Merge branch 'develop' into claude/iterative-diff

Conflicts: - include/nlohmann/json.hpp: kept the PR's diff_recursively()/ diff_object_keys() split and re-applied develop's #5691 (fast path for every object type except an insertion-ordered one; target key order only tracked for such types) inside diff_object_keys(), so both the recursive and the iterative walk get it - single_include/nlohmann/json.hpp: regenerated with make amalgamate - tests/src/unit-json_patch.cpp: kept both new test cases (deeply nested diff from the PR, #5639 regression from develop) Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-01 04:00:31 +00:00 · 2026-09-30 20:36:43 +02:00 · 2026-09-27 20:58:06 +02:00 · 2026-09-27 17:16:01 +02:00 · 2026-09-27 14:00:04 +02:00 · 2026-09-26 07:49:42 +02:00
51 changed files with 1348 additions and 852 deletions
@@ -1,15 +1,9 @@
-# bugprone-use-after-move (hicpp-invalid-access-moved is its alias) still flags
-# the basic_json move constructor, which forwards the whole object to its base
-# class (#5724), and two forwards in the error-message construction of
-# at(KeyType&&) (json.hpp, both overloads: find(std::forward<KeyType>(key))
-# followed by string_t(std::forward<KeyType>(key)) in the throw), which #5689
-# rewrites. Re-enable both checks once those changes have landed.
-# portability-avoid-pragma-once: kept disabled on purpose. #pragma once is accepted
-# by every supported compiler, and tools/amalgamate/amalgamate.py strips it from
-# single_include, so there is nothing left to fix here.
+# TODO: The first three checks are only removed to get the CI going. They have to be addressed at some point.
+# TODO: portability-avoid-pragma-once: should be fixed eventually

 Checks: '*,

+         -portability-template-virtual-member-function,
         -bugprone-use-after-move,
         -hicpp-invalid-access-moved,

@@ -43,6 +37,7 @@ Checks: '*,
         -google-readability-function-size,
         -google-runtime-float,
         -google-runtime-int,
+         -google-runtime-references,
         -hicpp-avoid-goto,
         -hicpp-explicit-conversions,
         -hicpp-function-size,
@@ -76,7 +71,6 @@ Checks: '*,
         -readability-magic-numbers,
         -readability-redundant-access-specifiers,
         -readability-redundant-parentheses,
-         -readability-redundant-typename,
         -readability-simplify-boolean-expr,
         -readability-uppercase-literal-suffix,
         -readability-use-concise-preprocessor-directives'
@@ -87,4 +81,5 @@ CheckOptions:

 WarningsAsErrors: '*'

+#HeaderFilterRegex: '.*nlohmann.*'
 HeaderFilterRegex: '.*hpp$'
@@ -78,13 +78,13 @@ jobs:

  ci_static_analysis_clang:
    runs-on: ubuntu-latest
-    container: silkeh/clang:22
+    container: silkeh/clang:dev
    strategy:
      matrix:
-        target: [ci_test_clang, ci_clang_tidy, ci_test_clang_sanitizer, ci_single_binaries]
+        target: [ci_test_clang, ci_clang_tidy, ci_test_clang_sanitizer, ci_clang_analyze, ci_single_binaries]
    steps:
-      - name: Install git, iwyu (ci_single_binaries), and unzip
-        run: apt-get update ; apt-get install -y git iwyu unzip
+      - name: Install git, clang-tools, iwyu (ci_single_binaries), and unzip
+        run: apt-get update ; apt-get install -y git clang-tools iwyu unzip
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          persist-credentials: false
@@ -8,24 +8,24 @@ set(N 10)
 include(FindPython3)
 find_package(Python3 COMPONENTS Interpreter)

-find_program(CLANG_TOOL NAMES clang++-HEAD clang++ clang++-22 clang++-21 clang++-20 clang++-19 clang++-18 clang++-17 clang++-16 clang++-15 clang++-14 clang++-13 clang++-12 clang++-11 clang++)
+find_program(CLANG_TOOL NAMES clang++-HEAD clang++ clang++-20 clang++-19 clang++-18 clang++-17 clang++-16 clang++-15 clang++-14 clang++-13 clang++-12 clang++-11 clang++)
 execute_process(COMMAND ${CLANG_TOOL} --version OUTPUT_VARIABLE CLANG_TOOL_VERSION ERROR_VARIABLE CLANG_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" CLANG_TOOL_VERSION "${CLANG_TOOL_VERSION}")
 message(STATUS "🔖 Clang ${CLANG_TOOL_VERSION} (${CLANG_TOOL})")

-find_program(CLANG_TIDY_TOOL NAMES clang-tidy-22 clang-tidy-21 clang-tidy-20 clang-tidy-19 clang-tidy-18 clang-tidy-17 clang-tidy-16 clang-tidy-15 clang-tidy-14 clang-tidy-13 clang-tidy-12 clang-tidy-11 clang-tidy)
+find_program(CLANG_TIDY_TOOL NAMES clang-tidy-20 clang-tidy-19 clang-tidy-18 clang-tidy-17 clang-tidy-16 clang-tidy-15 clang-tidy-14 clang-tidy-13 clang-tidy-12 clang-tidy-11 clang-tidy)
 execute_process(COMMAND ${CLANG_TIDY_TOOL} --version OUTPUT_VARIABLE CLANG_TIDY_TOOL_VERSION ERROR_VARIABLE CLANG_TIDY_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" CLANG_TIDY_TOOL_VERSION "${CLANG_TIDY_TOOL_VERSION}")
 message(STATUS "🔖 Clang-Tidy ${CLANG_TIDY_TOOL_VERSION} (${CLANG_TIDY_TOOL})")

 message(STATUS "🔖 CMake ${CMAKE_VERSION} (${CMAKE_COMMAND})")

-find_program(GCC_TOOL NAMES g++-latest g++-HEAD g++ g++-16 g++-15 g++-14 g++-13 g++-12 g++-11 g++-10)
+find_program(GCC_TOOL NAMES g++-latest g++-HEAD g++ g++-15 g++-14 g++-13 g++-12 g++-11 g++-10)
 execute_process(COMMAND ${GCC_TOOL} --version OUTPUT_VARIABLE GCC_TOOL_VERSION ERROR_VARIABLE GCC_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" GCC_TOOL_VERSION "${GCC_TOOL_VERSION}")
 message(STATUS "🔖 GCC ${GCC_TOOL_VERSION} (${GCC_TOOL})")

-find_program(GCOV_TOOL NAMES gcov-HEAD gcov gcov-16 gcov-15 gcov-14 gcov-13 gcov-12 gcov-11 gcov-10)
+find_program(GCOV_TOOL NAMES gcov-HEAD gcov gcov-15 gcov-14 gcov-13 gcov-12 gcov-11 gcov-10)
 execute_process(COMMAND ${GCOV_TOOL} --version OUTPUT_VARIABLE GCOV_TOOL_VERSION ERROR_VARIABLE GCOV_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" GCOV_TOOL_VERSION "${GCOV_TOOL_VERSION}")
 message(STATUS "🔖 GCOV ${GCOV_TOOL_VERSION} (${GCOV_TOOL})")
@@ -69,6 +69,7 @@ message(STATUS "🔖 Valgrind ${VALGRIND_TOOL_VERSION} (${VALGRIND_TOOL})")
 find_program(GENHTML_TOOL NAMES genhtml)
 find_program(PLOG_CONVERTER_TOOL NAMES plog-converter)
 find_program(PVS_STUDIO_ANALYZER_TOOL NAMES pvs-studio-analyzer)
+find_program(SCAN_BUILD_TOOL NAMES scan-build-15 scan-build-14 scan-build-13 scan-build-12 scan-build-11 scan-build)

 # the individual source files
 file(GLOB_RECURSE SRC_FILES ${PROJECT_SOURCE_DIR}/include/nlohmann/*.hpp)
@@ -425,6 +426,21 @@ add_custom_target(ci_test_valgrind
    COMMENT "Compile and test with Valgrind"
 )

+###############################################################################
+# Check code with Clang Static Analyzer.
+###############################################################################
+
+set(CLANG_ANALYZER_CHECKS "fuchsia.HandleChecker,nullability.NullableDereferenced,nullability.NullablePassedToNonnull,nullability.NullableReturnedFromNonnull,optin.cplusplus.UninitializedObject,optin.cplusplus.VirtualCall,optin.mpi.MPI-Checker,optin.osx.OSObjectCStyleCast,optin.osx.cocoa.localizability.EmptyLocalizationContextChecker,optin.osx.cocoa.localizability.NonLocalizedStringChecker,optin.performance.GCDAntipattern,optin.performance.Padding,optin.portability.UnixAPI,security.FloatLoopCounter,security.insecureAPI.DeprecatedOrUnsafeBufferHandling,security.insecureAPI.bcmp,security.insecureAPI.bcopy,security.insecureAPI.bzero,security.insecureAPI.rand,security.insecureAPI.strcpy,valist.CopyToSelf,valist.Uninitialized,valist.Unterminated,webkit.NoUncountedMemberChecker,webkit.RefCntblBaseVirtualDtor,core.CallAndMessage,core.DivideZero,core.NonNullParamChecker,core.NullDereference,core.StackAddressEscape,core.UndefinedBinaryOperatorResult,core.VLASize,core.uninitialized.ArraySubscript,core.uninitialized.Assign,core.uninitialized.Branch,core.uninitialized.CapturedBlockVariable,core.uninitialized.UndefReturn,cplusplus.InnerPointer,cplusplus.Move,cplusplus.NewDelete,cplusplus.NewDeleteLeaks,cplusplus.PlacementNew,cplusplus.PureVirtualCall,deadcode.DeadStores,nullability.NullPassedToNonnull,nullability.NullReturnedFromNonnull,osx.API,osx.MIG,osx.NumberObjectConversion,osx.OSObjectRetainCount,osx.ObjCProperty,osx.SecKeychainAPI,osx.cocoa.AtSync,osx.cocoa.AutoreleaseWrite,osx.cocoa.ClassRelease,osx.cocoa.Dealloc,osx.cocoa.IncompatibleMethodTypes,osx.cocoa.Loops,osx.cocoa.MissingSuperCall,osx.cocoa.NSAutoreleasePool,osx.cocoa.NSError,osx.cocoa.NilArg,osx.cocoa.NonNilReturnValue,osx.cocoa.ObjCGenerics,osx.cocoa.RetainCount,osx.cocoa.RunLoopAutoreleaseLeak,osx.cocoa.SelfInit,osx.cocoa.SuperDealloc,osx.cocoa.UnusedIvars,osx.cocoa.VariadicMethodTypes,osx.coreFoundation.CFError,osx.coreFoundation.CFNumber,osx.coreFoundation.CFRetainRelease,osx.coreFoundation.containers.OutOfBounds,osx.coreFoundation.containers.PointerSizedValues,security.insecureAPI.UncheckedReturn,security.insecureAPI.decodeValueOfObjCType,security.insecureAPI.getpw,security.insecureAPI.gets,security.insecureAPI.mkstemp,security.insecureAPI.mktemp,security.insecureAPI.vfork,unix.API,unix.Malloc,unix.MallocSizeof,unix.MismatchedDeallocator,unix.Vfork,unix.cstring.BadSizeArg,unix.cstring.NullArg")
+
+add_custom_target(ci_clang_analyze
+    COMMAND CXX=${CLANG_TOOL} ${CMAKE_COMMAND}
+        -DCMAKE_BUILD_TYPE=Debug -GNinja
+        -DJSON_BuildTests=ON
+        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_clang_analyze
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_clang_analyze && ${SCAN_BUILD_TOOL} -enable-checker ${CLANG_ANALYZER_CHECKS} --use-c++=${CLANG_TOOL} -analyze-headers -o ${PROJECT_BINARY_DIR}/report ninja
+    COMMENT "Check code with Clang Analyzer"
+)
+
 ###############################################################################
 # Check code with Cppcheck.
 ###############################################################################
@@ -2,6 +2,7 @@
 # -Wno-c++98-compat               The library targets C++11.
 # -Wno-c++98-compat-pedantic      The library targets C++11.
 # -Wno-deprecated-declarations    The library contains annotations for deprecated functions.
+# -Wno-extra-semi-stmt            The library uses assert which triggers this warning.
 # -Wno-padded                     We do not care about padding warnings.
 # -Wno-covered-switch-default     All switches list all cases and a default case.
 # -Wno-c2y-extensions             Clang 22.1 diagnoses __COUNTER__ as a C2y extension, also in
@@ -19,6 +20,7 @@ set(CLANG_CXXFLAGS
    -Wno-c++98-compat
    -Wno-c++98-compat-pedantic
    -Wno-deprecated-declarations
+    -Wno-extra-semi-stmt
    -Wno-padded
    -Wno-covered-switch-default
    -Wno-c2y-extensions
@@ -1,4 +1,4 @@
-# Warning flags determined for GCC 16.2.0 with https://github.com/nlohmann/gcc_flags:
+# Warning flags determined for GCC 15.1.0 with https://github.com/nlohmann/gcc_flags:
 # Ignored GCC warnings:
 # -Wno-abi-tag           We do not care about ABI tags.
 # -Wno-aggregate-return  The library uses aggregate returns.
@@ -16,8 +16,6 @@ set(GCC_CXXFLAGS
    --extra-warnings
    -W
    -WNSObject-attribute
-    -Wabbreviated-auto-in-template-arg
-    -Wabi
    -Wno-abi-tag
    -Waddress
    -Waddress-of-packed-member
@@ -66,7 +64,6 @@ set(GCC_CXXFLAGS
    -Wanalyzer-tainted-divisor
    -Wanalyzer-tainted-offset
    -Wanalyzer-tainted-size
-    -Wanalyzer-throw-of-unexpected-type
    -Wanalyzer-too-complex
    -Wanalyzer-undefined-behavior-ptrdiff
    -Wanalyzer-undefined-behavior-strtok
@@ -83,13 +80,10 @@ set(GCC_CXXFLAGS
    -Warith-conversion
    -Warray-bounds=2
    -Warray-compare
-    -Warray-parameter
    -Warray-parameter=2
    -Wattribute-alias=2
    -Wattribute-warning
    -Wattributes
-    -Wauto-profile
-    -Wbidi-chars=any
    -Wbool-compare
    -Wbool-operation
    -Wbuiltin-declaration-mismatch
@@ -105,7 +99,6 @@ set(GCC_CXXFLAGS
    -Wc++20-compat
    -Wc++20-extensions
    -Wc++23-extensions
-    -Wc++26-compat
    -Wc++26-extensions
    -Wc++2a-compat
    -Wcalloc-transposed-args
@@ -149,7 +142,6 @@ set(GCC_CXXFLAGS
    -Wdeprecated-enum-enum-conversion
    -Wdeprecated-enum-float-conversion
    -Wdeprecated-literal-operator
-    -Wdeprecated-openmp
    -Wdeprecated-variadic-comma-omission
    -Wdisabled-optimization
    -Wdiv-by-zero
@@ -164,18 +156,21 @@ set(GCC_CXXFLAGS
    -Wenum-conversion
    -Wexceptions
    -Wexpansion-to-defined
-    -Wexperimental-fmv-target
-    -Wexpose-global-module-tu-local
-    -Wexternal-tu-local
    -Wextra
    -Wextra-semi
    -Wflex-array-member-not-at-end
    -Wfloat-conversion
    -Wfloat-equal
-    -Wformat-diag
-    -Wformat-overflow=2
-    -Wformat-signedness
-    -Wformat-truncation=2
+    -Wformat -Wformat-contains-nul
+    -Wformat -Wformat-diag
+    -Wformat -Wformat-extra-args
+    -Wformat -Wformat-nonliteral
+    -Wformat -Wformat-overflow=2
+    -Wformat -Wformat-security
+    -Wformat -Wformat-signedness
+    -Wformat -Wformat-truncation=2
+    -Wformat -Wformat-y2k
+    -Wformat -Wformat-zero-length
    -Wformat=2
    -Wframe-address
    -Wfree-nonheap-object
@@ -202,8 +197,6 @@ set(GCC_CXXFLAGS
    -Winvalid-offsetof
    -Winvalid-pch
    -Winvalid-utf8
-    -Wkeyword-macro
-    -Wleading-whitespace=spaces
    -Wliteral-suffix
    -Wlogical-not-parentheses
    -Wlogical-op
@@ -234,7 +227,6 @@ set(GCC_CXXFLAGS
    -Wnarrowing
    -Wnoexcept
    -Wnoexcept-type
-    -Wnon-c-typedef-for-linkage
    -Wnon-template-friend
    -Wnon-virtual-dtor
    -Wnonnull
@@ -277,8 +269,6 @@ set(GCC_CXXFLAGS
    -Wscalar-storage-order
    -Wself-move
    -Wsequence-point
-    -Wsfinae-incomplete
-    -Wsfinae-incomplete=2
    -Wshadow=compatible-local
    -Wshadow=global
    -Wshadow=local
@@ -299,7 +289,6 @@ set(GCC_CXXFLAGS
    -Wstrict-aliasing=3
    -Wstrict-null-sentinel
    -Wstrict-overflow
-    -Wstrict-overflow=5
    -Wstring-compare
    -Wstringop-overflow
    -Wstringop-overflow=4
@@ -344,8 +333,8 @@ set(GCC_CXXFLAGS
    -Wunreachable-code
    -Wunsafe-loop-optimizations
    -Wunused
-    -Wunused-but-set-parameter=3
-    -Wunused-but-set-variable=3
+    -Wunused-but-set-parameter
+    -Wunused-but-set-variable
    -Wunused-const-variable=2
    -Wunused-function
    -Wunused-label
@@ -60,11 +60,11 @@ measures that counter them. The measures are described in detail in [Quality ass
 |---------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|
 | Out-of-bounds read/write ([CWE-125](https://cwe.mitre.org/data/definitions/125.html), [CWE-787](https://cwe.mitre.org/data/definitions/787.html)) | bounds checks on all reads from the input; AddressSanitizer and Valgrind on the test suite; OSS-Fuzz      |
 | Integer overflow ([CWE-190](https://cwe.mitre.org/data/definitions/190.html)) | UndefinedBehaviorSanitizer with integer overflow detection; Clang-Tidy; Cppcheck                 |
-| Use after free, double free ([CWE-416](https://cwe.mitre.org/data/definitions/416.html), [CWE-415](https://cwe.mitre.org/data/definitions/415.html)) | ownership of all memory by values; AddressSanitizer and Valgrind; Clang-Tidy (incl. Clang Static Analyzer checks) |
+| Use after free, double free ([CWE-416](https://cwe.mitre.org/data/definitions/416.html), [CWE-415](https://cwe.mitre.org/data/definitions/415.html)) | ownership of all memory by values; AddressSanitizer and Valgrind; Clang Static Analyzer          |
 | Memory leaks ([CWE-401](https://cwe.mitre.org/data/definitions/401.html)) | Valgrind (Memcheck) on the test suite                                                            |
 | Uncontrolled recursion ([CWE-674](https://cwe.mitre.org/data/definitions/674.html)) | iterative parser, binary readers, and destructor; bounded recursion in value operations; tests with deeply nested inputs |
 | Uncontrolled resource consumption ([CWE-400](https://cwe.mitre.org/data/definitions/400.html)) | allocations based on announced sizes are capped; OSS-Fuzz with memory limits                     |
-| Undefined behavior in general ([CWE-758](https://cwe.mitre.org/data/definitions/758.html)) | UndefinedBehaviorSanitizer; runtime assertions; Clang-Tidy (incl. Clang Static Analyzer checks), Cppcheck, Infer |
+| Undefined behavior in general ([CWE-758](https://cwe.mitre.org/data/definitions/758.html)) | UndefinedBehaviorSanitizer; runtime assertions; Clang-Tidy, Cppcheck, Clang Static Analyzer, Infer |

