Update copyright years

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/dependabot.yml

@@ -0,0 +1,11 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+        interval: "weekly"

.github/workflows/ci.yml

@@ -17,35 +17,42 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - toolset: gcc-7
-            cxxstd: "03,11,14,17"
-            os: ubuntu-18.04
-          - toolset: gcc-9  # Do not remove! It is the only toolset that tests misc/strip_boost_namespace.sh
+          - toolset: gcc-14  # Do not remove! It is the only toolset that tests CMake tests down below
+            cxxstd: "03,11,14,17,20"
+            os: ubuntu-24.04
+          - toolset: gcc-12
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-18.04
+            os: ubuntu-22.04
+            cxxflags: "cxxflags=--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined"
+            linkflags: "linkflags=--coverage -lasan -lubsan"
+            gcov_tool: "gcov-12"
+          - toolset: gcc-11
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-22.04
+            cxxflags: "cxxflags=--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined"
+            linkflags: "linkflags=--coverage -lasan -lubsan"
+            gcov_tool: "gcov-11"
           - toolset: gcc-10
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-18.04
+            os: ubuntu-22.04
             cxxflags: "cxxflags=--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined"
             linkflags: "linkflags=--coverage -lasan -lubsan"
             gcov_tool: "gcov-10"
-          - toolset: clang
-            compiler: clang++-10
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
-            cxxflags: "cxxflags=-fsanitize=address,undefined,integer -fno-sanitize-recover=undefined"
-            linkflags: "linkflags=-fsanitize=address,undefined,integer"
-          # To low quota to use
-          #- toolset: clang
-          #  cxxstd: "03,11,14,17,2a"
-          #  os: macos-10.15
-          #  cxxflags: "cxxflags=-fsanitize=address,undefined -fno-sanitize-recover=undefined"
-          #  linkflags: "linkflags=-fsanitize=address,undefined"
+          - toolset: clang-15
+            cxxstd: "03,11,14,17,20"
+            os: ubuntu-22.04
+          - toolset: clang-18
+            cxxstd: "03,11,14,17,20,23"
+            os: ubuntu-24.04
+          - toolset: clang-19   # tests misc/strip_boost_namespace.sh and modules
+            cxxstd: "20,23"
+            os: ubuntu-24.04
+            install: clang-19 llvm-19 libclang-rt-19-dev libc++-19-dev libc++abi-19-dev clang-tools-19
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
 
       - name: Install packages
         if: matrix.install
@@ -67,28 +74,60 @@ jobs:
           cd ..
           git clone -b $BOOST_BRANCH --depth 10 https://github.com/boostorg/boost.git boost-root
           cd boost-root
-          git submodule update --init --depth 10 --jobs 2 tools/boostdep tools/inspect libs/filesystem
+          git submodule update --init --depth 10 --jobs 2 tools/boostdep libs/filesystem tools/inspect
           python tools/boostdep/depinst/depinst.py --git_args "--depth 10 --jobs 3" filesystem
           rm -rf libs/$LIBRARY/*
           cp -r $GITHUB_WORKSPACE/* libs/$LIBRARY
           python tools/boostdep/depinst/depinst.py --include benchmark --include example --include examples --include tools --git_args "--depth 10 --jobs 3" $LIBRARY
           ./bootstrap.sh
-          ./b2 -d0 headers
-          ./b2 -j4 variant=debug tools/inspect/build
+          ./b2 variant=debug tools/inspect
 
-      - name: Create user-config.jam
-        if: matrix.compiler
+      - name: Run CMake tests
+        if: ${{matrix.toolset == 'gcc-14'}}
         run: |
-          echo "using ${{matrix.toolset}} : : ${{matrix.compiler}} ;" > ~/user-config.jam
+          cd ../boost-root/
+          mkdir __build
+          cd __build
+          cmake -DBUILD_TESTING=1 -DBOOST_INCLUDE_LIBRARIES=pfr -DCMAKE_CXX_COMPILER=g++-14 -DCMAKE_C_COMPILER=gcc-14 ..
+          cmake --build . --target tests
+          ctest --output-on-failure --no-tests=error
+          cd ..
+          rm -rf __build
+
+      - name: Run modules tests
+        if: false
+        # if: ${{matrix.toolset == 'clang-19'}}
+        run: |
+          cd ../boost-root/libs/pfr
+          mkdir build_module
+          cd build_module
+          cmake -DBUILD_TESTING=1 -DBOOST_USE_MODULES=1 -DCMAKE_CXX_COMPILER=clang++-19 -DCMAKE_CXX_FLAGS=-stdlib=libc++ -DCMAKE_EXE_LINKER_FLAGS=-stdlib=libc++ -DCMAKE_CXX_STANDARD=23 -DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=0e5b6991-d74f-4b3d-a41c-cf096e0b2508 -G Ninja ../test/cmake_subdir_test
+          cmake --build .
+          ctest -V
+          cd ..
+          rm -rf build_module
+
+      - name: Run modules tests wihtout 'import std;'
+        if: ${{matrix.toolset == 'clang-19'}}
+        run: |
+          cd ../boost-root/libs/pfr
+          mkdir build_module
+          cd build_module
+          cmake -DBOOST_USE_MODULES=1 -DBUILD_TESTING=1 -GNinja -DCMAKE_CXX_COMPILER=clang++-19 ../test/cmake_subdir_test
+          cmake --build .
+          ctest -V
+          cd ..
+          rm -rf build_module
 
       - name: Run tests
         run: |
           cd ../boost-root
-          ./b2 -j3 libs/$LIBRARY/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} variant=debug,release "${{matrix.cxxflags}}" "${{matrix.linkflags}}" "${{matrix.launcher}}"
+          ./b2 -d0 headers
+          ./b2 libs/$LIBRARY/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} variant=debug,release "${{matrix.cxxflags}}" "${{matrix.linkflags}}" "${{matrix.launcher}}"
           dist/bin/inspect libs/$LIBRARY
 
       - name: Test boost namespace stripping
-        if: ${{matrix.toolset == 'gcc-9'}}
+        if: ${{matrix.toolset == 'clang-19'}}
         run: ../boost-root/libs/$LIBRARY/misc/strip_boost_namespace.sh
 
       - name: Prepare coverage data
@@ -98,9 +137,9 @@ jobs:
 
           echo -e "#!/bin/bash\nexec ${{matrix.gcov_tool}} \"\$@\"" > $GITHUB_WORKSPACE/coveralls/gcov_wrapper.sh
           chmod +x $GITHUB_WORKSPACE/coveralls/gcov_wrapper.sh
-          wget https://github.com/linux-test-project/lcov/archive/v1.15.zip
-          unzip v1.15.zip
-          LCOV="`pwd`/lcov-1.15/bin/lcov --gcov-tool $GITHUB_WORKSPACE/coveralls/gcov_wrapper.sh"
+          wget https://github.com/linux-test-project/lcov/archive/v1.16.zip
+          unzip v1.16.zip
+          LCOV="`pwd`/lcov-1.16/bin/lcov --gcov-tool $GITHUB_WORKSPACE/coveralls/gcov_wrapper.sh"
 
           echo "$LCOV --directory ../boost-root/bin.v2/libs/$LIBRARY/ --base-directory `pwd`/libs/$LIBRARY/test --capture --output-file $GITHUB_WORKSPACE/coveralls/coverage.info"
           $LCOV --directory ../boost-root/bin.v2/libs/$LIBRARY/ --base-directory ../boost-root/ --capture --output-file $GITHUB_WORKSPACE/coveralls/coverage.info
@@ -124,25 +163,31 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          # TODO: fails the loophole tests
-          #- toolset: msvc
-          #  cxxstd: "14,17,latest"
-          #  addrmd: 32,64
-          #  os: windows-2022
-          # TODO: fails the loophole tests
-          #- toolset: msvc-14.2
-          #  cxxstd: "14,17,latest"
-          #  addrmd: 32,64
-          #  os: windows-2019
+          - toolset: msvc-14.3        # tests CMake tests down below, does not run b2 tests
+            cxxstd: "14,17,20,latest"
+            addrmd: 64
+            os: windows-2025
+            threads: "-j3"
           - toolset: gcc
             cxxstd: "03,11,14,17,2a"
             addrmd: 64
-            os: windows-2019
+            os: windows-2025
+            threads: "-j3"
+          - toolset: msvc-14.3  # tests CMake tests down below
+            cxxstd: "20,latest"
+            addrmd: 64
+            os: windows-2022
+            threads: "-j1"
+            # Fails with "Unexpected compiler version, expected Clang 19.0.0 or newer."
+            # - toolset: clang-win
+            #   cxxstd: "14,17,2a,latest"
+            #   addrmd: 32,64
+            #   os: windows-2022
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
 
       - name: Setup Boost
         shell: cmd
@@ -161,16 +206,62 @@ jobs:
           git clone -b %BOOST_BRANCH% --depth 10 https://github.com/boostorg/boost.git boost-root
           cd boost-root
           xcopy /s /e /q %GITHUB_WORKSPACE% libs\%LIBRARY%\
-          git submodule update --init tools/boostdep
+          git submodule update --init --depth 10 --jobs 2 tools/boostdep
           python tools/boostdep/depinst/depinst.py --include benchmark --include example --include examples --include tools --git_args "--jobs 3" %LIBRARY%
           cmd /c bootstrap
-          b2 -d0 headers
+
+      - name: Run CMake tests
+        if: ${{matrix.toolset == 'msvc-14.3'}}
+        shell: cmd
+        run: |
+          choco install --no-progress ninja
+          call "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvarsall.bat" x64
+          cd ../boost-root/
+          mkdir __build
+          cd __build
+          cmake -DBUILD_TESTING=1 -DBOOST_INCLUDE_LIBRARIES=pfr ..
+          cmake --build . --target tests --config Debug
+          ctest --output-on-failure --no-tests=error -C Debug
+          cd ..
+          rm -rf __build
+
+      - name: Run modules tests
+        if: false
+        # if: ${{matrix.toolset == 'msvc-14.3'}}
+        shell: cmd
+        run: |
+          choco install --no-progress ninja
+          call "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvarsall.bat" x64
+          cd ../boost-root/libs/pfr
+          mkdir build_module
+          cd build_module
+          cmake -DBOOST_USE_MODULES=1 -DBUILD_TESTING=1 -DCMAKE_CXX_STANDARD=23 -DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=0e5b6991-d74f-4b3d-a41c-cf096e0b2508 -G Ninja ../test/cmake_subdir_test
+          cmake --build .
+          ctest --no-tests=error -V
+          cd ..
+          rm -rf build_module
+
+      - name: Run modules tests wihtout 'import std;'
+        if: ${{matrix.toolset == 'msvc-14.3'}}
+        shell: cmd
+        run: |
+          choco install --no-progress ninja
+          call "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvarsall.bat" x64
+          cd ../boost-root/libs/pfr
+          mkdir build_module
+          cd build_module
+          cmake -DBOOST_USE_MODULES=1 -DBUILD_TESTING=1 -DCMAKE_CXX_STANDARD=20 -G Ninja ../test/cmake_subdir_test
+          cmake --build .
+          ctest --no-tests=error -V
+          cd ..
+          rm -rf build_module
 
       - name: Run tests
         shell: cmd
         run: |
           cd ../boost-root
-          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release
+          b2 -d0 headers
+          b2 ${{matrix.threads}} libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release
 
   finish:
     needs: posix

CMakeLists.txt

@@ -1,20 +1,48 @@
-# Generated by `boostdep --cmake pfr`
 # Copyright 2020 Peter Dimov
+# Copyright (c) 2016-2026 Antony Polukhin
+#
 # Distributed under the Boost Software License, Version 1.0.
 # https://www.boost.org/LICENSE_1_0.txt
 
-cmake_minimum_required(VERSION 3.5...3.16)
+cmake_minimum_required(VERSION 3.5...3.31)
 
 project(boost_pfr VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
-add_library(boost_pfr INTERFACE)
-add_library(Boost::pfr ALIAS boost_pfr)
-
-target_include_directories(boost_pfr INTERFACE include)
-
-if(BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")
-
-  add_subdirectory(test)
+if (BOOST_USE_MODULES)
+    add_library(boost_pfr)
+    target_sources(boost_pfr PUBLIC
+        FILE_SET modules_public TYPE CXX_MODULES FILES modules/boost_pfr.cppm
+    )
 
+    target_compile_features(boost_pfr PUBLIC cxx_std_20)
+    target_compile_definitions(boost_pfr PUBLIC BOOST_USE_MODULES)
+    if (CMAKE_CXX_COMPILER_IMPORT_STD)
+        target_compile_definitions(boost_pfr PRIVATE BOOST_PFR_USE_STD_MODULE)
+        message(STATUS "Using `import std;`")
+    else()
+        message(STATUS "`import std;` is not available")
+    endif()
+    target_include_directories(boost_pfr PUBLIC include)
+else()
+    add_library(boost_pfr INTERFACE)
+    target_include_directories(boost_pfr INTERFACE include)
+endif()
+
+add_library(Boost::pfr ALIAS boost_pfr)
+
+enable_testing()
+if (BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")
+    add_subdirectory(test)
+endif()
+
+if (BOOST_USE_MODULES AND BUILD_TESTING)
+    add_executable(boost_pfr_module_usage modules/usage_sample.cpp)
+    target_link_libraries(boost_pfr_module_usage PRIVATE Boost::pfr)
+    add_test(NAME boost_pfr_module_usage COMMAND boost_pfr_module_usage)
+
+    # Make sure that mixing includes and imports is fine for different TU
+    add_executable(boost_pfr_module_usage_mu modules/usage_test_mu1.cpp modules/usage_test_mu2.cpp)
+    target_link_libraries(boost_pfr_module_usage_mu PRIVATE Boost::pfr)
+    add_test(NAME boost_pfr_module_usage_mu COMMAND boost_pfr_module_usage_mu)
 endif()
 

README.md

@@ -10,8 +10,8 @@ For a version of the library without `boost::` namespace see [PFR](https://githu
 
 Branches        | Build         | Tests coverage | More info
 ----------------|-------------- | -------------- |-----------
-Develop:        | [![CI](https://github.com/boostorg/pfr/actions/workflows/ci.yml/badge.svg?branch=develop)](https://github.com/boostorg/pfr/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/0mavmnkdmltcdmqa/branch/develop?svg=true)](https://ci.appveyor.com/project/apolukhin/pfr/branch/develop) | [![Coverage Status](https://coveralls.io/repos/github/apolukhin/magic_get/badge.png?branch=develop)](https://coveralls.io/github/apolukhin/magic_get?branch=develop) | [details...](https://www.boost.org/development/tests/develop/developer/pfr.html)
-Master:         | [![CI](https://github.com/boostorg/pfr/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/boostorg/pfr/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/0mavmnkdmltcdmqa/branch/master?svg=true)](https://ci.appveyor.com/project/apolukhin/pfr/branch/master) | [![Coverage Status](https://coveralls.io/repos/github/apolukhin/magic_get/badge.png?branch=master)](https://coveralls.io/github/apolukhin/magic_get?branch=master) | [details...](https://www.boost.org/development/tests/master/developer/pfr.html)
+Develop:        | [![CI](https://github.com/boostorg/pfr/actions/workflows/ci.yml/badge.svg?branch=develop)](https://github.com/boostorg/pfr/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/0mavmnkdmltcdmqa/branch/develop?svg=true)](https://ci.appveyor.com/project/apolukhin/pfr/branch/develop) | [![Coverage Status](https://coveralls.io/repos/github/apolukhin/magic_get/badge.png?branch=develop)](https://coveralls.io/github/apolukhin/magic_get?branch=develop) | [details...](https://regression.boost.io/develop/developer/pfr.html)
+Master:         | [![CI](https://github.com/boostorg/pfr/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/boostorg/pfr/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/0mavmnkdmltcdmqa/branch/master?svg=true)](https://ci.appveyor.com/project/apolukhin/pfr/branch/master) | [![Coverage Status](https://coveralls.io/repos/github/apolukhin/magic_get/badge.png?branch=master)](https://coveralls.io/github/apolukhin/magic_get?branch=master) | [details...](https://regression.boost.io/master/developer/pfr.html)
 
 [Latest developer documentation](https://www.boost.org/doc/libs/develop/doc/html/boost_pfr.html)
 
@@ -45,6 +45,8 @@ Outputs:
 Edgar Allan Poe was born in 1809
 ```
 
+[Run the above sample](https://godbolt.org/z/PfYsWKb7v)
+
 
 ### Motivating Example #1
 ```c++
@@ -94,6 +96,58 @@ Outputs:
 my_struct has 2 fields: {"Das ist fantastisch!", 100}
 ```
 
+### Motivating Example #3
+
+```c++
+#include <iostream>
+#include <string>
+
+#include <boost/config/warning_disable.hpp>
+#include <boost/spirit/home/x3.hpp>
+#include <boost/fusion/include/adapt_boost_pfr.hpp>
+
+#include "boost/pfr/io.hpp"
+
+namespace x3 = boost::spirit::x3;
+
+struct ast_employee { // No BOOST_FUSION_ADAPT_STRUCT defined
+    int age;
+    std::string forename;
+    std::string surname;
+    double salary;
+};
+
+auto const quoted_string = x3::lexeme['"' >> +(x3::ascii::char_ - '"') >> '"'];
+
+x3::rule<class employee, ast_employee> const employee = "employee";
+auto const employee_def =
+    x3::lit("employee")
+    >> '{'
+    >>  x3::int_ >> ','
+    >>  quoted_string >> ','
+    >>  quoted_string >> ','
+    >>  x3::double_
+    >>  '}'
+    ;
+BOOST_SPIRIT_DEFINE(employee);
+
+int main() {
+    std::string str = R"(employee{34, "Chip", "Douglas", 2500.00})";
+    ast_employee emp;
+    x3::phrase_parse(str.begin(),
+                     str.end(),
+                     employee,
+                     x3::ascii::space,
+                     emp);
+    std::cout << boost::pfr::io(emp) << std::endl;
+}
+
+```
+Outputs:
+```
+(34 Chip Douglas 2500)
+```
+
 
 ### Requirements and Limitations
 

build.jam

@@ -0,0 +1,20 @@
+# Copyright René Ferdinand Rivera Morell 2023-2024
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+
+require-b2 5.2 ;
+
+project /boost/pfr
+    : common-requirements
+        <include>include
+    ;
+
+explicit
+    [ alias boost_pfr : : : : <library>$(boost_dependencies) ]
+    [ alias all : boost_pfr test ]
+    ;
+
+call-if : boost-library pfr
+    ;
+

doc/Jamfile.v2

@@ -18,7 +18,7 @@ project pfr/doc ;
 
 #
 # Common params for doxygen
-# 
+#
 
 local doxygen_params =
         <doxygen:param>EXTRACT_ALL=NO
@@ -32,19 +32,22 @@ local doxygen_params =
         <doxygen:param>"ALIASES= \\
             \"forcedlink{1}=\\xmlonly<link linkend='boost.pfr.\\1'>\\endxmlonly boost::pfr::\\1\\xmlonly</link>\\endxmlonly\" \\
             \"podops=\\b See \\b Also : \\xmlonly<link linkend='boost_pfr.tutorial.three_ways_of_getting_operators'>\\endxmlonly 'Three ways of getting operators' \\xmlonly</link>\\endxmlonly\" \\
+            \"fnrefl=\\b See \\b Also : \\xmlonly<link linkend='boost_pfr.tutorial.reflection_of_field_name'>\\endxmlonly 'Reflection of field names' \\xmlonly</link>\\endxmlonly\" \\
             \"customio=\\b See \\b Also : \\xmlonly<link linkend='boost_pfr.tutorial.custom_printing_of_aggregates'>\\endxmlonly 'Custom printing of aggregates' \\xmlonly</link>\\endxmlonly for info on how to implement your own manipulator with custom format.\" \\
             \"aggregate=\\xmlonly<link linkend='boost_pfr.limitations_and_configuration'>\\endxmlonly simple aggregate \\xmlonly</link>\\endxmlonly\" \\
-            \"BOOST_PFR_DOXYGEN_INVOKED\" \\
+        "
+        <doxygen:param>"PREDEFINED= \\
+            \"BOOST_PFR_DOXYGEN_INVOKED=1\" \\
         "
     ;
 
 doxygen autodoc_pfr
     :
-        [ glob ../../../boost/pfr.hpp ]
-        [ glob ../../../boost/pfr/*.hpp ]
+        [ glob ../include/boost/pfr.hpp ]
+        [ glob ../include/boost/pfr/*.hpp ]
     :
         $(doxygen_params)
-        <xsl:param>"boost.doxygen.reftitle=Reference Section"
+        <xsl:param>"boost.doxygen.reftitle=Reference Section of PFR"
     ;
 
 boostbook pfr-doc
@@ -52,9 +55,8 @@ boostbook pfr-doc
         pfr.qbk
     :
         <dependency>autodoc_pfr
-        <xsl:param>boost.root=https://www.boost.org/doc/libs/1_72_0
-        #<xsl:param>boost.root=../../../.
-        <xml:param>html.stylesheet=../../../../doc/src/boostbook.css
+        #<xsl:param>boost.root=https://www.boost.org/doc/libs/1_88_0
+        <xsl:param>boost.root=../../../..
     ;
 
 ###############################################################################

doc/pfr.qbk

@@ -1,7 +1,7 @@
 [library Boost.PFR
     [quickbook 1.6]
-    [version 2.0]
-    [copyright 2016-2022 Antony Polukhin]
+    [version 2.3]
+    [copyright 2016-2026 Antony Polukhin]
     [category Language Features Emulation]
     [license
         Distributed under the Boost Software License, Version 1.0.
@@ -17,6 +17,7 @@ Boost.PFR is a C++14 library for a very basic reflection. It gives you access to
 [import ../example/motivating_example0.cpp]
 [pfr_motivating_example]
 
+Experiment with the sample [@https://godbolt.org/z/PfYsWKb7v online].
 See [link boost_pfr.limitations_and_configuration [*limitations]].
 
 
@@ -42,20 +43,20 @@ user_info retrieve_friend(std::string_view name) {
         name
     );
 
-    ////////////////////////////////////////////////////////////////////////////////
+    /////////////////////////////////////////////////////////////////////////////
     user_info info {
         std::move(std::get<0>(info_tuple)),
         std::move(std::get<1>(info_tuple)),
         std::move(std::get<2>(info_tuple)),
         std::move(std::get<3>(info_tuple)),
     }
-    ////////////////////////////////////////////////////////////////////////////////
+    /////////////////////////////////////////////////////////////////////////////
 
     auto friend_info = ask_user_for_friend(std::move(info));
 
     db::insert(
         "INSERT INTO user_infos(id, name, email, login) VALUES ($0, $1, $2, $3)",
-        friend_info.id,    /////////////////////////////////////////////////////////
+        friend_info.id,    //////////////////////////////////////////////////////
         friend_info.name,  // Users are forced to enumerate fields because your
         friend_info.email, // library can not iterate over the fields of a user
         friend_info.login  // provided structure
@@ -80,20 +81,20 @@ user_info retrieve_friend(std::string_view name) {
         name
     );
 
-    ////////////////// No boilerplate code to move data around /////////////////////
+    ////////////////// No boilerplate code to move data around //////////////////
 
 
 
 
 
 
-    ////////////////////////////////////////////////////////////////////////////////
+    /////////////////////////////////////////////////////////////////////////////
 
     auto friend_info = ask_user_for_friend(std::move(info));
 
     db::insert(
         "INSERT INTO user_infos(id, name, email, login) VALUES ($0, $1, $2, $3)",
-        friend_info     ////////////////////////////////////////////////////////////
+        friend_info     /////////////////////////////////////////////////////////
                         // Boost.PFR allows you to iterate over all the fields
                         // of a user provided structure
                         //
@@ -119,7 +120,7 @@ struct user_info {
     std::string name, email, login;
 };
 
-/// Customizations via hand-written code or macro like BOOST_FUSION_ADAPT_STRUCT ///
+/// Customizations via hand-written code ////////////////////////////////////////
 auto db_api_tie(user_info& ui) noexcept {
     return std::tie(ui.id, ui.name, ui.email, ui.login);
 }
@@ -127,7 +128,7 @@ auto db_api_tie(user_info& ui) noexcept {
 auto db_api_tie(const user_info& ui) noexcept {
     return std::tie(ui.id, ui.name, ui.email, ui.login);
 }
-////////////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////////////////
 ```
 ][
 ```
@@ -138,7 +139,7 @@ struct user_info {
     std::string name, email, login;
 };
 
-//////// With Boost.PFR there's no need in hand written customizations /////////////
+//////// With Boost.PFR there's no need in hand written customizations //////////
 
 
 
@@ -146,14 +147,29 @@ struct user_info {
 
 
 
-////////////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////////////////
 ```
 ]]
 ]
 
 
+Imagine that you are writing a serialization library. Serialization of user
+provided structures (and nested structures) with Boost.PFR it is just as simple as:
+
+```
+void Write(Writer& writer, int value);
+void Write(Writer& writer, std::string_view value);
+
+template <typename T>
+std::enable_if_t<boost::pfr::is_implicitly_reflectable_v<T>> Write(Writer& writer, const T& value) {
+  boost::pfr::for_each_field(
+      value, [&writer](const auto& field) { Write(writer, field); });
+}
+```
+
 With Boost.PFR the code is shorter, more readable and more pleasant to write.
 
+[note All the above examples were inspired by the Boost.PFR usage in [@https://github.com/userver-framework/userver 🐙 userver framework].]
 
 
 [h2 Out of the box functionality ]
@@ -164,14 +180,17 @@ Boost.PFR adds the following out-of-the-box functionality for aggregate initiali
 * heterogeneous comparators
 * hash
 * IO streaming
-* access to members by index
+* access to members by index or type
+* access to member's names by index
 * member type retrieval
-* methods for cooperation with `std::tuple`
+* methods for cooperation with `std::tuple` for members
+* methods for cooperation with `std::array` for member's names
 * methods to visit each field of the structure
+* trait to detect potential ability to reflect type, and ability to override trait's decision in user-side code
 
 Boost.PFR is a header only library that does not depend on Boost. You can just copy the content of the "include" folder [@https://github.com/boostorg/pfr from the Boost.PFR github] into your project, and the library will work fine. For a version of the library without `boost::` namespace see [@https://github.com/apolukhin/pfr_non_boost PFR].
 
