Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45

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

# Conflicts:
#	include/nlohmann/detail/input/binary_reader.hpp
#	include/nlohmann/json.hpp
#	single_include/nlohmann/json.hpp

.github/workflows/check_amalgamation.yml

@@ -35,6 +35,7 @@ jobs:
       MAIN_DIR: ${{ github.workspace }}/main
       INCLUDE_DIR: ${{ github.workspace }}/main/single_include/nlohmann
       TOOL_DIR: ${{ github.workspace }}/tools/tools/amalgamate
+      NATVIS_TOOL_DIR: ${{ github.workspace }}/tools/tools/generate_natvis
 
     steps:
       - name: Harden Runner
@@ -61,6 +62,48 @@ jobs:
           python3 -mvenv venv
           venv/bin/pip3 install -r $MAIN_DIR/tools/astyle/requirements.txt
 
+      - name: Install generate_natvis dependencies
+        run: pip3 install -r $NATVIS_TOOL_DIR/requirements.txt
+
+      - name: Regenerate the tools/macro_builder tables in macro_scope.hpp
+        run: |
+          cd $MAIN_DIR
+
+          # Built from this PR's own tools/macro_builder/main.cpp, not a
+          # develop checkout: unlike amalgamate.py and generate_natvis.py,
+          # this tool has no other source of truth to check against (its
+          # own README documents that it must reproduce macro_scope.hpp
+          # byte for byte), so there is nothing to gain from checking out a
+          # separate copy, and doing so would make this step fail on a PR
+          # that adds support for a new dispatch table until that PR itself
+          # merges to develop, the same way generate_natvis.py's --version
+          # requirement briefly did.
+          TMPDIR=$(mktemp -d ./macro_builder_check.XXXXXX)
+          c++ -std=c++11 tools/macro_builder/main.cpp -o "$TMPDIR/macro_builder"
+          "$TMPDIR/macro_builder" > "$TMPDIR/paste.hpp"
+          "$TMPDIR/macro_builder" type_body > "$TMPDIR/type_body.hpp"
+
+          # Splice the (still unindented) generated blocks back into
+          # macro_scope.hpp; the astyle pass below indents their
+          # continuation lines the same way it does for the rest of
+          # include/, so a correctly regenerated file comes out unchanged.
+          awk -v newfile="$TMPDIR/paste.hpp" '
+            BEGIN { while ((getline line < newfile) > 0) { new = new line "\n" } }
+            /^#define NLOHMANN_JSON_EXPAND\( x \) x$/ { printf "%s", new; skip=1 }
+            skip && /^#define NLOHMANN_JSON_DOUBLE_PASTE63\(/ { skip=0; next }
+            skip { next }
+            { print }
+          ' include/nlohmann/detail/macro_scope.hpp > "$TMPDIR/macro_scope_1.hpp"
+          awk -v newfile="$TMPDIR/type_body.hpp" '
+            BEGIN { while ((getline line < newfile) > 0) { new = new line "\n" } }
+            /^#define NLOHMANN_JSON_TYPE_BODY\(Prefix, \.\.\.\)/ { printf "%s", new; skip=1 }
+            skip && /^[[:space:]]*NLOHMANN_JSON_TYPE_BODY_SENTINEL\)\)$/ { skip=0; next }
+            skip { next }
+            { print }
+          ' "$TMPDIR/macro_scope_1.hpp" > "$TMPDIR/macro_scope_2.hpp"
+          mv "$TMPDIR/macro_scope_2.hpp" include/nlohmann/detail/macro_scope.hpp
+          rm -rf "$TMPDIR"
+
       - name: Regenerate amalgamation, formatting, and BUILD.bazel
         run: |
           cd $MAIN_DIR
@@ -88,6 +131,19 @@ jobs:
           ${{ github.workspace }}/venv/bin/astyle --project=tools/astyle/.astylerc --suffix=none --quiet \
             $(find $SOURCE_DIRS -type f \( -name '*.hpp' -o -name '*.cpp' -o -name '*.cu' \) -not -path 'tests/thirdparty/*' -not -path 'tests/abi/include/nlohmann/*' | sort)
 
+      - name: Regenerate nlohmann_json.natvis
+        run: |
+          cd $MAIN_DIR
+          # Pass --version explicitly so this step also works with the tool
+          # copy from develop before this repository's own generate_natvis.py
+          # learns to derive the version itself: the older script requires
+          # --version, and the newer one accepts it as an explicit override.
+          ABI_MACROS=include/nlohmann/detail/abi_macros.hpp
+          VERSION_MAJOR=$(grep -m1 'define NLOHMANN_JSON_VERSION_MAJOR' $ABI_MACROS | grep -o '[0-9]\+')
+          VERSION_MINOR=$(grep -m1 'define NLOHMANN_JSON_VERSION_MINOR' $ABI_MACROS | grep -o '[0-9]\+')
+          VERSION_PATCH=$(grep -m1 'define NLOHMANN_JSON_VERSION_PATCH' $ABI_MACROS | grep -o '[0-9]\+')
+          python3 $NATVIS_TOOL_DIR/generate_natvis.py --version "$VERSION_MAJOR.$VERSION_MINOR.$VERSION_PATCH" $MAIN_DIR
+
       - name: Build patch and check for differences
         id: diff
         run: |

.github/workflows/publish_documentation.yml

@@ -7,6 +7,16 @@ on:
       - develop
     paths:
       - docs/mkdocs/**
+      # the site also embeds these files via pymdownx.snippets
+      # (mkdocs.yml sets restrict_base_path: false for this)
+      - .clang-tidy
+      - .github/CODE_OF_CONDUCT.md
+      - .github/CONTRIBUTING.md
+      - .github/SECURITY.md
+      - cmake/clang_flags.cmake
+      - cmake/gcc_flags.cmake
+      - tests/fmt_formatter/project/main.cpp
+      - tools/astyle/.astylerc
   workflow_dispatch:
 
 # we don't want to have concurrent jobs, and we don't want to cancel running jobs to avoid broken publications
@@ -23,7 +33,7 @@ jobs:
       contents: write
 
     if: github.repository == 'nlohmann/json'
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
@@ -31,6 +41,8 @@ jobs:
           egress-policy: audit
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
 
       - name: Install virtual environment
         run: make install_venv -C docs/mkdocs

.github/workflows/ubuntu.yml

@@ -100,7 +100,7 @@ jobs:
     container: ubuntu:focal
     strategy:
       matrix:
-        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_no_thread_local]
+        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_no_thread_local]
     steps:
       - name: Install build-essential
         run: apt-get update ; apt-get install -y build-essential unzip wget git libssl-dev
@@ -346,6 +346,8 @@ jobs:
     container: intel/oneapi-hpckit:latest
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
       - name: Get latest CMake and ninja
         uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
       - name: Run CMake
@@ -358,6 +360,8 @@ jobs:
     container: nvcr.io/nvidia/nvhpc:25.5-devel-cuda12.9-ubuntu22.04
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
       - name: Get latest CMake and ninja
         uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
       - name: Run CMake

.github/workflows/windows.yml

@@ -87,6 +87,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
       - name: Get latest CMake and ninja
         uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
       - name: Set extra CXX_FLAGS for latest std_version
@@ -123,6 +125,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
       - name: Run CMake (Release)
         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'

CMakeLists.txt

@@ -55,6 +55,7 @@ option(JSON_Diagnostic_Positions           "Enable diagnostic positions." OFF)
 option(JSON_GlobalUDLs                     "Place user-defined string literals in the global namespace." ON)
 option(JSON_ImplicitConversions            "Enable implicit conversions." ON)
 option(JSON_DisableEnumSerialization       "Disable default integer enum serialization." OFF)
+option(JSON_DisableTupleReferenceConversion "Disable conversion from a one-element tuple of a JSON reference." OFF)
 option(JSON_LegacyDiscardedValueComparison "Enable legacy discarded value comparison." OFF)
 option(JSON_Install                        "Install CMake targets during install step." ${MAIN_PROJECT})
 option(JSON_MultipleHeaders                "Use non-amalgamated version of the library." ON)
@@ -101,6 +102,10 @@ if (JSON_DisableEnumSerialization)
     message(STATUS "Enum integer serialization is disabled (JSON_DISABLE_ENUM_SERIALIZATION=1)")
 endif()
 
+if (JSON_DisableTupleReferenceConversion)
+    message(STATUS "Tuple reference conversion is disabled (JSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1)")
+endif()
+
 if (JSON_LegacyDiscardedValueComparison)
     message(STATUS "Legacy discarded value comparison enabled (JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1)")
 endif()
@@ -143,6 +148,7 @@ target_compile_definitions(
     $<$<NOT:$<BOOL:${JSON_GlobalUDLs}>>:JSON_USE_GLOBAL_UDLS=0>
     $<$<NOT:$<BOOL:${JSON_ImplicitConversions}>>:JSON_USE_IMPLICIT_CONVERSIONS=0>
     $<$<BOOL:${JSON_DisableEnumSerialization}>:JSON_DISABLE_ENUM_SERIALIZATION=1>
+    $<$<BOOL:${JSON_DisableTupleReferenceConversion}>:JSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1>
     $<$<BOOL:${JSON_Diagnostics}>:JSON_DIAGNOSTICS=1>
     $<$<BOOL:${JSON_Diagnostic_Positions}>:JSON_DIAGNOSTIC_POSITIONS=1>
     $<$<BOOL:${JSON_LegacyDiscardedValueComparison}>:JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1>

Makefile

@@ -1,4 +1,4 @@
-.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel
+.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel natvis macro_builder_check
 
 ##########################################################################
 # configuration
@@ -24,6 +24,9 @@ AMALGAMATED_FWD_FILE=single_include/nlohmann/json_fwd.hpp
 # json_literals.hpp only includes <nlohmann/json.hpp>, so it is copied verbatim
 AMALGAMATED_LITERALS_FILE=single_include/nlohmann/json_literals.hpp
 
+# the header with the argument-counting macros generated by tools/macro_builder
+MACRO_SCOPE_HPP=include/nlohmann/detail/macro_scope.hpp
+
 
 ##########################################################################
 # documentation of the Makefile's targets
@@ -36,13 +39,9 @@ all:
 	@echo "ChangeLog.md - generate ChangeLog file"
 	@echo "check-amalgamation - check whether sources have been amalgamated and BUILD.bazel is up to date"
 	@echo "clean - remove built files"
-	@echo "doctest - compile example files and check their output"
+	@echo "fuzzing - see tests/fuzzing.md for how to build and run the fuzzers"
-	@echo "fuzz_testing - prepare fuzz testing of the JSON parser"
+	@echo "macro_builder_check - check that macro_scope.hpp matches tools/macro_builder's output"
-	@echo "fuzz_testing_bon8 - prepare fuzz testing of the BON8 parser"
+	@echo "natvis - regenerate nlohmann_json.natvis from the current ABI tags and version"
-	@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"
-	@echo "fuzz_testing_ubjson - prepare fuzz testing of the UBJSON parser"
 	@echo "pretty - beautify code with Artistic Style"
 	@echo "run_benchmarks - build and run benchmarks"
 	@echo "update_hedley - download Hedley and regenerate hedley.hpp / hedley_undef.hpp"
@@ -61,74 +60,6 @@ run_benchmarks:
 	cd cmake-build-benchmarks ; ./json_benchmarks
 
 
-##########################################################################
-# fuzzing
-##########################################################################
-
-# the overall fuzz testing target
-fuzz_testing:
-	rm -fr fuzz-testing
-	mkdir -p fuzz-testing fuzz-testing/testcases fuzz-testing/out
-	$(MAKE) parse_afl_fuzzer -C tests CXX=afl-clang++
-	mv tests/parse_afl_fuzzer fuzz-testing/fuzzer
-	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
-	$(MAKE) parse_bson_fuzzer -C tests CXX=afl-clang++
-	mv tests/parse_bson_fuzzer fuzz-testing/fuzzer
-	find tests/data -size -5k -name *.bson | xargs -I{} cp "{}" fuzz-testing/testcases
-	@echo "Execute: afl-fuzz -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer"
-
-fuzz_testing_cbor:
-	rm -fr fuzz-testing
-	mkdir -p fuzz-testing fuzz-testing/testcases fuzz-testing/out
-	$(MAKE) parse_cbor_fuzzer -C tests CXX=afl-clang++
-	mv tests/parse_cbor_fuzzer fuzz-testing/fuzzer
-	find tests/data -size -5k -name *.cbor | xargs -I{} cp "{}" fuzz-testing/testcases
-	@echo "Execute: afl-fuzz -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer"
-
-fuzz_testing_msgpack:
-	rm -fr fuzz-testing
-	mkdir -p fuzz-testing fuzz-testing/testcases fuzz-testing/out
-	$(MAKE) parse_msgpack_fuzzer -C tests CXX=afl-clang++
-	mv tests/parse_msgpack_fuzzer fuzz-testing/fuzzer
-	find tests/data -size -5k -name *.msgpack | xargs -I{} cp "{}" fuzz-testing/testcases
-	@echo "Execute: afl-fuzz -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer"
-
-fuzz_testing_ubjson:
-	rm -fr fuzz-testing
-	mkdir -p fuzz-testing fuzz-testing/testcases fuzz-testing/out
-	$(MAKE) parse_ubjson_fuzzer -C tests CXX=afl-clang++
-	mv tests/parse_ubjson_fuzzer fuzz-testing/fuzzer
-	find tests/data -size -5k -name *.ubjson | xargs -I{} cp "{}" fuzz-testing/testcases
-	@echo "Execute: afl-fuzz -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer"
-
-fuzzing-start:
-	afl-fuzz -S fuzzer1 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -S fuzzer2 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -S fuzzer3 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -S fuzzer4 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -S fuzzer5 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -S fuzzer6 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -S fuzzer7 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer > /dev/null &
-	afl-fuzz -M fuzzer0 -i fuzz-testing/testcases -o fuzz-testing/out fuzz-testing/fuzzer
-
-fuzzing-stop:
-	-killall fuzzer
-	-killall afl-fuzz
-
-
 ##########################################################################
 # Static analysis
 ##########################################################################
@@ -158,10 +89,6 @@ install_astyle:
 pretty: install_astyle
 	$(ASTYLE) --project=tools/astyle/.astylerc $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) docs/mkdocs/docs/examples/*.cpp
 
-# call the Clang-Format on all source files
-pretty_format:
-	for FILE in $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) docs/mkdocs/docs/examples/*.cpp; do echo $$FILE; clang-format -i $$FILE; done
-
 # create single header files and pretty print
 amalgamate: $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE)
 	$(MAKE) pretty
@@ -178,8 +105,26 @@ $(AMALGAMATED_FWD_FILE): $(SRCS)
 $(AMALGAMATED_LITERALS_FILE): include/nlohmann/json_literals.hpp
 	cp include/nlohmann/json_literals.hpp $(AMALGAMATED_LITERALS_FILE)
 
+# regenerate nlohmann_json.natvis from the ABI tags and version in include/nlohmann/detail/abi_macros.hpp
+natvis:
+	python3 tools/generate_natvis/generate_natvis.py .
+
+# regenerate the two tools/macro_builder blocks of $(MACRO_SCOPE_HPP) (see its README.md) and diff against the
+# checked-in header; phony, because it never writes $(MACRO_SCOPE_HPP) itself
+macro_builder_check:
+	@set -e; \
+	TMPDIR=$$(mktemp -d ./macro_builder_check.XXXXXX); \
+	trap 'rm -rf "$$TMPDIR"' EXIT; \
+	$(CXX) -std=c++11 tools/macro_builder/main.cpp -o "$$TMPDIR/macro_builder"; \
+	"$$TMPDIR/macro_builder" > "$$TMPDIR/paste.hpp"; \
+	"$$TMPDIR/macro_builder" type_body > "$$TMPDIR/type_body.hpp"; \
+	$(ASTYLE) --project=tools/astyle/.astylerc --suffix=none --quiet "$$TMPDIR/paste.hpp" "$$TMPDIR/type_body.hpp"; \
+	sed -n '/^#define NLOHMANN_JSON_EXPAND( x ) x$$/,/^#define NLOHMANN_JSON_DOUBLE_PASTE63(/p' $(MACRO_SCOPE_HPP) > "$$TMPDIR/paste_actual.hpp"; \
+	sed -n '/^#define NLOHMANN_JSON_TYPE_BODY(Prefix, \.\.\.)/,/^        NLOHMANN_JSON_TYPE_BODY_SENTINEL))$$/p' $(MACRO_SCOPE_HPP) > "$$TMPDIR/type_body_actual.hpp"; \
+	diff "$$TMPDIR/paste.hpp" "$$TMPDIR/paste_actual.hpp" || (echo "===================================================================\n  $(MACRO_SCOPE_HPP) (NLOHMANN_JSON_EXPAND..NLOHMANN_JSON_DOUBLE_PASTE63) is out of date!\n  Regenerate it, see tools/macro_builder/README.md.\n===================================================================" ; exit 1); \
+	diff "$$TMPDIR/type_body.hpp" "$$TMPDIR/type_body_actual.hpp" || (echo "===================================================================\n  $(MACRO_SCOPE_HPP) (NLOHMANN_JSON_TYPE_BODY) is out of date!\n  Regenerate it, see tools/macro_builder/README.md.\n===================================================================" ; exit 1)
+
 # check if file single_include/nlohmann/json.hpp has been amalgamated from the nlohmann sources
-# Note: this target is called by Travis
 check-amalgamation:
 	@mv $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~
 	@mv $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~
@@ -195,6 +140,11 @@ check-amalgamation:
 	@$(MAKE) BUILD.bazel
 	@diff BUILD.bazel BUILD.bazel~ || (echo "===================================================================\n  BUILD.bazel is out of date! Please run 'make BUILD.bazel'.\n===================================================================" ; mv BUILD.bazel~ BUILD.bazel ; false)
 	@mv BUILD.bazel~ BUILD.bazel
+	@mv nlohmann_json.natvis nlohmann_json.natvis~
+	@$(MAKE) natvis
+	@diff nlohmann_json.natvis nlohmann_json.natvis~ || (echo "===================================================================\n  nlohmann_json.natvis is out of date! Please run 'make natvis'.\n===================================================================" ; mv nlohmann_json.natvis~ nlohmann_json.natvis ; false)
+	@mv nlohmann_json.natvis~ nlohmann_json.natvis
+	@$(MAKE) macro_builder_check
 