 In addition, every line of the library is covered by the unit tests, and all parsers are fuzz-tested around the clock
 by [OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json).
@@ -183,8 +183,8 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
        ```

 - [x] The code is checked with the latest [Cppcheck](https://cppcheck.sourceforge.io) with all warnings enabled.
- [x] The code is checked with the latest [Clang Static Analyzer](https://clang-analyzer.llvm.org) checks, run
-  through Clang-Tidy's `clang-analyzer-*` checks with warnings as errors.
+- [x] The code is checked with the latest [Clang Static Analyzer](https://clang-analyzer.llvm.org) with 89 enabled
+  rules.
 - [x] The code is checked with [Infer](https://fbinfer.com).
 - [x] The code is checked with [Codacy](https://app.codacy.com/gh/nlohmann/json/dashboard).

@@ -354,22 +354,22 @@ void())
 }

 template < typename BasicJsonType, typename T, std::size_t... Idx >
-std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(const BasicJsonType& j,
+std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(BasicJsonType&& j,
                     identity_tag<std::array<T, sizeof...(Idx)>> /*unused*/, index_sequence<Idx...> /*unused*/)
 {
-    return { { j.at(Idx).template get<T>()... } };
+    return { { std::forward<BasicJsonType>(j).at(Idx).template get<T>()... } };
 }

 template < typename BasicJsonType, typename T, std::size_t N >
-auto from_json(const BasicJsonType& j, identity_tag<std::array<T, N>> tag)
-> decltype(from_json_inplace_array_impl(j, tag, make_index_sequence<N> {}))
+auto from_json(BasicJsonType&& j, identity_tag<std::array<T, N>> tag)
+-> decltype(from_json_inplace_array_impl(std::forward<BasicJsonType>(j), tag, make_index_sequence<N> {}))
 {
    if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
    {
        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
    }

-    return from_json_inplace_array_impl(j, tag, make_index_sequence<N> {});
+    return from_json_inplace_array_impl(std::forward<BasicJsonType>(j), tag, make_index_sequence<N> {});
 }

 template<typename BasicJsonType>
@@ -504,54 +504,54 @@ template<std::size_t PTagValue, typename BasicJsonType, typename... Types>
 using tuple_type = std::tuple < decltype(from_json_tuple_get_impl(std::declval<BasicJsonType>(), detail::identity_tag<Types> {}, detail::priority_tag<PTagValue> {}))... >;

 template<std::size_t PTagValue, typename... Args, typename BasicJsonType, std::size_t... Idx>
-tuple_type<PTagValue, const BasicJsonType&, Args...> from_json_tuple_impl_base(const BasicJsonType& j, index_sequence<Idx...> /*unused*/)
+tuple_type<PTagValue, BasicJsonType, Args...> from_json_tuple_impl_base(BasicJsonType&& j, index_sequence<Idx...> /*unused*/)
 {
-    return tuple_type<PTagValue, const BasicJsonType&, Args...>(from_json_tuple_get_impl(j.at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
+    return tuple_type<PTagValue, BasicJsonType, Args...>(from_json_tuple_get_impl(std::forward<BasicJsonType>(j).at(Idx), detail::identity_tag<Args> {}, detail::priority_tag<PTagValue> {})...);
 }

 template<std::size_t PTagValue, typename BasicJsonType>
-std::tuple<> from_json_tuple_impl_base(const BasicJsonType& /*unused*/, index_sequence<> /*unused*/)
+std::tuple<> from_json_tuple_impl_base(BasicJsonType& /*unused*/, index_sequence<> /*unused*/)
 {
    return {};
 }

 template < typename BasicJsonType, class A1, class A2 >
-std::pair<A1, A2> from_json_tuple_impl(const BasicJsonType& j, identity_tag<std::pair<A1, A2>> /*unused*/, priority_tag<0> /*unused*/)
+std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair<A1, A2>> /*unused*/, priority_tag<0> /*unused*/)
 {
-    return {j.at(0).template get<A1>(),
-            j.at(1).template get<A2>()};
+    return {std::forward<BasicJsonType>(j).at(0).template get<A1>(),
+            std::forward<BasicJsonType>(j).at(1).template get<A2>()};
 }

 template<typename BasicJsonType, typename A1, typename A2>
-inline void from_json_tuple_impl(const BasicJsonType& j, std::pair<A1, A2>& p, priority_tag<1> /*unused*/)
+inline void from_json_tuple_impl(BasicJsonType&& j, std::pair<A1, A2>& p, priority_tag<1> /*unused*/)
 {
-    p = from_json_tuple_impl(j, identity_tag<std::pair<A1, A2>> {}, priority_tag<0> {});
+    p = from_json_tuple_impl(std::forward<BasicJsonType>(j), identity_tag<std::pair<A1, A2>> {}, priority_tag<0> {});
 }

 template<typename BasicJsonType, typename... Args>
-std::tuple<Args...> from_json_tuple_impl(const BasicJsonType& j, identity_tag<std::tuple<Args...>> /*unused*/, priority_tag<2> /*unused*/)
+std::tuple<Args...> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::tuple<Args...>> /*unused*/, priority_tag<2> /*unused*/)
 {
-    static_assert(cxpr_and<cxpr_or<cxpr_not<std::is_reference<Args>>, is_compatible_reference_type<const BasicJsonType&, Args>>...>::value,
+    static_assert(cxpr_and<cxpr_or<cxpr_not<std::is_reference<Args>>, is_compatible_reference_type<BasicJsonType, Args>>...>::value,
                  "Can not return a tuple containing references to types not contained in a Json, try Json::get_to()");
-    return from_json_tuple_impl_base<1, Args...>(j, index_sequence_for<Args...> {});
+    return from_json_tuple_impl_base<1, Args...>(std::forward<BasicJsonType>(j), index_sequence_for<Args...> {});
 }

 template<typename BasicJsonType, typename... Args>
-inline void from_json_tuple_impl(const BasicJsonType& j, std::tuple<Args...>& t, priority_tag<3> /*unused*/)
+inline void from_json_tuple_impl(BasicJsonType&& j, std::tuple<Args...>& t, priority_tag<3> /*unused*/)
 {
-    t = from_json_tuple_impl_base<2, Args...>(j, index_sequence_for<Args...> {});
+    t = from_json_tuple_impl_base<2, Args...>(std::forward<BasicJsonType>(j), index_sequence_for<Args...> {});
 }

 template<typename BasicJsonType, typename TupleRelated>
-auto from_json(const BasicJsonType& j, TupleRelated&& t)
-> decltype(from_json_tuple_impl(j, std::forward<TupleRelated>(t), priority_tag<3> {}))
+auto from_json(BasicJsonType&& j, TupleRelated&& t)
+-> decltype(from_json_tuple_impl(std::forward<BasicJsonType>(j), std::forward<TupleRelated>(t), priority_tag<3> {}))
 {
    if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
    {
        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
    }

-    return from_json_tuple_impl(j, std::forward<TupleRelated>(t), priority_tag<3> {});
+    return from_json_tuple_impl(std::forward<BasicJsonType>(j), std::forward<TupleRelated>(t), priority_tag<3> {});
 }

 template < typename BasicJsonType, typename Key, typename Value, typename Compare, typename Allocator,
@@ -636,7 +636,7 @@ struct from_json_fn
 /// namespace to hold default `from_json` function
 /// to see why this is required:
 /// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4381.html
-namespace // NOLINT(cert-dcl59-cpp,fuchsia-header-anon-namespaces,google-build-namespaces,misc-anonymous-namespace-in-header)
+namespace // NOLINT(cert-dcl59-cpp,fuchsia-header-anon-namespaces,google-build-namespaces)
 {
 #endif
 JSON_INLINE_VARIABLE constexpr const auto& from_json = // NOLINT(misc-definitions-in-headers)
@@ -546,7 +546,7 @@ struct to_json_fn
 /// namespace to hold default `to_json` function
 /// to see why this is required:
 /// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4381.html
-namespace // NOLINT(cert-dcl59-cpp,fuchsia-header-anon-namespaces,google-build-namespaces,misc-anonymous-namespace-in-header)
+namespace // NOLINT(cert-dcl59-cpp,fuchsia-header-anon-namespaces,google-build-namespaces)
 {
 #endif
 JSON_INLINE_VARIABLE constexpr const auto& to_json = // NOLINT(misc-definitions-in-headers)
@@ -407,7 +407,7 @@ class binary_reader
    @brief Parses a C-style string from the BSON input.
    @param[in,out] result  A reference to the string variable where the read
                            string is to be stored.
-    @return `true` if the \\x00-byte indicating the end of the string was
+    @return `true` if the \x00-byte indicating the end of the string was
             encountered before the EOF; false` indicates an unexpected EOF.
    */
    bool get_bson_cstr(string_t& result)
@@ -437,7 +437,7 @@ class binary_reader
    @brief read a C-style string from contiguous input in one step

    @param[in,out] result  the string to append to
-    @return whether the string was read; if the input has no \\x00-byte, nothing
+    @return whether the string was read; if the input has no \x00-byte, nothing
            is read, and @ref get_bson_cstr reports the end of the input
    */
    bool get_bson_cstr_bulk(string_t& result, std::true_type /*bulk*/)
@@ -769,9 +769,6 @@ struct container_input_adapter_factory< ContainerType,

           static adapter_type create(ContainerType&& container)
 {
-    // container is forwarded twice on purpose: the resulting begin/end
-    // iterator types must match adapter_type, computed the same way
-    // NOLINTNEXTLINE(bugprone-use-after-move)
    return input_adapter(begin(std::forward<ContainerType>(container)), end(std::forward<ContainerType>(container)));
 }
       };
@@ -440,7 +440,7 @@ class json_sax_dom_parser
                }
                default: // LCOV_EXCL_LINE
                    // Handle all possible types discretely, default handler should never be reached.
-                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
+                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
            }
        }
    }
@@ -903,7 +903,7 @@ class json_sax_dom_callback_parser
                }
                default: // LCOV_EXCL_LINE
                    // Handle all possible types discretely, default handler should never be reached.
-                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
+                    JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
            }
        }
    }
@@ -220,9 +220,9 @@ class lexer : public lexer_base<BasicJsonType>
    /////////////////////

    /*!
-    @brief get codepoint from 4 hex characters following `\\u`
+    @brief get codepoint from 4 hex characters following `\u`

-    For input "\\u c1 c2 c3 c4" the codepoint is:
+    For input "\u c1 c2 c3 c4" the codepoint is:
      (c1 * 0x1000) + (c2 * 0x0100) + (c3 * 0x0010) + c4
    = (c1 << 12) + (c2 << 8) + (c3 << 4) + (c4 << 0)

@@ -35,7 +35,7 @@ This class implements a both iterators (iterator and const_iterator) for the
      been set (e.g., by a constructor or a copy assignment). If the iterator is
      default-constructed, it is *uninitialized* and most methods are undefined.
      **The library uses assertions to detect calls on uninitialized iterators.**
-This class satisfies the following concept requirements (REQ-JSON-01):
+@requirement REQ-JSON-01 The class satisfies the following concept requirements:
 -
 [BidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator):
  The iterator that can be moved can be moved in both directions (i.e.
@@ -213,11 +213,11 @@ namespace std
    JSON_HEDLEY_PRAGMA(clang diagnostic ignored "-Wmismatched-tags")
 #endif
 template<typename IteratorType>
-class tuple_size<::nlohmann::detail::iteration_proxy_value<IteratorType>> // NOLINT(cert-dcl58-cpp,bugprone-std-namespace-modification)
+class tuple_size<::nlohmann::detail::iteration_proxy_value<IteratorType>> // NOLINT(cert-dcl58-cpp)
    : public std::integral_constant<std::size_t, 2> {};

 template<std::size_t N, typename IteratorType>
-class tuple_element<N, ::nlohmann::detail::iteration_proxy_value<IteratorType >> // NOLINT(cert-dcl58-cpp,bugprone-std-namespace-modification)
+class tuple_element<N, ::nlohmann::detail::iteration_proxy_value<IteratorType >> // NOLINT(cert-dcl58-cpp)
 {
  public:
    using type = decltype(
@@ -29,7 +29,7 @@ namespace detail
 iterator (to create @ref reverse_iterator) and @ref const_iterator (to
 create @ref const_reverse_iterator).