-[caution Recommended C++ Standards are C++17 and above. Library requires at least C++14! Pre C++14 compilers (C++11, C++03...) are not supported]
+[caution Recommended C++ Standards are C++20 and above. C++17 completely enough for a user who doesn't want accessing name of structure member. Library requires at least C++14! Pre C++14 compilers (C++11, C++03...) are not supported]
 
 [endsect]
 
@@ -186,6 +205,9 @@ Boost.PFR is a header only library that does not depend on Boost. You can just c
 [
     [ [pfr_quick_examples_get] ]
     [ [funcref boost::pfr::get] ]
+][
+    [ [pfr_quick_examples_get_name] ]
+    [ [funcref boost::pfr::get_name] ]
 ][
     [ [pfr_quick_examples_ops] ]
     [
@@ -208,6 +230,9 @@ Boost.PFR is a header only library that does not depend on Boost. You can just c
 
         [funcref boost::pfr::io]
     ]
+][
+    [ [pfr_quick_examples_for_each_with_name] ]
+    [ [funcref boost::pfr::for_each_field_with_name] ]
 ][
     [ [pfr_quick_examples_functions_for] ]
     [ [macroref BOOST_PFR_FUNCTIONS_FOR] ]
@@ -252,6 +277,7 @@ Boost.PFR is a header only library that does not depend on Boost. You can just c
 
 [import ../example/sample_printing.cpp]
 [import ../example/get.cpp]
+[import ../example/get_name.cpp]
 
 
 [section Why tuples are bad and aggregates are more preferable?]
@@ -431,12 +457,21 @@ error: static_assert failed "====================> Boost.PFR: For safety reasons
 
 [endsect]
 
+
+[section Reflection of field name ]
+
+[pfr_example_get_name]
+
+See [link boost_pfr.limitations_and_configuration [*Limitations and Configuration]].
+
+[endsect]
+
 [endsect]
 
 
 [section Limitations and Configuration]
 
-[caution Recommended C++ Standards are C++17 and above. Library requires at least C++14! Pre C++14 compilers (C++11, C++03...) are not supported. ]
+[caution Recommended C++ Standards are C++20 and above. C++17 completely enough for a user who doesn't want accessing name of structure member. Library requires at least C++14! Pre C++14 compilers (C++11, C++03...) are not supported. ]
 
 Boost.PFR library works with types that satisfy the requirements of `SimpleAggregate`: aggregate types without base classes, `const` fields, references, or C arrays:
 
