New Libraries

• Charconv: A high quality implementation of <charconv> in C++11, from Matt Borland.
• Scope: A collection of scope guard utilities and a unique_resource wrapper, from Andrey Semashev.

Updated Libraries

• Asio:

  • Fixed the async_result primary template's concept checking to correctly handle lvalue-qualified completion signatures.
  • Fixed some compile errors that could arise when using the bind_allocator, bind_executor, bind_immediate_executor and bind_cancellation_slot completion token adapters to adapt each other.
  • Changed the experimental::ranged_parallel_group operation so that it moves the completion_order vector when invoking the completion handler.
  • Fixed some warnings about deprecated implicit copy constructors on ip::basic_resolver_query, io_context::strand, and coroutine.
  • Updated the version specification used to initialise Winsock.
  • Fixed co_spawn to correctly propagate exceptions resulting from cancellation to the completion handler.
  • Added calls to std::launder to fix undefined behaviour in awaitable<> internal storage.
  • Added missing handling of the file_base::append flag in the Windows implementation of file support.
  • Updated the socket and descriptor implementations to add more cases where they will fall back to fcntl if a call to ioctl fails.
  • Fixed the boost/asio/experimental/parallel_group.hpp header so that it is self-contained.
  • Fixed a compile error that occurred when channels and experimental::coro were both used in the same translation unit.
  • Added missing CancellationSlot type requirements to documentation.
  • Fixed the documentation hyperlinks for the deduced return types of asynchronous operations' initiating functions.
  • Other minor documentation updates.
• Atomic:

  • Added support for pause instruction on RISC-V. (PR#65)
• Beast:

  • API Changes

    • The status code list has been updated to conform with the IANA registry.
  • Fixes

    • Unreachable code warning in buffers_cat.hpp.
    • Connection error handling in websocker_server_awaitable example.
    • Concurrent calls to async_write in advanced server examples.
    • zlib name conflicts with minizip.
    • host string should be updated after SSL_set_tlsext_host_name().
  • Improvements

    • asio::associator is specialized for bind_wrapper and bind_front_wrapper.
    • Add non-allocating overload for error category message function.
  • Documentation

    • Specifies when calling http::message::prepare_payload() is optional.
    • Operations affected by basic_stream::expires_after().
    • teardown() and async_teardown() are customization points.
    • Moving or copying http::serializer after first usage is undefined behaviour.
    • websocket::permessage_deflate should be configured before performing the WebSocket handshake.
    • bytes_transferred in http reads operations reports the number of bytes consumed by the HTTP parser.
  • Acknowledgements

    • Emile Cormier, JohannesWilde, yhzx233
• Bimap:

  • Fixed heterogeneous lookup for side collections (PR#42).
• Bind:

  • C++03 is no longer supported; a C++11 compiler is required. (This includes GCC 4.7 or later, and MSVC 12.0 (VS 2013) or later.)
• Conversion:

  • Removed outdated mentions of boost::lexical_cast that is not part of the library any more. Thanks to Danil Sidoruk for the PR PR#28!
• Core:

  • Added a new boost/core/functor.hpp header with a functor class template for wrapping a raw function into a function object class.
  • Changed null_deleter, fclose_deleter and checked deleter definitions so that they don't bring namespace boost into argument-dependent lookup. Users may need to either explicitly qualify the namespace of the called function or add a using-declaration.
• Filesystem:

  • path::generic_path and path::generic_string methods now remove duplicate directory separators in the returned paths.
  • v4: path::generic_path, path::generic_string, path::make_preferred and path::lexically_normal avoid converting between backslashes and forward slashes in path root names. For example, on Windows, path("\\\\\\\\?\\\\c:\\\\foo").generic_string() now returns "\\?\c:/foo" instead of "//?/c:/foo". Similarly, path("\\\\\\\\host/share/foo/..").lexically_normal() now returns "\\host\share".
  • v4: equivalent now indicates error if either one of the paths doesn't exist.
  • v4: absolute now returns a path with a trailing directory separator when the input path has an empty relative_path(). (#301)
  • Added a unique_path overload taking a single error_code& ec argument. The overload generates a unique path using the default path model.
  • weakly_canonical now produces an absolute path if the input path is relative and contains no elements that exist in the filesystem. (#300)
  • Added a new copy_options::ignore_attribute_errors option for copy_file and copy operations. The new option allows to ignore possible errors while copying file attributes. (#179)
  • On Linux, copy_file backends based on sendfile and copy_file_range system calls will attempt to preallocate storage for the target file. This may reduce filesystem fragmentation and provide early error indication if there is not enough free space. Not all filesystems support this feature; file copying proceeds if storage preallocation is not supported.
  • On POSIX systems that support fdopendir, openat and related APIs defined in POSIX.1-2008, as well as on Windows, recursive_directory_iterator now uses file descriptors/handles instead of paths to query the file statuses and open nested directories during iteration. This makes directory iteration more resilient to concurrent modifications of the filesystem.
  • Removed APIs that were previously declared deprecated. In particular, path and recursive_directory_iterator member functions, is_regular, copy_directory, symbolic_link_exists, complete, copy_option, symlink_option, as well as boost/filesystem/convenience.hpp and boost/filesystem/path_traits.hpp headers were removed. Possible replacements for the removed components are mentioned in the documentation.
  • Support for path construction, assignment and appending from container types (e.g. std::vector<char>) is now disabled by default. Users can still enable this functionality by defining BOOST_FILESYSTEM_DEPRECATED. This functionality remains deprecated and will be completely removed in a future release.
• Function:

  • C++03 is no longer supported; a C++11 compiler is required. (This includes GCC 4.7 or later, and MSVC 12.0 (VS 2013) or later.)
• Geometry:

