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

@@ -0,0 +1,182 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - develop
+      - feature/**
+
+env:
+  UBSAN_OPTIONS: print_stacktrace=1
+
+jobs:
+  posix:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - 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-22.04
+            cxxflags: "cxxflags=--coverage -fsanitize=address,leak,undefined -fno-sanitize-recover=undefined"
+            linkflags: "linkflags=--coverage -lasan -lubsan"
+            gcov_tool: "gcov-12"
+          - toolset: clang
+            compiler: clang++-14
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-22.04
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Install packages
+        if: matrix.install
+        run: sudo apt install ${{matrix.install}}
+
+      - name: Setup Boost
+        run: |
+          echo GITHUB_REPOSITORY: $GITHUB_REPOSITORY
+          LIBRARY=${GITHUB_REPOSITORY#*/}
+          echo LIBRARY: $LIBRARY
+          echo "LIBRARY=$LIBRARY" >> $GITHUB_ENV
+          echo GITHUB_BASE_REF: $GITHUB_BASE_REF
+          echo GITHUB_REF: $GITHUB_REF
+          REF=${GITHUB_BASE_REF:-$GITHUB_REF}
+          REF=${REF#refs/heads/}
+          echo REF: $REF
+          BOOST_BRANCH=develop && [ "$REF" == "master" ] && BOOST_BRANCH=master || true
+          echo BOOST_BRANCH: $BOOST_BRANCH
+          cd ..
+          git clone -b $BOOST_BRANCH --depth 10 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          git submodule update --init --depth 10 --jobs 2 tools/boostdep tools/inspect libs/filesystem
+          python tools/boostdep/depinst/depinst.py --git_args "--depth 10 --jobs 3" filesystem
+          rm -rf libs/$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 -j4 variant=debug tools/inspect
+
+      - name: Run CMake tests
+        if: ${{matrix.toolset == 'gcc-14'}}
+        run: |
+          cd ../boost-root/
+          mkdir __build
+          cd __build
+          cmake -DBUILD_TESTING=1 -DBOOST_INCLUDE_LIBRARIES=conversion -DCMAKE_CXX_COMPILER=g++-14 -DCMAKE_C_COMPILER=gcc-14 ..
+          cmake --build . --target tests
+          ctest --output-on-failure --no-tests=error
+          cd ..
+          rm -rf __build
+
+      - name: Run tests
+        run: |
+          cd ../boost-root
+          ./b2 -j3 libs/$LIBRARY/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} variant=debug,release "${{matrix.cxxflags}}" "${{matrix.linkflags}}" "${{matrix.launcher}}"
+          dist/bin/inspect libs/$LIBRARY
+
+      - name: Prepare coverage data
+        if: matrix.gcov_tool
+        run: |
+          mkdir -p $GITHUB_WORKSPACE/coveralls
+
+          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/v1.16.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
+          $LCOV --remove $GITHUB_WORKSPACE/coveralls/coverage.info "/usr*" "*/$LIBRARY/test/*" ${{matrix.ignore_coverage}} "*/$LIBRARY/tests/*" "*/$LIBRARY/examples/*" "*/$LIBRARY/example/*" -o $GITHUB_WORKSPACE/coveralls/coverage.info
+
+          cd ../boost-root
+          OTHER_LIBS=`grep "submodule .*" .gitmodules | sed 's/\[submodule\ "\(.*\)"\]/"\*\/boost\/\1\.hpp" "\*\/boost\/\1\/\*"/g'| sed "/\"\*\/boost\/$LIBRARY\/\*\"/d" | sed ':a;N;$!ba;s/\n/ /g'`
+          echo $OTHER_LIBS
+          eval "$LCOV --remove $GITHUB_WORKSPACE/coveralls/coverage.info $OTHER_LIBS -o $GITHUB_WORKSPACE/coveralls/coverage.info"
+
+      - name: Coveralls
+        uses: coverallsapp/github-action@master
+        if: matrix.gcov_tool
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          path-to-lcov: ./coveralls/coverage.info
+          parallel: true
+
+  windows:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - toolset: msvc-14.3
+            cxxstd: "14,17,latest"
+            addrmd: 32,64
+            os: windows-2025
+          - toolset: gcc
+            cxxstd: "03,11,14,17,2a"
+            addrmd: 64
+            os: windows-2025
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Setup Boost
+        shell: cmd
+        run: |
+          echo GITHUB_REPOSITORY: %GITHUB_REPOSITORY%
+          for /f %%i in ("%GITHUB_REPOSITORY%") do set LIBRARY=%%~nxi
+          echo LIBRARY: %LIBRARY%
+          echo LIBRARY=%LIBRARY%>>%GITHUB_ENV%
+          echo GITHUB_BASE_REF: %GITHUB_BASE_REF%
+          echo GITHUB_REF: %GITHUB_REF%
+          if "%GITHUB_BASE_REF%" == "" set GITHUB_BASE_REF=%GITHUB_REF%
+          set BOOST_BRANCH=develop
+          for /f %%i in ("%GITHUB_BASE_REF%") do if "%%~nxi" == "master" set BOOST_BRANCH=master
+          echo BOOST_BRANCH: %BOOST_BRANCH%
+          cd ..
+          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
+          python tools/boostdep/depinst/depinst.py --include benchmark --include example --include examples --include tools --git_args "--jobs 3" %LIBRARY%
+          cmd /c bootstrap
+
+      - name: Run CMake tests
+        if: ${{matrix.toolset == 'msvc-14.3'}}
+        shell: cmd
+        run: |
+          choco install --no-progress ninja
+          call "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvarsall.bat" x64
+          cd ../boost-root/
+          mkdir __build
+          cd __build
+          cmake -DBUILD_TESTING=1 -DBOOST_INCLUDE_LIBRARIES=conversion ..
+          cmake --build . --target tests --config Debug
+          ctest --output-on-failure --no-tests=error -C Debug
+          cd ..
+          rm -rf __build
+
+      - name: Run tests
+        shell: cmd
+        run: |
+          cd ../boost-root
+          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release
+
+  finish:
+    needs: posix
+    runs-on: ubuntu-latest
+    steps:
+    - name: Coveralls Finished
+      uses: coverallsapp/github-action@master
+      with:
+        github-token: ${{ secrets.github_token }}
+        parallel-finished: true

CMakeLists.txt

@@ -0,0 +1,22 @@
+# Copyright 2019 Mike Dev
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
+
+cmake_minimum_required( VERSION 3.5...4.20 )
+project( boost_conversion VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX )
+
+add_library( boost_conversion INTERFACE )
+add_library( Boost::conversion ALIAS boost_conversion )
+
+target_include_directories( boost_conversion INTERFACE include )
+
+target_link_libraries( boost_conversion
+    INTERFACE
+        Boost::assert
+        Boost::config
+        Boost::throw_exception
+)
+
+if(BUILD_TESTING)
+  add_subdirectory(test)
+endif()

