Boost C++ Libraries

Known Issues These are patches from library authors which were found too late to be fixed in the release. Boost.Build silently skips installation of library headers and binaries ... [More] in some cases, see #104. Fixed in PR#113, patch. New Libraries No new libraries. Updated Libraries Asio: Added an io_uring backend that may optionally be used for all I/O objects, including sockets, timers, and posix descriptors. Added support for files, with new new classes for stream-oriented and random-access files. This feature currently supports I/O completion ports on Windows, and io_uring on Linux. Added support for portable pipes on POSIX and Windows (when I/O completion ports are available). Added support for registered buffers, which are optimised when using the io_uring backend. Added experimental support for channels, that may be used to send and queue completions as messages. Implemented improvements to experimental::coro. Disabled aligned_alloc on clang when using an MSVC runtime. Changed to use a faster implementation for ip::network_v4::canonical(). Added template specialisations for common uses to improve compile time. Reduced the size of io_context executors to a single pointer. Increased the small object buffer size for execution::any_executor and any_io_executor. Fixed multi-signature handling when variadic templates are disabled. Fixed compatibility with new versions of gcc and clang. Fixed compilation on Solaris. Fixed defence against Qt-defined macros when building with MSVC. Improved error messages emitted by ssl facilities. Fixed bind_executor compatibility with completion tokens. Fixed build errors when BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT is defined. Added missing move assignment operator to awaitable<>. Fixed an access violation when using coroutines with MSVC, due to incorrect alignment of allocated memory. Fixed a cleanup issue in experimental::parallel_group that occured when the execution context was shut down with parallel operations still pending. Added clarifications to the documentation on concurrency hints. Added documentation on error handling techniques for C++20 coroutines. Fixed various warnings. Consult the Revision History for further details. Assert: Added source_location::to_string. Atomic: Use process-local futex operations on Android for non-IPC waiting and notifying operations. Added support for Linux targets that only define SYS_futex_time64 syscall, such as riscv32. Added a workaround for incorrect result of std::alignment_of on clang 8 for 64-bit types on 32-bit x86 targets. Added a ulock backend for waiting and notifying operations on Darwin systems since Mac OS 10.12, iOS 10.0, tvOS 10.0 or watchOS 3.0. On Windows, corrected discrepancy between atomic-type::always_has_native_wait_notify and the corresponding capability macros when targeting Windows 8 or later. The library will now directly use WaitOnAddress and related APIs from public headers and therefore require user to link with synchronization.lib if the user requires Windows 8 or later by defining BOOST_USE_WINAPI_VERSION, _WIN32_WINNT or similar macros. The library is linked automatically on compilers that support auto-linking (e.g. MSVC). Added support for types with padding bits, except unions, on compilers that provide a way to clear the padding bits. This feature is supported by gcc 11 and MSVC 14.2 (compiler version 19.27) and newer, as well as other compilers supporting similar intrinsics. On compilers that don't allow to clear the padding bits, types with padding are still generally not supported with the exception of 80-bit long double on x86 targets. A new BOOST_ATOMIC_NO_CLEAR_PADDING capability macro is defined to indicate when clearing the padding is not supported. Initializing constructors of atomic_ref and ipc_atomic_ref no longer use atomic instructions to clear the padding bits in the referenced object. This reduces the cost of the atomic reference construction. Initializing constructors of atomic and ipc_atomic are now constexpr for enums, classes and floating point types. For classes and floating point types, the constructors are constexpr if the compiler supports constexpr std::bit_cast, the type has no padding bytes and no padding is required to implement native atomic operations. In accordance with C++20, default constructors of atomic and ipc_atomic now perform value initialization of the contained object. For types without a user-defined default constructor, this means the default-constructed atomic will be zero-initialized. Added a workaround for compilation error on AIX caused by the assembler tool not supporting numeric labels. (PR#50) Added a workaround for compilation error with Visual Studio 2015 prior to Update 3. (#52) See changelog for more details. Beast: This maintenance update brings minor bug fixes and updated CI reporting. Fixed security vulnerability CVE-2016-9840 in zlib implementation. Fixed WebSocket permessage_deflate implementation. This should result in an increase in compression performance when using Beast WebSockets. Removed the test stream and test framework's dependency on RTTI. You can now use our handy test stream to check your embedded asynchronous communications code! We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Core: Added a generic implementation to <boost/core/cmath.hpp>, enabled when BOOST_CORE_USE_GENERIC_CMATH is defined or when the platform does not provide the necessary facilities in <cmath>. Added boost::core::type_name, a utility function that returns the name of a type as a string. Added boost::span, a C++11 implementation of C++20's std::span (Glen Fernandes). Describe: Added has_describe_enumerators, has_describe_bases, has_describe_members. Added enum_to_string, enum_from_string. Added relational and stream insertion operators. Added descriptor_by_name, descriptor_by_pointer. DLL: Fixed missing #include, thanks to Denis Blank (PR#54) Dropped TravisCI in favor of GithubAction CI Filesystem: v4: path::filename and path::iterator no longer return an implicit trailing dot (".") element if the path ends with a directory separator. Instead, an empty path is returned, similar to C++17 std::filesystem. This also affects other methods that are defined in terms of iterators or filename, such as path::stem, path::compare or lexicographical_compare. For example, path("a/b/") == path("a/b/.") no longer holds true. (#193) v4: path::lexically_normal no longer produce a trailing dot (".") element and omits a directory separator after a trailing dot-dot ("..") element in the normalized paths. v4: path append operations now consider root name and root directory in the appended path. If the appended path is absolute, or root name is present and differs from the source path, the resulting path is equivalent to the appended path. If root directory is present, the result is the root directory and relative path rebased on top of the root name of the source path. Otherwise, the behavior is similar to v3. (#214) path::lexically_normal now converts directory separators to preferred separators in the root name of the normalized paths. Optimized overloads of path::assign, path::append, path::concat and the corresponding operators to avoid unnecessary path copying and reduce the amount of code redundancy. On POSIX systems, fixed absolute(p, base) returning a path with root name base.root_name() if p starts with a root directory. In such a case p is already an absolute path and should be returned as is. create_directories no longer reports an error if the input path consists entirely of dot (".") and dot-dot ("..") elements. The implementation is no longer using recursion internally and therefore is better protected from stack overflow on extremely long paths. On Windows, remove now supports deleting read-only files. The operation will attempt to reset the read-only attribute prior to removal. Note that this introduces a possibility of the read-only attribute being left unset, if the operation fails and the original value of the attribute fails to be restored. This also affects remove_all. (#216) remove_all now returns static_cast< uintmax_t >(-1) in case of error, similar to C++17 std::filesystem. Fixed a linking error about unresolved references to Boost.ContainerHash functions when user's code includes boost/filesystem/path.hpp but not boost/container_hash/hash.hpp and the compiler is set to preserve unused inline functions. (#215) Added a workaround for MSVC and compatible compilers eliminating path globals cleanup in release builds. This could lead to a memory leak if Boost.Filesystem shared library was repeatedly loaded and unloaded in the process. (#217) Geometry: Improvements PR#894 Optimization and refactoring of rtree queries. PR#913 DynamicGeometry and GeometryCollection support in various algorithms (undocumented for now). PR#922 DynamicGeometry and GeometryCollection support in distance (undocumented for now). Solved issues #867 Poor performance of rtree query iterator with nearest predicate for big k. #870 Compilation error in boost::geometry::self_turns. #896 Assertion failure in get_turns with BOOST_GEOMETRY_NO_ROBUSTNESS. Bugfixes PR#906 Invalid result of buffer on macos-11 with clang-12. PR#921 Compilation errors with c++20 (various compilers) and gcc-5. Various fixes in set operations and buffer. JSON: Standalone mode of the library is deprecated. Allow external libraries to forward declare value_to and value_from. Fixed signed integer overflow in number parsing. Add support for /Zc:implicitNoexcept- on MSVC. Lambda2: Added special cases in operator<< and operator>> when the first argument is a stream, to allow std::cout << _1. Added operator->*. Added first, second. Log: General changes: Updated detection of std::codecvt specializations for char16_t and char32_t for compatibility with C++17 and later. (PR#159) Added support for C++17 std::byte type to receive methods of the inter-process message queue. On Windows, when building the library for Windows 8 or later, the library will use nt62 tag in the version namespace to denote the target OS ABI. For example, the version namespace could be named as v2_mt_nt62. This name will be part of all symbols exported by the library. Use the BOOST_USE_WINAPI_VERSION macro consistenly when building Boost and your code to request the minimum target Windows version. Improved performance of SSSE3 and AVX2 implementations of the dump stream manipulator. Added support for CMake build system. Only library build is supported at this moment, Boost.Build is still used for running tests. Bug fixes: Fixed a race condition on POSIX systems in reliable_message_queue::open_or_create or the equivalent constructor. Multiple threads or processes calling open_or_create concurrently with sending or receiving messages from the same queue could end up corrupting the queue contents and potentially crashing the process. (#162) Added a workaround for b2 install failing on Windows because of missing boost_log_setup library if BOOST_LOG_WITHOUT_SETTINGS_PARSERS is defined. (#164) See changelog for more details. Math: Add support for cubic roots. Add support for constexpr versions of various standard library math routines. Add support for Bezier polynomials. Improve worst-case tanh-sinh integration performance. Disable inadvertant use of integral types in integration routines. Minor update for erf approximations when the result is with 2ulp of 1. Allow Bernoulli code to be used on platforms with no atomic integers. Improve the mode of the non-central Chi Squared distribution. Improve certain edge cases for complex-valued elementary functions, see #507. Multi-index Containers: Added contains to key-based indices (issue #35). Added merge operations to key-based indices. The functionality goes beyond the standard specification for (unordered) associative containers in a number of ways, most notably: The source index can be of any type, including non key-based indices. Partial merge is provided: for instance, x.merge(y,first,last) merges only the elements of y within [first,last). Previous versions of splice for sequenced and random access indices were destructive, i.e. elements were copy-inserted into the destination and then erased from the source. Now, splice is based on node transfer much as merge in key-based indices, and has been similarly extended to accept source indices of any type: in fact, splice can be regarded as a frontend to the same functionality provided by merge in key-based indices. For reasons of backwards compatibility, the destructive behavior of splice has been retained in the case that the source and destination containers have unequal allocators. The fact has been documented that index iterator types do only depend on node_type and the position of the index in its multi_index_container, (except for hashed indices, where uniqueness/non-uniqueness is also a dependency). This has implications on the validity of iterators to elements transferred by merge or splice. This property is a variant of what has been called SCARY iterators in the C++ standard mailing lists. SCARYness is currently (August 2021) not mandated for standard containers. Iterator SCARYness is now also preserved in safe mode. Multiprecision: Rework rational_adaptor to remove dependency on Boost.Rational and improve performance. Fix issue with type_traits and clang, see #383. Fixed buggy Lehmer's GCD routine, see #370. Fix mpc_complex constructors so that lossy conversions are explicit, see #363. Correct miscellaneous configuration issues (Intel intrinsic usage and Apple clang). Correct some iostream operators for unsigned char types. Correct mpq_rational conversions to integer types, see #342. PFR: Added missing #include <memory> for inclusion of std::addressof Fixed -Wzero-length-array warning when dealing with empty aggregates Fixed compilation on msvc compilers <= 1920 (thanks to Alexey Romanov aka @alexey-romanov) Added basic CMakeLists.txt support (thanks to @pdimov aka Peter Dimov) Multiple improvements for docs, including links to https://github.com/apolukhin/pfr_non_boost Added misc/strip_boost_namespace.sh script to remove boost:: and BOOST_ prefixes Predef: Version 1.13.1 Fix spelling of "epoch". Add missing parenthesis in sparc.h (from tkoecker). Update documentation to use Rouge code styling and Amber general style. Regex: Breaking Change: Change \B to be the opposite of \b as per Perl behaviour. Change w32_regex_traits.hpp so that windows.h is no longer included. Fxed fuzzing related issues #151, #152, #153, #156. System: Added support for source locations to error_code. Added error_code::to_string, error_condition::to_string, error_code::what. system_error::what() now contains the source location, if present. Added result<T, E = error_code>, a class holding either a value or an error, defined in <boost/system/result.hpp>. Utility: Library documentation converted to QuickBook (thanks to Alan de Freitas, PR#79). Variant2: Added <boost/variant2.hpp>. Added unsafe_get<I>. Added visit_by_index. Added operator<<. Updated Tools Build: Includes release of B2 version 4.7.2. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

Known Issues These are patches from library authors which were found too late to be fixed in the release. Boost.Build silently skips installation of library headers and binaries ... [More] in some cases, see #104. Fixed in PR#113, patch. New Libraries No new libraries. Updated Libraries Asio: Added an io_uring backend that may optionally be used for all I/O objects, including sockets, timers, and posix descriptors. Added support for files, with new new classes for stream-oriented and random-access files. This feature currently supports I/O completion ports on Windows, and io_uring on Linux. Added support for portable pipes on POSIX and Windows (when I/O completion ports are available). Added support for registered buffers, which are optimised when using the io_uring backend. Added experimental support for channels, that may be used to send and queue completions as messages. Implemented improvements to experimental::coro. Disabled aligned_alloc on clang when using an MSVC runtime. Changed to use a faster implementation for ip::network_v4::canonical(). Added template specialisations for common uses to improve compile time. Reduced the size of io_context executors to a single pointer. Increased the small object buffer size for execution::any_executor and any_io_executor. Fixed multi-signature handling when variadic templates are disabled. Fixed compatibility with new versions of gcc and clang. Fixed compilation on Solaris. Fixed defence against Qt-defined macros when building with MSVC. Improved error messages emitted by ssl facilities. Fixed bind_executor compatibility with completion tokens. Fixed build errors when BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT is defined. Added missing move assignment operator to awaitable<>. Fixed an access violation when using coroutines with MSVC, due to incorrect alignment of allocated memory. Fixed a cleanup issue in experimental::parallel_group that occured when the execution context was shut down with parallel operations still pending. Added clarifications to the documentation on concurrency hints. Added documentation on error handling techniques for C++20 coroutines. Fixed various warnings. Consult the Revision History for further details. Assert: Added source_location::to_string. Atomic: Use process-local futex operations on Android for non-IPC waiting and notifying operations. Added support for Linux targets that only define SYS_futex_time64 syscall, such as riscv32. Added a workaround for incorrect result of std::alignment_of on clang 8 for 64-bit types on 32-bit x86 targets. Added a ulock backend for waiting and notifying operations on Darwin systems since Mac OS 10.12, iOS 10.0, tvOS 10.0 or watchOS 3.0. On Windows, corrected discrepancy between atomic-type::always_has_native_wait_notify and the corresponding capability macros when targeting Windows 8 or later. The library will now directly use WaitOnAddress and related APIs from public headers and therefore require user to link with synchronization.lib if the user requires Windows 8 or later by defining BOOST_USE_WINAPI_VERSION, _WIN32_WINNT or similar macros. The library is linked automatically on compilers that support auto-linking (e.g. MSVC). Added support for types with padding bits, except unions, on compilers that provide a way to clear the padding bits. This feature is supported by gcc 11 and MSVC 14.2 (compiler version 19.27) and newer, as well as other compilers supporting similar intrinsics. On compilers that don't allow to clear the padding