@@ -458,15 +493,24 @@ struct aggregate : empty { // not a SimpleAggregate
 ```
 The library may work with aggregates that don't satisfy the requirements of `SimpleAggregate`, but the behavior tends to be non-portable.
 
+Boost.PFRs extraction of field name works with only `SimpleAggregate` types.
+
+
 [h2 Configuration Macro]
 
 By default Boost.PFR [*auto-detects your compiler abilities] and automatically defines the configuration macro into appropriate values. If you wish to override that behavior, just define:
 [table:linkmacro Macros
     [[Macro name] [Effect]]
+    [[*BOOST_PFR_USE_CPP26*] [Define to `1` if you wish to override Boost.PFR choice and use C++26 variadic structured bindings for reflection. Define to `0` to override Boost.PFR choice and disable C++26 variadic structured bindings usage.]]
     [[*BOOST_PFR_USE_CPP17*] [Define to `1` if you wish to override Boost.PFR choice and use C++17 structured bindings for reflection. Define to `0` to override Boost.PFR choice and disable C++17 structured bindings usage.]]
     [[*BOOST_PFR_USE_LOOPHOLE*] [Define to `1` if you wish to override Boost.PFR choice and exploit [@http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#2118 CWG 2118] for reflection. Define to `0` to override Boost.PFR choice and disable CWG 2118 usage.]]
     [[*BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE*] [Define to `0` if you are hit by the template instantiation depth issues with `std::make_integer_sequence` and wish to use Boost.PFR version of that metafunction. Define to `1` to override Boost.PFR detection logic. ]]
     [[*BOOST_PFR_HAS_GUARANTEED_COPY_ELISION*] [Define to `0` if your compiler does not implement C++17 guaranteed copy elision properly and fails to reflect aggregates with non-movable fields. Define to `1` to override Boost.PFR detection logic. ]]
+    [[*BOOST_PFR_ENABLE_IMPLICIT_REFLECTION*] [Define to `0` if you are hit by lots of non-effective choices made by implicitly reflection. Define to `1` to override Boost.PFR detection logic. ]]
+    [[*BOOST_PFR_CORE_NAME_ENABLED*] [On platforms where field name extraction is not supported, the 'boost/pfr/config.hpp' header defines the BOOST_PFR_CORE_NAME_ENABLED macro equal to 0. Defining this macro as 0 before including the header disables the ability to get a field name. ]]
+    [[*BOOST_PFR_FUNCTION_SIGNATURE*] [For known compilers defined to a compiler specific macro, that outputs the whole function signature including non-type template parameters. ]]
+    [[*BOOST_PFR_CORE_NAME_PARSING*] [Describes extraction of field name from BOOST_PFR_FUNCTION_SIGNATURE macro. See details below. ]]
+    [[*BOOST_PFR_ENABLED*] [On platforms where Boost.PFR is not supported, the `boost/pfr/config.hpp` header defines the BOOST_PFR_ENABLED macro equal to 0. Defining this macro as 0 before including the header disables the Boost.PFR library. ]]
 ]
 
 
@@ -475,32 +519,93 @@ By default Boost.PFR [*auto-detects your compiler abilities] and automatically d
 The Boost.PFRs reflection has some limitations that depend on a C++ Standard and compiler capabilities:
 
 * Static variables are ignored
-* T must be aggregate initializable without empty base classes
-* if T contains C arrays or it is inherited from non-empty type then the result of reflection may differ depending on the C++ version and library configuration
+* T must be aggregate initializable without base classes
+* if T contains C arrays then the result of reflection may differ depending on the C++ version and library configuration
 * Additional limitations if [*BOOST_PFR_USE_CPP17 == 0]:
     * Non of the member fields should have a template constructor from one parameter.
     * Additional limitations if [*BOOST_PFR_USE_LOOPHOLE == 0]:
         * T must be constexpr aggregate initializable and all its fields must be constexpr default constructible
         * [funcref boost::pfr::get], [funcref boost::pfr::structure_to_tuple], [funcref boost::pfr::structure_tie], [headerref boost/pfr/core.hpp boost::pfr::tuple_element] require T to be a POD type with built-in types only.
 
+The Boost.PFRs extraction of field name has some limitations that depend on a C++ Standard and compiler capabilities:
+
+* T should be usable like `extern T t;`, i.e. has a non-internal linkage.
+
+[h2 Adjusting BOOST_PFR_CORE_NAME_PARSING]
+
+`BOOST_PFR_CORE_NAME_PARSING` is already set up for most of the popular compilers. You need to adjust it only
+if some static_assert in the library complained on `BOOST_PFR_CORE_NAME_PARSING`.
+
+To do that:
+
+# Build `test/core_name/print_name.cpp` with your compiler and run it
+# Define BOOST_PFR_CORE_NAME_PARSING to `(skip_at_begin, skip_at_end, "")`, where
+    * `skip_at_begin` is equal to characters count before the first occurrence of `user_defined_field` in output
+    * `skip_at_end` is equal to characters count after last occurrence of `user_defined_field` in output
+# Check that `test/core_name/print_name.cpp` returns "user_defined_field"
+# If it does not return `user_defined_field`, then define BOOST_PFR_CORE_NAME_PARSING to `(skip_at_begin, skip_at_end, "T = ")`, where
+    * `skip_at_begin` is equal to `skip_at_begin` at step 2
+    * `skip_at_end` is equal to `skip_at_end` at step 2
+    * `"T = "` is equal to characters that are right before the `user_defined_field` in output, use `backward("T = ")` to search for the occurange in the string from the right
+# (optional, but highly recommended) [@https://github.com/boostorg/pfr/issues create ticket] with
+feature request to add your compiler to supported compilers list. Include
+parameters provided to `BOOST_PFR_CORE_NAME_PARSING` macro [*and] the initial output of `test/core_name/print_name.cpp`.
+
+[endsect]
+
+[section PFR as a C++20 module]
+
+[caution C++20 PFR module support is on early stage, targets, flags and behavior may change in the future]
+
+If using modern CMake define CMake option `-DBOOST_USE_MODULES=1` to build a C++20 module and
+make the `Boost::pfr` CMake target provide it. After that an explicit usage of C++20 module `boost.pfr` is allowed:
+
+[import ../modules/usage_sample.cpp]
+[pfr_module_example]
+
+The `Boost::pfr` CMake target gives an ability to mix includes and imports of the PFR library in different translation units. Moreover,
+if `BOOST_USE_MODULES` macro is defined then all the `boost/pfr/...` includes implicitly do `import boost.pfr;` to give all the
+benifits of modules without changing the existing code.
+
+[note For better compile times make sure that `import std;` is available when building the `boost.pfr` module (in CMake logs there should be
+      a 'Using `import std;`' message). ]
+
+If not using CMake, then the module could be build manually from the `modules/boost_pfr.cppm` file.
+
+For manual module build the following commands can be used for clang compiler:
+
+```
+cd pfr/module
+clang++ -I ../include -std=c++20 --precompile -x c++-module boost_pfr.cppm
+```
+
+After that, the module could be used in the following way:
+
+```
+clang++ -std=c++20 -fmodule-file=boost_pfr.pcm boost_pfr.pcm usage_sample.cpp
+```
 
 [endsect]
 
 [section How it works]
 
+[h2 Fields count detection and getting references to members]
+
 Short description:
 
 # at compile-time: use aggregate initialization to detect fields count in user-provided structure
-    * [*BOOST_PFR_USE_CPP17 == 1]:
+    * [*BOOST_PFR_USE_CPP26 == 1]:
+        # at compile-time: structured bindings are used to decompose a type `T` to known variadic amount of fields
+    * [*BOOST_PFR_USE_CPP26 == 0 && BOOST_PFR_USE_CPP17 == 1]:
         # at compile-time: structured bindings are used to decompose a type `T` to known amount of fields
-    * [*BOOST_PFR_USE_CPP17 == 0 && BOOST_PFR_USE_LOOPHOLE == 1]:
+    * [*BOOST_PFR_USE_CPP26 == 0 && BOOST_PFR_USE_CPP17 == 0 && BOOST_PFR_USE_LOOPHOLE == 1]:
         # at compile-time: use aggregate initialization to detect fields count in user-provided structure
         # at compile-time: make a structure that is convertible to anything and remember types it has been converted to during aggregate initialization of user-provided structure
         # at compile-time: using knowledge from previous steps create a tuple with exactly the same layout as in user-provided structure
         # at compile-time: find offsets for each field in user-provided structure using the tuple from previous step
         # at run-time: get pointer to each field, knowing the structure address and each field offset
         # at run-time: a tuple of references to fields is returned => all the tuple methods are available for the structure
-    * [*BOOST_PFR_USE_CPP17 == 0 && BOOST_PFR_USE_LOOPHOLE == 0]:
+    * [*BOOST_PFR_USE_CPP26 == 0 && BOOST_PFR_USE_CPP17 == 0 && BOOST_PFR_USE_LOOPHOLE == 0]:
         # at compile-time: let `I` be is an index of current field, it equals 0
         # at run-time: `T` is constructed and field `I` is aggregate initialized using a separate instance of structure that is convertible to anything [note Additional care is taken to make sure that all the information about `T` is available to the compiler and that operations on `T` have no side effects, so the compiler can optimize away the unnecessary temporary objects.]
         # at compile-time: `I += 1`
@@ -514,11 +619,22 @@ Long description of some basics: [@https://youtu.be/UlNUNxLtBI0 Antony Polukhin:
 Long description of some basics of C++14 with [link boost_pfr.limitations_and_configuration [*BOOST_PFR_USE_LOOPHOLE == 0]]: [@https://youtu.be/abdeAew3gmQ Antony Polukhin: C++14 Reflections Without Macros, Markup nor External Tooling].
 Description of the [*BOOST_PFR_USE_LOOPHOLE == 1] technique by its inventor Alexandr Poltavsky [@http://alexpolt.github.io/type-loophole.html in his blog].
 
+[h2 Field name retrieval]
+
+# at compile-time:
+    * Get references to members of an object of type `T` in `constexpr` function
+    * Feed the reference from previous as a template parameter to a `constexpr` function with `template <auto member_ptr>`.
+      That function returns `__PRETTY_FUNCTION__` or some other vendor specific macro that prints the whole name of a function
+      along with the template arguments.
+    * The returned value from previous step contains the member name ([@https://godbolt.org/z/K4aWdcE9G godbolt example]). Do some
+      compiler specific parsing of the value and make a `std::string_view` that contains only the member name.
+# at run-time: return the `std::string_view` with the member name.
+
 [endsect]
 
 [section Acknowledgements]
 
-Many thanks to Bruno Dutra for showing the technique to precisely reflect aggregate initializable type in C++14 [@https://github.com/apolukhin/magic_get/issues/5 Manual type registering/structured bindings might be unnecessary].
+Many thanks to Bruno Dutra for showing the technique to precisely reflect aggregate initializable type in C++14 [@https://github.com/boostorg/pfr/issues/5 Manual type registering/structured bindings might be unnecessary].
 
 Many thanks to Alexandr Poltavsky for initial implementation the [*BOOST_PFR_USE_LOOPHOLE == 1] technique and for describing it [@http://alexpolt.github.io/type-loophole.html in his blog].
 

example/get.cpp

@@ -1,4 +1,4 @@
-// Copyright 2016-2022 Antony Polukhin
+// Copyright 2016-2026 Antony Polukhin
 
 // Distributed under the Boost Software License, Version 1.0.
 // (See the accompanying file LICENSE_1_0.txt

example/get_name.cpp

@@ -0,0 +1,43 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#include <boost/pfr/config.hpp>
+
+#if BOOST_PFR_CORE_NAME_ENABLED && BOOST_PFR_USE_CPP17
+//[pfr_example_get_name
+/*`
+    Since C++20 it's possible to read name of a structure field by index using Boost.PFR library.
+    The following example shows how to do it using [funcref boost::pfr::get_name].
+
+    Let's define some structure:
+*/
+#include <boost/pfr/core_name.hpp>
+
+struct foo {            // defining structure
+    int some_integer;
+    char c;
+};
+
+/*`
+    We can access field's names of that structure by index:
+*/
+constexpr std::string_view n1 = boost::pfr::get_name<0, foo>(); // returns "some_integer"
+constexpr std::string_view n2 = boost::pfr::get_name<1, foo>(); // returns "c"
+//] [/pfr_example_get_name]
+#endif
+
+int main() {
+#if BOOST_PFR_CORE_NAME_ENABLED && BOOST_PFR_USE_CPP17
+    if (n1 != "some_integer") return 1;
+    if (n2 != "c") return 2;
+#endif
+
+    return 0;
+}

example/motivating_example0.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

example/quick_examples.cpp

@@ -1,4 +1,4 @@
-// Copyright 2016-2022 Antony Polukhin
+// Copyright 2016-2026 Antony Polukhin
 
 // Distributed under the Boost Software License, Version 1.0.
 // (See the accompanying file LICENSE_1_0.txt
@@ -77,6 +77,35 @@ void test_examples() {
   }
 
 
+// Disabling for MSVC as it gives a hard error on using local types:
+//
+// error C7631:
+// 'boost::pfr::detail::do_not_use_PFR_with_local_types<test_examples::sample>':
+// variable with internal linkage declared but not defined
+#if BOOST_PFR_CORE_NAME_ENABLED && BOOST_PFR_USE_CPP17 && !defined(_MSC_VER)
+  {
+//[pfr_quick_examples_for_each_with_name
+    // Print the name and value
+    // of each element of the structure
+
+    struct test {
+        int n;
+        std::string str;
+    };
+
+    test var{42, "Hello, World!"};
+
+    // Outputs:
+    //  n: 42
+    //  str: Hello, World!
+    boost::pfr::for_each_field_with_name(var,
+      [](std::string_view name, const auto& value) {
+        std::cout << name << ": " << value << std::endl;
+    });
+//]
+  }
+#endif
+
   {
 //[pfr_quick_examples_tuple_size
     // Getting fields count of some structure
@@ -91,7 +120,7 @@ void test_examples() {
 
   {
 //[pfr_quick_examples_get
-    // Get field by index and assign new value to that field
+    // Get field by index/type and assign new value to that field
 
     struct sample {
         char c;
@@ -100,11 +129,33 @@ void test_examples() {
 
     sample var{};
     boost::pfr::get<1>(var) = 42.01f;
+    boost::pfr::get<char>(var) = 'A';
 
-    std::cout << var.f; // Outputs: 42.01
+    std::cout << var.c << var.f; // Outputs: A 42.01
 //]
   }
 
+// Disabling for MSVC as it gives a hard error on using local types:
+//
+// error C7631:
+// 'boost::pfr::detail::do_not_use_PFR_with_local_types<test_examples::sample>':
+// variable with internal linkage declared but not defined
+#if BOOST_PFR_CORE_NAME_ENABLED && BOOST_PFR_USE_CPP17 && !defined(_MSC_VER)
+  {
+//[pfr_quick_examples_get_name
+    // Get name of field by index
+
+    struct sample {
+        int f_int;
+        long f_long;
+    };
+
+    std::cout << boost::pfr::get_name<0, sample>()
+              << boost::pfr::get_name<1, sample>(); // Outputs: f_int f_long
+//]
+  }
+#endif
+
 #if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
   {
 //[pfr_quick_examples_structure_to_tuple

example/sample_printing.cpp

@@ -1,4 +1,4 @@
-// Copyright 2016-2022 Antony Polukhin
+// Copyright 2016-2026 Antony Polukhin
 
 // Distributed under the Boost Software License, Version 1.0.
 // (See the accompanying file LICENSE_1_0.txt

include/boost/pfr.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,7 +9,9 @@
 /// \file boost/pfr.hpp
 /// Includes all the Boost.PFR headers
 
+#include <boost/pfr/config.hpp>
 #include <boost/pfr/core.hpp>
+#include <boost/pfr/core_name.hpp>
 #include <boost/pfr/functions_for.hpp>
 #include <boost/pfr/functors.hpp>
 #include <boost/pfr/io.hpp>
@@ -17,5 +19,7 @@
 #include <boost/pfr/ops.hpp>
 #include <boost/pfr/ops_fields.hpp>
 #include <boost/pfr/tuple_size.hpp>
+#include <boost/pfr/traits_fwd.hpp>
+#include <boost/pfr/traits.hpp>
 
 #endif // BOOST_PFR_HPP

include/boost/pfr/config.hpp

@@ -0,0 +1,174 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+// Copyright (c) 2022 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_CONFIG_HPP
+#define BOOST_PFR_CONFIG_HPP
+#pragma once
+
+#if !defined(BOOST_USE_MODULES) && (__cplusplus >= 201402L || (defined(_MSC_VER) && defined(_MSVC_LANG) && _MSC_VER > 1900))
+#include <type_traits> // to get non standard platform macro definitions (__GLIBCXX__ for example)
+#endif
+
+#if defined(BOOST_USE_MODULES) || __cplusplus >= 202002L
+#include <version>
+#endif
+
+/// \file boost/pfr/config.hpp
+/// Contains all the macros that describe Boost.PFR configuration, like BOOST_PFR_ENABLED
+///
+/// \note This header file doesn't require C++14 Standard and supports all C++ compilers, even pre C++14 compilers (C++11, C++03...).
+
+// Reminder:
+//  * MSVC++ 14.2 _MSC_VER == 1927 <- Loophole is known to work (Visual Studio ????)
+//  * MSVC++ 14.1 _MSC_VER == 1916 <- Loophole is known to NOT work (Visual Studio 2017)
+//  * MSVC++ 14.0 _MSC_VER == 1900 (Visual Studio 2015)
+//  * MSVC++ 12.0 _MSC_VER == 1800 (Visual Studio 2013)
+
+#ifdef BOOST_PFR_NOT_SUPPORTED
+#   error Please, do not set BOOST_PFR_NOT_SUPPORTED value manually, use '-DBOOST_PFR_ENABLED=0' instead of it
+#endif
+
+#if defined(_MSC_VER)
+#   if !defined(_MSVC_LANG) || _MSC_VER <= 1900
+#       define BOOST_PFR_NOT_SUPPORTED 1
+#   endif
+#elif __cplusplus < 201402L
+#   define BOOST_PFR_NOT_SUPPORTED 1
+#endif
+
+#ifndef BOOST_PFR_USE_LOOPHOLE
+#   if defined(_MSC_VER)
+#       if _MSC_VER >= 1927
+#           define BOOST_PFR_USE_LOOPHOLE 1
+#       else
+#           define BOOST_PFR_USE_LOOPHOLE 0
+#       endif
+#   elif defined(__clang_major__) && __clang_major__ >= 8
+#       define BOOST_PFR_USE_LOOPHOLE 0
+#   else
+#       define BOOST_PFR_USE_LOOPHOLE 1
+#   endif
+#endif
+
+#ifndef BOOST_PFR_USE_CPP26
+#if __cpp_structured_bindings >= 202411L && __cpp_lib_forward_like >= 202207L
+#define BOOST_PFR_USE_CPP26 1
+#else
+#define BOOST_PFR_USE_CPP26 0
+#endif
+#endif
+
+#ifndef BOOST_PFR_USE_CPP17
+#   ifdef __cpp_structured_bindings
+#       define BOOST_PFR_USE_CPP17 1
+#   elif defined(_MSVC_LANG)
+#       if _MSVC_LANG >= 201703L
+#           define BOOST_PFR_USE_CPP17 1
+#       else
+#           define BOOST_PFR_USE_CPP17 0
+#       endif
+#   else
+#       define BOOST_PFR_USE_CPP17 0
+#   endif
+#endif
+
+#if (!BOOST_PFR_USE_CPP26 && !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_LOOPHOLE)
+#   if (defined(_MSC_VER) && _MSC_VER < 1916) ///< in Visual Studio 2017 v15.9 PFR library with classic engine normally works
+#      define BOOST_PFR_NOT_SUPPORTED 1
+#   endif
+#endif
+
+#ifndef BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE
+#   if defined(BOOST_USE_MODULES)
+#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 1
+// Assume that libstdc++ since GCC-7.3 does not have linear instantiation depth in std::make_integral_sequence
+#   elif defined( __GLIBCXX__) && __GLIBCXX__ >= 20180101
+#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 1
+#   elif defined(_MSC_VER)
+#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 1
+//# elif other known working lib
+#   else
+#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 0
+#   endif
+#endif
+
+#ifndef BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
+#   if  defined(__cpp_guaranteed_copy_elision) && (!defined(_MSC_VER) || _MSC_VER > 1928)
+#       define BOOST_PFR_HAS_GUARANTEED_COPY_ELISION 1
+#   else
+#       define BOOST_PFR_HAS_GUARANTEED_COPY_ELISION 0
+#   endif
+#endif
+
+#ifndef BOOST_PFR_ENABLE_IMPLICIT_REFLECTION
+#   if  defined(__cpp_lib_is_aggregate)
+#       define BOOST_PFR_ENABLE_IMPLICIT_REFLECTION 1
+#   else
+// There is no way to detect potential ability to be reflectable without std::is_aggregare
+#       define BOOST_PFR_ENABLE_IMPLICIT_REFLECTION 0
+#   endif
+#endif
+
+#ifndef BOOST_PFR_CORE_NAME_ENABLED
+#   if  (__cplusplus >= 202002L) || (defined(_MSVC_LANG) && (_MSVC_LANG >= 202002L))
+#       if (defined(__cpp_nontype_template_args) && __cpp_nontype_template_args >= 201911) \
+         || (defined(__clang_major__) && __clang_major__ >= 12)
+#           define BOOST_PFR_CORE_NAME_ENABLED 1
+#       else
+#           define BOOST_PFR_CORE_NAME_ENABLED 0
+#       endif
+#   else
+#       define BOOST_PFR_CORE_NAME_ENABLED 0
+#   endif
+#endif
+
+
+#ifndef BOOST_PFR_CORE_NAME_PARSING
+#   if defined(_MSC_VER) && !defined(__clang__)
+#       define BOOST_PFR_CORE_NAME_PARSING (sizeof("auto __cdecl boost::pfr::detail::name_of_field_impl<") - 1, sizeof(">(void) noexcept") - 1, backward("->"))
+#   elif defined(__clang__)
+#       define BOOST_PFR_CORE_NAME_PARSING (sizeof("auto boost::pfr::detail::name_of_field_impl() [MsvcWorkaround = ") - 1, sizeof("}]") - 1, backward("."))
+#   elif defined(__GNUC__)
+#       define BOOST_PFR_CORE_NAME_PARSING (sizeof("consteval auto boost::pfr::detail::name_of_field_impl() [with MsvcWorkaround = ") - 1, sizeof(")]") - 1, backward("::"))
+#   else
+// Default parser for other platforms... Just skip nothing!
+#       define BOOST_PFR_CORE_NAME_PARSING (0, 0, "")
+#   endif
+#endif
+
+#if defined(__has_cpp_attribute)
+#   if __has_cpp_attribute(maybe_unused)
+#       define BOOST_PFR_MAYBE_UNUSED [[maybe_unused]]
+#   endif
+#endif
+
+#ifndef BOOST_PFR_MAYBE_UNUSED
+#   define BOOST_PFR_MAYBE_UNUSED
+#endif
+
+#ifndef BOOST_PFR_ENABLED
+#   ifdef BOOST_PFR_NOT_SUPPORTED
+#       define BOOST_PFR_ENABLED 0
+#   else
+#       define BOOST_PFR_ENABLED 1
+#   endif
+#endif
+
+#undef BOOST_PFR_NOT_SUPPORTED
+
+#ifdef BOOST_PFR_INTERFACE_UNIT
+#   define BOOST_PFR_BEGIN_MODULE_EXPORT export {
+#   define BOOST_PFR_END_MODULE_EXPORT }
+#else
+#   define BOOST_PFR_BEGIN_MODULE_EXPORT
+#   define BOOST_PFR_END_MODULE_EXPORT
+#endif
+
+#if defined(BOOST_USE_MODULES) && !defined(BOOST_PFR_INTERFACE_UNIT)
+import boost.pfr;
+#endif
+
+#endif // BOOST_PFR_CONFIG_HPP

include/boost/pfr/core.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,18 +9,22 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #include <boost/pfr/detail/core.hpp>
 
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/stdtuple.hpp>
-#include <boost/pfr/detail/for_each_field_impl.hpp>
+#include <boost/pfr/detail/for_each_field.hpp>
 #include <boost/pfr/detail/make_integer_sequence.hpp>
 #include <boost/pfr/detail/tie_from_structure_tuple.hpp>
 
+#include <boost/pfr/tuple_size.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <type_traits>
 #include <utility>      // metaprogramming stuff
-
-#include <boost/pfr/tuple_size.hpp>
+#endif
 
 /// \file boost/pfr/core.hpp
 /// Contains all the basic tuple-like interfaces \forcedlink{get}, \forcedlink{tuple_size}, \forcedlink{tuple_element_t}, and others.
@@ -29,36 +33,53 @@
 
 namespace boost { namespace pfr {
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
 /// \brief Returns reference or const reference to a field with index `I` in \aggregate `val`.
+/// Overload taking the type `U` returns reference or const reference to a field
+/// with provided type `U` in \aggregate `val` if there's only one field of such type in `val`.
 ///
 /// \b Example:
 /// \code
 ///     struct my_struct { int i, short s; };
 ///     my_struct s {10, 11};
+///
 ///     assert(boost::pfr::get<0>(s) == 10);
 ///     boost::pfr::get<1>(s) = 0;
+///
+///     assert(boost::pfr::get<int>(s) == 10);
+///     boost::pfr::get<short>(s) = 11;
 /// \endcode
 template <std::size_t I, class T>
 constexpr decltype(auto) get(const T& val) noexcept {
-    return detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) );
+#if BOOST_PFR_USE_CPP26
+    const auto& [... members] = val;
+    return std::forward_like<const T &>(members...[I]);
+#else
+    return detail::sequence_tuple::get<I>(detail::tie_as_tuple(val));
+#endif
 }
 
-
 /// \overload get
 template <std::size_t I, class T>
 constexpr decltype(auto) get(T& val
-#if !BOOST_PFR_USE_CPP17
+#if !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26
     , std::enable_if_t<std::is_assignable<T, T>::value>* = nullptr
 #endif
 ) noexcept {
+#if BOOST_PFR_USE_CPP26
+    auto& [... members] = val;
+    return std::forward_like<T &>(members...[I]);
+#else
     return detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) );
+#endif
 }
 
-#if !BOOST_PFR_USE_CPP17
+#if !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26
 /// \overload get
 template <std::size_t I, class T>
 constexpr auto get(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nullptr) noexcept {
-    static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::get on non const non assignable type is allowed only in C++17");
+    static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::get on non const non assignable type is allowed only in C++17 and later");
     return 0;
 }
 #endif
@@ -66,8 +87,47 @@ constexpr auto get(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nul
 
 /// \overload get
 template <std::size_t I, class T>
-constexpr auto get(T&& val, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = 0) noexcept {
+constexpr auto get(T&& val, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = nullptr) noexcept {
+#if BOOST_PFR_USE_CPP26
+    auto&& [... members] = std::forward<T>(val);
+    return std::move(members...[I]);
+#else
     return std::move(detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) ));
+#endif
+}
+
+
+/// \overload get
+template <class U, class T>
+constexpr const U& get(const T& val) noexcept {
+    return detail::sequence_tuple::get_by_type_impl<const U&>( detail::tie_as_tuple(val) );
+}
+
+
+/// \overload get
+template <class U, class T>
+constexpr U& get(T& val
+#if !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26
+    , std::enable_if_t<std::is_assignable<T, T>::value>* = nullptr
+#endif
+) noexcept {
+    return detail::sequence_tuple::get_by_type_impl<U&>( detail::tie_as_tuple(val) );
+}
+
+#if !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26
+/// \overload get
+template <class U, class T>
+constexpr U& get(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nullptr) noexcept {
+    static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::get on non const non assignable type is allowed only in C++17 and later");
+    return 0;
+}
+#endif
+
+
+/// \overload get
+template <class U, class T>
+constexpr U&& get(T&& val, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = nullptr) noexcept {
+    return std::move(detail::sequence_tuple::get_by_type_impl<U&>( detail::tie_as_tuple(val) ));
 }
 
 
@@ -97,15 +157,20 @@ using tuple_element_t = typename tuple_element<I, T>::type;
 /// \code
 ///     struct my_struct { int i, short s; };
 ///     my_struct s {10, 11};
-///     std::tuple<int, short> t = make_tuple(s);
+///     std::tuple<int, short> t = boost::pfr::structure_to_tuple(s);
 ///     assert(get<0>(t) == 10);
 /// \endcode
 template <class T>
-constexpr auto structure_to_tuple(const T& val) noexcept {
+constexpr auto structure_to_tuple(const T& val) {
+#if BOOST_PFR_USE_CPP26
+    const auto& [... members] = val;
+    return std::make_tuple(members...);
+#else
     return detail::make_stdtuple_from_tietuple(
         detail::tie_as_tuple(val),
         detail::make_index_sequence< tuple_size_v<T> >()
     );
+#endif
 }
 
 
@@ -119,39 +184,47 @@ constexpr auto structure_to_tuple(const T& val) noexcept {
 ///     struct my_struct { int i, short s; };
 ///
 ///     const my_struct const_s{1, 2};
-///     std::apply(foo, structure_tie(const_s));
+///     std::apply(foo, boost::pfr::structure_tie(const_s));
 ///
 ///     my_struct s;
-///     structure_tie(s) = std::tuple<int, short>{10, 11};
+///     boost::pfr::structure_tie(s) = std::tuple<int, short>{10, 11};
 ///     assert(s.s == 11);
 /// \endcode
 template <class T>
 constexpr auto structure_tie(const T& val) noexcept {
+#if BOOST_PFR_USE_CPP26
+    const auto& [... members] = val;
+    return std::tie(std::forward_like<const T &>(members)...);
+#else
     return detail::make_conststdtiedtuple_from_tietuple(
         detail::tie_as_tuple(const_cast<T&>(val)),
         detail::make_index_sequence< tuple_size_v<T> >()
     );
+#endif
 }
 
 
 /// \overload structure_tie
 template <class T>
 constexpr auto structure_tie(T& val
-#if !BOOST_PFR_USE_CPP17
+#if !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26
     , std::enable_if_t<std::is_assignable<T, T>::value>* = nullptr
 #endif
 ) noexcept {
-    return detail::make_stdtiedtuple_from_tietuple(
-        detail::tie_as_tuple(val),
-        detail::make_index_sequence< tuple_size_v<T> >()
-    );
+#if BOOST_PFR_USE_CPP26
+    auto& [... members] = val;
+    return std::tie(std::forward_like<T &>(members)...);
+#else
+    return detail::make_stdtiedtuple_from_tietuple(detail::tie_as_tuple(val),
+                                                   detail::make_index_sequence<tuple_size_v<T> >());
+#endif
 }
 
-#if !BOOST_PFR_USE_CPP17
+#if !BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26
 /// \overload structure_tie
 template <class T>
 constexpr auto structure_tie(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nullptr) noexcept {