README.md

@@ -0,0 +1,15 @@
+# [Boost.Conversion](https://boost.org/libs/conversion)
+Boost.Conversion is one of the [Boost C++ Libraries](https://github.com/boostorg). This library improves program safety and clarity by performing otherwise messy conversions. 
+
+### Test results
+
+@               | Build         | Tests coverage | More info
+----------------|-------------- | -------------- |-----------
+Develop branch: | [![CI](https://github.com/boostorg/conversion/actions/workflows/ci.yml/badge.svg?branch=develop)](https://github.com/boostorg/conversion/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/1cky1hrunfa46bdx/branch/develop?svg=true)](https://ci.appveyor.com/project/apolukhin/conversion/branch/develop) | [![Coverage Status](https://coveralls.io/repos/github/boostorg/conversion/badge.svg?branch=develop)](https://coveralls.io/github/boostorg/conversion?branch=develop) | [details...](https://regression.boost.io/develop/developer/conversion.html)
+Master branch:  | [![CI](https://github.com/boostorg/conversion/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/boostorg/conversion/actions/workflows/ci.yml) [![Build status](https://ci.appveyor.com/api/projects/status/1cky1hrunfa46bdx/branch/master?svg=true)](https://ci.appveyor.com/project/apolukhin/conversion/branch/master) | [![Coverage Status](https://coveralls.io/repos/github/boostorg/conversion/badge.svg?branch=master)](https://coveralls.io/github/boostorg/conversion?branch=master) | [details...](https://regression.boost.io/master/developer/conversion.html)
+
+[Latest developer documentation](https://www.boost.org/doc/libs/develop/doc/html/conversion.html)
+
+### License
+
+Distributed under the [Boost Software License, Version 1.0](https://boost.org/LICENSE_1_0.txt).

build.jam

@@ -0,0 +1,25 @@
+# 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 ;
+
+constant boost_dependencies :
+    /boost/assert//boost_assert
+    /boost/config//boost_config
+    /boost/throw_exception//boost_throw_exception ;
+
+project /boost/conversion
+    : common-requirements
+        <include>include
+    ;
+
+explicit
+    [ alias boost_conversion : : : : <library>$(boost_dependencies) ]
+    [ alias all : boost_conversion test ]
+    ;
+
+call-if : boost-library conversion
+    ;
+

doc/Jamfile.v2

@@ -0,0 +1,38 @@
+#   Copyright (c) 2016 Mikhail Maximov <vigorous.activity -at- gmail.com>
+
+#   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)
+
+project doc/conversion ;
+
+using quickbook ;
+import boostbook ;
+
+xml conversion : conversion.qbk ;
+boostbook standalone
+    :
+        conversion
+    :
+        <xsl:param>boost.root=../../../..
+        # File name of HTML output:
+        <xsl:param>root.filename=conversion
+        # How far down we chunk nested sections, basically all of them:
+        <xsl:param>chunk.section.depth=0
+        # Don't put the first section on the same page as the TOC:
+        <xsl:param>chunk.first.sections=0
+        # How far down sections get TOC's
+        <xsl:param>toc.section.depth=2
+        # Max depth in each TOC:
+        <xsl:param>toc.max.depth=2
+        # How far down we go with TOC's
+        <xsl:param>generate.section.toc.level=0
+
+        <xsl:param>generate.manifest=0
+     ;
+
+###############################################################################
+alias boostdoc : conversion ;
+explicit boostdoc ;
+alias boostrelease ;
+explicit boostrelease ;

doc/conversion.qbk

@@ -0,0 +1,215 @@
+[/
+    Copyright 2016 Mikhail Maximov.
+    Copyright Antony Polukhin, 2020-2026.
+
+    Distributed under the Boost Software License, Version 1.0. (See accompanying
+    file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)
+]
+
+[article The Conversion Library
+    [quickbook 1.6]
+    [compatibility-mode 1.5]
+    [id conversion]
+    [version 1.7]
+    [authors [Stroustrup, Bjarne], [Abrahams, Dave], [Rasin, Boris], [Polukhin, Antony]]
+    [copyright 2001 Beman Dawes, 2014-2026 Antony Polukhin]
+    [license
+        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])
+    ]
+    [source-mode c++]
+]
+
+[/ QuickBook Document version 1.5 ]
+[/ Dec, 2016 ]
+
+[section Description]
+
+The Conversion Library improves program safety and clarity by performing
+otherwise messy conversions. It includes cast-style function templates designed 
+to complement the C++ Standard's built-in casts.
+
+To reduce coupling, the Boost Conversion Library is supplied by several headers:
+
+# The [@boost:boost/polymorphic_cast.hpp boost/polymorphic_cast.hpp] header
+  provides [link polymorphic_cast `polymorphic_cast<>`] and
+  [link polymorphic_downcast `polymorphic_downcast<>`]
+  to perform safe casting between polymorphic types.
+# The [@boost:boost/polymorphic_pointer_cast.hpp boost/polymorphic_pointer_cast.hpp] header
+  provides [link polymorphic_pointer_cast `polymorphic_pointer_cast<>`] and
+  [link polymorphic_pointer_cast `polymorphic_pointer_downcast<>`]
+# The [@boost:boost/implicit_cast.hpp boost/implicit_cast.hpp] header provides `implicit_cast<>` 
+  to perform implicit casts only (no down-cast, no void*->T*, no U->T if T has only explicit constructors for U).
+
+[endsect]
+
+[section Polymorphic casts]
+Pointers to polymorphic objects (objects of classes which define at
+least one virtual function) are sometimes downcast or crosscast.
+Downcasting means casting from a base class to a derived class.
+Crosscasting means casting across an inheritance hierarchy diagram, such
+as from one base to the other in a [^Y] diagram hierarchy.
+
+Such casts can be done with old-style casts, but this approach is
+never to be recommended. Old-style casts are sorely lacking in type