bits, types with padding are still generally not supported with the exception of 80-bit long double on x86 targets. A new BOOST_ATOMIC_NO_CLEAR_PADDING capability macro is defined to indicate when clearing the padding is not supported. Initializing constructors of atomic_ref and ipc_atomic_ref no longer use atomic instructions to clear the padding bits in the referenced object. This reduces the cost of the atomic reference construction. Initializing constructors of atomic and ipc_atomic are now constexpr for enums, classes and floating point types. For classes and floating point types, the constructors are constexpr if the compiler supports constexpr std::bit_cast, the type has no padding bytes and no padding is required to implement native atomic operations. In accordance with C++20, default constructors of atomic and ipc_atomic now perform value initialization of the contained object. For types without a user-defined default constructor, this means the default-constructed atomic will be zero-initialized. Added a workaround for compilation error on AIX caused by the assembler tool not supporting numeric labels. (PR#50) Added a workaround for compilation error with Visual Studio 2015 prior to Update 3. (#52) See changelog for more details. Beast: This maintenance update brings minor bug fixes and updated CI reporting. Fixed security vulnerability CVE-2016-9840 in zlib implementation. Fixed WebSocket permessage_deflate implementation. This should result in an increase in compression performance when using Beast WebSockets. Removed the test stream and test framework's dependency on RTTI. You can now use our handy test stream to check your embedded asynchronous communications code! We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Core: Added a generic implementation to <boost/core/cmath.hpp>, enabled when BOOST_CORE_USE_GENERIC_CMATH is defined or when the platform does not provide the necessary facilities in <cmath>. Added boost::core::type_name, a utility function that returns the name of a type as a string. Added boost::span, a C++11 implementation of C++20's std::span (Glen Fernandes). Describe: Added has_describe_enumerators, has_describe_bases, has_describe_members. Added enum_to_string, enum_from_string. Added relational and stream insertion operators. Added descriptor_by_name, descriptor_by_pointer. DLL: Fixed missing #include, thanks to Denis Blank (PR#54) Dropped TravisCI in favor of GithubAction CI Filesystem: v4: path::filename and path::iterator no longer return an implicit trailing dot (".") element if the path ends with a directory separator. Instead, an empty path is returned, similar to C++17 std::filesystem. This also affects other methods that are defined in terms of iterators or filename, such as path::stem, path::compare or lexicographical_compare. For example, path("a/b/") == path("a/b/.") no longer holds true. (#193) v4: path::lexically_normal no longer produce a trailing dot (".") element and omits a directory separator after a trailing dot-dot ("..") element in the normalized paths. v4: path append operations now consider root name and root directory in the appended path. If the appended path is absolute, or root name is present and differs from the source path, the resulting path is equivalent to the appended path. If root directory is present, the result is the root directory and relative path rebased on top of the root name of the source path. Otherwise, the behavior is similar to v3. (#214) path::lexically_normal now converts directory separators to preferred separators in the root name of the normalized paths. Optimized overloads of path::assign, path::append, path::concat and the corresponding operators to avoid unnecessary path copying and reduce the amount of code redundancy. On POSIX systems, fixed absolute(p, base) returning a path with root name base.root_name() if p starts with a root directory. In such a case p is already an absolute path and should be returned as is. create_directories no longer reports an error if the input path consists entirely of dot (".") and dot-dot ("..") elements. The implementation is no longer using recursion internally and therefore is better protected from stack overflow on extremely long paths. On Windows, remove now supports deleting read-only files. The operation will attempt to reset the read-only attribute prior to removal. Note that this introduces a possibility of the read-only attribute being left unset, if the operation fails and the original value of the attribute fails to be restored. This also affects remove_all. (#216) remove_all now returns static_cast< uintmax_t >(-1) in case of error, similar to C++17 std::filesystem. Fixed a linking error about unresolved references to Boost.ContainerHash functions when user's code includes boost/filesystem/path.hpp but not boost/container_hash/hash.hpp and the compiler is set to preserve unused inline functions. (#215) Added a workaround for MSVC and compatible compilers eliminating path globals cleanup in release builds. This could lead to a memory leak if Boost.Filesystem shared library was repeatedly loaded and unloaded in the process. (#217) Geometry: Improvements PR#894 Optimization and refactoring of rtree queries. PR#913 DynamicGeometry and GeometryCollection support in various algorithms (undocumented for now). PR#922 DynamicGeometry and GeometryCollection support in distance (undocumented for now). Solved issues #867 Poor performance of rtree query iterator with nearest predicate for big k. #870 Compilation error in boost::geometry::self_turns. #896 Assertion failure in get_turns with BOOST_GEOMETRY_NO_ROBUSTNESS. Bugfixes PR#906 Invalid result of buffer on macos-11 with clang-12. PR#921 Compilation errors with c++20 (various compilers) and gcc-5. Various fixes in set operations and buffer. JSON: Standalone mode of the library is deprecated. Allow external libraries to forward declare value_to and value_from. Fixed signed integer overflow in number parsing. Add support for /Zc:implicitNoexcept- on MSVC. Lambda2: Added special cases in operator<< and operator>> when the first argument is a stream, to allow std::cout << _1. Added operator->*. Added first, second. Log: General changes: Updated detection of std::codecvt specializations for char16_t and char32_t for compatibility with C++17 and later. (PR#159) Added support for C++17 std::byte type to receive methods of the inter-process message queue. On Windows, when building the library for Windows 8 or later, the library will use nt62 tag in the version namespace to denote the target OS ABI. For example, the version namespace could be named as v2_mt_nt62. This name will be part of all symbols exported by the library. Use the BOOST_USE_WINAPI_VERSION macro consistenly when building Boost and your code to request the minimum target Windows version. Improved performance of SSSE3 and AVX2 implementations of the dump stream manipulator. Added support for CMake build system. Only library build is supported at this moment, Boost.Build is still used for running tests. Bug fixes: Fixed a race condition on POSIX systems in reliable_message_queue::open_or_create or the equivalent constructor. Multiple threads or processes calling open_or_create concurrently with sending or receiving messages from the same queue could end up corrupting the queue contents and potentially crashing the process. (#162) Added a workaround for b2 install failing on Windows because of missing boost_log_setup library if BOOST_LOG_WITHOUT_SETTINGS_PARSERS is defined. (#164) See changelog for more details. Math: Add support for cubic roots. Add support for constexpr versions of various standard library math routines. Add support for Bezier polynomials. Improve worst-case tanh-sinh integration performance. Disable inadvertant use of integral types in integration routines. Minor update for erf approximations when the result is with 2ulp of 1. Allow Bernoulli code to be used on platforms with no atomic integers. Improve the mode of the non-central Chi Squared distribution. Improve certain edge cases for complex-valued elementary functions, see #507. Multi-index Containers: Added contains to key-based indices (issue #35). Added merge operations to key-based indices. The functionality goes beyond the standard specification for (unordered) associative containers in a number of ways, most notably: The source index can be of any type, including non key-based indices. Partial merge is provided: for instance, x.merge(y,first,last) merges only the elements of y within [first,last). Previous versions of splice for sequenced and random access indices were destructive, i.e. elements were copy-inserted into the destination and then erased from the source. Now, splice is based on node transfer much as merge in key-based indices, and has been similarly extended to accept source indices of any type: in fact, splice can be regarded as a frontend to the same functionality provided by merge in key-based indices. For reasons of backwards compatibility, the destructive behavior of splice has been retained in the case that the source and destination containers have unequal allocators. The fact has been documented that index iterator types do only depend on node_type and the position of the index in its multi_index_container, (except for hashed indices, where uniqueness/non-uniqueness is also a dependency). This has implications on the validity of iterators to elements transferred by merge or splice. This property is a variant of what has been called SCARY iterators in the C++ standard mailing lists. SCARYness is currently (August 2021) not mandated for standard containers. Iterator SCARYness is now also preserved in safe mode. Multiprecision: Rework rational_adaptor to remove dependency on Boost.Rational and improve performance. Fix issue with type_traits and clang, see #383. Fixed buggy Lehmer's GCD routine, see #370. Fix mpc_complex constructors so that lossy conversions are explicit, see #363. Correct miscellaneous configuration issues (Intel intrinsic usage and Apple clang). Correct some iostream operators for unsigned char types. Correct mpq_rational conversions to integer types, see #342. PFR: Added missing #include <memory> for inclusion of std::addressof Fixed -Wzero-length-array warning when dealing with empty aggregates Fixed compilation on msvc compilers <= 1920 (thanks to Alexey Romanov aka @alexey-romanov) Added basic CMakeLists.txt support (thanks to @pdimov aka Peter Dimov) Multiple improvements for docs, including links to https://github.com/apolukhin/pfr_non_boost Added misc/strip_boost_namespace.sh script to remove boost:: and BOOST_ prefixes Predef: Version 1.13.1 Fix spelling of "epoch". Add missing parenthesis in sparc.h (from tkoecker). Update documentation to use Rouge code styling and Amber general style. Regex: Breaking Change: Change \B to be the opposite of \b as per Perl behaviour. Change w32_regex_traits.hpp so that windows.h is no longer included. Fxed fuzzing related issues #151, #152, #153, #156. System: Added support for source locations to error_code. Added error_code::to_string, error_condition::to_string, error_code::what. system_error::what() now contains the source location, if present. Added result<T, E = error_code>, a class holding either a value or an error, defined in <boost/system/result.hpp>. Utility: Library documentation converted to QuickBook (thanks to Alan de Freitas, PR#79). Variant2: Added <boost/variant2.hpp>. Added unsafe_get<I>. Added visit_by_index. Added operator<<. Updated Tools Build: Includes release of B2 version 4.7.2. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

New Libraries No new libraries. Updated Libraries Asio: Added an io_uring backend that may ... [More] optionally be used for all I/O objects, including sockets, timers, and posix descriptors. Added support for files, with new new classes for stream-oriented and random-access files. This feature currently supports I/O completion ports on Windows, and io_uring on Linux. Added support for portable pipes on POSIX and Windows (when I/O completion ports are available). Added support for registered buffers, which are optimised when using the io_uring backend. Added experimental support for channels, that may be used to send and queue completions as messages. Implemented improvements to experimental::coro. Disabled aligned_alloc on clang when using an MSVC runtime. Changed to use a faster implementation for ip::network_v4::canonical(). Added template specialisations for common uses to improve compile time. Reduced the size of io_context executors to a single pointer. Increased the small object buffer size for execution::any_executor and any_io_executor. Fixed multi-signature handling when variadic templates are disabled. Fixed compatibility with new versions of gcc and clang. Fixed compilation on Solaris. Fixed defence against Qt-defined macros when building with MSVC. Improved error messages emitted by ssl facilities. Fixed bind_executor compatibility with completion tokens. Fixed build errors when BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT is defined. Added missing move assignment operator to awaitable<>. Fixed an access violation when using coroutines with MSVC, due to incorrect alignment of allocated memory. Fixed a cleanup issue in experimental::parallel_group that occured when the execution context was shut down with parallel operations still pending. Added clarifications to the documentation on concurrency hints. Added documentation on error handling techniques for C++20 coroutines. Fixed various warnings. Consult the Revision History for further details. Assert: Added source_location::to_string. Atomic: Use process-local futex operations on Android for non-IPC waiting and notifying operations. Added support for Linux targets that only define SYS_futex_time64 syscall, such as riscv32. Added a workaround for incorrect result of std::alignment_of on clang 8 for 64-bit types on 32-bit x86 targets. Added a ulock backend for waiting and notifying operations on Darwin systems since Mac OS 10.12, iOS 10.0, tvOS 10.0 or watchOS 3.0. On Windows, corrected discrepancy between atomic-type::always_has_native_wait_notify and the corresponding capability macros when targeting Windows 8 or later. The library will now directly use WaitOnAddress and related APIs from public headers and therefore require user to link with synchronization.lib if the user requires Windows 8 or later by defining BOOST_USE_WINAPI_VERSION, _WIN32_WINNT or similar macros. The library is linked automatically on compilers that support auto-linking (e.g. MSVC). Added support for types with padding bits, except unions, on compilers that provide a way to clear the padding bits. This feature is supported by gcc 11 and MSVC 14.2 (compiler version 19.27) and newer, as well as other compilers supporting similar intrinsics. On compilers that don't allow to clear the padding bits, types with padding are still generally not supported with the exception of 80-bit long double on x86 targets. A new BOOST_ATOMIC_NO_CLEAR_PADDING capability macro is defined to indicate when clearing the padding is not supported. Initializing constructors of atomic_ref and ipc_atomic_ref no longer use atomic instructions to clear the padding bits in the referenced object. This reduces the cost of the atomic reference construction. Initializing constructors of atomic and ipc_atomic are now constexpr for enums, classes and floating point types. For classes and floating point types, the constructors are constexpr if the compiler supports constexpr std::bit_cast, the type has no padding bytes and no padding is required to implement native atomic operations. In accordance with C++20, default constructors of atomic and ipc_atomic now perform value initialization of the contained object. For types without a user-defined default constructor, this means the default-constructed atomic will be zero-initialized. Added a workaround for compilation error on AIX caused by the assembler tool not supporting numeric labels. (PR#50) Added a workaround for compilation error with Visual Studio 2015 prior to Update 3. (#52) See changelog for more details. Beast: This maintenance update brings minor bug fixes and updated CI reporting. Fixed security vulnerability CVE-2016-9840 in zlib implementation. Fixed WebSocket permessage_deflate implementation. This should result in an increase in compression performance when using Beast WebSockets. Removed the test stream and test framework's dependency on RTTI. You can now use our handy test stream to check your embedded asynchronous communications code! We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Core: Added a generic implementation to <boost/core/cmath.hpp>, enabled when BOOST_CORE_USE_GENERIC_CMATH is defined or when the platform does not provide the necessary facilities in <cmath>. Added boost::core::type_name, a utility function that returns the name of a type as a string. Added boost::span, a C++11 implementation of C++20's std::span (Glen Fernandes). Describe: Added has_describe_enumerators, has_describe_bases, has_describe_members. Added enum_to_string, enum_from_string. Added relational and stream insertion operators. Added descriptor_by_name, descriptor_by_pointer. DLL: Fixed missing #include, thanks to Denis Blank (PR#54) Dropped TravisCI in favor of GithubAction CI Filesystem: v4: path::filename and path::iterator no longer return an implicit trailing dot (".") element if the path ends with a directory separator. Instead, an empty path is returned, similar to C++17 std::filesystem. This also affects other methods that are defined in terms of iterators or filename, such as path::stem, path::compare or lexicographical_compare. For example, path("a/b/") == path("a/b/.") no longer holds true. (#193) v4: path::lexically_normal no longer produce a trailing dot (".") element and omits a directory separator after a trailing dot-dot ("..") element in the normalized paths. v4: path append operations now consider root name and root directory in the appended path. If the appended path is absolute, or root name is present and differs from the source path, the resulting path is equivalent to the appended path. If root directory is present, the result is the root directory and relative path rebased on top of the root name of the source path. Otherwise, the behavior is similar to v3. (#214) path::lexically_normal now converts directory separators to preferred separators in the root name of the normalized paths. Optimized overloads of path::assign, path::append, path::concat and the corresponding operators to avoid unnecessary path copying and reduce the amount of