 # generate the Bazel BUILD file; phony, because a removed header would not trigger a rebuild
 BUILD.bazel:
@@ -246,7 +196,7 @@ release: include.zip json.tar.xz
 	cp $(AMALGAMATED_FWD_FILE) release_files
 	cp $(AMALGAMATED_LITERALS_FILE) release_files
 	mv $(AMALGAMATED_FILE).asc $(AMALGAMATED_FWD_FILE).asc $(AMALGAMATED_LITERALS_FILE).asc json.tar.xz json.tar.xz.asc include.zip include.zip.asc release_files
-	cd release_files ; shasum -a 256 json.hpp include.zip json.tar.xz > hashes.txt
+	cd release_files ; shasum -a 256 $$(find . -type f -not -name '*.asc' | sed 's|^\./||' | sort) > hashes.txt
 
 
 ##########################################################################
@@ -256,7 +206,6 @@ release: include.zip json.tar.xz
 # clean up
 clean:
 	rm -fr fuzz fuzz-testing *.dSYM tests/*.dSYM
-	rm -fr benchmarks/files/numbers/*.json
 	rm -fr cmake-build-benchmarks fuzz-testing cmake-build-pvs-studio release_files
 	$(MAKE) clean -Cdocs
 

cmake/ci.cmake

@@ -276,6 +276,20 @@ add_custom_target(ci_test_disableenumserialization
     COMMENT "Compile and test with enum serialization disabled"
 )
 
+###############################################################################
+# Disable conversion from a one-element tuple of a JSON reference.
+###############################################################################
+
+add_custom_target(ci_test_disabletuplereferenceconversion
+    COMMAND ${CMAKE_COMMAND}
+    -DCMAKE_BUILD_TYPE=Debug -GNinja
+    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_DisableTupleReferenceConversion=ON
+    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_disabletuplereferenceconversion
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_disabletuplereferenceconversion
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_disabletuplereferenceconversion && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
+    COMMENT "Compile and test with tuple reference conversion disabled"
+)
+
 ###############################################################################
 # Skip the multiple-inclusion library version check.
 ###############################################################################

docs/Makefile

@@ -11,20 +11,31 @@ EXAMPLES = $(wildcard mkdocs/docs/examples/*.cpp)
 
 cxx_standard = $(lastword c++11 $(filter c++%, $(subst ., ,$1)))
 
+# common compile flags for the stand-alone example files
+EXAMPLE_CPPFLAGS = -I $(SRCDIR) -DJSON_USE_GLOBAL_UDLS=0
+EXAMPLE_WARNFLAGS = -Werror=deprecated-declarations
+
+# examples that document deprecated API and are allowed to use it
+DEPRECATED_EXAMPLES = $(addprefix mkdocs/docs/examples/, \
+	json_pointer__operator__equal_stringtype \
+	json_pointer__operator__notequal_stringtype \
+	json_pointer__operator_string_t)
+$(DEPRECATED_EXAMPLES:=.output) $(DEPRECATED_EXAMPLES:=.test): EXAMPLE_WARNFLAGS = -Wno-deprecated-declarations
+
 # create output from a stand-alone example file
 %.output: %.cpp
-	@echo "standard $(call cxx_standard $(<:.cpp=))"
+	@echo "standard $(call cxx_standard,$(<:.cpp=))"
 	$(MAKE) $(<:.cpp=) \
-		CPPFLAGS="-I $(SRCDIR) -DJSON_USE_GLOBAL_UDLS=0" \
+		CPPFLAGS="$(EXAMPLE_CPPFLAGS)" \
-		CXXFLAGS="-std=$(call cxx_standard,$(<:.cpp=)) -Wno-deprecated-declarations"
+		CXXFLAGS="-std=$(call cxx_standard,$(<:.cpp=)) $(EXAMPLE_WARNFLAGS)"
 	./$(<:.cpp=) > $@
 	rm $(<:.cpp=)
 
 # compare created output with current output of the example files
 %.test: %.cpp
 	$(MAKE) $(<:.cpp=) \
-		CPPFLAGS="-I $(SRCDIR) -DJSON_USE_GLOBAL_UDLS=0" \
+		CPPFLAGS="$(EXAMPLE_CPPFLAGS)" \
-		CXXFLAGS="-std=$(call cxx_standard,$(<:.cpp=)) -Wno-deprecated-declarations"
+		CXXFLAGS="-std=$(call cxx_standard,$(<:.cpp=)) $(EXAMPLE_WARNFLAGS)"
 	./$(<:.cpp=) > $@
 	diff $@ $(<:.cpp=.output)
 	rm $(<:.cpp=) $@

docs/docset/Info.plist

@@ -13,7 +13,7 @@
     <key>dashIndexFilePath</key>
     <string>index.html</string>
     <key>DashDocSetFallbackURL</key>
-    <string>https://nlohmann.github.io/json/</string>
+    <string>https://json.nlohmann.me/</string>
     <key>isJavaScriptEnabled</key>
     <true/>
 </dict>

docs/docset/Makefile

@@ -52,35 +52,25 @@ install_docset_zeal: JSON_for_Modern_C++.docset
 	mkdir -p $$docset_root; \
 	cp -r JSON_for_Modern_C++.docset $$docset_root/
 
+# both targets below compare the docset search index with the mkdocs page
+# set. They share the same normalization (docs/foo/index.md and
+# docs/foo.md both become foo/index.html, the URL mkdocs itself would
+# give the page; the top-level index.md is excluded, as it is not part
+# of the hand-curated docSet.sql) and use comm(1) on two sorted lists
+# instead of running a sqlite3 query, or an O(n*m) nested shell loop,
+# once per page.
+DOCSET_INDEX_PATHS=$(shell sqlite3 docSet.dsidx "SELECT DISTINCT path FROM searchIndex" | sort)
+DOCSET_PAGE_PATHS=$(shell echo '$(MKDOCS_PAGES)' | tr ' ' '\n' | grep -v '^index\.md$$' | $(SED) -E 's@/index\.md$$@/index.html@; s@\.md$$@/index.html@' | sort)
+
 # list mkdocs pages missing from the docset index
 .PHONY: list_missing_pages
 list_missing_pages: docSet.dsidx
-	@for page in $(MKDOCS_PAGES); do \
+	@comm -23 <(echo '$(DOCSET_PAGE_PATHS)' | tr ' ' '\n') <(echo '$(DOCSET_INDEX_PATHS)' | tr ' ' '\n')
-		case "$$page" in \
-			*/index.md) path=$${page/\/index.md/} ;; \
-			*)          path=$${page/.md/}        ;; \
-		esac; \
-		if [ "x$$page" != "xindex.md" -a "x$$(sqlite3 docSet.dsidx "SELECT COUNT(*) FROM searchIndex WHERE path='$$path/index.html'")" = "x0" ]; then \
-			echo $$page; \
-		fi \
-	done
 
 # list paths in the docset index without a corresponding mkdocs page
 .PHONY: list_removed_paths
 list_removed_paths: docSet.dsidx
-	@for path in $$(sqlite3 docSet.dsidx "SELECT path FROM searchIndex"); do \
+	@comm -13 <(echo '$(DOCSET_PAGE_PATHS)' | tr ' ' '\n') <(echo '$(DOCSET_INDEX_PATHS)' | tr ' ' '\n')
-		page=$${path/\/index.html/.md}; \
-		page_index=$${path/index.html/index.md}; \
-		page_found=0; \
-		for p in $(MKDOCS_PAGES); do \
-			if [ "x$$p" = "x$$page" -o "x$$p" = "x$$page_index" ]; then \
-				page_found=1; \
-			fi \
-		done; \
-		if [ "x$$page_found" = "x0" ]; then \
-			echo $$path; \
-		fi \
-	done
 
 .PHONY: clean
 clean:

docs/docset/README.md

@@ -7,10 +7,11 @@ documentation browsers like [Dash](https://kapeli.com/dash), [Velocity](https://
 The docset can be created with
 
 ```sh
-make nlohmann_json.docset
+make JSON_for_Modern_C++.docset
 ```
 
-The generated folder `nlohmann_json.docset` can then be opened in the documentation browser.
+The generated folder `JSON_for_Modern_C++.docset` can then be opened in the documentation browser. `make all` builds a
+`JSON_for_Modern_C++.tgz` archive instead, and `make install_docset_zeal` installs the docset for Zeal directly.
 
 A recent version is also part of the [Dash user contributions](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B).
 

docs/docset/docSet.sql

@@ -210,6 +210,7 @@ INSERT INTO searchIndex(name, type, path) VALUES ('JSON_CATCH_USER', 'Macro', 'a
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DIAGNOSTICS', 'Macro', 'api/macros/json_diagnostics/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DIAGNOSTIC_POSITIONS', 'Macro', 'api/macros/json_diagnostic_positions/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DISABLE_ENUM_SERIALIZATION', 'Macro', 'api/macros/json_disable_enum_serialization/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('JSON_DISABLE_TUPLE_REFERENCE_CONVERSION', 'Macro', 'api/macros/json_disable_tuple_reference_conversion/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_11', 'Macro', 'api/macros/json_has_cpp_11/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_14', 'Macro', 'api/macros/json_has_cpp_11/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_17', 'Macro', 'api/macros/json_has_cpp_11/index.html');

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

@@ -159,6 +159,8 @@ basic_json(basic_json&& other) noexcept;
     - `CompatibleType` is not `basic_json` (to avoid hijacking copy/move constructors),
     - `CompatibleType` is not a different `basic_json` type (i.e. with different template arguments)
     - `CompatibleType` is not a `basic_json` nested type (e.g., `json_pointer`, `iterator`, etc.)
+    - if [`JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../macros/json_disable_tuple_reference_conversion.md) is defined
+      to `1`: `CompatibleType` is not a one-element `std::tuple` holding a reference to `basic_json`
     - `json_serializer<U>` (with `U = uncvref_t<CompatibleType>`) has a `to_json(basic_json_t&, CompatibleType&&)`
        method
 

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

@@ -51,7 +51,7 @@ range will yield over/underflow when used in a constructor. During deserializati
 will automatically be stored as [`number_unsigned_t`](number_unsigned_t.md) or [`number_float_t`](number_float_t.md).
 
 [RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
-> Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are
+> Note that when such software is used, numbers that are integers and are in the range [-2<sup>53</sup>+1, 2<sup>53</sup>-1] are
 > interoperable in the sense that implementations will agree exactly on their numeric values.
 
 As this range is a subrange of the exactly supported range [INT64_MIN, INT64_MAX], this class's integer type is

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

@@ -52,7 +52,7 @@ when used in a constructor. During deserialization, too large or small integer n
 as [`number_integer_t`](number_integer_t.md) or [`number_float_t`](number_float_t.md).
 
 [RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
-> Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are
+> Note that when such software is used, numbers that are integers and are in the range [-2<sup>53</sup>+1, 2<sup>53</sup>-1] are
 > interoperable in the sense that implementations will agree exactly on their numeric values.
 
 As this range is a subrange (when considered in conjunction with the `number_integer_t` type) of the exactly supported

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

@@ -54,7 +54,7 @@ classDiagram
 
 ## Notes
 
-For an input with $n$ bytes, 1 is the index of the first character and $n+1$ is the index of the terminating null byte
+For an input with <i>n</i> bytes, 1 is the index of the first character and <i>n</i>+1 is the index of the terminating null byte
 or the end of file. This also holds true when reading a byte vector for binary formats.
 
 ## Examples

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

@@ -53,6 +53,7 @@ header. See also the [macro overview page](../../features/macros.md).
 
 - [**JSON_BRACE_INIT_COPY_SEMANTICS**](json_brace_init_copy_semantics.md) - opt in to copy/move semantics for single-element brace initialization
 - [**JSON_DISABLE_ENUM_SERIALIZATION**](json_disable_enum_serialization.md) - switch off default serialization/deserialization functions for enums
+- [**JSON_DISABLE_TUPLE_REFERENCE_CONVERSION**](json_disable_tuple_reference_conversion.md) - switch off conversion from a one-element tuple of a JSON reference
 - [**JSON_USE_IMPLICIT_CONVERSIONS**](json_use_implicit_conversions.md) - control implicit conversions
 
 ## Comparison behavior

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

@@ -0,0 +1,114 @@
+# JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
+
+```cpp
+#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION /* value */
+```
+
+When defined to `1`, a `basic_json` value can no longer be constructed from a one-element `std::tuple` whose element is
+a reference to that `basic_json` type, such as `std::tuple<json&>`, `std::tuple<const json&>`, or `std::tuple<json&&>`.
+These are the tuples created by `std::forward_as_tuple(j)`.
+
+## Default definition
+
+The default value is `0` (disabled — existing behavior is preserved).
+
+```cpp
+#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
+```
+
+## Notes
+
+!!! note "Background"
+
+    By default, `basic_json` can be constructed from any `std::tuple` whose elements can be converted to JSON; the result
+    is an array. This includes `std::tuple<json&>`, which becomes a one-element array.
+
+    `std::tuple` only converts another tuple element by element if its element type cannot be constructed from the whole
+    source tuple. Because `json` *can* be constructed from `std::tuple<json&>`, `std::tuple` instead converts the whole
+    tuple into a single `json` value. This has two surprising effects:
+
+    ```cpp
+    json j = true;
+
+    // rejected by some standard libraries (e.g., libc++); with others, the
+    // reference binds to a temporary that is destroyed right away
+    std::tuple<const json&> t1(std::forward_as_tuple(j));
+
+    // compiles, but std::get<0>(t2) is [true], not true
+    std::tuple<json> t2(std::forward_as_tuple(j));
+    ```
+
+    Enabling this macro removes the conversion, so both tuples are converted element by element: `std::get<0>(t1)`
+    refers to `j`, and `std::get<0>(t2)` is a copy of `j` (see [#2226](https://github.com/nlohmann/json/issues/2226)).
+
+!!! warning "Opt-in only"
+
+    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no effect.
+
+!!! note "Affected conversions"
+
+    Only one-element tuples holding a reference to the **same** `basic_json` type are affected. Constructing a JSON value
+    from them no longer compiles:
+
+    ```cpp
+    json j = true;
+    json a = std::forward_as_tuple(j);  // error with the macro enabled
+    json b = json::array({j});          // use this instead: [true]
+    ```
+
+    Tuples holding a JSON value (`std::make_tuple(j)`), tuples with more than one element, and tuples holding references
+    to other types (including other `basic_json` specializations) are converted to arrays as before.
+
+!!! hint "CMake option"
+
+    This behavior can also be controlled with the CMake option
+    [`JSON_DisableTupleReferenceConversion`](../../integration/cmake.md#json_disabletuplereferenceconversion)
+    (`OFF` by default) which defines `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION` accordingly.
+
+## Examples
+
+??? example "Default behavior (macro not defined)"
+
+    ```cpp
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        json j = true;
+
+        std::tuple<json> t(std::forward_as_tuple(j));
+        // std::get<0>(t) is [true] -- the whole tuple was converted
+    }
+    ```
+
+??? example "Conversion disabled (macro defined to 1)"
+
+    ```cpp
+    #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 1
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        json j = true;
+
+        std::tuple<json> t(std::forward_as_tuple(j));
+        // std::get<0>(t) is true -- a copy of j
+
+        std::tuple<const json&> r(std::forward_as_tuple(j));
+        // std::get<0>(r) refers to j
+    }
+    ```
+
+## See also
+
+- [**basic_json(CompatibleType&&)**](../basic_json/basic_json.md) - the affected constructor
+- [:simple-cmake: JSON_DisableTupleReferenceConversion](../../integration/cmake.md#json_disabletuplereferenceconversion) -
+  CMake option to control the macro
+
+## Version history
+
+- Added in version 3.13.0.

docs/mkdocs/docs/api/operator_gtgt.md

@@ -18,6 +18,10 @@ Deserializes an input stream to a JSON value.
 
 the stream `i`
 
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in `j`.
+
 ## Exceptions
 
 - Throws [`parse_error.101`](../home/exceptions.md#jsonexceptionparse_error101) in case of an unexpected token, or if
@@ -125,3 +129,5 @@ being read.
   the stream; planned to become the default in version 4.0.0.
 - Fixed a null pointer dereference for an `std::istream` without a stream buffer (now throws `parse_error.101`), and a
   crash (`std::terminate`) when `i` has `eofbit` in its exception mask, in version 3.13.0.
+- Changed to the strong exception safety guarantee in version 3.13.0: `j` is no longer left with a partially parsed
+  value if parsing throws.

docs/mkdocs/docs/examples/parse__iterator_pair.link

@@ -1 +0,0 @@
-<a target="_blank" href="https://wandbox.org/permlink/hUJYo1HWmfTBLMGn"><b>online</b></a>

docs/mkdocs/docs/examples/parse__pointers.link

@@ -1 +0,0 @@
-<a target="_blank" href="https://wandbox.org/permlink/AWbpa8e1xRV3y4MM"><b>online</b></a>

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

@@ -61,7 +61,7 @@ The library uses the following mapping from JSON values types to BJData types ac
 
     The following values can **not** be converted to a BJData value:
 
-      - strings with more than 18446744073709551615 bytes, i.e., $2^{64}-1$ bytes (theoretical)
+      - strings with more than 18446744073709551615 bytes, i.e., 2<sup>64</sup>-1 bytes (theoretical)
 
 !!! info "Unused BJData markers"
 

docs/mkdocs/docs/features/macros.md

@@ -83,6 +83,13 @@ When defined, default parse and serialize functions for enums are excluded and h
 
 See [full documentation of `JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md).
 
