Use MSVC intrinsics for full multiplication (#5782)

* Use MSVC intrinsics for full multiplication

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

* Fix formatting in unit-class_lexer

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

* Address review feedback

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

---------

Signed-off-by: Suyog Verma <suyogverma0057@gmail.com>

.github/workflows/ubuntu.yml

@@ -31,6 +31,51 @@ jobs:
       - name: Build
         run: cmake --build build --target ci_test_gcc
 
+  ci_meson_install:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
+      - name: Check that Meson and pkg-config offer the CMake options
+        run: make check_build_options
+      - name: Install Meson
+        run: pip install meson
+      - name: Install with Meson
+        run: |
+          meson setup build-meson --prefix=${{ github.workspace }}/install
+          meson install -C build-meson
+      - name: Use the installed package with find_package
+        run: |
+          cmake -S tests/cmake_import/project -B build-import -DCMAKE_PREFIX_PATH=${{ github.workspace }}/install
+          cmake --build build-import
+      - name: Install with Meson and non-default options
+        run: |
+          meson setup build-meson-options --prefix=${{ github.workspace }}/install-options -DMultipleHeaders=true -DDiagnostics=true -DGlobalUDLs=false -DDisableTupleReferenceConversion=true -DStrictBinaryUTF8=true -DDeleteDeprecatedFunctions=true
+          meson install -C build-meson-options
+      - name: Check that the options reach the installed files
+        run: |
+          test -d install-options/include/nlohmann/detail
+          cflags=$(PKG_CONFIG_PATH=${{ github.workspace }}/install-options/share/pkgconfig pkg-config --cflags nlohmann_json)
+          echo "$cflags"
+          echo "$cflags" | grep -q -- '-DJSON_DIAGNOSTICS=1'
+          echo "$cflags" | grep -q -- '-DJSON_USE_GLOBAL_UDLS=0'
+          echo "$cflags" | grep -q -- '-DJSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1'
+          echo "$cflags" | grep -q -- '-DJSON_STRICT_BINARY_UTF8=1'
+          echo "$cflags" | grep -q -- '-DJSON_DELETE_DEPRECATED_FUNCTIONS=1'
+          grep -q 'JSON_USE_GLOBAL_UDLS=0;JSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1;JSON_DIAGNOSTICS=1' install-options/share/cmake/nlohmann_json/nlohmann_jsonTargets.cmake
+          grep -q 'JSON_STRICT_BINARY_UTF8=1;JSON_DELETE_DEPRECATED_FUNCTIONS=1' install-options/share/cmake/nlohmann_json/nlohmann_jsonTargets.cmake
+          cmake -S tests/cmake_import/project -B build-import-options -DCMAKE_PREFIX_PATH=${{ github.workspace }}/install-options
+          cmake --build build-import-options
+      - name: Install with Meson and the include directory outside the prefix
+        run: |
+          meson setup build-meson-split --prefix=${{ github.workspace }}/install-split --includedir=${{ github.workspace }}/install-split-dev/include
+          meson install -C build-meson-split
+          cmake -S tests/cmake_import/project -B build-import-split -DCMAKE_PREFIX_PATH=${{ github.workspace }}/install-split
+          cmake --build build-import-split
+
   ci_infer:
     runs-on: ubuntu-latest
     steps:

CMakeLists.txt

@@ -189,7 +189,39 @@ if (MSVC)
     )
 endif()
 
-# Install a pkg-config file, so other tools can find this.
+# Install a pkg-config file, so other tools can find this. It carries the same
+# compile definitions as the target above.
+set(NLOHMANN_JSON_PKGCONFIG_CFLAGS "")
+if (NOT JSON_GlobalUDLs)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_USE_GLOBAL_UDLS=0")
+endif()
+if (NOT JSON_ImplicitConversions)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_USE_IMPLICIT_CONVERSIONS=0")
+endif()
+if (JSON_DisableEnumSerialization)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_DISABLE_ENUM_SERIALIZATION=1")
+endif()
+if (JSON_DisableTupleReferenceConversion)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1")
+endif()
+if (JSON_Diagnostics)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_DIAGNOSTICS=1")
+endif()
+if (JSON_Diagnostic_Positions)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_DIAGNOSTIC_POSITIONS=1")
+endif()
+if (JSON_LegacyDiscardedValueComparison)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1")
+endif()
+if (JSON_StrictNulHandling)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_STRICT_NUL_HANDLING=1")
+endif()
+if (JSON_StrictBinaryUTF8)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_STRICT_BINARY_UTF8=1")
+endif()
+if (JSON_DeleteDeprecatedFunctions)
+    string(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -DJSON_DELETE_DEPRECATED_FUNCTIONS=1")
+endif()
 configure_file(
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake/pkg-config.pc.in"
     "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.pc"

FILES.md

@@ -249,9 +249,31 @@ make BUILD.bazel
 
 The "Check amalgamation" workflow fails if the file is out of date.
 