code redundancy. On POSIX systems, fixed absolute(p, base) returning a path with root name base.root_name() if p starts with a root directory. In such a case p is already an absolute path and should be returned as is. create_directories no longer reports an error if the input path consists entirely of dot (".") and dot-dot ("..") elements. The implementation is no longer using recursion internally and therefore is better protected from stack overflow on extremely long paths. On Windows, remove now supports deleting read-only files. The operation will attempt to reset the read-only attribute prior to removal. Note that this introduces a possibility of the read-only attribute being left unset, if the operation fails and the original value of the attribute fails to be restored. This also affects remove_all. (#216) remove_all now returns static_cast< uintmax_t >(-1) in case of error, similar to C++17 std::filesystem. Fixed a linking error about unresolved references to Boost.ContainerHash functions when user's code includes boost/filesystem/path.hpp but not boost/container_hash/hash.hpp and the compiler is set to preserve unused inline functions. (#215) Added a workaround for MSVC and compatible compilers eliminating path globals cleanup in release builds. This could lead to a memory leak if Boost.Filesystem shared library was repeatedly loaded and unloaded in the process. (#217) Geometry: Improvements PR#894 Optimization and refactoring of rtree queries. PR#913 DynamicGeometry and GeometryCollection support in various algorithms (undocumented for now). PR#922 DynamicGeometry and GeometryCollection support in distance (undocumented for now). Solved issues #867 Poor performance of rtree query iterator with nearest predicate for big k. #870 Compilation error in boost::geometry::self_turns. #896 Assertion failure in get_turns with BOOST_GEOMETRY_NO_ROBUSTNESS. Bugfixes PR#906 Invalid result of buffer on macos-11 with clang-12. PR#921 Compilation errors with c++20 (various compilers) and gcc-5. Various fixes in set operations and buffer. JSON: Standalone mode of the library is deprecated. Allow external libraries to forward declare value_to and value_from. Fixed signed integer overflow in number parsing. Add support for /Zc:implicitNoexcept- on MSVC. Lambda2: Added special cases in operator<< and operator>> when the first argument is a stream, to allow std::cout << _1. Added operator->*. Added first, second. Log: General changes: Updated detection of std::codecvt specializations for char16_t and char32_t for compatibility with C++17 and later. (PR#159) Added support for C++17 std::byte type to receive methods of the inter-process message queue. On Windows, when building the library for Windows 8 or later, the library will use nt62 tag in the version namespace to denote the target OS ABI. For example, the version namespace could be named as v2_mt_nt62. This name will be part of all symbols exported by the library. Use the BOOST_USE_WINAPI_VERSION macro consistenly when building Boost and your code to request the minimum target Windows version. Improved performance of SSSE3 and AVX2 implementations of the dump stream manipulator. Added support for CMake build system. Only library build is supported at this moment, Boost.Build is still used for running tests. Bug fixes: Fixed a race condition on POSIX systems in reliable_message_queue::open_or_create or the equivalent constructor. Multiple threads or processes calling open_or_create concurrently with sending or receiving messages from the same queue could end up corrupting the queue contents and potentially crashing the process. (#162) Added a workaround for b2 install failing on Windows because of missing boost_log_setup library if BOOST_LOG_WITHOUT_SETTINGS_PARSERS is defined. (#164) See changelog for more details. Math: Add support for cubic roots. Add support for constexpr versions of various standard library math routines. Add support for Bezier polynomials. Improve worst-case tanh-sinh integration performance. Disable inadvertant use of integral types in integration routines. Minor update for erf approximations when the result is with 2ulp of 1. Allow Bernoulli code to be used on platforms with no atomic integers. Improve the mode of the non-central Chi Squared distribution. Improve certain edge cases for complex-valued elementary functions, see #507. Multi-index Containers: Added contains to key-based indices (issue #35). Added merge operations to key-based indices. The functionality goes beyond the standard specification for (unordered) associative containers in a number of ways, most notably: The source index can be of any type, including non key-based indices. Partial merge is provided: for instance, x.merge(y,first,last) merges only the elements of y within [first,last). Previous versions of splice for sequenced and random access indices were destructive, i.e. elements were copy-inserted into the destination and then erased from the source. Now, splice is based on node transfer much as merge in key-based indices, and has been similarly extended to accept source indices of any type: in fact, splice can be regarded as a frontend to the same functionality provided by merge in key-based indices. For reasons of backwards compatibility, the destructive behavior of splice has been retained in the case that the source and destination containers have unequal allocators. The fact has been documented that index iterator types do only depend on node_type and the position of the index in its multi_index_container, (except for hashed indices, where uniqueness/non-uniqueness is also a dependency). This has implications on the validity of iterators to elements transferred by merge or splice. This property is a variant of what has been called SCARY iterators in the C++ standard mailing lists. SCARYness is currently (August 2021) not mandated for standard containers. Iterator SCARYness is now also preserved in safe mode. Multiprecision: Rework rational_adaptor to remove dependency on Boost.Rational and improve performance. Fix issue with type_traits and clang, see #383. Fixed buggy Lehmer's GCD routine, see #370. Fix mpc_complex constructors so that lossy conversions are explicit, see #363. Correct miscellaneous configuration issues (Intel intrinsic usage and Apple clang). Correct some iostream operators for unsigned char types. Correct mpq_rational conversions to integer types, see #342. PFR: Added missing #include <memory> for inclusion of std::addressof Fixed -Wzero-length-array warning when dealing with empty aggregates Fixed compilation on msvc compilers <= 1920 (thanks to Alexey Romanov aka @alexey-romanov) Added basic CMakeLists.txt support (thanks to @pdimov aka Peter Dimov) Multiple improvements for docs, including links to https://github.com/apolukhin/pfr_non_boost Added misc/strip_boost_namespace.sh script to remove boost:: and BOOST_ prefixes Predef: Version 1.13.1 Fix spelling of "epoch". Add missing parenthesis in sparc.h (from tkoecker). Update documentation to use Rouge code styling and Amber general style. Regex: Breaking Change: Change \B to be the opposite of \b as per Perl behaviour. Change w32_regex_traits.hpp so that windows.h is no longer included. Fxed fuzzing related issues #151, #152, #153, #156. System: Added support for source locations to error_code. Added error_code::to_string, error_condition::to_string, error_code::what. system_error::what() now contains the source location, if present. Added result<T, E = error_code>, a class holding either a value or an error, defined in <boost/system/result.hpp>. Utility: Library documentation converted to QuickBook (thanks to Alan de Freitas, PR#79). Variant2: Added <boost/variant2.hpp>. Added unsafe_get<I>. Added visit_by_index. Added operator<<. Updated Tools Build: Includes release of B2 version 4.7.2. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

Known Issues These are patches from library authors which were found too late to be fixed in the release. Boost.Build silently skips installation of library headers and binaries ... [More] in some cases, see #104. Fixed in PR#113, patch. Boost.Atomic fails to build when targeting UWP, see #54. Patch. New Libraries No new libraries. Updated Libraries Asio: Added an io_uring backend that may optionally be used for all I/O objects, including sockets, timers, and posix descriptors. Added support for files, with new new classes for stream-oriented and random-access files. This feature currently supports I/O completion ports on Windows, and io_uring on Linux. Added support for portable pipes on POSIX and Windows (when I/O completion ports are available). Added support for registered buffers, which are optimised when using the io_uring backend. Added experimental support for channels, that may be used to send and queue completions as messages. Implemented improvements to experimental::coro. Disabled aligned_alloc on clang when using an MSVC runtime. Changed to use a faster implementation for ip::network_v4::canonical(). Added template specialisations for common uses to improve compile time. Reduced the size of io_context executors to a single pointer. Increased the small object buffer size for execution::any_executor and any_io_executor. Fixed multi-signature handling when variadic templates are disabled. Fixed compatibility with new versions of gcc and clang. Fixed compilation on Solaris. Fixed defence against Qt-defined macros when building with MSVC. Improved error messages emitted by ssl facilities. Fixed bind_executor compatibility with completion tokens. Fixed build errors when BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT is defined. Added missing move assignment operator to awaitable<>. Fixed an access violation when using coroutines with MSVC, due to incorrect alignment of allocated memory. Fixed a cleanup issue in experimental::parallel_group that occured when the execution context was shut down with parallel operations still pending. Added clarifications to the documentation on concurrency hints. Added documentation on error handling techniques for C++20 coroutines. Fixed various warnings. Consult the Revision History for further details. Assert: Added source_location::to_string. Atomic: Use process-local futex operations on Android for non-IPC waiting and notifying operations. Added support for Linux targets that only define SYS_futex_time64 syscall, such as riscv32. Added a workaround for incorrect result of std::alignment_of on clang 8 for 64-bit types on 32-bit x86 targets. Added a ulock backend for waiting and notifying operations on Darwin systems since Mac OS 10.12, iOS 10.0, tvOS 10.0 or watchOS 3.0. On Windows, corrected discrepancy between atomic-type::always_has_native_wait_notify and the corresponding capability macros when targeting Windows 8 or later. The library will now directly use WaitOnAddress and related APIs from public headers and therefore require user to link with synchronization.lib if the user requires Windows 8 or later by defining BOOST_USE_WINAPI_VERSION, _WIN32_WINNT or similar macros. The library is linked automatically on compilers that support auto-linking (e.g. MSVC). Added support for types with padding bits, except unions, on compilers that provide a way to clear the padding bits. This feature is supported by gcc 11 and MSVC 14.2 (compiler version 19.27) and newer, as well as other compilers supporting similar intrinsics. On compilers that don't allow to clear the padding bits, types with padding are still generally not supported with the exception of 80-bit long double on x86 targets. A new BOOST_ATOMIC_NO_CLEAR_PADDING capability macro is defined to indicate when clearing the padding is not supported. Initializing constructors of atomic_ref and ipc_atomic_ref no longer use atomic instructions to clear the padding bits in the referenced object. This reduces the cost of the atomic reference construction. Initializing constructors of atomic and ipc_atomic are now constexpr for enums, classes and floating point types. For classes and floating point types, the constructors are constexpr if the compiler supports constexpr std::bit_cast, the type has no padding bytes and no padding is required to implement native atomic operations. In accordance with C++20, default constructors of atomic and ipc_atomic now perform value initialization of the contained object. For types without a user-defined default constructor, this means the default-constructed atomic will be zero-initialized. Added a workaround for compilation error on AIX caused by the assembler tool not supporting numeric labels. (PR#50) Added a workaround for compilation error with Visual Studio 2015 prior to Update 3. (#52) See changelog for more details. Beast: This maintenance update brings minor bug fixes and updated CI reporting. Fixed security vulnerability CVE-2016-9840 in zlib implementation. Fixed WebSocket permessage_deflate implementation. This should result in an increase in compression performance when using Beast WebSockets. Removed the test stream and test framework's dependency on RTTI. You can now use our handy test stream to check your embedded asynchronous communications code! We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Core: Added a generic implementation to <boost/core/cmath.hpp>, enabled when BOOST_CORE_USE_GENERIC_CMATH is defined or when the platform does not provide the necessary facilities in <cmath>. Added boost::core::type_name, a utility function that returns the name of a type as a string. Added boost::span, a C++11 implementation of C++20's std::span (Glen Fernandes). Describe: Added has_describe_enumerators, has_describe_bases, has_describe_members. Added enum_to_string, enum_from_string. Added relational and stream insertion operators. Added descriptor_by_name, descriptor_by_pointer. DLL: Fixed missing #include, thanks to Denis Blank (PR#54) Dropped TravisCI in favor of GithubAction CI Filesystem: v4: path::filename and path::iterator no longer return an implicit trailing dot (".") element if the path ends with a directory separator. Instead, an empty path is returned, similar to C++17 std::filesystem. This also affects other methods that are defined in terms of iterators or filename, such as path::stem, path::compare or lexicographical_compare. For example, path("a/b/") == path("a/b/.") no longer holds true. (#193) v4: path::lexically_normal no longer produce a trailing dot (".") element and omits a directory separator after a trailing dot-dot ("..") element in the normalized paths. v4: path append operations now consider root name and root directory in the appended path. If the appended path is absolute, or root name is present and differs from the source path, the resulting path is equivalent to the appended path. If root directory is present, the result is the root directory and relative path rebased on top of the root name of the source path. Otherwise, the behavior is similar to v3. (#214) path::lexically_normal now converts directory separators to preferred separators in the root name of the normalized paths. Optimized overloads of path::assign, path::append, path::concat and the corresponding operators to avoid unnecessary path copying and reduce the amount of code redundancy. On POSIX systems, fixed absolute(p, base) returning a path with root name base.root_name() if p starts with a root directory. In such a case p is already an absolute path and should be returned as is. create_directories no longer reports an error if the input path consists entirely of dot (".") and dot-dot ("..") elements. The implementation is no longer using recursion internally and therefore is better protected from stack overflow on extremely long paths. On Windows, remove now supports deleting read-only files. The operation will attempt to reset the read-only attribute prior to removal. Note that this introduces a possibility of the read-only attribute being left unset, if the operation fails and the original value of the attribute fails to be restored. This also affects remove_all. (#216) remove_all now returns static_cast< uintmax_t >(-1) in case of error, similar to C++17 std::filesystem. Fixed a linking error about unresolved references to Boost.ContainerHash functions when user's code includes boost/filesystem/path.hpp but not boost/container_hash/hash.hpp and the compiler is set to preserve unused inline functions. (#215) Added a workaround for MSVC and compatible compilers eliminating path globals cleanup in release builds. This could lead to a memory leak if Boost.Filesystem shared library was repeatedly loaded and unloaded in the process. (#217) Geometry: Improvements PR#894 Optimization and refactoring of rtree queries. PR#913 DynamicGeometry and GeometryCollection support in various algorithms (undocumented for now). PR#922 DynamicGeometry and GeometryCollection support in distance (undocumented for now). Solved issues #867 Poor performance of rtree query iterator with nearest predicate for big k. #870 Compilation error in boost::geometry::self_turns. #896 Assertion failure in get_turns with BOOST_GEOMETRY_NO_ROBUSTNESS. Bugfixes PR#906 Invalid result of buffer on macos-11 with clang-12. PR#921 Compilation errors with c++20 (various compilers) and gcc-5. Various fixes in set operations and buffer. JSON: Standalone mode of the library is deprecated. Allow external libraries to forward declare value_to and value_from. Fixed signed integer overflow in number parsing. Add support for /Zc:implicitNoexcept- on MSVC. Lambda2: Added special cases in operator<< and operator>> when the first argument is a stream, to allow std::cout << _1. Added operator->*. Added first, second. Log: General changes: Updated detection of std::codecvt specializations for char16_t and char32_t for compatibility with C++17 and later. (PR#159) Added support for C++17 std::byte type to receive methods of the inter-process message queue. On Windows, when building the library for Windows 8 or later, the library will use nt62 tag in the version namespace to denote the target OS ABI. For example, the version namespace could be named as v2_mt_nt62. This name will be part of all symbols exported by the library. Use the BOOST_USE_WINAPI_VERSION macro consistenly when building Boost and your code to request the minimum target Windows version. Improved performance of SSSE3 and AVX2 implementations of the dump stream manipulator. Added support for CMake build system. Only library build is supported at this moment, Boost.Build is still used for running tests. Bug fixes: Fixed a race condition on POSIX systems in reliable_message_queue::open_or_create or the equivalent constructor. Multiple threads or processes calling