_equal) noexcept
+    {
+        /// a pair of containers being compared in lockstep
+        struct frame
+        {
+            const basic_json* lhs_value{nullptr};
+            const basic_json* rhs_value{nullptr};
+            typename array_t::const_iterator lhs_array_it{};
+            typename array_t::const_iterator rhs_array_it{};
+            typename object_t::const_iterator lhs_object_it{};
+            typename object_t::const_iterator rhs_object_it{};
+        };
+
+        std::vector<frame> stack;
+        const basic_json* left = &lhs;
+        const basic_json* right = &rhs;
+
+        for (;;)
+        {
+            const auto type = left->m_data.m_type;
+
+            if (type == right->m_data.m_type && (type == value_t::array || type == value_t::object))
+            {
+                // descend: the elements decide, and are compared further down
+                stack.emplace_back();
+                frame& pushed = stack.back();
+                pushed.lhs_value = left;
+                pushed.rhs_value = right;
+
+                if (type == value_t::array)
+                {
+                    pushed.lhs_array_it = left->m_data.m_value.array->cbegin();
+                    pushed.rhs_array_it = right->m_data.m_value.array->cbegin();
+                }
+                else
+                {
+                    pushed.lhs_object_it = left->m_data.m_value.object->cbegin();
+                    pushed.rhs_object_it = right->m_data.m_value.object->cbegin();
+                }
+            }
+            else
+            {
+                const compare_result result = compare_leaves<Ordered>(*left, *right);
+
+                // Values that cannot be ordered - a NaN, say - end an ordered
+                // comparison for std::lexicographical_compare_three_way, but
+                // std::lexicographical_compare treats them as equivalent and
+                // carries on with the next element. Both are reproduced here,
+                // so that a value nested too deeply to descend into compares
+                // exactly as one that is not.
+                if (result != compare_result::equal &&
+                        !(unordered_compares_equal && result == compare_result::unordered))
+                {
+                    return result;
+                }
+            }
+
+            // walk back up past the containers that are exhausted, then take the
+            // next pair of elements from the innermost one that is not
+            for (;;)
+            {
+                if (stack.empty())
+                {
+                    return compare_result::equal;
+                }
+
+                frame& current = stack.back();
+                const bool is_object = current.lhs_value->m_data.m_type == value_t::object;
+
+                const bool lhs_done = is_object
+                                      ? current.lhs_object_it == current.lhs_value->m_data.m_value.object->cend()
+                                      : current.lhs_array_it == current.lhs_value->m_data.m_value.array->cend();
+                const bool rhs_done = is_object
+                                      ? current.rhs_object_it == current.rhs_value->m_data.m_value.object->cend()
+                                      : current.rhs_array_it == current.rhs_value->m_data.m_value.array->cend();
+
+                if (lhs_done || rhs_done)
+                {
+                    // whichever ran out first holds the smaller container; if
+                    // both did, they are equal and the container above decides
+                    if (lhs_done != rhs_done)
+                    {
+                        return lhs_done ? compare_result::less : compare_result::greater;
+                    }
+
+                    stack.pop_back();
+                    continue;
+                }
+
+                if (is_object)
+                {
+                    // an entry is a key and a value, and the key decides first
+                    const compare_result key_result =
+                        compare_keys(current.lhs_object_it->first, current.rhs_object_it->first,
+                                     std::integral_constant<bool, Ordered> {});
+
+                    left = &(current.lhs_object_it->second);
+                    right = &(current.rhs_object_it->second);
+
+                    if (key_result != compare_result::equal)
+                    {
+                        // An object type without a fixed order of its entries -
+                        // std::unordered_map, say - may enumerate two equal
+                        // objects differently, and its operator== does not care.
+                        // Equality then finds the entry by its key; an ordering,
+                        // or an object type that compares its entries in
+                        // sequence (ordered_map), is decided by the key itself.
+                        const auto* rhs_object = current.rhs_value->m_data.m_value.object;
+                        const auto found = (!Ordered && !detail::is_ordered_map<object_t>::value)
+                                           ? rhs_object->find(current.lhs_object_it->first)
+                                           : rhs_object->cend();
+                        if (found == rhs_object->cend())
+                        {
+                            return key_result;
+                        }
+                        right = &(found->second);
+                    }
+
+                    ++current.lhs_object_it;
+                    ++current.rhs_object_it;
+                }
+                else
+                {
+                    left = &(*current.lhs_array_it);
+                    right = &(*current.rhs_array_it);
+                    ++current.lhs_array_it;
+                    ++current.rhs_array_it;
+                }
+
+                break;
+            }
+        }
+    }
+
+
+    /// @brief restore the parent pointers after erasing from an object
+    /// ordered_json keeps its members in a vector, and erasing a member
+    /// re-constructs every member after it in place, which resets their
+    /// parent pointers
+    void set_parents_after_object_erase()
+    {
+#if JSON_DIAGNOSTICS
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning(push )
+#pragma warning(disable : 4127) // ignore warning to replace if with if constexpr
+#endif
+        if (detail::is_ordered_map<object_t>::value)
+        {
+            set_parents();
+        }
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning( pop )
+#endif
+#endif
+    }
+
   public:
     //////////////////////////
     // JSON parser callback //
@@ -1863,17 +2172,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     // value access //
     //////////////////
 