+## `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`
+
+When defined to `1`, a JSON value can no longer be created from a one-element `std::tuple` holding a reference to a JSON
+value, such as the result of `std::forward_as_tuple(j)`. This lets `std::tuple` convert such tuples element-wise.
+
+See [full documentation of `JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md).
+
 ## `JSON_NO_AUTOMATIC_UDLS`
 
 When defined, `<nlohmann/json.hpp>` does not include `<nlohmann/json_literals.hpp>` with the user-defined string literals

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

@@ -273,7 +273,7 @@ When the default type is used, the maximal unsigned integer number that can be s
 
 [RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
 
-> Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are interoperable in the sense that implementations will agree exactly on their numeric values.
+> Note that when such software is used, numbers that are integers and are in the range [-2<sup>53</sup>+1, 2<sup>53</sup>-1] are interoperable in the sense that implementations will agree exactly on their numeric values.
 
 As this range is a subrange of the exactly supported range [`INT64_MIN`, `INT64_MAX`], this class's integer type is interoperable.
 

docs/mkdocs/docs/features/types/number_handling.md

@@ -48,7 +48,7 @@ On number interoperability, the following remarks are made:
     for numeric magnitude and precision than is widely available.
     
     Note that when such software is used, numbers that are integers and
-    are in the range $[-2^{53}+1, 2^{53}-1]$ are interoperable in the
+    are in the range [-2<sup>53</sup>+1, 2<sup>53</sup>-1] are interoperable in the
     sense that implementations will agree exactly on their numeric
     values.
 
@@ -95,9 +95,9 @@ This is the same behavior as the code `#!c double x = 3.141592653589793238462643
 
 !!! success "Interoperability"
 
-    - The library is interoperable with respect to the specification, because its supported range $[-2^{63}, 2^{64}-1]$ is
+    - The library is interoperable with respect to the specification, because its supported range [-2<sup>63</sup>, 2<sup>64</sup>-1] is
-      larger than the described range $[-2^{53}+1, 2^{53}-1]$.
+      larger than the described range [-2<sup>53</sup>+1, 2<sup>53</sup>-1].
-    - All integers outside the range $[-2^{63}, 2^{64}-1]$, as well as floating-point numbers are stored as `double`.
+    - All integers outside the range [-2<sup>63</sup>, 2<sup>64</sup>-1], as well as floating-point numbers are stored as `double`.
       This also concurs with the specification above.
 
 ### Zeros

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

@@ -389,6 +389,7 @@ using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
 | Functionality                                                                                                                     | Additional requirement                                                                                                                                                                       |
 |-----------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | [`diff`](../../api/basic_json/diff.md), [`items`](../../api/basic_json/items.md), [`std::hash`](../../api/basic_json/std_hash.md) | conversion of a `#!cpp std::size_t` to `StringType`: either assignability from the result of `#!cpp std::to_string`, or an ADL overload `#!cpp void int_to_string(StringType&, std::size_t)` |
+| [`operator/(std::size_t)`](../../api/json_pointer/operator_slash.md)                                                              | the same conversion of a `#!cpp std::size_t` to `StringType` as `diff`, `items`, and `std::hash` above                                                                                       |
 | [`std::hash<basic_json>`](../../api/basic_json/std_hash.md)                                                                       | additionally a specialization of `#!cpp std::hash<StringType>`                                                                                                                               |
 | [`to_bson`](../../api/basic_json/to_bson.md)                                                                                      | `find(value_type)` and `npos`                                                                                                                                                                |
 | [`parse`](../../api/basic_json/parse.md) from a `string_t`                                                                        | the input adapters must accept it; otherwise pass a character range                                                                                                                          |

docs/mkdocs/docs/integration/cmake.md

@@ -169,6 +169,12 @@ Enable position diagnostics by defining macro [`JSON_DIAGNOSTIC_POSITIONS`](../a
 Disable default `enum` serialization by defining the macro
 [`JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md). This option is `OFF` by default.
 
+### `JSON_DisableTupleReferenceConversion`
+
+Disable the conversion from a one-element `std::tuple` holding a reference to a JSON value by defining the macro
+[`JSON_DISABLE_TUPLE_REFERENCE_CONVERSION`](../api/macros/json_disable_tuple_reference_conversion.md). This option is
+`OFF` by default.
+
 ### `JSON_FastTests`
 
 Skip expensive/slow test suites. This option is `OFF` by default. Depends on `JSON_BuildTests`.

docs/mkdocs/docs/integration/package_managers.md

@@ -678,11 +678,11 @@ to install the [nlohmann-json](https://ports.macports.org/port/nlohmann-json/) p
     1. Create the following files:
 
         ```cpp title="example.cpp"
-        --8<-- "integration/homebrew/example.cpp"
+        --8<-- "integration/macports/example.cpp"
         ```
 
         ```cmake title="CMakeLists.txt"
-        --8<-- "integration/homebrew/CMakeLists.txt"
+        --8<-- "integration/macports/CMakeLists.txt"
         ```
 
     2. Install the package:

docs/mkdocs/mkdocs.yml

@@ -288,6 +288,7 @@ nav:
           - 'JSON_DIAGNOSTICS': api/macros/json_diagnostics.md
           - 'JSON_DIAGNOSTIC_POSITIONS': api/macros/json_diagnostic_positions.md
           - 'JSON_DISABLE_ENUM_SERIALIZATION': api/macros/json_disable_enum_serialization.md
+          - 'JSON_DISABLE_TUPLE_REFERENCE_CONVERSION': api/macros/json_disable_tuple_reference_conversion.md
           - 'JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20': api/macros/json_has_cpp_11.md
           - 'JSON_HAS_EXPERIMENTAL_FILESYSTEM, JSON_HAS_FILESYSTEM': api/macros/json_has_filesystem.md
           - 'JSON_HAS_RANGES': api/macros/json_has_ranges.md
@@ -351,7 +352,6 @@ markdown_extensions:
   - toc:
       permalink: true
   - md_in_html
-  - pymdownx.arithmatex
   - pymdownx.betterem:
       smart_enable: all
   - pymdownx.caret
@@ -443,6 +443,3 @@ plugins:
 
 extra_css:
   - css/custom.css
-
-extra_javascript:
-  - https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-MML-AM_CHTML

docs/mkdocs/scripts/check_structure.py

@@ -79,9 +79,9 @@ def check_structure() -> None:
                     report("whitespace/line_length", f"{file}:{lineno+1} ({current_section})", f"line is too long ({len(line)} vs. 160 chars)")
 
                 # sections in `<!-- NOLINT -->` comments are treated as present
-                if line.startswith("<!-- NOLINT"):
+                nolint_match = re.match(r"<!--\s*NOLINT\s+(.*?)\s*-->", line)
-                    current_section = line.strip("<!-- NOLINT")
+                if nolint_match:
-                    current_section = current_section.strip(" -->")
+                    current_section = nolint_match.group(1)
                     existing_sections.append(current_section)
 
                 # check if sections are correct
@@ -97,7 +97,7 @@ def check_structure() -> None:
                             if len(unexpected):
                                 report("style/numbering", f"{file}:{lineno} ({current_section})", f'unexpected overloads: {", ".join([f"({x})" for x in unexpected])}')
 
-                    current_section = line.strip("## ")
+                    current_section = line[3:]
                     existing_sections.append(current_section)
 
                     if current_section in expected_sections:
@@ -141,7 +141,7 @@ def check_structure() -> None:
                 # check that non-example admonitions have titles
                 untitled_admonition = re.match(r"^(\?\?\?|!!!) ([^ ]+)$", line)
                 if untitled_admonition and untitled_admonition.group(2) != "example":
-                    report("style/admonition_title", f"{file}:{lineno} ({current_section})", f'"{untitled_admonition.group(2)}" admonitions should have a title')
+                    report("style/admonition_title", f"{file}:{lineno+1} ({current_section})", f'"{untitled_admonition.group(2)}" admonitions should have a title')
 
                 previous_line = line
 

include/nlohmann/detail/conversions/to_json.hpp

@@ -471,11 +471,13 @@ inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<
     j = { std::get<Idx>(t)... };
 }
 
-#if JSON_BRACE_INIT_COPY_SEMANTICS
+// A one-element braced list does not reliably wrap its element: with
-// JSON_BRACE_INIT_COPY_SEMANTICS makes a one-element braced list copy its
+// JSON_BRACE_INIT_COPY_SEMANTICS it copies it, which would serialize
-// element instead of wrapping it, which would serialize std::tuple<int>{5} as 5
+// std::tuple<int>{5} as 5 rather than [5], and some compilers (e.g., Apple clang
-// rather than [5]. Build what the default deduction builds instead: an object
+// 15 and 16) copy an element that is itself a basic_json even without it, so
-// if the element is a [string, value] pair, a one-element array otherwise.
+// std::tuple<json>{true} became true rather than [true]. Build what the default
+// deduction builds instead: an object if the element is a [string, value] pair,
+// a one-element array otherwise.
 template<typename BasicJsonType, typename Tuple>
 inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<0> /*unused*/)
 {
@@ -493,7 +495,6 @@ inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<
         j = BasicJsonType::array({std::move(element)});
     }
 }
-#endif
 
 template<typename BasicJsonType, typename Tuple>
 inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& /*unused*/, index_sequence<> /*unused*/)

include/nlohmann/detail/input/binary_reader.hpp

@@ -8,7 +8,6 @@
 
 #pragma once
 
-#include <algorithm> // generate_n
 #include <array> // array
 #include <cmath> // ldexp
 #include <cstddef> // size_t
@@ -131,7 +130,8 @@ class binary_reader
     ~binary_reader() = default;
 
     /*!
-    @param[in] format  the binary format to parse
+    @brief parse in the format the constructor was given
+
     @param[in] sax_    a SAX event processor
     @param[in] strict  whether to expect the input to be consumed completed
     @param[in] tag_handler  how to treat CBOR tags
@@ -139,9 +139,8 @@ class binary_reader
     @return whether parsing was successful: the input was read without errors,
             and no SAX event returned false
     */
-    JSON_HEDLEY_NON_NULL(3)
+    JSON_HEDLEY_NON_NULL(2)
-    bool sax_parse(const input_format_t format,
+    bool sax_parse(json_sax_t* sax_,
-                   json_sax_t* sax_,
                    const bool strict = true,
                    const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
     {
@@ -155,14 +154,14 @@ class binary_reader
         ndarray_open = 0;
         bool result = false;
 
-        switch (format)
+        switch (input_format)
         {
             case input_format_t::bson:
                 result = parse_bson_internal();
                 break;
 
             case input_format_t::cbor:
-                result = parse_cbor_internal(true, tag_handler);
+                result = parse_cbor_internal(tag_handler);
                 break;
 
             case input_format_t::msgpack:
@@ -290,6 +289,22 @@ class binary_reader
         return enter_container(/*is_object*/true, len, type_marker);
     }
 
+    /*!
+    @brief close the innermost open array or object
+
+    Pops the container opened by the matching @ref enter_container call and
+    emits the SAX end event. Every format-specific driver otherwise repeated
+    the same pop-then-dispatch sequence at its own close site.
+
+    @return whether the SAX parser accepted the end event
+    */
+    bool leave_container()
+    {
+        const bool is_object = container_stack.back().is_object;
+        container_stack.pop_back();
+        return is_object ? sax->end_object() : sax->end_array();
+    }
+
     //////////
     // BSON //
     //////////
@@ -548,8 +563,8 @@ class binary_reader
             if (element_type == 0) // end of the innermost document
             {
                 // a copy, not a reference: it must stay valid across the
-                // pop_back() below, which destroys the container_stack
+                // pop_back() inside leave_container() below, which destroys
-                // element it would otherwise alias
+                // the container_stack element it would otherwise alias
                 const container_frame top = container_stack.back();
 
                 if (JSON_HEDLEY_UNLIKELY(!check_bson_document_size(top.start_position, top.declared_size)))
@@ -557,8 +572,7 @@ class binary_reader
                     return false;
                 }
 
-                container_stack.pop_back();
+                if (JSON_HEDLEY_UNLIKELY(!leave_container()))
-                if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                 {
                     return false;
                 }
@@ -1057,29 +1071,13 @@ class binary_reader
                 return enter_array(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0x98: // array (one-byte uint8_t for n follows)
-            {
-                std::uint8_t len{};
-                return get_number(input_format_t::cbor, len) && enter_array(static_cast<std::size_t>(len));
-            }
-
             case 0x99: // array (two-byte uint16_t for n follow)
-            {
-                std::uint16_t len{};
-                return get_number(input_format_t::cbor, len) && enter_array(static_cast<std::size_t>(len));
-            }
-
             case 0x9A: // array (four-byte uint32_t for n follow)
-            {
-                std::uint32_t len{};
-                std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && enter_array(size);
-            }
-
             case 0x9B: // array (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "array") && enter_array(size);
+                return get_cbor_argument(len) && get_cbor_container_size(len, size, "array") && enter_array(size);
             }
 
             case 0x9F: // array (indefinite length)
@@ -1113,35 +1111,19 @@ class binary_reader
                 return enter_object(conditional_static_cast<std::size_t>(static_cast<unsigned int>(current) & 0x1Fu));
 
             case 0xB8: // map (one-byte uint8_t for n follows)
-            {
-                std::uint8_t len{};
-                return get_number(input_format_t::cbor, len) && enter_object(static_cast<std::size_t>(len));
-            }
-
             case 0xB9: // map (two-byte uint16_t for n follow)
-            {
-                std::uint16_t len{};
-                return get_number(input_format_t::cbor, len) && enter_object(static_cast<std::size_t>(len));
-            }
-
             case 0xBA: // map (four-byte uint32_t for n follow)
-            {
-                std::uint32_t len{};
-                std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && enter_object(size);
-            }
-
             case 0xBB: // map (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
                 std::size_t size{};
-                return get_number(input_format_t::cbor, len) && get_cbor_container_size(len, size, "map") && enter_object(size);
+                return get_cbor_argument(len) && get_cbor_container_size(len, size, "map") && enter_object(size);
             }
 
             case 0xBF: // map (indefinite length)
                 return enter_object(detail::unknown_size());
 
-            case 0xC0: // tagged item
+            case 0xC0: // tagged item (tag value 0-23, in the head itself)
             case 0xC1:
             case 0xC2:
             case 0xC3:
@@ -1165,6 +1147,27 @@ class binary_reader
             case 0xD5:
             case 0xD6:
             case 0xD7:
+            {
+                if (tag_handler == cbor_tag_handler_t::error)
+                {
+                    auto last_token = get_token_string();
+                    if (!report_repairable_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                                 exception_message(input_format_t::cbor, concat("invalid byte: 0x", last_token), "value"), nullptr)))
+                    {
+                        return false;
+                    }
+                    // when recovering, the tag is ignored, as RFC 8949,
+                    // Section 6.1 suggests for converting to JSON
+                }
+
+                // ignore and store: the tag value is already in the head, so
+                // there is nothing left to read here; the tagged value that
+                // follows is read by the loop in parse_cbor_internal() rather
+                // than by recursing here
+                tag_pending = true;
+                return true;
+            }
+
             case 0xD8: // tagged item (1 byte follows)
             case 0xD9: // tagged item (2 bytes follow)
             case 0xDA: // tagged item (4 bytes follow)
@@ -1187,47 +1190,11 @@ class binary_reader
 
                     case cbor_tag_handler_t::ignore:
                     {
-                        // ignore binary subtype
+                        // ignore the tag's binary subtype argument
-                        switch (current)
+                        std::uint64_t subtype_to_ignore{};
+                        if (!get_cbor_argument(subtype_to_ignore))
                         {
-                            case 0xD8:
+                            return false;
-                            {
-                                std::uint8_t subtype_to_ignore{};
-                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
-                                {
-                                    return false;
-                                }
-                                break;
-                            }
-                            case 0xD9:
-                            {
-                                std::uint16_t subtype_to_ignore{};
-                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
-                                {
-                                    return false;
-                                }
-                                break;
-                            }
-                            case 0xDA:
-                            {
-                                std::uint32_t subtype_to_ignore{};
-                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
-                                {
-                                    return false;
-                                }
-                                break;
-                            }
-                            case 0xDB:
-                            {
-                                std::uint64_t subtype_to_ignore{};
-                                if (!get_number(input_format_t::cbor, subtype_to_ignore))
-                                {
-                                    return false;
-                                }
-                                break;
-                            }
-                            default:
-                                break;
                         }
                         // the tagged value follows; it is read by the loop in
                         // parse_cbor_internal() rather than by recursing here
@@ -1237,57 +1204,15 @@ class binary_reader
 