-This class satisfies the following concept requirements (REQ-JSON-02):
+@requirement REQ-JSON-02 The class satisfies the following concept requirements:
 -
 [BidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator):
  The iterator that can be moved can be moved in both directions (i.e.
@@ -278,11 +278,11 @@ class json_pointer
            JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", s, "'"), nullptr));
        }

-        // the index does not fit into size_type; on 64-bit platforms this is
-        // only SIZE_MAX itself (see #2203 and #5395)
+        // only triggered on special platforms (like 32bit), see also
+        // https://github.com/nlohmann/json/pull/2203
        if (res >= static_cast<unsigned long long>((std::numeric_limits<size_type>::max)()))  // NOLINT(runtime/int)
        {
-            JSON_THROW(detail::out_of_range::create(410, detail::concat("array index ", s, " exceeds size_type"), nullptr));
+            JSON_THROW(detail::out_of_range::create(410, detail::concat("array index ", s, " exceeds size_type"), nullptr));   // LCOV_EXCL_LINE
        }

        return static_cast<size_type>(res);
@@ -316,7 +316,7 @@ class json_pointer
    /*!
    @brief create and return a reference to the pointed to value

-    Complexity: Linear in the number of reference tokens.
+    @complexity Linear in the number of reference tokens.

    @throw parse_error.106 if an array index begins with '0'
    @throw parse_error.109 if array index is not a number
@@ -403,7 +403,7 @@ class json_pointer

    @return reference to the JSON value pointed to by the JSON pointer

-    Complexity: Linear in the length of the JSON pointer.
+    @complexity Linear in the length of the JSON pointer.

    @throw parse_error.106   if an array index begins with '0'
    @throw parse_error.109   if an array index was not a number
@@ -195,6 +195,13 @@
    #define JSON_NO_THREAD_LOCAL 1
 #endif

+// disable documentation warnings on clang
+#if defined(__clang__)
+    #pragma clang diagnostic push
+    #pragma clang diagnostic ignored "-Wdocumentation"
+    #pragma clang diagnostic ignored "-Wdocumentation-unknown-command"
+#endif
+
 // allow disabling exceptions
 #if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
    #define JSON_THROW(exception) throw exception
@@ -253,7 +260,7 @@
    {                                                                                           \
        /* NOLINTNEXTLINE(modernize-type-traits) we use C++11 */                                \
        static_assert(std::is_enum<ENUM_TYPE>::value, #ENUM_TYPE " must be an enum!");          \
-        /* NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) we don't want to depend on <array> */ \
+        /* NOLINTNEXTLINE(modernize-avoid-c-arrays) we don't want to depend on <array> */       \
        static const std::pair<ENUM_TYPE, BasicJsonType> m[] = __VA_ARGS__;                     \
        auto it = std::find_if(std::begin(m), std::end(m),                                      \
                               [e](const std::pair<ENUM_TYPE, BasicJsonType>& ej_pair) -> bool  \
@@ -267,7 +274,7 @@
    {                                                                                           \
        /* NOLINTNEXTLINE(modernize-type-traits) we use C++11 */                                \
        static_assert(std::is_enum<ENUM_TYPE>::value, #ENUM_TYPE " must be an enum!");          \
-        /* NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) we don't want to depend on <array> */ \
+        /* NOLINTNEXTLINE(modernize-avoid-c-arrays) we don't want to depend on <array> */       \
        static const std::pair<ENUM_TYPE, BasicJsonType> m[] = __VA_ARGS__;                     \
        auto it = std::find_if(std::begin(m), std::end(m),                                      \
                               [&j](const std::pair<ENUM_TYPE, BasicJsonType>& ej_pair) -> bool \
@@ -306,7 +313,7 @@ void templated_json_throw(ExceptionType exception)
    {                                                                                           \
        /* NOLINTNEXTLINE(modernize-type-traits) we use C++11 */                                \
        static_assert(std::is_enum<ENUM_TYPE>::value, #ENUM_TYPE " must be an enum!");          \
-        /* NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) we don't want to depend on <array> */ \
+        /* NOLINTNEXTLINE(modernize-avoid-c-arrays) we don't want to depend on <array> */       \
        static const std::pair<ENUM_TYPE, BasicJsonType> m[] = __VA_ARGS__;                     \
        auto it = std::find_if(std::begin(m), std::end(m),                                      \
                               [e](const std::pair<ENUM_TYPE, BasicJsonType>& ej_pair) -> bool  \
@@ -321,7 +328,7 @@ void templated_json_throw(ExceptionType exception)
    {                                                                                           \
        /* NOLINTNEXTLINE(modernize-type-traits) we use C++11 */                                \
        static_assert(std::is_enum<ENUM_TYPE>::value, #ENUM_TYPE " must be an enum!");          \
-        /* NOLINTNEXTLINE(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) we don't want to depend on <array> */ \
+        /* NOLINTNEXTLINE(modernize-avoid-c-arrays) we don't want to depend on <array> */       \
        static const std::pair<ENUM_TYPE, BasicJsonType> m[] = __VA_ARGS__;                     \
        auto it = std::find_if(std::begin(m), std::end(m),                                      \
                               [&j](const std::pair<ENUM_TYPE, BasicJsonType>& ej_pair) -> bool \
@@ -8,6 +8,11 @@

 #pragma once

+// restore clang diagnostic settings
+#if defined(__clang__)
+    #pragma clang diagnostic pop
+#endif
+
 // clean up
 #undef JSON_ASSERT
 #undef JSON_INTERNAL_CATCH
@@ -13,7 +13,6 @@
 #include <iterator> // back_inserter
 #include <memory> // shared_ptr, make_shared
 #include <string> // basic_string
-#include <type_traits> // conditional, integral_constant, is_same
 #include <utility> // move
 #include <vector> // vector

@@ -118,14 +117,12 @@ class output_stream_adapter : public output_adapter_protocol<CharType>
        : stream(s)
    {}

-    // NOLINTNEXTLINE(portability-template-virtual-member-function)
    void write_character(CharType c) override
    {
        stream.put(c);
    }

    JSON_HEDLEY_NON_NULL(2)
-    // NOLINTNEXTLINE(portability-template-virtual-member-function)
    void write_characters(const CharType* s, std::size_t length) override
    {
        stream.write(s, static_cast<std::streamsize>(length));
@@ -193,82 +190,7 @@ class output_adapter_sink
    output_adapter_t<CharType> oa;
 };

-/// @brief whether std::basic_string<CharType> has a non-deprecated std::char_traits
-///        specialization, and is therefore usable as output_adapter's default StringType
-///
-/// std::char_traits is only guaranteed (and, on some standard libraries, only
-/// implemented without a deprecation warning) for the character types listed
-/// below; std::char_traits<T> for any other T (e.g. std::uint8_t, as used by the
-/// binary writers) is a non-standard extension some standard libraries deprecate.
-/// See https://github.com/nlohmann/json/issues/5725 item 2.
-template<typename CharType>
-struct is_output_adapter_string_char_type : std::integral_constant < bool,
-    std::is_same<CharType, char>::value ||
-    std::is_same<CharType, wchar_t>::value ||
-    std::is_same<CharType, char16_t>::value ||
-    std::is_same<CharType, char32_t>::value
-#if defined(__cpp_lib_char8_t) && (__cpp_lib_char8_t >= 201907L)
-    || std::is_same<CharType, char8_t>::value
-#endif
-    > {};
-
-/// @brief placeholder type for output_adapter's StringType and (with JSON_NO_IO
-///        undefined) its std::basic_ostream constructor parameter, for CharType
-///        with no non-deprecated std::char_traits specialization
-///
-/// Never actually used: the StringType- and std::basic_ostream-based
-/// output_adapter constructors are neither documented nor tested for such
-/// CharType (only the std::vector-based constructor is used for them, by the
-/// binary writers). Naming std::basic_string<CharType> or
-/// std::basic_ostream<CharType> anywhere such a constructor would otherwise be
-/// declared - even as an unused default template argument or an unused,
-/// never-called overload - instantiates std::char_traits<CharType> merely to
-/// name the type, which is exactly what triggers the deprecation warning this
-/// placeholder avoids.
-template<typename CharType>
-struct output_adapter_no_string_type {};
-
-// Select output_adapter's default StringType (and, below, its ostream
-// constructor's parameter type) via partial specialization, not
-// std::conditional: std::conditional<B, T, F> requires both T and F to be named
-// as template arguments up front, which would still instantiate (and thus name)
-// std::basic_string<CharType> / std::basic_ostream<CharType> for every CharType,
-// defeating the point. A bool non-type parameter with two specializations only
-// ever names the type that is actually selected.
-template<typename CharType, bool = is_output_adapter_string_char_type<CharType>::value>
-struct output_adapter_default_string_type
-{
-    using type = output_adapter_no_string_type<CharType>;
-};
-
-template<typename CharType>
-struct output_adapter_default_string_type<CharType, true>
-{
-    using type = std::basic_string<CharType>;
-};
-
-#ifndef JSON_NO_IO
-/// distinct from output_adapter_no_string_type, so the placeholder overloads of
-/// output_adapter's constructor (used when CharType is not a character type)
-/// stay distinct overloads instead of colliding into a single redeclaration
-template<typename CharType>
-struct output_adapter_no_ostream_type {};
-
-template<typename CharType, bool = is_output_adapter_string_char_type<CharType>::value>
-struct output_adapter_ostream_type
-{
-    using type = output_adapter_no_ostream_type<CharType>;
-};
-
-template<typename CharType>
-struct output_adapter_ostream_type<CharType, true>
-{
-    using type = std::basic_ostream<CharType>;
-};
-#endif  // JSON_NO_IO
-
-template < typename CharType, typename StringType =
-           typename output_adapter_default_string_type<CharType>::type >
+template<typename CharType, typename StringType = std::basic_string<CharType>>
 class output_adapter
 {
  public:
@@ -277,7 +199,7 @@ class output_adapter
        : oa(std::make_shared<output_vector_adapter<CharType, AllocatorType>>(vec)) {}

 #ifndef JSON_NO_IO
-    output_adapter(typename output_adapter_ostream_type<CharType>::type& s)
+    output_adapter(std::basic_ostream<CharType>& s)
        : oa(std::make_shared<output_stream_adapter<CharType>>(s)) {}
 #endif  // JSON_NO_IO

@@ -67,7 +67,7 @@ class serializer
    @param[in] ichar  indentation character to use
    @param[in] pretty_print_  whether the output shall be pretty-printed
    @param[in] ensure_ascii_ If @a ensure_ascii_ is true, all non-ASCII
-    characters in the output are escaped with `\\uXXXX` sequences, and the
+    characters in the output are escaped with `\uXXXX` sequences, and the
    result consists of ASCII characters only.
    @param[in] indent_step_  the indent level
    @param[in] error_handler_  how to react on decoding errors
@@ -772,7 +772,7 @@ class serializer

    @param[in] s  the string to escape

-    Complexity: Linear in the length of string @a s.
+    @complexity Linear in the length of string @a s.
    */
    void dump_escaped(const string_t& s)
    {
@@ -1290,7 +1290,7 @@ class serializer
    }

    /*!
-     * @brief write a lowercase "\\uXXXX" escape sequence into @a string_buffer
+     * @brief write a lowercase "\uXXXX" escape sequence into @a string_buffer
     *
     * Branch-free replacement for `snprintf(buf, 7, "\\u%04x", codeunit)` in the
     * string escaping hot path. It writes exactly six characters ('\\', 'u' and
@@ -1650,7 +1650,7 @@ class serializer
    /// whether to pretty-print the output
    const bool pretty_print;

-    /// whether to escape non-ASCII characters with \\uXXXX sequences
+    /// whether to escape non-ASCII characters with \uXXXX sequences
    const bool ensure_ascii;

    /// the indent level
@@ -62,7 +62,8 @@ inline StringType escape(const StringType& s)

 /*!
 * @brief string unescaping as described in RFC 6901 (Sect. 4)
- * @param[in,out] s string to unescape in place
+ * @param[in] s string to unescape
+ * @return    unescaped string
 *
 * Note the order of escaping "~1" to "/" and "~0" to "~" is important.
 *
@@ -18,6 +18,16 @@
 #ifndef INCLUDE_NLOHMANN_JSON_HPP_
 #define INCLUDE_NLOHMANN_JSON_HPP_

+// Workaround for GCC template redefinition errors in C++ modules
+// When nlohmann/json.hpp is included in a C++20 module preamble after
+// other module imports, GCC may report spurious redefinition errors for
+// STL templates. These pragmas suppress those false positives.
+// See: https://github.com/nlohmann/json/issues/5103
+#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wignored-attributes"
+#endif
+
 #include <algorithm> // all_of, find, for_each, none_of
 #include <cstddef> // nullptr_t, ptrdiff_t, size_t
 #include <functional> // hash, less
@@ -2340,12 +2350,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec

    @throw what @ref json_serializer<ValueType> `from_json()` method throws

-    The example below shows several conversions from JSON values
+    @liveexample{The example below shows several conversions from JSON values
    to other types. There a few things to note: (1) Floating-point numbers can
-    be converted to integers, (2) A JSON array can be converted to a standard
-    `std::vector<short>`, (3) A JSON object can be converted to C++
-    associative containers such as `std::unordered_map<std::string,
-    json>`.
+    be converted to integers\, (2) A JSON array can be converted to a standard
+    `std::vector<short>`\, (3) A JSON object can be converted to C++
+    associative containers such as `std::unordered_map<std::string\,
+    json>`.,get__ValueType_const}

    @since version 2.1.0
    */
@@ -2412,7 +2422,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec

    @return a copy of *this, converted into @a BasicJsonType

-    Complexity: Depending on the implementation of the called `from_json()`
+    @complexity Depending on the implementation of the called `from_json()`
                method.