+safety, suffer poor readability, and are difficult to locate with search
+tools.
+
+[#polymorphic_downcast]
+[section polymorphic_downcast]
+
+The C++ built-in `static_cast` can be used for efficiently
+downcasting pointers to polymorphic objects, but provides no error
+detection for the case where the pointer being cast actually points to
+the wrong derived class. The `polymorphic_downcast` template retains
+the efficiency of `static_cast` for non-debug compilations, but for
+debug compilations adds safety via an `assert()` that a `dynamic_cast`
+succeeds.
+
+A `polymorphic_downcast` should be used for
+downcasts that you are certain should succeed. Error checking is
+only performed in translation units where `NDEBUG` is
+not defined, via
+```
+    assert( dynamic_cast<Derived>(x) == x )
+```
+where `x` is the source pointer.  This approach
+ensures that not only is a non-zero pointer returned, but also
+that it is correct in the presence of multiple inheritance.
+Attempts to crosscast using `polymorphic_downcast` will
+fail to compile.
+
+[warning Because `polymorphic_downcast` uses `assert()`, it
+violates the One Definition Rule (ODR) if `NDEBUG` is inconsistently
+defined across translation units. See ISO Std 3.2]
+
+[h4 Example:]
+```
+    #include <boost/polymorphic_cast.hpp>
+    ...
+    class Fruit { public: virtual ~Fruit(){}; ... };
+    class Banana : public Fruit { ... };
+    ...
+    void f( Fruit * fruit ) {
+      // ... logic which leads us to believe it is a Banana
+      Banana * banana = boost::polymorphic_downcast<Banana*>(fruit);
+      ...
+    }
+```
+[endsect]
+
+[#polymorphic_cast]
+[section polymorphic_cast]
+
+The C++ built-in `dynamic_cast` can be used for downcasts and
+crosscasts of pointers to polymorphic objects, but error notification in
+the form of a returned value of 0 is inconvenient to test, or worse yet,
+easy to forget to test. The throwing form of `dynamic_cast`, which
+works on references, can be used on pointers through the ugly expression
+`&dynamic_cast<T&>(*p)`, which causes undefined
+behavior if `p` is `0`. The `polymorphic_cast`
+template performs a `dynamic_cast` on a pointer, and throws an
+exception if the `dynamic_cast` returns 0.
+
+For crosscasts, or when the success of a cast can only be known at runtime, 
+or when efficiency is not important, `polymorphic_cast` is preferred.
+
+The C++ built-in `dynamic_cast` must be used to cast references rather than pointers.
+It is also the only cast that can be used to check whether a given interface is supported; in that case a return of 0 isn't an error condition.
+
+[endsect]
+
+
+[#polymorphic_pointer_cast]
+[section polymorphic_pointer_cast]
+While `polymorphic_downcast` and `polymorphic_cast` work with built-in pointer types only,
+`polymorphic_pointer_downcast` and `polymorphic_pointer_cast` are more generic versions
+with support for any pointer type for which the following expressions would be valid:
+
+For `polymorphic_pointer_downcast`:
+```
+    static_pointer_cast<Derived>(p);
+    dynamic_pointer_cast<Derived>(p);
+```
+For `polymorphic_pointer_cast`:
+```
+    dynamic_pointer_cast<Derived>(p);
+    !p; // conversion to bool with negation
+```
+
+This includes C++ built-in pointers, `std::shared_ptr`,
+`boost::shared_ptr`, `boost::intrusive_ptr`, etc.
+
+
+[h4 Example:]
+```
+    #include <boost/polymorphic_pointer_cast.hpp>
+
+    class Fruit { public: virtual ~Fruit(){} };
+    class Banana : public Fruit {};
+
+    // Use one of these:
+    using FruitPtr = Fruit*;
+    using FruitPtr = std::shared_ptr<Fruit>;
+    using FruitPtr = boost::shared_ptr<Fruit>;
+    using FruitPtr = boost::intrusive_ptr<Fruit>;
+
+    void f(FruitPtr fruit) {
+      // ... logic which leads us to believe it is a banana
+      auto banana = boost::polymorphic_pointer_downcast<Banana>(fruit);
+      ...
+    }
+```
+
+[endsect]
+
+[endsect]
+
+[section Synopsis]
+```
+    namespace boost {
+
+    // Throws: std::bad_cast if ( dynamic_cast<Derived>(x) == 0 )
+    // Returns: dynamic_cast<Derived>(x)
+    template <class Derived, class Base>
+    constexpr Derived polymorphic_cast(Base* x);
+
+    // Effects: assert( dynamic_cast<Derived>(x) == x );
+    // Returns: static_cast<Derived>(x)
+    template <class Derived, class Base>
+    constexpr Derived polymorphic_downcast(Base* x);
+
+    // Effects: assert( dynamic_cast<Derived>(&x) == &x );
+    // Returns: static_cast<Derived>(x)
+    template <class Derived, class Base>
+    constexpr Derived polymorphic_downcast(Base& x);
+
+    // Throws: std::bad_cast if ( dynamic_pointer_cast<Derived>(x) == 0 )
+    // Returns: dynamic_pointer_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline auto polymorphic_pointer_cast(Base x);
+
+    // Effects: assert( dynamic_pointer_cast<Derived>(x) == x );
+    // Returns: static_pointer_cast<Derived>(x)
+    template <class Derived, class Base>
+    inline auto polymorphic_pointer_downcast(Base x);
+
+    }
+```
+[endsect]
+
+
+[section History]
+`polymorphic_cast` was suggested by Bjarne Stroustrup in "The C++ Programming Language".
+
+`polymorphic_downcast` was contributed by [@http://www.boost.org/people/dave_abrahams.htm Dave Abrahams].
+
+`polymorphic_pointer_downcast` was contributed by [@http://www.boost.org/people/boris_rasin.htm Boris Rasin]
+and `polymorphic_pointer_cast` by Antony Polukhin.
+
+`polymorphic_downcast` overload for references was contributed by Julien Delacroix.
+
+An old `numeric_cast` that was contributed by [@http://www.boost.org/people/kevlin_henney.htm Kevlin Henney]
+is now superseded by the [@boost:numeric_conversion/doc/html/html/boost_numericconversion/improved_numeric_cast__.html Boost Numeric Conversion Library]
+[endsect]