                     case cbor_tag_handler_t::store:
                     {
-                        binary_t b;
                         // use binary subtype and store in a binary container
-                        switch (current)
+                        std::uint64_t subtype{};
+                        if (!get_cbor_argument(subtype))
                         {
-                            case 0xD8:
+                            return false;
-                            {
-                                std::uint8_t subtype{};
-                                if (!get_number(input_format_t::cbor, subtype))
-                                {
-                                    return false;
-                                }
-                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
-                                break;
-                            }
-                            case 0xD9:
-                            {
-                                std::uint16_t subtype{};
-                                if (!get_number(input_format_t::cbor, subtype))
-                                {
-                                    return false;
-                                }
-                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
-                                break;
-                            }
-                            case 0xDA:
-                            {
-                                std::uint32_t subtype{};
-                                if (!get_number(input_format_t::cbor, subtype))
-                                {
-                                    return false;
-                                }
-                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
-                                break;
-                            }
-                            case 0xDB:
-                            {
-                                std::uint64_t subtype{};
-                                if (!get_number(input_format_t::cbor, subtype))
-                                {
-                                    return false;
-                                }
-                                b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
-                                break;
-                            }
-                            default:
-                            {
-                                // as above, the tagged value is read by the caller
-                                tag_pending = true;
-                                return true;
-                            }
                         }
+                        binary_t b;
+                        b.set_subtype(detail::conditional_static_cast<typename binary_t::subtype_type>(subtype));
+
                         get();
                         // a byte string (the heads accepted by get_cbor_binary) keeps the tag as subtype
                         if ((current >= 0x40 && current <= 0x5B) || current == 0x5F)
@@ -1318,52 +1243,7 @@ class binary_reader
                 return sax->null();
 
             case 0xF9: // Half-Precision Float (two-byte IEEE 754)
-            {
+                return get_half_float(input_format_t::cbor, false);
-                const auto byte1_raw = get();
-                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "number")))
-                {
-                    return false;
-                }
-                const auto byte2_raw = get();
-                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format_t::cbor, "number")))
-                {
-                    return false;
-                }
-
-                const auto byte1 = static_cast<unsigned char>(byte1_raw);
-                const auto byte2 = static_cast<unsigned char>(byte2_raw);
-
-                // Code from RFC 8949, Appendix D, Figure 3:
-                // As half-precision floating-point numbers were only added
-                // to IEEE 754 in 2008, today's programming platforms often
-                // still only have limited support for them. It is very
-                // easy to include at least decoding support for them even
-                // without such support. An example of a small decoder for
-                // half-precision floating-point numbers in the C language
-                // is shown in Fig. 3.
-                const auto half = static_cast<unsigned int>((byte1 << 8u) + byte2);
-                const double val = [&half]
-                {
-                    const int exp = (half >> 10u) & 0x1Fu;
-                    const unsigned int mant = half & 0x3FFu;
-                    JSON_ASSERT(exp <= 31);
-                    JSON_ASSERT(mant <= 1023);
-                    switch (exp)
-                    {
-                        case 0:
-                            return std::ldexp(mant, -24);
-                        case 31:
-                            return (mant == 0)
-                            ? std::numeric_limits<double>::infinity()
-                            : std::numeric_limits<double>::quiet_NaN();
-                        default:
-                            return std::ldexp(mant + 1024, exp - 25);
-                    }
-                }();
-                return sax->number_float((half & 0x8000u) != 0
-                                         ? static_cast<number_float_t>(-val)
-                                         : static_cast<number_float_t>(val), "");
-            }
 
             case 0xFA: // Single-Precision Float (four-byte IEEE 754)
             {
@@ -1759,6 +1639,73 @@ class binary_reader
         }
     }
 
+    /*!
+    @brief read a CBOR argument (additional information 24-27) of the width
+           @ref current announces
+
+    The lower 5 bits of @a current (0x18-0x1B) select a 1/2/4/8-byte
+    big-endian unsigned integer that follows the head byte; this is shared by
+    every major type that uses this encoding (unsigned/negative integers,
+    strings, arrays, maps, tags). Reading always goes through @ref get_number,
+    so EOF is reported the same way as before this helper existed.
+
+    @param[out] value  the decoded argument
+    @return whether reading succeeded
+    */
+    bool get_cbor_argument(std::uint64_t& value)
+    {
+        switch (current & 0x1F)
+        {
+            case 0x18: // 1 byte
+            {
+                std::uint8_t n{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
+                {
+                    return false;
+                }
+                value = n;
+                return true;
+            }
+
+            case 0x19: // 2 bytes
+            {
+                std::uint16_t n{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
+                {
+                    return false;
+                }
+                value = n;
+                return true;
+            }
+
+            case 0x1A: // 4 bytes
+            {
+                std::uint32_t n{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
+                {
+                    return false;
+                }
+                value = n;
+                return true;
+            }
+
+            case 0x1B: // 8 bytes
+            {
+                std::uint64_t n{};
+                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format_t::cbor, n)))
+                {
+                    return false;
+                }
+                value = n;
+                return true;
+            }
+
+            default:                 // LCOV_EXCL_LINE
+                JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
+                return false;        // LCOV_EXCL_LINE
+        }
+    }
+
     /*!
     @brief narrow a definite CBOR array/map length to std::size_t
 
@@ -1791,19 +1738,15 @@ class binary_reader
     enclosing container after each element, so that the nesting depth of the
     input costs heap rather than native stack (see #5104).
 
-    @param[in] get_char  whether a new character should be retrieved from the
-                         input (true) or whether the last read character
-                         @a current should be considered instead
     @param[in] tag_handler how CBOR tags should be treated
 
     @return whether reading the value succeeded
     */
-    bool parse_cbor_internal(const bool get_char,
+    bool parse_cbor_internal(const cbor_tag_handler_t tag_handler)
-                             const cbor_tag_handler_t tag_handler)
     {
         // whether the next value starts at a fresh byte or at the one already
         // read into `current`
-        bool fetch = get_char;
+        bool fetch = true;
 
         // the key currently being read; hoisted out of the loop so that its
         // capacity is reused across elements and across nesting levels
@@ -1846,8 +1789,7 @@ class binary_reader
 
                 if (at_end)
                 {
-                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
-                    if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                     {
                         return false;
                     }
@@ -2035,9 +1977,6 @@ class binary_reader
     // MsgPack //
     /////////////
 
-    /*!
-    @return whether a valid MessagePack value was passed to the SAX parser
-    */
     /*!
     @brief read one MessagePack value
 
@@ -2741,8 +2680,7 @@ class binary_reader
 
                 if (container_stack.back().remaining == 0)
                 {
-                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
-                    if (JSON_HEDLEY_UNLIKELY(is_object ? !sax->end_object() : !sax->end_array()))
                     {
                         return false;
                     }
@@ -2936,20 +2874,16 @@ class binary_reader
     ////////////
 
     /*!
-    @param[in] get_char  whether a new character should be retrieved from the
-                         input (true, default) or whether the last read
-                         character should be considered instead
-
     @return whether a valid UBJSON value was passed to the SAX parser
     */
-    bool parse_ubjson_internal(const bool get_char = true)
+    bool parse_ubjson_internal()
     {
         // the key currently being read; hoisted out of the loop so that its
         // capacity is reused across elements and across nesting levels
         string_t key;
 
         // the type marker of the value to read next
-        char_int_type prefix = get_char ? get_ignore_noop() : current;
+        char_int_type prefix = get_ignore_noop();
 
         while (true)
         {
@@ -3024,8 +2958,7 @@ class binary_reader
                     break;
                 }
 
-                container_stack.pop_back();
+                if (JSON_HEDLEY_UNLIKELY(!leave_container()))
-                if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                 {
                     return false;
                 }
@@ -3233,6 +3166,42 @@ class binary_reader
         return true;
     }
 
+    /*!
+    @brief read a UBJSON/BJData optimized-container count of a signed marker
+           type ('i', 'I', 'l', 'L') and narrow it to std::size_t
+
+    Every signed count marker rejects a negative value the same way (error
+    113); the value_in_range_of check additionally needed for 'L' is only
+    ever live when @a SignedType is std::int64_t on a target where
+    std::size_t is narrower (e.g. 32-bit), since 'i'/'I'/'l' can never exceed
+    std::size_t there.
+
+    @tparam SignedType  std::int8_t, std::int16_t, std::int32_t or std::int64_t
+    @param[out] result  the count narrowed to std::size_t
+    @return whether reading and validating succeeded
+    */
+    template<typename SignedType>
+    bool get_ubjson_signed_count(std::size_t& result)
+    {
+        SignedType number{};
+        if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
+        {
+            return false;
+        }
+        if (JSON_HEDLEY_UNLIKELY(number < 0))
+        {
+            return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
+        }
+        if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::size_t>(number)))
+        {
+            return report_error(chars_read, get_token_string(), out_of_range::create(408,
+                                exception_message(input_format, "integer value overflow", "size"), nullptr));
+        }
+        result = static_cast<std::size_t>(number); // NOLINT(bugprone-signed-char-misuse,cert-str34-c): number is not a char
+        return true;
+    }
+
     /*!
     @param[out] result  determined size
     @param[in,out] is_ndarray  for input, `true` means already inside an ndarray vector
@@ -3265,73 +3234,16 @@ class binary_reader
             }
 
             case 'i':
-            {
+                return get_ubjson_signed_count<std::int8_t>(result);
-                std::int8_t number{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
-                {
-                    return false;
-                }
-                if (number < 0)
-                {
-                    return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
-                                        exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
-                }
-                result = static_cast<std::size_t>(number); // NOLINT(bugprone-signed-char-misuse,cert-str34-c): number is not a char
-                return true;
-            }
 
             case 'I':
-            {
+                return get_ubjson_signed_count<std::int16_t>(result);
-                std::int16_t number{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
-                {
-                    return false;
-                }
-                if (number < 0)
-                {
-                    return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
-                                        exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
-                }
-                result = static_cast<std::size_t>(number);
-                return true;
-            }
 
             case 'l':
-            {
+                return get_ubjson_signed_count<std::int32_t>(result);
-                std::int32_t number{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
-                {
-                    return false;
-                }
-                if (number < 0)
-                {
-                    return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
-                                        exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
-                }
-                result = static_cast<std::size_t>(number);
-                return true;
-            }
 
             case 'L':
-            {
+                return get_ubjson_signed_count<std::int64_t>(result);
-                std::int64_t number{};
-                if (JSON_HEDLEY_UNLIKELY(!get_number(input_format, number)))
-                {
-                    return false;
-                }
-                if (number < 0)
-                {
-                    return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
-                                        exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
-                }
-                if (!value_in_range_of<std::size_t>(number))
-                {
-                    return report_error(chars_read, get_token_string(), out_of_range::create(408,
-                                        exception_message(input_format, "integer value overflow", "size"), nullptr));
-                }
-                result = static_cast<std::size_t>(number);
-                return true;
-            }
 
             case 'u':
             {
@@ -3423,16 +3335,23 @@ class binary_reader
                     result = 1;
                     for (auto i : dim)
                     {
-                        // Pre-multiplication overflow check: if i > 0 and result > SIZE_MAX/i, then result*i would overflow.
+                        // Pre-multiplication overflow check: since the loop above
-                        // This check must happen before multiplication since overflow detection after the fact is unreliable
+                        // already rejected any zero dimension, i is always > 0
-                        // as modular arithmetic can produce any value, not just 0 or SIZE_MAX.
+                        // here, so result > SIZE_MAX/i means result*i would
-                        if (JSON_HEDLEY_UNLIKELY(i > 0 && result > (std::numeric_limits<std::size_t>::max)() / i))
+                        // overflow. This check must happen before multiplication
+                        // since overflow detection after the fact is unreliable,
+                        // as modular arithmetic can produce any value, not just 0
+                        // or SIZE_MAX.
+                        if (JSON_HEDLEY_UNLIKELY(result > (std::numeric_limits<std::size_t>::max)() / i))
                         {
                             return report_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
                         }
                         result *= i;
-                        // Additional post-multiplication check to catch any edge cases the pre-check might miss
+                        // the pre-check above already rules out result becoming 0
-                        if (result == 0 || result == npos)
+                        // by overflow; the only value it cannot rule out is an
+                        // exact match with npos, the sentinel reserved for an
+                        // unknown-size container (see get_ubjson_size_type())
+                        if (result == npos)
                         {
                             return report_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
                         }
@@ -3494,7 +3413,7 @@ class binary_reader
         {
             result.second = get();  // must not ignore 'N', because 'N' maybe the type
             if (input_format == input_format_t::bjdata
-                    && JSON_HEDLEY_UNLIKELY(std::binary_search(bjd_optimized_type_markers.begin(), bjd_optimized_type_markers.end(), result.second)))
+                    && JSON_HEDLEY_UNLIKELY(is_bjd_excluded_optimized_type(result.second)))
             {
                 auto last_token = get_token_string();
                 return report_error(chars_read, last_token, parse_error::create(112, chars_read,
@@ -3638,50 +3557,7 @@ class binary_reader
                 {
                     break;
                 }
-                const auto byte1_raw = get();
+                return get_half_float(input_format, true);
-                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format, "number")))
-                {
-                    return false;
-                }
-                const auto byte2_raw = get();
-                if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format, "number")))
-                {
-                    return false;
-                }
-
-                const auto byte1 = static_cast<unsigned char>(byte1_raw);
-                const auto byte2 = static_cast<unsigned char>(byte2_raw);
-
-                // Code from RFC 8949, Appendix D, Figure 3:
-                // As half-precision floating-point numbers were only added
-                // to IEEE 754 in 2008, today's programming platforms often
-                // still only have limited support for them. It is very
-                // easy to include at least decoding support for them even
-                // without such support. An example of a small decoder for
-                // half-precision floating-point numbers in the C language
-                // is shown in Fig. 3.
-                const auto half = static_cast<unsigned int>((byte2 << 8u) + byte1);
-                const double val = [&half]
-                {
-                    const int exp = (half >> 10u) & 0x1Fu;
-                    const unsigned int mant = half & 0x3FFu;
-                    JSON_ASSERT(exp <= 31);
-                    JSON_ASSERT(mant <= 1023);
-                    switch (exp)
-                    {
-                        case 0:
-                            return std::ldexp(mant, -24);
-                        case 31:
-                            return (mant == 0)
-                            ? std::numeric_limits<double>::infinity()
-                            : std::numeric_limits<double>::quiet_NaN();
-                        default:
-                            return std::ldexp(mant + 1024, exp - 25);
-                    }
-                }();
-                return sax->number_float((half & 0x8000u) != 0
-                                         ? static_cast<number_float_t>(-val)
-                                         : static_cast<number_float_t>(val), "");
             }
 
             case 'd':
@@ -3762,19 +3638,16 @@ class binary_reader
         if (input_format == input_format_t::bjdata && size_and_type.first != npos && (size_and_type.second & (1 << 8)) != 0)
         {
             size_and_type.second &= ~(static_cast<char_int_type>(1) << 8);  // use bit 8 to indicate ndarray, here we remove the bit to restore the type marker
-            auto it = std::lower_bound(bjd_types_map.begin(), bjd_types_map.end(), size_and_type.second, [](const bjd_type & p, char_int_type t)
+            const char* type_name = bjd_type_name(size_and_type.second);
-            {
-                return p.first < t;
-            });
             string_t key = "_ArrayType_";
-            if (JSON_HEDLEY_UNLIKELY(it == bjd_types_map.end() || it->first != size_and_type.second))
+            if (JSON_HEDLEY_UNLIKELY(type_name == nullptr))
             {
                 auto last_token = get_token_string();
                 return report_error(chars_read, last_token, parse_error::create(112, chars_read,
                                     exception_message(input_format, "invalid byte: 0x" + last_token, "type"), nullptr));
             }
 
-            string_t type = it->second; // sax->string() takes a reference
+            string_t type = type_name; // sax->string() takes a reference
             if (JSON_HEDLEY_UNLIKELY(!sax->key(key) || !sax->string(type)))
             {
                 return false;
@@ -4143,8 +4016,7 @@ class binary_reader
 
                 if (at_end)
                 {
-                    container_stack.pop_back();
+                    if (JSON_HEDLEY_UNLIKELY(!leave_container()))
-                    if (JSON_HEDLEY_UNLIKELY(top.is_object ? !sax->end_object() : !sax->end_array()))
                     {
                         return false;
                     }
@@ -4808,6 +4680,68 @@ class binary_reader
         return true;
     }
 
+    /*!
+    @brief read and decode an IEEE 754 half-precision (16-bit) float
+
+    Used by CBOR (big endian) and BJData (little endian); the two formats
+    only differ in the byte order of the two bytes that make up the half.
+
+    @param[in] format       the current format (for diagnostics)
+    @param[in] little_endian whether the two bytes are little endian (BJData)
+                             or big endian (CBOR)
+
+    @return whether reading and decoding succeeded
+    */
+    bool get_half_float(const input_format_t format, const bool little_endian)
+    {
+        const auto byte1_raw = get();
+        if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(format, "number")))
+        {
+            return false;
+        }
+        const auto byte2_raw = get();
+        if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(format, "number")))
+        {
+            return false;
+        }
+
+        const auto byte1 = static_cast<unsigned char>(byte1_raw);
+        const auto byte2 = static_cast<unsigned char>(byte2_raw);
+
+        // Code from RFC 8949, Appendix D, Figure 3:
+        // As half-precision floating-point numbers were only added
+        // to IEEE 754 in 2008, today's programming platforms often
+        // still only have limited support for them. It is very
+        // easy to include at least decoding support for them even
+        // without such support. An example of a small decoder for
+        // half-precision floating-point numbers in the C language
+        // is shown in Fig. 3.
+        const auto half = little_endian
+                          ? static_cast<unsigned int>((byte2 << 8u) + byte1)
+                          : static_cast<unsigned int>((byte1 << 8u) + byte2);
+        const double val = [&half]
+        {
+            const int exp = (half >> 10u) & 0x1Fu;
+            const unsigned int mant = half & 0x3FFu;
+            JSON_ASSERT(exp <= 31);
+            JSON_ASSERT(mant <= 1023);
+            switch (exp)
+            {
+                case 0:
+                    return std::ldexp(mant, -24);
+                case 31:
+                    return (mant == 0)
+                    ? std::numeric_limits<double>::infinity()
+                    : std::numeric_limits<double>::quiet_NaN();
+                default:
+                    return std::ldexp(mant + 1024, exp - 25);
+            }
+        }();
+        return sax->number_float((half & 0x8000u) != 0
+                                 ? static_cast<number_float_t>(-val)
+                                 : static_cast<number_float_t>(val), "");
+    }
+
     /*!
     @brief create a string by reading characters from the input
 