-### `meson.build`
+### `meson.build` and `meson_options.txt`
 
-The build definition for the [Meson](https://mesonbuild.com) build system.
+Meson build definitions suitable for use as a subproject ("wrap" in Meson terminology).
+
+Projects wishing to use the wrap can execute:
+```sh
+meson wrap install nlohmann_json
+```
+
+Which allows Meson to build from source when a system provided dependency isn't available.
+
+To build directly:
+```sh
+meson setup builddir
+ninja -C builddir
+```
+
+`meson_options.txt` defines the options, which mirror the CMake options that change the library's target (for example,
+`-DDiagnostics=true`). Meson requires this file next to `meson.build`, so it is also part of `include.zip`. `make check_build_options`
+([`tools/check_build_options`](tools/check_build_options/README.md)) checks in CI that both files and the pkg-config files
+stay in sync with the CMake options.
+
+When installing, `meson.build` installs the headers, a pkg-config file, and the CMake package config files, so that
+`find_package(nlohmann_json)` works. As Meson cannot generate `nlohmann_jsonTargets.cmake` itself, it is created from
+the template `cmake/nlohmann_jsonTargets.cmake.in`, which is only used by Meson.
 
 ### `Package.swift`
 

Makefile

@@ -1,4 +1,4 @@
-.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel natvis macro_builder_check
+.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel natvis macro_builder_check check_build_options
 
 ##########################################################################
 # configuration
@@ -127,6 +127,10 @@ macro_builder_check:
 	diff "$$TMPDIR/paste.hpp" "$$TMPDIR/paste_actual.hpp" || (echo "===================================================================\n  $(MACRO_SCOPE_HPP) (NLOHMANN_JSON_EXPAND..NLOHMANN_JSON_DOUBLE_PASTE63) is out of date!\n  Regenerate it, see tools/macro_builder/README.md.\n===================================================================" ; exit 1); \
 	diff "$$TMPDIR/type_body.hpp" "$$TMPDIR/type_body_actual.hpp" || (echo "===================================================================\n  $(MACRO_SCOPE_HPP) (NLOHMANN_JSON_TYPE_BODY) is out of date!\n  Regenerate it, see tools/macro_builder/README.md.\n===================================================================" ; exit 1)
 
+# check that the Meson build and the pkg-config files offer the options of the CMake target
+check_build_options:
+	python3 tools/check_build_options/check_build_options.py .
+
 # check if file single_include/nlohmann/json.hpp has been amalgamated from the nlohmann sources
 check-amalgamation:
 	@mv $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~
@@ -184,7 +188,7 @@ json.tar.xz:
 # We use `-X` to make the resulting ZIP file reproducible, see
 # <https://content.pivotal.io/blog/barriers-to-deterministic-reproducible-zip-files>.
 include.zip: BUILD.bazel
-	zip -9 --recurse-paths -X include.zip $(SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) BUILD.bazel MODULE.bazel meson.build LICENSE.MIT
+	zip -9 --recurse-paths -X include.zip $(SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) BUILD.bazel MODULE.bazel meson.build meson_options.txt LICENSE.MIT
 
 # Create the files for a release and add signatures and hashes.
 release: include.zip json.tar.xz

cmake/nlohmann_jsonTargets.cmake.in

@@ -0,0 +1,42 @@
+# Imported target for installations made with Meson (see meson.build).
+#
+# CMake installations generate this file with install(EXPORT ...). Meson cannot
+# do that, but as the library is header-only, the target only needs an include
+# directory, the C++ standard, and the compile definitions of the options that
+# differ from their defaults. Paths are computed relative to this file so that
+# the installation can be relocated (e.g., into a sysroot), unless includedir or
+# datadir is outside the prefix.
+
+if(TARGET @PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@)
+    return()
+endif()
+
+get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_CONFIG_TO_PREFIX@" ABSOLUTE)
+# As in CMake's generated file: avoid "//include" for an installation to "/".
+if(_IMPORT_PREFIX STREQUAL "/")
+    set(_IMPORT_PREFIX "")
+endif()
+
+add_library(@PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@ INTERFACE IMPORTED)
+set_target_properties(@PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@ PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "@NLOHMANN_JSON_INCLUDE_DIR@"
+)
+if(CMAKE_VERSION VERSION_LESS 3.8)
+    set_target_properties(@PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@ PROPERTIES
+        INTERFACE_COMPILE_FEATURES cxx_range_for
+    )
+else()
+    set_target_properties(@PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@ PROPERTIES
+        INTERFACE_COMPILE_FEATURES cxx_std_11
+    )
+endif()
+
+set(_NLOHMANN_JSON_COMPILE_DEFINITIONS "@NLOHMANN_JSON_COMPILE_DEFINITIONS@")
+if(_NLOHMANN_JSON_COMPILE_DEFINITIONS)
+    set_target_properties(@PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@ PROPERTIES
+        INTERFACE_COMPILE_DEFINITIONS "${_NLOHMANN_JSON_COMPILE_DEFINITIONS}"
+    )
+endif()
+
+unset(_NLOHMANN_JSON_COMPILE_DEFINITIONS)
+unset(_IMPORT_PREFIX)