include/boost/cast.hpp

@@ -1,257 +0,0 @@
-//  boost cast.hpp header file  ----------------------------------------------//
-
-//  (C) Copyright boost.org 1999. Permission to copy, use, modify, sell
-//  and distribute this software is granted provided this copyright
-//  notice appears in all copies. This software is provided "as is" without
-//  express or implied warranty, and with no claim as to its suitability for
-//  any purpose.
-
-//  See http://www.boost.org for most recent version including documentation.
-
-//  Revision History
-//  15 Jul 00  Suppress numeric_cast warnings for GCC, Borland and MSVC (Dave Abrahams)
-//  30 Jun 00  More MSVC6 wordarounds.  See comments below.  (Dave Abrahams)
-//  28 Jun 00  Removed implicit_cast<>.  See comment below. (Beman Dawes)
-//  27 Jun 00  More MSVC6 workarounds 
-//  15 Jun 00  Add workarounds for MSVC6
-//   2 Feb 00  Remove bad_numeric_cast ";" syntax error (Doncho Angelov)
-//  26 Jan 00  Add missing throw() to bad_numeric_cast::what(0 (Adam Levar)
-//  29 Dec 99  Change using declarations so usages in other namespaces work
-//             correctly (Dave Abrahams)
-//  23 Sep 99  Change polymorphic_downcast assert to also detect M.I. errors
-//             as suggested Darin Adler and improved by Valentin Bonnard.  
-//   2 Sep 99  Remove controversial asserts, simplify, rename.
-//  30 Aug 99  Move to cast.hpp, replace value_cast with numeric_cast,
-//             place in nested namespace.
-//   3 Aug 99  Initial version
-
-#ifndef BOOST_CAST_HPP
-#define BOOST_CAST_HPP
-
-# include <boost/config.hpp>
-# include <cassert>
-# include <typeinfo> 
-# include <limits>
-
-//  It has been demonstrated numerous times that MSVC 6.0 fails silently at link
-//  time if you use a template function which has template parameters that don't
-//  appear in the function's argument list.
-//
-//  TODO: Add this to config.hpp?
-# if defined(BOOST_MSVC) && BOOST_MSVC <= 1200 // 1200 = VC6
-#  define BOOST_EXPLICIT_DEFAULT_TARGET , ::boost::detail::type_wrapper<Target>* = 0
-#  define BOOST_EXPLICIT_TARGET ,::boost::detail::type_wrapper<Target>*
-# else
-#  define BOOST_EXPLICIT_DEFAULT_TARGET
-#  define BOOST_EXPLICIT_TARGET
-# endif
-
-namespace boost
-{
-  namespace detail {
-    template <class T> struct type_wrapper {};
-  }
-#if !(defined(BOOST_MSVC) && BOOST_MSVC <= 1200) // 1200 = VC6
-  namespace cast
-  {
-#endif
-
-//  See the documentation for descriptions of how to choose between
-//  static_cast<>, dynamic_cast<>, polymorphic_cast<>. and down_cast<>
-
-//  polymorphic_cast  --------------------------------------------------------//
-
-    //  Runtime checked polymorphic downcasts and crosscasts.
-    //  Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup, 
-    //  section 15.8 exercise 1, page 425.
-
-    template <class Target, class Source>
-    inline Target polymorphic_cast(Source* x BOOST_EXPLICIT_DEFAULT_TARGET)
-    {
-        Target tmp = dynamic_cast<Target>(x);
-        if ( tmp == 0 ) throw std::bad_cast();
-        return tmp;
-    }
-
-//  polymorphic_downcast  ----------------------------------------------------//
-
-    //  assert() checked polymorphic downcast.  Crosscasts prohibited.
-
-    //  WARNING: Because this cast uses assert(), it violates the One Definition
-    //  Rule if NDEBUG is inconsistently defined across translation units.
-
-    //  Contributed by Dave Abrahams
-
-    template <class Target, class Source>
-    inline Target polymorphic_downcast(Source* x BOOST_EXPLICIT_DEFAULT_TARGET)
-    {
-        assert( dynamic_cast<Target>(x) == x );  // detect logic error
-        return static_cast<Target>(x);
-    }
-
-//  implicit_cast  -----------------------------------------------------------//
-//
-//  Removed due to uncertain purpose.  Use either numeric_cast (see below)
-//  or static_cast according to the need. 
-
-//  numeric_cast and related exception  --------------------------------------//
-
-//  Contributed by Kevlin Henney
-
-//  bad_numeric_cast  --------------------------------------------------------//
-
-    // exception used to indicate runtime numeric_cast failure
-    class bad_numeric_cast : public std::bad_cast
-    {
-    public:
-        // constructors, destructors and assignment operator defaulted
-
-        // function inlined for brevity and consistency with rest of library
-        virtual const char *what() const throw()
-        {
-            return "bad numeric cast: loss of range in numeric_cast";
-        }
-    };
-
-//  numeric_cast  ------------------------------------------------------------//
-
-// Move to config.hpp?
-#if defined(__SGI_STL_PORT) && __SGI_STL_PORT <= 0x400 && __STL_STATIC_CONST_INIT_BUG
-// STLPort 4.0 doesn't define the static constants in numeric_limits<> so that they
-// can be used at compile time if the compiler bug indicated by
-// __STL_STATIC_CONST_INIT_BUG is present.
-# define BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
-#endif
-
-#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
-  // less_than_type_min -
-  //    x_is_signed should be numeric_limits<X>::is_signed
-  //    y_is_signed should be numeric_limits<Y>::is_signed
-  //    y_min should be numeric_limits<Y>::min()
-  //
-  //    check(x, y_min) returns true iff x < y_min without invoking comparisons
-  //    between signed and unsigned values.
-  //
-  //    "poor man's partial specialization" is in use here.
-    template <bool x_is_signed, bool y_is_signed>
-    struct less_than_type_min
-    {
-        template <class X, class Y>
-        static bool check(X x, Y y_min)
-            { return x < y_min; }
-    };
-
-    template <>
-    struct less_than_type_min<false, true>
-    {
-        template <class X, class Y>
-        static bool check(X, Y)
-            { return false; }
-    };
-    
-    template <>
-    struct less_than_type_min<true, false>
-    {
-        template <class X, class Y>
-        static bool check(X x, Y)
-            { return x < 0; }
-    };
-    
-  // greater_than_type_max -
-  //    same_sign should be:
-  //            numeric_limits<X>::is_signed == numeric_limits<Y>::is_signed
-  //    y_max should be numeric_limits<Y>::max()
-  //
-  //    check(x, y_max) returns true iff x > y_max without invoking comparisons
-  //    between signed and unsigned values.
-  //
-  //    "poor man's partial specialization" is in use here.
-    template <bool same_sign>
-    struct greater_than_type_max;
-
-    template<>
-    struct greater_than_type_max<true>
-    {
-        template <class X, class Y>
-        static bool check(X x, Y y_max)
-            { return x > y_max; }
-    };
-
-    template <>
-    struct greater_than_type_max<false>
-    {
-        // What does the standard say about this? I think it's right, and it
-        // will work with every compiler I know of.
-        template <class X, class Y>
-        static bool check(X x, Y)
-            { return x >= 0 && static_cast<X>(static_cast<Y>(x)) != x; }
-    };
-#endif
-  
-    template<typename Target, typename Source>
-    inline Target numeric_cast(Source arg BOOST_EXPLICIT_DEFAULT_TARGET)
-    {
-        // typedefs abbreviating respective trait classes
-        typedef std::numeric_limits<Source> arg_traits;
-        typedef std::numeric_limits<Target> result_traits;
-
-#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
-        // typedefs that act as compile time assertions
-        // (to be replaced by boost compile time assertions
-        // as and when they become available and are stable)
-        typedef bool argument_must_be_numeric[arg_traits::is_specialized];
-        typedef bool result_must_be_numeric[result_traits::is_specialized];
-
-        const bool arg_is_signed = arg_traits::is_signed;
-        const bool result_is_signed = result_traits::is_signed;
-        const bool same_sign = arg_is_signed == result_is_signed;
-
-        if (less_than_type_min<arg_is_signed, result_is_signed>::check(arg, result_traits::min())
-            || greater_than_type_max<same_sign>::check(arg, result_traits::max())
-            )
-            
-#else // We need to use #pragma hacks if available
-            
-# if BOOST_MSVC
-#  pragma warning(push)
-#  pragma warning(disable : 4018)
-# endif
-        if ( (arg < 0 && !result_traits::is_signed) ||  // loss of negative range
-              (arg_traits::is_signed &&
-                 arg < result_traits::min()) ||        // underflow
-               arg > result_traits::max() )            // overflow
-# if BOOST_MSVC
-#  pragma warning(pop)
-# endif
-#endif
-        {
-            throw bad_numeric_cast();
-        }
-        return static_cast<Target>(arg);
-    }
-
-//  Visual C++ workarounds  --------------------------------------------------//
-
-#  if !(defined(BOOST_MSVC) && BOOST_MSVC <= 1200) // 1200 = VC6
-  } // namespace cast
-
-  using ::boost::cast::polymorphic_cast;
-  using ::boost::cast::polymorphic_downcast;
-  using ::boost::cast::bad_numeric_cast;
-  using ::boost::cast::numeric_cast;
-#  else
-  namespace cast {
-    using ::boost::polymorphic_cast;
-    using ::boost::polymorphic_downcast;
-    using ::boost::bad_numeric_cast;
-    using ::boost::numeric_cast;
-  }
-#  endif
-
-#  undef BOOST_EXPLICIT_DEFAULT_TARGET
-#  undef BOOST_EXPLICIT_TARGET
-
-} // namespace boost
-
-#endif  // BOOST_CAST_HPP
-

include/boost/implicit_cast.hpp

@@ -0,0 +1,38 @@
+// Copyright David Abrahams 2003.
+// 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_IMPLICIT_CAST_DWA200356_HPP
+#define BOOST_IMPLICIT_CAST_DWA200356_HPP
+
+#include <boost/config.hpp>
+#ifdef BOOST_HAS_PRAGMA_ONCE
+# pragma once
+#endif
+
+namespace boost {
+
+namespace detail {
+
+template<class T> struct icast_identity
+{
+    using type = T;
+};
+
+} // namespace detail
+
+// implementation originally suggested by C. Green in
+// http://lists.boost.org/MailArchives/boost/msg00886.php
+
+// The use of identity creates a non-deduced form, so that the
+// explicit template argument must be supplied
+template <typename T>
+constexpr T implicit_cast (typename boost::detail::icast_identity<T>::type x) {
+    return x;
+}
+
+} // namespace boost
+
+
+#endif // BOOST_IMPLICIT_CAST_DWA200356_HPP