-    /// get a boolean (explicit)
-    boolean_t get_impl(boolean_t* /*unused*/) const
-    {
-        if (JSON_HEDLEY_LIKELY(is_boolean()))
-        {
-            return m_data.m_value.boolean;
-        }
-
-        JSON_THROW(type_error::create(302, detail::concat("type must be boolean, but is ", type_name()), this));
-    }
-
     /// get a pointer to the value (object)
     object_t* get_impl_ptr(object_t* /*unused*/) noexcept
     {
@@ -2260,6 +2558,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     ValueType & get_to(ValueType& v) const noexcept(noexcept(
                 JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>(), v)))
     {
+        static_assert(!std::is_const<ValueType>::value, "get_to() cannot deserialize into a const value");
         JSONSerializer<ValueType>::from_json(*this, v);
         return v;
     }
@@ -2285,6 +2584,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     noexcept(noexcept(JSONSerializer<Array>::from_json(
                           std::declval<const basic_json_t&>(), v)))
     {
+        static_assert(!std::is_const<T>::value, "get_to() cannot deserialize into a const value");
         JSONSerializer<Array>::from_json(*this, v);
         return v;
     }
@@ -2931,6 +3231,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             case value_t::object:
             {
                 result.m_it.object_iterator = erase_from_object(pos.m_it.object_iterator);
+                set_parents_after_object_erase();
                 break;
             }
 
@@ -3003,6 +3304,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             {
                 result.m_it.object_iterator = m_data.m_value.object->erase(first.m_it.object_iterator,
                                               last.m_it.object_iterator);
+                set_parents_after_object_erase();
                 break;
             }
 
@@ -3033,7 +3335,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
 
-        return m_data.m_value.object->erase(std::forward<KeyType>(key));
+        const auto erased = m_data.m_value.object->erase(std::forward<KeyType>(key));
+        set_parents_after_object_erase();
+        return erased;
     }
 
     template < typename KeyType, detail::enable_if_t <
@@ -3050,6 +3354,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         if (it != m_data.m_value.object->end())
         {
             m_data.m_value.object->erase(it);
+            set_parents_after_object_erase();
             return 1;
         }
         return 0;
@@ -3961,16 +4266,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 if (it2 != m_data.m_value.object->end() && it2->second.is_object())
                 {
                     it2->second.update_members(it.value().cbegin(), it.value().cend(), true, depth + 1);
-#if JSON_DIAGNOSTICS
-                    it2->second.set_parents();
-#endif
                     continue;
                 }
             }
-            m_data.m_value.object->operator[](it.key()) = it.value();
+            // set_parent() also repairs the other members, which ordered_json
-#if JSON_DIAGNOSTICS
+            // relocates when adding a key makes its vector grow
-            m_data.m_value.object->operator[](it.key()).m_parent = this;
+            set_parent(m_data.m_value.object->operator[](it.key()) = it.value());
-#endif
         }
     }
 