cmake/pkg-config.pc.in

@@ -4,4 +4,4 @@ includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
 Name: @PROJECT_NAME@
 Description: JSON for Modern C++
 Version: @PROJECT_VERSION@
-Cflags: -I${includedir}
+Cflags: -I${includedir}@NLOHMANN_JSON_PKGCONFIG_CFLAGS@

docs/mkdocs/docs/community/roadmap.md

@@ -36,26 +36,13 @@ work items are tracked in the [GitHub milestones](https://github.com/nlohmann/js
 ## API stability
 
 Releases follow [semantic versioning](https://semver.org): a minor or patch release of version 3.x does not break code
-that uses the public API, unless that code opts in to a change with a macro as described [below](#version-40). In
-particular, a 3.x release does not:
+that uses the public API. In particular, a 3.x release does not:
 
-- make breaking changes to the signature of a function: the types or order of its existing parameters, its return type,
-  its `noexcept` or `constexpr` specifier, or the const-ness of a member function. New parameters may be added if they
-  have a default value;
-- remove or rename a function or class, or change the template parameters of a public class template;
+- change the signature of a function (its parameter types, return type, number of parameters, or the const-ness of a
+  member function);
+- remove or rename a function or class;
 - change which exceptions a function throws, or the [exception ids](../home/exceptions.md);
-- change access specifiers, or change or remove existing default arguments. New default arguments may be added;
-- change the JSON type that a valid input parses to, or the text that `dump()` produces for a valid value;
-- accept input that was rejected before, or reject input that was accepted before;
-- change the order in which the keys of an object are iterated. The default type sorts keys, and
-  [`ordered_json`](../api/ordered_json.md) keeps insertion order;
-- change when iterators, pointers, or references are invalidated, or the state of a moved-from `basic_json`;
-- add or remove implicit conversions from `basic_json`;
-- change how `to_json` and `from_json` functions are found, or the behavior of
-  [`adl_serializer`](../api/adl_serializer/index.md);
-- add pure virtual functions to the [`json_sax`](../api/json_sax/index.md) interface;
-- remove, rename, renumber, or add enumerators of `value_t`;
-- remove or rename a documented macro, CMake option, CMake target, or header, or change what a documented macro does.
+- change access specifiers or default arguments.
 
 Exceptions to these rules, for instance when fixing a bug requires changing the exception a function throws, are
 documented in the [release notes](../home/releases.md).
@@ -64,14 +51,13 @@ The following are **not** part of the public API and may change in any release,
 
 - The text of exception messages returned by `what()`. Use the [exception id](../home/exceptions.md) to tell errors
   apart.
-- The ABI, including `sizeof(basic_json)` and the memory layout of its values. The
-  [versioned inline namespace](../features/namespace.md) turns mixing versions into a link error.
-- The hash values returned by `std::hash` for `basic_json`. Numbers that compare equal still hash equally.
+- The ABI, including `sizeof(basic_json)` and the memory layout of its values. Recompile your code when you upgrade the
+  library. The [versioned inline namespace](../features/namespace.md) turns mixing versions into a link error.
 - Everything in namespace `nlohmann::detail`, and macros and type traits that are not documented in the
   [API reference](../api/basic_json/index.md).
 
-Breaking changes are only added behind a macro whose default keeps the 3.x behavior. See [Version 4.0](#version-40) and
-the [macro overview](../features/macros.md).
+Changes that would break the public API are only added behind a macro whose default keeps the 3.x behavior, see
+[Version 4.0](#version-40).
 
 ## Version 4.0
 

docs/mkdocs/docs/integration/package_managers.md

@@ -125,10 +125,24 @@ meson wrap install nlohmann_json
 Please see the Meson project for any issues regarding the packaging.
 