include/boost/polymorphic_cast.hpp

@@ -0,0 +1,132 @@
+//  boost polymorphic_cast.hpp header file  ----------------------------------------------//
+
+//  (C) Copyright Kevlin Henney and Dave Abrahams 1999.
+//  (C) Copyright Boris Rasin 2014.
+//  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)
+
+//  See http://www.boost.org/libs/conversion for Documentation.
+
+//  Revision History
+//  10 Nov 14  polymorphic_pointer_downcast moved to a separate header,
+//             minor improvements to stisfy latest Boost coding style
+//  08 Nov 14  Add polymorphic_pointer_downcast (Boris Rasin)
+//  09 Jun 14  "cast.hpp" was renamed to "polymorphic_cast.hpp" and
+//             inclusion of numeric_cast was removed (Antony Polukhin)
+//  23 Jun 05  numeric_cast removed and redirected to the new version (Fernando Cacciola)
+//  02 Apr 01  Removed BOOST_NO_LIMITS workarounds and included
+//             <boost/limits.hpp> instead (the workaround did not
+//             actually compile when BOOST_NO_LIMITS was defined in
+//             any case, so we loose nothing). (John Maddock)
+//  21 Jan 01  Undid a bug I introduced yesterday. numeric_cast<> never
+//             worked with stock GCC; trying to get it to do that broke
+//             vc-stlport.
+//  20 Jan 01  Moved BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS to config.hpp.
+//             Removed unused BOOST_EXPLICIT_TARGET macro. Moved
+//             boost::detail::type to boost/type.hpp. Made it compile with
+//             stock gcc again (Dave Abrahams)
+//  29 Nov 00  Remove nested namespace cast, cleanup spacing before Formal
+//             Review (Beman Dawes)
+//  19 Oct 00  Fix numeric_cast for floating-point types (Dave Abrahams)
+//  15 Jul 00  Suppress numeric_cast warnings for GCC, Borland and MSVC
+//             (Dave Abrahams)
+//  30 Jun 00  More MSVC6 workarounds.  See comments below.  (Dave Abrahams)
+//  28 Jun 00  Removed implicit_cast<>.  See comment below. (Beman Dawes)
+//  27 Jun 00  More MSVC6 workarounds
+//  15 Jun 00  Add workarounds for MSVC6
+//   2 Feb 00  Remove bad_numeric_cast ";" syntax error (Doncho Angelov)
+//  26 Jan 00  Add missing throw() to bad_numeric_cast::what(0 (Adam Levar)
+//  29 Dec 99  Change using declarations so usages in other namespaces work
+//             correctly (Dave Abrahams)
+//  23 Sep 99  Change polymorphic_downcast assert to also detect M.I. errors
+//             as suggested Darin Adler and improved by Valentin Bonnard.
+//   2 Sep 99  Remove controversial asserts, simplify, rename.
+//  30 Aug 99  Move to cast.hpp, replace value_cast with numeric_cast,
+//             place in nested namespace.
+//   3 Aug 99  Initial version
+
+#ifndef BOOST_POLYMORPHIC_CAST_HPP
+#define BOOST_POLYMORPHIC_CAST_HPP
+
+#include <boost/config.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#   pragma once
+#endif
+
+# include <boost/assert.hpp>
+# include <boost/throw_exception.hpp>
+
+# include <memory>  // std::addressof
+# include <typeinfo>
+# include <type_traits>
+
+#if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
+#define BOOST_CONVERSION_IMPL_CONSTEXPR_DYN_CAST constexpr
+#else
+#define BOOST_CONVERSION_IMPL_CONSTEXPR_DYN_CAST inline
+#endif
+
+namespace boost
+{
+//  See the documentation for descriptions of how to choose between
+//  static_cast<>, dynamic_cast<>, polymorphic_cast<> and polymorphic_downcast<>
+
+//  polymorphic_cast  --------------------------------------------------------//
+
+    //  Runtime checked polymorphic downcasts and crosscasts.
+    //  Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup,
+    //  section 15.8 exercise 1, page 425.
+
+    template <class Target, class Source>
+    BOOST_CONVERSION_IMPL_CONSTEXPR_DYN_CAST Target polymorphic_cast(Source* x)
+    {
+        Target tmp = dynamic_cast<Target>(x);
+        if ( tmp == 0 ) boost::throw_exception( std::bad_cast() );
+        return tmp;
+    }
+
+//  polymorphic_downcast  ----------------------------------------------------//
+
+    //  BOOST_ASSERT() checked raw pointer polymorphic downcast.  Crosscasts prohibited.
+
+    //  WARNING: Because this cast uses BOOST_ASSERT(), it violates
+    //  the One Definition Rule if used in multiple translation units
+    //  where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
+    //  NDEBUG are defined inconsistently.
+
+    //  Contributed by Dave Abrahams
+
+    template <class Target, class Source>
+    BOOST_CONVERSION_IMPL_CONSTEXPR_DYN_CAST Target polymorphic_downcast(Source* x)
+    {
+        BOOST_ASSERT( dynamic_cast<Target>(x) == x );  // detect logic error
+        return static_cast<Target>(x);
+    }
+
+    //  BOOST_ASSERT() checked reference polymorphic downcast.  Crosscasts prohibited.
+
+    //  WARNING: Because this cast uses BOOST_ASSERT(), it violates
+    //  the One Definition Rule if used in multiple translation units
+    //  where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
+    //  NDEBUG are defined inconsistently.
+
+    //  Contributed by Julien Delacroix
+
+    template <class Target, class Source>
+    BOOST_CONVERSION_IMPL_CONSTEXPR_DYN_CAST typename std::enable_if<
+        std::is_reference<Target>::value, Target
+    >::type polymorphic_downcast(Source& x)
+    {
+        using target_pointer_type = typename std::remove_reference<Target>::type*;
+        return *boost::polymorphic_downcast<target_pointer_type>(
+            std::addressof(x)
+        );
+    }
+
+} // namespace boost
+
+#undef BOOST_CONVERSION_IMPL_CONSTEXPR_DYN_CAST
+
+#endif  // BOOST_POLYMORPHIC_CAST_HPP

include/boost/polymorphic_pointer_cast.hpp

@@ -0,0 +1,60 @@
+//  boost polymorphic_pointer_cast.hpp header file  ----------------------------------------------//
+//  (C) Copyright Boris Rasin, 2014-2021.
+//  (C) Copyright Antony Polukhin, 2014-2026.
+//  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)
+
+//  See http://www.boost.org/libs/conversion for Documentation.
+
+#ifndef BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP
+#define BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP
+
+#include <boost/config.hpp>
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#   pragma once
+#endif
+
+# include <boost/assert.hpp>
+# include <boost/pointer_cast.hpp>
+# include <boost/throw_exception.hpp>
+
+
+namespace boost
+{
+//  See the documentation for descriptions of how to choose between
+//  static_pointer_cast<>, dynamic_pointer_cast<>, polymorphic_pointer_cast<> and polymorphic_pointer_downcast<>
+
+//  polymorphic_pointer_downcast  --------------------------------------------//
+
+    //  BOOST_ASSERT() checked polymorphic downcast.  Crosscasts prohibited.
+    //  Supports any type with static_pointer_cast/dynamic_pointer_cast functions:
+    //  built-in pointers, std::shared_ptr, boost::shared_ptr, boost::intrusive_ptr, etc.
+
+    //  WARNING: Because this cast uses BOOST_ASSERT(), it violates
+    //  the One Definition Rule if used in multiple translation units
+    //  where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
+    //  NDEBUG are defined inconsistently.
+
+    //  Contributed by Boris Rasin
+
+    template <typename Target, typename Source>
+    inline auto polymorphic_pointer_downcast (const Source& x)
+        -> decltype(static_pointer_cast<Target>(x))
+    {
+        BOOST_ASSERT(dynamic_pointer_cast<Target> (x) == x);
+        return static_pointer_cast<Target> (x);
+    }
+
+    template <typename Target, typename Source>
+    inline auto polymorphic_pointer_cast (const Source& x)
+        -> decltype(dynamic_pointer_cast<Target>(x))
+    {
+        auto tmp = dynamic_pointer_cast<Target> (x);
+        if ( !tmp ) boost::throw_exception( std::bad_cast() );
+        return tmp;
+    }
+
+} // namespace boost
+
+#endif  // BOOST_CONVERSION_POLYMORPHIC_POINTER_CAST_HPP