-    static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::structure_tie on non const non assignable type is allowed only in C++17");
+    static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::structure_tie on non const non assignable type is allowed only in C++17 and later modes");
     return 0;
 }
 #endif
@@ -159,7 +232,7 @@ constexpr auto structure_tie(T&, std::enable_if_t<!std::is_assignable<T, T>::val
 
 /// \overload structure_tie
 template <class T>
-constexpr auto structure_tie(T&&, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = 0) noexcept {
+constexpr auto structure_tie(T&&, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = nullptr) noexcept {
     static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::structure_tie on rvalue references is forbidden");
     return 0;
 }
@@ -177,29 +250,12 @@ constexpr auto structure_tie(T&&, std::enable_if_t< std::is_rvalue_reference<T&&
 /// \code
 ///     struct my_struct { int i, short s; };
 ///     int sum = 0;
-///     for_each_field(my_struct{20, 22}, [&sum](const auto& field) { sum += field; });
+///     boost::pfr::for_each_field(my_struct{20, 22}, [&sum](const auto& field) { sum += field; });
 ///     assert(sum == 42);
 /// \endcode
 template <class T, class F>
-void for_each_field(T&& value, F&& func) {
-    constexpr std::size_t fields_count_val = boost::pfr::detail::fields_count<std::remove_reference_t<T>>();
-
-    ::boost::pfr::detail::for_each_field_dispatcher(
-        value,
-        [f = std::forward<F>(func)](auto&& t) mutable {
-            // MSVC related workaround. Its lambdas do not capture constexprs.
-            constexpr std::size_t fields_count_val_in_lambda
-                = boost::pfr::detail::fields_count<std::remove_reference_t<T>>();
-
-            ::boost::pfr::detail::for_each_field_impl(
-                t,
-                std::forward<F>(f),
-                detail::make_index_sequence<fields_count_val_in_lambda>{},
-                std::is_rvalue_reference<T&&>{}
-            );
-        },
-        detail::make_index_sequence<fields_count_val>{}
-    );
+constexpr void for_each_field(T&& value, F&& func) {
+    return ::boost::pfr::detail::for_each_field(std::forward<T>(value), std::forward<F>(func));
 }
 
 /// \brief std::tie-like function that allows assigning to tied values from aggregates.
@@ -214,13 +270,17 @@ void for_each_field(T&& value, F&& func) {
 ///       return res;
 ///     }
 ///     auto [p, s] = f();
-///     tie_from_structure(p, s) = f();
+///     boost::pfr::tie_from_structure(p, s) = f();
 /// \endcode
 template <typename... Elements>
 constexpr detail::tie_from_structure_tuple<Elements...> tie_from_structure(Elements&... args) noexcept {
     return detail::tie_from_structure_tuple<Elements...>(args...);
 }
 
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_CORE_HPP

include/boost/pfr/core_name.hpp

@@ -0,0 +1,118 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#ifndef BOOST_PFR_CORE_NAME_HPP
+#define BOOST_PFR_CORE_NAME_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
+#include <boost/pfr/detail/core_name.hpp>
+
+#include <boost/pfr/detail/sequence_tuple.hpp>
+#include <boost/pfr/detail/stdarray.hpp>
+#include <boost/pfr/detail/make_integer_sequence.hpp>
+
+#include <boost/pfr/tuple_size.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <cstddef> // for std::size_t
+#endif
+
+/// \file boost/pfr/core_name.hpp
+/// Contains functions \forcedlink{get_name} and \forcedlink{names_as_array} to know which names each field of any \aggregate has.
+///
+/// \fnrefl for details.
+///
+/// \b Synopsis:
+
+namespace boost { namespace pfr {
+
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
+/// \brief Returns name of a field with index `I` in \aggregate `T`.
+///
+/// \b Example:
+/// \code
+///     struct my_struct { int i, short s; };
+///
+///     assert(boost::pfr::get_name<0, my_struct>() == "i");
+///     assert(boost::pfr::get_name<1, my_struct>() == "s");
+/// \endcode
+template <std::size_t I, class T>
+constexpr
+#ifdef BOOST_PFR_DOXYGEN_INVOKED
+std::string_view
+#else
+auto
+#endif
+get_name() noexcept {
+    return detail::get_name<T, I>();
+}
+
+// FIXME: implement this
+// template<class U, class T>
+// constexpr auto get_name() noexcept {
+//     return detail::sequence_tuple::get_by_type_impl<U>( detail::tie_as_names_tuple<T>() );
+// }
+
+/// \brief Creates a `std::array` from names of fields of an \aggregate `T`.
+///
+/// \b Example:
+/// \code
+///     struct my_struct { int i, short s; };
+///     std::array<std::string_view, 2> a = boost::pfr::names_as_array<my_struct>();
+///     assert(a[0] == "i");
+/// \endcode
+template <class T>
+constexpr
+#ifdef BOOST_PFR_DOXYGEN_INVOKED
+std::array<std::string_view, boost::pfr::tuple_size_v<T>>
+#else
+auto
+#endif
+names_as_array() noexcept {
+    return detail::make_stdarray_from_tietuple(
+        detail::tie_as_names_tuple<T>(),
+        detail::make_index_sequence< tuple_size_v<T> >()
+    );
+}
+
+
+/// Calls `func` for each field with its name of a `value`
+///
+/// \param func must have one of the following signatures:
+///     * any_return_type func(std::string_view name, U&& field)                // field of value is perfect forwarded to function
+///     * any_return_type func(std::string_view name, U&& field, std::size_t i)
+///     * any_return_type func(std::string_view name, U&& value, I i)           // Here I is an `std::integral_constant<size_t, field_index>`
+///
+/// \param value To each field of this variable will be the `func` applied.
+///
+/// \b Example:
+/// \code
+///     struct Toto { int a; char c; };
+///     Toto t {5, 'c'};
+///     auto print = [](std::string_view name, const auto& value){ std::cout << "Name: " << name << " Value: " << value << std::endl; };
+///     for_each_field_with_name(t, print);
+/// \endcode
+template <class T, class F>
+constexpr void for_each_field_with_name(T&& value, F&& func) {
+    return boost::pfr::detail::for_each_field_with_name(std::forward<T>(value), std::forward<F>(func));
+}
+
+BOOST_PFR_END_MODULE_EXPORT
+
+}} // namespace boost::pfr
+
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
+#endif // BOOST_PFR_CORE_NAME_HPP

include/boost/pfr/detail/cast_to_layout_compatible.hpp

@@ -1,75 +0,0 @@
-// Copyright (c) 2016-2022 Antony Polukhin
-//
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-
-#ifndef BOOST_PFR_DETAIL_CAST_TO_LAYOUT_COMPATIBLE_HPP
-#define BOOST_PFR_DETAIL_CAST_TO_LAYOUT_COMPATIBLE_HPP
-#pragma once
-
-#include <boost/pfr/detail/config.hpp>
-
-#include <type_traits>
-#include <utility>      // metaprogramming stuff
-#include <boost/pfr/detail/rvalue_t.hpp>
-
-namespace boost { namespace pfr { namespace detail {
-
-template <class T, class U>
-constexpr void static_assert_layout_compatible() noexcept {
-    static_assert(
-        std::alignment_of<T>::value == std::alignment_of<U>::value,
-        "====================> Boost.PFR: Alignment check failed, probably your structure has user-defined alignment for the whole structure or for some of the fields."
-    );
-    static_assert(sizeof(T) == sizeof(U), "====================> Boost.PFR: Size check failed, probably your structure has bitfields or user-defined alignment.");
-}
-
-/// @cond
-#ifdef __GNUC__
-#define MAY_ALIAS __attribute__((__may_alias__))
-#else
-#define MAY_ALIAS
-#endif
-/// @endcond
-
-template <class To, class From>
-MAY_ALIAS const To& cast_to_layout_compatible(const From& val) noexcept {
-    MAY_ALIAS const To* const t = reinterpret_cast<const To*>( std::addressof(val) );
-    detail::static_assert_layout_compatible<To, From>();
-    return *t;
-}
-
-template <class To, class From>
-MAY_ALIAS const volatile To& cast_to_layout_compatible(const volatile From& val) noexcept {
-    MAY_ALIAS const volatile To* const t = reinterpret_cast<const volatile To*>( std::addressof(val) );
-    detail::static_assert_layout_compatible<To, From>();
-    return *t;
-}
-
-
-template <class To, class From>
-MAY_ALIAS volatile To& cast_to_layout_compatible(volatile From& val) noexcept {
-    MAY_ALIAS volatile To* const t = reinterpret_cast<volatile To*>( std::addressof(val) );
-    detail::static_assert_layout_compatible<To, From>();
-    return *t;
-}
-
-
-template <class To, class From>
-MAY_ALIAS To& cast_to_layout_compatible(From& val) noexcept {
-    MAY_ALIAS To* const t = reinterpret_cast<To*>( std::addressof(val) );
-    detail::static_assert_layout_compatible<To, From>();
-    return *t;
-}
-
-#ifdef BOOST_PFR_DETAIL_STRICT_RVALUE_TESTING
-template <class To, class From>
-To&& cast_to_layout_compatible(rvalue_t<From> val) noexcept = delete;
-#endif
-
-#undef MAY_ALIAS
-
-
-}}} // namespace boost::pfr::detail
-
-#endif // BOOST_PFR_DETAIL_CAST_TO_LAYOUT_COMPATIBLE_HPP

include/boost/pfr/detail/config.hpp

@@ -1,4 +1,5 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
+// Copyright (c) 2022 Denis Mikhailov
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -7,85 +8,19 @@
 #define BOOST_PFR_DETAIL_CONFIG_HPP
 #pragma once
 
-#include <type_traits> // to get non standard platform macro definitions (__GLIBCXX__ for example)
+#include <boost/pfr/config.hpp>
 
-// Reminder:
-//  * MSVC++ 14.2 _MSC_VER == 1927 <- Loophole is known to work (Visual Studio ????)
-//  * MSVC++ 14.1 _MSC_VER == 1916 <- Loophole is known to NOT work (Visual Studio 2017)
-//  * MSVC++ 14.0 _MSC_VER == 1900 (Visual Studio 2015)
-//  * MSVC++ 12.0 _MSC_VER == 1800 (Visual Studio 2013)
+#if !BOOST_PFR_ENABLED
 
-#if defined(_MSC_VER)
-#   if !defined(_MSVC_LANG) || _MSC_VER <= 1900
-#       error Boost.PFR library requires more modern MSVC compiler.
-#   endif
-#elif __cplusplus < 201402L
-#   error Boost.PFR library requires at least C++14.
-#endif
-
-#ifndef BOOST_PFR_USE_LOOPHOLE
-#   if defined(_MSC_VER)
-#       if _MSC_VER >= 1927
-#           define BOOST_PFR_USE_LOOPHOLE 1
-#       else
-#           define BOOST_PFR_USE_LOOPHOLE 0
-#       endif
-#   elif defined(__clang_major__) && __clang_major__ >= 8
-#       define BOOST_PFR_USE_LOOPHOLE 0
-#   else
-#       define BOOST_PFR_USE_LOOPHOLE 1
-#   endif
-#endif
-
-#ifndef BOOST_PFR_USE_CPP17
-#   ifdef __cpp_structured_bindings
-#       define BOOST_PFR_USE_CPP17 1
-#   elif defined(_MSVC_LANG)
-#       if _MSVC_LANG >= 201703L
-#           define BOOST_PFR_USE_CPP17 1
-#       else
-#           define BOOST_PFR_USE_CPP17 0
-#       endif
-#   else
-#       define BOOST_PFR_USE_CPP17 0
-#   endif
-#endif
-
-#if (!BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_LOOPHOLE)
-#   if (defined(_MSC_VER) && _MSC_VER < 1916) ///< in Visual Studio 2017 v15.9 PFR library with classic engine normally works
-#      error Boost.PFR requires /std:c++latest or /std:c++17 flags on your compiler.
-#   endif
-#endif
-
-#ifndef BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE
-// Assume that libstdc++ since GCC-7.3 does not have linear instantiation depth in std::make_integral_sequence
-#   if defined( __GLIBCXX__) && __GLIBCXX__ >= 20180101
-#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 1
-#   elif defined(_MSC_VER)
-#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 1
-//# elif other known working lib
-#   else
-#       define BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE 0
-#   endif
-#endif
-
-#ifndef BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
-#   if  defined(__cpp_guaranteed_copy_elision) && (!defined(_MSC_VER) || _MSC_VER > 1928)
-#       define BOOST_PFR_HAS_GUARANTEED_COPY_ELISION 1
-#   else
-#       define BOOST_PFR_HAS_GUARANTEED_COPY_ELISION 0
-#   endif
-#endif
-
-#if defined(__has_cpp_attribute)
-#   if __has_cpp_attribute(maybe_unused)
-#       define BOOST_PFR_MAYBE_UNUSED [[maybe_unused]]
-#   endif
-#endif
-
-#ifndef BOOST_PFR_MAYBE_UNUSED
-#   define BOOST_PFR_MAYBE_UNUSED
-#endif
+#error Boost.PFR library is not supported in your environment.             \
+       Try one of the possible solutions:                                  \
+       1. try to take away an '-DBOOST_PFR_ENABLED=0', if it exists        \
+       2. enable C++14;                                                    \
+       3. enable C++17;                                                    \
+       4. update your compiler;                                            \
+       or disable this error by '-DBOOST_PFR_ENABLED=1' if you really know what are you doing.
 
+#endif // !BOOST_PFR_ENABLED
 
 #endif // BOOST_PFR_DETAIL_CONFIG_HPP
+

include/boost/pfr/detail/core.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -13,7 +13,9 @@
 // `boost::pfr::detail::for_each_field_dispatcher` functions.
 //
 // The whole PFR library is build on top of those two functions.
-#if BOOST_PFR_USE_CPP17
+#if BOOST_PFR_USE_CPP26
+#include <boost/pfr/detail/core26.hpp>
+#elif BOOST_PFR_USE_CPP17
 #   include <boost/pfr/detail/core17.hpp>
 #elif BOOST_PFR_USE_LOOPHOLE
 #   include <boost/pfr/detail/core14_loophole.hpp>

include/boost/pfr/detail/core14_classic.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,9 +9,6 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <type_traits>
-#include <utility>      // metaprogramming stuff
-
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/offset_based_getter.hpp>
 #include <boost/pfr/detail/fields_count.hpp>
@@ -21,6 +18,11 @@
 #include <boost/pfr/detail/size_t_.hpp>
 #include <boost/pfr/detail/rvalue_t.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#include <utility>      // metaprogramming stuff
+#endif
+
 #ifdef __clang__
 #   pragma clang diagnostic push
 #   pragma clang diagnostic ignored "-Wmissing-braces"
@@ -53,7 +55,7 @@ namespace typeid_conversions {
 #ifdef _MSC_VER
 #   pragma warning( push )
     // '<<': check operator precedence for possible error; use parentheses to clarify precedence
-#   pragma warning( disable : 4554 ) 
+#   pragma warning( disable : 4554 )
 #endif
 
 constexpr std::size_t native_types_mask = 31;
@@ -118,16 +120,16 @@ template <class Type> constexpr std::size_t type_to_id(identity<const Type*>) no
 template <class Type> constexpr std::size_t type_to_id(identity<const volatile Type*>) noexcept;
 template <class Type> constexpr std::size_t type_to_id(identity<volatile Type*>) noexcept;
 template <class Type> constexpr std::size_t type_to_id(identity<Type&>) noexcept;
-template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_enum<Type>::value>* = 0) noexcept;
-template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_empty<Type>::value>* = 0) noexcept;
-template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_union<Type>::value>* = 0) noexcept;
+template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_enum<Type>::value>* = nullptr) noexcept;
+template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_empty<Type>::value>* = nullptr) noexcept;
+template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_union<Type>::value>* = nullptr) noexcept;
 template <class Type> constexpr size_array<sizeof(Type) * 3> type_to_id(identity<Type>, std::enable_if_t<!std::is_enum<Type>::value && !std::is_empty<Type>::value && !std::is_union<Type>::value>* = 0) noexcept;
 
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_volatile_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_volatile_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ref_type> = 0) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_volatile_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_volatile_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ref_type> = nullptr) noexcept;
 
 
 ///////////////////// Definitions of type_to_id and id_to_type for fundamental types
@@ -346,7 +348,7 @@ constexpr size_array<N> get_type_offsets() noexcept {
     return offsets;
 }
 
-///////////////////// Returns array of typeids and zeros if construtor of a type accepts sizeof...(I) parameters
+///////////////////// Returns array of typeids and zeros if constructor of a type accepts sizeof...(I) parameters
 template <class T, std::size_t N, std::size_t... I>
 constexpr void* flat_type_to_array_of_type_ids(std::size_t* types, std::index_sequence<I...>) noexcept
 {

include/boost/pfr/detail/core14_loophole.hpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2017-2018 Alexandr Poltavsky, Antony Polukhin.
-// Copyright (c) 2019-2022 Antony Polukhin.
+// Copyright (c) 2019-2026 Antony Polukhin.
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -8,7 +8,7 @@
 // The Great Type Loophole (C++14)
 // Initial implementation by Alexandr Poltavsky, http://alexpolt.github.io
 //
-// Description: 
+// Description:
 //  The Great Type Loophole is a technique that allows to exchange type information with template
 //  instantiations. Basically you can assign and read type information during compile time.
 //  Here it is used to detect data members of a data type. I described it for the first time in
@@ -20,13 +20,10 @@
 
 #ifndef BOOST_PFR_DETAIL_CORE14_LOOPHOLE_HPP
 #define BOOST_PFR_DETAIL_CORE14_LOOPHOLE_HPP
+#pragma once
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <type_traits>
-#include <utility>
-
-#include <boost/pfr/detail/cast_to_layout_compatible.hpp> // still needed for enums
 #include <boost/pfr/detail/offset_based_getter.hpp>
 #include <boost/pfr/detail/fields_count.hpp>
 #include <boost/pfr/detail/make_flat_tuple_of_references.hpp>
@@ -35,6 +32,9 @@
 #include <boost/pfr/detail/rvalue_t.hpp>
 #include <boost/pfr/detail/unsafe_declval.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <utility>
+#endif
 
 #ifdef __clang__
 #   pragma clang diagnostic push

include/boost/pfr/detail/core17.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -6,6 +6,7 @@
 
 #ifndef BOOST_PFR_DETAIL_CORE17_HPP
 #define BOOST_PFR_DETAIL_CORE17_HPP
+#pragma once
 
 #include <boost/pfr/detail/core17_generated.hpp>
 #include <boost/pfr/detail/fields_count.hpp>
@@ -22,7 +23,7 @@ struct do_not_define_std_tuple_size_for_me {
 template <class T>
 constexpr bool do_structured_bindings_work() noexcept { // ******************************************* IN CASE OF ERROR READ THE FOLLOWING LINES IN boost/pfr/detail/core17.hpp FILE:
     T val{};
-    const auto& [a] = val; // ******************************************* IN CASE OF ERROR READ THE FOLLOWING LINES IN boost/pfr/detail/core17.hpp FILE:
+    auto& [a] = val; // ******************************************* IN CASE OF ERROR READ THE FOLLOWING LINES IN boost/pfr/detail/core17.hpp FILE:
 
     /****************************************************************************
     *
@@ -56,7 +57,7 @@ constexpr auto tie_as_tuple(T& val) noexcept {
 }
 
 template <class T, class F, std::size_t... I>
-void for_each_field_dispatcher(T& t, F&& f, std::index_sequence<I...>) {
+constexpr void for_each_field_dispatcher(T& t, F&& f, std::index_sequence<I...>) {
     static_assert(
         !std::is_union<T>::value,
         "====================> Boost.PFR: For safety reasons it is forbidden to reflect unions. See `Reflection of unions` section in the docs for more info."

include/boost/pfr/detail/core26.hpp

@@ -0,0 +1,39 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+// Copyright (c) 2025 Jean-Michaël Celerier
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// boost-no-inspect
+
+#ifndef BOOST_PFR_DETAIL_CORE26_HPP
+#define BOOST_PFR_DETAIL_CORE26_HPP
+#pragma once
+
+#include <boost/pfr/detail/sequence_tuple.hpp>
+
+namespace boost::pfr::detail {
+
+template<class T>
+constexpr auto tie_as_tuple(T &val) noexcept {
+    static_assert(!std::is_union<T>::value,
+                  "====================> Boost.PFR: For safety reasons it is forbidden to reflect "
+                  "unions. See `Reflection of unions` section in the docs for more info.");
+    auto &&[... members] = std::forward<T>(val);
+    return sequence_tuple::tuple<std::add_lvalue_reference_t<decltype(members)>...>{members...};
+}
+
+template <class T, class F, std::size_t... I>
+constexpr void for_each_field_dispatcher(T& t, F&& f, std::index_sequence<I...>) {
+    static_assert(
+        !std::is_union<T>::value,
+        "====================> Boost.PFR: For safety reasons it is forbidden to reflect unions. See `Reflection of unions` section in the docs for more info."
+    );
+    std::forward<F>(f)(
+        detail::tie_as_tuple(t)
+    );
+}
+
+} // namespace boost::pfr::detail
+
+#endif

include/boost/pfr/detail/core_name.hpp

@@ -0,0 +1,29 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#ifndef BOOST_PFR_DETAIL_CORE_NAME_HPP
+#define BOOST_PFR_DETAIL_CORE_NAME_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+// Each core_name provides `boost::pfr::detail::get_name` and
+// `boost::pfr::detail::tie_as_names_tuple` functions.
+//
+// The whole functional of extracting field's names is build on top of those
+// two functions.
+#if BOOST_PFR_CORE_NAME_ENABLED
+#include <boost/pfr/detail/core_name20_static.hpp>
+#else
+#include <boost/pfr/detail/core_name14_disabled.hpp>
+#endif
+
+#endif // BOOST_PFR_DETAIL_CORE_NAME_HPP
+

include/boost/pfr/detail/core_name14_disabled.hpp

@@ -0,0 +1,52 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#ifndef BOOST_PFR_DETAIL_CORE_NAME14_DISABLED_HPP
+#define BOOST_PFR_DETAIL_CORE_NAME14_DISABLED_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+#include <boost/pfr/detail/sequence_tuple.hpp>
+
+namespace boost { namespace pfr { namespace detail {
+
+template <class T, std::size_t I>
+constexpr auto get_name() noexcept {
+    static_assert(
+        sizeof(T) && false,
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
+    );
+
+    return nullptr;
+}
+
+template <class T>
+constexpr auto tie_as_names_tuple() noexcept {
+    static_assert(
+        sizeof(T) && false,
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
+    );
+
+    return detail::sequence_tuple::make_sequence_tuple();
+}
+
+
+template <class T, class F>
+constexpr void for_each_field_with_name(T&& /* value */, F&& /* func */) {
+    static_assert(
+        sizeof(T) && false,
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
+    );
+}
+
+}}} // namespace boost::pfr::detail
+
+#endif // BOOST_PFR_DETAIL_CORE_NAME14_DISABLED_HPP
+

include/boost/pfr/detail/core_name20_static.hpp

@@ -0,0 +1,263 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#ifndef BOOST_PFR_DETAIL_CORE_NAME20_STATIC_HPP
+#define BOOST_PFR_DETAIL_CORE_NAME20_STATIC_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#include <boost/pfr/detail/core.hpp>
+#include <boost/pfr/detail/fake_object.hpp>
+#include <boost/pfr/detail/fields_count.hpp>
+#include <boost/pfr/detail/for_each_field.hpp>
+#include <boost/pfr/detail/make_integer_sequence.hpp>
+#include <boost/pfr/detail/sequence_tuple.hpp>
+#include <boost/pfr/detail/stdarray.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#include <string_view>
+#include <array>
+#include <memory> // for std::addressof
+#endif
+
+namespace boost { namespace pfr { namespace detail {
+
+struct core_name_skip {
+    std::size_t size_at_begin;
+    std::size_t size_at_end;
+    bool is_backward;
+    std::string_view until_runtime;
+
+    consteval std::string_view apply(std::string_view sv) const noexcept {
+        // We use std::min here to make the compiler diagnostic shorter and
+        // cleaner in case of misconfigured BOOST_PFR_CORE_NAME_PARSING
+        sv.remove_prefix((std::min)(size_at_begin, sv.size()));
+        sv.remove_suffix((std::min)(size_at_end, sv.size()));
+        if (until_runtime.empty()) {
+            return sv;
+        }
+
+        const auto found = is_backward ? sv.rfind(until_runtime)
+                                       : sv.find(until_runtime);
+
+        const auto cut_until = found + until_runtime.size();
+        const auto safe_cut_until = (std::min)(cut_until, sv.size());
+        return sv.substr(safe_cut_until);
+    }
+};
+
+struct backward {
+    explicit consteval backward(std::string_view value) noexcept
+        : value(value)
+    {}
+
+    std::string_view value;
+};
+
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             std::string_view until_runtime) noexcept
+{
+    return core_name_skip{size_at_begin, size_at_end, false, until_runtime};
+}
+
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             backward until_runtime) noexcept
+{
+    return core_name_skip{size_at_begin, size_at_end, true, until_runtime.value};
+}
+
+// it might be compilation failed without this workaround sometimes
+// See https://github.com/llvm/llvm-project/issues/41751 for details
+template <class>
+consteval std::string_view clang_workaround(std::string_view value) noexcept
+{
+    return value;
+}
+
+template <class MsvcWorkaround, auto ptr>
+consteval auto name_of_field_impl() noexcept {
+    // Some of the following compiler specific macro may be defined only
+    // inside the function body:
+
+#ifndef BOOST_PFR_FUNCTION_SIGNATURE
+#   if defined(__FUNCSIG__)
+#       define BOOST_PFR_FUNCTION_SIGNATURE __FUNCSIG__
+#   elif defined(__PRETTY_FUNCTION__) || defined(__GNUC__) || defined(__clang__)
+#       define BOOST_PFR_FUNCTION_SIGNATURE __PRETTY_FUNCTION__
+#   else
+#       define BOOST_PFR_FUNCTION_SIGNATURE ""
+#   endif
+#endif
+
+    constexpr std::string_view sv = detail::clang_workaround<MsvcWorkaround>(BOOST_PFR_FUNCTION_SIGNATURE);
+    static_assert(!sv.empty(),
+        "====================> Boost.PFR: Field reflection parser configured in a wrong way. "
+        "Please define the BOOST_PFR_FUNCTION_SIGNATURE to a compiler specific macro, "
+        "that outputs the whole function signature including non-type template parameters."
+    );
+
+    constexpr auto skip = detail::make_core_name_skip BOOST_PFR_CORE_NAME_PARSING;
+    static_assert(skip.size_at_begin + skip.size_at_end + skip.until_runtime.size() < sv.size(),
+        "====================> Boost.PFR: Field reflection parser configured in a wrong way. "
+        "It attempts to skip more chars than available. "
+        "Please define BOOST_PFR_CORE_NAME_PARSING to correct values. See documentation section "
+        "'Limitations and Configuration' for more information."
+    );
+    constexpr auto fn = skip.apply(sv);
+    static_assert(
+        !fn.empty(),
+        "====================> Boost.PFR: Extraction of field name is misconfigured for your compiler. "
+        "It skipped all the input, leaving the field name empty. "
+        "Please define BOOST_PFR_CORE_NAME_PARSING to correct values. See documentation section "
+        "'Limitations and Configuration' for more information."
+    );
+    auto res = std::array<char, fn.size()+1>{};
+
+    auto* out = res.data();
+    for (auto x: fn) {
+        *out = x;
+        ++out;
+    }
+
+    return res;
+}
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wundefined-var-template"
+
+// clang 16 and earlier don't support address of non-static member as template parameter
+// but fortunately it's possible to use C++20 non-type template parameters in another way
+// even in clang 16 and more older clangs
+// all we need is to wrap pointer into 'clang_wrapper_t' and then pass it into template
+template <class T>
+struct clang_wrapper_t {
+    T v;
+};
+template <class T>
+clang_wrapper_t(T) -> clang_wrapper_t<T>;
+
+template <class T>
+constexpr auto make_clang_wrapper(const T& arg) noexcept {
+    return clang_wrapper_t{arg};
+}
+
+#else
+
+template <class T>
+constexpr const T& make_clang_wrapper(const T& arg) noexcept {
+    // It's everything OK with address of non-static member as template parameter support on this compiler
+    // so we don't need a wrapper here, just pass the pointer into template
+    return arg;
+}
+
+#endif
+
+template <class MsvcWorkaround, auto ptr>
+consteval auto name_of_field() noexcept {
+    // Sanity check: known field name must match the deduced one
+    static_assert(
+        sizeof(MsvcWorkaround)  // do not trigger if `name_of_field()` is not used
+        && std::string_view{
+            detail::name_of_field_impl<
+                core_name_skip, detail::make_clang_wrapper(std::addressof(
+                    detail::fake_object<core_name_skip>().size_at_begin
+                ))
+            >().data()
+        } == "size_at_begin",
+        "====================> Boost.PFR: Extraction of field name is misconfigured for your compiler. "
+        "It does not return the proper field name. "
+        "Please define BOOST_PFR_CORE_NAME_PARSING to correct values. See documentation section "
+        "'Limitations and Configuration' for more information."
+    );
+
+    return detail::name_of_field_impl<MsvcWorkaround, ptr>();
+}
+
+// Storing part of a string literal into an array minimizes the binary size.
+//
+// Without passing 'T' into 'name_of_field' different fields from different structures might have the same name!
+// See https://developercommunity.visualstudio.com/t/__FUNCSIG__-outputs-wrong-value-with-C/10458554 for details