 The provided `meson.build` can also be used as an alternative to CMake for installing `nlohmann_json` system-wide in
-which case a [pkg-config](pkg-config.md) file is installed. To use it, have your build system require the
-`nlohmann_json` pkg-config dependency. In Meson, it is preferred to use the
-[`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than
-using the subproject directly.
+which case a [pkg-config](pkg-config.md) file and the CMake package config files are installed. To use it, have your build system require
+the `nlohmann_json` pkg-config dependency, or use [`find_package(nlohmann_json)`](cmake.md#external) in CMake. In Meson,
+it is preferred to use the [`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a
+subproject fallback, rather than using the subproject directly.
+
+The options that change the library's configuration are available in Meson as well, named like the
+[CMake options](cmake.md#cmake-options) without the `JSON_` prefix: `MultipleHeaders`, `GlobalUDLs`,
+`ImplicitConversions`, `DisableEnumSerialization`, `DisableTupleReferenceConversion`, `Diagnostics`,
+`Diagnostic_Positions`, `LegacyDiscardedValueComparison`, `StrictNulHandling`, `StrictBinaryUTF8`, and
+`DeleteDeprecatedFunctions`. They have the same defaults as in CMake, except that
+`MultipleHeaders` is `false`. Set them with `-D` when setting up the build, or with the subproject name as prefix when
+the library is used as a subproject:
+
+```shell
+meson setup build -Dnlohmann_json:Diagnostics=true
+```
+
+The resulting compile definitions are part of the Meson dependency, the pkg-config file, and the CMake target.
 
 ??? example "Example: Wrap"
 

include/nlohmann/detail/bit_ops.hpp

@@ -9,12 +9,15 @@
 #pragma once
 
 #include <cstdint> // uint64_t
+#if !defined(__SIZEOF_INT128__) && defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    #include <intrin0.h> // __umulh, _umul128
+#endif
 
 #include <nlohmann/detail/abi_macros.hpp>
 
 // Portable bit-level helpers for the number and string scanners. They use
-// compiler builtins where available and plain C++ otherwise, so they need no
-// platform headers and work regardless of byte order.
+// compiler builtins or platform-specific intrinsics where available and plain
+// C++ otherwise, so they work regardless of byte order.
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -52,6 +55,12 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
     __extension__ using uint128 = unsigned __int128;
     const uint128 r = static_cast<uint128>(a) * b;
     return {static_cast<std::uint64_t>(r), static_cast<std::uint64_t>(r >> 64u)};
+#elif defined(_MSC_VER) && defined(_M_X64)
+    std::uint64_t high = 0;
+    const std::uint64_t low = _umul128(a, b, &high);
+    return {low, high};
+#elif defined(_MSC_VER) && defined(_M_ARM64)
+    return {a * b, __umulh(a, b)};
 #else
     const std::uint64_t a_lo = a & 0xFFFFFFFFu;
     const std::uint64_t a_hi = a >> 32u;

meson.build

@@ -2,24 +2,120 @@ project('nlohmann_json',
     'cpp',
     version : '3.12.0',
     license : 'MIT',
+    meson_version : '>= 0.64',
+    default_options: ['cpp_std=c++11'],
 )
 
+if get_option('MultipleHeaders')
+    incdir = 'include'
+else
+    incdir = 'single_include'
+endif
+
+# The same compile definitions as the CMake target (see target_compile_definitions
+# in CMakeLists.txt): only an option that differs from its default adds one.
+json_defines = []
+if not get_option('GlobalUDLs')
+    json_defines += 'JSON_USE_GLOBAL_UDLS=0'
+endif
+if not get_option('ImplicitConversions')
+    json_defines += 'JSON_USE_IMPLICIT_CONVERSIONS=0'
+endif
+if get_option('DisableEnumSerialization')
+    json_defines += 'JSON_DISABLE_ENUM_SERIALIZATION=1'
+endif
+if get_option('DisableTupleReferenceConversion')
+    json_defines += 'JSON_DISABLE_TUPLE_REFERENCE_CONVERSION=1'
+endif
+if get_option('Diagnostics')
+    json_defines += 'JSON_DIAGNOSTICS=1'
+endif
+if get_option('Diagnostic_Positions')
+    json_defines += 'JSON_DIAGNOSTIC_POSITIONS=1'
+endif
+if get_option('LegacyDiscardedValueComparison')
+    json_defines += 'JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1'
+endif
+if get_option('StrictNulHandling')
+    json_defines += 'JSON_STRICT_NUL_HANDLING=1'
+endif
+if get_option('StrictBinaryUTF8')
+    json_defines += 'JSON_STRICT_BINARY_UTF8=1'
+endif
+if get_option('DeleteDeprecatedFunctions')
+    json_defines += 'JSON_DELETE_DEPRECATED_FUNCTIONS=1'
+endif
+
+cpp_args = []
+foreach define : json_defines
+    cpp_args += '-D' + define
+endforeach
+
 nlohmann_json_dep = declare_dependency(
-    include_directories: include_directories('single_include')
+    compile_args: cpp_args,
+    include_directories: include_directories(incdir)
 )
+meson.override_dependency('nlohmann_json', nlohmann_json_dep)
 