    @since version 3.2.0
@@ -2436,7 +2446,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec

    @return a copy of *this

-    Complexity: Constant.
+    @complexity Constant.

    @since version 2.1.0
    */
@@ -2482,7 +2492,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    @tparam ValueTypeCV the provided value type
    @tparam ValueType the returned value type

-    @return copy of the JSON value, converted to @a ValueType if necessary
+    @return copy of the JSON value, converted to @tparam ValueType if necessary

    @throw what @ref json_serializer<ValueType> `from_json()` method throws if conversion is required

@@ -2520,12 +2530,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    @return pointer to the internally stored JSON value if the requested
    pointer type @a PointerType fits to the JSON value; `nullptr` otherwise

-    Complexity: Constant.
+    @complexity Constant.

-    The example below shows how pointers to internal values of a
+    @liveexample{The example below shows how pointers to internal values of a
    JSON value can be requested. Note that no type conversions are made and a
    `nullptr` is returned if the value and the requested pointer type does not
-    match.
+    match.,get__PointerType}

    @sa see @ref get_ptr() for explicit pointer-member access

@@ -2619,14 +2629,14 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    to the JSON value type (e.g., the JSON value is of type boolean, but a
    string is requested); see example below

-    Complexity: Linear in the size of the JSON value.
+    @complexity Linear in the size of the JSON value.

-    The example below shows several conversions from JSON values
+    @liveexample{The example below shows several conversions from JSON values
    to other types. There a few things to note: (1) Floating-point numbers can
-    be converted to integers, (2) A JSON array can be converted to a standard
-    `std::vector<short>`, (3) A JSON object can be converted to C++
-    associative containers such as `std::unordered_map<std::string,
-    json>`.
+    be converted to integers\, (2) A JSON array can be converted to a standard
+    `std::vector<short>`\, (3) A JSON object can be converted to C++
+    associative containers such as `std::unordered_map<std::string\,
+    json>`.,operator__ValueType}

    @since version 1.0.0
    */
@@ -5049,19 +5059,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    /// @deprecated This function is deprecated since 3.8.0 and will be removed in
    ///             version 4.0.0 of the library. Please use
    ///             sax_parse(ptr, ptr + len) instead.
-    //
-    // Clang reports "declaration is marked with '@deprecated' command but does
-    // not have a deprecation attribute" for this overload even though
-    // JSON_HEDLEY_DEPRECATED_FOR below does expand to __attribute__((deprecated));
-    // isolated reproductions of this exact declaration shape (doc comment,
-    // template<>, two stacked __attribute__ lines, an overload set of the same
-    // name) do not reproduce it, so this looks like a Clang comment/declaration
-    // association quirk specific to this overload within basic_json, not a
-    // genuine documentation bug. See #5725 item 2.
-#if defined(__clang__)
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdocumentation-deprecated-sync"
-#endif
    template <typename SAX>
    JSON_HEDLEY_DEPRECATED_FOR(3.8.0, sax_parse(ptr, ptr + len, ...))
    JSON_HEDLEY_NON_NULL(2)
@@ -5078,9 +5075,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
               // NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
               : detail::binary_reader<basic_json, decltype(ia), SAX>(std::move(ia), format).sax_parse(format, sax, strict);
    }
-#if defined(__clang__)
-#pragma clang diagnostic pop
-#endif
 #ifndef JSON_NO_IO
    /// @brief deserialize from stream
    /// @sa https://json.nlohmann.me/api/basic_json/operator_gtgt/
@@ -6112,21 +6106,256 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    {
        // the patch
        basic_json result(value_t::array);
+        diff_recursively(result, source, target, path, 0);
+        return result;
+    }

-        // if the values are the same, return an empty patch
+  private:
+    /// @brief two arrays or two objects @ref diff_iteratively is diffing
+    struct diff_frame
+    {
+        diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_) noexcept
+            : source(source_), target(target_), path_length(path_length_)
+        {}
+
+        // declared for GCC's -Weffc++, which asks for them in a class with
+        // pointer members and a non-trivial destructor; the exception
+        // specifications are left implicit, as GCC 4.8 rejects explicit ones
+        // that differ from them
+        diff_frame(const diff_frame&) = default;
+        diff_frame(diff_frame&&) = default;
+        diff_frame& operator=(const diff_frame&) = default;
+        diff_frame& operator=(diff_frame&&) = default;
+        ~diff_frame() = default;
+
+        /// the values being diffed, both arrays or both objects
+        const basic_json* source;
+        const basic_json* target;
+        /// the length of their path in `current_path`
+        std::size_t path_length;
+        /// arrays: the next index to diff
+        std::size_t index = 0;
+        /// objects: the next member of source to look at
+        const_iterator member{}; // NOLINT(readability-redundant-member-init)
+        /// objects: the keys common to both, in source's order
+        std::vector<typename object_t::key_type> common_keys{}; // NOLINT(readability-redundant-member-init)
+        /// objects: the next entry of common_keys
+        std::size_t next_common = 0;
+        /// objects: the "add" operations for keys only target has
+        basic_json added_ops{}; // NOLINT(readability-redundant-member-init)
+    };
+
+    // The operations of a diff are built by the functions below rather than
+    // where they are needed: building one takes several temporaries, and
+    // unoptimized builds give each temporary a stack slot of its own in the
+    // function it appears in. In diff_recursively, which is on the call stack
+    // once per nesting level, that made every level cost kilobytes of stack.
+
+    /// @brief append a "replace" operation for @a path with @a value to @a result
+    static void diff_replace(basic_json& result, const string_t& path, const basic_json& value)
+    {
+        result.push_back(
+        {
+            {"op", "replace"}, {"path", path}, {"value", value}
+        });
+    }
+
+    /// @brief append a "remove" operation for @a path to @a result
+    static void diff_remove(basic_json& result, const string_t& path)
+    {
+        result.push_back(object(
+        {
+            {"op", "remove"}, {"path", path}
+        }));
+    }
+
+    /// @brief append an "add" operation for @a path with @a value to @a result
+    static void diff_add(basic_json& result, const string_t& path, const basic_json& value)
+    {
+        result.push_back(
+        {
+            {"op", "add"}, {"path", path}, {"value", value}
+        });
+    }
+
+    /// @brief append the "remove" operations for the elements of array
+    ///        @a source from @a index on, and the "add" operations for the
+    ///        elements of array @a target from source's size on, to @a result
+    static void diff_array_tails(basic_json& result, const basic_json& source, const basic_json& target,
+                                 const string_t& path, const std::size_t index)
+    {
+        // remove my remaining elements, highest index first; appending
+        // in that order avoids the quadratic reinsertion done before
+        for (std::size_t j = source.size(); j > index; --j)
+        {
+            diff_remove(result, detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1)));
+        }
+
+        // add other remaining elements
+        for (std::size_t i = source.size(); i < target.size(); ++i)
+        {
+            diff_add(result, detail::concat<string_t>(path, "/-"), target[i]);
+        }
+    }
+
+    /*!
+    @brief compare the keys of objects @a source and @a target
+
+    If object_t does not keep its members in insertion order, or if the keys
+    both objects have are in the same order in both, and the keys only
+    @a target has come after them, stores the keys common to both in
+    source's order in @a common_keys, stores the "add" operations for the keys
+    only @a target has in @a added_ops, and returns true: the caller then diffs
+    the objects member by member. Otherwise, appends operations that remove
+    every member of @a source and add every member of @a target to @a result,
+    and returns false.
+    */
+    static bool diff_object_keys(basic_json& result, const basic_json& source, const basic_json& target,
+                                 const string_t& path, std::vector<typename object_t::key_type>& common_keys,
+                                 basic_json& added_ops)
+    {
+        // first pass: record, for every source key, whether it is
+        // common to both objects (in source's iteration order) or
+        // was deleted (i.e., in source but not in target) -- this is
+        // a by-product of the target.find() call already needed to
+        // tell the two cases apart, so it adds no extra lookups. The
+        // "remove" ops themselves are emitted later, interleaved
+        // with the per-key diffs in the caller's fast path, to match
+        // source's original iteration order (as the original,
+        // pre-reordering-aware implementation did) instead of
+        // grouping all removes before all per-key diffs.
+        std::vector<typename object_t::key_type> common_keys_source_order;
+        for (auto it = source.cbegin(); it != source.cend(); ++it)
+        {
+            if (target.find(it.key()) != target.end())
+            {
+                common_keys_source_order.push_back(it.key());
+            }
+        }
+
+        // second pass: find keys that were added (i.e., in target but
+        // not in source), and record the keys common to both, in
+        // target's iteration order -- again a by-product of the
+        // source.find() call already needed to detect added keys. At
+        // the same time, determine whether every added key comes
+        // after every common key in target's order (a precondition
+        // for the fast path, which only ever appends new keys
+        // at the very end). Both are only needed for an object_t that
+        // keeps its members in insertion order, such as the one
+        // backing `ordered_json`; for any other object_t, the fast
+        // path is always taken and they are not computed.
+        // The patch ops for keys that were added (i.e., in target but not
+        // in source) are built here so the fast path can reuse
+        // them without a second source.find() per target key. Only
+        // used by the fast path -- the slow (reordering) path
+        // rebuilds "add" ops for every key itself.
+        std::vector<typename object_t::key_type> common_keys_target_order;
+        bool new_keys_form_suffix = true;
+        bool seen_new_key = false;
+        for (auto it = target.cbegin(); it != target.cend(); ++it)
+        {
+            if (source.find(it.key()) == source.end())
+            {
+                seen_new_key = true;
+                diff_add(added_ops, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
+            }
+            else
+            {
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning(push )
+#pragma warning(disable : 4127) // ignore warning to replace if with if constexpr
+#endif
+                if (detail::is_ordered_map<object_t>::value)
+                {
+                    common_keys_target_order.push_back(it.key());
+                    if (seen_new_key)
+                    {
+                        new_keys_form_suffix = false;
+                    }
+                }
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning( pop )
+#endif
+            }
+        }
+
+        // Only an object type that keeps its members in insertion
+        // order, such as nlohmann::ordered_map, can need reordering:
+        // patch() appends a new member at the end of such an object.
+        // Any other object type places its members itself - std::map
+        // in key order, a hash map in an order its operator== ignores -
+        // so a member-by-member diff always reproduces target there.
+        if (!detail::is_ordered_map<object_t>::value
+                || (common_keys_source_order == common_keys_target_order && new_keys_form_suffix))
+        {
+            // fast path: order of common keys already matches (or the
+            // object_t's iteration order does not depend on
+            // insertion history), so a plain per-key diff is correct
+            // and minimal, as before
+            common_keys = std::move(common_keys_source_order);
+            return true;
+        }
+
+        // slow path: the common keys are in a different relative
+        // order in source and target (only possible for a
+        // reorderable object_t like ordered_map). Building a
+        // minimal reordering patch is a nontrivial (LCS-like)
+        // problem; instead, remove every source key -- both
+        // deleted keys (which must be removed regardless) and
+        // common keys (removed so they can be re-added in
+        // target's order) -- and re-add every key that should
+        // remain, with its final target value, in target's
+        // order. basic_json::patch()'s "add" operation on an
+        // object uses operator[], which appends at the end for a
+        // vector-backed insertion-ordered map when the key does
+        // not already exist -- so removing a key and then adding
+        // it moves it to the end, fixing its position.
+        for (auto it = source.cbegin(); it != source.cend(); ++it)
+        {
+            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+        }
+
+        // add every key that is either common (just removed
+        // above) or brand new, in target's iteration order, so
+        // that the final order after applying the patch matches
+        // target exactly
+        for (auto it = target.cbegin(); it != target.cend(); ++it)
+        {
+            diff_add(result, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
+        }
+        return false;
+    }
+
+    /*!
+    @brief @ref diff, for values at nesting level @a depth, appending the
+           operations to @a result
+
+    Diffing two arrays or objects calls this function again, once per nesting
+    level, so values nested deeply enough used to exhaust the call stack and
+    terminate the process. The descent is bounded here: once @ref
+    detail::recursion_depth_limit levels have been entered, @ref
+    diff_iteratively diffs what is left without the call stack.
+    */
+    static void diff_recursively(basic_json& result, const basic_json& source, const basic_json& target,
+                                 const string_t& path, const std::size_t depth)
+    {
+        // if the values are the same, there is nothing to do
        if (source == target)
        {
-            return result;
+            return;
+        }
+
+        if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
+        {
+            diff_iteratively(result, source, target, path);
+            return;
        }

        if (source.type() != target.type())
        {
            // different types: replace value
-            result.push_back(
-            {
-                {"op", "replace"}, {"path", path}, {"value", target}
-            });
-            return result;
+            diff_replace(result, path, target);
+            return;
        }

        switch (source.type())
@@ -6138,200 +6367,50 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                while (i < source.size() && i < target.size())
                {
                    // recursive call to compare array values at index i
-                    auto temp_diff = diff(source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)));
-                    result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                    diff_recursively(result, source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)), depth + 1);
                    ++i;
                }