+template <class T, std::size_t I>
+inline constexpr auto stored_name_of_field = detail::name_of_field<T,
+    detail::make_clang_wrapper(std::addressof(detail::sequence_tuple::get<I>(
+        detail::tie_as_tuple(detail::fake_object<T>())
+    )))
+>();
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+template <class T, std::size_t... I>
+constexpr auto tie_as_names_tuple_impl(std::index_sequence<I...>) noexcept {
+    return detail::sequence_tuple::make_sequence_tuple(std::string_view{stored_name_of_field<T, I>.data()}...);
+}
+
+template <class T, std::size_t I>
+constexpr std::string_view get_name() noexcept {
+    static_assert(
+        !std::is_union<T>::value,
+        "====================> Boost.PFR: For safety reasons it is forbidden to reflect unions. See `Reflection of unions` section in the docs for more info."
+    );
+    static_assert(
+        !std::is_array<T>::value,
+        "====================> Boost.PFR: It is impossible to extract name from old C array since it doesn't have named members"
+    );
+    static_assert(
+        sizeof(T) && (BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_CPP26),
+        "====================> Boost.PFR: Extraction of field's names is allowed only when the BOOST_PFR_USE_CPP17 or the BOOST_PFR_USE_CPP26 macro enabled."
+   );
+
+   return stored_name_of_field<T, I>.data();
+}
+
+template <class T>
+constexpr auto tie_as_names_tuple() noexcept {
+    static_assert(
+        !std::is_union<T>::value,
+        "====================> Boost.PFR: For safety reasons it is forbidden to reflect unions. See `Reflection of unions` section in the docs for more info."
+    );
+    static_assert(
+        !std::is_array<T>::value,
+        "====================> Boost.PFR: It is impossible to extract name from old C array since it doesn't have named members"
+    );
+    static_assert(
+        sizeof(T) && BOOST_PFR_USE_CPP17,
+        "====================> Boost.PFR: Extraction of field's names is allowed only when the BOOST_PFR_USE_CPP17 macro enabled."
+    );
+
+    return detail::tie_as_names_tuple_impl<T>(detail::make_index_sequence<detail::fields_count<T>()>{});
+}
+
+template <class T, class F>
+constexpr void for_each_field_with_name(T&& value, F&& func) {
+    return boost::pfr::detail::for_each_field(
+        std::forward<T>(value),
+        [f = std::forward<F>(func)](auto&& field, auto index) mutable {
+            using IndexType = decltype(index);
+            using FieldType = decltype(field);
+            constexpr auto name = boost::pfr::detail::get_name<std::remove_reference_t<T>, IndexType::value>();
+            if constexpr (std::is_invocable_v<F, std::string_view, FieldType, IndexType>) {
+                f(name, std::forward<FieldType>(field), index);
+            } else {
+                f(name, std::forward<FieldType>(field));
+            }
+        });
+}
+
+}}} // namespace boost::pfr::detail
+
+#endif // BOOST_PFR_DETAIL_CORE_NAME20_STATIC_HPP
+

include/boost/pfr/detail/detectors.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,15 +9,17 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <functional>
 #include <type_traits>
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 ///////////////////// `value` is true if Detector<Tleft, Tright> does not compile (SFINAE)
     struct can_not_apply{};
 
     template <template <class, class> class Detector, class Tleft, class Tright>
-    struct not_appliable {
+    struct not_applicable {
         static constexpr bool value = std::is_same<
             Detector<Tleft, Tright>,
             can_not_apply

include/boost/pfr/detail/fake_object.hpp

@@ -0,0 +1,54 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+// Copyright (c) 2024-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#ifndef BOOST_PFR_DETAIL_FAKE_OBJECT_HPP
+#define BOOST_PFR_DETAIL_FAKE_OBJECT_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#ifdef __clang__
+#   pragma clang diagnostic push
+#   pragma clang diagnostic ignored "-Wundefined-internal"
+#   pragma clang diagnostic ignored "-Wundefined-var-template"
+#endif
+
+namespace boost { namespace pfr { namespace detail {
+
+// This class has external linkage while T has not sure.
+template <class T>
+struct wrapper {
+    const T value;
+};
+
+// This variable servers as a link-time assert.
+// If linker requires it, then `fake_object()` is used at runtime.
+template <class T>
+extern const wrapper<T> do_not_use_PFR_with_local_types;
+
+// For returning non default constructible types, it's exclusively used in member name retrieval.
+//
+// Neither std::declval nor boost::pfr::detail::unsafe_declval are usable there.
+// This takes advantage of C++20 features, while boost::pfr::detail::unsafe_declval works
+// with the former standards.
+template <class T>
+constexpr const T& fake_object() noexcept {
+    return do_not_use_PFR_with_local_types<T>.value;
+}
+
+}}} // namespace boost::pfr::detail
+
+#ifdef __clang__
+#   pragma clang diagnostic pop
+#endif
+
+#endif // BOOST_PFR_DETAIL_FAKE_OBJECT_HPP
+

include/boost/pfr/detail/fields_count.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -12,9 +12,11 @@
 #include <boost/pfr/detail/size_t_.hpp>
 #include <boost/pfr/detail/unsafe_declval.hpp>
 
-#include <climits>      // CHAR_BIT
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <limits>
 #include <type_traits>
 #include <utility>      // metaprogramming stuff
+#endif
 
 #ifdef __clang__
 #   pragma clang diagnostic push
@@ -26,6 +28,11 @@
 
 namespace boost { namespace pfr { namespace detail {
 
+///////////////////// min without including <algorithm>
+constexpr std::size_t min_of_size_t(std::size_t a, std::size_t b) noexcept {
+    return b < a ? b : a;
+}
+
 ///////////////////// Structure that can be converted to reference to anything
 struct ubiq_lref_constructor {
     std::size_t ignore;
@@ -46,6 +53,14 @@ struct ubiq_rref_constructor {
     }
 };
 
+///////////////////// Hand-made is_complete<T> trait
+template <typename T, typename = void>
+struct is_complete : std::false_type
+{};
+
+template <typename T>
+struct is_complete<T, decltype(void(sizeof(T)))> : std::integral_constant<bool, true>
+{};
 
 #ifndef __cpp_lib_is_aggregate
 ///////////////////// Hand-made is_aggregate_initializable_n<T> trait
@@ -74,8 +89,16 @@ template <class T> struct is_single_field_and_aggregate_initializable<1, T>: std
 // Before C++20 aggregates could be constructed from `decltype(ubiq_?ref_constructor{I})...` but type traits report that
 // there's no constructor from `decltype(ubiq_?ref_constructor{I})...`
 // Special case for N == 1: `std::is_constructible<T, ubiq_?ref_constructor>` returns true if N == 1 and T is copy/move constructible.
-template <class T, std::size_t N>
+template <class T, std::size_t N, class /*Enable*/ = void>
 struct is_aggregate_initializable_n {
+    static constexpr bool value =
+           std::is_empty<T>::value
+        || std::is_array<T>::value
+    ;
+};
+
+template <class T, std::size_t N>
+struct is_aggregate_initializable_n<T, N, std::enable_if_t<std::is_class<T>::value && !std::is_empty<T>::value>> {
     template <std::size_t ...I>
     static constexpr bool is_not_constructible_n(std::index_sequence<I...>) noexcept {
         return (!std::is_constructible<T, decltype(ubiq_lref_constructor{I})...>::value && !std::is_constructible<T, decltype(ubiq_rref_constructor{I})...>::value)
@@ -83,12 +106,7 @@ struct is_aggregate_initializable_n {
         ;
     }
 
-    static constexpr bool value =
-           std::is_empty<T>::value
-        || std::is_array<T>::value
-        || std::is_fundamental<T>::value
-        || is_not_constructible_n(detail::make_index_sequence<N>{})
-    ;
+    static constexpr bool value = is_not_constructible_n(detail::make_index_sequence<N>{});
 };
 
 #endif // #ifndef __cpp_lib_is_aggregate
@@ -127,16 +145,16 @@ struct ubiq_rref_base_asserting {
     }
 };
 
-template <class T, std::size_t I0, std::size_t... I, class /*Enable*/ = typename std::enable_if<std::is_copy_constructible<T>::value>::type>
+template <class T, std::size_t I0, std::size_t... I, class /*Enable*/ = std::enable_if_t<std::is_copy_constructible<T>::value>>
 constexpr auto assert_first_not_base(std::index_sequence<I0, I...>) noexcept
-    -> typename std::add_pointer<decltype(T{ ubiq_lref_base_asserting<T>{}, ubiq_lref_constructor{I}... })>::type
+    -> std::add_pointer_t<decltype(T{ ubiq_lref_base_asserting<T>{}, ubiq_lref_constructor{I}... })>
 {
     return nullptr;
 }
 
-template <class T, std::size_t I0, std::size_t... I, class /*Enable*/ = typename std::enable_if<!std::is_copy_constructible<T>::value>::type>
+template <class T, std::size_t I0, std::size_t... I, class /*Enable*/ = std::enable_if_t<!std::is_copy_constructible<T>::value>>
 constexpr auto assert_first_not_base(std::index_sequence<I0, I...>) noexcept
-    -> typename std::add_pointer<decltype(T{ ubiq_rref_base_asserting<T>{}, ubiq_rref_constructor{I}... })>::type
+    -> std::add_pointer_t<decltype(T{ ubiq_rref_base_asserting<T>{}, ubiq_rref_constructor{I}... })>
 {
     return nullptr;
 }
@@ -147,17 +165,40 @@ constexpr void* assert_first_not_base(std::index_sequence<>) noexcept
     return nullptr;
 }
 
-///////////////////// Helper for SFINAE on fields count
-template <class T, std::size_t... I, class /*Enable*/ = typename std::enable_if<std::is_copy_constructible<T>::value>::type>
-constexpr auto enable_if_constructible_helper(std::index_sequence<I...>) noexcept
-    -> typename std::add_pointer<decltype(T{ ubiq_lref_constructor{I}... })>::type;
+template <class T, std::size_t N>
+constexpr void assert_first_not_base(int) noexcept {}
 
-template <class T, std::size_t... I, class /*Enable*/ = typename std::enable_if<!std::is_copy_constructible<T>::value>::type>
-constexpr auto enable_if_constructible_helper(std::index_sequence<I...>) noexcept
-    -> typename std::add_pointer<decltype(T{ ubiq_rref_constructor{I}... })>::type;
+template <class T, std::size_t N>
+constexpr auto assert_first_not_base(long) noexcept
+    -> std::enable_if_t<std::is_class<T>::value>
+{
+    detail::assert_first_not_base<T>(detail::make_index_sequence<N>{});
+}
 
-template <class T, std::size_t N, class /*Enable*/ = decltype( enable_if_constructible_helper<T>(detail::make_index_sequence<N>()) ) >
-using enable_if_constructible_helper_t = std::size_t;
+///////////////////// Helpers for initializable detection
+// Note that these take O(N) compile time and memory!
+template <class T, std::size_t... I, class /*Enable*/ = std::enable_if_t<std::is_copy_constructible<T>::value>>
+constexpr auto enable_if_initializable_helper(std::index_sequence<I...>) noexcept
+    -> std::add_pointer_t<decltype(T{ubiq_lref_constructor{I}...})>;
+
+template <class T, std::size_t... I, class /*Enable*/ = std::enable_if_t<!std::is_copy_constructible<T>::value>>
+constexpr auto enable_if_initializable_helper(std::index_sequence<I...>) noexcept
+    -> std::add_pointer_t<decltype(T{ubiq_rref_constructor{I}...})>;
+
+template <class T, std::size_t N, class U = std::size_t, class /*Enable*/ = decltype(detail::enable_if_initializable_helper<T>(detail::make_index_sequence<N>()))>
+using enable_if_initializable_helper_t = U;
+
+template <class T, std::size_t N>
+constexpr auto is_initializable(long) noexcept
+    -> detail::enable_if_initializable_helper_t<T, N, bool>
+{
+    return true;
+}
+
+template <class T, std::size_t N>
+constexpr bool is_initializable(int) noexcept {
+    return false;
+}
 
 ///////////////////// Helpers for range size detection
 template <std::size_t Begin, std::size_t Last>
@@ -166,125 +207,235 @@ using is_one_element_range = std::integral_constant<bool, Begin == Last>;
 using multi_element_range = std::false_type;
 using one_element_range = std::true_type;
 
-///////////////////// Non greedy fields count search. Templates instantiation depth is log(sizeof(T)), templates instantiation count is log(sizeof(T)).
-template <class T, std::size_t Begin, std::size_t Middle>
-constexpr std::size_t detect_fields_count(detail::one_element_range, long) noexcept {
+#if !BOOST_PFR_USE_CPP26
+///////////////////// Fields count next expected compiler limitation
+constexpr std::size_t fields_count_compiler_limitation_next(std::size_t n) noexcept {
+#if defined(_MSC_VER) && (_MSC_VER <= 1920)
+    if (n < 1024)
+        return 1024;
+#else
+    static_cast<void>(n);
+#endif
+    return (std::numeric_limits<std::size_t>::max)();
+}
+
+///////////////////// Fields count upper bound based on sizeof(T)
+template <class T>
+constexpr std::size_t fields_count_upper_bound_loose() noexcept {
+    return sizeof(T) * std::numeric_limits<unsigned char>::digits + 1 /* +1 for "Arrays of Length Zero" extension */;
+}
+
+///////////////////// Fields count binary search.
+// Template instantiation: depth is O(log(result)), count is O(log(result)), cost is O(result * log(result)).
+template <class T, std::size_t Begin, std::size_t Last>
+constexpr std::size_t fields_count_binary_search(detail::one_element_range, long) noexcept {
     static_assert(
-        Begin == Middle,
+        Begin == Last,
         "====================> Boost.PFR: Internal logic error."
     );
     return Begin;
 }
 
-template <class T, std::size_t Begin, std::size_t Middle>
-constexpr std::size_t detect_fields_count(detail::multi_element_range, int) noexcept;
+template <class T, std::size_t Begin, std::size_t Last>
+constexpr std::size_t fields_count_binary_search(detail::multi_element_range, int) noexcept;
 
-template <class T, std::size_t Begin, std::size_t Middle>
-constexpr auto detect_fields_count(detail::multi_element_range, long) noexcept
-    -> detail::enable_if_constructible_helper_t<T, Middle>
+template <class T, std::size_t Begin, std::size_t Last>
+constexpr auto fields_count_binary_search(detail::multi_element_range, long) noexcept
+    -> detail::enable_if_initializable_helper_t<T, (Begin + Last + 1) / 2>
 {
-    constexpr std::size_t next_v = Middle + (Middle - Begin + 1) / 2;
-    return detail::detect_fields_count<T, Middle, next_v>(detail::is_one_element_range<Middle, next_v>{}, 1L);
-}
-
-template <class T, std::size_t Begin, std::size_t Middle>
-constexpr std::size_t detect_fields_count(detail::multi_element_range, int) noexcept {
-    constexpr std::size_t next_v = Begin + (Middle - Begin) / 2;
-    return detail::detect_fields_count<T, Begin, next_v>(detail::is_one_element_range<Begin, next_v>{}, 1L);
-}
-
-///////////////////// Greedy search. Templates instantiation depth is log(sizeof(T)), templates instantiation count is log(sizeof(T))*T in worst case.
-template <class T, std::size_t N>
-constexpr auto detect_fields_count_greedy_remember(long) noexcept
-    -> detail::enable_if_constructible_helper_t<T, N>
-{
-    return N;
-}
-
-template <class T, std::size_t N>
-constexpr std::size_t detect_fields_count_greedy_remember(int) noexcept {
-    return 0;
+    constexpr std::size_t next_v = (Begin + Last + 1) / 2;
+    return detail::fields_count_binary_search<T, next_v, Last>(detail::is_one_element_range<next_v, Last>{}, 1L);
 }
 
 template <class T, std::size_t Begin, std::size_t Last>
-constexpr std::size_t detect_fields_count_greedy(detail::one_element_range) noexcept {
+constexpr std::size_t fields_count_binary_search(detail::multi_element_range, int) noexcept {
+    constexpr std::size_t next_v = (Begin + Last + 1) / 2 - 1;
+    return detail::fields_count_binary_search<T, Begin, next_v>(detail::is_one_element_range<Begin, next_v>{}, 1L);
+}
+
+template <class T, std::size_t Begin, std::size_t N>
+constexpr std::size_t fields_count_upper_bound(int, int) noexcept {
+    return N - 1;
+}
+
+template <class T, std::size_t Begin, std::size_t N>
+constexpr auto fields_count_upper_bound(long, long) noexcept
+    -> std::enable_if_t<(N > detail::fields_count_upper_bound_loose<T>()), std::size_t>
+{
+    static_assert(
+        !detail::is_initializable<T, detail::fields_count_upper_bound_loose<T>() + 1>(1L),
+        "====================> Boost.PFR: Types with user specified constructors (non-aggregate initializable types) are not supported.");
+    return detail::fields_count_upper_bound_loose<T>();
+}
+
+template <class T, std::size_t Begin, std::size_t N>
+constexpr auto fields_count_upper_bound(long, int) noexcept
+    -> detail::enable_if_initializable_helper_t<T, N>
+{
+    constexpr std::size_t next_optimal = Begin + (N - Begin) * 2;
+    constexpr std::size_t next = detail::min_of_size_t(next_optimal, detail::fields_count_compiler_limitation_next(N));
+    return detail::fields_count_upper_bound<T, Begin, next>(1L, 1L);
+}
+
+///////////////////// Fields count lower bound linear search.
+// Template instantiation: depth is O(log(result)), count is O(result), cost is O(result^2).
+template <class T, std::size_t Begin, std::size_t Last, class RangeSize, std::size_t Result>
+constexpr std::size_t fields_count_lower_bound(RangeSize, size_t_<Result>) noexcept {
+    return Result;
+}
+
+template <class T, std::size_t Begin, std::size_t Last>
+constexpr std::size_t fields_count_lower_bound(detail::one_element_range, size_t_<0> = {}) noexcept {
     static_assert(
         Begin == Last,
         "====================> Boost.PFR: Internal logic error."
     );
-    return detail::detect_fields_count_greedy_remember<T, Begin>(1L);
+    return detail::is_initializable<T, Begin>(1L) ? Begin : 0;
 }
 
 template <class T, std::size_t Begin, std::size_t Last>
-constexpr std::size_t detect_fields_count_greedy(detail::multi_element_range) noexcept {
+constexpr std::size_t fields_count_lower_bound(detail::multi_element_range, size_t_<0> = {}) noexcept {
+    // Binary partition to limit template depth.
     constexpr std::size_t middle = Begin + (Last - Begin) / 2;
-    constexpr std::size_t fields_count_big_range = detail::detect_fields_count_greedy<T, middle + 1, Last>(
-        detail::is_one_element_range<middle + 1, Last>{}
+    constexpr std::size_t result_maybe = detail::fields_count_lower_bound<T, Begin, middle>(
+        detail::is_one_element_range<Begin, middle>{}
     );
-
-    constexpr std::size_t small_range_begin = (fields_count_big_range ? 0 : Begin);
-    constexpr std::size_t small_range_last = (fields_count_big_range ? 0 : middle);
-    constexpr std::size_t fields_count_small_range = detail::detect_fields_count_greedy<T, small_range_begin, small_range_last>(
-        detail::is_one_element_range<small_range_begin, small_range_last>{}
+    return detail::fields_count_lower_bound<T, middle + 1, Last>(
+        detail::is_one_element_range<middle + 1, Last>{},
+        size_t_<result_maybe>{}
     );
-    return fields_count_big_range ? fields_count_big_range : fields_count_small_range;
 }
 
-///////////////////// Choosing between array size, greedy and non greedy search.
-template <class T, std::size_t N>
-constexpr auto detect_fields_count_dispatch(size_t_<N>, long, long) noexcept
-    -> typename std::enable_if<std::is_array<T>::value, std::size_t>::type
+template <class T, std::size_t Begin, std::size_t Result>
+constexpr std::size_t fields_count_lower_bound_unbounded(int, size_t_<Result>) noexcept {
+    return Result;
+}
+
+template <class T, std::size_t Begin>
+constexpr auto fields_count_lower_bound_unbounded(long, size_t_<0>) noexcept
+    -> std::enable_if_t<(Begin >= detail::fields_count_upper_bound_loose<T>()), std::size_t>
 {
-    return sizeof(T) / sizeof(typename std::remove_all_extents<T>::type);
+    static_assert(
+        detail::is_initializable<T, detail::fields_count_upper_bound_loose<T>()>(1L),
+        "====================> Boost.PFR: Type must be aggregate initializable.");
+    return detail::fields_count_upper_bound_loose<T>();
 }
 
-template <class T, std::size_t N>
-constexpr auto detect_fields_count_dispatch(size_t_<N>, long, int) noexcept
+template <class T, std::size_t Begin>
+constexpr std::size_t fields_count_lower_bound_unbounded(int, size_t_<0>) noexcept {
+    constexpr std::size_t last = detail::min_of_size_t(Begin * 2, detail::fields_count_upper_bound_loose<T>()) - 1;
+    constexpr std::size_t result_maybe = detail::fields_count_lower_bound<T, Begin, last>(
+        detail::is_one_element_range<Begin, last>{}
+    );
+    return detail::fields_count_lower_bound_unbounded<T, last + 1>(1L, size_t_<result_maybe>{});
+}
+#endif
+
+///////////////////// Choosing between array size, unbounded binary search, and linear search followed by unbounded binary search.
+template <class T>
+constexpr auto fields_count_dispatch(long, long, std::false_type /*are_preconditions_met*/) noexcept {
+    return 0;
+}
+
+template <class T>
+constexpr auto fields_count_dispatch(long, long, std::true_type /*are_preconditions_met*/) noexcept
+    -> std::enable_if_t<std::is_array<T>::value, std::size_t>
+{
+    return sizeof(T) / sizeof(std::remove_all_extents_t<T>);
+}
+
+#if BOOST_PFR_USE_CPP26
+template<class T>
+constexpr auto fields_count_dispatch_impl(const T &t) noexcept
+{
+    const auto &[... elts] = t;
+    return std::integral_constant<std::size_t, sizeof...(elts)>{};
+}
+
+template<class T>
+constexpr auto fields_count_dispatch(long, int, std::true_type /*are_preconditions_met*/) noexcept
+    -> std::enable_if_t<std::is_scalar<T>::value, std::size_t>
+{
+    return 1;
+}
+
+template<class T>
+constexpr auto fields_count_dispatch(int, int, std::true_type /*are_preconditions_met*/) noexcept
+{
+    return decltype(detail::fields_count_dispatch_impl(std::declval<const T &>()))::value;
+}
+#else
+template <class T>
+constexpr auto fields_count_dispatch(long, int, std::true_type /*are_preconditions_met*/) noexcept
     -> decltype(sizeof(T{}))
 {
-    constexpr std::size_t middle = N / 2 + 1;
-    return detail::detect_fields_count<T, 0, middle>(detail::multi_element_range{}, 1L);
+    constexpr std::size_t typical_fields_count = 4;
+    constexpr std::size_t last = detail::fields_count_upper_bound<T, typical_fields_count / 2, typical_fields_count>(1L, 1L);
+    return detail::fields_count_binary_search<T, 0, last>(detail::is_one_element_range<0, last>{}, 1L);
 }
 
-template <class T, std::size_t N>
-constexpr std::size_t detect_fields_count_dispatch(size_t_<N>, int, int) noexcept {
-    // T is not default aggregate initialzable. It means that at least one of the members is not default constructible,
-    // so we have to check all the aggregate initializations for T up to N parameters and return the bigest succeeded
-    // (we can not use binary search for detecting fields count).
-    return detail::detect_fields_count_greedy<T, 0, N>(detail::multi_element_range{});
+template <class T>
+constexpr std::size_t fields_count_dispatch(int, int, std::true_type /*are_preconditions_met*/) noexcept {
+    // T is not default aggregate initializable. This means that at least one of the members is not default-constructible.
+    // Use linear search to find the smallest valid initializer, after which we unbounded binary search for the largest.
+    constexpr std::size_t begin = detail::fields_count_lower_bound_unbounded<T, 1>(1L, size_t_<0>{});
+
+    constexpr std::size_t last = detail::fields_count_upper_bound<T, begin, begin + 1>(1L, 1L);
+    return detail::fields_count_binary_search<T, begin, last>(detail::is_one_element_range<begin, last>{}, 1L);
 }
+#endif
 
 ///////////////////// Returns fields count
 template <class T>
 constexpr std::size_t fields_count() noexcept {
     using type = std::remove_cv_t<T>;
 
+    constexpr bool type_is_complete = detail::is_complete<type>::value;
     static_assert(
-        !std::is_reference<type>::value,
+        type_is_complete,
+        "====================> Boost.PFR: Type must be complete."
+    );
+
+    constexpr bool type_is_not_a_reference = !std::is_reference<type>::value
+         || !type_is_complete // do not show assert if previous check failed
+    ;
+    static_assert(
+        type_is_not_a_reference,
         "====================> Boost.PFR: Attempt to get fields count on a reference. This is not allowed because that could hide an issue and different library users expect different behavior in that case."
     );
 
-#if !BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
-    static_assert(
+#if BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
+    constexpr bool type_fields_are_move_constructible = true;
+#else
+    constexpr bool type_fields_are_move_constructible =
         std::is_copy_constructible<std::remove_all_extents_t<type>>::value || (
             std::is_move_constructible<std::remove_all_extents_t<type>>::value
             && std::is_move_assignable<std::remove_all_extents_t<type>>::value
-        ),
+        )
+        || !type_is_not_a_reference // do not show assert if previous check failed
+    ;
+    static_assert(
+        type_fields_are_move_constructible,
         "====================> Boost.PFR: Type and each field in the type must be copy constructible (or move constructible and move assignable)."
     );
 #endif  // #if !BOOST_PFR_HAS_GUARANTEED_COPY_ELISION
 
+    constexpr bool type_is_not_polymorphic = !std::is_polymorphic<type>::value;
     static_assert(
-        !std::is_polymorphic<type>::value,
+        type_is_not_polymorphic,
         "====================> Boost.PFR: Type must have no virtual function, because otherwise it is not aggregate initializable."
     );
 
 #ifdef __cpp_lib_is_aggregate
-    static_assert(
+    constexpr bool type_is_aggregate =
         std::is_aggregate<type>::value             // Does not return `true` for built-in types.
-        || std::is_scalar<type>::value,
+        || std::is_scalar<type>::value;
+    static_assert(
+        type_is_aggregate,
         "====================> Boost.PFR: Type must be aggregate initializable."
     );
+#else
+    constexpr bool type_is_aggregate = true;
 #endif
 
 // Can't use the following. See the non_std_layout.cpp test.
@@ -295,26 +446,27 @@ constexpr std::size_t fields_count() noexcept {
 //    );
 //#endif
 
-#if defined(_MSC_VER) && (_MSC_VER <= 1920)
-    // Workaround for msvc compilers. Versions <= 1920 have a limit of max 1024 elements in template parameter pack
-    constexpr std::size_t max_fields_count = (sizeof(type) * CHAR_BIT >= 1024 ? 1024 : sizeof(type) * CHAR_BIT);
-#else
-    constexpr std::size_t max_fields_count = (sizeof(type) * CHAR_BIT); // We multiply by CHAR_BIT because the type may have bitfields in T
-#endif
-
-    constexpr std::size_t result = detail::detect_fields_count_dispatch<type>(size_t_<max_fields_count>{}, 1L, 1L);
-
-    detail::assert_first_not_base<type>(detail::make_index_sequence<result>{});
+    constexpr bool no_errors =
+        type_is_complete && type_is_not_a_reference && type_fields_are_move_constructible
+        && type_is_not_polymorphic && type_is_aggregate;
+    constexpr std::size_t result
+        = detail::fields_count_dispatch<type>(1L, 1L, std::integral_constant<bool, no_errors>{});
+    detail::assert_first_not_base<type, result>(1L);
 
 #ifndef __cpp_lib_is_aggregate
+    constexpr bool type_is_aggregate_initializable_n =
+        detail::is_aggregate_initializable_n<type, result>::value  // Does not return `true` for built-in types.
+        || std::is_scalar<type>::value;
     static_assert(
-        is_aggregate_initializable_n<type, result>::value,
+        type_is_aggregate_initializable_n,
         "====================> Boost.PFR: Types with user specified constructors (non-aggregate initializable types) are not supported."
     );
+#else
+    constexpr bool type_is_aggregate_initializable_n = true;
 #endif
 
     static_assert(
-        result != 0 || std::is_empty<type>::value || std::is_fundamental<type>::value || std::is_reference<type>::value,
+        result != 0 || std::is_empty<type>::value || std::is_fundamental<type>::value || std::is_reference<type>::value || !no_errors || !type_is_aggregate_initializable_n,
         "====================> Boost.PFR: If there's no other failed static asserts then something went wrong. Please report this issue to the github along with the structure you're reflecting."
     );
 

include/boost/pfr/detail/for_each_field.hpp

@@ -0,0 +1,65 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_DETAIL_FOR_EACH_FIELD_HPP
+#define BOOST_PFR_DETAIL_FOR_EACH_FIELD_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#include <boost/pfr/detail/core.hpp>
+#include <boost/pfr/detail/fields_count.hpp>
+#include <boost/pfr/detail/for_each_field_impl.hpp>
+#include <boost/pfr/detail/make_integer_sequence.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>      // metaprogramming stuff
+#include <utility>          // forward_like
+#endif
+
+namespace boost { namespace pfr { namespace detail {
+
+template <class T, class F>
+constexpr void for_each_field(T&& value, F&& func) {
+#if BOOST_PFR_USE_CPP26
+    using no_ref = std::remove_reference_t<T>;