+# The multi-header version under the name earlier versions of this file used
 nlohmann_json_multiple_headers = declare_dependency(
+    compile_args: cpp_args,
     include_directories: include_directories('include')
 )
 
 if not meson.is_subproject()
-install_headers('single_include/nlohmann/json.hpp', subdir: 'nlohmann')
-install_headers('single_include/nlohmann/json_fwd.hpp', subdir: 'nlohmann')
-install_headers('single_include/nlohmann/json_literals.hpp', subdir: 'nlohmann')
+    install_subdir(
+        incdir / 'nlohmann',
+        install_dir: get_option('includedir'),
+        install_tag: 'devel',
+    )
 
-pkgc = import('pkgconfig')
-pkgc.generate(name: 'nlohmann_json',
-    version: meson.project_version(),
-    description: 'JSON for Modern C++'
-)
+    pkgc = import('pkgconfig')
+    pkgc.generate(name: 'nlohmann_json',
+        version: meson.project_version(),
+        description: 'JSON for Modern C++',
+        extra_cflags: cpp_args,
+        install_dir: get_option('datadir') / 'pkgconfig',
+    )
+
+    # CMake package config files, so that find_package(nlohmann_json) works. The
+    # include directory is given relative to the config files, so that the
+    # installation can be relocated. This is not possible if includedir or datadir
+    # is an absolute path outside the prefix (e.g., with the separate outputs of
+    # Nix); then the absolute include directory is used, as CMake does.
+    fs = import('fs')
+    cmake_install_dir = get_option('datadir') / 'cmake' / meson.project_name()
+    cmake_to_prefix = []
+    if fs.is_absolute(get_option('includedir')) or fs.is_absolute(cmake_install_dir)
+        cmake_include_dir = (get_option('prefix') / get_option('includedir')).replace('\\', '/')
+    else
+        foreach component : cmake_install_dir.split('/')
+            cmake_to_prefix += '..'
+        endforeach
+        cmake_include_dir = '${_IMPORT_PREFIX}/' + get_option('includedir')
+    endif
+
+    cmake_conf = configuration_data()
+    cmake_conf.set('PROJECT_NAME', meson.project_name())
+    cmake_conf.set('PROJECT_VERSION', meson.project_version())
+    cmake_conf.set('PROJECT_VERSION_MAJOR', meson.project_version().split('.')[0])
+    cmake_conf.set('NLOHMANN_JSON_TARGET_NAME', meson.project_name())
+    cmake_conf.set('NLOHMANN_JSON_TARGETS_EXPORT_NAME', meson.project_name() + 'Targets')
+    cmake_conf.set('NLOHMANN_JSON_INCLUDE_DIR', cmake_include_dir)
+    cmake_conf.set('NLOHMANN_JSON_CONFIG_TO_PREFIX', '/'.join(cmake_to_prefix))
+    cmake_conf.set('NLOHMANN_JSON_COMPILE_DEFINITIONS', ';'.join(json_defines))
+
+    foreach cmake_file : [
+        ['cmake/config.cmake.in', 'nlohmann_jsonConfig.cmake'],
+        ['cmake/nlohmann_jsonConfigVersion.cmake.in', 'nlohmann_jsonConfigVersion.cmake'],
+        ['cmake/nlohmann_jsonTargets.cmake.in', 'nlohmann_jsonTargets.cmake'],
+    ]
+        configure_file(
+            input: cmake_file[0],
+            output: cmake_file[1],
+            configuration: cmake_conf,
+            format: 'cmake@',
+            install_dir: cmake_install_dir,
+        )
+    endforeach
 endif