open_or_create concurrently with sending or receiving messages from the same queue could end up corrupting the queue contents and potentially crashing the process. (#162) Added a workaround for b2 install failing on Windows because of missing boost_log_setup library if BOOST_LOG_WITHOUT_SETTINGS_PARSERS is defined. (#164) See changelog for more details. Math: Add support for cubic roots. Add support for constexpr versions of various standard library math routines. Add support for Bezier polynomials. Improve worst-case tanh-sinh integration performance. Disable inadvertant use of integral types in integration routines. Minor update for erf approximations when the result is with 2ulp of 1. Allow Bernoulli code to be used on platforms with no atomic integers. Improve the mode of the non-central Chi Squared distribution. Improve certain edge cases for complex-valued elementary functions, see #507. Multi-index Containers: Added contains to key-based indices (issue #35). Added merge operations to key-based indices. The functionality goes beyond the standard specification for (unordered) associative containers in a number of ways, most notably: The source index can be of any type, including non key-based indices. Partial merge is provided: for instance, x.merge(y,first,last) merges only the elements of y within [first,last). Previous versions of splice for sequenced and random access indices were destructive, i.e. elements were copy-inserted into the destination and then erased from the source. Now, splice is based on node transfer much as merge in key-based indices, and has been similarly extended to accept source indices of any type: in fact, splice can be regarded as a frontend to the same functionality provided by merge in key-based indices. For reasons of backwards compatibility, the destructive behavior of splice has been retained in the case that the source and destination containers have unequal allocators. The fact has been documented that index iterator types do only depend on node_type and the position of the index in its multi_index_container, (except for hashed indices, where uniqueness/non-uniqueness is also a dependency). This has implications on the validity of iterators to elements transferred by merge or splice. This property is a variant of what has been called SCARY iterators in the C++ standard mailing lists. SCARYness is currently (August 2021) not mandated for standard containers. Iterator SCARYness is now also preserved in safe mode. Multiprecision: Rework rational_adaptor to remove dependency on Boost.Rational and improve performance. Fix issue with type_traits and clang, see #383. Fixed buggy Lehmer's GCD routine, see #370. Fix mpc_complex constructors so that lossy conversions are explicit, see #363. Correct miscellaneous configuration issues (Intel intrinsic usage and Apple clang). Correct some iostream operators for unsigned char types. Correct mpq_rational conversions to integer types, see #342. PFR: Added missing #include <memory> for inclusion of std::addressof Fixed -Wzero-length-array warning when dealing with empty aggregates Fixed compilation on msvc compilers <= 1920 (thanks to Alexey Romanov aka @alexey-romanov) Added basic CMakeLists.txt support (thanks to @pdimov aka Peter Dimov) Multiple improvements for docs, including links to https://github.com/apolukhin/pfr_non_boost Added misc/strip_boost_namespace.sh script to remove boost:: and BOOST_ prefixes Predef: Version 1.13.1 Fix spelling of "epoch". Add missing parenthesis in sparc.h (from tkoecker). Update documentation to use Rouge code styling and Amber general style. Regex: Breaking Change: Change \B to be the opposite of \b as per Perl behaviour. Change w32_regex_traits.hpp so that windows.h is no longer included. Fxed fuzzing related issues #151, #152, #153, #156. System: Added support for source locations to error_code. Added error_code::to_string, error_condition::to_string, error_code::what. system_error::what() now contains the source location, if present. Added result<T, E = error_code>, a class holding either a value or an error, defined in <boost/system/result.hpp>. Utility: Library documentation converted to QuickBook (thanks to Alan de Freitas, PR#79). Variant2: Added <boost/variant2.hpp>. Added unsafe_get<I>. Added visit_by_index. Added operator<<. Updated Tools Build: Includes release of B2 version 4.7.2. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

New Libraries No new libraries. Updated Libraries Asio: Added an io_uring backend that may ... [More] optionally be used for all I/O objects, including sockets, timers, and posix descriptors. Added support for files, with new new classes for stream-oriented and random-access files. This feature currently supports I/O completion ports on Windows, and io_uring on Linux. Added support for portable pipes on POSIX and Windows (when I/O completion ports are available). Added support for registered buffers, which are optimised when using the io_uring backend. Added experimental support for channels, that may be used to send and queue completions as messages. Implemented improvements to experimental::coro. Disabled aligned_alloc on clang when using an MSVC runtime. Changed to use a faster implementation for ip::network_v4::canonical(). Added template specialisations for common uses to improve compile time. Reduced the size of io_context executors to a single pointer. Increased the small object buffer size for execution::any_executor and any_io_executor. Fixed multi-signature handling when variadic templates are disabled. Fixed compatibility with new versions of gcc and clang. Fixed compilation on Solaris. Fixed defence against Qt-defined macros when building with MSVC. Improved error messages emitted by ssl facilities. Fixed bind_executor compatibility with completion tokens. Fixed build errors when BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT is defined. Added missing move assignment operator to awaitable<>. Fixed an access violation when using coroutines with MSVC, due to incorrect alignment of allocated memory. Fixed a cleanup issue in experimental::parallel_group that occured when the execution context was shut down with parallel operations still pending. Added clarifications to the documentation on concurrency hints. Added documentation on error handling techniques for C++20 coroutines. Fixed various warnings. Consult the Revision History for further details. Assert: Added source_location::to_string. Atomic: Use process-local futex operations on Android for non-IPC waiting and notifying operations. Added support for Linux targets that only define SYS_futex_time64 syscall, such as riscv32. Added a workaround for incorrect result of std::alignment_of on clang 8 for 64-bit types on 32-bit x86 targets. Added a ulock backend for waiting and notifying operations on Darwin systems since Mac OS 10.12, iOS 10.0, tvOS 10.0 or watchOS 3.0. On Windows, corrected discrepancy between atomic-type::always_has_native_wait_notify and the corresponding capability macros when targeting Windows 8 or later. The library will now directly use WaitOnAddress and related APIs from public headers and therefore require user to link with synchronization.lib if the user requires Windows 8 or later by defining BOOST_USE_WINAPI_VERSION, _WIN32_WINNT or similar macros. The library is linked automatically on compilers that support auto-linking (e.g. MSVC). Added support for types with padding bits, except unions, on compilers that provide a way to clear the padding bits. This feature is supported by gcc 11 and MSVC 14.2 (compiler version 19.27) and newer, as well as other compilers supporting similar intrinsics. On compilers that don't allow to clear the padding bits, types with padding are still generally not supported with the exception of 80-bit long double on x86 targets. A new BOOST_ATOMIC_NO_CLEAR_PADDING capability macro is defined to indicate when clearing the padding is not supported. Initializing constructors of atomic_ref and ipc_atomic_ref no longer use atomic instructions to clear the padding bits in the referenced object. This reduces the cost of the atomic reference construction. Initializing constructors of atomic and ipc_atomic are now constexpr for enums, classes and floating point types. For classes and floating point types, the constructors are constexpr if the compiler supports constexpr std::bit_cast, the type has no padding bytes and no padding is required to implement native atomic operations. In accordance with C++20, default constructors of atomic and ipc_atomic now perform value initialization of the contained object. For types without a user-defined default constructor, this means the default-constructed atomic will be zero-initialized. Added a workaround for compilation error on AIX caused by the assembler tool not supporting numeric labels. (PR#50) Added a workaround for compilation error with Visual Studio 2015 prior to Update 3. (#52) See changelog for more details. Beast: This maintenance update brings minor bug fixes and updated CI reporting. Fixed security vulnerability CVE-2016-9840 in zlib implementation. Fixed WebSocket permessage_deflate implementation. This should result in an increase in compression performance when using Beast WebSockets. Removed the test stream and test framework's dependency on RTTI. You can now use our handy test stream to check your embedded asynchronous communications code! We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Core: Added a generic implementation to <boost/core/cmath.hpp>, enabled when BOOST_CORE_USE_GENERIC_CMATH is defined or when the platform does not provide the necessary facilities in <cmath>. Added boost::core::type_name, a utility function that returns the name of a type as a string. Added boost::span, a C++11 implementation of C++20's std::span (Glen Fernandes). Describe: Added has_describe_enumerators, has_describe_bases, has_describe_members. Added enum_to_string, enum_from_string. Added relational and stream insertion operators. Added descriptor_by_name, descriptor_by_pointer. DLL: Fixed missing #include, thanks to Denis Blank (PR#54) Dropped TravisCI in favor of GithubAction CI Filesystem: v4: path::filename and path::iterator no longer return an implicit trailing dot (".") element if the path ends with a directory separator. Instead, an empty path is returned, similar to C++17 std::filesystem. This also affects other methods that are defined in terms of iterators or filename, such as path::stem, path::compare or lexicographical_compare. For example, path("a/b/") == path("a/b/.") no longer holds true. (#193) v4: path::lexically_normal no longer produce a trailing dot (".") element and omits a directory separator after a trailing dot-dot ("..") element in the normalized paths. v4: path append operations now consider root name and root directory in the appended path. If the appended path is absolute, or root name is present and differs from the source path, the resulting path is equivalent to the appended path. If root directory is present, the result is the root directory and relative path rebased on top of the root name of the source path. Otherwise, the behavior is similar to v3. (#214) path::lexically_normal now converts directory separators to preferred separators in the root name of the normalized paths. Optimized overloads of path::assign, path::append, path::concat and the corresponding operators to avoid unnecessary path copying and reduce the amount of code redundancy. On POSIX systems, fixed absolute(p, base) returning a path with root name base.root_name() if p starts with a root directory. In such a case p is already an absolute path and should be returned as is. create_directories no longer reports an error if the input path consists entirely of dot (".") and dot-dot ("..") elements. The implementation is no longer using recursion internally and therefore is better protected from stack overflow on extremely long paths. On Windows, remove now supports deleting read-only files. The operation will attempt to reset the read-only attribute prior to removal. Note that this introduces a possibility of the read-only attribute being left unset, if the operation fails and the original value of the attribute fails to be restored. This also affects remove_all. (#216) remove_all now returns static_cast< uintmax_t >(-1) in case of error, similar to C++17 std::filesystem. Fixed a linking error about unresolved references to Boost.ContainerHash functions when user's code includes boost/filesystem/path.hpp but not boost/container_hash/hash.hpp and the compiler is set to preserve unused inline functions. (#215) Added a workaround for MSVC and compatible compilers eliminating path globals cleanup in release builds. This could lead to a memory leak if Boost.Filesystem shared library was repeatedly loaded and unloaded in the process. (#217) Geometry: Improvements PR#894 Optimization and refactoring of rtree queries. PR#913 DynamicGeometry and GeometryCollection support in various algorithms (undocumented for now). PR#922 DynamicGeometry and GeometryCollection support in distance (undocumented for now). Solved issues #867 Poor performance of rtree query iterator with nearest predicate for big k. #870 Compilation error in boost::geometry::self_turns. #896 Assertion failure in get_turns with BOOST_GEOMETRY_NO_ROBUSTNESS. Bugfixes PR#906 Invalid result of buffer on macos-11 with clang-12. PR#921 Compilation errors with c++20 (various compilers) and gcc-5. Various fixes in set operations and buffer. JSON: Standalone mode of the library is deprecated. Allow external libraries to forward declare value_to and value_from. Fixed signed integer overflow in number parsing. Add support for /Zc:implicitNoexcept- on MSVC. Lambda2: Added special cases in operator<< and operator>> when the first argument is a stream, to allow std::cout << _1. Added operator->*. Added first, second. Log: General changes: Updated detection of std::codecvt specializations for char16_t and char32_t for compatibility with C++17 and later. (PR#159) Added support for C++17 std::byte type to receive methods of the inter-process message queue. On Windows, when building the library for Windows 8 or later, the library will use nt62 tag in the version namespace to denote the target OS ABI. For example, the version namespace could be named as v2_mt_nt62. This name will be part of all symbols exported by the library. Use the BOOST_USE_WINAPI_VERSION macro consistenly when building Boost and your code to request the minimum target Windows version. Improved performance of SSSE3 and AVX2 implementations of the dump stream manipulator. Added support for CMake build system. Only library build is supported at this moment, Boost.Build is still used for running tests. Bug fixes: Fixed a race condition on POSIX systems in reliable_message_queue::open_or_create or the equivalent constructor. Multiple threads or processes calling open_or_create concurrently with sending or receiving messages from the same queue could end up corrupting the queue contents and potentially crashing the process. (#162) Added a workaround for b2 install failing on Windows because of missing boost_log_setup library if BOOST_LOG_WITHOUT_SETTINGS_PARSERS is defined. (#164) See changelog for more details. Math: Add support for cubic roots. Add support for constexpr versions of various standard library math routines. Add support for Bezier polynomials. Improve worst-case tanh-sinh integration performance. Disable inadvertant use of integral types in integration routines. Minor update for erf approximations when the result is with 2ulp of 1. Allow Bernoulli code to be used on platforms with no atomic integers. Improve the mode of the non-central Chi Squared distribution. Improve certain edge cases for complex-valued elementary functions, see #507. Multi-index Containers: Added contains to key-based indices (issue #35). Added merge operations to key-based indices. The functionality goes beyond the standard specification for (unordered) associative containers in a number of ways, most notably: The source index can be of any type, including non key-based indices. Partial merge is provided: for instance, x.merge(y,first,last) merges only the elements of y within [first,last). Previous versions of splice for sequenced and random access indices were destructive, i.e. elements were copy-inserted into the destination and then erased from the source. Now, splice is based on node transfer much as merge in key-based indices, and has been similarly extended to accept source indices of any type: in fact, splice can be regarded as a frontend to the same functionality provided by merge in key-based indices. For reasons of backwards compatibility, the destructive behavior of splice has been retained in the case that the source and destination containers have unequal allocators. The fact has been documented that index iterator types do only depend on node_type and the position of the index in its multi_index_container, (except for hashed indices, where uniqueness/non-uniqueness is also a dependency). This has implications on the validity of iterators to elements transferred by merge or splice. This property is a variant of what has been called SCARY iterators in the C++ standard mailing lists. SCARYness is currently (August 2021) not mandated for standard containers. Iterator SCARYness is now also preserved in safe mode. Multiprecision: Rework rational_adaptor to remove dependency on Boost.Rational and improve performance. Fix issue with type_traits and clang, see #383. Fixed buggy Lehmer's GCD routine, see #370. Fix mpc_complex constructors so that lossy conversions are explicit, see #363. Correct miscellaneous configuration issues (Intel intrinsic usage and Apple clang). Correct some iostream operators for unsigned char types. Correct mpq_rational conversions to integer types, see #342. PFR: Added missing #include <memory> for inclusion of std::addressof Fixed -Wzero-length-array warning when dealing with empty aggregates Fixed compilation on msvc compilers <= 1920 (thanks to Alexey Romanov aka @alexey-romanov) Added basic CMakeLists.txt support (thanks to @pdimov aka Peter Dimov) Multiple improvements for docs, including links to https://github.com/apolukhin/pfr_non_boost Added misc/strip_boost_namespace.sh script to remove boost:: and BOOST_ prefixes Predef: Version 1.13.1 Fix spelling of "epoch". Add missing parenthesis in sparc.h (from tkoecker). Update documentation to use Rouge code styling and Amber general style. Regex: Breaking Change: Change \B to be the opposite of \b as per Perl behaviour. Change w32_regex_traits.hpp so that windows.h is no longer included. Fxed fuzzing related issues #151, #152, #153, #156. System: Added support for source locations to error_code. Added error_code::to_string, error_condition::to_string, error_code::what. system_error::what() now contains the source location, if present. Added result<T, E = error_code>, a class holding either a value or an error, defined in <boost/system/result.hpp>. Utility: Library documentation converted to QuickBook (thanks to Alan de Freitas, PR#79). Variant2: Added <boost/variant2.hpp>. Added unsafe_get<I>. Added visit_by_index. Added operator<<. Updated Tools Build: Includes release of B2 version 4.7.2. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