@@ -3999,9 +4300,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 }
 
                 // a nested object is merged: continue with its parent
-#if JSON_DIAGNOSTICS
-                target->set_parents();
-#endif
                 target = stack.back().target;
                 first = stack.back().position;
                 last = stack.back().last;
@@ -4023,10 +4321,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     continue;
                 }
             }
-            target->m_data.m_value.object->operator[](first.key()) = first.value();
+            // set_parent() also repairs the other members, which ordered_json
-#if JSON_DIAGNOSTICS
+            // relocates when adding a key makes its vector grow
-            target->m_data.m_value.object->operator[](first.key()).m_parent = target;
+            target->set_parent(target->m_data.m_value.object->operator[](first.key()) = first.value());
-#endif
             ++first;
         }
     }
@@ -4165,7 +4462,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     // because any negative signed value is smaller than any unsigned value.
     // Otherwise, the non-negative signed value is cast to unsigned before the
     // comparison to avoid wraparound.
-#define JSON_IMPLEMENT_OPERATOR(op, null_result, unordered_result, default_result)                       \
+#define JSON_IMPLEMENT_OPERATOR(op, null_result, unordered_result, default_result, deep_result, may_descend) \
     const auto lhs_type = lhs.type();                                                                    \
     const auto rhs_type = rhs.type();                                                                    \
     \
@@ -4174,11 +4471,25 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         switch (lhs_type)                                                                                \
         {                                                                                                \
             case value_t::array:                                                                         \
+            {                                                                                            \
+                if (JSON_HEDLEY_UNLIKELY(nesting_depth_exhausted(may_descend)))                        \
+                {                                                                                        \
+                    return (deep_result);                                                                \
+                }                                                                                        \
+                const nesting_depth_guard guard;                                                         \
                 return (*lhs.m_data.m_value.array) op (*rhs.m_data.m_value.array);                                     \
-                \
+            }                                                                                            \
+            \
             case value_t::object:                                                                        \
+            {                                                                                            \
+                if (JSON_HEDLEY_UNLIKELY(nesting_depth_exhausted(may_descend)))                        \
+                {                                                                                        \
+                    return (deep_result);                                                                \
+                }                                                                                        \
+                const nesting_depth_guard guard;                                                         \
                 return (*lhs.m_data.m_value.object) op (*rhs.m_data.m_value.object);                                   \
-                \
+            }                                                                                            \
+            \
             case value_t::null:                                                                          \
                 return (null_result);                                                                    \
                 \
@@ -4278,7 +4589,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         JSON_HEDLEY_PRAGMA(GCC diagnostic ignored "-Wfloat-equal")
 #endif
         const_reference lhs = *this;
-        JSON_IMPLEMENT_OPERATOR( ==, true, false, false)
+        JSON_IMPLEMENT_OPERATOR( ==, true, false, false,
+                                 compare_iteratively<false>(lhs, rhs, false) == compare_result::equal, true)
 #ifdef __GNUC__
         JSON_HEDLEY_DIAGNOSTIC_POP
 #endif
@@ -4303,7 +4615,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         JSON_IMPLEMENT_OPERATOR(<=>, // *NOPAD*
                                 std::partial_ordering::equivalent,
                                 std::partial_ordering::unordered,
-                                lhs_type <=> rhs_type) // *NOPAD*
+                                lhs_type <=> rhs_type, // *NOPAD*
+                                to_partial_ordering(compare_iteratively<true>(lhs, rhs, false)), true)
     }
 
     /// @brief comparison: 3-way
@@ -4370,7 +4683,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         JSON_HEDLEY_DIAGNOSTIC_PUSH
         JSON_HEDLEY_PRAGMA(GCC diagnostic ignored "-Wfloat-equal")
 #endif
-        JSON_IMPLEMENT_OPERATOR( ==, true, false, false)
+        JSON_IMPLEMENT_OPERATOR( ==, true, false, false,
+                                 compare_iteratively<false>(lhs, rhs, false) == compare_result::equal, true)
 #ifdef __GNUC__
         JSON_HEDLEY_DIAGNOSTIC_POP
 #endif
@@ -4426,7 +4740,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         // default_result is used if we cannot compare values. In that case,
         // we compare types. Note we have to call the operator explicitly,
         // because MSVC has problems otherwise.
-        JSON_IMPLEMENT_OPERATOR( <, false, false, operator<(lhs_type, rhs_type))
+        JSON_IMPLEMENT_OPERATOR( <, false, false, operator<(lhs_type, rhs_type),
+                                 compare_iteratively<true>(lhs, rhs, true) == compare_result::less, false)
     }
 