meson_options.txt

@@ -0,0 +1,66 @@
+option(
+    'MultipleHeaders',
+    type: 'boolean',
+    value: false,
+    description: 'Use non-amalgamated version of the library',
+)
+option(
+    'GlobalUDLs',
+    type: 'boolean',
+    value: true,
+    description: 'Place user-defined string literals in the global namespace',
+)
+option(
+    'ImplicitConversions',
+    type: 'boolean',
+    value: true,
+    description: 'Enable implicit conversions',
+)
+option(
+    'DisableEnumSerialization',
+    type: 'boolean',
+    value: false,
+    description: 'Disable default integer enum serialization',
+)
+option(
+    'DisableTupleReferenceConversion',
+    type: 'boolean',
+    value: false,
+    description: 'Disable conversion from a one-element tuple of a JSON reference',
+)
+option(
+    'Diagnostics',
+    type: 'boolean',
+    value: false,
+    description: 'Use extended diagnostic messages',
+)
+option(
+    'Diagnostic_Positions',
+    type: 'boolean',
+    value: false,
+    description: 'Enable diagnostic positions',
+)
+option(
+    'LegacyDiscardedValueComparison',
+    type: 'boolean',
+    value: false,
+    description: 'Enable legacy discarded value comparison',
+)
+option(
+    'StrictNulHandling',
+    type: 'boolean',
+    value: false,
+    description: 'Enable strict NUL-byte handling',
+)
+option(
+    'StrictBinaryUTF8',
+    type: 'boolean',
+    value: false,
+    description: 'Enable UTF-8 checks in the CBOR, UBJSON, BJData, and BSON writers',
+)
+option(
+    'DeleteDeprecatedFunctions',
+    type: 'boolean',
+    value: false,
+    description: 'Delete the deprecated functions instead of only deprecating them',
+)

single_include/nlohmann/json.hpp

@@ -8791,13 +8791,16 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 #include <cstdint> // uint64_t
+#if !defined(__SIZEOF_INT128__) && defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    #include <intrin0.h> // __umulh, _umul128
+#endif
 
 // #include <nlohmann/detail/abi_macros.hpp>
 
 
 // Portable bit-level helpers for the number and string scanners. They use
-// compiler builtins where available and plain C++ otherwise, so they need no
-// platform headers and work regardless of byte order.
+// compiler builtins or platform-specific intrinsics where available and plain
+// C++ otherwise, so they work regardless of byte order.
 
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -8835,6 +8838,12 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
     __extension__ using uint128 = unsigned __int128;
     const uint128 r = static_cast<uint128>(a) * b;
     return {static_cast<std::uint64_t>(r), static_cast<std::uint64_t>(r >> 64u)};
+#elif defined(_MSC_VER) && defined(_M_X64)
+    std::uint64_t high = 0;
+    const std::uint64_t low = _umul128(a, b, &high);
+    return {low, high};
+#elif defined(_MSC_VER) && defined(_M_ARM64)
+    return {a * b, __umulh(a, b)};
 #else
     const std::uint64_t a_lo = a & 0xFFFFFFFFu;
     const std::uint64_t a_hi = a >> 32u;

tests/CMakeLists.txt

@@ -138,8 +138,7 @@ json_test_set_test_options(test-disabled_exceptions
 # only the #972 regression test needs thirdparty/fifo_map on its include path
 json_test_set_test_options(test-regression1 LINK_LIBRARIES fifo_map_include)
 
-# Regression test for GCC's false -Warray-bounds error with JSON_DIAGNOSTICS (#5742, fixed in #5585). It only
-# showed up when optimizing, so build this test with -O3 and the warning as an error.
+# GCC's false -Warray-bounds error with JSON_DIAGNOSTICS only shows up when optimizing (#5742).
 # -O3 makes the optimizer-driven warnings of the ci_test_gcc flag set (-Winline,
 # -Wsuggest-attribute=...) fire on the library's inline functions; they are not
 # what this test checks, so turn them off for it.

tests/src/unit-class_lexer.cpp

@@ -17,6 +17,7 @@ using nlohmann::json;
 #include <cstdint> // uint32_t, uint64_t
 #include <cstdlib> // strtod
 #include <cstring> // memcpy
+#include <limits> // numeric_limits
 #include <sstream> // stringstream
 #include <string> // string
 #include <utility> // pair
@@ -891,8 +892,39 @@ TEST_CASE("Eisel-Lemire float conversion")
 