Known Issues These are patches from library authors which were found too late to be fixed in the release. Boost.Build silently skips installation of library headers and binaries ... [More] in some cases, see #104. Fixed in PR#113, patch. Boost.Atomic fails to build when targeting UWP, see #54. Patch. New Libraries No new libraries. Updated Libraries Asio: Added an io_uring backend that may optionally be used for all I/O objects, including sockets, timers, and posix descriptors. Added support for files, with new new classes for stream-oriented and random-access files. This feature currently supports I/O completion ports on Windows, and io_uring on Linux. Added support for portable pipes on POSIX and Windows (when I/O completion ports are available). Added support for registered buffers, which are optimised when using the io_uring backend. Added experimental support for channels, that may be used to send and queue completions as messages. Implemented improvements to experimental::coro. Disabled aligned_alloc on clang when using an MSVC runtime. Changed to use a faster implementation for ip::network_v4::canonical(). Added template specialisations for common uses to improve compile time. Reduced the size of io_context executors to a single pointer. Increased the small object buffer size for execution::any_executor and any_io_executor. Fixed multi-signature handling when variadic templates are disabled. Fixed compatibility with new versions of gcc and clang. Fixed compilation on Solaris. Fixed defence against Qt-defined macros when building with MSVC. Improved error messages emitted by ssl facilities. Fixed bind_executor compatibility with completion tokens. Fixed build errors when BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT is defined. Added missing move assignment operator to awaitable<>. Fixed an access violation when using coroutines with MSVC, due to incorrect alignment of allocated memory. Fixed a cleanup issue in experimental::parallel_group that occured when the execution context was shut down with parallel operations still pending. Added clarifications to the documentation on concurrency hints. Added documentation on error handling techniques for C++20 coroutines. Fixed various warnings. Consult the Revision History for further details. Assert: Added source_location::to_string. Atomic: Use process-local futex operations on Android for non-IPC waiting and notifying operations. Added support for Linux targets that only define SYS_futex_time64 syscall, such as riscv32. Added a workaround for incorrect result of std::alignment_of on clang 8 for 64-bit types on 32-bit x86 targets. Added a ulock backend for waiting and notifying operations on Darwin systems since Mac OS 10.12, iOS 10.0, tvOS 10.0 or watchOS 3.0. On Windows, corrected discrepancy between atomic-type::always_has_native_wait_notify and the corresponding capability macros when targeting Windows 8 or later. The library will now directly use WaitOnAddress and related APIs from public headers and therefore require user to link with synchronization.lib if the user requires Windows 8 or later by defining BOOST_USE_WINAPI_VERSION, _WIN32_WINNT or similar macros. The library is linked automatically on compilers that support auto-linking (e.g. MSVC). Added support for types with padding bits, except unions, on compilers that provide a way to clear the padding bits. This feature is supported by gcc 11 and MSVC 14.2 (compiler version 19.27) and newer, as well as other compilers supporting similar intrinsics. On compilers that don't allow to clear the padding bits, types with padding are still generally not supported with the exception of 80-bit long double on x86 targets. A new BOOST_ATOMIC_NO_CLEAR_PADDING capability macro is defined to indicate when clearing the padding is not supported. Initializing constructors of atomic_ref and ipc_atomic_ref no longer use atomic instructions to clear the padding bits in the referenced object. This reduces the cost of the atomic reference construction. Initializing constructors of atomic and ipc_atomic are now constexpr for enums, classes and floating point types. For classes and floating point types, the constructors are constexpr if the compiler supports constexpr std::bit_cast, the type has no padding bytes and no padding is required to implement native atomic operations. In accordance with C++20, default constructors of atomic and ipc_atomic now perform value initialization of the contained object. For types without a user-defined default constructor, this means the default-constructed atomic will be zero-initialized. Added a workaround for compilation error on AIX caused by the assembler tool not supporting numeric labels. (PR#50) Added a workaround for compilation error with Visual Studio 2015 prior to Update 3. (#52) See changelog for more details. Beast: This maintenance update brings minor bug fixes and updated CI reporting. Fixed security vulnerability CVE-2016-9840 in zlib implementation. Fixed WebSocket permessage_deflate implementation. This should result in an increase in compression performance when using Beast WebSockets. Removed the test stream and test framework's dependency on RTTI. You can now use our handy test stream to check your embedded asynchronous communications code! We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Core: Added a generic implementation to <boost/core/cmath.hpp>, enabled when BOOST_CORE_USE_GENERIC_CMATH is defined or when the platform does not provide the necessary facilities in <cmath>. Added boost::core::type_name, a utility function that returns the name of a type as a string. Added boost::span, a C++11 implementation of C++20's std::span (Glen Fernandes). Describe: Added has_describe_enumerators, has_describe_bases, has_describe_members. Added enum_to_string, enum_from_string. Added relational and stream insertion operators. Added descriptor_by_name, descriptor_by_pointer. DLL: Fixed missing #include, thanks to Denis Blank (PR#54) Dropped TravisCI in favor of GithubAction CI Filesystem: v4: path::filename and path::iterator no longer return an implicit trailing dot (".") element if the path ends with a directory separator. Instead, an empty path is returned, similar to C++17 std::filesystem. This also affects other methods that are defined in terms of iterators or filename, such as path::stem, path::compare or lexicographical_compare. For example, path("a/b/") == path("a/b/.") no longer holds true. (#193) v4: path::lexically_normal no longer produce a trailing dot (".") element and omits a directory separator after a trailing dot-dot ("..") element in the normalized paths. v4: path append operations now consider root name and root directory in the appended path. If the appended path is absolute, or root name is present and differs from the source path, the resulting path is equivalent to the appended path. If root directory is present, the result is the root directory and relative path rebased on top of the root name of the source path. Otherwise, the behavior is similar to v3. (#214) path::lexically_normal now converts directory separators to preferred separators in the root name of the normalized paths. Optimized overloads of path::assign, path::append, path::concat and the corresponding operators to avoid unnecessary path copying and reduce the amount of code redundancy. On POSIX systems, fixed absolute(p, base) returning a path with root name base.root_name() if p starts with a root directory. In such a case p is already an absolute path and should be returned as is. create_directories no longer reports an error if the input path consists entirely of dot (".") and dot-dot ("..") elements. The implementation is no longer using recursion internally and therefore is better protected from stack overflow on extremely long paths. On Windows, remove now supports deleting read-only files. The operation will attempt to reset the read-only attribute prior to removal. Note that this introduces a possibility of the read-only attribute being left unset, if the operation fails and the original value of the attribute fails to be restored. This also affects remove_all. (#216) remove_all now returns static_cast< uintmax_t >(-1) in case of error, similar to C++17 std::filesystem. Fixed a linking error about unresolved references to Boost.ContainerHash functions when user's code includes boost/filesystem/path.hpp but not boost/container_hash/hash.hpp and the compiler is set to preserve unused inline functions. (#215) Added a workaround for MSVC and compatible compilers eliminating path globals cleanup in release builds. This could lead to a memory leak if Boost.Filesystem shared library was repeatedly loaded and unloaded in the process. (#217) Geometry: Improvements PR#894 Optimization and refactoring of rtree queries. PR#913 DynamicGeometry and GeometryCollection support in various algorithms (undocumented for now). PR#922 DynamicGeometry and GeometryCollection support in distance (undocumented for now). Solved issues #867 Poor performance of rtree query iterator with nearest predicate for big k. #870 Compilation error in boost::geometry::self_turns. #896 Assertion failure in get_turns with BOOST_GEOMETRY_NO_ROBUSTNESS. Bugfixes PR#906 Invalid result of buffer on macos-11 with clang-12. PR#921 Compilation errors with c++20 (various compilers) and gcc-5. Various fixes in set operations and buffer. JSON: Standalone mode of the library is deprecated. Allow external libraries to forward declare value_to and value_from. Fixed signed integer overflow in number parsing. Add support for /Zc:implicitNoexcept- on MSVC. Lambda2: Added special cases in operator<< and operator>> when the first argument is a stream, to allow std::cout << _1. Added operator->*. Added first, second. Log: General changes: Updated detection of std::codecvt specializations for char16_t and char32_t for compatibility with C++17 and later. (PR#159) Added support for C++17 std::byte type to receive methods of the inter-process message queue. On Windows, when building the library for Windows 8 or later, the library will use nt62 tag in the version namespace to denote the target OS ABI. For example, the version namespace could be named as v2_mt_nt62. This name will be part of all symbols exported by the library. Use the BOOST_USE_WINAPI_VERSION macro consistenly when building Boost and your code to request the minimum target Windows version. Improved performance of SSSE3 and AVX2 implementations of the dump stream manipulator. Added support for CMake build system. Only library build is supported at this moment, Boost.Build is still used for running tests. Bug fixes: Fixed a race condition on POSIX systems in reliable_message_queue::open_or_create or the equivalent constructor. Multiple threads or processes calling open_or_create concurrently with sending or receiving messages from the same queue could end up corrupting the queue contents and potentially crashing the process. (#162) Added a workaround for b2 install failing on Windows because of missing boost_log_setup library if BOOST_LOG_WITHOUT_SETTINGS_PARSERS is defined. (#164) See changelog for more details. Math: Add support for cubic roots. Add support for constexpr versions of various standard library math routines. Add support for Bezier polynomials. Improve worst-case tanh-sinh integration performance. Disable inadvertant use of integral types in integration routines. Minor update for erf approximations when the result is with 2ulp of 1. Allow Bernoulli code to be used on platforms with no atomic integers. Improve the mode of the non-central Chi Squared distribution. Improve certain edge cases for complex-valued elementary functions, see #507. Multi-index Containers: Added contains to key-based indices (issue #35). Added merge operations to key-based indices. The functionality goes beyond the standard specification for (unordered) associative containers in a number of ways, most notably: The source index can be of any type, including non key-based indices. Partial merge is provided: for instance, x.merge(y,first,last) merges only the elements of y within [first,last). Previous versions of splice for sequenced and random access indices were destructive, i.e. elements were copy-inserted into the destination and then erased from the source. Now, splice is based on node transfer much as merge in key-based indices, and has been similarly extended to accept source indices of any type: in fact, splice can be regarded as a frontend to the same functionality provided by merge in key-based indices. For reasons of backwards compatibility, the destructive behavior of splice has been retained in the case that the source and destination containers have unequal allocators. The fact has been documented that index iterator types do only depend on node_type and the position of the index in its multi_index_container, (except for hashed indices, where uniqueness/non-uniqueness is also a dependency). This has implications on the validity of iterators to elements transferred by merge or splice. This property is a variant of what has been called SCARY iterators in the C++ standard mailing lists. SCARYness is currently (August 2021) not mandated for standard containers. Iterator SCARYness is now also preserved in safe mode. Multiprecision: Rework rational_adaptor to remove dependency on Boost.Rational and improve performance. Fix issue with type_traits and clang, see #383. Fixed buggy Lehmer's GCD routine, see #370. Fix mpc_complex constructors so that lossy conversions are explicit, see #363. Correct miscellaneous configuration issues (Intel intrinsic usage and Apple clang). Correct some iostream operators for unsigned char types. Correct mpq_rational conversions to integer types, see #342. PFR: Added missing #include <memory> for inclusion of std::addressof Fixed -Wzero-length-array warning when dealing with empty aggregates Fixed compilation on msvc compilers <= 1920 (thanks to Alexey Romanov aka @alexey-romanov) Added basic CMakeLists.txt support (thanks to @pdimov aka Peter Dimov) Multiple improvements for docs, including links to https://github.com/apolukhin/pfr_non_boost Added misc/strip_boost_namespace.sh script to remove boost:: and BOOST_ prefixes Predef: Version 1.13.1 Fix spelling of "epoch". Add missing parenthesis in sparc.h (from tkoecker). Update documentation to use Rouge code styling and Amber general style. Regex: Breaking Change: Change \B to be the opposite of \b as per Perl behaviour. Change w32_regex_traits.hpp so that windows.h is no longer included. Fxed fuzzing related issues #151, #152, #153, #156. System: Added support for source locations to error_code. Added error_code::to_string, error_condition::to_string, error_code::what. system_error::what() now contains the source location, if present. Added result<T, E = error_code>, a class holding either a value or an error, defined in <boost/system/result.hpp>. Utility: Library documentation converted to QuickBook (thanks to Alan de Freitas, PR#79). Variant2: Added <boost/variant2.hpp>. Added unsafe_get<I>. Added visit_by_index. Added operator<<. Updated Tools Build: Includes release of B2 version 4.7.2. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

New Libraries Describe: A C++14 reflection library, from Peter Dimov. Provides macros for describing enumerators and struct/class members, and primitives for querying this information. ... [More] Lambda2: A C++14, dependency-free, single header lambda library, from Peter Dimov. Allows simple function objects to be constructed via expressions such as _1 + 5, _1 % 2 == 0, _1 > _2, or _1 == ' ' || _1 == '\t'. Updated Libraries Any: Added boost::anys::basic_any - a data type with customizable Small Object Optimization whose instances can hold instances of any type that satisfies ValueType requirements (many thanks to Ruslan Arutyunyan @rarutyun). If you are not sure that you really need it, then use boost::any instead. Started using GithubActions CI for additional testing Asio: Added support for cancellation of individual asynchronous operations. Added the associator trait, used to generically forward associators. Changed all asynchronous operations implemented in Asio to invoke their completion handlers as rvalue references. Added support for asynchronous operations with multiple completion signatures. Added operator&& and operator|| for awaitable<>, to allow coroutines to be trivially awaited in parallel. Added the experimental::as_tuple completion token adapter. Added the experimental::append completion token adapter. Added the experimental::prepend completion token adapter. Added the experimental::deferred completion token, whicih allows deferred execution of asynchronous operations. Added the experimental::parallel_group class and experimental::make_parallel_group function. Added experimental::promise, which allows eager execution and synchronisation of asynchronous operations. Added the experimental::coro class template, a C++20 coroutine primitive with the ability to combine both asynchronous waiting (co_await) and yielding (co_yield). Added move assignment to ssl::stream<>. Changed co_spawn to dispatch the coroutine's initial step to the executor. Enabled additional optimisations for any_executor and any_io_executor when used with asynchronous operations. Added the nodiscard attribute to awaitable<>. Increased the number of cached slots in the default recycling allocator. Changed the default allocator behaviour to respect alignment requirements, to support over-aligned types. Ensured the result strings are always initialised in reverse name resolution. Fixed recursive template instantiation issues in use_awaitable_t::executor_with_default. Fixed the any_io_executor equality operators to correctly return a result based on the target executor. Fixed strand<> to avoid using a potentially moved-from executor. Ensured gcc tests are not used for clang when detecting compiler features. Disabled coroutines support for the clang shipped with MSVC. Fixed compatibility