index.html

@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<!--
+ Copyright (c) 2016 Mikhail Maximov
+ vigorous.activity at gmail dot com
+
+ Copyright (c) Antony Polukhin, 2021-2026
+
+ 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=../../doc/html/conversion.html">
+<title>Boost.Conversion</title>
+<style>
+  body {
+    background: #fff;
+    color: #000;
+  }
+  a {
+    color: #00f;
+    text-decoration: none;
+  }
+</style>
+</head>
+<body>
+  <p>
+    Automatic redirection failed, please go to
+    <a href="../../doc/html/conversion.html">../../doc/html/conversion.html</a>
+  </p>
+  <p>
+    &copy; Antony Polukhin, 2014-2024
+  </p>
+</body>
+</html>

meta/libraries.json

@@ -0,0 +1,16 @@
+{
+    "key": "conversion",
+    "name": "Conversion",
+    "authors": [
+        "Dave Abrahams",
+        "Kevlin Henney"
+    ],
+    "description": "Polymorphic casts.",
+    "category": [
+        "Miscellaneous"
+    ],
+    "maintainers": [
+        "Antony Polukhin <antoshkka -at- gmail.com>"
+    ],
+    "cxxstd": "11"
+}

test/CMakeLists.txt

@@ -0,0 +1,17 @@
+# 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(BoostTest OPTIONAL RESULT_VARIABLE HAVE_BOOST_TEST)
+
+if(NOT HAVE_BOOST_TEST)
+  return()
+endif()
+
+set(BOOST_TEST_LINK_LIBRARIES Boost::conversion Boost::core)
+
+boost_test(TYPE run SOURCES cast_test.cpp)
+boost_test(TYPE run SOURCES implicit_cast.cpp)
+boost_test(TYPE compile-fail SOURCES implicit_cast_fail.cpp)
+boost_test(TYPE compile-fail SOURCES implicit_cast_fail2.cpp)
+boost_test(TYPE run SOURCES polymorphic_cast_test.cpp LINK_LIBRARIES Boost::smart_ptr)

test/Jamfile.v2

@@ -0,0 +1,31 @@
+# Copyright (C) 2001-2003 Douglas Gregor
+# Copyright (C) Antony Polukhin, 2011-2024
+#
+# 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 5.0.1 ;
+import-search /boost/config/checks ;
+import config : requires ;
+import testing ;
+import feature ;
+
+project
+    : requirements
+        <library>/boost/conversion//boost_conversion
+        [ requires cxx11_decltype ]
+        # default to all warnings on:
+        <warnings>all
+        # set warnings as errors for those compilers we know we get warning free:
+        <toolset>gcc:<cxxflags>-Wextra
+        <toolset>gcc:<cxxflags>-Wno-uninitialized
+    ;
+
+test-suite conversion
+  : [ run implicit_cast.cpp ]
+    [ compile-fail implicit_cast_fail.cpp ]
+    [ run cast_test.cpp ]
+    [ run polymorphic_cast_test.cpp : : : <library>/boost/smart_ptr//boost_smart_ptr ]
+    [ compile-fail implicit_cast_fail2.cpp ]
+  ;

test/appveyor.yml

@@ -0,0 +1,87 @@
+# Use, modification, and distribution are
+# 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)
+#
+# Copyright Antony Polukhin, 2016-2025.
+
+#
+# See https://svn.boost.org/trac/boost/wiki/TravisCoverals for description of this file
+# and how it can be used with Boost libraries.
+#
+# File revision #6
+
+init:
+    # boost-local/libs/ folder to put this library into. This may be useful, if you're for example running Travis
+    # from `Boost.DLL` repo while Boost already has `dll` and with to replace `dll` with content of`Boost.DLL`.
+    #
+    # Otherwise just leave the default value - set BOOST_LIBS_FOLDER=%APPVEYOR_PROJECT_NAME%
+    - set BOOST_LIBS_FOLDER=%APPVEYOR_PROJECT_NAME%
+
+###############################################################################################################
+# From this point and below code is same for all the Boost libs
+###############################################################################################################
+
+version: 1.84.{build}-{branch}
+ 
+# branches to build
+branches:
+  except:
+    - gh-pages
+
+skip_tags: true
+
+environment:
+  matrix:
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      TOOLSET: msvc-14.1,clang-win
+      CXXSTD: 14,17
+      ADDRMD: 32,64
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\cygwin\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\cygwin64\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\mingw\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      ADDPATH: C:\mingw-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin;
+      TOOLSET: gcc
+      CXXSTD: 03,11,14,1z
+
+before_build:
+    - set BOOST_BRANCH=develop
+    - if "%APPVEYOR_REPO_BRANCH%" == "master" set BOOST_BRANCH=master
+    - echo "Testing %APPVEYOR_PROJECT_NAME%"
+    # Cloning Boost libraries (fast nondeep cloning)
+    - set BOOST=C:/boost-local
+    - git clone -b %BOOST_BRANCH% --depth 10 https://github.com/boostorg/boost.git %BOOST%
+    - cd %BOOST%
+    - git submodule update --init --depth 10 tools/build tools/boostdep
+
+    - rm -rf %BOOST%/libs/%BOOST_LIBS_FOLDER%
+    - mv -f %APPVEYOR_BUILD_FOLDER% %BOOST%/libs/%BOOST_LIBS_FOLDER%
+    - python tools/boostdep/depinst/depinst.py --git_args "--depth 10 --jobs 2" %BOOST_LIBS_FOLDER%
+
+build_script:
+    - cmd /c bootstrap
+    - b2.exe headers
+    - cd %BOOST%/libs/%BOOST_LIBS_FOLDER%/test
+
+after_build:
+before_test:
+test_script:
+  - PATH=%ADDPATH%%PATH%
+  - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
+  - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
+  - echo "Running command ..\..\..\b2 -j3 toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release"
+  - ..\..\..\b2.exe -j3 toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release cxxflags="-DBOOST_TRAVISCI_BUILD"
+
+after_test:
+on_success:
+on_failure:
+on_finish:

test/cast_test.cpp

@@ -0,0 +1,124 @@
+//  boost utility cast test program  -----------------------------------------//
+
+//  (C) Copyright Beman Dawes, Dave Abrahams 1999. 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)
+
+//  See http://www.boost.org for most recent version including documentation.
+
+//  Revision History
+//   28 Set 04  factored out numeric_cast<> test (Fernando Cacciola)
+//   20 Jan 01  removed use of <limits> for portability to raw GCC (David Abrahams)
+//   28 Jun 00  implicit_cast removed (Beman Dawes)
+//   30 Aug 99  value_cast replaced by numeric_cast
+//    3 Aug 99  Initial Version
+
+#include <iostream>
+#include <boost/polymorphic_cast.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost;
+using std::cout;
+
+namespace
+{
+    struct Base
+    {
+        virtual char kind() { return 'B'; }
+    };
+
+    struct Base2
+    {
+        virtual char kind2() { return '2'; }
+    };
+
+    struct Derived : public Base, Base2
+    {
+        virtual char kind() { return 'D'; }
+    };
+}
+
+constexpr bool compile_time_polymorphic_cast_check() {
+#if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
+    Derived derived;
+    Base* base = &derived;
+    return polymorphic_cast<Derived*>(base) != nullptr;
+#endif
+    return true;
+}
+
+static_assert(
+    compile_time_polymorphic_cast_check(),
+    "polymorphic_cast does not work at compile time"
+);
+
+constexpr bool compile_time_polymorphic_downcast_check() {
+#if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
+    Derived derived;
+    Base* base = &derived;
+    return polymorphic_downcast<Derived*>(base) != nullptr;
+#endif
+    return true;
+}
+
+static_assert(
+    compile_time_polymorphic_downcast_check(),
+    "polymorphic_downcast does not work at compile time"
+);
+
+constexpr bool compile_time_polymorphic_downcast2_check() {
+#if defined(__cpp_constexpr) && __cpp_constexpr >= 201907L
+    Derived derived;
+    Base& base = derived;
+    Derived& derived_again = polymorphic_downcast<Derived&>(base);
+    (void)derived_again;
+#endif
+    return true;
+}
+
+static_assert(
+    compile_time_polymorphic_downcast2_check(),
+    "polymorphic_downcast does not work at compile time"
+);
+
+int main( int argc, char * argv[] )
+{
+#   ifdef NDEBUG
+        cout << "NDEBUG is defined\n";
+#   else
+        cout << "NDEBUG is not defined\n";
+#   endif
+
+    cout << "\nBeginning tests...\n";
+
+//  test polymorphic_cast  ---------------------------------------------------//
+
+    //  tests which should succeed
+    Derived derived_instance;
+    Base * base = &derived_instance;
+    Derived * derived = polymorphic_downcast<Derived*>( base );  // downcast
+    BOOST_TEST( derived->kind() == 'D' );
+
+    derived = polymorphic_cast<Derived*>( base ); // downcast, throw on error
+    BOOST_TEST( derived->kind() == 'D' );
+
+    Base2 *   base2 =  polymorphic_cast<Base2*>( base ); // crosscast
+    BOOST_TEST( base2->kind2() == '2' );
+
+     //  tests which should result in errors being detected
+    Base base_instance;
+    base = &base_instance;
+
+    if ( argc > 1 && *argv[1] == '1' )
+        { derived = polymorphic_downcast<Derived*>( base ); } // #1 assert failure
+
+    bool caught_exception = false;
+    try { derived = polymorphic_cast<Derived*>( base ); }
+    catch (const std::bad_cast&)
+        { cout<<"caught bad_cast\n"; caught_exception = true; }
+    BOOST_TEST( caught_exception );
+    //  the following is just so generated code can be inspected
+    BOOST_TEST( derived->kind() != 'B' );
+
+    return boost::report_errors();
+}   // main