     SECTION("128-bit products and leading zeros")
     {
+        const auto check_product = [](std::uint64_t a, std::uint64_t b)
+        {
+            const auto product = nlohmann::detail::full_multiplication(a, b);
+            CHECK(big_from(product.high, product.low) == big_mul(big_from(0, a), big_from(0, b)));
+        };
+
+        const std::uint64_t max = (std::numeric_limits<std::uint64_t>::max)();
+        const std::array<std::pair<std::uint64_t, std::uint64_t>, 13> edge_cases =
+        {
+            {
+                {0, 0},
+                {0, 1},
+                {1, 1},
+                {1, max},
+                {0xFFFFFFFFu, 0x100000000u},
+                {0x100000000u, 0x100000000u},
+                {0x100000001u, 0x100000001u},
+                {max, max},
+                {max, 2},
+                {0xFFFFFFFF00000000u, 0x100000001u},
+                {0x100000001u, 0xFFFFFFFF00000000u},
+                {max, 1},
+                {2, max},
+            }
+        };
+
+        for (const auto& test : edge_cases)
+        {
+            check_product(test.first, test.second);
+        }
+
         // whichever implementation the compiler gets (with or without a
-        // 128-bit integer type or a builtin)
+        // 128-bit integer type or a builtin / intrinsic)
         std::uint64_t state = 42;
         for (int i = 0; i < 10000; ++i)
         {
@@ -901,8 +933,7 @@ TEST_CASE("Eisel-Lemire float conversion")
             state ^= state << 17u;
             const std::uint64_t a = state;
             const std::uint64_t b = (state * 0x9E3779B97F4A7C15u) >> (i % 64);
-            const auto product = nlohmann::detail::full_multiplication(a, b);
-            CHECK(big_from(product.high, product.low) == big_mul(big_from(0, a), big_from(0, b)));
+            check_product(a, b);
 
             const int k = i % 64;
             const std::uint64_t x = (std::uint64_t{1} << k) | (a & ((std::uint64_t{1} << k) - 1));

tools/check_build_options/README.md

@@ -0,0 +1,21 @@
+# check_build_options
+
+Checks that the Meson build and the pkg-config files offer the same options as the CMake target, so that a new CMake
+option is not forgotten in one of them.
+
+The compile definitions of the CMake target (`target_compile_definitions` in [`CMakeLists.txt`](../../CMakeLists.txt))
+are the reference. When you add an option there, also add it to
+
+- the pkg-config block in `CMakeLists.txt` (`NLOHMANN_JSON_PKGCONFIG_CFLAGS`),
+- [`meson_options.txt`](../../meson_options.txt), named without the `JSON_` prefix and with the same default,
+- [`meson.build`](../../meson.build) (`json_defines`), and
+- the list of Meson options in
+  [`docs/mkdocs/docs/integration/package_managers.md`](../../docs/mkdocs/docs/integration/package_managers.md).
+
+Run the check with
+
+```shell
+make check_build_options
+```
+
+It needs only Python 3 and runs in the `ci_meson_install` CI job.