with recent LibreSSL when OPENSSL_NO_SSL_INTERN is defined. Fixed posix::basic_stream_descriptor move operations to work with non-defaulted executors. Consult the Revision History for further details. Atomic: Added make_atomic_ref and make_ipc_atomic_ref factory functions for constructing atomic reference objects. Added C++17 template argument deduction guides for atomic_ref and ipc_atomic_ref to allow omitting template arguments when they can be deduced from constructor arguments. Beast: This maintenance update brings minor bug fixes and updated CI reporting. We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Conversion: boost::implicit_cast is now constexpr (#25). Fixed broken links (PR#23). Started using GithubActions CI for additional testing Core: boost/core/uncaught_exceptions.hpp has been modified for compatibility with Mac OS 10.4 and older. (PR#92) DLL: More runtime checks for malformed ELFs in boost::dll::library_info In boost::dll::library_info use info from .dynsym ELF section if .symtab is empty or missing List protected ELF symbols in boost::dll::library_info as they are available for import (#50) Remove unneeded convert from wchar_t to char on POSIX environment, thanks to Vladislav Shchapov (PR#49) Started using GithubAction CI for additional testing Filesystem: Introducing Boost.Filesystem v4. This new version of the library removes all deprecated features of v3 and also makes a number of breaking API changes intended to make Boost.Filesystem more compatible with std::filesystem introduced in C++17. The differences are described in the release notes and documentation using v3 and v4 tags and are also summarised in a separate section. Users can select Boost.Filesystem version by defining BOOST_FILESYSTEM_VERSION macro to either 3 or 4 when compiling their code. There is no need to separately compile Boost.Filesystem for each library version - a single binary supports both v3 and v4. Users should avoid using both v3 and v4 in the same application as this can lead to subtle bugs. Currently, v3 is the default. In a future release v4 will become the default, and eventually v3 will be removed. v4 is functional, but it is still a work in progress and there may be breaking API changes in the future. v4: path::filename, path::stem and path::extension no longer consider root name or root directory of the path as a filename if the path only consists of those components. For example, on Windows path("C:").filename() used to return "C:" and path("C:\\").filename() used to return "\" and both will return an empty path now. (#88, #194) v4: path::stem and path::extension no longer treat a filename that starts with a dot and has no other dots as an extension. Filenames starting with a dot are commonly treated as filenames with an empty extension. The leading dot is used to indicate a hidden file on most UNIX-like systems. (#88) New: Improved support for various path prefixes on Windows. Added support for local device prefix ("\\.\") and experimental support for NT path prefix ("\??\"). The prefixes will be included in the root name of a path. Note that using the prefixes with Boost.Filesystem v3 can lead to surprising results (e.g. path("\\\\.\\").stem() == "\\\\"). It is recommended to use the prefixes only with Boost.Filesystem v4. Reworked path::lexically_normal implementation to eliminate some cases of duplicate dot (".") elements in the normalized paths. New: Added runtime detection of the statx and getrandom system calls on Linux. This can be useful if the syscall is present at compile time but fails with ENOSYS at run time (for example, in Docker containers that restrict the syscall, even if available on the host). (#172) New: Added support for disabling usage of various system APIs at library build time. This can be useful when a certain API is detected as present by the library configuration scripts but must not be used for some reason (for example, when runtime detection does not work on the target system). See the description of configuration macros in the library documentationfor for more details. New: Added copy_options::synchronize_data and copy_options::synchronize options for the copy_file operation. These options allow to synchronize the written data and attributes with the permanent storage. These options are expensive in terms of performance, but allow to ensure reliability of the copied data. Note that copy_file performed implicit data synchronization on POSIX systems since Boost.Filesystem 1.74.0. This release adds support for more platforms and disables data synchronization by default while allowing the caller to explicitly request it. (#186) Added handling of EINTR error code on POSIX systems for some system calls issued internally. In particular, EINTR could have been ignored on close, which on HP-UX would result in a leaked file descriptor. In the copy_file implementations based on Linux sendfile and copy_file_range system calls, added handling of error codes indicating that a particular filesystem does not support the system call and fall back to the generic read/write loop. This should fix copy_file failing on eCryptFS and possibly other filesystems. (#184) The copy_file_range system call is now used since Linux kernel 4.5, whereas previously it was only enabled since 5.3. The copy_file implementation will fall back to sendfile or read/write loop if copy_file_range fails to copy a given file across filesystems. The copy_file implementations based on Linux sendfile and copy_file_range system calls will not be used on filesystems that are known to contain files with generated content. These system calls are incompatible with such files, and copying them would result in zero-sized files. The generic read/write loop will be used instead. Currently, the blacklisted filesystems are: procfs, sysfs, tracefs and debugfs. In the copy_file implementation based on read/write loop, increased the maximum size of the buffer used for temporary storage and take into account the target filesystem block size for more optimal performance. On Windows CE, calling current_path to obtain the current path for a process will now fail with an error instead of returning successfully with a root path. This platform does not support current directory. Changing the current path was already failing similarly in previous releases of Boost.Filesystem. In canonical, fixed the check for a symlink referencing a directory above root, if an earlier symlink was resolved to an absolute path with a different root from the original path. In canonical, added a limit for the maximum number of symlinks that can be resolved during the call. The limit is currently at least 40 symlinks. On Windows, canonical and weakly_canonical will now use path::preferred_separator for the root directory separator in the resulting paths. This fixes "file not found" errors caused by Windows API not handling generic separators in UNC paths and paths that start with the Win32 filesystem prefix ("\\?\"). (#87, #187) New: Added weakly_canonical overloads taking base path as an argument. On Windows, weakly_canonical no longer fails with an error if the input path contains elements that do not exist in the filesystem but are cancelled by a subsequent dot-dot ("..") element. For example, weakly_canonical("C:\\a\\..") would previously fail if "C:\a" directory did not exist. (#201) In read_symlink on Windows, corrected reparse point handling. The operation would return an empty path for some mount points (for example, created by Box cloud storage driver) and directory junction points that had empty print names. The new implementation now parses substitute name of the reparse point and attempts to reconstruct a Win32 path from it. (#187) On Windows, file streams provided in boost/filesystem/fstream.hpp will use wide character paths on libc++ versions 7.0 and higher, when the standard library supports opening files with wide character paths. (#181) On Windows, creating symlinks should no longer require elevated privileges, if Windows is configured in Developer mode. With some compilers, global objects used internally in Boost.Filesystem are now destroyed after user's global destructors are called. This allows to call Boost.Filesystem methods during the program termination stage. In particular, this concerns the path locale that is used for character code conversion and can be installed by calling path::imbue. The supported compilers include MSVC, GCC and Clang, as well as other compilers that support customizing program initialization order through #pragma section (for MSVC-compatible compilers) or __attribute__ ((init_priority)) (for GCC-compatible compilers). JSON: value_to supports TupleLike types. value_to and value_from support std::array and similar types. Implicit conversion operator from string to std::string_view. std::hash specializations for json types. Fixed allocation errors in object and key_value_pair. Fixed crash when constructing array from a pair of iterators that form an empty range. LexicalCast: Fixed assignment to an int of a floating point value that is out of representable range for int. Started using GithubActions CI for additional testing Log: Fixed compilation for riscv32 target. (PR#150) Mp11: Added mp_intersperse, mp_split, mp_join Multi-index Containers: Maintenance work. PFR: A MurMur Hash based implementation of hash_combine() is now used to reduce collisions count and improve quality of boost::pfr::hash_value() Visual Studio 2017 now supported in C++14 mode (thanks to Denis Mikhailov aka @denzor200) Issues found by inspect tool were fixed Fixed some warnings, including removal of extra semicolons in include/boost/pfr/detail/fields_count.hpp (#72) Added a compile time assert for inherited types (thanks to Denis Mikhailov aka @denzor200) Reflection of aggregates with non movable fields is now possible if guaranteed copy elision is on Fixed spelling issues Started using GithubActions CI for additional testing PropertyTree: This is a maintenance release. Extend compiler coverage in CI. Fix Boost compatibility for CMakeLists.txt. System: The conversion operator from error_category to std::error_category has been improved and no longer requires <map> or <mutex>. The comparison operators of error_category are now inline friends instead of member functions (a side effect of the previous change.) error_condition now defers calling generic_category() to avoid instantiating the object until it's actually needed. error_condition::failed and error_condition::message have been undeprecated, and operator bool() now once again returns failed(). The system category now doesn't call generic_category(), to avoid instantiating the object. The return value of default_error_condition changes in some cases into an error_condition from the generic category, instead of from the system category. This happens on POSIX when the input error_code is from the system category and does not correspond to any errc_t value. The interoperability of error_code and std::error_code has been improved substantially. It is now possible to construct boost::system::error_code from std::error_code, and it's possible to pass boost::system::error_code to functions taking std::error_code&. A stream insertion operator for error_condition has been added. Uuid: Added to_chars for writing uuid strings without allocating (PR#116) Updated Tools Build: Includes release of B2 version 4.6.1. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

New Libraries Describe: A C++14 reflection library, from Peter Dimov. Provides macros for describing enumerators and struct/class members, and primitives for querying this information. ... [More] Lambda2: A C++14, dependency-free, single header lambda library, from Peter Dimov. Allows simple function objects to be constructed via expressions such as _1 + 5, _1 % 2 == 0, _1 > _2, or _1 == ' ' || _1 == '\t'. Updated Libraries Any: Added boost::anys::basic_any - a data type with customizable Small Object Optimization whose instances can hold instances of any type that satisfies ValueType requirements (many thanks to Ruslan Arutyunyan @rarutyun). If you are not sure that you really need it, then use boost::any instead. Started using GithubActions CI for additional testing Asio: Added support for cancellation of individual asynchronous operations. Added the associator trait, used to generically forward associators. Changed all asynchronous operations implemented in Asio to invoke their completion handlers as rvalue references. Added support for asynchronous operations with multiple completion signatures. Added operator&& and operator|| for awaitable<>, to allow coroutines to be trivially awaited in parallel. Added the experimental::as_tuple completion token adapter. Added the experimental::append completion token adapter. Added the experimental::prepend completion token adapter. Added the experimental::deferred completion token, whicih allows deferred execution of asynchronous operations. Added the experimental::parallel_group class and experimental::make_parallel_group function. Added experimental::promise, which allows eager execution and synchronisation of asynchronous operations. Added the experimental::coro class template, a C++20 coroutine primitive with the ability to combine both asynchronous waiting (co_await) and yielding (co_yield). Added move assignment to ssl::stream<>. Changed co_spawn to dispatch the coroutine's initial step to the executor. Enabled additional optimisations for any_executor and any_io_executor when used with asynchronous operations. Added the nodiscard attribute to awaitable<>. Increased the number of cached slots in the default recycling allocator. Changed the default allocator behaviour to respect alignment requirements, to support over-aligned types. Ensured the result strings are always initialised in reverse name resolution. Fixed recursive template instantiation issues in use_awaitable_t::executor_with_default. Fixed the any_io_executor equality operators to correctly return a result based on the target executor. Fixed strand<> to avoid using a potentially moved-from executor. Ensured gcc tests are not used for clang when detecting compiler features. Disabled coroutines support for the clang shipped with MSVC. Fixed compatibility with recent LibreSSL when OPENSSL_NO_SSL_INTERN is defined. Fixed posix::basic_stream_descriptor move operations to work with non-defaulted executors. Consult the Revision History for further details. Atomic: Added make_atomic_ref and make_ipc_atomic_ref factory functions for constructing atomic reference objects. Added C++17 template argument deduction guides for atomic_ref and ipc_atomic_ref to allow omitting template arguments when they can be deduced from constructor arguments. Beast: This maintenance update brings minor bug fixes and updated CI reporting. We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Conversion: boost::implicit_cast is now constexpr (#25). Fixed broken links (PR#23). Started using GithubActions CI for additional testing Core: boost/core/uncaught_exceptions.hpp has been modified for compatibility with Mac OS 10.4 and older. (PR#92) DLL: More runtime checks for malformed ELFs in boost::dll::library_info In boost::dll::library_info use info from .dynsym ELF section if .symtab is empty or missing List protected ELF symbols in boost::dll::library_info as they are available for import (#50) Remove unneeded convert from wchar_t to char on POSIX environment, thanks to Vladislav Shchapov (PR#49) Started using GithubAction CI for additional testing Filesystem: Introducing Boost.Filesystem v4. This new version of the library removes all deprecated features of v3 and also makes a number of breaking API changes intended to make Boost.Filesystem more compatible with std::filesystem introduced in C++17. The differences are described in the release notes and documentation using v3 and v4 tags and are also summarised in a separate section. Users can select Boost.Filesystem version by defining BOOST_FILESYSTEM_VERSION macro to either 3 or 4 when compiling their code. There is no need to separately compile Boost.Filesystem for each library version - a single binary supports both v3 and v4. Users should avoid using both v3 and v4 in the same application as this can lead to subtle bugs. Currently, v3 is the default. In a future release v4 will become the default, and eventually v3 will be removed. v4 is functional, but it is still a work in progress and there may be breaking API changes in the future. v4: path::filename, path::stem and path::extension no longer consider root name or root directory of the path as a filename if the path only consists of those components. For example, on Windows path("C:").filename() used to return "C:" and path("C:\\").filename() used to return "\" and both will return an empty path now. (#88, #194) v4: path::stem and path::extension no longer treat a filename that starts with a dot and has no other dots as an extension. Filenames starting with a dot are commonly treated as filenames with an empty extension. The leading dot is used to indicate a hidden file on most UNIX-like systems. (#88) New: Improved support for various path prefixes on Windows. Added support for local device prefix ("\\.\") and experimental support for NT path prefix ("\??\"). The prefixes will be included in the root name of a path. Note that using the prefixes with Boost.Filesystem v3 can lead to surprising results (e.g. path("\\\\.