                // We now reached the end of at least one array
                // in a second pass, traverse the remaining elements
-
-                // remove my remaining elements, highest index first; appending
-                // in that order avoids the quadratic reinsertion done before
-                for (std::size_t j = source.size(); j > i; --j)
-                {
-                    result.push_back(object(
-                    {
-                        {"op", "remove"},
-                        {"path", detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1))}
-                    }));
-                }
-                i = source.size();
-
-                // add other remaining elements
-                while (i < target.size())
-                {
-                    result.push_back(
-                    {
-                        {"op", "add"},
-                        {"path", detail::concat<string_t>(path, "/-")},
-                        {"value", target[i]}
-                    });
-                    ++i;
-                }
-
+                diff_array_tails(result, source, target, path, i);
                break;
            }

            case value_t::object:
            {
-                // first pass: record, for every source key, whether it is
-                // common to both objects (in source's iteration order) or
-                // was deleted (i.e., in source but not in target) -- this is
-                // a by-product of the target.find() call already needed to
-                // tell the two cases apart, so it adds no extra lookups. The
-                // "remove" ops themselves are emitted later, interleaved
-                // with the recursive per-key diffs in the fast path below,
-                // to match source's original iteration order (as the
-                // original, pre-reordering-aware implementation did) instead
-                // of grouping all removes before all recursive diffs.
-                std::vector<typename object_t::key_type> common_keys_source_order;
-                for (auto it = source.cbegin(); it != source.cend(); ++it)
-                {
-                    if (target.find(it.key()) != target.end())
-                    {
-                        common_keys_source_order.push_back(it.key());
-                    }
-                }
-
-                // second pass: find keys that were added (i.e., in target but
-                // not in source), and record the keys common to both, in
-                // target's iteration order -- again a by-product of the
-                // source.find() call already needed to detect added keys. At
-                // the same time, determine whether every added key comes
-                // after every common key in target's order (a precondition
-                // for the fast path below, which only ever appends new keys
-                // at the very end). Both are only needed for an object_t that
-                // keeps its members in insertion order, such as the one
-                // backing `ordered_json`; for any other object_t, the fast
-                // path is always taken and they are not computed.
-                // patch ops for keys that were added (i.e., in target but not
-                // in source); built here so the fast path below can reuse
-                // them without a second source.find() per target key. Only
-                // used by the fast path -- the slow (reordering) path
-                // rebuilds "add" ops for every key itself.
-                std::vector<typename object_t::key_type> common_keys_target_order;
+                std::vector<typename object_t::key_type> common_keys;
                basic_json added_ops(value_t::array);
-                bool new_keys_form_suffix = true;
-                bool seen_new_key = false;
-                for (auto it = target.cbegin(); it != target.cend(); ++it)
+                if (diff_object_keys(result, source, target, path, common_keys, added_ops))
                {
-                    if (source.find(it.key()) == source.end())
-                    {
-                        seen_new_key = true;
-                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
-                        added_ops.push_back(
-                        {
-                            {"op", "add"}, {"path", path_key},
-                            {"value", it.value()}
-                        });
-                    }
-                    else
-                    {
-#ifdef JSON_HEDLEY_MSVC_VERSION
-#pragma warning(push )
-#pragma warning(disable : 4127) // ignore warning to replace if with if constexpr
-#endif
-                        if (detail::is_ordered_map<object_t>::value)
-                        {
-                            common_keys_target_order.push_back(it.key());
-                            if (seen_new_key)
-                            {
-                                new_keys_form_suffix = false;
-                            }
-                        }
-#ifdef JSON_HEDLEY_MSVC_VERSION
-#pragma warning( pop )
-#endif
-                    }
-                }
-
-                // Only an object type that keeps its members in insertion
-                // order, such as nlohmann::ordered_map, can need reordering:
-                // patch() appends a new member at the end of such an object.
-                // Any other object type places its members itself - std::map
-                // in key order, a hash map in an order its operator== ignores -
-                // so a member-by-member diff always reproduces target there.
-                if (!detail::is_ordered_map<object_t>::value
-                        || (common_keys_source_order == common_keys_target_order && new_keys_form_suffix))
-                {
-                    // fast path: order of common keys already matches (or the
-                    // object_t's iteration order does not depend on
-                    // insertion history), so a plain per-key recursive diff
-                    // is correct and minimal, as before. common_keys_source_order
-                    // is, by construction, the subsequence of source's keys
-                    // that are common to both objects, in source's iteration
-                    // order -- so it can be walked in lockstep with `source`
-                    // using a cheap key comparison instead of another lookup.
-                    // Deleted keys (those source keys not in common_keys_source_order)
-                    // are interleaved here too, in source's original order, to
-                    // match the historical (pre-reordering-aware) output order.
-                    auto common_it = common_keys_source_order.cbegin();
+                    // fast path: common_keys is, by construction, the
+                    // subsequence of source's keys that are common to both
+                    // objects, in source's iteration order -- so it can be
+                    // walked in lockstep with `source` using a cheap key
+                    // comparison instead of another lookup. Deleted keys
+                    // (those source keys not in common_keys) are interleaved
+                    // here too, in source's original order, to match the
+                    // historical (pre-reordering-aware) output order.
+                    auto common_it = common_keys.cbegin();
                    for (auto it = source.cbegin(); it != source.cend(); ++it)
                    {
-                        if (common_it != common_keys_source_order.cend() && it.key() == *common_it)
+                        if (common_it != common_keys.cend() && it.key() == *common_it)
                        {
-                            const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
-                            auto temp_diff = diff(it.value(), target[it.key()], path_key);
-                            result.insert(result.end(), temp_diff.begin(), temp_diff.end());
+                            diff_recursively(result, it.value(), target[it.key()], detail::concat<string_t>(path, '/', detail::escape(it.key())), depth + 1);
                            ++common_it;
                        }
                        else
                        {
                            // found a key that is not in target -> remove it
-                            const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
-                            result.push_back(object(
-                            {
-                                {"op", "remove"}, {"path", path_key}
-                            }));
+                            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
                        }
                    }

-                    // append the "add" ops for brand-new keys collected above
-                    // during the pass over target -- no second source.find()
-                    // per target key needed
+                    // append the "add" ops for brand-new keys collected by
+                    // diff_object_keys -- no second source.find() per target
+                    // key needed
                    result.insert(result.end(), added_ops.begin(), added_ops.end());
                }
-                else
-                {
-                    // slow path: the common keys are in a different relative
-                    // order in source and target (only possible for a
-                    // reorderable object_t like ordered_map). Building a
-                    // minimal reordering patch is a nontrivial (LCS-like)
-                    // problem; instead, remove every source key -- both
-                    // deleted keys (which must be removed regardless) and
-                    // common keys (removed so they can be re-added in
-                    // target's order) -- and re-add every key that should
-                    // remain, with its final target value, in target's
-                    // order. basic_json::patch()'s "add" operation on an
-                    // object uses operator[], which appends at the end for a
-                    // vector-backed insertion-ordered map when the key does
-                    // not already exist -- so removing a key and then adding
-                    // it moves it to the end, fixing its position.
-                    for (auto it = source.cbegin(); it != source.cend(); ++it)
-                    {
-                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
-                        result.push_back(object(
-                        {
-                            {"op", "remove"}, {"path", path_key}
-                        }));
-                    }
-
-                    // add every key that is either common (just removed
-                    // above) or brand new, in target's iteration order, so
-                    // that the final order after applying the patch matches
-                    // target exactly
-                    for (auto it = target.cbegin(); it != target.cend(); ++it)
-                    {
-                        const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
-                        result.push_back(
-                        {
-                            {"op", "add"}, {"path", path_key},
-                            {"value", it.value()}
-                        });
-                    }
-                }
-
                break;
            }

@@ -6346,16 +6425,170 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
            default:
            {
                // both primitive types: replace value
-                result.push_back(
-                {
-                    {"op", "replace"}, {"path", path}, {"value", target}
-                });
+                diff_replace(result, path, target);
                break;
            }
        }
-
-        return result;
    }
+
+    /*!
+    @brief @ref diff without the call stack, appending the operations to
+           @a result
+
+    Produces the same operations as @ref diff_recursively. Only reached for
+    values nested more deeply than @ref detail::recursion_depth_limit.
+    */
+    static void diff_iteratively(basic_json& result, const basic_json& source, const basic_json& target,
+                                 const string_t& path)
+    {
+        // The arrays and objects being diffed are kept on an explicit stack,
+        // and every pair of elements is still diffed completely before the
+        // next one, so the operations come out in the same order as in
+        // diff_recursively. The path of the values being diffed is kept in
+        // one buffer that grows and shrinks with the stack, rather than in a
+        // new string per level.
+        std::vector<diff_frame> stack;
+        string_t current_path = path;
+
+        // diff `s` against `t`, whose path is current_path: primitives,
+        // values of different types, and objects whose members were reordered
+        // are handled right away; arrays and other objects get a frame
+        const auto enter = [&result, &stack, &current_path](const basic_json & s, const basic_json & t)
+        {
+            // if the values are the same, there is nothing to do. Arrays and
+            // objects are not compared up front: comparing them visits
+            // everything below them, so doing that at every level would take
+            // quadratic time in the nesting depth - equal ones yield no
+            // operations anyway.
+            if ((!s.is_structured() || !t.is_structured()) && s == t)
+            {
+                return;
+            }
+
+            if (s.type() != t.type())
+            {
+                // different types: replace value
+                diff_replace(result, current_path, t);
+                return;
+            }
+
+            switch (s.type())
+            {
+                case value_t::array:
+                {
+                    stack.emplace_back(&s, &t, current_path.size());
+                    return;
+                }
+
+                case value_t::object:
+                {
+                    std::vector<typename object_t::key_type> common_keys;
+                    basic_json added_ops(value_t::array);
+                    if (diff_object_keys(result, s, t, current_path, common_keys, added_ops))
+                    {
+                        // fast path: the frame walks source in lockstep with
+                        // common_keys, as diff_recursively does, and appends
+                        // added_ops once all members are done
+                        stack.emplace_back(&s, &t, current_path.size());
+                        stack.back().member = s.cbegin();
+                        stack.back().common_keys = std::move(common_keys);
+                        stack.back().added_ops = std::move(added_ops);
+                    }
+                    return;
+                }
+
+                case value_t::null:
+                case value_t::string:
+                case value_t::boolean:
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                case value_t::binary:
+                case value_t::discarded:
+                default:
+                {
+                    // both primitive types: replace value
+                    diff_replace(result, current_path, t);
+                    return;
+                }
+            }
+        };
+
+        enter(source, target);
+        while (!stack.empty())
+        {
+            // the frame is copied out member by member and changed through
+            // stack.back(): enter() may push a frame and the end of the loop
+            // pops it, either of which would invalidate a reference to it
+            const basic_json* const s = stack.back().source;
+            const basic_json* const t = stack.back().target;
+            const std::size_t path_length = stack.back().path_length;
+            const std::size_t depth = stack.size();
+
+            if (s->is_array())
+            {
+                const auto& source_array = *s->m_data.m_value.array;
+                const auto& target_array = *t->m_data.m_value.array;
+
+                // first pass: traverse common elements
+                const std::size_t i = stack.back().index;
+                if (i < source_array.size() && i < target_array.size())
+                {
+                    ++stack.back().index;
+                    detail::concat_into(current_path, '/', detail::to_string<string_t>(i));
+                    enter(source_array[i], target_array[i]);
+                    if (stack.size() == depth)
+                    {
+                        current_path.resize(path_length);
+                    }
+                    continue;
+                }
+
+                // We now reached the end of at least one array
+                // in a second pass, traverse the remaining elements
+                diff_array_tails(result, *s, *t, current_path, i);
+            }
+            else
+            {
+                const const_iterator it = stack.back().member;
+                if (it != s->cend())
+                {
+                    ++stack.back().member;
+                    const std::size_t next_common = stack.back().next_common;
+                    if (next_common < stack.back().common_keys.size() && it.key() == stack.back().common_keys[next_common])
+                    {
+                        ++stack.back().next_common;
+                        const basic_json& target_value = (*t)[it.key()];
+                        detail::concat_into(current_path, '/', detail::escape(it.key()));
+                        enter(it.value(), target_value);
+                        if (stack.size() == depth)
+                        {
+                            current_path.resize(path_length);
+                        }
+                    }
+                    else
+                    {
+                        // found a key that is not in target -> remove it
+                        diff_remove(result, detail::concat<string_t>(current_path, '/', detail::escape(it.key())));
+                    }
+                    continue;
+                }
+
+                // append the "add" ops for brand-new keys collected when the
+                // object was entered
+                result.insert(result.end(), stack.back().added_ops.begin(), stack.back().added_ops.end());
+            }
+
+            // this array or object is done: continue with the one it is in
+            stack.pop_back();
+            if (!stack.empty())
+            {
+                current_path.resize(stack.back().path_length);
+            }
+        }
+    }
+
+  public:
    /// @}

    ////////////////////////////////
@@ -6501,7 +6734,7 @@ namespace std // NOLINT(cert-dcl58-cpp)
 /// @brief hash value for JSON objects
 /// @sa https://json.nlohmann.me/api/basic_json/std_hash/
 NLOHMANN_BASIC_JSON_TPL_DECLARATION
-struct hash<nlohmann::NLOHMANN_BASIC_JSON_TPL> // NOLINT(cert-dcl58-cpp,bugprone-std-namespace-modification)
+struct hash<nlohmann::NLOHMANN_BASIC_JSON_TPL> // NOLINT(cert-dcl58-cpp)
 {
    std::size_t operator()(const nlohmann::NLOHMANN_BASIC_JSON_TPL& j) const
    {
@@ -6534,7 +6767,7 @@ struct less< ::nlohmann::detail::value_t> // do not remove the space after '<',
 /// @brief exchanges the values of two JSON objects
 /// @sa https://json.nlohmann.me/api/basic_json/std_swap/
 NLOHMANN_BASIC_JSON_TPL_DECLARATION
-inline void swap(nlohmann::NLOHMANN_BASIC_JSON_TPL& j1, nlohmann::NLOHMANN_BASIC_JSON_TPL& j2) noexcept(  // NOLINT(readability-inconsistent-declaration-parameter-name, cert-dcl58-cpp,bugprone-std-namespace-modification)
+inline void swap(nlohmann::NLOHMANN_BASIC_JSON_TPL& j1, nlohmann::NLOHMANN_BASIC_JSON_TPL& j2) noexcept(  // NOLINT(readability-inconsistent-declaration-parameter-name, cert-dcl58-cpp)
    is_nothrow_move_constructible<nlohmann::NLOHMANN_BASIC_JSON_TPL>::value&&                          // NOLINT(misc-redundant-expression,cppcoreguidelines-noexcept-swap,performance-noexcept-swap)
    is_nothrow_move_assignable<nlohmann::NLOHMANN_BASIC_JSON_TPL>::value)
 {
@@ -6548,7 +6781,7 @@ inline void swap(nlohmann::NLOHMANN_BASIC_JSON_TPL& j1, nlohmann::NLOHMANN_BASIC
 /// @brief std::formatter specialization for JSON values
 /// @sa https://json.nlohmann.me/api/basic_json/std_formatter/
 NLOHMANN_BASIC_JSON_TPL_DECLARATION
-struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-cpp,bugprone-std-namespace-modification)
+struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-cpp)
 {
    // -1 means compact output (dump()); any value >= 0 means pretty-printed
    // output with that many spaces (or indent_char) per level (dump(indent, indent_char)).
@@ -6625,6 +6858,11 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c

 #include <nlohmann/detail/macro_unscope.hpp>

+// End of GCC diagnostic pragmas for C++ modules support
+#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L
+    #pragma GCC diagnostic pop
+#endif
+
 // The user-defined string literals are in a separate header, because their
 // bodies instantiate the parser in every translation unit that includes them.
 // Define JSON_NO_AUTOMATIC_UDLS to include <nlohmann/json_literals.hpp> only
@@ -90,11 +90,11 @@ target_compile_options(test_main PUBLIC
    # https://github.com/nlohmann/json/pull/3229
    $<$<CXX_COMPILER_ID:Intel>:-diag-disable=2196>