+    if constexpr (std::is_aggregate_v<no_ref> || std::is_bounded_array_v<no_ref>) {
+        auto &&[... members] = value;
+        ::boost::pfr::detail::for_each_field_impl(value,
+                                                  std::forward<F>(func),
+                                                  std::make_index_sequence<sizeof...(members)>{},
+                                                  std::is_rvalue_reference<T &&>{});
+    } else {
+        ::boost::pfr::detail::for_each_field_impl(value,
+                                                  std::forward<F>(func),
+                                                  std::make_index_sequence<1>{},
+                                                  std::is_rvalue_reference<T &&>{});
+    }
+#else
+    constexpr std::size_t fields_count_val = boost::pfr::detail::fields_count<std::remove_reference_t<T>>();
+
+    ::boost::pfr::detail::for_each_field_dispatcher(
+        value,
+        [f = std::forward<F>(func)](auto&& t) mutable {
+            // MSVC related workaround. Its lambdas do not capture constexprs.
+            constexpr std::size_t fields_count_val_in_lambda
+                = boost::pfr::detail::fields_count<std::remove_reference_t<T>>();
+
+            ::boost::pfr::detail::for_each_field_impl(
+                t,
+                std::forward<F>(f),
+                detail::make_index_sequence<fields_count_val_in_lambda>{},
+                std::is_rvalue_reference<T&&>{}
+            );
+        },
+        detail::make_index_sequence<fields_count_val>{}
+    );
+#endif
+}
+
+}}} // namespace boost::pfr::detail
+
+
+#endif // BOOST_PFR_DETAIL_FOR_EACH_FIELD_HPP

include/boost/pfr/detail/for_each_field_impl.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,29 +9,54 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <utility>      // metaprogramming stuff
-
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/rvalue_t.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <utility>      // metaprogramming stuff
+#endif
+
 namespace boost { namespace pfr { namespace detail {
 
 template <std::size_t Index>
 using size_t_ = std::integral_constant<std::size_t, Index >;
 
 template <class T, class F, class I, class = decltype(std::declval<F>()(std::declval<T>(), I{}))>
-void for_each_field_impl_apply(T&& v, F&& f, I i, long) {
+constexpr void for_each_field_impl_apply(T&& v, F&& f, I i, long) {
     std::forward<F>(f)(std::forward<T>(v), i);
 }
 
 template <class T, class F, class I>
-void for_each_field_impl_apply(T&& v, F&& f, I /*i*/, int) {
+constexpr void for_each_field_impl_apply(T&& v, F&& f, I /*i*/, int) {
     std::forward<F>(f)(std::forward<T>(v));
 }
 
-#if !defined(__cpp_fold_expressions) || __cpp_fold_expressions < 201603
+#if BOOST_PFR_USE_CPP26
+template<class T, class F, std::size_t... I>
+constexpr void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, auto move_values) {
+    if constexpr (std::is_aggregate_v<T> || std::is_bounded_array_v<T>) {
+        auto &&[... members] = t;
+        if constexpr (move_values)
+            (detail::for_each_field_impl_apply(std::move(members...[I]),
+                                               std::forward<F>(f),
+                                               size_t_<I>{},
+                                               1L),
+             ...);
+        else
+            (detail::for_each_field_impl_apply(
+                 members... [I], std::forward<F>(f), size_t_<I> {}, 1L),
+             ...);
+    } else {
+        if constexpr (move_values)
+            (detail::for_each_field_impl_apply(std::move(t), std::forward<F>(f), size_t_<I>{}, 1L),
+             ...);
+        else
+            (detail::for_each_field_impl_apply(t, std::forward<F>(f), size_t_<I>{}, 1L), ...);
+    }
+}
+#elif !defined(__cpp_fold_expressions) || __cpp_fold_expressions < 201603
 template <class T, class F, std::size_t... I>
-void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::false_type /*move_values*/) {
+constexpr void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::false_type /*move_values*/) {
      const int v[] = {0, (
          detail::for_each_field_impl_apply(sequence_tuple::get<I>(t), std::forward<F>(f), size_t_<I>{}, 1L),
          0
@@ -41,7 +66,7 @@ void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::false_type
 
 
 template <class T, class F, std::size_t... I>
-void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::true_type /*move_values*/) {
+constexpr void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::true_type /*move_values*/) {
      const int v[] = {0, (
          detail::for_each_field_impl_apply(sequence_tuple::get<I>(std::move(t)), std::forward<F>(f), size_t_<I>{}, 1L),
          0
@@ -50,17 +75,15 @@ void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::true_type
 }
 #else
 template <class T, class F, std::size_t... I>
-void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::false_type /*move_values*/) {
+constexpr void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::false_type /*move_values*/) {
      (detail::for_each_field_impl_apply(sequence_tuple::get<I>(t), std::forward<F>(f), size_t_<I>{}, 1L), ...);
 }
 
 template <class T, class F, std::size_t... I>
-void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::true_type /*move_values*/) {
+constexpr void for_each_field_impl(T& t, F&& f, std::index_sequence<I...>, std::true_type /*move_values*/) {
      (detail::for_each_field_impl_apply(sequence_tuple::get<I>(std::move(t)), std::forward<F>(f), size_t_<I>{}, 1L), ...);
 }
 #endif
-
 }}} // namespace boost::pfr::detail
 
-
 #endif // BOOST_PFR_DETAIL_FOR_EACH_FIELD_IMPL_HPP

include/boost/pfr/detail/functional.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,11 +9,13 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <functional>
-#include <cstdint>
-
 #include <boost/pfr/detail/sequence_tuple.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <cstdint>
+#include <functional>
+#endif
+
 namespace boost { namespace pfr { namespace detail {
     template <std::size_t I, std::size_t N>
     struct equal_impl {

include/boost/pfr/detail/io.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,6 +10,8 @@
 #include <boost/pfr/detail/config.hpp>
 
 #include <boost/pfr/detail/sequence_tuple.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <iosfwd>       // stream operators
 #include <iomanip>
 
@@ -19,6 +21,8 @@
 #   endif
 #endif
 
+#endif
+
 namespace boost { namespace pfr { namespace detail {
 
 inline auto quoted_helper(const std::string& s) noexcept {

include/boost/pfr/detail/make_flat_tuple_of_references.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,11 +9,13 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <utility>      // metaprogramming stuff
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/rvalue_t.hpp>
 #include <boost/pfr/detail/make_integer_sequence.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <utility>      // metaprogramming stuff
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 

include/boost/pfr/detail/make_integer_sequence.hpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2018 Sergei Fedorov
-// Copyright (c) 2019-2022 Antony Polukhin
+// Copyright (c) 2019-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,9 +10,11 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <type_traits>
 #include <utility>
 #include <cstddef>
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 

include/boost/pfr/detail/offset_based_getter.hpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2017-2018 Chris Beck
-// Copyright (c) 2019-2022 Antony Polukhin
+// Copyright (c) 2019-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,13 +10,15 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <type_traits>
-#include <utility>
-#include <memory>  // std::addressof
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/rvalue_t.hpp>
 #include <boost/pfr/detail/size_t_.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#include <utility>
+#include <memory>  // std::addressof
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 
@@ -42,7 +44,7 @@ struct tuple_of_aligned_storage<sequence_tuple::tuple<Ts...>> {
   using type = sequence_tuple::tuple<internal_aligned_storage<sizeof(Ts),
 #if defined(__GNUC__) && __GNUC__ < 8 && !defined(__x86_64__) && !defined(__CYGWIN__)
       // Before GCC-8 the `alignof` was returning the optimal alignment rather than the minimal one.
-      // We have to adjust the alignemnt because otherwise we get the wrong offset.
+      // We have to adjust the alignment because otherwise we get the wrong offset.
       (alignof(Ts) > 4 ? 4 : alignof(Ts))
 #else
       alignof(Ts)

include/boost/pfr/detail/possible_reflectable.hpp

@@ -0,0 +1,51 @@
+// Copyright (c) 2022 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_DETAIL_POSSIBLE_REFLECTABLE_HPP
+#define BOOST_PFR_DETAIL_POSSIBLE_REFLECTABLE_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+#include <boost/pfr/traits_fwd.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits> // for std::is_aggregate
+#endif
+
+namespace boost { namespace pfr { namespace detail {
+
+///////////////////// Returns false when the type exactly wasn't be reflectable
+template <class T, class WhatFor>
+constexpr decltype(is_reflectable<T, WhatFor>::value) possible_reflectable(long) noexcept {
+    return is_reflectable<T, WhatFor>::value;
+}
+
+#if BOOST_PFR_ENABLE_IMPLICIT_REFLECTION
+
+template <class T, class WhatFor>
+constexpr bool possible_reflectable(int) noexcept {
+#   if  defined(__cpp_lib_is_aggregate)
+    using type = std::remove_cv_t<T>;
+    return std::is_aggregate<type>();
+#   else
+    return true;
+#   endif
+}
+
+#else
+
+template <class T, class WhatFor>
+constexpr bool possible_reflectable(int) noexcept {
+    // negative answer here won't change behaviour in PFR-dependent libraries(like Fusion)
+    return false;
+}
+
+#endif
+
+}}} // namespace boost::pfr::detail
+
+#endif // BOOST_PFR_DETAIL_POSSIBLE_REFLECTABLE_HPP
+
+

include/boost/pfr/detail/rvalue_t.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -7,8 +7,10 @@
 #define BOOST_PFR_DETAIL_RVALUE_T_HPP
 #pragma once
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <type_traits>
 #include <utility>      // std::enable_if_t
+#endif
 
 // This header provides aliases rvalue_t and lvalue_t.
 //

include/boost/pfr/detail/sequence_tuple.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,8 +10,10 @@
 #include <boost/pfr/detail/config.hpp>
 #include <boost/pfr/detail/make_integer_sequence.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <utility>      // metaprogramming stuff
 #include <cstddef>      // std::size_t
+#endif
 
 ///////////////////// Tuple that holds its values in the supplied order
 namespace boost { namespace pfr { namespace detail { namespace sequence_tuple {
@@ -50,35 +52,74 @@ struct tuple_base<std::index_sequence<> > {
 
 template <std::size_t N, class T>
 constexpr T& get_impl(base_from_member<N, T>& t) noexcept {
-    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
     return t.value;
 }
 
 template <std::size_t N, class T>
 constexpr const T& get_impl(const base_from_member<N, T>& t) noexcept {
-    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
     return t.value;
 }
 
 template <std::size_t N, class T>
 constexpr volatile T& get_impl(volatile base_from_member<N, T>& t) noexcept {
-    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
     return t.value;
 }
 
 template <std::size_t N, class T>
 constexpr const volatile T& get_impl(const volatile base_from_member<N, T>& t) noexcept {
-    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
     return t.value;
 }
 
 template <std::size_t N, class T>
 constexpr T&& get_impl(base_from_member<N, T>&& t) noexcept {
-    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
     return std::forward<T>(t.value);
 }
 
 
+template <class T, std::size_t N>
+constexpr T& get_by_type_impl(base_from_member<N, T>& t) noexcept {
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
+    return t.value;
+}
+
+template <class T, std::size_t N>
+constexpr const T& get_by_type_impl(const base_from_member<N, T>& t) noexcept {
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
+    return t.value;
+}
+
+template <class T, std::size_t N>
+constexpr volatile T& get_by_type_impl(volatile base_from_member<N, T>& t) noexcept {
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
+    return t.value;
+}
+
+template <class T, std::size_t N>
+constexpr const volatile T& get_by_type_impl(const volatile base_from_member<N, T>& t) noexcept {
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
+    return t.value;
+}
+
+template <class T, std::size_t N>
+constexpr T&& get_by_type_impl(base_from_member<N, T>&& t) noexcept {
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
+    return std::forward<T>(t.value);
+}
+
+template <class T, std::size_t N>
+constexpr const T&& get_by_type_impl(const base_from_member<N, T>&& t) noexcept {
+    // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn,clang-analyzer-core.CallAndMessage)
+    return std::forward<T>(t.value);
+}
+
+
+
+
 template <class ...Values>
 struct tuple: tuple_base<
     detail::index_sequence_for<Values...>,
@@ -88,6 +129,9 @@ struct tuple: tuple_base<
         detail::index_sequence_for<Values...>,
         Values...
     >::tuple_base;
+
+    constexpr static std::size_t size() noexcept { return sizeof...(Values); }
+    constexpr static bool empty() noexcept { return size() == 0; }
 };
 
 
@@ -126,6 +170,10 @@ using tuple_element = std::remove_reference< decltype(
         ::boost::pfr::detail::sequence_tuple::get<I>( std::declval<T>() )
     ) >;
 
+template <class... Args>
+constexpr auto make_sequence_tuple(Args... args) noexcept {
+    return ::boost::pfr::detail::sequence_tuple::tuple<Args...>{ args... };
+}
 
 }}}} // namespace boost::pfr::detail::sequence_tuple
 

include/boost/pfr/detail/size_array.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,7 +9,9 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <cstddef>      // metaprogramming stuff
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <cstddef>
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 

include/boost/pfr/detail/size_t_.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -7,6 +7,11 @@
 #define BOOST_PFR_DETAIL_SIZE_T_HPP
 #pragma once
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#include <cstddef>
+#endif
+
 namespace boost { namespace pfr { namespace detail {
 
 ///////////////////// General utility stuff

include/boost/pfr/detail/stdarray.hpp

@@ -0,0 +1,41 @@
+// Copyright (c) 2023 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_DETAIL_STDARRAY_HPP
+#define BOOST_PFR_DETAIL_STDARRAY_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#include <boost/pfr/detail/sequence_tuple.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <array>
+#if BOOST_PFR_CORE_NAME_ENABLED
+#   include <string_view>
+#endif
+#include <utility> // metaprogramming stuff
+#endif
+
+namespace boost { namespace pfr { namespace detail {
+
+#if BOOST_PFR_CORE_NAME_ENABLED
+template <class T, std::size_t... I>
+constexpr auto make_stdarray_from_tietuple(const T& t, std::index_sequence<I...>) noexcept {
+    return std::array<std::string_view, sizeof...(I)>{
+        boost::pfr::detail::sequence_tuple::get<I>(t)...
+    };
+}
+#else
+template <class T, std::size_t... I>
+constexpr auto make_stdarray_from_tietuple(const T&, std::index_sequence<I...>) noexcept {
+    return nullptr;
+}
+#endif
+
+}}} // namespace boost::pfr::detail
+
+#endif // BOOST_PFR_DETAIL_STDARRAY_HPP
+

include/boost/pfr/detail/stdtuple.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,15 +9,18 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#include <boost/pfr/detail/sequence_tuple.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <utility>      // metaprogramming stuff
 #include <tuple>
-
-#include <boost/pfr/detail/sequence_tuple.hpp>
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 
 template <class T, std::size_t... I>
-constexpr auto make_stdtuple_from_tietuple(const T& t, std::index_sequence<I...>) noexcept {
+constexpr auto make_stdtuple_from_tietuple(const T& t, std::index_sequence<I...>) {
+    (void)t;  // workaround for MSVC 14.1 `warning C4100: 't': unreferenced formal parameter`
     return std::make_tuple(
         boost::pfr::detail::sequence_tuple::get<I>(t)...
     );
@@ -25,6 +28,7 @@ constexpr auto make_stdtuple_from_tietuple(const T& t, std::index_sequence<I...>
 
 template <class T, std::size_t... I>
 constexpr auto make_stdtiedtuple_from_tietuple(const T& t, std::index_sequence<I...>) noexcept {
+    (void)t;  // workaround for MSVC 14.1 `warning C4100: 't': unreferenced formal parameter`
     return std::tie(
         boost::pfr::detail::sequence_tuple::get<I>(t)...
     );
@@ -32,6 +36,7 @@ constexpr auto make_stdtiedtuple_from_tietuple(const T& t, std::index_sequence<I
 
 template <class T, std::size_t... I>
 constexpr auto make_conststdtiedtuple_from_tietuple(const T& t, std::index_sequence<I...>) noexcept {
+    (void)t;  // workaround for MSVC 14.1 `warning C4100: 't': unreferenced formal parameter`
     return std::tuple<
         std::add_lvalue_reference_t<std::add_const_t<
             std::remove_reference_t<decltype(boost::pfr::detail::sequence_tuple::get<I>(t))>

include/boost/pfr/detail/tie_from_structure_tuple.hpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2018 Adam Butcher, Antony Polukhin
-// Copyright (c) 2019-2022 Antony Polukhin
+// Copyright (c) 2019-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -16,7 +16,9 @@
 #include <boost/pfr/tuple_size.hpp>
 #include <boost/pfr/detail/make_integer_sequence.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <tuple>
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 

include/boost/pfr/detail/unsafe_declval.hpp

@@ -1,14 +1,17 @@
-// Copyright (c) 2019-2022 Antony Polukhin.
+// Copyright (c) 2019-2026 Antony Polukhin.
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
 #ifndef BOOST_PFR_DETAIL_UNSAFE_DECLVAL_HPP
 #define BOOST_PFR_DETAIL_UNSAFE_DECLVAL_HPP
+#pragma once
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
 #include <type_traits>
+#endif
 
 namespace boost { namespace pfr { namespace detail {
 
@@ -24,9 +27,19 @@ template <class T>
 constexpr T unsafe_declval() noexcept {
     report_if_you_see_link_error_with_this_function();
 
-    typename std::remove_reference<T>::type* ptr = 0;
+#ifdef BOOST_PFR_USE_LEGACY_UNSAFE_DECLVAL_IMPLEMENTATION
+    typename std::remove_reference<T>::type* ptr = nullptr;
     ptr += 42; // suppresses 'null pointer dereference' warnings
     return static_cast<T>(*ptr);
+#else
+    // Looks like `static_cast<T>(*ptr)` to prvalue fails on clang in C++26.
+    // If this new implementation does not work for some cases, please, fill a
+    // bug report and feel free to
+    // define BOOST_PFR_USE_LEGACY_UNSAFE_DECLVAL_IMPLEMENTATION.
+    using func_ptr_t = T(*)();
+    func_ptr_t ptr = nullptr;
+    return ptr();
+#endif
 }
 
 }}} // namespace boost::pfr::detail

include/boost/pfr/functions_for.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,8 +9,10 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
 #include <boost/pfr/ops_fields.hpp>
 #include <boost/pfr/io_fields.hpp>
+#endif
 
 /// \file boost/pfr/functions_for.hpp
 /// Contains BOOST_PFR_FUNCTIONS_FOR macro that defined comparison and stream operators for T along with hash_value function.

include/boost/pfr/functors.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,6 +9,8 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #include <boost/pfr/ops.hpp>
 
 #include <boost/pfr/detail/functional.hpp>
@@ -35,6 +37,8 @@
 /// \b Synopsis:
 namespace boost { namespace pfr {
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
 ///////////////////// Comparisons
 
 /// \brief std::equal_to like comparator that returns \forcedlink{eq}(x, y)
@@ -216,6 +220,10 @@ template <class T> struct hash {
     }
 };
 
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_FUNCTORS_HPP

include/boost/pfr/io.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,6 +9,8 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #include <boost/pfr/detail/detectors.hpp>
 #include <boost/pfr/io_fields.hpp>
 
@@ -38,25 +40,25 @@ namespace detail {
 ///////////////////// Helper typedefs
     template <class Stream, class Type>
     using enable_not_ostreamable_t = std::enable_if_t<
-        not_appliable<ostreamable_detector, Stream&, const std::remove_reference_t<Type>&>::value,
+        not_applicable<ostreamable_detector, Stream&, const std::remove_reference_t<Type>&>::value,
         Stream&
     >;
 
     template <class Stream, class Type>
     using enable_not_istreamable_t = std::enable_if_t<
-        not_appliable<istreamable_detector, Stream&, Type&>::value,
+        not_applicable<istreamable_detector, Stream&, Type&>::value,
         Stream&
     >;
 
     template <class Stream, class Type>
     using enable_ostreamable_t = std::enable_if_t<
-        !not_appliable<ostreamable_detector, Stream&, const std::remove_reference_t<Type>&>::value,
+        !not_applicable<ostreamable_detector, Stream&, const std::remove_reference_t<Type>&>::value,
         Stream&
     >;
 
     template <class Stream, class Type>
     using enable_istreamable_t = std::enable_if_t<
-        !not_appliable<istreamable_detector, Stream&, Type&>::value,
+        !not_applicable<istreamable_detector, Stream&, Type&>::value,
         Stream&
     >;
 
@@ -67,6 +69,8 @@ struct io_impl {
     T value;
 };
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
 template <class Char, class Traits, class T>
 enable_not_ostreamable_t<std::basic_ostream<Char, Traits>, T> operator<<(std::basic_ostream<Char, Traits>& out, io_impl<T>&& x) {
     return out << boost::pfr::io_fields(std::forward<T>(x.value));
@@ -87,19 +91,23 @@ enable_istreamable_t<std::basic_istream<Char, Traits>, T> operator>>(std::basic_
     return in >> x.value;
 }
 
+BOOST_PFR_END_MODULE_EXPORT
+
 } // namespace detail
 
-/// IO manupulator to read/write \aggregate `value` using its IO stream operators or using \forcedlink{io_fields} if operators are not awailable.
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
+/// IO manipulator to read/write \aggregate `value` using its IO stream operators or using \forcedlink{io_fields} if operators are not available.
 ///
 /// \b Example:
 /// \code
 ///     struct my_struct { int i; short s; };
-///     my_struct s;
+///     my_struct x;
 ///     std::stringstream ss;
 ///     ss << "{ 12, 13 }";
-///     ss >> boost::pfr::io(s);
-///     assert(s.i == 12);
-///     assert(s.i == 13);
+///     ss >> boost::pfr::io(x);
+///     assert(x.i == 12);
+///     assert(x.s == 13);
 /// \endcode
 ///
 /// \customio
@@ -108,6 +116,10 @@ auto io(T&& value) noexcept {
     return detail::io_impl<T>{std::forward<T>(value)};
 }
 
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_IO_HPP

include/boost/pfr/io_fields.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,18 +10,21 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #include <boost/pfr/detail/core.hpp>
-
-#include <type_traits>
-#include <utility>      // metaprogramming stuff
-
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/io.hpp>
 #include <boost/pfr/detail/make_integer_sequence.hpp>
 #include <boost/pfr/tuple_size.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#include <utility>      // metaprogramming stuff
+#endif
+
 /// \file boost/pfr/io_fields.hpp
-/// Contains IO manupulator \forcedlink{io_fields} to read/write \aggregate `value` field-by-field.
+/// Contains IO manipulator \forcedlink{io_fields} to read/write any \aggregate field-by-field.
 ///
 /// \b Example:
 /// \code
@@ -52,6 +55,7 @@ struct io_fields_impl {
     T value;
 };
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
 
 template <class Char, class Traits, class T>
 std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& out, io_fields_impl<const T&>&& x) {
@@ -130,9 +134,13 @@ std::basic_istream<Char, Traits>& operator>>(std::basic_istream<Char, Traits>& i
     return in;
 }
 
+BOOST_PFR_END_MODULE_EXPORT
+
 } // namespace detail
 
-/// IO manupulator to read/write \aggregate `value` field-by-field.
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
+/// IO manipulator to read/write \aggregate `value` field-by-field.
 ///
 /// \b Example:
 /// \code
@@ -159,6 +167,10 @@ auto io_fields(T&& value) noexcept {
     return detail::io_fields_impl<T>{std::forward<T>(value)};
 }
 
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_IO_FIELDS_HPP

include/boost/pfr/ops.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,6 +9,8 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #include <boost/pfr/detail/detectors.hpp>
 #include <boost/pfr/ops_fields.hpp>
 
@@ -40,13 +42,13 @@ namespace detail {
 ///////////////////// Helper typedefs that are used by all the ops
     template <template <class, class> class Detector, class T, class U>
     using enable_not_comp_base_t = std::enable_if_t<
-        not_appliable<Detector, T const&, U const&>::value,
+        not_applicable<Detector, T const&, U const&>::value,
         bool
     >;
 
     template <template <class, class> class Detector, class T, class U>
     using enable_comp_base_t = std::enable_if_t<
-        !not_appliable<Detector, T const&, U const&>::value,
+        !not_applicable<Detector, T const&, U const&>::value,
         bool
     >;
 ///////////////////// std::enable_if_t like functions that enable only if types do not support operation
@@ -59,7 +61,7 @@ namespace detail {
     template <class T, class U> using enable_not_ge_comp_t = enable_not_comp_base_t<comp_ge_detector, T, U>;
 
     template <class T> using enable_not_hashable_t = std::enable_if_t<
-        not_appliable<hash_detector, const T&, const T&>::value,
+        not_applicable<hash_detector, const T&, const T&>::value,
         std::size_t
     >;
 ///////////////////// std::enable_if_t like functions that enable only if types do support operation
@@ -72,13 +74,14 @@ namespace detail {
     template <class T, class U> using enable_ge_comp_t = enable_comp_base_t<comp_ge_detector, T, U>;
 
     template <class T> using enable_hashable_t = std::enable_if_t<
-        !not_appliable<hash_detector, const T&, const T&>::value,
+        !not_applicable<hash_detector, const T&, const T&>::value,
         std::size_t
     >;
 } // namespace detail
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
 
-/// \brief Compares lhs and rhs for equality using their own comparison and conversion operators; if no operators avalable returns \forcedlink{eq_fields}(lhs, rhs).
+/// \brief Compares lhs and rhs for equality using their own comparison and conversion operators; if no operators available returns \forcedlink{eq_fields}(lhs, rhs).
 ///
 /// \returns true if lhs is equal to rhs; false otherwise
 template <class T, class U>
@@ -93,7 +96,7 @@ constexpr detail::enable_eq_comp_t<T, U> eq(const T& lhs, const U& rhs) {
 }
 
 
-/// \brief Compares lhs and rhs for inequality using their own comparison and conversion operators; if no operators avalable returns \forcedlink{ne_fields}(lhs, rhs).
+/// \brief Compares lhs and rhs for inequality using their own comparison and conversion operators; if no operators available returns \forcedlink{ne_fields}(lhs, rhs).
 ///
 /// \returns true if lhs is not equal to rhs; false otherwise
 template <class T, class U>
@@ -108,7 +111,7 @@ constexpr detail::enable_ne_comp_t<T, U> ne(const T& lhs, const U& rhs) {
 }
 
 
-/// \brief Compares lhs and rhs for less-than using their own comparison and conversion operators; if no operators avalable returns \forcedlink{lt_fields}(lhs, rhs).
+/// \brief Compares lhs and rhs for less-than using their own comparison and conversion operators; if no operators available returns \forcedlink{lt_fields}(lhs, rhs).
 ///
 /// \returns true if lhs is less than rhs; false otherwise
 template <class T, class U>
@@ -123,7 +126,7 @@ constexpr detail::enable_lt_comp_t<T, U> lt(const T& lhs, const U& rhs) {
 }
 
 
-/// \brief Compares lhs and rhs for greater-than using their own comparison and conversion operators; if no operators avalable returns \forcedlink{lt_fields}(lhs, rhs).
+/// \brief Compares lhs and rhs for greater-than using their own comparison and conversion operators; if no operators available returns \forcedlink{lt_fields}(lhs, rhs).
 ///
 /// \returns true if lhs is greater than rhs; false otherwise
 template <class T, class U>
@@ -138,7 +141,7 @@ constexpr detail::enable_gt_comp_t<T, U> gt(const T& lhs, const U& rhs) {
 }
 
 
-/// \brief Compares lhs and rhs for less-equal using their own comparison and conversion operators; if no operators avalable returns \forcedlink{le_fields}(lhs, rhs).