     /// @brief comparison: less than
@@ -4677,7 +4992,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = detail::input_adapter(std::forward<InputType>(i));
         return format == input_format_t::json
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(format, sax, strict);
     }
 
     /// @brief generate SAX events (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -4694,7 +5009,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = detail::input_adapter(std::move(first), std::move(last));
         return format == input_format_t::json
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(format, sax, strict);
     }
 
     /// @brief generate SAX events
@@ -4716,7 +5031,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
                ? parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict)
                // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(format, sax, strict);
     }
 #ifndef JSON_NO_IO
     /// @brief deserialize from stream
@@ -4975,6 +5290,30 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         binary_writer<char>(o).write_bson(j);
     }
 
+    /// @brief create a BON8 serialization of a given JSON value
+    /// @sa https://json.nlohmann.me/api/basic_json/to_bon8/
+    static std::vector<std::uint8_t> to_bon8(const basic_json& j)
+    {
+        std::vector<std::uint8_t> result;
+        result.reserve(detail::binary_reserve_hint(j));
+        vector_writer(result).write_bon8(j);
+        return result;
+    }
+
+    /// @brief create a BON8 serialization of a given JSON value
+    /// @sa https://json.nlohmann.me/api/basic_json/to_bon8/
+    static void to_bon8(const basic_json& j, detail::output_adapter<std::uint8_t> o)
+    {
+        binary_writer<std::uint8_t>(o).write_bon8(j);
+    }
+
+    /// @brief create a BON8 serialization of a given JSON value
+    /// @sa https://json.nlohmann.me/api/basic_json/to_bon8/
+    static void to_bon8(const basic_json& j, detail::output_adapter<char> o)
+    {
+        binary_writer<char>(o).write_bon8(j);
+    }
+
     /// @brief create a JSON value from an input in CBOR format
     /// @sa https://json.nlohmann.me/api/basic_json/from_cbor/
     template<typename InputType>
@@ -5208,6 +5547,43 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
+    /// @brief create a JSON value from an input in BON8 format
+    /// @sa https://json.nlohmann.me/api/basic_json/from_bon8/
+    template<typename InputType>
+    JSON_HEDLEY_WARN_UNUSED_RESULT
+    static basic_json from_bon8(InputType&& i,
+                                const bool strict = true,
+                                const bool allow_exceptions = true)
+    {
+        basic_json result;
+        auto ia = detail::input_adapter(std::forward<InputType>(i));
+        detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(input_format_t::bon8, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        {
+            result = value_t::discarded;
+        }
+        return result;
+    }
+
+    /// @brief create a JSON value from an input in BON8 format (iterator pair, or iterator+sentinel pair for C++20 ranges support)
+    /// @sa https://json.nlohmann.me/api/basic_json/from_bon8/
+    template<typename IteratorType, typename SentinelType = IteratorType,
+             detail::enable_if_t<detail::can_compare_ne<IteratorType, SentinelType>::value, int> = 0>
+    JSON_HEDLEY_WARN_UNUSED_RESULT
+    static basic_json from_bon8(IteratorType first, SentinelType last,
+                                const bool strict = true,
+                                const bool allow_exceptions = true)
+    {
+        basic_json result;
+        auto ia = detail::input_adapter(std::move(first), std::move(last));
+        detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(input_format_t::bon8, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        {
+            result = value_t::discarded;
+        }
+        return result;
+    }
+
     /// @brief create a JSON value from an input in BSON format
     /// @sa https://json.nlohmann.me/api/basic_json/from_bson/
     template<typename InputType>

single_include/nlohmann/json_fwd.hpp

@@ -56,6 +56,14 @@
     #define JSON_BRACE_INIT_COPY_SEMANTICS 0
 #endif
 
+#ifndef JSON_PRECISE_STREAM_POSITION
+    #define JSON_PRECISE_STREAM_POSITION 0
+#endif
+
+#ifndef JSON_STRICT_NUL_HANDLING
+    #define JSON_STRICT_NUL_HANDLING 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -80,21 +88,35 @@
     #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
 #endif
 