test/implicit_cast.cpp

@@ -0,0 +1,43 @@
+// Copyright David Abrahams 2003.
+// 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/implicit_cast.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/type.hpp>
+
+using boost::implicit_cast;
+using boost::type;
+
+template <class T>
+type<T> check_return(T) { return type<T>(); }
+
+struct foo
+{
+    foo(char const*) {}
+    operator long() const { return 0; }
+};
+
+using long_type = type<long>;
+using foo_type = type<foo>;
+
+int main()
+{
+    type<long> x = check_return(boost::implicit_cast<long>(1));
+    BOOST_TEST(boost::implicit_cast<long>(1) == 1L);
+
+    type<foo> f = check_return(boost::implicit_cast<foo>("hello"));
+    type<long> z = check_return(boost::implicit_cast<long>(foo("hello")));
+
+    // warning suppression:
+    (void)x;
+    (void)f;
+    (void)z;
+
+
+    constexpr long value = boost::implicit_cast<long>(42);
+    BOOST_TEST(value == 42L);
+
+    return boost::report_errors();
+}

test/implicit_cast_fail.cpp

@@ -0,0 +1,20 @@
+// Copyright David Abrahams 2003.
+// 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/implicit_cast.hpp>
+
+using boost::implicit_cast;
+
+struct foo
+{
+    explicit foo(char const*) {}
+};
+
+int main()
+{
+    foo x = implicit_cast<foo>("foobar");
+    (void)x;            // warning suppression.
+    return 0;
+}

test/implicit_cast_fail2.cpp

@@ -0,0 +1,19 @@
+//
+// Test that implicit_cast requires a template argument
+//
+// Copyright 2014 Peter Dimov
+//
+// 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/implicit_cast.hpp>
+
+int main()
+{
+    int x = boost::implicit_cast( 1 );
+    (void)x;
+
+    return 0;
+}