+    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wno-deprecated;-Wno-float-equal>
    $<$<CXX_COMPILER_ID:GNU>:-Wno-deprecated-declarations>
    $<$<CXX_COMPILER_ID:Intel>:-diag-disable=1786>)
-target_include_directories(test_main SYSTEM PUBLIC
-    thirdparty/doctest)
 target_include_directories(test_main PUBLIC
+    thirdparty/doctest
    thirdparty/fifo_map
    ${PROJECT_BINARY_DIR}/include)
 target_link_libraries(test_main PUBLIC ${NLOHMANN_JSON_TARGET_NAME})
@@ -12,6 +12,7 @@ target_compile_options(abi_compat_common INTERFACE
    # https://github.com/nlohmann/json/pull/3229
    $<$<CXX_COMPILER_ID:Intel>:-diag-disable=2196>

+    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wno-deprecated;-Wno-float-equal>
    $<$<CXX_COMPILER_ID:GNU>:-Wno-deprecated-declarations>
    $<$<CXX_COMPILER_ID:Intel>:-diag-disable=1786>)
 target_include_directories(abi_compat_common SYSTEM INTERFACE
@@ -28,7 +28,7 @@ std::string namespace_name(std::string ns, T* /*unused*/ = nullptr) // NOLINT(pe
    std::smatch m;

    // extract the true namespace name from the function signature
-    CAPTURE(ns)
+    CAPTURE(ns);
    CHECK(std::regex_search(ns, m, std::regex("nlohmann(::[a-zA-Z0-9_]+)*::basic_json")));

    return m.str();
@@ -59,10 +59,10 @@ TEST_CASE_TEMPLATE_DEFINE("value_in_range_of trait", T, value_in_range_of_test)

    INFO("type := ", type_str);

-    CAPTURE(val_min)
-    CAPTURE(min_in_range)
-    CAPTURE(val_max)
-    CAPTURE(max_in_range)
+    CAPTURE(val_min);
+    CAPTURE(min_in_range);
+    CAPTURE(val_max);
+    CAPTURE(max_in_range);

    if (min_in_range)
    {
@@ -239,7 +239,7 @@ TEST_CASE("controlled bad_alloc")
            // iterative path instead, part-way through its worklist.
            const auto check_deep_copy = [](bool objects)
            {
-                CAPTURE(objects)
+                CAPTURE(objects);

                next_construct_fails = false;

@@ -315,7 +315,7 @@ struct nth_alloc_fails_allocator : std::allocator<T>
 template<class BasicJsonType>
 void check_deep_copy_survives_failing_allocation(bool nest_objects)
 {
-    CAPTURE(nest_objects)
+    CAPTURE(nest_objects);

    fail_at_alloc_call = -1;

@@ -352,7 +352,7 @@ void check_deep_copy_survives_failing_allocation(bool nest_objects)
    // must come out exactly as it went in
    for (std::size_t n = 0; n < total_allocations; ++n)
    {
-        CAPTURE(n)
+        CAPTURE(n);
        alloc_call_count = 0;
        fail_at_alloc_call = static_cast<long>(n);

@@ -18,7 +18,7 @@ DOCTEST_CLANG_SUPPRESS_WARNING("-Wstrict-overflow")
 static int assert_counter;

 /// set failure variable to true instead of calling assert(x)
-#define JSON_ASSERT(x) do { if (!(x)) { ++assert_counter; } } while (false)
+#define JSON_ASSERT(x) {if (!(x)) ++assert_counter; }

 #include <nlohmann/json.hpp>
 using nlohmann::json;
@@ -89,7 +89,7 @@ TEST_CASE("binary writer output sinks")
        // the first iteration
        for (const auto& j : test_values())
        {
-            CAPTURE(j.dump(-1, ' ', false, json::error_handler_t::replace))
+            CAPTURE(j.dump(-1, ' ', false, json::error_handler_t::replace));

            std::vector<std::uint8_t> cbor;
            json::to_cbor(j, cbor);
@@ -120,8 +120,8 @@ TEST_CASE("binary writer output sinks")
                    {
                        continue; // not a supported combination
                    }
-                    CAPTURE(use_size)
-                    CAPTURE(use_type)
+                    CAPTURE(use_size);
+                    CAPTURE(use_type);
                    std::vector<std::uint8_t> ubjson;
                    json::to_ubjson(j, ubjson, use_size, use_type);
                    CHECK(json::to_ubjson(j, use_size, use_type) == ubjson);
@@ -141,7 +141,7 @@ TEST_CASE("binary writer output sinks")

        for (const auto& j : bson_values())
        {
-            CAPTURE(j.dump())
+            CAPTURE(j.dump());
            std::vector<std::uint8_t> bson;
            json::to_bson(j, bson);
            CHECK(json::to_bson(j) == bson);
@@ -152,7 +152,7 @@ TEST_CASE("binary writer output sinks")
    {
        for (const auto& j : test_values())
        {
-            CAPTURE(j.dump(-1, ' ', false, json::error_handler_t::replace))
+            CAPTURE(j.dump(-1, ' ', false, json::error_handler_t::replace));

            const std::vector<std::uint8_t> expected = json::to_cbor(j);
            std::vector<char> as_char;
@@ -177,7 +177,7 @@ TEST_CASE("binary_reserve_hint never over-reserves")
 {
    for (const auto& j : test_values())
    {
-        CAPTURE(j.dump(-1, ' ', false, json::error_handler_t::replace))
+        CAPTURE(j.dump(-1, ' ', false, json::error_handler_t::replace));

        const std::size_t hint = nlohmann::detail::binary_reserve_hint(j);

@@ -194,7 +194,7 @@ TEST_CASE("binary_reserve_hint never over-reserves")

    for (const auto& j : bson_values())
    {
-        CAPTURE(j.dump())
+        CAPTURE(j.dump());
        CHECK(nlohmann::detail::binary_reserve_hint(j) <= json::to_bson(j).size());
    }

@@ -146,10 +146,10 @@ TEST_CASE_TEMPLATE_DEFINE("value_in_range_of trait", T, value_in_range_of_test)

    INFO("type := ", type_str);

-    CAPTURE(val_min)
-    CAPTURE(min_in_range)
-    CAPTURE(val_max)
-    CAPTURE(max_in_range)
+    CAPTURE(val_min);
+    CAPTURE(min_in_range);
+    CAPTURE(val_max);
+    CAPTURE(max_in_range);

    if (min_in_range)
    {
@@ -2641,7 +2641,7 @@ TEST_CASE("BJData")
                        {"uint8", "int8", "uint16", "int16", "uint32", "int32", "uint64", "int64", "char"
                        })
                {
-                    CAPTURE(type)
+                    CAPTURE(type);
                    const std::string text = std::string(R"({"_ArrayType_":")") + type +
                                             R"(","_ArraySize_":[2,3],"_ArrayData_":[1,2,3,4,5,6]})";
                    const auto from_text = json::to_bjdata(json::parse(text));
@@ -2949,7 +2949,7 @@ TEST_CASE("BJData")
                            R"({"_ArrayType_":"int16","_ArraySize_":[0,2],"_ArrayData_":[]})"
                        })
                {
-                    CAPTURE(text)
+                    CAPTURE(text);
                    const json j = json::parse(text);
                    for (const bool use_size :
                            {
@@ -2983,7 +2983,7 @@ TEST_CASE("BJData")
                            R"({"_ArrayType_":"int16","_ArraySize_":[],"_ArrayData_":null})"
                        })
                {
-                    CAPTURE(text)
+                    CAPTURE(text);
                    const json j = json::parse(text);
                    const auto out = json::to_bjdata(j);
                    CHECK(out.at(0) == '{');
@@ -4317,7 +4317,7 @@ TEST_CASE("BJData and UBJSON can be written to a string")

    for (const auto& j : values)
    {
-        CAPTURE(j.dump())
+        CAPTURE(j.dump());
        for (const bool use_size :
                {
                    false, true
@@ -4332,8 +4332,8 @@ TEST_CASE("BJData and UBJSON can be written to a string")
                {
                    continue;
                }
-                CAPTURE(use_size)
-                CAPTURE(use_type)
+                CAPTURE(use_size);
+                CAPTURE(use_type);

                const auto bjdata = json::to_bjdata(j, use_size, use_type);
                std::string bjdata_string;
@@ -1788,7 +1788,7 @@ TEST_CASE("BSON: deeply nested values")
        json value = "leaf";
        for (std::size_t depth = 0; depth <= 300; ++depth)
        {
-            CAPTURE(depth)
+            CAPTURE(depth);
            const json document = {{"value", value}, {"n", depth}};
            CHECK(json::from_bson(json::to_bson(document)) == document);

@@ -1836,7 +1836,7 @@ value = depth % 2 == 0 ? json{{"a", std::move(value)}, {"b", {1, "x"}}} :
                    false, true
                })
        {
-            CAPTURE(objects)
+            CAPTURE(objects);
            std::string text = "{\"a\":";
            for (std::size_t i = 0; i < depth; ++i)
            {
@@ -17,7 +17,7 @@ TEST_CASE("capacity")
    {
        SECTION("boolean")
        {
-            json j = true;
+            json j = true; // NOLINT(misc-const-correctness)
            const json j_const = true;

            SECTION("result of empty")
@@ -35,7 +35,7 @@ TEST_CASE("capacity")

        SECTION("string")
        {
-            json j = "hello world";
+            json j = "hello world"; // NOLINT(misc-const-correctness)
            const json j_const = "hello world";

            SECTION("result of empty")
@@ -55,7 +55,7 @@ TEST_CASE("capacity")
        {
            SECTION("empty array")
            {
-                json j = json::array();
+                json j = json::array(); // NOLINT(misc-const-correctness)
                const json j_const = json::array();

                SECTION("result of empty")
@@ -73,7 +73,7 @@ TEST_CASE("capacity")

            SECTION("filled array")
            {
-                json j = {1, 2, 3};
+                json j = {1, 2, 3}; // NOLINT(misc-const-correctness)
                const json j_const = {1, 2, 3};

                SECTION("result of empty")
@@ -94,7 +94,7 @@ TEST_CASE("capacity")
        {
            SECTION("empty object")
            {
-                json j = json::object();
+                json j = json::object(); // NOLINT(misc-const-correctness)
                const json j_const = json::object();

                SECTION("result of empty")
@@ -112,7 +112,7 @@ TEST_CASE("capacity")

            SECTION("filled object")
            {
-                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}}; // NOLINT(misc-const-correctness)
                const json j_const = {{"one", 1}, {"two", 2}, {"three", 3}};

                SECTION("result of empty")
@@ -131,7 +131,7 @@ TEST_CASE("capacity")

        SECTION("number (integer)")
        {
-            json j = -23;
+            json j = -23; // NOLINT(misc-const-correctness)
            const json j_const = -23;

            SECTION("result of empty")
@@ -149,7 +149,7 @@ TEST_CASE("capacity")

        SECTION("number (unsigned)")
        {
-            json j = 23u;
+            json j = 23u; // NOLINT(misc-const-correctness)
            const json j_const = 23u;

            SECTION("result of empty")
@@ -167,7 +167,7 @@ TEST_CASE("capacity")

        SECTION("number (float)")
        {
-            json j = 23.42;
+            json j = 23.42; // NOLINT(misc-const-correctness)
            const json j_const = 23.42;

            SECTION("result of empty")
@@ -185,7 +185,7 @@ TEST_CASE("capacity")

        SECTION("null")
        {
-            json j = nullptr;
+            json j = nullptr; // NOLINT(misc-const-correctness)
            const json j_const = nullptr;

            SECTION("result of empty")
@@ -206,7 +206,7 @@ TEST_CASE("capacity")
    {
        SECTION("boolean")
        {
-            json j = true;
+            json j = true; // NOLINT(misc-const-correctness)
            const json j_const = true;

            SECTION("result of size")
@@ -226,7 +226,7 @@ TEST_CASE("capacity")

        SECTION("string")
        {
-            json j = "hello world";
+            json j = "hello world"; // NOLINT(misc-const-correctness)
            const json j_const = "hello world";

            SECTION("result of size")
@@ -248,7 +248,7 @@ TEST_CASE("capacity")
        {
            SECTION("empty array")
            {
-                json j = json::array();
+                json j = json::array(); // NOLINT(misc-const-correctness)
                const json j_const = json::array();

                SECTION("result of size")
@@ -268,7 +268,7 @@ TEST_CASE("capacity")

            SECTION("filled array")
            {
-                json j = {1, 2, 3};
+                json j = {1, 2, 3}; // NOLINT(misc-const-correctness)
                const json j_const = {1, 2, 3};

                SECTION("result of size")
@@ -291,7 +291,7 @@ TEST_CASE("capacity")
        {
            SECTION("empty object")
            {
-                json j = json::object();
+                json j = json::object(); // NOLINT(misc-const-correctness)
                const json j_const = json::object();

                SECTION("result of size")
@@ -311,7 +311,7 @@ TEST_CASE("capacity")

            SECTION("filled object")
            {
-                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}}; // NOLINT(misc-const-correctness)
                const json j_const = {{"one", 1}, {"two", 2}, {"three", 3}};

                SECTION("result of size")
@@ -332,7 +332,7 @@ TEST_CASE("capacity")

        SECTION("number (integer)")
        {
-            json j = -23;
+            json j = -23; // NOLINT(misc-const-correctness)
            const json j_const = -23;

            SECTION("result of size")
@@ -352,7 +352,7 @@ TEST_CASE("capacity")

        SECTION("number (unsigned)")
        {
-            json j = 23u;
+            json j = 23u; // NOLINT(misc-const-correctness)
            const json j_const = 23u;

            SECTION("result of size")
@@ -372,7 +372,7 @@ TEST_CASE("capacity")

        SECTION("number (float)")
        {
-            json j = 23.42;
+            json j = 23.42; // NOLINT(misc-const-correctness)
            const json j_const = 23.42;

            SECTION("result of size")
@@ -392,7 +392,7 @@ TEST_CASE("capacity")

        SECTION("null")
        {
-            json j = nullptr;
+            json j = nullptr; // NOLINT(misc-const-correctness)
            const json j_const = nullptr;

            SECTION("result of size")
@@ -415,7 +415,7 @@ TEST_CASE("capacity")
    {
        SECTION("boolean")
        {
-            json j = true;
+            json j = true; // NOLINT(misc-const-correctness)
            const json j_const = true;

            SECTION("result of max_size")
@@ -427,7 +427,7 @@ TEST_CASE("capacity")

        SECTION("string")
        {
-            json j = "hello world";
+            json j = "hello world"; // NOLINT(misc-const-correctness)
            const json j_const = "hello world";

            SECTION("result of max_size")
@@ -441,7 +441,7 @@ TEST_CASE("capacity")
        {
            SECTION("empty array")
            {
-                json j = json::array();
+                json j = json::array(); // NOLINT(misc-const-correctness)
                const json j_const = json::array();

                SECTION("result of max_size")
@@ -453,7 +453,7 @@ TEST_CASE("capacity")

            SECTION("filled array")
            {
-                json j = {1, 2, 3};
+                json j = {1, 2, 3}; // NOLINT(misc-const-correctness)
                const json j_const = {1, 2, 3};

                SECTION("result of max_size")
@@ -468,7 +468,7 @@ TEST_CASE("capacity")
        {
            SECTION("empty object")
            {
-                json j = json::object();
+                json j = json::object(); // NOLINT(misc-const-correctness)
                const json j_const = json::object();