@@ -5353,38 +5287,61 @@ class binary_reader
     /// open: none, its object, or its object and an array inside it
     std::uint8_t ndarray_open = 0;
 
-    // excluded markers in bjdata optimized type
-#define JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_ \
-    make_array<char_int_type>('F', 'H', 'N', 'S', 'T', 'Z', '[', '{')
-
-#define JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_ \
-    make_array<bjd_type>(                      \
-    bjd_type{'B', "byte"},                     \
-    bjd_type{'C', "char"},                     \
-    bjd_type{'D', "double"},                   \
-    bjd_type{'I', "int16"},                    \
-    bjd_type{'L', "int64"},                    \
-    bjd_type{'M', "uint64"},                   \
-    bjd_type{'U', "uint8"},                    \
-    bjd_type{'d', "single"},                   \
-    bjd_type{'i', "int8"},                     \
-    bjd_type{'l', "int32"},                    \
-    bjd_type{'m', "uint32"},                   \
-    bjd_type{'u', "uint16"})
-
   JSON_PRIVATE_UNLESS_TESTED:
-    // lookup tables
+    /*!
-    // NOLINTNEXTLINE(cppcoreguidelines-non-private-member-variables-in-classes)
+    @brief whether @a marker is excluded from BJData's optimized ND-array types
-    const decltype(JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_) bjd_optimized_type_markers =
+    @return whether @a marker is one of 'F', 'H', 'N', 'S', 'T', 'Z', '[', '{'
-        JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_;
 
-    using bjd_type = std::pair<char_int_type, string_t>;
+    Mirrors binary_writer's @ref binary_writer::is_bjdata_excluded_type_marker
-    // NOLINTNEXTLINE(cppcoreguidelines-non-private-member-variables-in-classes)
+    "is_bjdata_excluded_type_marker()`, which encodes the same list the other
-    const decltype(JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_) bjd_types_map =
+    way; keep the two in sync.
-        JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_;
+    */
+    static constexpr bool is_bjd_excluded_optimized_type(const char_int_type marker) noexcept
+    {
+        return marker == '[' || marker == '{' || marker == 'S' || marker == 'H'
+               || marker == 'T' || marker == 'F' || marker == 'N' || marker == 'Z';
+    }
 
-#undef JSON_BINARY_READER_MAKE_BJD_OPTIMIZED_TYPE_MARKERS_
+    /*!
-#undef JSON_BINARY_READER_MAKE_BJD_TYPES_MAP_
+    @brief look up the ND-array element type name for a BJData dtype marker
+    @return the type name ("uint8", "int8", ...), or nullptr if @a marker does
+            not name a known dtype
+
+    A C++11 `constexpr` function cannot contain a `switch`, so this is a
+    plain (non-constexpr) switch instead.
+    */
+    static const char* bjd_type_name(const char_int_type marker)
+    {
+        switch (marker)
+        {
+            case 'B':
+                return "byte";
+            case 'C':
+                return "char";
+            case 'D':
+                return "double";
+            case 'I':
+                return "int16";
+            case 'L':
+                return "int64";
+            case 'M':
+                return "uint64";
+            case 'U':
+                return "uint8";
+            case 'd':
+                return "single";
+            case 'i':
+                return "int8";
+            case 'l':
+                return "int32";
+            case 'm':
+                return "uint32";
+            case 'u':
+                return "uint16";
+            default:
+                return nullptr;
+        }
+    }
 };
 
 #ifndef JSON_HAS_CPP_17

include/nlohmann/detail/json_pointer.hpp

@@ -26,6 +26,7 @@
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/string_concat.hpp>
 #include <nlohmann/detail/string_escape.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -116,7 +117,7 @@ class json_pointer
     /// @sa https://json.nlohmann.me/api/json_pointer/operator_slasheq/
     json_pointer& operator/=(std::size_t array_idx)
     {
-        return *this /= std::to_string(array_idx);
+        return *this /= detail::to_string<string_t>(array_idx);
     }
 
     /// @brief create a new JSON pointer by appending the right JSON pointer at the end of the left JSON pointer
@@ -752,7 +753,7 @@ class json_pointer
                         // would throw out_of_range.404 -- contains() must not throw (see #5395)
                         return false;
                     }
-                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !("0" <= reference_token && reference_token <= "9")))
+                    if (JSON_HEDLEY_UNLIKELY(reference_token.size() == 1 && !('0' <= reference_token[0] && reference_token[0] <= '9')))
                     {
                         // invalid char
                         return false;
@@ -780,7 +781,7 @@ class json_pointer
                     // not throw (see #5395), so such a reference token is treated as "not found"
                     errno = 0; // strtoull() does not reset errno on success
                     char* p_end = nullptr; // NOLINT(misc-const-correctness)
-                    const unsigned long long magnitude = std::strtoull(reference_token.c_str(), &p_end, 10); // NOLINT(runtime/int)
+                    const unsigned long long magnitude = std::strtoull(reference_token.data(), &p_end, 10); // NOLINT(runtime/int)
                     if (JSON_HEDLEY_UNLIKELY(errno == ERANGE // the value exceeds ULLONG_MAX
                                              || magnitude >= static_cast<unsigned long long>((std::numeric_limits<typename BasicJsonType::size_type>::max)()))) // NOLINT(runtime/int)
                     {

include/nlohmann/detail/macro_scope.hpp

@@ -359,6 +359,7 @@ void templated_json_throw(ExceptionType exception)
 
 // Macros to simplify conversion from/to types
 
+// NLOHMANN_JSON_EXPAND to NLOHMANN_JSON_DOUBLE_PASTE63 are generated by tools/macro_builder (see its README.md)
 #define NLOHMANN_JSON_EXPAND( x ) x
 #define NLOHMANN_JSON_GET_MACRO(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32, _33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43, _44, _45, _46, _47, _48, _49, _50, _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, _61, _62, _63, _64, NAME,...) NAME
 #define NLOHMANN_JSON_PASTE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_GET_MACRO(__VA_ARGS__, \
@@ -621,6 +622,10 @@ void templated_json_throw(ExceptionType exception)
 // 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.
+//
+// The slot table below (down to the closing NLOHMANN_JSON_TYPE_BODY_SENTINEL))
+// is generated by tools/macro_builder (see its README.md; run with the
+// "type_body" argument).
 #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, \
@@ -915,3 +920,7 @@ void templated_json_throw(ExceptionType exception)
 #ifndef JSON_DISABLE_ENUM_SERIALIZATION
     #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif
+
+#ifndef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
+    #define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 0
+#endif

include/nlohmann/detail/macro_unscope.hpp

@@ -25,6 +25,7 @@
 #undef JSON_INLINE_VARIABLE
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
+#undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH

include/nlohmann/detail/meta/cpp_future.hpp

@@ -9,7 +9,6 @@
 
 #pragma once
 
-#include <array> // array
 #include <cstddef> // size_t
 #include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
 #include <utility> // index_sequence, make_index_sequence, index_sequence_for
@@ -161,11 +160,5 @@ struct static_const
     constexpr T static_const<T>::value;
 #endif
 
-template<typename T, typename... Args>
-constexpr std::array<T, sizeof...(Args)> make_array(Args&& ... args)
-{
-    return std::array<T, sizeof...(Args)> {{static_cast<T>(std::forward<Args>(args))...}};
-}
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END

include/nlohmann/detail/meta/type_traits.hpp

@@ -636,6 +636,18 @@ template<typename BasicJsonType, typename CompatibleType>
 struct is_compatible_type
     : is_compatible_type_impl<BasicJsonType, CompatibleType> {};
 
+// a one-element std::tuple holding a reference to BasicJsonType, as created by
+// std::forward_as_tuple(j); see JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
+template<typename BasicJsonType, typename T>
+struct is_basic_json_reference_tuple : std::false_type {};
+
+template<typename BasicJsonType, typename T>
+struct is_basic_json_reference_tuple<BasicJsonType, std::tuple<T>>
+{
+    static constexpr bool value =
+        std::is_reference<T>::value && std::is_same<uncvref_t<T>, BasicJsonType>::value;
+};
+
 template<typename BasicJsonType, typename CompatibleArrayType>
 struct is_compatible_binary_type
 {

include/nlohmann/json.hpp

@@ -906,11 +906,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /*!
     @brief how many levels the operation going on in this thread has descended into
 
-    Copying a value and comparing two values share this count. The library never
+    Copying a value, converting one from another specialization, and comparing
-    nests one inside the other - copying a value does not compare one, and
+    two values share this count. The library never nests one of them inside
-    comparing two values does not copy them - and where user code nests them
+    another - none of them does either of the other two on the way - and where
-    anyway, sharing the count only ends a descent sooner than it had to, which
+    user code nests them anyway, sharing the count only ends a descent sooner
-    costs a little speed and is never wrong.
+    than it had to, which costs a little speed and is never wrong.
 
     A byte is enough: the count never exceeds the limit by more than the single
     level that notices the limit has been reached.
@@ -1267,6 +1267,222 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         copy_iteratively(src);
     }
 
+    /*!
+    @brief convert the value @a val of another specialization into this null
+           value; @a val must be neither an object nor an array
+
+    Converting such a value never descends, so both ways of converting an
+    object or an array (@ref convert_structured) leave their elements of this
+    kind to the converting constructor, which leaves them to this.
+    */
+    template<typename BasicJsonType>
+    void convert_leaf(const BasicJsonType& val)
+    {
+        using other_boolean_t = typename BasicJsonType::boolean_t;
+        using other_number_float_t = typename BasicJsonType::number_float_t;
+        using other_number_integer_t = typename BasicJsonType::number_integer_t;
+        using other_number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+        using other_string_t = typename BasicJsonType::string_t;
+        using other_binary_t = typename BasicJsonType::binary_t;
+
+        switch (val.type())
+        {
+            case value_t::boolean:
+                JSONSerializer<other_boolean_t>::to_json(*this, val.template get<other_boolean_t>());
+                break;
+            case value_t::number_float:
+                JSONSerializer<other_number_float_t>::to_json(*this, val.template get<other_number_float_t>());
+                break;
+            case value_t::number_integer:
+                JSONSerializer<other_number_integer_t>::to_json(*this, val.template get<other_number_integer_t>());
+                break;
+            case value_t::number_unsigned:
+                JSONSerializer<other_number_unsigned_t>::to_json(*this, val.template get<other_number_unsigned_t>());
+                break;
+            case value_t::string:
+                JSONSerializer<other_string_t>::to_json(*this, val.template get_ref<const other_string_t&>());
+                break;
+            case value_t::binary:
+                JSONSerializer<other_binary_t>::to_json(*this, val.template get_ref<const other_binary_t&>());
+                break;
+            case value_t::null:
+                // m_data.m_type is already value_t::null
+                break;
+            case value_t::discarded:
+                m_data.m_type = value_t::discarded;
+                break;
+            case value_t::object: // LCOV_EXCL_LINE
+            case value_t::array:  // LCOV_EXCL_LINE
+            default:              // LCOV_EXCL_LINE
+                JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
+        }
+    }
+
+    /// scratch space for the converted elements of the arrays that
+    /// @ref convert_iteratively has yet to create
+    using convert_scratch_t = std::vector<basic_json, AllocatorType<basic_json>>;
+
+    /*!
+    @brief create the object or array @a val converted into this null value
+
+    Its converted elements are the last `val.size()` entries of @a elements (an
+    array) or of @a members (an object); they are moved into the container in
+    one go and then removed.
+    */
+    template<typename BasicJsonType>
+    void convert_level(const BasicJsonType& val, convert_scratch_t& elements, copy_scratch_t& members)
+    {
+        if (val.is_object())
+        {
+            const auto first = members.end() - static_cast<typename copy_scratch_t::difference_type>(val.size());
+            m_data.m_value.object = create<object_t>(std::make_move_iterator(first),
+                                    std::make_move_iterator(members.end()));
+            // only now that the object exists may this stop being a null value
+            m_data.m_type = value_t::object;
+            members.erase(first, members.end());
+        }
+        else
+        {
+            const auto first = elements.end() - static_cast<typename convert_scratch_t::difference_type>(val.size());
+            m_data.m_value.array = create<array_t>(std::make_move_iterator(first),
+                                                   std::make_move_iterator(elements.end()));
+            // only now that the array exists may this stop being a null value
+            m_data.m_type = value_t::array;
+            elements.erase(first, elements.end());
+        }
+
+        set_parents();
+    }
+
+    /*!
+    @brief convert the object or array @a val of another specialization into
+           this null value without recursing
+
+    The containers whose conversion has begun are kept on an explicit stack
+    rather than on the call stack. Unlike @ref copy_iteratively, this builds
+    every container from the bottom up: all its elements are converted first,
+    and the container is then created from them in one go, the way the range
+    constructor that converts the levels above the bound does. The two object
+    types need not enumerate their members in the same order, so the members
+    could not be paired up by position anyway, and building from a range keeps
+    what the range constructor does with keys that become equal on conversion.
+
+    Every value is complete before it is handed on, and a container gets its
+    type only once it exists, so whatever throws, every value left behind can
+    be destroyed.
+    */
+    template<typename BasicJsonType>
+    void convert_iteratively(const BasicJsonType& val)
+    {
+        using other_const_iterator = typename BasicJsonType::const_iterator;
+
+        // the containers whose conversion has begun, innermost last, each with
+        // its element to convert next
+        std::vector<std::pair<const BasicJsonType*, other_const_iterator>> pending;
+
+        // the converted elements of the pending arrays and the converted
+        // members of the pending objects, those of the innermost one last
+        convert_scratch_t elements;
+        copy_scratch_t members;
+
+        pending.emplace_back(&val, val.cbegin());
+
+        for (;;)
+        {
+            const BasicJsonType& container = *pending.back().first;
+            // a copy, as descending below can reallocate pending; the
+            // iterator kept in pending is only advanced through pending.back()
+            const other_const_iterator next = pending.back().second;
+
+            if (next != container.cend())
+            {
+                if (next->is_structured())
+                {
+                    // convert its elements first; next stays where it is until
+                    // the converted container is handed back to this one
+                    pending.emplace_back(&*next, next->cbegin());
+                    continue;
+                }
+
+                // the converting constructor does not descend into this value
+                if (container.is_object())
+                {
+                    members.emplace_back(next.key(), *next);
+                }
+                else
+                {
+                    elements.emplace_back(*next);
+                }
+                ++pending.back().second;
+                continue;
+            }
+
+            // all elements of the container are converted: create it
+            pending.pop_back();
+
+            if (pending.empty())
+            {
+                convert_level(container, elements, members);
+                return;
+            }
+
+            basic_json converted;
+            converted.convert_level(container, elements, members);
+#if JSON_DIAGNOSTIC_POSITIONS
+            converted.start_position = container.start_pos();
+            converted.end_position = container.end_pos();
+#endif
+
+            // hand it to the container it is an element of
+            if (pending.back().first->is_object())
+            {
+                members.emplace_back(pending.back().second.key(), std::move(converted));
+            }
+            else
+            {
+                elements.push_back(std::move(converted));
+            }
+            ++pending.back().second;
+        }
+    }
+
+    /*!
+    @brief convert the object or array @a val of another specialization into
+           this null value
+
+    Converting a container converts its elements, so a value nested deeply
+    enough used to exhaust the call stack. The descent is bounded here as in
+    @ref copy_structured: the first `detail::recursion_depth_limit()` levels
+    are converted by the containers' range constructors, just as they always were,
+    and anything below that is converted without the call stack by
+    @ref convert_iteratively.
+
+    @sa https://github.com/nlohmann/json/issues/5650
+    */
+    template<typename BasicJsonType>
+    void convert_structured(const BasicJsonType& val)
+    {
+        const nesting_depth_guard guard;
+
+        if (JSON_HEDLEY_LIKELY(guard.okay()))
+        {
+            // every element comes back to the converting constructor
+            if (val.is_object())
+            {
+                using other_object_t = typename BasicJsonType::object_t;
+                JSONSerializer<other_object_t>::to_json(*this, val.template get_ref<const other_object_t&>());
+            }
+            else
+            {
+                using other_array_t = typename BasicJsonType::array_t;
+                JSONSerializer<other_array_t>::to_json(*this, val.template get_ref<const other_array_t&>());
+            }
+            return;
+        }
+
+        convert_iteratively(val);
+    }
+
 