tools/check_build_options/check_build_options.py

@@ -0,0 +1,144 @@
+#!/usr/bin/env python3
+"""Check that the Meson build and the pkg-config files offer the CMake options.
+
+The compile definitions of the CMake target (target_compile_definitions in
+CMakeLists.txt) are the reference. For every option used there, the script
+checks that
+
+- the CMake pkg-config file adds the same definition under the same condition,
+- meson_options.txt has a boolean option of the same name without the "JSON_"
+  prefix and with the same default,
+- meson.build adds the same definition under the same condition, and
+- the Meson section of the package manager documentation lists the option.
+
+Meson's MultipleHeaders option selects the include directory and adds no
+definition; it is the only Meson option without a definition.
+"""
+
+import argparse
+import os
+import re
+import sys
+
+REPO_ROOT = os.path.normpath(os.path.join(sys.path[0], '..', '..'))
+DOCS = os.path.join('docs', 'mkdocs', 'docs', 'integration', 'package_managers.md')
+
+# Meson options that add no compile definition, with their default
+MESON_ONLY = {'MultipleHeaders': 'false'}
+
+
+def read(root, path):
+    with open(os.path.join(root, path), encoding='utf-8') as f:
+        return f.read()
+
+
+def cmake_target_definitions(cmake):
+    """Return {option: (definition, add_if_on)} from target_compile_definitions."""
+    block = re.search(r'target_compile_definitions\(\s*\$\{NLOHMANN_JSON_TARGET_NAME\}\s*INTERFACE(.*?)\n\)', cmake, re.S)
+    if not block:
+        sys.exit('CMakeLists.txt: target_compile_definitions of the target not found')
+    result = {}
+    for line in block.group(1).split('\n'):
+        line = line.strip()
+        if not line:
+            continue
+        m = re.fullmatch(r'\$<\$<NOT:\$<BOOL:\$\{JSON_(\w+)\}>>:(\w+=\w+)>', line)
+        if m:
+            result[m.group(1)] = (m.group(2), False)
+            continue
+        m = re.fullmatch(r'\$<\$<BOOL:\$\{JSON_(\w+)\}>:(\w+=\w+)>', line)
+        if m:
+            result[m.group(1)] = (m.group(2), True)
+            continue
+        sys.exit(f'CMakeLists.txt: unexpected line in target_compile_definitions: {line}')
+    return result
+
+
+def cmake_defaults(cmake):
+    """Return {option: 'true'/'false'} for the option() calls of the form JSON_<name>."""
+    return {m.group(1): 'true' if m.group(2) == 'ON' else 'false'
+            for m in re.finditer(r'^option\(JSON_(\w+)\s+"[^"]*"\s+(ON|OFF)\)', cmake, re.M)}
+
+
+def cmake_pkgconfig_definitions(cmake):
+    """Return {option: (definition, add_if_on)} from the pkg-config block."""
+    return {m.group(2): (m.group(3), m.group(1) is None)
+            for m in re.finditer(r'if \((NOT )?JSON_(\w+)\)\s*\n\s*string\(APPEND NLOHMANN_JSON_PKGCONFIG_CFLAGS " -D(\w+=\w+)"\)', cmake)}
+
+
+def meson_options(options):
+    """Return {option: default} for the boolean options in meson_options.txt."""
+    result = {}
+    for block in re.findall(r'option\((.*?)\)', options, re.S):
+        name = re.search(r"'(\w+)'", block).group(1)
+        kind = re.search(r"type\s*:\s*'(\w+)'", block)
+        value = re.search(r'value\s*:\s*(\w+)', block)
+        result[name] = value.group(1) if kind and kind.group(1) == 'boolean' and value else None
+    return result
+
+
+def meson_definitions(meson):
+    """Return {option: (definition, add_if_on)} from meson.build."""
+    return {m.group(2): (m.group(3), m.group(1) is None)
+            for m in re.finditer(r"if (not )?get_option\('(\w+)'\)\s*\n\s*json_defines \+= '(\w+=\w+)'", meson)}
+
+
+def describe(definition):
+    name, add_if_on = definition
+    return f'{name} if {"enabled" if add_if_on else "disabled"}'
+
+
+def compare(errors, where, expected, actual):
+    for option, definition in expected.items():
+        if option not in actual:
+            errors.append(f'{where}: no definition for option {option} (expected {describe(definition)})')
+        elif actual[option] != definition:
+            errors.append(f'{where}: option {option} adds {describe(actual[option])}, expected {describe(definition)}')
+    for option in actual.keys() - expected.keys():
+        errors.append(f'{where}: definition for option {option}, which the CMake target does not have')
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__.split('\n')[0])
+    parser.add_argument('root', nargs='?', default=REPO_ROOT, help='repository root (default: %(default)s)')
+    root = parser.parse_args().root
+
+    cmake = read(root, 'CMakeLists.txt')
+    reference = cmake_target_definitions(cmake)
+    defaults = cmake_defaults(cmake)
+    errors = []
+
+    compare(errors, 'CMakeLists.txt (pkg-config)', reference, cmake_pkgconfig_definitions(cmake))
+    compare(errors, 'meson.build', reference, meson_definitions(read(root, 'meson.build')))
+
+    options = meson_options(read(root, 'meson_options.txt'))
+    for option in reference:
+        if option not in defaults:
+            errors.append(f'CMakeLists.txt: no option(JSON_{option} ... ON|OFF)')
+        elif option not in options:
+            errors.append(f'meson_options.txt: option {option} missing')
+        elif options[option] != defaults[option]:
+            errors.append(f'meson_options.txt: option {option} must be boolean with value {defaults[option]} as in CMake')
+    for option, default in MESON_ONLY.items():
+        if options.get(option) != default:
+            errors.append(f'meson_options.txt: option {option} must be boolean with value {default}')
+    for option in options.keys() - reference.keys() - MESON_ONLY.keys():
+        errors.append(f'meson_options.txt: option {option} has no counterpart in the CMake target')
+
+    docs = read(root, DOCS)
+    for option in sorted(set(options) & (reference.keys() | MESON_ONLY.keys())):
+        if f'`{option}`' not in docs:
+            errors.append(f'{DOCS}: Meson option {option} not listed')
+
+    for error in errors:
+        print(error, file=sys.stderr)
+    if errors:
+        print('The Meson build and the pkg-config files must offer the options of the CMake target; see '
+              'tools/check_build_options/README.md.', file=sys.stderr)
+        return 1
+    print(f'OK: {len(reference)} options with compile definitions agree between CMake, pkg-config, and Meson.')
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())