\\").stem() == "\\\\"). It is recommended to use the prefixes only with Boost.Filesystem v4. Reworked path::lexically_normal implementation to eliminate some cases of duplicate dot (".") elements in the normalized paths. New: Added runtime detection of the statx and getrandom system calls on Linux. This can be useful if the syscall is present at compile time but fails with ENOSYS at run time (for example, in Docker containers that restrict the syscall, even if available on the host). (#172) New: Added support for disabling usage of various system APIs at library build time. This can be useful when a certain API is detected as present by the library configuration scripts but must not be used for some reason (for example, when runtime detection does not work on the target system). See the description of configuration macros in the library documentationfor for more details. New: Added copy_options::synchronize_data and copy_options::synchronize options for the copy_file operation. These options allow to synchronize the written data and attributes with the permanent storage. These options are expensive in terms of performance, but allow to ensure reliability of the copied data. Note that copy_file performed implicit data synchronization on POSIX systems since Boost.Filesystem 1.74.0. This release adds support for more platforms and disables data synchronization by default while allowing the caller to explicitly request it. (#186) Added handling of EINTR error code on POSIX systems for some system calls issued internally. In particular, EINTR could have been ignored on close, which on HP-UX would result in a leaked file descriptor. In the copy_file implementations based on Linux sendfile and copy_file_range system calls, added handling of error codes indicating that a particular filesystem does not support the system call and fall back to the generic read/write loop. This should fix copy_file failing on eCryptFS and possibly other filesystems. (#184) The copy_file_range system call is now used since Linux kernel 4.5, whereas previously it was only enabled since 5.3. The copy_file implementation will fall back to sendfile or read/write loop if copy_file_range fails to copy a given file across filesystems. The copy_file implementations based on Linux sendfile and copy_file_range system calls will not be used on filesystems that are known to contain files with generated content. These system calls are incompatible with such files, and copying them would result in zero-sized files. The generic read/write loop will be used instead. Currently, the blacklisted filesystems are: procfs, sysfs, tracefs and debugfs. In the copy_file implementation based on read/write loop, increased the maximum size of the buffer used for temporary storage and take into account the target filesystem block size for more optimal performance. On Windows CE, calling current_path to obtain the current path for a process will now fail with an error instead of returning successfully with a root path. This platform does not support current directory. Changing the current path was already failing similarly in previous releases of Boost.Filesystem. In canonical, fixed the check for a symlink referencing a directory above root, if an earlier symlink was resolved to an absolute path with a different root from the original path. In canonical, added a limit for the maximum number of symlinks that can be resolved during the call. The limit is currently at least 40 symlinks. On Windows, canonical and weakly_canonical will now use path::preferred_separator for the root directory separator in the resulting paths. This fixes "file not found" errors caused by Windows API not handling generic separators in UNC paths and paths that start with the Win32 filesystem prefix ("\\?\"). (#87, #187) New: Added weakly_canonical overloads taking base path as an argument. On Windows, weakly_canonical no longer fails with an error if the input path contains elements that do not exist in the filesystem but are cancelled by a subsequent dot-dot ("..") element. For example, weakly_canonical("C:\\a\\..") would previously fail if "C:\a" directory did not exist. (#201) In read_symlink on Windows, corrected reparse point handling. The operation would return an empty path for some mount points (for example, created by Box cloud storage driver) and directory junction points that had empty print names. The new implementation now parses substitute name of the reparse point and attempts to reconstruct a Win32 path from it. (#187) On Windows, file streams provided in boost/filesystem/fstream.hpp will use wide character paths on libc++ versions 7.0 and higher, when the standard library supports opening files with wide character paths. (#181) On Windows, creating symlinks should no longer require elevated privileges, if Windows is configured in Developer mode. With some compilers, global objects used internally in Boost.Filesystem are now destroyed after user's global destructors are called. This allows to call Boost.Filesystem methods during the program termination stage. In particular, this concerns the path locale that is used for character code conversion and can be installed by calling path::imbue. The supported compilers include MSVC, GCC and Clang, as well as other compilers that support customizing program initialization order through #pragma section (for MSVC-compatible compilers) or __attribute__ ((init_priority)) (for GCC-compatible compilers). Geometry: Improvements PR#812 Umbrella strategies for distance and comparable_distance (undocumented for now). PR#840 Umbrella strategies for various algorithms (undocumented for now). PR#850 Introduced DynamicGeometry and GeometryCollection concepts and support in some algorithms (undocumented for now). PR#855 Various improvements related to strategies. Default strategies are now included with algorithms. Solved issues #865 Exception thrown in rtree serialization. #439 Invalid box spherical area computation. #838 Invalid result of union_(). #851 Invalid geographic disjoint segment/box result. #861 Invalid result of intersection(). Bugfixes PR#832 Fixed box spherical and geographic area computation. PR#853 Fixed geographic disjoint segment/box. PR#866 Fixed serialization of rtree containing lesser number of elements in root node than minimum. PR#886 Fixed knn rtree query bug causing it to be slow for big k. Various fixes in set operations and buffer. JSON: value_to supports TupleLike types. value_to and value_from support std::array and similar types. Implicit conversion operator from string to std::string_view. std::hash specializations for json types. Fixed allocation errors in object and key_value_pair. Fixed crash when constructing array from a pair of iterators that form an empty range. LexicalCast: Fixed assignment to an int of a floating point value that is out of representable range for int. Started using GithubActions CI for additional testing Log: Fixed compilation for riscv32 target. (PR#150) Mp11: Added mp_intersperse, mp_split, mp_join Multi-index Containers: Maintenance work. PFR: A MurMur Hash based implementation of hash_combine() is now used to reduce collisions count and improve quality of boost::pfr::hash_value() Visual Studio 2017 now supported in C++14 mode (thanks to Denis Mikhailov aka @denzor200) Issues found by inspect tool were fixed Fixed some warnings, including removal of extra semicolons in include/boost/pfr/detail/fields_count.hpp (#72) Added a compile time assert for inherited types (thanks to Denis Mikhailov aka @denzor200) Reflection of aggregates with non movable fields is now possible if guaranteed copy elision is on Fixed spelling issues Started using GithubActions CI for additional testing PropertyTree: This is a maintenance release. Extend compiler coverage in CI. Fix Boost compatibility for CMakeLists.txt. System: The conversion operator from error_category to std::error_category has been improved and no longer requires <map> or <mutex>. The comparison operators of error_category are now inline friends instead of member functions (a side effect of the previous change.) error_condition now defers calling generic_category() to avoid instantiating the object until it's actually needed. error_condition::failed and error_condition::message have been undeprecated, and operator bool() now once again returns failed(). The system category now doesn't call generic_category(), to avoid instantiating the object. The return value of default_error_condition changes in some cases into an error_condition from the generic category, instead of from the system category. This happens on POSIX when the input error_code is from the system category and does not correspond to any errc_t value. The interoperability of error_code and std::error_code has been improved substantially. It is now possible to construct boost::system::error_code from std::error_code, and it's possible to pass boost::system::error_code to functions taking std::error_code&. A stream insertion operator for error_condition has been added. Uuid: Added to_chars for writing uuid strings without allocating (PR#116) Updated Tools Build: Includes release of B2 version 4.6.1. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

New Libraries Describe: A C++14 reflection library, from Peter Dimov. Provides macros for describing enumerators and struct/class members, and primitives for querying this information. ... [More] Lambda2: A C++14, dependency-free, single header lambda library, from Peter Dimov. Allows simple function objects to be constructed via expressions such as _1 + 5, _1 % 2 == 0, _1 > _2, or _1 == ' ' || _1 == '\t'. Updated Libraries Any: Added boost::anys::basic_any - a data type with customizable Small Object Optimization whose instances can hold instances of any type that satisfies ValueType requirements (many thanks to Ruslan Arutyunyan @rarutyun). If you are not sure that you really need it, then use boost::any instead. Started using GithubActions CI for additional testing Asio: Added support for cancellation of individual asynchronous operations. Added the associator trait, used to generically forward associators. Changed all asynchronous operations implemented in Asio to invoke their completion handlers as rvalue references. Added support for asynchronous operations with multiple completion signatures. Added operator&& and operator|| for awaitable<>, to allow coroutines to be trivially awaited in parallel. Added the experimental::as_tuple completion token adapter. Added the experimental::append completion token adapter. Added the experimental::prepend completion token adapter. Added the experimental::deferred completion token, whicih allows deferred execution of asynchronous operations. Added the experimental::parallel_group class and experimental::make_parallel_group function. Added experimental::promise, which allows eager execution and synchronisation of asynchronous operations. Added the experimental::coro class template, a C++20 coroutine primitive with the ability to combine both asynchronous waiting (co_await) and yielding (co_yield). Added move assignment to ssl::stream<>. Changed co_spawn to dispatch the coroutine's initial step to the executor. Enabled additional optimisations for any_executor and any_io_executor when used with asynchronous operations. Added the nodiscard attribute to awaitable<>. Increased the number of cached slots in the default recycling allocator. Changed the default allocator behaviour to respect alignment requirements, to support over-aligned types. Ensured the result strings are always initialised in reverse name resolution. Fixed recursive template instantiation issues in use_awaitable_t::executor_with_default. Fixed the any_io_executor equality operators to correctly return a result based on the target executor. Fixed strand<> to avoid using a potentially moved-from executor. Ensured gcc tests are not used for clang when detecting compiler features. Disabled coroutines support for the clang shipped with MSVC. Fixed compatibility with recent LibreSSL when OPENSSL_NO_SSL_INTERN is defined. Fixed posix::basic_stream_descriptor move operations to work with non-defaulted executors. Consult the Revision History for further details. Atomic: Added make_atomic_ref and make_ipc_atomic_ref factory functions for constructing atomic reference objects. Added C++17 template argument deduction guides for atomic_ref and ipc_atomic_ref to allow omitting template arguments when they can be deduced from constructor arguments. Beast: This maintenance update brings minor bug fixes and updated CI reporting. We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Conversion: boost::implicit_cast is now constexpr (#25). Fixed broken links (PR#23). Started using GithubActions CI for additional testing Core: boost/core/uncaught_exceptions.hpp has been modified for compatibility with Mac OS 10.4 and older. (PR#92) DLL: More runtime checks for malformed ELFs in boost::dll::library_info In boost::dll::library_info use info from .dynsym ELF section if .symtab is empty or missing List protected ELF symbols in boost::dll::library_info as they are available for import (#50) Remove unneeded convert from wchar_t to char on POSIX environment, thanks to Vladislav Shchapov (PR#49) Started using GithubAction CI for additional testing Filesystem: Introducing Boost.Filesystem v4. This new version of the library removes all deprecated features of v3 and also makes a number of breaking API changes intended to make Boost.Filesystem more compatible with std::filesystem introduced in C++17. The differences are described in the release notes and documentation using v3 and v4 tags and are also summarised in a separate section. Users can select Boost.Filesystem version by defining BOOST_FILESYSTEM_VERSION macro to either 3 or 4 when compiling their code. There is no need to separately compile Boost.Filesystem for each library version - a single binary supports both v3 and v4. Users should avoid using both v3 and v4 in the same application as this can lead to subtle bugs. Currently, v3 is the default. In a future release v4 will become the default, and eventually v3 will be removed. v4 is functional, but it is still a work in progress and there may be breaking API changes in the future. v4: path::filename, path::stem and path::extension no longer consider root name or root directory of the path as a filename if the path only consists of those components. For example, on Windows path("C:").filename() used to return "C:" and path("C:\\").filename() used to return "" and both will return an empty path now. (#88, #194) v4: path::stem and path::extension no longer treat a filename that starts with a dot and has no other dots as an extension. Filenames starting with a dot are commonly treated as filenames with an empty extension. The leading dot is used to indicate a hidden file on most UNIX-like systems. (#88) New: Improved support for various path prefixes on Windows. Added support for local device prefix ("\.") and experimental support for NT path prefix ("??"). The prefixes will be included in the root name of a path. Note that using the prefixes with Boost.Filesystem v3 can lead to surprising results (e.g. path("\\\\.\\").stem() == "\\\\"). It is recommended to use the prefixes only with Boost.Filesystem v4. Reworked path::lexically_normal implementation to eliminate some cases of duplicate dot (".") elements in the normalized paths. New: Added runtime detection of the statx and getrandom system calls on Linux. This can be useful if the syscall is present at compile time but fails with ENOSYS at run time (for example, in Docker containers that restrict the syscall, even if available on the host). (#172) New: Added support for disabling usage of various system APIs at library build time. This can be useful when a certain API is detected as present by the library configuration scripts but must not be used for some reason (for example, when runtime detection does not work on the target system). See the description of configuration macros in the library documentationfor for more details. New: Added copy_options::synchronize_data and copy_options::synchronize options for the copy_file operation. These options allow to synchronize the written data and attributes with the permanent storage. These options are expensive in terms of performance, but allow to ensure reliability of the copied data. Note that copy_file performed implicit data synchronization on POSIX systems since Boost.Filesystem 1.74.0. This release adds support for more platforms and disables data synchronization by default while allowing the caller to explicitly request it. (#186) Added handling of EINTR error code on POSIX systems for some system calls issued internally. In particular, EINTR could have been ignored on close, which on HP-UX would result in a leaked file descriptor. In the copy_file implementations based on Linux sendfile and copy_file_range system calls, added handling of error codes indicating that a particular filesystem does not support the system call and fall back to the generic read/write loop. This should fix copy_file failing on eCryptFS and possibly other filesystems. (#184) The copy_file_range system call is now used since Linux kernel 4.5, whereas previously it was only enabled since 5.3. The copy_file implementation will fall back to sendfile or read/write loop if copy_file_range fails to copy a given file across filesystems. The copy_file implementations based on Linux sendfile and copy_file_range system calls will not be used on filesystems that are known to contain files with generated content. These system calls are incompatible with such files, and copying them would result in zero-sized files. The generic read/write loop will be used instead. Currently, the blacklisted filesystems are: procfs, sysfs, tracefs and debugfs. In the copy_file implementation based on read/write loop, increased the maximum size of the buffer used for temporary storage and take into account the target filesystem block size for more optimal performance. On Windows CE, calling current_path to obtain the current path for a process will now fail with an error instead of returning successfully with a root path. This platform does not support current directory. Changing the current path was already failing similarly in previous releases of Boost.Filesystem. In canonical, fixed the check for a symlink referencing a directory above root, if an earlier symlink was resolved to an absolute path with a different root from the original path. In canonical, added a limit for the maximum number of symlinks that can be resolved during the call. The limit is currently at least 40 symlinks. On Windows, canonical and weakly_canonical will now use path::preferred_separator for the root directory separator in the resulting paths. This fixes "file not found" errors caused by Windows API not handling generic separators in UNC paths and paths that start with the Win32 filesystem prefix ("\?"). (#87, #187) New: Added weakly_canonical overloads taking base path as an argument. On Windows, weakly_canonical no longer fails with an error if the input path contains elements that do not exist in the filesystem but are cancelled by a subsequent dot-dot ("..") element. For example, weakly_canonical("C:\\a\\..") would previously fail if "C:\a" directory did not exist. (#201) In read_symlink on Windows, corrected reparse point handling. The operation would return an empty path for some mount points (for example, created by Box cloud storage driver) and directory junction points that had empty print names. The new implementation now parses substitute name of the reparse point and attempts to reconstruct a Win32 path from it. (#187) On Windows, file streams provided in boost/filesystem/fstream.hpp will use wide character paths on libc++ versions 7.0 and higher, when the standard library