                SECTION("result of max_size")
@@ -480,7 +480,7 @@ TEST_CASE("capacity")

            SECTION("filled object")
            {
-                json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+                json j = {{"one", 1}, {"two", 2}, {"three", 3}}; // NOLINT(misc-const-correctness)
                const json j_const = {{"one", 1}, {"two", 2}, {"three", 3}};

                SECTION("result of max_size")
@@ -493,7 +493,7 @@ TEST_CASE("capacity")

        SECTION("number (integer)")
        {
-            json j = -23;
+            json j = -23; // NOLINT(misc-const-correctness)
            const json j_const = -23;

            SECTION("result of max_size")
@@ -505,7 +505,7 @@ TEST_CASE("capacity")

        SECTION("number (unsigned)")
        {
-            json j = 23u;
+            json j = 23u; // NOLINT(misc-const-correctness)
            const json j_const = 23u;

            SECTION("result of max_size")
@@ -517,7 +517,7 @@ TEST_CASE("capacity")

        SECTION("number (float)")
        {
-            json j = 23.42;
+            json j = 23.42; // NOLINT(misc-const-correctness)
            const json j_const = 23.42;

            SECTION("result of max_size")
@@ -529,7 +529,7 @@ TEST_CASE("capacity")

        SECTION("null")
        {
-            json j = nullptr;
+            json j = nullptr; // NOLINT(misc-const-correctness)
            const json j_const = nullptr;

            SECTION("result of max_size")
@@ -2931,7 +2931,7 @@ TEST_CASE("Tagged values")
        0xD5, 0xD6, 0xD7
    })
        {
-            CAPTURE(b)
+            CAPTURE(b);

            // add tag to value
            auto v_tagged = v;
@@ -3271,7 +3271,7 @@ TEST_CASE("CBOR large strings and binaries (chunked reader)")
                std::size_t{4097}, std::size_t{8192}, std::size_t{100000}
            })
    {
-        CAPTURE(len)
+        CAPTURE(len);

        // text string
        const json j_string = std::string(len, 'x');
@@ -272,7 +272,7 @@ TEST_CASE("lexer number fast path")
            std::stringstream ss(doc);
            const json b = json::parse(ss);

-            CAPTURE(n)
+            CAPTURE(n);
            CHECK(a == b);
            CHECK(a.dump() == b.dump());
            CHECK(a[0].type() == b[0].type());
@@ -310,7 +310,7 @@ TEST_CASE("lexer number fast path")

        for (const auto& n : numbers)
        {
-            CAPTURE(n)
+            CAPTURE(n);
            const std::string doc = "[" + n + "]";

            const json a = json::parse(doc);   // contiguous fast path
@@ -347,7 +347,7 @@ TEST_CASE("lexer number fast path")
                {"-", "1.", "1e", "1e+", "1.2e", "01", "-01", "1..2", "1.2.3"
                })
        {
-            CAPTURE(bad)
+            CAPTURE(bad);
            // the contiguous fast path must decline and let the byte path report
            const std::string doc = std::string("[") + bad + "]";
            CHECK_FALSE(json::accept(doc));
@@ -415,7 +415,7 @@ TEST_CASE("lexer number fast path")

        // 7 + 49 + 343 + 2401 tokens
        CHECK(tokens.size() == 2401);
-        CAPTURE(mismatches)
+        CAPTURE(mismatches);
        CHECK(mismatches.empty());
    }

@@ -459,7 +459,7 @@ TEST_CASE("lexer number fast path")
                 "[1 \n2]", "[\n1\n2]", "1\n2", "[01\r\n]", "[1e\n]", "[-\n]"
                })
        {
-            CAPTURE(bad)
+            CAPTURE(bad);
            const std::string doc = bad;
            const std::string contiguous_what = contiguous_error(doc);

@@ -576,7 +576,7 @@ TEST_CASE("lexer string fast path")

        // 13 + 169 + 2197 tokens, each at two offsets
        CHECK(tokens.size() == 2197);
-        CAPTURE(mismatches)
+        CAPTURE(mismatches);
        CHECK(mismatches.empty());
    }

@@ -604,7 +604,7 @@ TEST_CASE("lexer string fast path")
                }
            }
        }
-        CAPTURE(mismatches)
+        CAPTURE(mismatches);
        CHECK(mismatches.empty());
    }
 #endif
@@ -649,10 +649,10 @@ TEST_CASE("lexer string fast path")

        for (const auto& test_case : cases)
        {
-            CAPTURE(test_case.description)
+            CAPTURE(test_case.description);
            for (const std::size_t offset : offsets)
            {
-                CAPTURE(offset)
+                CAPTURE(offset);
                const std::string doc = "[\"" + std::string(offset, 'a') + test_case.sequence + "\"]";
                CHECK(json::accept(doc) == test_case.valid);
 #if !defined(JSON_NOEXCEPTION)
@@ -1236,7 +1236,7 @@ TEST_CASE("Eisel-Lemire float conversion")

        for (const auto& c : known)
        {
-            CAPTURE(c.first)
+            CAPTURE(c.first);
            double out = 0;
            if (eisel_lemire(c.first, out))
            {
@@ -1277,7 +1277,7 @@ TEST_CASE("Eisel-Lemire float conversion")
            std::array<char, 64> buffer{};
            const char* end = nlohmann::detail::to_chars(buffer.data(), buffer.data() + buffer.size(), d);
            const std::string token(buffer.data(), static_cast<std::size_t>(end - buffer.data()));
-            CAPTURE(token)
+            CAPTURE(token);
            double out = 0;
            REQUIRE(eisel_lemire(token, out));
            CHECK(bits_of(out) == b);
@@ -1289,7 +1289,7 @@ TEST_CASE("Eisel-Lemire float conversion")
            const std::size_t dot = longer.find('.');
            const std::string extra = dot == std::string::npos ? ".000000000000000000001" : "000000000000000000001";
            longer.insert(e == std::string::npos ? longer.size() : e, extra);
-            CAPTURE(longer)
+            CAPTURE(longer);
            if (eisel_lemire(longer, out))
            {
                CHECK(bits_of(out) == b);
@@ -2561,7 +2561,7 @@ TEST_CASE("last-read diagnostics are identical across input adapters")

    for (const auto& s : inputs)
    {
-        CAPTURE(s)
+        CAPTURE(s);

        // reference: contiguous std::string -> seekable (lazy) path
        const std::string reference = parse_error_message(s);
@@ -2645,7 +2645,7 @@ TEST_CASE("diagnostic positions: value lifetime, input adapters, and SAX")

        SECTION("move constructor resets the moved-from value to npos")
        {
-            // basic_json(basic_json&&) (json.hpp, around line 1951) copies
+            // basic_json(basic_json&&) (json.hpp, around line 1265) copies
            // other's start_position/end_position into *this and then resets
            // other's to npos (see the cppcheck-suppress[accessForwarded]
            // annotation there, which flags this reset as worth a second
@@ -857,7 +857,7 @@ TEST_CASE("equality of objects whose entries have no fixed order")

    for (const std::size_t depth : std::vector<std::size_t> {0, 200})
    {
-        CAPTURE(depth)
+        CAPTURE(depth);

        const unordered_json descending = nest(make_unordered_object(true), depth);
        const unordered_json ascending = nest(make_unordered_object(false), depth);
@@ -909,7 +909,7 @@ TEST_CASE("equality of an object whose comparator treats different keys as equiv

    for (const std::size_t depth : std::vector<std::size_t> {0, 127, 128, 200})
    {
-        CAPTURE(depth)
+        CAPTURE(depth);

        const ci_json x = nest(a, depth);
        const ci_json y = nest(b, depth);
@@ -935,7 +935,7 @@ TEST_CASE("containers are compared element by element")

    for (const std::size_t depth : std::vector<std::size_t> {0, 200})
    {
-        CAPTURE(depth)
+        CAPTURE(depth);

        // objects with different keys
        {
@@ -85,7 +85,7 @@ TEST_CASE("other constructors and destructor")
        CHECK(j.type() == json::value_t::object);
        const json k(std::move(j));
        CHECK(k.type() == json::value_t::object);
-        CHECK(j.type() == json::value_t::null); // NOLINT(bugprone-use-after-move,hicpp-invalid-access-moved) access after move is OK here
+        CHECK(j.type() == json::value_t::null); // NOLINT: access after move is OK here
    }

    SECTION("copy assignment")
@@ -1630,7 +1630,7 @@ TEST_CASE("value conversion")

 enum class cards {kreuz, pik, herz, karo};

-// NOLINTNEXTLINE(misc-use-internal-linkage,misc-const-correctness) - false positive
+// NOLINTNEXTLINE(misc-use-internal-linkage,misc-const-correctness,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) - false positive
 NLOHMANN_JSON_SERIALIZE_ENUM(cards,
 {
    {cards::kreuz, "kreuz"},
@@ -1648,7 +1648,7 @@ enum TaskState // NOLINT(cert-int09-c,readability-enum-initial-value,cppcoreguid
    TS_INVALID = -1,
 };

-// NOLINTNEXTLINE(misc-const-correctness,misc-use-internal-linkage) - false positive
+// NOLINTNEXTLINE(misc-const-correctness,misc-use-internal-linkage,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) - false positive
 NLOHMANN_JSON_SERIALIZE_ENUM(TaskState,
 {
    {TS_INVALID, nullptr},
@@ -1698,7 +1698,7 @@ TEST_CASE("JSON to enum mapping")

 enum class strict_cards {kreuz, pik, herz, karo, andere}; // andere not included in mapping

-// NOLINTNEXTLINE(misc-use-internal-linkage,misc-const-correctness) - false positive
+// NOLINTNEXTLINE(misc-use-internal-linkage,misc-const-correctness,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) - false positive
 NLOHMANN_JSON_SERIALIZE_ENUM_STRICT(strict_cards,
 {
    {strict_cards::kreuz, "kreuz"},
@@ -1717,7 +1717,7 @@ enum StrictTaskState // NOLINT(cert-int09-c,readability-enum-initial-value,cppco
    STRICT_TS_INVALID = -1,
 };

-// NOLINTNEXTLINE(misc-const-correctness,misc-use-internal-linkage) - false positive
+// NOLINTNEXTLINE(misc-const-correctness,misc-use-internal-linkage,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) - false positive
 NLOHMANN_JSON_SERIALIZE_ENUM_STRICT(StrictTaskState,
 {
    {STRICT_TS_INVALID, nullptr},
@@ -191,7 +191,7 @@ TEST_CASE("hash of deeply nested values")
        // every depth on either side of where the iterative path takes over
        for (std::size_t depth = 0; depth <= (2 * nlohmann::detail::recursion_depth_limit()) + 10; ++depth)
        {
-            CAPTURE(depth)
+            CAPTURE(depth);
            const auto arrays = nested<json>(depth, false);
            const auto objects = nested<json>(depth, true);
            const auto ordered = nested<ordered_json>(depth, true);
@@ -212,7 +212,7 @@ TEST_CASE("hash of deeply nested values")
                    false, true
                })
        {
-            CAPTURE(objects)
+            CAPTURE(objects);
            const auto text = nested_text(depth, objects);
            const auto a = json::parse(text);
            const auto b = json::parse(text);
@@ -15,8 +15,65 @@ using nlohmann::json;
 #endif

 #include <fstream>
+#include <string>
+#include <vector>
 #include "make_test_data_available.hpp"

+namespace
+{
+// alternating objects and arrays nested `depth` levels deep, with members that
+// depend on `variant` at some levels, so diffing two variants yields
+// operations on many levels: replacing the innermost value, adding, removing,
+// and (for ordered_json) reordering members, and changing array lengths
+template<typename BasicJsonType>
+BasicJsonType nested(const std::size_t depth, const int variant)
+{
+    BasicJsonType value = variant;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        if (i % 2 == 0)
+        {
+            BasicJsonType object = BasicJsonType::object();
+            if ((i + static_cast<std::size_t>(variant)) % 7 == 0)
+            {
+                object["x"] = i;
+            }
+            if (variant == 2 && i % 11 == 0)
+            {
+                object["z"] = "z";
+            }
+            object["a"] = std::move(value);
+            if (variant == 1 && i % 5 == 0)
+            {
+                object["y"] = 1;
+            }
+            value = std::move(object);
+        }
+        else
+        {
+            BasicJsonType array = BasicJsonType::array({std::move(value)});
+            if ((i + static_cast<std::size_t>(variant)) % 3 == 0)
+            {
+                array.push_back(i);
+            }
+            value = std::move(array);
+        }
+    }
+    return value;
+}
+
+// a path of `depth` reference tokens, as nested() nests its values
+std::string nested_path(const std::size_t depth)
+{
+    std::string path;
+    for (std::size_t i = depth; i > 0; --i)
+    {
+        path += (i - 1) % 2 == 0 ? "/a" : "/0";
+    }
+    return path;
+}
+} // namespace
+
 TEST_CASE("JSON patch")
 {
    SECTION("examples from RFC 6902")
@@ -1752,6 +1809,102 @@ TEST_CASE("JSON patch - diff emits array removals in descending index order")
    }
 }