     /// the result of comparing two values, including values that cannot be
     /// ordered at all, such as a discarded value or a NaN
@@ -1596,7 +1812,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     template < typename CompatibleType,
                typename U = detail::uncvref_t<CompatibleType>,
                detail::enable_if_t <
-                   !detail::is_basic_json<U>::value && detail::is_compatible_type<basic_json_t, U>::value, int > = 0 >
+                   !detail::is_basic_json<U>::value && detail::is_compatible_type<basic_json_t, U>::value
+#if JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
+                   // see https://github.com/nlohmann/json/issues/2226
+                   && !detail::is_basic_json_reference_tuple<basic_json_t, U>::value
+#endif
+                   , int > = 0 >
     basic_json(CompatibleType && val) noexcept(noexcept( // NOLINT(bugprone-forwarding-reference-overload,bugprone-exception-escape)
                 JSONSerializer<U>::to_json(std::declval<basic_json_t&>(),
                                            std::forward<CompatibleType>(val))))
@@ -1617,49 +1838,13 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
           end_position(val.end_pos())
 #endif
     {
-        using other_boolean_t = typename BasicJsonType::boolean_t;
+        if (val.is_structured())
-        using other_number_float_t = typename BasicJsonType::number_float_t;
-        using other_number_integer_t = typename BasicJsonType::number_integer_t;
-        using other_number_unsigned_t = typename BasicJsonType::number_unsigned_t;
-        using other_string_t = typename BasicJsonType::string_t;
-        using other_object_t = typename BasicJsonType::object_t;
-        using other_array_t = typename BasicJsonType::array_t;
-        using other_binary_t = typename BasicJsonType::binary_t;
-
-        switch (val.type())
         {
-            case value_t::boolean:
+            convert_structured(val);
-                JSONSerializer<other_boolean_t>::to_json(*this, val.template get<other_boolean_t>());
+        }
-                break;
+        else
-            case value_t::number_float:
+        {
-                JSONSerializer<other_number_float_t>::to_json(*this, val.template get<other_number_float_t>());
+            convert_leaf(val);
-                break;
-            case value_t::number_integer:
-                JSONSerializer<other_number_integer_t>::to_json(*this, val.template get<other_number_integer_t>());
-                break;
-            case value_t::number_unsigned:
-                JSONSerializer<other_number_unsigned_t>::to_json(*this, val.template get<other_number_unsigned_t>());
-                break;
-            case value_t::string:
-                JSONSerializer<other_string_t>::to_json(*this, val.template get_ref<const other_string_t&>());
-                break;
-            case value_t::object:
-                JSONSerializer<other_object_t>::to_json(*this, val.template get_ref<const other_object_t&>());
-                break;
-            case value_t::array:
-                JSONSerializer<other_array_t>::to_json(*this, val.template get_ref<const other_array_t&>());
-                break;
-            case value_t::binary:
-                JSONSerializer<other_binary_t>::to_json(*this, val.template get_ref<const other_binary_t&>());
-                break;
-            case value_t::null:
-                *this = nullptr;
-                break;
-            case value_t::discarded:
-                m_data.m_type = value_t::discarded;
-                break;
-            default:            // LCOV_EXCL_LINE
-                JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
         }
         JSON_ASSERT(m_data.m_type == val.type());
 
@@ -5034,7 +5219,7 @@ 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, true>(std::move(ia), format).sax_parse(format, sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(sax, strict);
     }
 
     /// @brief generate SAX events (iterator pair, or iterator+sentinel pair for C++20 ranges support)
@@ -5051,7 +5236,7 @@ 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, true>(std::move(ia), format).sax_parse(format, sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(sax, strict);
     }
 
     /// @brief generate SAX events
@@ -5073,7 +5258,7 @@ 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, true>(std::move(ia), format).sax_parse(format, sax, strict);
+               : detail::binary_reader<basic_json, decltype(ia), SAX, true>(std::move(ia), format).sax_parse(sax, strict);
     }
 #ifndef JSON_NO_IO
     /// @brief deserialize from stream
@@ -5092,7 +5277,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_gtgt/
     friend std::istream& operator>>(std::istream& i, basic_json& j)
     {
-        parser(detail::input_adapter(i)).parse(false, j);
+        // parse into a temporary so that j is left unchanged if parsing fails
+        basic_json result;
+        parser(detail::input_adapter(i)).parse(false, result);
+        j = std::move(result);
         return i;
     }
 #endif  // JSON_NO_IO
@@ -5368,7 +5556,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(&sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5388,7 +5576,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(&sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5417,7 +5605,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::cbor).sax_parse(&sdp, strict, tag_handler)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5435,7 +5623,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5454,7 +5642,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5481,7 +5669,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(input_format_t::msgpack, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::msgpack).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5499,7 +5687,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5518,7 +5706,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5545,7 +5733,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(input_format_t::ubjson, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::ubjson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5563,7 +5751,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5582,7 +5770,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5600,7 +5788,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5619,7 +5807,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bon8).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5637,7 +5825,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5656,7 +5844,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         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::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }
@@ -5683,7 +5871,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         auto ia = i.get();
         detail::json_sax_dom_parser<basic_json, decltype(ia)> sdp(result, allow_exceptions);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
-        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(input_format_t::bson, &sdp, strict)) // cppcheck-suppress[accessMoved]
+        if (!binary_reader<decltype(ia)>(std::move(ia), input_format_t::bson).sax_parse(&sdp, strict)) // cppcheck-suppress[accessMoved]
         {
             result = value_t::discarded;
         }

tests/src/unit-allocator.cpp

@@ -479,6 +479,77 @@ TEST_CASE("deep copy uses the provided allocator")
     CHECK(copy == j);
 }
 
+namespace
+{
+// the number of constructions countdown_allocator lets happen, including the
+// one that fails; 0 means none ever fails
+std::size_t constructions_until_failure = 0;
+
+template<class T>
+struct countdown_allocator : std::allocator<T>
+{
+    using std::allocator<T>::allocator;
+
+    template<class U, class... Args>
+    void construct(U* p, Args&& ... args)
+    {
+        if (constructions_until_failure != 0 && --constructions_until_failure == 0)
+        {
+            throw std::bad_alloc();
+        }
+
+        ::new (static_cast<void*>(p)) U(std::forward<Args>(args)...);
+    }
+
+    template <class U>
+    struct rebind
+    {
+        using other = countdown_allocator<U>;
+    };
+};
+} // namespace
+
+TEST_CASE("converting a deeply nested value from another specialization fails cleanly (#5650)")
+{
+    using countdown_json = nlohmann::basic_json<std::map,
+          std::vector,
+          std::string,
+          bool,
+          std::int64_t,
+          std::uint64_t,
+          double,
+          countdown_allocator>;
+
+    // deeper than the 128 levels the converting constructor descends into, so
+    // that failures land on both sides of the bound - or, built with
+    // JSON_NO_THREAD_LOCAL, all in the iterative conversion
+    json j = {1, "two", {{"three", 3}}};
+    for (std::size_t i = 0; i < 150; ++i)
+    {
+        j = json{{"a", json::array({j, "sibling"})}};
+    }
+
+    // Fail every construction in turn. Each failure has to reach the caller,
+    // and everything built until then has to be destroyed cleanly.
+    std::size_t failures = 0;
+    for (std::size_t n = 1;; ++n)
+    {
+        constructions_until_failure = n;
+        try
+        {
+            const countdown_json converted = j;
+            constructions_until_failure = 0;
+            CHECK(converted.dump() == j.dump());
+            break;
+        }
+        catch (const std::bad_alloc&)
+        {
+            ++failures;
+        }
+    }
+    CHECK(failures > 0);
+}
+
 namespace
 {
 template<class T>

tests/src/unit-alt-string.cpp

@@ -352,6 +352,41 @@ TEST_CASE("alternative string type")
         CHECK(j2.flatten().unflatten() == j2);
     }
 
+    SECTION("contains(json_pointer)")
+    {
+        // contains(json_pointer) must compile and work with a string_t that has
+        // no c_str() and no comparison with const char* (see #5666)
+        auto j = alt_json::parse(R"({"foo": ["bar", "baz"]})");
+
+        // present: object key and array indices
+        CHECK(j.contains(alt_json::json_pointer("/foo")));
+        CHECK(j.contains(alt_json::json_pointer("/foo/0")));
+        CHECK(j.contains(alt_json::json_pointer("/foo/1")));
+
+        // missing: absent object key and out-of-range array index
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/bar")));
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/2")));
+
+        // "-" always fails the range check
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/-")));
+
+        // an array index must not have a leading zero
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/01")));
+
+        // a reference token that is not a number
+        CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/bar")));
+    }
+
+    SECTION("operator/(std::size_t)")
+    {
+        // json_pointer::operator/=(std::size_t) must compile without string_t
+        // being constructible from std::string (see #5666)
+        auto j = alt_json::parse(R"({"foo": ["bar", "baz"]})");
+
+        CHECK(j.at(alt_json::json_pointer("/foo") / std::size_t(0)) == j["foo"][0]);
+        CHECK(j.at(alt_json::json_pointer("/foo") / std::size_t(1)) == j["foo"][1]);
+    }
+
     SECTION("patch")
     {
         alt_json const patch1 = alt_json::parse(R"([{ "op": "add", "path": "/a/b", "value": [ "foo", "bar" ] }])");

tests/src/unit-bjdata.cpp

@@ -210,15 +210,42 @@ TEST_CASE_TEMPLATE_INVOKE(value_in_range_of_test, \
 
 TEST_CASE("BJData")
 {
-    SECTION("binary_reader BJData LUT arrays are sorted")
+    SECTION("binary_reader BJData lookup tables")
     {
         std::vector<std::uint8_t> const data;
         auto ia = nlohmann::detail::input_adapter(data);
         // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
         nlohmann::detail::binary_reader<json, decltype(ia)> const br{std::move(ia), json::input_format_t::bjdata};
 
-        CHECK(std::is_sorted(br.bjd_optimized_type_markers.begin(), br.bjd_optimized_type_markers.end()));
+        // the excluded optimized-type markers must match binary_writer's
-        CHECK(std::is_sorted(br.bjd_types_map.begin(), br.bjd_types_map.end()));
+        // is_bjdata_excluded_type_marker(), which encodes the same 8 markers
+        for (const char marker :
+                {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'
+                })
+        {
+            CHECK(br.is_bjd_excluded_optimized_type(marker));
+        }
+        for (const char marker :
+                {'U', 'i', 'u', 'I', 'm', 'l', 'M', 'L', 'd', 'D', 'C', 'B', 'x'
+                })
+        {
+            CHECK(!br.is_bjd_excluded_optimized_type(marker));
+        }
+
+        // every dtype marker must round-trip to its ND-array type name
+        const std::vector<std::pair<char, std::string>> types
+        {
+            {'B', "byte"}, {'C', "char"}, {'D', "double"}, {'I', "int16"},
+            {'L', "int64"}, {'M', "uint64"}, {'U', "uint8"}, {'d', "single"},
+            {'i', "int8"}, {'l', "int32"}, {'m', "uint32"}, {'u', "uint16"}
+        };
+        for (const auto& type : types)
+        {
+            const char* name = br.bjd_type_name(type.first);
+            REQUIRE(name != nullptr);
+            CHECK(std::string(name) == type.second);
+        }
+        CHECK(br.bjd_type_name('x') == nullptr);
     }
 
     SECTION("individual values")

tests/src/unit-diagnostic-positions.cpp

@@ -141,6 +141,58 @@ TEST_CASE("Better diagnostics with positions")
         check_objects(300);
     }
 
+    SECTION("converting keeps the positions of nested values (#5650)")
+    {
+        // Values nested deeper than the converting constructor's descent bound
+        // are converted without the call stack, on a path that has to carry the
+        // positions of every value over itself. Objects and arrays take turns,
+        // and the innermost value is null, which used to lose its positions.
+        const auto check_conversion = [](std::size_t depth)
+        {
+            CAPTURE(depth)
+
+            std::string text;
+            std::string closing;
+            for (std::size_t i = 0; i < depth; ++i)
+            {
+                text += (i % 2 == 0) ? "[12, " : R"({"b":1, "a":)";
+                closing += (i % 2 == 0) ? ']' : '}';
+            }
+            text += "null";
+            text.append(closing.rbegin(), closing.rend());
+
+            const json original = json::parse(text);
+            const nlohmann::ordered_json converted = original;
+
+            const json* o = &original;
+            const nlohmann::ordered_json* c = &converted;
+            for (std::size_t level = 0; level <= depth; ++level)
+            {
+                CAPTURE(level)
+                REQUIRE(c->start_pos() == o->start_pos());
+                REQUIRE(c->end_pos() == o->end_pos());
+
+                if (level < depth)
+                {
+                    // the number beside the value nested next
+                    const json& o_number = o->is_object() ? o->at("b") : o->at(0);
+                    const nlohmann::ordered_json& c_number = c->is_object() ? c->at("b") : c->at(0);
+                    REQUIRE(c_number.start_pos() == o_number.start_pos());
+                    REQUIRE(c_number.end_pos() == o_number.end_pos());
+
+                    o = o->is_object() ? &o->at("a") : &o->at(1);
+                    c = c->is_object() ? &c->at("a") : &c->at(1);
+                }
+            }
+        };
+
+        check_conversion(1);
+        check_conversion(127);
+        check_conversion(128);
+        check_conversion(129);
+        check_conversion(300);
+    }
+
     SECTION("JSON patch add to primitive parent (#4292)")
     {
         // the JSON Patch "add" target /foo/bar/baz has a string parent

tests/src/unit-diagnostics.cpp

@@ -19,6 +19,7 @@ using nlohmann::json;
 
 #include <map>
 #include <unordered_map>
+#include <sstream>
 
 TEST_CASE("Better diagnostics")
 {
@@ -340,6 +341,36 @@ TEST_CASE("Regression tests for extended diagnostics")
         }
     }
 
+    SECTION("Regression test for issue #5650 - converting keeps the parents of nested values")
+    {
+        // A value nested deeper than the converting constructor's descent bound
+        // is converted without the call stack. Every container that path creates
+        // has to have the parents of its children set, or the JSON Pointer in the
+        // diagnostic is cut short. Objects and arrays take turns.
+        const std::size_t pairs = 150;
+
+        json j = "not a number";
+        std::string pointer;
+        for (std::size_t i = 0; i < pairs; ++i)
+        {
+            j = json{{"a", json::array({j})}};
+            pointer += "/a/0";
+        }
+
+        const nlohmann::ordered_json converted = j;
+
+        const nlohmann::ordered_json* inner = &converted;
+        for (std::size_t i = 0; i < pairs; ++i)
+        {
+            inner = &inner->at("a").at(0);
+        }
+
+        std::string const expected = "[json.exception.type_error.302] (" + pointer + ") type must be number, but is string";
+        int i = 0;
+        CHECK_THROWS_WITH_AS(i = inner->get<int>(), expected.c_str(), nlohmann::ordered_json::type_error);
+        CHECK(i == 0);
+    }
+
     SECTION("Regression test for issue #5668 - wrong path for std::map/unordered_map with non-string keys")
     {
         // a map with non-string keys is read from an array of [key, value] arrays;
@@ -492,6 +523,21 @@ TEST_CASE("Regression tests for extended diagnostics")
             CHECK(copy == j);
         }
     }
+
+    SECTION("Regression test for issue #5652 - operator>> leaves a partial value in its target on a parse error")
+    {
+        json j = "old value";
+        std::istringstream is("[1, x");
+        CHECK_THROWS_WITH_AS(is >> j, "[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - invalid literal; last read: '1, x'", json::parse_error);
+
+        // j must be left unchanged, as json::parse() guarantees for its result
+        CHECK(j == "old value");
+
+        // copying j must not trigger assert_invariant(): a failed parse must
+        // not leave array/object elements without a parent pointer
+        json const copy = j; // NOLINT(performance-unnecessary-copy-initialization)
+        CHECK(copy == j);
+    }
 }
 
 TEST_CASE("Better diagnostics past the descent bound of update() and merge_patch()")

tests/src/unit-disable-tuple-reference-conversion.cpp

@@ -0,0 +1,93 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#include "doctest_compatibility.h"
+
+// This file tests the opt-in JSON_DISABLE_TUPLE_REFERENCE_CONVERSION, so it
+// defines the macro itself rather than relying on a -D flag, and runs in every
+// build.
+#ifdef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
+    #undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
+#endif
+
+#define JSON_DISABLE_TUPLE_REFERENCE_CONVERSION 1
+
+#include <nlohmann/json.hpp>
+using nlohmann::json;
+using nlohmann::ordered_json;
+
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+// clang before 4 and GCC before 5 cannot create a std::tuple of basic_json
+// references at all, with or without JSON_DISABLE_TUPLE_REFERENCE_CONVERSION:
+// the tuple constructors make them instantiate basic_json's conversion operator
+// for libstdc++'s internal tuple bases, which fails hard
+#if (defined(__clang__) && __clang_major__ < 4) || (!defined(__clang__) && defined(__GNUC__) && __GNUC__ < 5)
+    #define SKIP_TESTS_FOR_JSON_REFERENCE_TUPLES
+#endif
+
+TEST_CASE("JSON_DISABLE_TUPLE_REFERENCE_CONVERSION")
+{
+    SECTION("json is not constructible from a one-element tuple of a json reference")
+    {
+        CHECK_FALSE(std::is_constructible<json, std::tuple<json&>>::value);
+        CHECK_FALSE(std::is_constructible<json, std::tuple<const json&>>::value);
+        CHECK_FALSE(std::is_constructible < json, std::tuple < json && >>::value);
+        CHECK_FALSE(std::is_constructible<json, const std::tuple<json&>&>::value);
+        CHECK_FALSE(std::is_constructible<ordered_json, std::tuple<ordered_json&>>::value);
+    }
+
+#ifndef SKIP_TESTS_FOR_JSON_REFERENCE_TUPLES
+    SECTION("issue #2226 - tuple<const json&> from tuple<json&> keeps the reference")
+    {
+        json j = true;
+        const std::tuple<const json&> tup(std::forward_as_tuple(j));
+        CHECK(&std::get<0>(tup) == &j);
+    }
+
+    SECTION("tuple<json> from tuple<json&> copies the element")
+    {
+        const json j = {{"key", "value"}};
+        const std::tuple<json> t1(std::forward_as_tuple(j));
+        CHECK(std::get<0>(t1) == j);
+
+        json j2 = "text";
+        const std::tuple<json> t2(std::forward_as_tuple(std::move(j2)));
+        CHECK(std::get<0>(t2) == "text");
+    }
+#endif
+
+    SECTION("other tuple conversions are not affected")
+    {
+        const json j = true;
+
+        // one-element tuple holding a json value
+        CHECK(json(std::make_tuple(j)) == json::array({true}));
+
+        // tuples with more than one element, even when holding references
+        int i = 1;
+#ifndef SKIP_TESTS_FOR_JSON_REFERENCE_TUPLES
+        CHECK(json(std::forward_as_tuple(i, j)) == json::array({1, true}));
+        CHECK(json(std::forward_as_tuple(j, j)) == json::array({true, true}));
+#endif
+
+        // one-element tuples holding references to other types
+        std::string s = "text";
+        CHECK(json(std::forward_as_tuple(s)) == json::array({"text"}));
+        CHECK(json(std::forward_as_tuple(i)) == json::array({1}));
+
+#ifndef SKIP_TESTS_FOR_JSON_REFERENCE_TUPLES
+        // a reference to a different basic_json specialization
+        ordered_json oj = true;
+        CHECK(json(std::forward_as_tuple(oj)) == json::array({true}));
+#endif
+    }
+}

tests/src/unit-large_json.cpp

@@ -13,6 +13,7 @@ using nlohmann::json;
 