+#if JSON_PRECISE_STREAM_POSITION
+    #define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION _psp
+#else
+    #define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION
+#endif
+
+#if JSON_STRICT_NUL_HANDLING
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING _snul
+#else
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING
+#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) json_abi ## a ## b ## c ## d
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f) json_abi ## a ## b ## c ## d ## e ## f
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
-            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
+            NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION,           \
+            NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

src/modules/json.cppm

@@ -46,6 +46,7 @@ inline namespace json_literals
 namespace detail
 {
     using NLOHMANN_JSON_NAMESPACE::detail::json_sax_dom_callback_parser;
+    using NLOHMANN_JSON_NAMESPACE::detail::json_sax_dom_parser;
     using NLOHMANN_JSON_NAMESPACE::detail::unknown_size;
 } // namespace detail
 

tests/CMakeLists.txt

@@ -80,7 +80,10 @@ target_compile_options(test_main PUBLIC
     #                              std::allocator_traits<...>::construct for the custom-base-class
     #                              test's map type past VS2015's limit. The name is only used for
     #                              debug info, so truncation does not affect the build.
-    $<$<CXX_COMPILER_ID:MSVC>:/W4;/wd4566;/wd4996;/wd4702;/wd4503>
+    #       Disable warning C5285: cannot declare a specialization for 'std::tuple'; MSVC 19.51
+    #                              reports the forward declarations of standard library
+    #                              templates in the vendored doctest.h
+    $<$<CXX_COMPILER_ID:MSVC>:/W4;/wd4566;/wd4996;/wd4702;/wd4503;/wd5285>
     # https://github.com/nlohmann/json/issues/1114
     $<$<CXX_COMPILER_ID:MSVC>:/bigobj> $<$<BOOL:${MINGW}>:-Wa,-mbig-obj>
 
@@ -109,7 +112,7 @@ endif()
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     # avoid stack overflow, see https://github.com/nlohmann/json/issues/2955
-    json_test_set_test_options("test-cbor;test-msgpack;test-ubjson;test-bjdata;test-binary_formats" LINK_OPTIONS /STACK:4000000)
+    json_test_set_test_options("test-bon8;test-cbor;test-msgpack;test-ubjson;test-bjdata;test-binary_formats" LINK_OPTIONS /STACK:4000000)
 endif()
 
 # disable exceptions for test-disabled_exceptions

tests/Makefile

@@ -10,7 +10,7 @@ CXXFLAGS += -std=c++11
 CPPFLAGS += -I ../single_include
 
 FUZZER_ENGINE = src/fuzzer-driver_afl.cpp
-FUZZERS = parse_afl_fuzzer parse_bson_fuzzer parse_cbor_fuzzer parse_msgpack_fuzzer parse_ubjson_fuzzer parse_bjdata_fuzzer
+FUZZERS = parse_afl_fuzzer parse_bson_fuzzer parse_cbor_fuzzer parse_msgpack_fuzzer parse_ubjson_fuzzer parse_bjdata_fuzzer parse_bon8_fuzzer
 fuzzers: $(FUZZERS)
 
 parse_afl_fuzzer:
@@ -30,3 +30,6 @@ parse_ubjson_fuzzer:
 
 parse_bjdata_fuzzer:
 	$(CXX) $(CXXFLAGS) $(CPPFLAGS) $(FUZZER_ENGINE) src/fuzzer-parse_bjdata.cpp -o $@
+
+parse_bon8_fuzzer:
+	$(CXX) $(CXXFLAGS) $(CPPFLAGS) $(FUZZER_ENGINE) src/fuzzer-parse_bon8.cpp -o $@

tests/abi/config/default.cpp

@@ -36,6 +36,14 @@ TEST_CASE("default namespace")
         expected += "_bics";
 #endif
 
+#if JSON_PRECISE_STREAM_POSITION
+        expected += "_psp";
+#endif
+
+#if JSON_STRICT_NUL_HANDLING
+        expected += "_snul";
+#endif
+
         expected += "_v" STRINGIZE(NLOHMANN_JSON_VERSION_MAJOR);
         expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_MINOR);
         expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_PATCH) "::basic_json";