+TEST_CASE("JSON patch: diff of deeply nested values")
+{
+    SECTION("the diff reproduces the target at every depth")
+    {
+        // depths on either side of the nesting depth up to which diff()
+        // recurses (detail::recursion_depth_limit(), 128); not every depth up
+        // to 300, as the test would then time out under Valgrind
+        std::vector<std::size_t> depths;
+        for (std::size_t depth = 0; depth <= 16; ++depth)
+        {
+            depths.push_back(depth);
+        }
+        for (std::size_t depth = 120; depth <= 136; ++depth)
+        {
+            depths.push_back(depth);
+        }
+        depths.push_back(300);
+
+        for (const auto depth : depths)
+        {
+            CAPTURE(depth);
+            for (int from = 0; from < 3; ++from)
+            {
+                for (int to = 0; to < 3; ++to)
+                {
+                    CAPTURE(from);
+                    CAPTURE(to);
+                    const auto source = nested<json>(depth, from);
+                    const auto target = nested<json>(depth, to);
+                    const auto patch = json::diff(source, target);
+                    CHECK(source.patch(patch) == target);
+                    CHECK(patch.empty() == (from == to));
+
+                    const auto ordered_source = nested<nlohmann::ordered_json>(depth, from);
+                    const auto ordered_target = nested<nlohmann::ordered_json>(depth, to);
+                    CHECK(ordered_source.patch(nlohmann::ordered_json::diff(ordered_source, ordered_target)) == ordered_target);
+                }
+            }
+        }
+    }
+
+    SECTION("a difference only in the innermost value is one replace operation")
+    {
+        for (std::size_t depth = 0; depth <= 300; ++depth)
+        {
+            CAPTURE(depth);
+            json source = 1;
+            json target = 2;
+            for (std::size_t i = 0; i < depth; ++i)
+            {
+                source = i % 2 == 0 ? json::object({{"a", std::move(source)}}) : json::array({std::move(source)});
+                target = i % 2 == 0 ? json::object({{"a", std::move(target)}}) : json::array({std::move(target)});
+            }
+            CHECK(json::diff(source, target, "/root") == json::array({{{"op", "replace"}, {"path", "/root" + nested_path(depth)}, {"value", 2}}}));
+        }
+    }
+
+    SECTION("values nested too deeply for the call stack (#5393)")
+    {
+        // diff() used to recurse once per nesting level, and compared the
+        // values with operator== on every level. The values are only
+        // parsed and diffed, never copied or compared, since those recurse
+        // too.
+        const std::size_t depth = 100000;
+        for (const bool objects :
+                {
+                    false, true
+                })
+        {
+            CAPTURE(objects);
+            std::string source_text;
+            std::string target_text;
+            std::string equal_text;
+            std::string path;
+            for (std::size_t i = 0; i < depth; ++i)
+            {
+                source_text += objects ? "{\"a\":" : "[";
+                path += objects ? "/a" : "/0";
+            }
+            target_text = source_text + "2";
+            equal_text = source_text + "1";
+            source_text += "1";
+            const std::string closing(depth, objects ? '}' : ']');
+            const auto source = json::parse(source_text + closing);
+
+            const auto patch = json::diff(source, json::parse(target_text + closing));
+            REQUIRE(patch.size() == 1);
+            CHECK(patch[0]["op"] == "replace");
+            CHECK(patch[0]["path"] == path);
+            CHECK(patch[0]["value"] == 2);
+
+            CHECK(json::diff(source, json::parse(equal_text + closing)).empty());
+        }
+    }
+}
+
 TEST_CASE("JSON patch - diff() takes the fast path for non-reorderable object types (regression #5639)")
 {
    // #5465 added an order check to diff()'s object handling so a
@@ -1893,7 +2046,7 @@ TEST_CASE("JSON patch - every operation on ordered_json")
        };
        for (const auto& target : targets)
        {
-            CAPTURE(target.dump())
+            CAPTURE(target.dump());
            CHECK(source.patch(ordered_json::diff(source, target)) == target);
        }
    }
@@ -116,7 +116,7 @@ TEST_CASE("tests on deeply nested JSONs")
            // are known to meet cleanly - wherever the bound is set.
            for (std::size_t d = 1; d <= 300; ++d)
            {
-                CAPTURE(d)
+                CAPTURE(d);

                const json array = json::parse(std::string(d, '[') + '0' + std::string(d, ']'));
                const json array_copy(array); // NOLINT(performance-unnecessary-copy-initialization): the copy is what is tested
@@ -286,8 +286,8 @@ TEST_CASE("locale changes between lexer construction and number conversion (#519

    for (const auto& transition : transitions)
    {
-        CAPTURE(transition.first)
-        CAPTURE(transition.second)
+        CAPTURE(transition.first);
+        CAPTURE(transition.second);

        if (std::setlocale(LC_NUMERIC, transition.first) == nullptr)
        {
@@ -365,7 +365,7 @@ TEST_CASE("locale with a multi-byte decimal point")
        {
            continue;
        }
-        CAPTURE(name)
+        CAPTURE(name);
        tested = true;

        // too many significant digits for Clinger's fast path, and an underflow
@@ -305,10 +305,10 @@ TEST_CASE("JSON Merge Patch on deeply nested values")
        // over (detail::recursion_depth_limit(), 128)
        for (std::size_t depth = 0; depth <= 300; ++depth)
        {
-            CAPTURE(depth)
+            CAPTURE(depth);
            for (int variant = 0; variant < 3; ++variant)
            {
-                CAPTURE(variant)
+                CAPTURE(variant);
                const json patch = json::parse(nested_objects(depth, variant));

                json result = json::parse(nested_objects(depth, (variant + 1) % 3));
@@ -1084,10 +1084,10 @@ TEST_CASE("update() on deeply nested values")
        // over (detail::recursion_depth_limit(), 128)
        for (std::size_t depth = 0; depth <= 300; ++depth)
        {
-            CAPTURE(depth)
+            CAPTURE(depth);
            for (int variant = 0; variant < 3; ++variant)
            {
-                CAPTURE(variant)
+                CAPTURE(variant);
                const json source = json::parse(nested_objects(depth, variant));
                json result = json::parse(nested_objects(depth, (variant + 1) % 3));
                json expected = result;
@@ -113,7 +113,7 @@ TEST_CASE("JSON_PRECISE_STREAM_POSITION")

        for (const auto& test : tests)
        {
-            CAPTURE(test.first)
+            CAPTURE(test.first);
            std::istringstream ss(test.first);
            json j;
            ss >> j;
@@ -135,7 +135,7 @@ TEST_CASE("JSON_PRECISE_STREAM_POSITION")

        for (const auto& test : tests)
        {
-            CAPTURE(test.first)
+            CAPTURE(test.first);
            std::istringstream ss(test.first);
            json j;
            ss >> j;
@@ -149,7 +149,7 @@ TEST_CASE("JSON_PRECISE_STREAM_POSITION")
                {"1", "12", "-3.5e2", " 7 "
                })
        {
-            CAPTURE(s)
+            CAPTURE(s);
            std::istringstream ss(s);
            json j;
            ss >> j;
@@ -112,7 +112,7 @@ enum class for_1647
    two
 };

-// NOLINTNEXTLINE(misc-const-correctness): this is a false positive
+// NOLINTNEXTLINE(misc-const-correctness,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays): this is a false positive
 NLOHMANN_JSON_SERIALIZE_ENUM(for_1647,
 {
    {for_1647::one, "one"},
@@ -849,13 +849,13 @@ TEST_CASE("issue #5338 - truncated CBOR tagged binary subtype is rejected")

    for (const auto& data : truncated_tags)
    {
-        CAPTURE(data)
+        CAPTURE(data);
        for (const auto tag_handler :
                {
                    json::cbor_tag_handler_t::ignore, json::cbor_tag_handler_t::store
                })
        {
-            CAPTURE(tag_handler)
+            CAPTURE(tag_handler);
            const auto result = json::from_cbor(data, true, false, tag_handler);
            CHECK(result.is_discarded());
        }
@@ -584,7 +584,7 @@ TEST_CASE("serialization of deeply nested values")
        // value are known to meet cleanly - wherever the bound is set.
        for (std::size_t d = 1; d <= 300; ++d)
        {
-            CAPTURE(d)
+            CAPTURE(d);

            const std::string array_text = std::string(d, '[') + '7' + std::string(d, ']');
            CHECK(json::parse(array_text).dump() == array_text);
@@ -604,7 +604,7 @@ TEST_CASE("serialization of deeply nested values")
    {
        for (std::size_t d = 120; d <= 140; ++d)
        {
-            CAPTURE(d)
+            CAPTURE(d);

            const json j = json::parse(std::string(d, '[') + '7' + std::string(d, ']'));

@@ -629,7 +629,7 @@ TEST_CASE("serialization of deeply nested values")
        // so it must not gain a newline when it is reached iteratively
        for (std::size_t d = 125; d <= 135; ++d)
        {
-            CAPTURE(d)
+            CAPTURE(d);

            const std::string compact = std::string(d, '[') + "[]" + std::string(d, ']');
            CHECK(json::parse(compact).dump() == compact);
@@ -711,10 +711,10 @@ TEST_CASE("serialization of every kind of value below the bound of the descent")

    for (const std::size_t depth : std::vector<std::size_t> {1, 200})
    {
-        CAPTURE(depth)
+        CAPTURE(depth);
        for (const auto& inner : values)
        {
-            CAPTURE(inner.dump())
+            CAPTURE(inner.dump());
            const json j = wrap_in_arrays(inner, depth);
            CHECK(j.dump() == std::string(depth, '[') + inner.dump() + std::string(depth, ']'));
            CHECK(j.dump(2) == expected_pretty_in_arrays(inner, depth));
@@ -725,7 +725,7 @@ TEST_CASE("serialization of every kind of value below the bound of the descent")
    {
        for (std::size_t d = 120; d <= 140; ++d)
        {
-            CAPTURE(d)
+            CAPTURE(d);

            // built from the inside out: {"k": <level below>, "n": <level>}
            json j = 7;
@@ -350,7 +350,7 @@ TEST_CASE("std::counted_iterator reaches the contiguous fast paths")

    for (const auto& text : diagnostic_docs)
    {
-        CAPTURE(text)
+        CAPTURE(text);
        const std::counted_iterator<const char*> it(text.data(), static_cast<std::iter_difference_t<const char*>>(text.size()));
        std::string counted_message;
        std::string string_message;
@@ -460,8 +460,8 @@ TEST_CASE("std::counted_iterator bulk scanning stops at the counted end")

    for (const auto& tc : cases)
    {
-        CAPTURE(tc.buffer)
-        CAPTURE(tc.count)
+        CAPTURE(tc.buffer);
+        CAPTURE(tc.count);
        const std::string buffer = tc.buffer;
        CHECK(via_counted(buffer, tc.count) == via_prefix(buffer, tc.count));
    }
Author	SHA1	Message	Date
Niels Lohmann	795ce4e4a7	Merge branch 'develop' into claude/iterative-diff Conflicts: - include/nlohmann/json.hpp: kept the PR's diff_recursively()/ diff_object_keys() split and re-applied develop's #5691 (fast path for every object type except an insertion-ordered one; target key order only tracked for such types) inside diff_object_keys(), so both the recursive and the iterative walk get it - single_include/nlohmann/json.hpp: regenerated with make amalgamate - tests/src/unit-json_patch.cpp: kept both new test cases (deeply nested diff from the PR, #5639 regression from develop) Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-30 20:36:43 +02:00
Niels Lohmann	90f85d6d75	Merge branch 'develop' into claude/iterative-diff Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 20:58:06 +02:00
Niels Lohmann	4aaeb01ea4	Merge remote-tracking branch 'origin/develop' into claude/iterative-diff Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 17:16:01 +02:00
Niels Lohmann	2038838eea	Copy the diff frame's members instead of holding a reference to it The loop in diff_iteratively held a reference to the top frame, which enter() invalidates when it pushes and the end of the loop invalidates when it pops. Nothing used it afterwards, but a later change could. As in the other iterative walks, the members the loop reads are now copied out as constants and the ones it advances are changed through stack.back(). The frame as a whole is not copied: it holds the common keys and the "add" operations of an object. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 14:00:04 +02:00
Niels Lohmann	aa5084d713	Keep diff()'s recursive levels small and its result elided diff_recursively built every patch operation in place from initializer lists. Unoptimized builds give each of those temporaries its own stack slot, so every level of the bounded descent cost kilobytes of stack (about 6 KB with clang -O0), and the 128 recursive levels overflowed the 1 MB stack of MSVC Debug in the "deeply nested values" test. The operations and the key comparison of two objects are now built by separate functions, which diff_iteratively shares, and both diff functions append to one result instead of returning a patch per level that the caller copies. With clang -O0, diffing values nested 300 levels deep now peaks at about 190 KB of stack instead of 880 KB. Since diff() now owns the only returned value, clang's -Wnrvo no longer reports the returns of diff_recursively, which alternated between the local patch and diff_iteratively's result. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-26 07:49:42 +02:00
Niels Lohmann	33c4dfdc18	Note that the diff frame reference is invalidated by pop_back() too Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-26 07:46:43 +02:00
Niels Lohmann	b41e43fffc	Bound diff()'s descent with a depth count instead of scanning the source Now that operator== no longer recurses (#5390), diff() can keep its per-level equality shortcut all the way down. It diffs recursively for the first detail::recursion_depth_limit() levels, as merge_patch() does, and hands anything deeper to diff_iteratively(). The nesting_exceeds() scan, which cost about 30% on equal documents, is gone, and diff() is on par with develop again. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-25 22:23:57 +02:00
Niels Lohmann	958e0a906b	Merge remote-tracking branch 'origin/develop' into claude/iterative-diff	2026-09-25 22:19:57 +02:00
Niels Lohmann	49f038b86a	Merge branch 'develop' into claude/iterative-diff Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-25 20:22:45 +02:00
Niels Lohmann	722c2bb561	Merge branch 'develop' into claude/iterative-diff Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-25 18:06:10 +02:00
Niels Lohmann	f41296276c	Mark the diff frame's value-initialized members for clang-tidy The braces are kept for GCC's -Weffc++, as in json_sax.hpp. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-25 18:06:10 +02:00
Niels Lohmann	481b8d17fa	Merge branch 'develop' into claude/iterative-diff Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-25 08:24:38 +02:00
Niels Lohmann	484f644b86	Diff fewer nesting depths so the test does not time out under Valgrind Checking every depth up to 300 made test-json_patch exceed the 1500 s ctest timeout in ci_test_valgrind. Check the depths up to 16, those around the recursion limit of 128, and 300 instead. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-25 08:21:38 +02:00
Niels Lohmann	08e30eca78	Use the shared recursion limit in diff() diff_depth_limit() is gone in favor of detail::recursion_depth_limit(). Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-24 17:12:07 +02:00
Niels Lohmann	582223eb8a	Make diff_frame a member struct that declares its special members GCC's -Weffc++ (an error in CI) asks a class with pointer members, a user constructor and a non-trivial destructor to declare its copy constructor and copy assignment; diff_frame's vector and basic_json members make its destructor non-trivial. Declare all five as defaulted, which also satisfies clang-tidy's special-member-functions check. Leave their exception specifications implicit: GCC 4.8 rejects an explicit one that differs from the implicit one, as it does for flatten_task in #5517. The converting constructor cannot throw, and is now declared noexcept for GCC's -Wnoexcept, which flags the emplace_back() under C++26 otherwise. The struct also moves from diff_iteratively() into the class, like dump_frame in the serializer. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-24 17:12:07 +02:00
Niels Lohmann	c14208a8e0	Diff deeply nested values without recursing per nesting level diff() descended into both values once per nesting level, and compared them with operator== on every level on the way, which recurses as well. Values nested deeply enough - 25,000 levels on an 8 MiB stack - exhausted the call stack and terminated the process, although parse() accepts them without complaint. On such a chain the per-level comparisons and path strings also made diff() quadratic in time and memory. Both the recursion and operator== only descend as far as the source is nested. So diff() first checks, recursing at most diff_depth_limit() (128) levels, whether the source is nested more deeply than that. If not - all but a vanishing minority of values - the recursive algorithm diffs it exactly as before, now as diff_recursively(). Otherwise diff_iteratively() walks the two values on an explicit stack, emitting the same operations in the same order. It does not compare arrays and objects with operator== up front (equal ones yield no operations anyway), keeps the path in one buffer instead of a new string per level, and hands every subtree that is not nested too deeply back to diff_recursively(), so equal parts are still skipped quickly. The check costs one pass over the source. On a 3,000-object document that is about 30% of diffing two equal values (which is just an operator== call), about 10% of diffing values that differ in a few places, and noise when arrays change length. Once operator== no longer recurses (#5390), the check can go. Tests check that the patch reproduces the target at every depth up to 300, for json and ordered_json, including reordered members. They also check the exact operation for a difference deep inside, and diff values nested 100,000 levels deep. Fixes #5393 for diff(). Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-24 17:12:07 +02:00