 #include <algorithm>
 #include <string>
+#include <vector>
 
 TEST_CASE("tests on very large JSONs")
 {
@@ -53,6 +54,24 @@ const json* innermost_value(const json& j, std::size_t& depth)
     return current;
 }
 
+// The text of a value nested depth levels deep around the number 0. Level i is
+// an array if pattern[i % pattern.size()] is '[', and otherwise an object with
+// the single member "a", which every object type enumerates in the same order.
+std::string nested_text(std::size_t depth, const std::string& pattern)
+{
+    std::string text;
+    std::string closing;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        const bool array = pattern[i % pattern.size()] == '[';
+        text += array ? "[" : "{\"a\":";
+        closing += array ? ']' : '}';
+    }
+    text += '0';
+    text.append(closing.rbegin(), closing.rend());
+    return text;
+}
+
 } // namespace
 
 TEST_CASE("tests on deeply nested JSONs")
@@ -224,5 +243,114 @@ TEST_CASE("tests on deeply nested JSONs")
             CHECK(*innermost_value(j, unused) == 0);
         }
     }
+
+    SECTION("issue #5650 - stack overflow converting between specializations")
+    {
+        const std::vector<std::string> patterns = {"[", "{", "[{"};
+
+        SECTION("json to ordered_json")
+        {
+            for (const auto& pattern : patterns)
+            {
+                CAPTURE(pattern);
+                const std::string text = nested_text(depth, pattern);
+                const json j = json::parse(text);
+
+                const nlohmann::ordered_json converted = j;
+                CHECK(converted.dump() == text);
+            }
+        }
+
+        SECTION("ordered_json to json")
+        {
+            for (const auto& pattern : patterns)
+            {
+                CAPTURE(pattern);
+                const std::string text = nested_text(depth, pattern);
+                const nlohmann::ordered_json o = nlohmann::ordered_json::parse(text);
+
+                const json converted = o;
+                CHECK(converted.dump() == text);
+            }
+        }
+
+        SECTION("get<ordered_json>()")
+        {
+            for (const auto& pattern : patterns)
+            {
+                CAPTURE(pattern);
+                const std::string text = nested_text(depth, pattern);
+                const json j = json::parse(text);
+
+                CHECK(j.get<nlohmann::ordered_json>().dump() == text);
+            }
+        }
+
+        SECTION("depths around the bound of the recursive descent")
+        {
+            for (std::size_t d = 1; d <= 300; ++d)
+            {
+                CAPTURE(d);
+                for (const auto& pattern : patterns)
+                {
+                    CAPTURE(pattern);
+                    const std::string text = nested_text(d, pattern);
+                    const json j = json::parse(text);
+
+                    const nlohmann::ordered_json converted = j;
+                    CHECK(converted.dump() == text);
+                    const json back = converted;
+                    CHECK(back.dump() == text);
+                }
+            }
+        }
+
+        SECTION("values below the bound are converted as values above it")
+        {
+            // Bury a value below the bound, where it is converted without the
+            // call stack, and compare it with the same value converted on its
+            // own by the containers' range constructors. Its objects have
+            // members that the two object types enumerate in different orders.
+            const auto bury = [](nlohmann::ordered_json value)
+            {
+                for (std::size_t i = 0; i < 200; ++i)
+                {
+                    value = nlohmann::ordered_json::array({std::move(value)});
+                }
+                return value;
+            };
+            const auto dig = [](const json & value)
+            {
+                const json* current = &value;
+                for (std::size_t i = 0; i < 200; ++i)
+                {
+                    current = &current->at(0);
+                }
+                return current;
+            };
+
+            nlohmann::ordered_json value = nlohmann::ordered_json::object();
+            value["z"] = {1, -2, 3U, 4.5, true, nullptr, "six", nlohmann::ordered_json::binary({7, 8}, 9),
+                          nlohmann::ordered_json::binary({10}), nlohmann::ordered_json::array(), nlohmann::ordered_json::object()
+                         };
+            value["y"] = {{"x", {{"w", 1}, {"v", 2}}}, {"u", {3, {{"t", 4}, {"s", 5}}}}};
+            value["r"] = nlohmann::ordered_json::array({nlohmann::ordered_json(nlohmann::ordered_json::value_t::discarded)});
+
+            const json converted_above = value;
+            const json buried = bury(value);
+            const json& converted_below = *dig(buried);
+
+            CHECK(converted_below.dump() == converted_above.dump());
+            CHECK(converted_below.at("z").at(7).get_binary().subtype() == 9);
+            CHECK_FALSE(converted_below.at("z").at(8).get_binary().has_subtype());
+            CHECK(converted_below.at("r").at(0).is_discarded());
+
+            // a discarded value is never equal to anything, so compare the rest
+            value.erase("r");
+            const json without_discarded_above = value;
+            const json without_discarded_buried = bury(value);
+            CHECK(*dig(without_discarded_buried) == without_discarded_above);
+        }
+    }
 }
 

tests/src/unit-regression2.cpp

@@ -18,6 +18,19 @@
 // for some reason including this after the json header leads to linker errors with VS 2017...
 #include <locale>
 
+// skip tests if JSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1 (#2226)
+#if defined(JSON_DISABLE_TUPLE_REFERENCE_CONVERSION) && (JSON_DISABLE_TUPLE_REFERENCE_CONVERSION == 1)
+    #define SKIP_TESTS_FOR_TUPLE_REFERENCE_CONVERSION
+#endif
+
+// clang before 4 and GCC before 5 cannot create a std::tuple of basic_json
+// references at all, with or without JSON_DISABLE_TUPLE_REFERENCE_CONVERSION:
+// the tuple constructors make them instantiate basic_json's conversion operator
+// for libstdc++'s internal tuple bases, which fails hard
+#if (defined(__clang__) && __clang_major__ < 4) || (!defined(__clang__) && defined(__GNUC__) && __GNUC__ < 5)
+    #define SKIP_TESTS_FOR_JSON_REFERENCE_TUPLES
+#endif
+
 #define JSON_TESTS_PRIVATE
 #include <nlohmann/json.hpp>
 using json = nlohmann::json;
@@ -28,6 +41,7 @@ using ordered_json = nlohmann::ordered_json;
 
 #include <cstdio>
 #include <list>
+#include <tuple>
 #include <type_traits>
 #include <utility>
 
@@ -542,6 +556,20 @@ TEST_CASE("regression tests 2")
                       )));
     }
 
+#ifndef SKIP_TESTS_FOR_TUPLE_REFERENCE_CONVERSION
+    SECTION("issue #2226 - std::tuple dangling reference - implicit conversion")
+    {
+        // by default, a one-element tuple holding a json reference converts to
+        // a one-element array; JSON_DISABLE_TUPLE_REFERENCE_CONVERSION removes
+        // this conversion (see unit-disable-tuple-reference-conversion.cpp)
+        const json j = true;
+        CHECK(std::is_constructible<json, std::tuple<const json&>>::value);
+#ifndef SKIP_TESTS_FOR_JSON_REFERENCE_TUPLES
+        CHECK(json(std::forward_as_tuple(j)) == json::array({true}));
+#endif
+    }
+#endif
+
     SECTION("PR #2181 - regression bug with lvalue")
     {
         // see https://github.com/nlohmann/json/pull/2181#issuecomment-653326060

tests/src/unit-ubjson.cpp

@@ -3033,3 +3033,224 @@ TEST_CASE("UBJSON optimized array of unsigned integers beyond int64")
     CHECK(json::to_ubjson(j, true, true) == expected);
     CHECK(json::from_ubjson(expected) == j);
 }
+
+namespace
+{
+// the bytes that follow the marker of an integer: the value in the width of
+// the marker (big endian for UBJSON, little endian for BJData), or, for a
+// high-precision number, the length and the decimal digits
+std::vector<std::uint8_t> integer_payload(const char marker, const json& value, const bool little_endian)
+{
+    std::size_t width = 0;
+    switch (marker)
+    {
+        case 'i':
+        case 'U':
+            width = 1;
+            break;
+        case 'I':
+        case 'u':
+            width = 2;
+            break;
+        case 'l':
+        case 'm':
+            width = 4;
+            break;
+        case 'L':
+        case 'M':
+            width = 8;
+            break;
+        default:
+        {
+            const std::string digits = value.dump();
+            std::vector<std::uint8_t> result = {'i', static_cast<std::uint8_t>(digits.size())};
+            for (const char c : digits)
+            {
+                result.push_back(static_cast<std::uint8_t>(c));
+            }
+            return result;
+        }
+    }
+
+    const std::uint64_t bits = value.is_number_unsigned()
+                               ? value.get<std::uint64_t>()
+                               : static_cast<std::uint64_t>(value.get<std::int64_t>());
+    std::vector<std::uint8_t> result(width);
+    for (std::size_t i = 0; i < width; ++i)
+    {
+        result[little_endian ? i : width - 1 - i] = static_cast<std::uint8_t>(bits >> (8 * i));
+    }
+    return result;
+}
+
+json i64(const std::int64_t v)
+{
+    return v;
+}
+
+json u64(const std::uint64_t v)
+{
+    return v;
+}
+} // namespace
+
+TEST_CASE("UBJSON and BJData integer markers at every range edge")
+{
+    // An optimized container announces the marker of its values after `$` and
+    // then writes every value without a marker, so the marker the writer
+    // announces and the width it writes must match for every value. This
+    // checks both for the values around each edge of the integer types, as
+    // scalars and as the values of optimized arrays and objects.
+    struct integer_case
+    {
+        json value;
+        char ubjson; // expected UBJSON marker
+        char bjdata; // expected BJData marker
+    };
+
+    const std::int64_t int64_min = (std::numeric_limits<std::int64_t>::min)();
+    const std::int64_t int64_max = (std::numeric_limits<std::int64_t>::max)();
+    const std::uint64_t uint64_max = (std::numeric_limits<std::uint64_t>::max)();
+
+    const std::vector<integer_case> cases =
+    {
+        // int8
+        {i64(-129), 'I', 'I'},
+        {i64(-128), 'i', 'i'},
+        {i64(-127), 'i', 'i'},
+        {i64(-1), 'i', 'i'},
+        {i64(0), 'i', 'i'},
+        {u64(0), 'i', 'i'},
+        {i64(126), 'i', 'i'},
+        {i64(127), 'i', 'i'},
+        {u64(127), 'i', 'i'},
+        {i64(128), 'U', 'U'},
+        {u64(128), 'U', 'U'},
+        // uint8
+        {i64(254), 'U', 'U'},
+        {i64(255), 'U', 'U'},
+        {u64(255), 'U', 'U'},
+        {i64(256), 'I', 'I'},
+        {u64(256), 'I', 'I'},
+        // int16
+        {i64(-32769), 'l', 'l'},
+        {i64(-32768), 'I', 'I'},
+        {i64(-32767), 'I', 'I'},
+        {i64(32766), 'I', 'I'},
+        {i64(32767), 'I', 'I'},
+        {u64(32767), 'I', 'I'},
+        {i64(32768), 'l', 'u'},
+        {u64(32768), 'l', 'u'},
+        // uint16 (BJData only)
+        {i64(65534), 'l', 'u'},
+        {i64(65535), 'l', 'u'},
+        {u64(65535), 'l', 'u'},
+        {i64(65536), 'l', 'l'},
+        {u64(65536), 'l', 'l'},
+        // int32
+        {i64(-2147483649LL), 'L', 'L'},
+        {i64(-2147483648LL), 'l', 'l'},
+        {i64(-2147483647LL), 'l', 'l'},
+        {i64(2147483646LL), 'l', 'l'},
+        {i64(2147483647LL), 'l', 'l'},
+        {u64(2147483647ULL), 'l', 'l'},
+        {i64(2147483648LL), 'L', 'm'},
+        {u64(2147483648ULL), 'L', 'm'},
+        // uint32 (BJData only)
+        {i64(4294967294LL), 'L', 'm'},
+        {i64(4294967295LL), 'L', 'm'},
+        {u64(4294967295ULL), 'L', 'm'},
+        {i64(4294967296LL), 'L', 'L'},
+        {u64(4294967296ULL), 'L', 'L'},
+        // int64
+        {i64(int64_min), 'L', 'L'},
+        {i64(int64_min + 1), 'L', 'L'},
+        {i64(int64_max - 1), 'L', 'L'},
+        {i64(int64_max), 'L', 'L'},
+        {u64(static_cast<std::uint64_t>(int64_max)), 'L', 'L'},
+        // uint64 (BJData only; UBJSON writes a high-precision number)
+        {u64(static_cast<std::uint64_t>(int64_max) + 1), 'H', 'M'},
+        {u64(uint64_max - 1), 'H', 'M'},
+        {u64(uint64_max), 'H', 'M'},
+    };
+
+    for (const auto& c : cases)
+    {
+        for (const bool bjdata :
+                {
+                    false, true
+                })
+        {
+            const char marker = bjdata ? c.bjdata : c.ubjson;
+            const std::vector<std::uint8_t> payload = integer_payload(marker, c.value, bjdata);
+            const auto to_binary = [bjdata](const json & j, const bool use_size, const bool use_type)
+            {
+                return bjdata ? json::to_bjdata(j, use_size, use_type) : json::to_ubjson(j, use_size, use_type);
+            };
+            const auto from_binary = [bjdata](const std::vector<std::uint8_t>& v)
+            {
+                return bjdata ? json::from_bjdata(v) : json::from_ubjson(v);
+            };
+            INFO("value = " << c.value.dump() << (c.value.is_number_unsigned() ? " (unsigned)" : "") << ", format = " << (bjdata ? "BJData" : "UBJSON"));
+
+            // scalar
+            std::vector<std::uint8_t> expected = {static_cast<std::uint8_t>(marker)};
+            expected.insert(expected.end(), payload.begin(), payload.end());
+            for (const bool use_size :
+                    {
+                        false, true
+                    })
+            {
+                CHECK(to_binary(c.value, use_size, false) == expected);
+            }
+            CHECK(from_binary(expected) == c.value);
+
+            const json arr = {c.value, c.value, c.value};
+
+            // array without count or type: every value has its marker
+            expected = {'['};
+            for (int i = 0; i < 3; ++i)
+            {
+                expected.push_back(static_cast<std::uint8_t>(marker));
+                expected.insert(expected.end(), payload.begin(), payload.end());
+            }
+            expected.push_back(']');
+            CHECK(to_binary(arr, false, false) == expected);
+            CHECK(from_binary(expected) == arr);
+
+            // array with count: every value has its marker
+            expected = {'[', '#', 'i', 3};
+            for (int i = 0; i < 3; ++i)
+            {
+                expected.push_back(static_cast<std::uint8_t>(marker));
+                expected.insert(expected.end(), payload.begin(), payload.end());
+            }
+            CHECK(to_binary(arr, true, false) == expected);
+            CHECK(from_binary(expected) == arr);
+
+            // array with type and count: the marker once, then the payloads
+            expected = {'[', '$', static_cast<std::uint8_t>(marker), '#', 'i', 3};
+            for (int i = 0; i < 3; ++i)
+            {
+                expected.insert(expected.end(), payload.begin(), payload.end());
+            }
+            CHECK(to_binary(arr, true, true) == expected);
+            CHECK(from_binary(expected) == arr);
+
+            // object with type and count: the marker once, then key and payload
+            const json obj = {{"a", c.value}, {"b", c.value}};
+            expected = {'{', '$', static_cast<std::uint8_t>(marker), '#', 'i', 2};
+            for (const char key :
+                    {'a', 'b'
+                    })
+            {
+                expected.push_back('i');
+                expected.push_back(1);
+                expected.push_back(static_cast<std::uint8_t>(key));
+                expected.insert(expected.end(), payload.begin(), payload.end());
+            }
+            CHECK(to_binary(obj, true, true) == expected);
+            CHECK(from_binary(expected) == obj);
+        }
+    }
+}

tools/amalgamate/README.md

@@ -1,8 +1,8 @@
 # amalgamate.py - Amalgamate C source and header files
 
-Origin: https://bitbucket.org/erikedlund/amalgamate
+Origin: https://github.com/edlund/amalgamate (formerly hosted at
-
+https://bitbucket.org/erikedlund/amalgamate, which no longer exists; see
-Mirror: https://github.com/edlund/amalgamate
+`CHANGES.md` for the upstream commit this copy is based on)
 
 `amalgamate.py` aims to make it easy to use SQLite-style C source and header
 amalgamation in projects.
@@ -41,21 +41,22 @@ results.
 