+/// \brief Compares lhs and rhs for less-equal using their own comparison and conversion operators; if no operators available returns \forcedlink{le_fields}(lhs, rhs).
 ///
 /// \returns true if lhs is less or equal to rhs; false otherwise
 template <class T, class U>
@@ -153,7 +156,7 @@ constexpr detail::enable_le_comp_t<T, U> le(const T& lhs, const U& rhs) {
 }
 
 
-/// \brief Compares lhs and rhs for greater-equal using their own comparison and conversion operators; if no operators avalable returns \forcedlink{ge_fields}(lhs, rhs).
+/// \brief Compares lhs and rhs for greater-equal using their own comparison and conversion operators; if no operators available returns \forcedlink{ge_fields}(lhs, rhs).
 ///
 /// \returns true if lhs is greater or equal to rhs; false otherwise
 template <class T, class U>
@@ -168,7 +171,7 @@ constexpr detail::enable_ge_comp_t<T, U> ge(const T& lhs, const U& rhs) {
 }
 
 
-/// \brief Hashes value using its own std::hash specialization; if no std::hash specialization avalable returns \forcedlink{hash_fields}(value).
+/// \brief Hashes value using its own std::hash specialization; if no std::hash specialization available returns \forcedlink{hash_fields}(value).
 ///
 /// \returns std::size_t with hash of the value
 template <class T>
@@ -182,6 +185,10 @@ constexpr detail::enable_hashable_t<T> hash_value(const T& value) {
     return std::hash<T>{}(value);
 }
 
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_OPS_HPP

include/boost/pfr/ops_fields.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -9,6 +9,8 @@
 
 #include <boost/pfr/detail/config.hpp>
 
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #include <boost/pfr/core.hpp>
 #include <boost/pfr/detail/functional.hpp>
 
@@ -33,6 +35,8 @@
 /// \b Synopsis:
 namespace boost { namespace pfr {
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
     /// Does a field-by-field equality comparison.
     ///
     /// \returns `L == R && tuple_size_v<T> == tuple_size_v<U>`, where `L` and
@@ -122,6 +126,11 @@ namespace boost { namespace pfr {
         return result;
 #endif
     }
+
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_OPS_HPP

include/boost/pfr/traits.hpp

@@ -0,0 +1,71 @@
+// Copyright (c) 2022 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_TRAITS_HPP
+#define BOOST_PFR_TRAITS_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
+#include <boost/pfr/detail/possible_reflectable.hpp>
+
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#endif
+
+/// \file boost/pfr/traits.hpp
+/// Contains traits \forcedlink{is_reflectable} and \forcedlink{is_implicitly_reflectable} for detecting an ability to reflect type.
+///
+/// \b Synopsis:
+
+namespace boost { namespace pfr {
+
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
+/// Has a static const member variable `value` when it is known that type T can or can't be reflected using Boost.PFR; otherwise, there is no member variable.
+/// Every user may (and in some difficult cases - should) specialize is_reflectable on his own.
+///
+/// \b Example:
+/// \code
+///     namespace boost { namespace pfr {
+///         template<class All> struct is_reflectable<A, All> : std::false_type {};       // 'A' won't be interpreted as reflectable everywhere
+///         template<> struct is_reflectable<B, boost_fusion_tag> : std::false_type {};   // 'B' won't be interpreted as reflectable in only Boost Fusion
+///     }}
+/// \endcode
+/// \note is_reflectable affects is_implicitly_reflectable, the decision made by is_reflectable is used by is_implicitly_reflectable.
+template<class T, class WhatFor>
+struct is_reflectable { /*  does not have 'value' because value is unknown */ };
+
+// these specs can't be inherited from 'std::integral_constant< bool, boost::pfr::is_reflectable<T, WhatFor>::value >',
+// because it will break the sfinae-friendliness
+template<class T, class WhatFor>
+struct is_reflectable<const T, WhatFor> : boost::pfr::is_reflectable<T, WhatFor> {};
+
+template<class T, class WhatFor>
+struct is_reflectable<volatile T, WhatFor> : boost::pfr::is_reflectable<T, WhatFor> {};
+
+template<class T, class WhatFor>
+struct is_reflectable<const volatile T, WhatFor> : boost::pfr::is_reflectable<T, WhatFor> {};
+
+/// Checks the input type for the potential to be reflected.
+/// Specialize is_reflectable if you disagree with is_implicitly_reflectable's default decision.
+template<class T, class WhatFor>
+using is_implicitly_reflectable = std::integral_constant< bool, boost::pfr::detail::possible_reflectable<T, WhatFor>(1L) >;
+
+/// Checks the input type for the potential to be reflected.
+/// Specialize is_reflectable if you disagree with is_implicitly_reflectable_v's default decision.
+template<class T, class WhatFor>
+constexpr bool is_implicitly_reflectable_v = is_implicitly_reflectable<T, WhatFor>::value;
+
+BOOST_PFR_END_MODULE_EXPORT
+
+}} // namespace boost::pfr
+
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
+#endif // BOOST_PFR_TRAITS_HPP
+

include/boost/pfr/traits_fwd.hpp

@@ -0,0 +1,28 @@
+// Copyright (c) 2022 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_DETAIL_TRAITS_FWD_HPP
+#define BOOST_PFR_DETAIL_TRAITS_FWD_HPP
+#pragma once
+
+#include <boost/pfr/detail/config.hpp>
+
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
+namespace boost { namespace pfr {
+
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
+template<class T, class WhatFor>
+struct is_reflectable;
+
+BOOST_PFR_END_MODULE_EXPORT
+
+}} // namespace boost::pfr
+
+#endif  // #if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
+
+#endif // BOOST_PFR_DETAIL_TRAITS_FWD_HPP
+

include/boost/pfr/tuple_size.hpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -10,20 +10,26 @@
 
 #include <boost/pfr/detail/config.hpp>
 
-#include <type_traits>
-#include <utility>      // metaprogramming stuff
+#if !defined(BOOST_USE_MODULES) || defined(BOOST_PFR_INTERFACE_UNIT)
 
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/fields_count.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits>
+#include <utility>      // metaprogramming stuff
+#endif
+
 /// \file boost/pfr/tuple_size.hpp
 /// Contains tuple-like interfaces to get fields count \forcedlink{tuple_size}, \forcedlink{tuple_size_v}.
 ///
 /// \b Synopsis:
 namespace boost { namespace pfr {
 
+BOOST_PFR_BEGIN_MODULE_EXPORT
+
 /// Has a static const member variable `value` that contains fields count in a T.
-/// Works for any T that supports aggregate initialization.
+/// Works for any T that satisfies \aggregate.
 ///
 /// \b Example:
 /// \code
@@ -34,7 +40,7 @@ using tuple_size = detail::size_t_< boost::pfr::detail::fields_count<T>() >;
 
 
 /// `tuple_size_v` is a template variable that contains fields count in a T and
-/// works for any T that supports aggregate initialization.
+/// works for any T that satisfies \aggregate.
 ///
 /// \b Example:
 /// \code
@@ -43,6 +49,10 @@ using tuple_size = detail::size_t_< boost::pfr::detail::fields_count<T>() >;
 template <class T>
 constexpr std::size_t tuple_size_v = tuple_size<T>::value;
 
+BOOST_PFR_END_MODULE_EXPORT
+
 }} // namespace boost::pfr
 
+#endif  // #if defined(BOOST_USE_MODULES) && !defined(BOOST_PFR_INTERFACE_UNIT)
+
 #endif // BOOST_PFR_TUPLE_SIZE_HPP

index.html

@@ -1,16 +1,18 @@
 <!DOCTYPE html>
 <!--
- Copyright (c) 2014-2022 Antony Polukhin
+ Copyright (c) 2014-2026 Antony Polukhin
  antoshkka at gmail dot com
 
  Distributed under the Boost Software License,
  Version 1.0. (See accompanying file LICENSE_1_0.txt
  or copy at http://boost.org/LICENSE_1_0.txt)
+
+boost-no-inspect
 -->
 <html>
 <head>
 <meta charset="utf-8">
-<meta http-equiv="refresh" content="0; url=https://www.boost.org/doc/libs/master/doc/html/boost_pfr.html">
+<meta http-equiv="refresh" content="0; url=../../doc/html/boost_pfr.html">
 <title>Boost.Stacktrace</title>
 <style>
   body {
@@ -26,10 +28,10 @@
 <body>
   <p>
     Automatic redirection failed, please go to
-    <a href="https://www.boost.org/doc/libs/master/doc/html/boost_pfr.html">https://www.boost.org/doc/libs/master/doc/html/boost_pfr.html</a>
+    <a href="../../doc/html/boost_pfr.html">../../doc/html/boost_pfr.html</a>
   </p>
   <p>
-    &copy; 2014-2022 Antony Polukhin
+    &copy; 2014-2024 Antony Polukhin
   </p>
 </body>
 </html>

misc/generate_cpp17.py

@@ -1,6 +1,7 @@
 #!/usr/bin/python
 
-# Copyright (c) 2016-2022 Antony Polukhin
+# Copyright (c) 2016-2026 Antony Polukhin
+# Copyright (c) 2023 Denis Mikhailov
 #
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -12,8 +13,10 @@ import string
 
 # Skipping some letters that may produce keywords or are hard to read, or shadow template parameters
 ascii_letters = string.ascii_letters.replace("o", "").replace("O", "").replace("i", "").replace("I", "").replace("T", "")
+WORKAROUND_CAST_EXPRESSIONS_LIMIT_PER_LINE = 3
 
-PROLOGUE = """// Copyright (c) 2016-2020 Antony Polukhin
+PROLOGUE = """// Copyright (c) 2016-2026 Antony Polukhin
+// Copyright (c) 2023 Denis Mikhailov
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -36,6 +39,10 @@ PROLOGUE = """// Copyright (c) 2016-2020 Antony Polukhin
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/size_t_.hpp>
 
+#if !defined(BOOST_PFR_INTERFACE_UNIT)
+#include <type_traits> // for std::conditional_t, std::is_reference
+#endif
+
 namespace boost { namespace pfr { namespace detail {
 
 template <class... Args>
@@ -43,20 +50,43 @@ constexpr auto make_tuple_of_references(Args&&... args) noexcept {
   return sequence_tuple::tuple<Args&...>{ args... };
 }
 
+template<typename T, typename Arg>
+constexpr decltype(auto) add_cv_like(Arg& arg) noexcept {
+    if constexpr (std::is_const<T>::value && std::is_volatile<T>::value) {
+        return const_cast<const volatile Arg&>(arg);
+    }
+    else if constexpr (std::is_const<T>::value) {
+        return const_cast<const Arg&>(arg);
+    }
+    else if constexpr (std::is_volatile<T>::value) {
+        return const_cast<volatile Arg&>(arg);
+    }
+    else {
+        return const_cast<Arg&>(arg);
+    }
+}
+
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78939
+template<typename T, typename Sb, typename Arg>
+constexpr decltype(auto) workaround_cast(Arg& arg) noexcept {
+    using output_arg_t = std::conditional_t<!std::is_reference<Sb>(), decltype(detail::add_cv_like<T>(arg)), Sb>;
+    return const_cast<output_arg_t>(arg);
+}
+
 template <class T>
 constexpr auto tie_as_tuple(T& /*val*/, size_t_<0>) noexcept {
   return sequence_tuple::tuple<>{};
 }
 
 template <class T>
-constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<std::is_class< std::remove_cv_t<T> >::value>* = 0) noexcept {
-  auto& [a] = val; // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.
-  return ::boost::pfr::detail::make_tuple_of_references(a);
+constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<std::is_class< std::remove_cv_t<T> >::value>* = nullptr) noexcept {
+  auto& [a] = const_cast<std::remove_cv_t<T>&>(val); // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.
+  return ::boost::pfr::detail::make_tuple_of_references(detail::workaround_cast<T, decltype(a)>(a));
 }
 
 
 template <class T>
-constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<!std::is_class< std::remove_cv_t<T> >::value>* = 0) noexcept {
+constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<!std::is_class< std::remove_cv_t<T> >::value>* = nullptr) noexcept {
   return ::boost::pfr::detail::make_tuple_of_references( val );
 }
 
@@ -77,10 +107,37 @@ constexpr void tie_as_tuple(T& /*val*/, size_t_<I>) noexcept {
 
 ############################################################################################################################
 
+def fold_workaround_cast(indexes, divider):
+    WORKAROUND_CAST_TEMPLATE = """
+detail::workaround_cast<T, decltype({arg})>({arg})
+"""
+    lines = []
+    div = ''
+    tokens = [x.strip() for x in indexes.split(',')]
+    casts = [WORKAROUND_CAST_TEMPLATE.strip().format(arg=tok)
+             for tok in tokens]
+    for i in range(0, len(casts)):
+        if i%WORKAROUND_CAST_EXPRESSIONS_LIMIT_PER_LINE==0:
+            div = ''
+            lines.append('')
+        lines[-1] += div + casts[i]
+        div = ','
+    return divider.join(lines)
+
+def calc_indexes_count(indexes):
+    tokens = [x.strip() for x in indexes.split(',')]
+    return len(tokens)
+
+class EmptyLinePrinter:
+    def print_once(self):
+        if not self.printed:
+            print("")
+            self.printed = True
+    printed = False
 
 indexes = "    a"
 print(PROLOGUE)
-funcs_count = 100 if len(sys.argv) == 1 else int(sys.argv[1])
+funcs_count = 200 if len(sys.argv) == 1 else int(sys.argv[1])
 max_args_on_a_line = len(ascii_letters)
 for i in range(1, funcs_count):
     if i % max_args_on_a_line == 0:
@@ -92,18 +149,26 @@ for i in range(1, funcs_count):
         indexes += ascii_letters[i // max_args_on_a_line - 1]
     indexes += ascii_letters[i % max_args_on_a_line]
 
+    printed_casts = fold_workaround_cast(indexes.strip(), ",\n    ")
+    indexes_count = calc_indexes_count(indexes.strip())
+    empty_printer = EmptyLinePrinter()
+
     print("template <class T>")
     print("constexpr auto tie_as_tuple(T& val, size_t_<" + str(i + 1) + ">) noexcept {")
     if i < max_args_on_a_line:
-        print("  auto& [" + indexes.strip() + "] = val; // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.")
-        print("  return ::boost::pfr::detail::make_tuple_of_references(" + indexes.strip() + ");")
+        print("  auto& [" + indexes.strip() + "] = const_cast<std::remove_cv_t<T>&>(val); // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.")
     else:
         print("  auto& [")
         print(indexes)
-        print("  ] = val; // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.")
-        print("")
+        print("  ] = const_cast<std::remove_cv_t<T>&>(val); // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.")
+        empty_printer.print_once()
+ 
+    if indexes_count < WORKAROUND_CAST_EXPRESSIONS_LIMIT_PER_LINE:
+        print("  return ::boost::pfr::detail::make_tuple_of_references(" + printed_casts + ");")
+    else:
+        empty_printer.print_once()
         print("  return ::boost::pfr::detail::make_tuple_of_references(")
-        print(indexes)
+        print("    " + printed_casts)
         print("  );")
 
     print("}\n")

misc/generate_fields_names_big.cpp.py

@@ -0,0 +1,267 @@
+# Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+#
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+# Initial implementation by Bela Schaum, https://github.com/schaumb
+# The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+#
+
+############################################################################################################################
+
+import sys
+import string
+import random
+
+# a bigger value might lead to compiler out of heap space error on MSVC
+STRUCT_COUNT = 50
+MAX_FIELD_COUNT = 50
+
+MAIN_TEMPLATE = """// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov, Antony Polukhin.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// Generated by misc/generate_fields_names_big.cpp.py
+
+#include <boost/pfr/core_name.hpp>
+#include <type_traits>
+
+#include <boost/core/lightweight_test.hpp>
+
+namespace testing {
+
+template <class... Types>
+auto make_stdarray(const Types&... t) {
+    return std::array<std::common_type_t<Types...>, sizeof...(Types)>{t...};
+}
+
+%STRUCTS_LIST%
+
+%TEST_GET_NAME_DEFINITIONS_LIST%
+
+%TEST_GET_NAMES_AS_ARRAY_DEFINITIONS_LIST%
+
+
+} // namespace testing
+
+int main() {
+    %TEST_GET_NAME_CALLS_LIST%
+    %TEST_GET_NAMES_AS_ARRAY_CALLS_LIST%
+
+    return boost::report_errors();
+}
+"""
+
+STRUCT_TEMPLATE = """struct Aggregate%STRUCT_ID% {
+    %FIELD_DEFINITIONS_LIST%
+};
+"""
+
+STRUCT_FIELD_DEFINITION_TEMPLATE = """int %FIELD_NAME%;
+"""
+
+TEST_GET_NAME_TEMPLATE = """void test_get_name_%TEST_ID%() {
+    %CHECKERS_LIST%
+}
+"""
+
+TEST_GET_NAME_CHECKER_TEMPLATE = """BOOST_TEST_EQ( ((boost::pfr::get_name<%FIELD_ID%, Aggregate%STRUCT_ID%>())), "%FIELD_NAME%");
+"""
+
+TEST_GET_NAMES_AS_ARRAY_TEMPLATE = """void test_names_as_array_%TEST_ID%() {
+    const auto expected = make_stdarray(
+        %FIELD_NAMES_LIST%
+    );
+    const auto value = boost::pfr::names_as_array<Aggregate%STRUCT_ID%>();
+    BOOST_TEST_EQ(expected.size(), value.size());
+    for (std::size_t i=0;i<expected.size();++i) {
+        BOOST_TEST_EQ(value[i], expected[i]);
+    }
+}
+"""
+
+FIELD_NAME_TEMPLATE = """std::string_view{"%FIELD_NAME%"}
+"""
+
+TEST_GET_NAME_CALL_TEMPLATE = """testing::test_get_name_%TEST_ID%();
+"""
+
+TEST_GET_NAMES_AS_ARRAY_CALL_TEMPLATE = """testing::test_names_as_array_%TEST_ID%();
+"""
+
+############################################################################################################################
+
+field_names = {
+    "alignas": True,
+    "alignof": True,
+    "and": True,
+    "and_eq": True,
+    "asm": True,
+    "atomic_cancel": True,
+    "atomic_commit": True,
+    "atomic_noexcept": True,
+    "auto": True,
+    "bitand": True,
+    "bitor": True,
+    "bool": True,
+    "break": True,
+    "case": True,
+    "catch": True,
+    "char": True,
+    "char8_t": True,
+    "char16_t": True,
+    "char32_t": True,
+    "class": True,
+    "compl": True,
+    "concept": True,
+    "const": True,
+    "consteval": True,
+    "constexpr": True,
+    "constinit": True,
+    "const_cast": True,
+    "continue": True,
+    "co_await": True,
+    "co_return": True,
+    "co_yield": True,
+    "decltype": True,
+    "default": True,
+    "delete": True,
+    "do": True,
+    "double": True,
+    "dynamic_cast": True,
+    "else": True,
+    "enum": True,
+    "explicit": True,
+    "export": True,
+    "extern": True,
+    "false": True,
+    "float": True,
+    "for": True,
+    "friend": True,
+    "goto": True,
+    "if": True,
+    "inline": True,
+    "int": True,
+    "long": True,
+    "mutable": True,
+    "namespace": True,
+    "new": True,
+    "noexcept": True,
+    "not": True,
+    "not_eq": True,
+    "nullptr": True,
+    "operator": True,
+    "or": True,
+    "or_eq": True,
+    "private": True,
+    "protected": True,
+    "public": True,
+    "reflexpr": True,
+    "register": True,
+    "reinterpret_cast": True,
+    "requires": True,
+    "return": True,
+    "short": True,
+    "signed": True,
+    "sizeof": True,
+    "static": True,
+    "static_assert": True,
+    "static_cast": True,
+    "struct": True,
+    "switch": True,
+    "synchronized": True,
+    "template": True,
+    "this": True,
+    "thread_local": True,
+    "throw": True,
+    "true": True,
+    "try": True,
+    "typedef": True,
+    "typeid": True,
+    "typename": True,
+    "union": True,
+    "unsigned": True,
+    "using": True,
+    "virtual": True,
+    "void": True,
+    "volatile": True,
+    "wchar_t": True,
+    "while": True,
+    "xor": True,
+    "xor_eq": True
+}
+field_names_by_id = {}
+
+def generate_new_field_name():
+    result = ''
+    name_len = random.randint(1,100)
+    result += random.choice("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_")
+    for i in range(name_len-1):
+        result += random.choice("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789")
+    return result
+
+def generate_field_name(struct_id, field_id):
+    key = (struct_id, field_id)
+    if not key in field_names_by_id:
+        new_name = generate_new_field_name()
+        while new_name in field_names:
+            new_name = generate_new_field_name()
+        field_names[new_name] = True
+        field_names_by_id[key] = new_name
+    return field_names_by_id[key]
+
+def generate_struct(struct_id):
+    field_definitions = ''
+    fields_count = struct_id
+    for i in range(fields_count):
+        field_definitions += STRUCT_FIELD_DEFINITION_TEMPLATE.replace('%FIELD_NAME%', generate_field_name(struct_id, i))
+    return STRUCT_TEMPLATE.replace('%FIELD_DEFINITIONS_LIST%', field_definitions).replace('%STRUCT_ID%', str(struct_id))
+
+def generate_structs_list():
+    result = ''
+    for i in range(STRUCT_COUNT):
+        result += generate_struct(i+1)
+    return result
+
+def generate_test_get_name_definition(struct_id):
+    checkers_list = ''
+    fields_count = struct_id
+    for i in range(fields_count):
+        checkers_list += TEST_GET_NAME_CHECKER_TEMPLATE.replace('%FIELD_ID%', str(i)).replace('%STRUCT_ID%', str(struct_id)).replace('%FIELD_NAME%', generate_field_name(struct_id, i))
+    return TEST_GET_NAME_TEMPLATE.replace('%TEST_ID%', str(struct_id)).replace('%CHECKERS_LIST%', checkers_list)
+
+def generate_test_get_name_definitions_list():
+    result = ''
+    for i in range(STRUCT_COUNT):
+        result += generate_test_get_name_definition(i+1)
+    return result
+
+def generate_test_names_as_array_definition(struct_id):
+    field_names_list = FIELD_NAME_TEMPLATE.replace('%FIELD_NAME%', generate_field_name(struct_id, 0))
+    fields_count = struct_id
+    for i in range(1, fields_count):
+        field_names_list += ', ' + FIELD_NAME_TEMPLATE.replace('%FIELD_NAME%', generate_field_name(struct_id, i))
+    return TEST_GET_NAMES_AS_ARRAY_TEMPLATE.replace('%TEST_ID%', str(struct_id)).replace('%FIELD_NAMES_LIST%', field_names_list).replace('%STRUCT_ID%', str(struct_id))
+
+def generate_test_names_as_array_definitions_list():
+    result = ''
+    for i in range(STRUCT_COUNT):
+        result += generate_test_names_as_array_definition(i+1)
+    return result
+
+def generate_test_get_name_calls_list():
+    result = ''
+    for i in range(STRUCT_COUNT):
+        result += TEST_GET_NAME_CALL_TEMPLATE.replace('%TEST_ID%', str(i+1))
+    return result
+
+def generate_test_names_as_array_calls_list():
+    result = ''
+    for i in range(STRUCT_COUNT):
+        result += TEST_GET_NAMES_AS_ARRAY_CALL_TEMPLATE.replace('%TEST_ID%', str(i+1))
+    return result
+
+print(MAIN_TEMPLATE.replace('%STRUCTS_LIST%', generate_structs_list()).replace('%TEST_GET_NAME_DEFINITIONS_LIST%', generate_test_get_name_definitions_list()).replace('%TEST_GET_NAMES_AS_ARRAY_DEFINITIONS_LIST%', generate_test_names_as_array_definitions_list()).replace('%TEST_GET_NAME_CALLS_LIST%', generate_test_get_name_calls_list()).replace('%TEST_GET_NAMES_AS_ARRAY_CALLS_LIST%', generate_test_names_as_array_calls_list()))
+

misc/strip_boost_namespace.sh

@@ -1,10 +1,12 @@
 #!/bin/bash
 
-# Copyright (c) 2021 Antony Polukhin
+# Copyright (c) 2021-2026 Antony Polukhin
 #
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
+PFR_TEST_COMPILER=clang++-19
+
 echo "***** Making target path"
 TARGET_PATH="`dirname \"$0\"`/../../pfr_non_boost"
 rm -rf ${TARGET_PATH}/*
@@ -24,41 +26,83 @@ rm ${TARGET_PATH}/misc/strip_boost_namespace.sh
 rm -rf ${TARGET_PATH}/meta
 
 echo "***** Changing sources"
-find ${TARGET_PATH} -type f | xargs sed -i 's|namespace boost { ||g'
-find ${TARGET_PATH} -type f | xargs sed -i 's|namespace boost {||g'
-find ${TARGET_PATH} -type f | xargs sed -i 's|} // namespace boost::| // namespace |g'
+find ${TARGET_PATH} -type f | xargs sed -i \
+        -e 's|namespace boost { ||g' \
+        -e 's|namespace boost {||g' \
+        -e 's|} // namespace boost::| // namespace |g' \
+        \
+        -e 's/::boost::pfr/::pfr/g' \
+        -e 's/boost::pfr/pfr/g' \
+        -e 's/BOOST_PFR_/PFR_/g' \
+        -e 's|boost/pfr|pfr|g' \
+        \
+        -e 's/boost_pfr /pfr /g' \
+        -e 's/boost_pfr_/pfr_/g' \
+        -e 's/boost_pfr)/pfr)/g' \
+        -e 's/Boost::pfr/pfr::pfr/g' \
+        -e 's/BOOST_USE_MODULES/PFR_USE_MODULES/g' \
+        -e 's|boost\.pfr;|pfr;|g' \
 
-find ${TARGET_PATH} -type f | xargs sed -i 's/::boost::pfr/::pfr/g'
-find ${TARGET_PATH} -type f | xargs sed -i 's/boost::pfr/pfr/g'
-find ${TARGET_PATH} -type f | xargs sed -i 's/BOOST_PFR_/PFR_/g'
-find ${TARGET_PATH} -type f | xargs sed -i 's|boost/pfr|pfr|g'
-
-find ${TARGET_PATH}/doc -type f | xargs sed -i 's|boost.pfr.|pfr.|g'
-find ${TARGET_PATH}/doc -type f | xargs sed -i 's|Boost.PFR|PFR|g'
+find ${TARGET_PATH}/doc -type f | xargs sed -i \
+        -e 's|boost\.pfr\.|pfr.|g' \
+        -e 's|boost\.pfr`|pfr`|g' \
+        -e 's/boost_pfr\./pfr./g' \
+        -e 's|Boost\.PFR|PFR|g' \
 
 sed -i  's|# \[Boost.PFR\](https://boost.org/libs/pfr)|# [PFR](https://apolukhin.github.io/pfr_non_boost/)|g' ${TARGET_PATH}/README.md
 
 echo -n "***** Testing: "
-if g++-9 -std=c++17 -DPFR_USE_LOOPHOLE=0 -DPFR_USE_CPP17=1 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/motivating_example0.cpp && ./a.out > /dev/null; then
+if ${PFR_TEST_COMPILER} -std=c++2a -DPFR_ENABLE_GET_NAME_STATIC=1 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/motivating_example0.cpp && ./a.out > /dev/null; then
     echo -n "OK"
 else
     echo -n "FAIL"
     exit 2
 fi
-if g++-9 -std=c++17 -DPFR_USE_LOOPHOLE=1 -DPFR_USE_CPP17=0 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/motivating_example0.cpp && ./a.out > /dev/null; then
+if ${PFR_TEST_COMPILER} -std=c++2a -DPFR_ENABLE_GET_NAME_STATIC=0 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/motivating_example0.cpp && ./a.out > /dev/null; then
     echo -n ", OK"
 else
     echo -n ", FAIL"
     exit 3
 fi
 
-if g++-9 -std=c++17 -DPFR_USE_LOOPHOLE=0 -DPFR_USE_CPP17=0 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/get.cpp && ./a.out > /dev/null; then
-    echo -e ", OK"
+if ${PFR_TEST_COMPILER} -std=c++2a -DPFR_ENABLE_GET_NAME_STATIC=1 -DBOOST_PFR_USE_CPP17=1 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/get_name.cpp && ./a.out > /dev/null; then
+    echo -n ", OK"
 else
-    echo -e ", FAIL"
+    echo -n ", FAIL"
     exit 4
 fi
 
+if ${PFR_TEST_COMPILER} -std=c++2a -DPFR_USE_LOOPHOLE=0 -DPFR_USE_CPP17=1 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/motivating_example0.cpp && ./a.out > /dev/null; then
+    echo -n ", OK"
+else
+    echo -n ", FAIL"
+    exit 5
+fi
+if ${PFR_TEST_COMPILER} -std=c++2a -DPFR_USE_LOOPHOLE=1 -DPFR_USE_CPP17=0 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/motivating_example0.cpp && ./a.out > /dev/null; then
+    echo -n ", OK"
+else
+    echo -n ", FAIL"
+    exit 6
+fi
+
+if ${PFR_TEST_COMPILER} -std=c++2a -DPFR_USE_LOOPHOLE=0 -DPFR_USE_CPP17=0 -I ${TARGET_PATH}/include/ ${TARGET_PATH}/example/get.cpp && ./a.out > /dev/null; then
+    echo -n ", OK"
+else
+    echo -n ", FAIL"
+    exit 7
+fi
+
+mkdir build_module || :
+cd build_module
+if cmake -DPFR_USE_MODULES=1 -DBUILD_TESTING=1 -GNinja -DCMAKE_CXX_COMPILER=${PFR_TEST_COMPILER} ${TARGET_PATH} && cmake --build .; then
+    echo "Modules check OK"
+else
+    echo "Modules check FAIL"
+    exit 8
+fi
+cd ..
+
+rm -rf build_module || :
 rm a.out || :
 
-echo "***** Done"
+echo -e "\n***** Done"

modules/boost_pfr.cppm

@@ -0,0 +1,42 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// To compile manually use a command like the folowing:
+// clang++ -I ../include -std=c++20 --precompile -x c++-module pfr.cppm
+
+module;
+
+#include <version>
+#include <cstddef>
+#include <cstdint>
+
+#ifdef BOOST_PFR_USE_STD_MODULE
+import std;
+#else
+#include <array>
+#include <cstddef>
+#include <functional>
+#include <iomanip>
+#include <iostream>
+#include <limits>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <variant>
+#endif
+
+#define BOOST_PFR_INTERFACE_UNIT
+
+export module boost.pfr;
+
+#ifdef __clang__
+#   pragma clang diagnostic ignored "-Winclude-angled-in-module-purview"
+#endif
+
+#include <boost/pfr.hpp>
+

modules/usage_sample.cpp

@@ -0,0 +1,31 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// To compile manually use a command like the folowing:
+// clang++ -std=c++20 -fmodule-file=pfr.pcm pfr.pcm usage_sample.cpp
+
+//[pfr_module_example
+#include <iostream>
+#include <iomanip>
+#include <string>
+
+import boost.pfr;
+
+struct some_person {
+    std::string name;
+    unsigned birth_year;
+};
+
+int main() {
+    some_person val{"Edgar Allan Poe", 1809};
+
+    std::cout << boost::pfr::get<0>(val)                // No macro!
+        << " was born in " << boost::pfr::get<1>(val);  // Works with any aggregate!
+
+    std::cout << '\n' << boost::pfr::io(val);           // Outputs: {"Edgar Allan Poe", 1809}
+    std::cout << "\n." << boost::pfr::get_name<0, some_person>()
+        << '=' << val.name << '\n';                     // Outputs: .name=Edgar Allan Poe
+}
+//]

modules/usage_test_mu1.cpp

@@ -0,0 +1,27 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// To compile manually use a command like the folowing:
+// clang++ -std=c++20 -fmodule-file=pfr.pcm pfr.pcm usage_sample.cpp
+
+#include <iostream>
+
+#include <boost/pfr.hpp>
+
+struct some_person {
+    std::string name;
+    unsigned birth_year;
+};
+
+void mu1_act() {
+    some_person val{"Edgar Allan Poe", 1809};
+
+    std::cout << boost::pfr::get<0>(val)                // No macro!
+        << " was born in " << boost::pfr::get<1>(val);  // Works with any aggregate!