test/polymorphic_cast_test.cpp

@@ -0,0 +1,383 @@
+//
+// Test boost::polymorphic_cast, boost::polymorphic_downcast and 
+// boost::polymorphic_pointer_cast, boost::polymorphic_pointer_downcast
+//
+// Copyright 1999 Beman Dawes
+// Copyright 1999 Dave Abrahams
+// Copyright 2014 Peter Dimov
+// Copyright 2014 Boris Rasin, Antony Polukhin
+// Copyright 2023 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
+//
+
+#define BOOST_ENABLE_ASSERT_HANDLER
+#include <boost/polymorphic_cast.hpp>
+#include <boost/polymorphic_pointer_cast.hpp>
+#include <boost/smart_ptr/shared_ptr.hpp>
+#include <boost/smart_ptr/intrusive_ptr.hpp>
+#include <boost/smart_ptr/intrusive_ref_counter.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <string>
+#include <memory>
+
+static bool expect_assertion = false;
+static int assertion_failed_count = 0;
+
+//assertion handler throws it to exit like assert, but to be able to catch it and stop
+//usage: BOOST_TEST_THROWS( function_with_assert(), expected_assertion );
+struct expected_assertion {};
+
+// BOOST_ASSERT custom handler
+void boost::assertion_failed( char const * expr, char const * function, char const * file, long line )
+{
+    if( expect_assertion )
+    {
+        ++assertion_failed_count;
+        throw expected_assertion();
+    }
+    else
+    {
+        BOOST_ERROR( "unexpected assertion" );
+
+        BOOST_LIGHTWEIGHT_TEST_OSTREAM
+          << file << "(" << line << "): assertion '" << expr << "' failed in function '"
+          << function << "'" << std::endl;
+    }
+}
+
+//
+
+struct Base : boost::intrusive_ref_counter<Base>
+{
+    virtual ~Base() {}
+    virtual std::string kind() { return "Base"; }
+};
+
+struct Base2
+{
+    virtual ~Base2() {}
+    virtual std::string kind2() { return "Base2"; }
+};
+
+struct Derived : public Base, Base2
+{
+    virtual std::string kind() { return "Derived"; }
+};
+
+static void test_polymorphic_cast()
+{
+    Base * base = new Derived;
+
+    Derived * derived;
+    
+    try
+    {
+        derived = boost::polymorphic_cast<Derived*>( base );
+
+        BOOST_TEST( derived != 0 );
+
+        if( derived != 0 )
+        {
+            BOOST_TEST_EQ( derived->kind(), "Derived" );
+        }
+    }
+    catch( std::bad_cast const& )
+    {
+        BOOST_ERROR( "boost::polymorphic_cast<Derived*>( base ) threw std::bad_cast" );
+    }
+
+    Base2 * base2;
+
+    try
+    {
+        base2 = boost::polymorphic_cast<Base2*>( base ); // crosscast
+
+        BOOST_TEST( base2 != 0 );
+
+        if( base2 != 0 )
+        {
+            BOOST_TEST_EQ( base2->kind2(), "Base2" );
+        }
+    }
+    catch( std::bad_cast const& )
+    {
+        BOOST_ERROR( "boost::polymorphic_cast<Base2*>( base ) threw std::bad_cast" );
+    }
+
+    delete base;
+}
+
+static void test_polymorphic_pointer_cast()
+{
+    Base * base = new Derived;
+
+    Derived * derived;
+
+    try
+    {
+        derived = boost::polymorphic_pointer_cast<Derived>( base );
+
+        BOOST_TEST( derived != 0 );
+
+        if( derived != 0 )
+        {
+            BOOST_TEST_EQ( derived->kind(), "Derived" );
+        }
+    }
+    catch( std::bad_cast const& )
+    {
+        BOOST_ERROR( "boost::polymorphic_pointer_cast<Derived>( base ) threw std::bad_cast" );
+    }
+
+    Base2 * base2;
+
+    try
+    {
+        base2 = boost::polymorphic_pointer_cast<Base2>( base ); // crosscast
+
+        BOOST_TEST( base2 != 0 );
+
+        if( base2 != 0 )
+        {
+            BOOST_TEST_EQ( base2->kind2(), "Base2" );
+        }
+    }
+    catch( std::bad_cast const& )
+    {
+        BOOST_ERROR( "boost::polymorphic_pointer_cast<Base2>( base ) threw std::bad_cast" );
+    }
+
+    boost::shared_ptr<Base> sp_base( base );
+    boost::shared_ptr<Base2> sp_base2;
+    try
+    {
+        sp_base2 = boost::polymorphic_pointer_cast<Base2>( sp_base ); // crosscast
+
+        BOOST_TEST( sp_base2 != 0 );
+
+        if( sp_base2 != 0 )
+        {
+            BOOST_TEST_EQ( sp_base2->kind2(), "Base2" );
+        }
+    }
+    catch( std::bad_cast const& )
+    {
+        BOOST_ERROR( "boost::polymorphic_pointer_cast<Base2>( sp_base ) threw std::bad_cast" );
+    }
+
+    // we do not `delete base;` because sahred_ptr is holding base
+}
+
+static void test_polymorphic_downcast()
+{
+    Base *base_pointer = new Derived;
+
+    // test raw pointer cast
+    Derived *derived_pointer = boost::polymorphic_downcast<Derived *>(base_pointer);
+
+    BOOST_TEST(derived_pointer != 0);
+
+    if (derived_pointer != 0)
+    {
+        BOOST_TEST_EQ(derived_pointer->kind(), "Derived");
+    }
+
+    // test reference cast
+    Derived& derived_ref = boost::polymorphic_downcast<Derived&>(*base_pointer);
+    BOOST_TEST_EQ(derived_ref.kind(), "Derived");
+
+    delete base_pointer;
+}
+
+static void test_polymorphic_pointer_downcast_builtin()
+{
+    Base * base = new Derived;
+
+    Derived * derived = boost::polymorphic_pointer_downcast<Derived>( base );
+
+    BOOST_TEST( derived != 0 );
+
+    if( derived != 0 )
+    {
+        BOOST_TEST_EQ( derived->kind(), "Derived" );
+    }
+
+    // polymorphic_pointer_downcast can't do crosscasts
+
+    delete base;
+}
+
+static void test_polymorphic_pointer_downcast_boost_shared()
+{
+    boost::shared_ptr<Base> base (new Derived);
+
+    boost::shared_ptr<Derived> derived = boost::polymorphic_pointer_downcast<Derived>( base );
+
+    BOOST_TEST( derived != 0 );
+
+    if( derived != 0 )
+    {
+        BOOST_TEST_EQ( derived->kind(), "Derived" );
+    }
+}
+
+static void test_polymorphic_pointer_downcast_intrusive()
+{
+    boost::intrusive_ptr<Base> base (new Derived);
+
+    boost::intrusive_ptr<Derived> derived = boost::polymorphic_pointer_downcast<Derived>( base );
+
+    BOOST_TEST( derived != 0 );
+
+    if( derived != 0 )
+    {
+        BOOST_TEST_EQ( derived->kind(), "Derived" );
+    }
+}
+
+static void test_polymorphic_pointer_downcast_std_shared()
+{
+    std::shared_ptr<Base> base (new Derived);
+
+    std::shared_ptr<Derived> derived = boost::polymorphic_pointer_downcast<Derived>( base );
+
+    BOOST_TEST( derived != 0 );
+
+    if( derived != 0 )
+    {
+        BOOST_TEST_EQ( derived->kind(), "Derived" );
+    }
+}
+
+static void test_polymorphic_cast_fail()
+{
+    Base * base = new Base;
+
+    BOOST_TEST_THROWS( boost::polymorphic_cast<Derived*>( base ), std::bad_cast );
+
+    delete base;
+}
+
+static void test_polymorphic_pointer_cast_fail()
+{
+    Base * base = new Base;
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_cast<Derived>( base ), std::bad_cast );
+    delete base;
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_cast<Derived>( boost::shared_ptr<Base>(new Base) ), std::bad_cast );
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_cast<Derived>( std::shared_ptr<Base>(new Base) ), std::bad_cast );
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_cast<Derived>( boost::intrusive_ptr<Base>(new Base) ), std::bad_cast );
+}
+
+static void test_polymorphic_downcast_fail()
+{
+    Base * base_pointer = new Base;
+
+    {
+        // test raw pointer cast
+
+        int old_count = assertion_failed_count;
+        expect_assertion = true;
+
+        BOOST_TEST_THROWS(boost::polymorphic_downcast<Derived *>(base_pointer), expected_assertion); // should assert
+
+        BOOST_TEST_EQ(assertion_failed_count, old_count + 1);
+        expect_assertion = false;
+    }
+    {
+        // test reference cast
+
+        int old_count = assertion_failed_count;
+        expect_assertion = true;
+
+        BOOST_TEST_THROWS(boost::polymorphic_downcast<Derived &>(*base_pointer), expected_assertion); // should assert
+
+        BOOST_TEST_EQ(assertion_failed_count, old_count + 1);
+        expect_assertion = false;
+    }
+
+    delete base_pointer;
+}
+
+static void test_polymorphic_pointer_downcast_builtin_fail()
+{
+    Base * base = new Base;
+
+    int old_count = assertion_failed_count;
+    expect_assertion = true;
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_downcast<Derived>( base ), expected_assertion ); // should assert
+
+    BOOST_TEST_EQ( assertion_failed_count, old_count + 1 );
+    expect_assertion = false;
+
+    delete base;
+}
+
+static void test_polymorphic_pointer_downcast_boost_shared_fail()
+{
+    boost::shared_ptr<Base> base (new Base);
+
+    int old_count = assertion_failed_count;
+    expect_assertion = true;
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_downcast<Derived>( base ), expected_assertion ); // should assert
+
+    BOOST_TEST_EQ( assertion_failed_count, old_count + 1 );
+    expect_assertion = false;
+}
+
+
+static void test_polymorphic_pointer_downcast_std_shared_fail()
+{
+    std::shared_ptr<Base> base (new Base);
+
+    int old_count = assertion_failed_count;
+    expect_assertion = true;
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_downcast<Derived>( base ), expected_assertion ); // should assert
+
+    BOOST_TEST_EQ( assertion_failed_count, old_count + 1 );
+    expect_assertion = false;
+}
+
+
+static void test_polymorphic_pointer_downcast_intrusive_fail()
+{
+    boost::intrusive_ptr<Base> base (new Base);
+
+    int old_count = assertion_failed_count;
+    expect_assertion = true;
+
+    BOOST_TEST_THROWS( boost::polymorphic_pointer_downcast<Derived>( base ), expected_assertion); // should assert
+
+    BOOST_TEST_EQ( assertion_failed_count, old_count + 1 );
+    expect_assertion = false;
+}
+
+int main()
+{
+    test_polymorphic_cast();
+    test_polymorphic_pointer_cast();
+    test_polymorphic_downcast();
+    test_polymorphic_pointer_downcast_builtin();
+    test_polymorphic_pointer_downcast_boost_shared();
+    test_polymorphic_pointer_downcast_intrusive();
+    test_polymorphic_cast_fail();
+    test_polymorphic_pointer_cast_fail();
+    test_polymorphic_downcast_fail();
+    test_polymorphic_pointer_downcast_builtin_fail();
+    test_polymorphic_pointer_downcast_boost_shared_fail();
+    test_polymorphic_pointer_downcast_intrusive_fail();
+
+    test_polymorphic_pointer_downcast_std_shared();
+    test_polymorphic_pointer_downcast_std_shared_fail();
+
+
+    return boost::report_errors();
+}