 ## Installing amalgamate.py
 
-Python v.2.7.0 or higher is required.
+Python 3 is required.
 
-`amalgamate.py` can be tested and installed using the following commands:
+In this repository, `amalgamate.py` is not installed separately; it is run in
-
+place through `make amalgamate`, which calls it once for `json.hpp` and once
-        ./test.sh && sudo -k cp ./amalgamate.py /usr/local/bin/
+for `json_fwd.hpp` (see the root `Makefile`).
 
 ## Using amalgamate.py
 
-        amalgamate.py [-v] -c path/to/config.json -s path/to/source/dir \
+        amalgamate.py -c path/to/config.json -s path/to/source/dir \
-                [-p path/to/prologue.(c|h)]
+                [-p path/to/prologue.(c|h)] [--verbose=yes|no]
 
  * The `-c, --config` option should specify the path to a JSON config file which
    lists the source files, include paths and where to write the resulting
-   amalgamation. Have a look at `test/source.c.json` and `test/include.h.json`
+   amalgamation. `config_json.json` and `config_json_fwd.json` in this
-   to see two examples.
+   directory are the configs used for `json.hpp` and `json_fwd.hpp`; each
+   sets `target`, `sources` and `include_paths`.
 
    The optional `external` list names include paths that are kept as `#include`
    directives instead of being inlined, e.g. `["nlohmann/json.hpp"]` for a header
@@ -68,3 +69,6 @@ Python v.2.7.0 or higher is required.
  * The `-p, --prologue` option should specify the path to a file which will be
    added to the beginning of the amalgamation. It is optional.
 
+ * The `-v, --verbose` option takes `yes` or `no` (for example
+   `--verbose=yes`, as used by the Makefile). It is optional.
+

tools/generate_natvis/README.md

@@ -2,8 +2,26 @@
 
 Generate the Natvis debugger visualization file for all supported namespace combinations.
 
+The ABI tag list and the library version are parsed from
+`include/nlohmann/detail/abi_macros.hpp`, so this script must be re-run (via
+`make natvis`) whenever an `NLOHMANN_JSON_ABI_TAG_*` macro is added to that
+file or the library version is bumped — otherwise the committed
+`nlohmann_json.natvis` drifts from the header it visualizes, and
+`make check-amalgamation` fails.
+
 ## Usage
 
 ```shell
-./generate_natvis.py --version X.Y.Z output_directory/
+make natvis
 ```
+
+or, equivalently:
+
+```shell
+./generate_natvis.py [--version X.Y.Z] [repository_root/]
+```
+
+`--version` and the output/repository-root directory both default to values
+derived from this script's own location, so they only need to be given
+explicitly when generating a Natvis file for a different checkout or a
+version other than the one in `abi_macros.hpp`.

tools/generate_natvis/generate_natvis.py

@@ -7,21 +7,75 @@ import os
 import re
 import sys
 
+# Directory of the repository, assuming this script stays at
+# tools/generate_natvis/generate_natvis.py. Used only as the default value
+# for the "output" argument below.
+REPO_ROOT = os.path.normpath(os.path.join(sys.path[0], '..', '..'))
+
+
 def semver(v):
     if not re.fullmatch(r'\d+\.\d+\.\d+', v):
         raise ValueError
     return v
 
+
+def abi_info(repo_root):
+    """Derive the ABI tag list (in NLOHMANN_JSON_ABI_TAGS_CONCAT order) and the
+    library version from <repo_root>/include/nlohmann/detail/abi_macros.hpp,
+    so this script cannot drift from the header it visualizes."""
+    abi_macros_hpp = os.path.join(repo_root, 'include', 'nlohmann', 'detail', 'abi_macros.hpp')
+    with open(abi_macros_hpp) as f:
+        content = f.read()
+
+    # find the NLOHMANN_JSON_ABI_TAGS_CONCAT(...) invocation that lists the
+    # NLOHMANN_JSON_ABI_TAG_* identifiers in order (not its own #define, which
+    # only names its formal parameters a, b, c, ...)
+    tag_idents = None
+    for args in re.findall(r'NLOHMANN_JSON_ABI_TAGS_CONCAT\(\s*(.*?)\)', content, re.S):
+        idents = re.findall(r'NLOHMANN_JSON_ABI_TAG_\w+', args)
+        if idents:
+            tag_idents = idents
+            break
+    if not tag_idents:
+        raise ValueError(f'could not find NLOHMANN_JSON_ABI_TAGS_CONCAT(...) in {abi_macros_hpp}')
+
+    abi_tags = []
+    for ident in tag_idents:
+        # each tag is #define'd to its suffix (e.g. _diag) when the matching
+        # JSON_* option is enabled, and to nothing in the #else branch; only
+        # the non-empty definition matches here
+        match = re.search(r'#define\s+' + re.escape(ident) + r'\s+(_\w+)\s*\n', content)
+        if not match:
+            raise ValueError(f'could not find a non-empty #define for {ident} in {abi_macros_hpp}')
+        abi_tags.append(match.group(1))
+
+    version = {}
+    for part in ('MAJOR', 'MINOR', 'PATCH'):
+        match = re.search(r'#define\s+NLOHMANN_JSON_VERSION_' + part + r'\s+(\d+)', content)
+        if not match:
+            raise ValueError(f'could not find NLOHMANN_JSON_VERSION_{part} in {abi_macros_hpp}')
+        version[part] = match.group(1)
+
+    return abi_tags, '{MAJOR}.{MINOR}.{PATCH}'.format(**version)
+
+
 if __name__ == '__main__':
     parser = argparse.ArgumentParser()
-    parser.add_argument('--version', required=True, type=semver, help='Library version number')
+    parser.add_argument('--version', type=semver,
-    parser.add_argument('output', help='Output directory for nlohmann_json.natvis')
+                         help='Library version number (default: parsed from '
+                              'include/nlohmann/detail/abi_macros.hpp below "output")')
+    parser.add_argument('output', nargs='?', default=REPO_ROOT,
+                         help='Repository root: where include/nlohmann/detail/abi_macros.hpp is '
+                              'read from and where nlohmann_json.natvis is written '
+                              '(default: the repository root this script lives in)')
     args = parser.parse_args()
 
+    derived_tags, derived_version = abi_info(args.output)
+
     namespaces = ['nlohmann']
     abi_prefix = 'json_abi'
-    abi_tags = ['_diag', '_ldvcmp', '_dp', '_bics', '_psp', '_snul']
+    abi_tags = derived_tags
-    version = '_v' + args.version.replace('.', '_')
+    version = '_v' + (args.version or derived_version).replace('.', '_')
     inline_namespaces = []
 
     # generate all combinations of inline namespace names

tools/macro_builder/README.md

@@ -0,0 +1,51 @@
+# macro_builder
+
+Generates the argument-counting macros behind the `NLOHMANN_DEFINE_TYPE_*` and `NLOHMANN_DEFINE_DERIVED_TYPE_*`
+macros in [`include/nlohmann/detail/macro_scope.hpp`](../../include/nlohmann/detail/macro_scope.hpp):
+
+- `NLOHMANN_JSON_EXPAND`
+- `NLOHMANN_JSON_GET_MACRO`, which selects a macro by the number of its arguments (64 slots)
+- `NLOHMANN_JSON_PASTE`, which calls a function-like macro for each member, and its helpers `NLOHMANN_JSON_PASTE2`
+  to `NLOHMANN_JSON_PASTE64`
+- `NLOHMANN_JSON_DOUBLE_PASTE`, which the `*_WITH_NAMES` macros use to call a function-like macro for each
+  (JSON name, member) pair, and its helpers `NLOHMANN_JSON_DOUBLE_PASTE3` to `NLOHMANN_JSON_DOUBLE_PASTE63`
+- the slot table of `NLOHMANN_JSON_TYPE_BODY`, which dispatches `NLOHMANN_DEFINE_TYPE_*(Type)` (no further
+  arguments) to the zero-member implementation and every other argument count to the one-or-more-member
+  implementation
+
+The number of slots (`max_args` in [`main.cpp`](main.cpp)) sets the member limit of these macros.
+`NLOHMANN_JSON_PASTE` and `NLOHMANN_JSON_TYPE_BODY` take the function/prefix as their first argument, so 64 slots
+allow 63 members; `NLOHMANN_JSON_DOUBLE_PASTE` additionally consumes its members two at a time (name, member), so
+it only defines the odd helpers up to `NLOHMANN_JSON_DOUBLE_PASTE63`.
+
+## Usage
+
+From the project root:
+
+```shell
+c++ -std=c++11 tools/macro_builder/main.cpp -o macro_builder
+./macro_builder
+./macro_builder type_body
+```
+
+1. Run `./macro_builder` (no arguments). In `include/nlohmann/detail/macro_scope.hpp`, replace the lines from
+   `#define NLOHMANN_JSON_EXPAND( x ) x` to the `#define NLOHMANN_JSON_DOUBLE_PASTE63(...)` line with the output,
+   without its trailing empty line.
+2. Run `./macro_builder type_body`. Replace the lines from `#define NLOHMANN_JSON_TYPE_BODY(Prefix, ...)` to the
+   `NLOHMANN_JSON_TYPE_BODY_SENTINEL))` line with the output.
+3. Run `make amalgamate`. It updates `single_include/nlohmann/json.hpp` and runs `make pretty`, which indents the
+   continuation lines that the tool writes unindented.
+
+With an unchanged `main.cpp`, these steps reproduce both blocks of `macro_scope.hpp` byte for byte. `make
+macro_builder_check` (also run by CI, see `.github/workflows/check_amalgamation.yml`) automates this: it builds
+`main.cpp`, regenerates both blocks, and fails on a diff against the checked-in header.
+
+## Maintained by hand
+
+The tool does not generate everything that depends on the number of slots. When changing `max_args`, also update:
+
+- the documented limit of 63 members in `docs/mkdocs/docs` and the tests at that limit in
+  `tests/src/unit-udt_macro.cpp`
+
+All three tables pass one macro name per slot to `NLOHMANN_JSON_GET_MACRO`, so they need exactly as many entries as
+it has slots.

tools/macro_builder/main.cpp

@@ -1,10 +1,14 @@
 #include <cstdlib>
 #include <iostream>
 #include <sstream>
+#include <string>
 
 using namespace std;
 
-void build_code(int max_args)
+// Builds NLOHMANN_JSON_EXPAND, NLOHMANN_JSON_GET_MACRO, and the
+// NLOHMANN_JSON_PASTE / NLOHMANN_JSON_PASTE2..PASTE<max_args> dispatch table
+// and recursive definitions.
+string build_paste_code(int max_args)
 {
     stringstream ss;
     ss << "#define NLOHMANN_JSON_EXPAND( x ) x" << endl;
@@ -30,14 +34,75 @@ void build_code(int max_args)
         ss << "v" << i-1 << ")" << endl;
     }
 
-    cout << ss.str() << endl;
+    return ss.str();
+}
+
+// Builds the NLOHMANN_JSON_DOUBLE_PASTE dispatch table and recursive
+// definitions used by the *_WITH_NAMES macros. Its GET_MACRO dispatch reuses
+// the same max_args slots as NLOHMANN_JSON_PASTE, but DOUBLE_PASTE consumes
+// its arguments two at a time (name, member), so an even slot count falls
+// back to the next lower odd NLOHMANN_JSON_DOUBLE_PASTE<N>.
+string build_double_paste_code(int max_args)
+{
+    stringstream ss;
+    ss << "#define NLOHMANN_JSON_DOUBLE_PASTE(...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_GET_MACRO(__VA_ARGS__, \\" << endl;
+    for (int i = max_args ; i > 1 ; i--)
+    {
+        int k = (i % 2 == 1) ? i : i - 1;
+        ss << "NLOHMANN_JSON_DOUBLE_PASTE" << k << ", \\" << endl;
+    }
+    ss << "NLOHMANN_JSON_DOUBLE_PASTE1)(__VA_ARGS__))" << endl;
+
+    ss << "#define NLOHMANN_JSON_DOUBLE_PASTE3(func, v1, v2) func(v1, v2)" << endl;
+    for (int k = 5 ; k <= max_args - 1 ; k += 2)
+    {
+        ss << "#define NLOHMANN_JSON_DOUBLE_PASTE" << k << "(func, ";
+        for (int j = 1 ; j < k - 1 ; j++)
+            ss << "v" << j << ", ";
+        ss << "v" << k - 1 << ") NLOHMANN_JSON_DOUBLE_PASTE3(func, v1, v2) NLOHMANN_JSON_DOUBLE_PASTE" << k - 2 << "(func, ";
+        for (int j = 3 ; j < k - 1 ; j++)
+            ss << "v" << j << ", ";
+        ss << "v" << k - 1 << ")" << endl;
+    }
+
+    return ss.str();
+}
+
+// Builds the NLOHMANN_JSON_TYPE_BODY dispatch table: max_args - 1 slots
+// selecting the *_MEMBERS implementation and a final slot selecting
+// *_EMPTY, so NLOHMANN_DEFINE_TYPE_*(Type) with no further arguments still
+// resolves (issue #4041).
+string build_type_body_table(int max_args)
+{
+    stringstream ss;
+    ss << "#define NLOHMANN_JSON_TYPE_BODY(Prefix, ...) NLOHMANN_JSON_EXPAND(NLOHMANN_JSON_GET_MACRO(__VA_ARGS__, \\" << endl;
+    const int per_line = 8;
+    for (int i = 1 ; i <= max_args ; i++)
+    {
+        ss << (i == max_args ? "Prefix ## EMPTY" : "Prefix ## MEMBERS") << ", ";
+        if (i % per_line == 0)
+            ss << "\\" << endl;
+    }
+    ss << "NLOHMANN_JSON_TYPE_BODY_SENTINEL))" << endl;
+
+    return ss.str();
 }
 
 int main(int argc, char** argv)
 {
     int max_args = 64;
-    build_code(max_args);
+
+    // With "type_body", print only the NLOHMANN_JSON_TYPE_BODY dispatch
+    // table (a separate insertion point in macro_scope.hpp); otherwise
+    // print the EXPAND/GET_MACRO/PASTE/DOUBLE_PASTE block that precedes it.
+    if (argc > 1 && string(argv[1]) == "type_body")
+    {
+        cout << build_type_body_table(max_args);
+    }
+    else
+    {
+        cout << build_paste_code(max_args) << build_double_paste_code(max_args);
+    }
 
     return 0;
 }
-

tools/serve_header/serve_header.py

@@ -5,6 +5,8 @@ import logging
 import os
 import re
 import shutil
+import socket
+import ssl
 import sys
 import subprocess
 
@@ -34,7 +36,7 @@ JSON_VERSION_RE = re.compile(r'\s*#\s*define\s+NLOHMANN_JSON_VERSION_MAJOR\s+')
 
 class ExitHandler(logging.StreamHandler):
     def __init__(self, level):
-        """."""
+        """Exit the process on log records at or above level."""
         super().__init__()
         self.level = level
 
@@ -54,7 +56,7 @@ def is_project_root(test_dir='.'):
 
 class DirectoryEventBucket:
     def __init__(self, callback, delay=1.2, threshold=0.8):
-        """."""
+        """Batch directory events and pass their common path to callback."""
         self.delay = delay
         self.threshold = timedelta(seconds=threshold)
         self.callback = callback
@@ -99,7 +101,7 @@ class WorkTree:
     make_command = 'make'
 
     def __init__(self, root_dir, tree_dir):
-        """."""
+        """Track the working tree at tree_dir and its amalgamated header."""
         self.root_dir = root_dir
         self.tree_dir = tree_dir
         self.rel_dir = os.path.relpath(tree_dir, root_dir)
@@ -114,11 +116,11 @@ class WorkTree:
         self.build_time = t.strftime(DATETIME_FORMAT)
 
     def __hash__(self):
-        """."""
+        """Hash by working tree directory."""
         return hash((self.tree_dir))
 
     def __eq__(self, other):
-        """."""
+        """Compare by working tree directory."""
         if not isinstance(other, type(self)):
             return NotImplemented
         return self.tree_dir == other.tree_dir
@@ -150,7 +152,7 @@ class WorkTree:
 
 class WorkTrees(FileSystemEventHandler):
     def __init__(self, root_dir):
-        """."""
+        """Find the working trees below root_dir and watch it for changes."""
         super().__init__()
         self.root_dir = root_dir
         self.trees = set([])
@@ -250,11 +252,11 @@ class WorkTrees(FileSystemEventHandler):
         self.observer.stop()
         self.observer.join()
 
-class HeaderRequestHandler(SimpleHTTPRequestHandler): # lgtm[py/missing-call-to-init]
+class HeaderRequestHandler(SimpleHTTPRequestHandler):
     cors_origins = DEFAULT_CORS_ORIGINS
 
     def __init__(self, request, client_address, server):
-        """."""
+        """Handle a request for a header below the working trees' root directory."""
         self.worktrees = server.worktrees
         self.worktree = None
         try:
@@ -336,7 +338,7 @@ class HeaderRequestHandler(SimpleHTTPRequestHandler): # lgtm[py/missing-call-to-
 
 class DualStackServer(ThreadingHTTPServer):
     def __init__(self, addr, worktrees):
-        """."""
+        """Serve the headers of worktrees on addr."""
         self.worktrees = worktrees
         super().__init__(addr, HeaderRequestHandler)
 
@@ -349,8 +351,6 @@ class DualStackServer(ThreadingHTTPServer):
 
 if __name__ == '__main__':
     import argparse
-    import ssl
-    import socket
     import yaml
 
     # exit code