+
+    std::cout << '\n' << boost::pfr::io(val);           // Outputs: {"Edgar Allan Poe", 1809}
+    std::cout << "\n." << boost::pfr::get_name<0, some_person>()
+        << '=' << val.name << '\n';                     // Outputs: .name=Edgar Allan Poe
+}

modules/usage_test_mu2.cpp

@@ -0,0 +1,32 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// To compile manually use a command like the folowing:
+// clang++ -std=c++20 -fmodule-file=pfr.pcm pfr.pcm usage_sample.cpp
+
+#include <iostream>
+#include <iomanip>
+
+import boost.pfr;
+
+struct some_person {
+    std::string name;
+    unsigned birth_year;
+};
+
+void mu1_act();
+
+int main() {
+    mu1_act();
+
+    some_person val{"Joseph Brodsky", 1940};
+
+    std::cout << boost::pfr::get<0>(val)                // No macro!
+        << " was born in " << boost::pfr::get<1>(val);  // Works with any aggregate!
+
+    std::cout << '\n' << boost::pfr::io(val);
+    std::cout << "\n." << boost::pfr::get_name<0, some_person>()
+        << '=' << val.name << '\n';
+}

test/CMakeLists.txt

@@ -0,0 +1,32 @@
+# Copyright  (c) 2016-2026 Antony Polukhin
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
+
+if(NOT TARGET tests)
+  add_custom_target(tests)
+endif()
+
+file(GLOB CORE_RUN_FILES "core/run/*.cpp")
+foreach (testsourcefile ${CORE_RUN_FILES})
+    get_filename_component(testname ${testsourcefile} NAME_WE)
+    add_executable(pfr_core_${testname} ${testsourcefile})
+    target_link_libraries(pfr_core_${testname} Boost::pfr Boost::core Boost::container_hash)
+    target_include_directories(pfr_core_${testname} PRIVATE ../../../)
+    add_test(NAME pfr_core_${testname} COMMAND pfr_core_${testname})
+    add_dependencies(tests pfr_core_${testname})
+endforeach()
+
+if(CMAKE_VERSION VERSION_LESS 3.12)
+    message(AUTHOR_WARNING "Disabling core_name tests as CMake version 3.12+ is required but using ${CMAKE_VERSION}")
+else()
+    file(GLOB CORE_NAME_RUN_FILES "core_name/run/*.cpp")
+    foreach (testsourcefile ${CORE_NAME_RUN_FILES})
+        get_filename_component(testname ${testsourcefile} NAME_WE)
+        add_executable(pfr_corename_${testname} ${testsourcefile})
+        target_compile_features(pfr_corename_${testname} PUBLIC cxx_std_20)
+        target_link_libraries(pfr_corename_${testname} Boost::pfr Boost::core Boost::container_hash)
+        target_include_directories(pfr_corename_${testname} PRIVATE ../../../)
+        add_test(NAME pfr_corename_${testname} COMMAND pfr_corename_${testname})
+        add_dependencies(tests pfr_corename_${testname})
+    endforeach()
+endif()

test/Jamfile

@@ -0,0 +1,10 @@
+#  Copyright (C) 2023 Denis Mikhailov
+#
+# Use, modification and distribution is subject to the Boost Software License,
+# Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+#
+
+build-project config ;
+build-project core ;
+build-project core_name ;

test/appveyor.yml

@@ -32,21 +32,25 @@ skip_tags: true
 
 environment:
   matrix:
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      TOOLSET: msvc-9.0
+      ADDRMD: 32
+      CXXSTD: latest # fake
 #    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
 #      TOOLSET: msvc # TODO: clang-win ???
 #      ADDRMD: 32,64
 #      CXXSTD: 17,latest
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: msvc # clang-win has problems with structured bindings - it can not correclty use std::tuple_size
+      TOOLSET: msvc # clang-win has problems with structured bindings - it can not correctly use std::tuple_size
       ADDRMD: 32,64
       CXXSTD: 17,latest
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: msvc # clang-win has problems with structured bindings - it can not correclty use std::tuple_size
+      TOOLSET: msvc # clang-win has problems with structured bindings - it can not correctly use std::tuple_size
       ADDRMD: 32,64
       CXXSTD: 17,latest
       CXXFLAGS: /permissive-
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: msvc # clang-win has problems with structured bindings - it can not correclty use std::tuple_size
+      TOOLSET: msvc # clang-win has problems with structured bindings - it can not correctly use std::tuple_size
       ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       ADDPATH: C:\cygwin\bin;

test/cmake_subdir_test/CMakeLists.txt

@@ -0,0 +1,21 @@
+# Copyright  (c) 2016-2026 Antony Polukhin
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
+
+cmake_minimum_required(VERSION 3.5...4.0)
+
+project(pfr_subdir_test LANGUAGES CXX)
+
+add_subdirectory(../../../assert boostorg/assert)
+add_subdirectory(../../../container_hash boostorg/container_hash)
+add_subdirectory(../../../core boostorg/core)
+add_subdirectory(../../../config boostorg/config)
+add_subdirectory(../../../detail boostorg/detail)
+add_subdirectory(../../../describe boostorg/describe)
+add_subdirectory(../../../integer boostorg/integer)
+add_subdirectory(../../../mp11 boostorg/mp11)
+add_subdirectory(../../../static_assert boostorg/static_assert)
+add_subdirectory(../../../throw_exception boostorg/throw_exception)
+add_subdirectory(../../../type_traits boostorg/type_traits)
+
+add_subdirectory(../../ boostorg/pfr)

test/config/Jamfile.v2

@@ -0,0 +1,26 @@
+#  Copyright (C) 2023 Denis Mikhailov
+#
+# Use, modification and distribution is subject to the Boost Software License,
+# Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+#
+
+import-search /boost/config/checks ;
+
+import python ;
+import testing ;
+import config : requires ;
+
+project
+    : source-location .
+    : requirements
+        <library>/boost/config//boost_config
+        <library>/boost/preprocessor//boost_preprocessor
+        <define>BOOST_PFR_DETAIL_STRICT_RVALUE_TESTING=1
+    ;
+
+
+test-suite pfr_tests
+  :
+    [ run print_config.cpp : : : <test-info>always_show_run_output : auto_engine_config ]
+  ;

test/config/print_config.cpp

@@ -1,18 +1,28 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-#include <boost/pfr/core.hpp>
+#include <boost/pfr/config.hpp>
+#if BOOST_PFR_ENABLED
+#include <boost/pfr.hpp>
+#endif
+#include <boost/preprocessor/stringize.hpp>
 
 #include <iostream>
 
 int main() {
     std::cout << "Platform info:" << '\n'
         << "BOOST_PFR_USE_CPP17 == " << BOOST_PFR_USE_CPP17 << '\n'
+        << "BOOST_PFR_USE_CPP26 == " << BOOST_PFR_USE_CPP26 << '\n'
         << "BOOST_PFR_USE_LOOPHOLE == " << BOOST_PFR_USE_LOOPHOLE << '\n'
         << "BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE == " << BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE << '\n'
         << "BOOST_PFR_HAS_GUARANTEED_COPY_ELISION == " << BOOST_PFR_HAS_GUARANTEED_COPY_ELISION << '\n'
+        << "BOOST_PFR_ENABLE_IMPLICIT_REFLECTION == " << BOOST_PFR_ENABLE_IMPLICIT_REFLECTION << '\n'
+        << "BOOST_PFR_CORE_NAME_ENABLED == " << BOOST_PFR_CORE_NAME_ENABLED << '\n'
+        << "BOOST_PFR_FUNCTION_SIGNATURE == " << BOOST_PP_STRINGIZE(BOOST_PFR_FUNCTION_SIGNATURE) << '\n'
+        << "BOOST_PFR_CORE_NAME_PARSING == " << BOOST_PP_STRINGIZE(BOOST_PFR_CORE_NAME_PARSING) << '\n'
+        << "BOOST_PFR_ENABLED == " << BOOST_PFR_ENABLED << '\n'
         << "__cplusplus == " << __cplusplus << '\n'
 #ifdef __cpp_structured_bindings
         << "__cpp_structured_bindings == " << __cpp_structured_bindings << '\n'

test/core/Jamfile.v2

@@ -1,22 +1,29 @@
-#  Copyright (C) 2016-2022 Antony Polukhin.
+#  Copyright (C) 2016-2026 Antony Polukhin.
 #
 # Use, modification and distribution is subject to the Boost Software License,
 # Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 # http://www.boost.org/LICENSE_1_0.txt)
 #
 
+import-search /boost/config/checks ;
+
 import python ;
 import testing ;
-import ../../config/checks/config : requires ;
+import config : requires ;
 
 project
     : source-location .
     : requirements
+        <library>/boost/config//boost_config
+        <library>/boost/core//boost_core
+        <library>/boost/container_hash//boost_container_hash
+        <library>/boost/type_index//boost_type_index
+
         <define>BOOST_PFR_DETAIL_STRICT_RVALUE_TESTING=1
         [ requires cxx14_constexpr ]
     ;
 
-########## BEGIN of helpers to detect Loophole trick support
+########## BEGIN of helpers to detect Loophole and variadic structured binding support
 
 actions mp_simple_run_action
 {
@@ -35,24 +42,31 @@ rule mp-run-simple ( sources + : args * : input-files * : requirements * : targe
 mp-run-simple loophole_detection.cpp : : : : compiler_supports_loophole ;
 explicit compiler_supports_loophole ;
 
+mp-run-simple variadic_structured_binding_detection.cpp : : : : compiler_supports_vsb ;
+explicit compiler_supports_vsb ;
+
 ########## END of helpers to detect Loophole trick support
 
 
 local DISABLE_ON_MSVC = ; #<toolset>msvc:<build>no ;
 local REQUIRE_LOOPHOLE =
-    [ check-target-builds ../test//compiler_supports_loophole : : <build>no ]
+    [ check-target-builds ../core//compiler_supports_loophole : : <build>no ]
+  ;
+local REQUIRE_VSB =
+    [ check-target-builds ../core//compiler_supports_vsb : : <build>no ]
   ;
 
-local STRUCTURED_BINDING_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=0 <define>BOOST_PFR_USE_CPP17=1 [ requires cxx17_structured_bindings ] ;
-local LOOPHOLE_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=1 <define>BOOST_PFR_USE_CPP17=0 $(REQUIRE_LOOPHOLE) ;
-local CLASSIC_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=0 <define>BOOST_PFR_USE_CPP17=0 $(DISABLE_ON_MSVC) ;
+local VARIADIC_STRUCTURED_BINDING_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=0 <define>BOOST_PFR_USE_CPP17=0 <define>BOOST_PFR_USE_CPP26=1 $(REQUIRE_VSB) ;
+local STRUCTURED_BINDING_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=0 <define>BOOST_PFR_USE_CPP17=1 <define>BOOST_PFR_USE_CPP26=0 [ requires cxx17_structured_bindings ] ;
+local LOOPHOLE_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=1 <define>BOOST_PFR_USE_CPP17=0 <define>BOOST_PFR_USE_CPP26=0 $(REQUIRE_LOOPHOLE) ;
+local CLASSIC_ENGINE = <define>BOOST_PFR_USE_LOOPHOLE=0 <define>BOOST_PFR_USE_CPP17=0 <define>BOOST_PFR_USE_CPP26=0 $(DISABLE_ON_MSVC) ;
 
 test-suite pfr_tests
   :
-    [ run print_config.cpp : : : <test-info>always_show_run_output : auto_engine_config ]
-
     [ run offset_based_getter.cpp ]
 
+    [ run can_be_as_fallback_in_the_fusion.cpp ]
+
     [ run test_tuple_sizes_on.cpp : : : <define>BOOST_PFR_RUN_TEST_ON=char : test_tuple_sizes_on_chars ]
     [ run test_tuple_sizes_on.cpp : : : <define>BOOST_PFR_RUN_TEST_ON=int : test_tuple_sizes_on_ints ]
     [ run test_tuple_sizes_on.cpp : : : <define>BOOST_PFR_RUN_TEST_ON=short : test_tuple_sizes_on_shorts ]
@@ -60,9 +74,13 @@ test-suite pfr_tests
     [ run test_tuple_sizes_on.cpp : : : <define>BOOST_PFR_RUN_TEST_ON="std::size_t" : test_tuple_sizes_on_size_ts ]
 
     [ run run/motivating_example.cpp      : : : : auto_engine_motivating ]
-    [ run ../example/sample_printing.cpp  : : : : auto_engine_sample_printing ]
-    [ run ../example/get.cpp              : : : : auto_engine_get ]
-    [ run ../example/quick_examples.cpp   : : : : auto_engine_quick ]
+    [ run ../../example/sample_printing.cpp  : : : : auto_engine_sample_printing ]
+    [ run ../../example/get.cpp              : : : : auto_engine_get ]
+    [ run ../../example/quick_examples.cpp   : : : : auto_engine_quick ]
+
+    [ compile-fail fields_count_on_incomplete_type.cpp : <define>BOOST_PFR_RUN_TEST_ON=void : fields_count_on_incomplete_type_void ]
+    [ compile-fail fields_count_on_incomplete_type.cpp : <define>BOOST_PFR_RUN_TEST_ON="void()" : fields_count_on_incomplete_type_function ]
+    [ compile-fail fields_count_on_incomplete_type.cpp : <define>BOOST_PFR_RUN_TEST_ON="struct Foo" : fields_count_on_incomplete_type_struct ]
   ;
 
 local BLACKLIST_TESTS_FOR_LOOPHOLE =
@@ -73,7 +91,7 @@ local BLACKLIST_TESTS_FOR_LOOPHOLE =
     tie_anonymous_const_field           # boost::pfr::structure_tie gives compile time error on const fields
   ;
 
-# Those tests are either 
+# Those tests are either
 # * reflecting a non literal type
 # * or calling boost::pfr::get and the result is a user defined structure
 local BLACKLIST_TESTS_FOR_CLASSIC =
@@ -95,11 +113,12 @@ local BLACKLIST_TESTS_FOR_CLASSIC =
     tie_anonymous_const_field
   ;
 
-for local source_file in [ glob ./run/*.cpp ] [ glob ../example/*.cpp ]
+for local source_file in [ glob ./run/*.cpp ] [ glob ../../example/*.cpp ]
 {
     local target_name = $(source_file[1]:B) ;
+    pfr_tests += [ run $(source_file) : : : $(VARIADIC_STRUCTURED_BINDING_ENGINE) : $(target_name)_vsb ] ;
     pfr_tests += [ run $(source_file) : : : $(STRUCTURED_BINDING_ENGINE) : $(target_name)_sb ] ;
-    
+
     if ! $(target_name) in $(BLACKLIST_TESTS_FOR_LOOPHOLE)
     {
         pfr_tests += [ run $(source_file) : : : $(LOOPHOLE_ENGINE) : $(target_name)_lh ] ;
@@ -129,5 +148,5 @@ for local source_file in [ glob ./compile-fail/*.cpp ]
 
 if [ python.configured ]
 {
-    testing.make-test run-pyd : ../misc/generate_cpp17.py ;
+    testing.make-test run-pyd : ../../misc/generate_cpp17.py ;
 }

test/core/can_be_as_fallback_in_the_fusion.cpp

@@ -0,0 +1,37 @@
+// Copyright (c) 2022 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <type_traits>
+
+struct Aggregate {};
+using NonAggregate = int;
+
+template<class T>
+struct is_implicitly_reflectable : std::false_type
+{};
+
+template<>
+struct is_implicitly_reflectable<Aggregate> : std::true_type
+{};
+
+template<class T, class E=void>
+struct tag_of_fallback {
+    using type = int; // unknown
+};
+
+template<class T>
+struct tag_of_fallback<T, std::enable_if_t<std::is_same<T,T>::value>>
+{
+    using type = std::conditional_t<
+        is_implicitly_reflectable<T>::value
+      , std::true_type
+      , std::false_type
+    >;
+};
+
+static_assert(tag_of_fallback<Aggregate>::type::value == true, "");
+static_assert(tag_of_fallback<NonAggregate>::type::value == false, "");
+
+int main() { }

test/core/compile-fail/boost_pfr_disabled_via_macro.cpp

@@ -0,0 +1,10 @@
+// Copyright (c) 2022 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#define BOOST_PFR_ENABLED 0
+#include <boost/pfr/core.hpp>
+
+int main() { }
+

test/core/compile-fail/constructible_0_or_more_args.cpp

@@ -0,0 +1,15 @@
+// Copyright (c) 2023-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/pfr/tuple_size.hpp>
+
+struct A {
+    template <typename... Args>
+    explicit A(Args&&...) {}
+};
+
+int main() {
+    (void)boost::pfr::tuple_size<A>::value; // Must be a compile time error
+}

test/core/compile-fail/constructible_1_or_more_args.cpp

@@ -0,0 +1,15 @@
+// Copyright (c) 2023-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/pfr/tuple_size.hpp>
+
+struct A {
+    template <typename Arg0, typename... Args>
+    explicit A(Arg0&&, Args&&...) {}
+};
+
+int main() {
+    (void)boost::pfr::tuple_size<A>::value; // Must be a compile time error
+}

test/core/compile-fail/fields_count_on_reference.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/inherited.cpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2021 Denis Mikhailov
-// Copyright (c) 2021 Antony Polukhin
+// Copyright (c) 2021-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/inherited_nonempty.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2021 Antony Polukhin
+// Copyright (c) 2021-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/movable_and_lvalue_references.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/non_aggregate.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/ops_on_union.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/ops_unions.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/ops_unrestricted_unions.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/pfr_review_test2.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2020-2022 Antony Polukhin
+// Copyright (c) 2020-2026 Antony Polukhin
 // Copyright (c) 2020 Richard Hodges
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying

test/core/compile-fail/private_fields.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/protected_fields.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/rvalue_tie.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2020-2022 Antony Polukhin
+// Copyright (c) 2020-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/compile-fail/virtual_functions.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/fields_count_immutable.cpp

@@ -0,0 +1,37 @@
+// Copyright (c) 2025-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// Test from https://github.com/boostorg/pfr/issues/126
+
+#include <boost/pfr.hpp>
+
+struct NoCopy {
+    NoCopy() = default;
+    NoCopy(NoCopy const&) = delete;
+    NoCopy(NoCopy&&) = delete;
+    NoCopy& operator=(NoCopy&&) = delete;
+    NoCopy& operator=(NoCopy const&) = delete;
+};
+
+struct Group {
+    NoCopy m;
+    NoCopy m2;
+    NoCopy m3;
+    NoCopy m4;
+};
+
+Group ReturnGroup() { return {};}
+
+int main()
+{   
+#ifdef __cpp_lib_is_aggregate
+    static_assert(std::is_aggregate_v<Group>, "Group is totally an aggregate");
+#endif
+    static_assert(BOOST_PFR_HAS_GUARANTEED_COPY_ELISION, "Compiler implements mandatory copy elision");
+    Group aggregate_init_test{{}, {}, {}, {}};
+    Group elision_test = ReturnGroup();
+    return  boost::pfr::tuple_size_v<Group>;
+}
+

test/core/fields_count_on_incomplete_type.cpp

@@ -0,0 +1,10 @@
+// Copyright (c) 2023-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/pfr/detail/fields_count.hpp>
+
+int main() {
+    return static_cast<int>(boost::pfr::detail::fields_count<BOOST_PFR_RUN_TEST_ON>());
+}

test/core/loophole_detection.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2020-2022 Antony Polukhin
+// Copyright (c) 2020-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/offset_based_getter.cpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2019 Ilya Kiselev
-// Copyright (c) 2019-2022 Antony Polukhin
+// Copyright (c) 2019-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/run/bitfields_count.cpp

@@ -0,0 +1,86 @@
+// Copyright (c) 2016-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/pfr/tuple_size.hpp>
+
+#include <cstdint>
+
+struct bf7 {
+    uint8_t b0 : 1;
+    uint8_t b1 : 1;
+    uint8_t b2 : 1;
+    uint8_t b3 : 1;
+    uint8_t b4 : 1;
+    uint8_t b5 : 1;
+    uint8_t b6 : 1;
+};
+static_assert(sizeof(bf7) == 1, "");
+
+struct bf8 {
+    uint8_t b0 : 1;
+    uint8_t b1 : 1;
+    uint8_t b2 : 1;
+    uint8_t b3 : 1;
+    uint8_t b4 : 1;
+    uint8_t b5 : 1;
+    uint8_t b6 : 1;
+    uint8_t b7 : 1;
+};
+static_assert(sizeof(bf8) == 1, "");
+
+struct bf16 {
+    uint8_t b0 : 1;
+    uint8_t b1 : 1;
+    uint8_t b2 : 1;
+    uint8_t b3 : 1;
+    uint8_t b4 : 1;
+    uint8_t b5 : 1;
+    uint8_t b6 : 1;
+    uint8_t b7 : 1;
+    uint8_t b8 : 1;
+    uint8_t b9 : 1;
+    uint8_t b10 : 1;
+    uint8_t b11 : 1;
+    uint8_t b12 : 1;
+    uint8_t b13 : 1;
+    uint8_t b14 : 1;
+    uint8_t b15 : 1;
+};
+static_assert(sizeof(bf16) == 2, "");
+
+struct bf24 {
+    uint8_t b0 : 1;
+    uint8_t b1 : 1;
+    uint8_t b2 : 1;
+    uint8_t b3 : 1;
+    uint8_t b4 : 1;
+    uint8_t b5 : 1;
+    uint8_t b6 : 1;
+    uint8_t b7 : 1;
+    uint8_t b8 : 1;
+    uint8_t b9 : 1;
+    uint8_t b10 : 1;
+    uint8_t b11 : 1;
+    uint8_t b12 : 1;
+    uint8_t b13 : 1;
+    uint8_t b14 : 1;
+    uint8_t b15 : 1;
+    uint8_t b16 : 1;
+    uint8_t b17 : 1;
+    uint8_t b18 : 1;
+    uint8_t b19 : 1;
+    uint8_t b20 : 1;
+    uint8_t b21 : 1;
+    uint8_t b22 : 1;
+    uint8_t b23 : 1;
+};
+static_assert(sizeof(bf24) == 3, "");
+
+int main() {
+    static_assert(boost::pfr::tuple_size_v<bf7> == 7, "");
+    static_assert(boost::pfr::tuple_size_v<bf8> == 8, "");
+    static_assert(boost::pfr::tuple_size_v<bf16> == 16, "");
+    static_assert(boost::pfr::tuple_size_v<bf24> == 24, "");
+}

test/core/run/constexpr_ops.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -13,7 +13,6 @@
 #include <set>
 #include <string>
 
-#include <boost/config.hpp>
 #include <boost/core/lightweight_test.hpp>
 
 #ifdef __clang__

test/core/run/core17_generated.cpp

@@ -0,0 +1,125 @@
+// Copyright (c) 2023 Denis Mikhailov
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/pfr/core.hpp>
+#include <type_traits> // for std::is_same
+
+struct A {
+    const volatile int cv_value = 0;
+    volatile int v_value = 0;
+    const int c_value = 0;
+    int value = 0;
+
+    const volatile int& cv_ref;
+    volatile int& v_ref;
+    const int& c_ref;
+    int& ref;
+
+    const volatile int&& cv_rref;
+    volatile int&& v_rref;
+    const int&& c_rref;
+    int&& rref;
+};
+
+int main() {
+#if BOOST_PFR_USE_CPP17 && !BOOST_PFR_USE_CPP26 && !defined(BOOST_USE_MODULES)  // TODO: fix for BOOST_USE_MODULES
+    const volatile int cv_value = 0;
+    volatile int v_value = 0;
+    const int c_value = 0;
+    int value = 0;
+
+    typedef boost::pfr::detail::size_t_<12> fields_count_tag;
+
+    {
+        A a {cv_value, v_value, c_value, value,
+             cv_value, v_value, c_value, value,
+             std::move(cv_value), std::move(v_value), std::move(c_value), std::move(value)};
+
+        const auto t = boost::pfr::detail::tie_as_tuple(a, fields_count_tag{});
+
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<0>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<1>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<2>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<3>(t)), int&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<4>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<5>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<6>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<7>(t)), int&>());
+        // FIXME implement rvalue references as a field support
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<8>(t)), int const volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<9>(t)), int volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<10>(t)), int const&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<11>(t)), int&&>());
+    }
+
+    {
+        const A a {cv_value, v_value, c_value, value,
+                   cv_value, v_value, c_value, value,
+                   std::move(cv_value), std::move(v_value), std::move(c_value), std::move(value)};
+
+        const auto t = boost::pfr::detail::tie_as_tuple(a, fields_count_tag{});
+
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<0>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<1>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<2>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<3>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<4>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<5>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<6>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<7>(t)), int&>());
+        // FIXME implement rvalue references as a field support
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<8>(t)), int const volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<9>(t)), int volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<10>(t)), int const&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<11>(t)), int&&>());
+    }
+
+    {
+        volatile A a {cv_value, v_value, c_value, value,
+                      cv_value, v_value, c_value, value,
+                      std::move(cv_value), std::move(v_value), std::move(c_value), std::move(value)};
+
+        const auto t = boost::pfr::detail::tie_as_tuple(a, fields_count_tag{});
+
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<0>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<1>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<2>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<3>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<4>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<5>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<6>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<7>(t)), int&>());
+        // FIXME implement rvalue references as a field support
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<8>(t)), int const volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<9>(t)), int volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<10>(t)), int const&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<11>(t)), int&&>());
+    }
+
+    {
+        const volatile A a {cv_value, v_value, c_value, value,
+                            cv_value, v_value, c_value, value,
+                            std::move(cv_value), std::move(v_value), std::move(c_value), std::move(value)};
+
+        const auto t = boost::pfr::detail::tie_as_tuple(a, fields_count_tag{});
+
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<0>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<1>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<2>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<3>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<4>(t)), int const volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<5>(t)), int volatile&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<6>(t)), int const&>());
+        static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<7>(t)), int&>());
+        // FIXME implement rvalue references as a field support
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<8>(t)), int const volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<9>(t)), int volatile&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<10>(t)), int const&&>());
+        // static_assert(std::is_same<decltype(boost::pfr::detail::sequence_tuple::get<11>(t)), int&&>());
+    }
+
+#endif
+}
+

test/core/run/destructuring_tie.cpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2018 Adam Butcher, Antony Polukhin
-// Copyright (c) 2019-2022 Antony Polukhin
+// Copyright (c) 2019-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/run/error_pfr_c1202.cpp

@@ -1,9 +1,9 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-// Example from https://github.com/apolukhin/magic_get/issues/21
+// Example from https://github.com/boostorg/pfr/issues/21
 
 
 // boost::pfr::for_each_field crashes when sizeof(MyConfig) > 248 (probably >= 256)
@@ -13,6 +13,11 @@
 #include <iostream>
 #include <type_traits>
 
+#if defined(BOOST_USE_MODULES) // TODO: fix for BOOST_USE_MODULES
+int main() {}
+
+#else
+
 template <typename T>
 class CfgAttrib {
 public:
@@ -99,3 +104,5 @@ int main() {
     boost::pfr::get<0>(aCfg); // also C1202
 #endif
 }
+
+#endif

test/core/run/fields_count_on_const.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 Antony Polukhin
+// Copyright (c) 2018-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

test/core/run/for_each_field.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -56,6 +56,21 @@ struct simple {
 
 struct empty{};
 
+#if BOOST_PFR_USE_CPP17
+constexpr std::size_t get_field_count_through_for_each_field() {
+    std::size_t counter = 0;
+    boost::pfr::for_each_field(simple{}, [&counter](auto&& /*val*/, std::size_t /*i*/) {
+        ++ counter;
+    });
+    return counter;
+}
+
+// MSVC-14.1 fails to compile the following code
+#if !defined(_MSC_VER) || _MSC_VER > 1916
+static_assert(3 == get_field_count_through_for_each_field());
+#endif
+
+#endif
 
 int main () {
     std::size_t control = 0;

test/core/run/functions_for.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2022 Antony Polukhin
+// Copyright (c) 2016-2026 Antony Polukhin
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -14,7 +14,7 @@
 #include <set>
 #include <string>
 
-#include <boost/functional/hash.hpp>
+#include <boost/container_hash/hash.hpp>
 #include <unordered_set>
 
 struct adl_hash {

test/core/run/get_by_type.cpp

@@ -0,0 +1,67 @@
+// Copyright (c) 2020-2026 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+#include <boost/pfr/core.hpp>
+
+#include <boost/core/lightweight_test.hpp>
+
+namespace testing {
+
+namespace {
+
+struct Aggregate {
+    int a;
+    const int b;
+    double c;
+    double d;
+    short e;
+};
+
+void test_get_by_type() {
+#if BOOST_PFR_USE_CPP17
+    Aggregate t{1, 2, 3.4, 5.6, 7};
+
+    BOOST_TEST_EQ(boost::pfr::get<int>(t), 1);
+    BOOST_TEST_EQ(boost::pfr::get<const int>(t), 2);
+    BOOST_TEST_EQ(boost::pfr::get<short>(t), 7);
+
+    boost::pfr::get<int>(t) = 11;
+    boost::pfr::get<short>(t) = 77;
+#endif
+}
+
+void test_const_get_by_type() {
+#if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
+    const Aggregate t{1, 2, 3.4, 5.6, 7};
+    BOOST_TEST_EQ(boost::pfr::get<short>(t), 7);
+#endif
+}
+
+void test_get_by_type_pod() {
+    struct PodAggregate {
+      int i;
+      short s;
+    };
+
+    PodAggregate pod{1, 2};
+    BOOST_TEST_EQ(boost::pfr::get<int>(pod), 1);
+    BOOST_TEST_EQ(boost::pfr::get<short>(pod), 2);
+}
+
+} // anonymous namespace
+
+
+} // namespace testing
+
+int main() {
+    testing::test_get_by_type();
+    testing::test_const_get_by_type();
+    testing::test_get_by_type_pod();
+
+    return boost::report_errors();
+}
+
+