supports opening files with wide character paths. (#181) On Windows, creating symlinks should no longer require elevated privileges, if Windows is configured in Developer mode. With some compilers, global objects used internally in Boost.Filesystem are now destroyed after user's global destructors are called. This allows to call Boost.Filesystem methods during the program termination stage. In particular, this concerns the path locale that is used for character code conversion and can be installed by calling path::imbue. The supported compilers include MSVC, GCC and Clang, as well as other compilers that support customizing program initialization order through #pragma section (for MSVC-compatible compilers) or __attribute__ ((init_priority)) (for GCC-compatible compilers). JSON: value_to supports TupleLike types. value_to and value_from support std::array and similar types. Implicit conversion operator from string to std::string_view. std::hash specializations for json types. Fixed allocation errors in object and key_value_pair. Fixed crash when constructing array from a pair of iterators that form an empty range. LexicalCast: Fixed assignment to an int of a floating point value that is out of representable range for int. Started using GithubActions CI for additional testing Log: Fixed compilation for riscv32 target. (PR#150) Mp11: Added mp_intersperse, mp_split, mp_join Multi-index Containers: Maintenance work. PFR: A MurMur Hash based implementation of hash_combine() is now used to reduce collisions count and improve quality of boost::pfr::hash_value() Visual Studio 2017 now supported in C++14 mode (thanks to Denis Mikhailov aka @denzor200) Issues found by inspect tool were fixed Fixed some warnings, including removal of extra semicolons in include/boost/pfr/detail/fields_count.hpp (#72) Added a compile time assert for inherited types (thanks to Denis Mikhailov aka @denzor200) Reflection of aggregates with non movable fields is now possible if guaranteed copy elision is on Fixed spelling issues Started using GithubActions CI for additional testing PropertyTree: This is a maintenance release. Extend compiler coverage in CI. Fix Boost compatibility for CMakeLists.txt. System: The conversion operator from error_category to std::error_category has been improved and no longer requires <map> or <mutex>. The comparison operators of error_category are now inline friends instead of member functions (a side effect of the previous change.) error_condition now defers calling generic_category() to avoid instantiating the object until it's actually needed. error_condition::failed and error_condition::message have been undeprecated, and operator bool() now once again returns failed(). The system category now doesn't call generic_category(), to avoid instantiating the object. The return value of default_error_condition changes in some cases into an error_condition from the generic category, instead of from the system category. This happens on POSIX when the input error_code is from the system category and does not correspond to any errc_t value. The interoperability of error_code and std::error_code has been improved substantially. It is now possible to construct boost::system::error_code from std::error_code, and it's possible to pass boost::system::error_code to functions taking std::error_code&. A stream insertion operator for error_condition has been added. Uuid: Added to_chars for writing uuid strings without allocating (PR#116) Updated Tools Build: Includes release of B2 version 4.6.1. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Boost's additional test compilers include: Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]

New Libraries Describe: A C++14 reflection library, from Peter Dimov. Provides macros for describing enumerators and struct/class members, and primitives for querying this information. ... [More] Lambda2: A C++14, dependency-free, single header lambda library, from Peter Dimov. Allows simple function objects to be constructed via expressions such as _1 + 5, _1 % 2 == 0, _1 > _2, or _1 == ' ' || _1 == '\t'. Updated Libraries Any: Added boost::anys::basic_any - a data type with customizable Small Object Optimization whose instances can hold instances of any type that satisfies ValueType requirements (many thanks to Ruslan Arutyunyan @rarutyun). If you are not sure that you really need it, then use boost::any instead. Started using GithubActions CI for additional testing Asio: Added support for cancellation of individual asynchronous operations. Added the associator trait, used to generically forward associators. Changed all asynchronous operations implemented in Asio to invoke their completion handlers as rvalue references. Added support for asynchronous operations with multiple completion signatures. Added operator&& and operator|| for awaitable<>, to allow coroutines to be trivially awaited in parallel. Added the experimental::as_tuple completion token adapter. Added the experimental::append completion token adapter. Added the experimental::prepend completion token adapter. Added the experimental::deferred completion token, whicih allows deferred execution of asynchronous operations. Added the experimental::parallel_group class and experimental::make_parallel_group function. Added experimental::promise, which allows eager execution and synchronisation of asynchronous operations. Added the experimental::coro class template, a C++20 coroutine primitive with the ability to combine both asynchronous waiting (co_await) and yielding (co_yield). Added move assignment to ssl::stream<>. Changed co_spawn to dispatch the coroutine's initial step to the executor. Enabled additional optimisations for any_executor and any_io_executor when used with asynchronous operations. Added the nodiscard attribute to awaitable<>. Increased the number of cached slots in the default recycling allocator. Changed the default allocator behaviour to respect alignment requirements, to support over-aligned types. Ensured the result strings are always initialised in reverse name resolution. Fixed recursive template instantiation issues in use_awaitable_t::executor_with_default. Fixed the any_io_executor equality operators to correctly return a result based on the target executor. Fixed strand<> to avoid using a potentially moved-from executor. Ensured gcc tests are not used for clang when detecting compiler features. Disabled coroutines support for the clang shipped with MSVC. Fixed compatibility with recent LibreSSL when OPENSSL_NO_SSL_INTERN is defined. Fixed posix::basic_stream_descriptor move operations to work with non-defaulted executors. Consult the Revision History for further details. Atomic: Added make_atomic_ref and make_ipc_atomic_ref factory functions for constructing atomic reference objects. Added C++17 template argument deduction guides for atomic_ref and ipc_atomic_ref to allow omitting template arguments when they can be deduced from constructor arguments. Beast: This maintenance update brings minor bug fixes and updated CI reporting. We'd love to know how you or your company use Beast, consider adding an entry to the Companies and Individuals Using Beast list. See the full Release Notes for a complete list of changes. Conversion: boost::implicit_cast is now constexpr (#25). Fixed broken links (PR#23). Started using GithubActions CI for additional testing Core: boost/core/uncaught_exceptions.hpp has been modified for compatibility with Mac OS 10.4 and older. (PR#92) DLL: More runtime checks for malformed ELFs in boost::dll::library_info In boost::dll::library_info use info from .dynsym ELF section if .symtab is empty or missing List protected ELF symbols in boost::dll::library_info as they are available for import (#50) Remove unneeded convert from wchar_t to char on POSIX environment, thanks to Vladislav Shchapov (PR#49) Started using GithubAction CI for additional testing Filesystem: Introducing Boost.Filesystem v4. This new version of the library removes all deprecated features of v3 and also makes a number of breaking API changes intended to make Boost.Filesystem more compatible with std::filesystem introduced in C++17. The differences are described in the release notes and documentation using v3 and v4 tags and are also summarised in a separate section. Users can select Boost.Filesystem version by defining BOOST_FILESYSTEM_VERSION macro to either 3 or 4 when compiling their code. There is no need to separately compile Boost.Filesystem for each library version - a single binary supports both v3 and v4. Users should avoid using both v3 and v4 in the same application as this can lead to subtle bugs. Currently, v3 is the default. In a future release v4 will become the default, and eventually v3 will be removed. v4 is functional, but it is still a work in progress and there may be breaking API changes in the future. v4: path::filename, path::stem and path::extension no longer consider root name or root directory of the path as a filename if the path only consists of those components. For example, on Windows path("C:").filename() used to return "C:" and path("C:\\").filename() used to return "\" and both will return an empty path now. (#88, #194) v4: path::stem and path::extension no longer treat a filename that starts with a dot and has no other dots as an extension. Filenames starting with a dot are commonly treated as filenames with an empty extension. The leading dot is used to indicate a hidden file on most UNIX-like systems. (#88) New: Improved support for various path prefixes on Windows. Added support for local device prefix ("\\.\") and experimental support for NT path prefix ("\??\"). The prefixes will be included in the root name of a path. Note that using the prefixes with Boost.Filesystem v3 can lead to surprising results (e.g. path("\\\\.\\").stem() == "\\\\"). It is recommended to use the prefixes only with Boost.Filesystem v4. Reworked path::lexically_normal implementation to eliminate some cases of duplicate dot (".") elements in the normalized paths. New: Added runtime detection of the statx and getrandom system calls on Linux. This can be useful if the syscall is present at compile time but fails with ENOSYS at run time (for example, in Docker containers that restrict the syscall, even if available on the host). (#172) New: Added support for disabling usage of various system APIs at library build time. This can be useful when a certain API is detected as present by the library configuration scripts but must not be used for some reason (for example, when runtime detection does not work on the target system). See the description of configuration macros in the library documentationfor for more details. New: Added copy_options::synchronize_data and copy_options::synchronize options for the copy_file operation. These options allow to synchronize the written data and attributes with the permanent storage. These options are expensive in terms of performance, but allow to ensure reliability of the copied data. Note that copy_file performed implicit data synchronization on POSIX systems since Boost.Filesystem 1.74.0. This release adds support for more platforms and disables data synchronization by default while allowing the caller to explicitly request it. (#186) Added handling of EINTR error code on POSIX systems for some system calls issued internally. In particular, EINTR could have been ignored on close, which on HP-UX would result in a leaked file descriptor. In the copy_file implementations based on Linux sendfile and copy_file_range system calls, added handling of error codes indicating that a particular filesystem does not support the system call and fall back to the generic read/write loop. This should fix copy_file failing on eCryptFS and possibly other filesystems. (#184) The copy_file_range system call is now used since Linux kernel 4.5, whereas previously it was only enabled since 5.3. The copy_file implementation will fall back to sendfile or read/write loop if copy_file_range fails to copy a given file across filesystems. The copy_file implementations based on Linux sendfile and copy_file_range system calls will not be used on filesystems that are known to contain files with generated content. These system calls are incompatible with such files, and copying them would result in zero-sized files. The generic read/write loop will be used instead. Currently, the blacklisted filesystems are: procfs, sysfs, tracefs and debugfs. In the copy_file implementation based on read/write loop, increased the maximum size of the buffer used for temporary storage and take into account the target filesystem block size for more optimal performance. On Windows CE, calling current_path to obtain the current path for a process will now fail with an error instead of returning successfully with a root path. This platform does not support current directory. Changing the current path was already failing similarly in previous releases of Boost.Filesystem. In canonical, fixed the check for a symlink referencing a directory above root, if an earlier symlink was resolved to an absolute path with a different root from the original path. In canonical, added a limit for the maximum number of symlinks that can be resolved during the call. The limit is currently at least 40 symlinks. On Windows, canonical and weakly_canonical will now use path::preferred_separator for the root directory separator in the resulting paths. This fixes "file not found" errors caused by Windows API not handling generic separators in UNC paths and paths that start with the Win32 filesystem prefix ("\\?\"). (#87, #187) New: Added weakly_canonical overloads taking base path as an argument. On Windows, weakly_canonical no longer fails with an error if the input path contains elements that do not exist in the filesystem but are cancelled by a subsequent dot-dot ("..") element. For example, weakly_canonical("C:\\a\\..") would previously fail if "C:\a" directory did not exist. (#201) In read_symlink on Windows, corrected reparse point handling. The operation would return an empty path for some mount points (for example, created by Box cloud storage driver) and directory junction points that had empty print names. The new implementation now parses substitute name of the reparse point and attempts to reconstruct a Win32 path from it. (#187) On Windows, file streams provided in boost/filesystem/fstream.hpp will use wide character paths on libc++ versions 7.0 and higher, when the standard library supports opening files with wide character paths. (#181) On Windows, creating symlinks should no longer require elevated privileges, if Windows is configured in Developer mode. With some compilers, global objects used internally in Boost.Filesystem are now destroyed after user's global destructors are called. This allows to call Boost.Filesystem methods during the program termination stage. In particular, this concerns the path locale that is used for character code conversion and can be installed by calling path::imbue. The supported compilers include MSVC, GCC and Clang, as well as other compilers that support customizing program initialization order through #pragma section (for MSVC-compatible compilers) or __attribute__ ((init_priority)) (for GCC-compatible compilers). JSON: value_to supports TupleLike types. value_to and value_from support std::array and similar types. Implicit conversion operator from string to std::string_view. std::hash specializations for json types. Fixed allocation errors in object and key_value_pair. Fixed crash when constructing array from a pair of iterators that form an empty range. LexicalCast: Fixed assignment to an int of a floating point value that is out of representable range for int. Started using GithubActions CI for additional testing Log: Fixed compilation for riscv32 target. (PR#150) Mp11: Added mp_intersperse, mp_split, mp_join Multi-index Containers: Maintenance work. PFR: A MurMur Hash based implementation of hash_combine() is now used to reduce collisions count and improve quality of boost::pfr::hash_value() Visual Studio 2017 now supported in C++14 mode (thanks to Denis Mikhailov aka @denzor200) Issues found by inspect tool were fixed Fixed some warnings, including removal of extra semicolons in include/boost/pfr/detail/fields_count.hpp (#72) Added a compile time assert for inherited types (thanks to Denis Mikhailov aka @denzor200) Reflection of aggregates with non movable fields is now possible if guaranteed copy elision is on Fixed spelling issues Started using GithubActions CI for additional testing PropertyTree: This is a maintenance release. Extend compiler coverage in CI. Fix Boost compatibility for CMakeLists.txt. System: The conversion operator from error_category to std::error_category has been improved and no longer requires <map> or <mutex>. The comparison operators of error_category are now inline friends instead of member functions (a side effect of the previous change.) error_condition now defers calling generic_category() to avoid instantiating the object until it's actually needed. error_condition::failed and error_condition::message have been undeprecated, and operator bool() now once again returns failed(). The system category now doesn't call generic_category(), to avoid instantiating the object. The return value of default_error_condition changes in some cases into an error_condition from the generic category, instead of from the system category. This happens on POSIX when the input error_code is from the system category and does not correspond to any errc_t value. The interoperability of error_code and std::error_code has been improved substantially. It is now possible to construct boost::system::error_code from std::error_code, and it's possible to pass boost::system::error_code to functions taking std::error_code&. A stream insertion operator for error_condition has been added. Uuid: Added to_chars for writing uuid strings without allocating (PR#116) Updated Tools Build: Includes release of B2 version 4.6.1. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0 Clang, C++11: 3.4, 11.0.0 Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0 Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0 Clang, C++20: 11.0.0, 12.0.0, 13.0.0 GCC: 4.6.3, 11 GCC, C++11: 4.7.3, 4.8.5, 11 GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11 GCC, C++20: 8.0.1, 9.1.0, 10, 11 OS X: Apple Clang: 11.0.3 Apple Clang, C++11: 11.0.3 Apple Clang, C++14: 11.0.3 Apple Clang, C++17: 11.0.3 Apple Clang, C++20: 11.0.3 Windows: Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2 Boost's additional test compilers include: Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. [Less]