  • Improvements

    • PR#1247 Use if constexpr macro instead of condition macro
    • PR#1242 Pass strategy to sort by side
    • PR#1234 Add cmake files for clang/mac/darwin/arm64
  • Solved issues

    • #1231, #1244 Fix invalid set operations for CCW polygons
    • #1259 Fix compilation error with CUDA NVCC compiler
    • #1250 Fix buffer of linestring returning incorrect inner polygon
    • #1230 Fix union operation perturbing a point and returning wrong result
    • #1229 Fix union producing self intersections
    • PR#1248 Fix buffer issue by setting turns in closed clusters as non traversable
    • PR#1246 Fix compilation of converter and is_base_of
    • Various fixes of errors and warnings
• Iterator:

  • Support for C++03 is deprecated and will be removed in a future release.
• JSON:

  • Boost.Endian is now used to deal with endianness.
  • Aliases to Boost.System and Boost.Container components are deprecated and will be completely removed in 1.87.0.
  • Conversion of described classes supports private members.
  • Rvalue reference overload for visit.
  • Add conversion support for path-like types.
  • Parsing into described classes correctly considers inherited members.
  • Conversion of self-referential sequences is disabled.
  • Fixed reference handling in visit.
• LEAF:

  • New API for transporting of error objects and exceptions between threads: try_capture_all.
  • result<T> able to transport exceptions captured via try_capture_all.
  • result<T> transporting dynamically captured error objects with improved efficiency.
  • Old make_shared_context/capture APIs are deprecated, will be removed in the next release.
  • Removed support for transporting of dynamicaly captured error objects in exceptions.
• LexicalCast:

  • Significant rewrite of the internal logic to separate optimized and C++ Standard Library IO-based streams:

    • C++ Standard Library based streams now constructed in less cases leading to better performance;
    • less template instantiations and simpler code;
    • always use std::char_traits (do not use custom traits from input/output types as it leads to linktime or runtime errors);
    • fixed missuse of forward declared boost::array (thanks to 13steinj for the report #64!);
    • support for volatile input types was dropped, following the C++ Standard Library trend.
  • Optimized conversions from std::basic_string_view and boost::basic_string_view #30.
  • Dropped dependency on Boost.NumericConversion and Boost.MPL. Fixed some cases of converting floting point types to arithmetics.
  • The library now compiles and works fine with -fno-sanitize-recover=integer #45.
• Locale:

  • Fix linker issues due to missing typeinfo for char8_t in C++20 mode
  • Fix IConv compile flags when using ICU that has a bundled IConv
  • collator now throws on construction, if at all, as documented
  • collator no longer derives from std::collator to avoid possible type confusing when it isn't available for the current backend PR#216
  • Throw an exception when a faulty IConv library is detected (e.g. on some MacOS versions) instead of looping indefinitely PR#218
  • Reduce resolution of date_time to seconds as milliseconds where not easily available causing confusion #221
• Math:

  • Added a new collection of optimization algorithms:

    • Differential Evolution PR#1062
    • JSO PR#1065
    • Random Search PR#1071
    • CMA-ES PR#1074
  • Fix Divide by 0 warning in NCF survival function
  • Fix constexpr depth limits of ccmath::floor/ceil fail for large arguments
  • Improve accuracy of quartic_roots
  • Fix cstdfloat numeric limits detection macro for libstdc++14
  • Fix for MSVC UCRT defining _Complex_I in complex.h when using C++14 PR#1060
  • Improve cstdfloat iostream PR#1066
  • Fix redefnition of Boost.Config macros when using standalone mode in a non-standalone environment
  • Significant improvements to code coverage with associated bug fixes
• MSM:

  • Major Update. Backend update (back11). Requires C++ 11. The documentation now uses it as default.
  • Big new feature. New front-end (PlantUML). Requires C++ 20
  • Various Bugfixes (compiler errors and warnings, priority of deferred events)
• Multi-index Containers:

  • Fixed documentation errors.
• Multiprecision:

  • Fix deprecation warnings from C++23 <limits> PR#575
  • Fix cpp_bin_float for small bit counts PR#577
  • Fix -Wpessimizing-move PR#580
  • Add covecov runs
  • Reduce truncation in cpp_dec_float multiplication PR#585
  • Fix complex_adaptor to match precision requirements PR#597
  • Fix for breaking changes in tommath PR#603
  • Fix for types that can be converted to number participting in arithmetic operator overloads #608
• MySQL:

  • Breaking change: Boost.MySQL now requires linking to the new Boost.Charconv compiled library. This addresses a locale-dependency problem, increases efficiency, and powers the new client-side SQL formatting feature.
  • Added experimental support for connection pools, which allows re-using sessions and provides built-in reconnection and error handling.
  • Added experimental support for type-erased connections (any_connection class). any_connection is not a template and features simpler connection establishment and reconnection semantics.
  • Added experimental support for client-side SQL formatting functions (format_sql and format_sql_to). These allow securely composing queries client-side, which enables patterns like batch inserts, dynamic filters or PATCH-like updates.
  • Fixed a performance issue affecting close_statement and async_close_statement that could cause significant delays in application code.
  • Added support for building with BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT.
  • The deprecated execution interface (connection::query, connection::start_query, connection::execute_statement, connection::start_statement_execution and their async counterparts) now triggers warnings, as it's scheduled for removal in Boost 1.86.
  • Fixed a bug that caused some error messages to be truncated.
  • Warning cleanup. Builds are now clean from warnings when building with -Wall and -Wextra.
  • All field_view constructors are now stable.
  • The library internals have been rewritten using a sans-io approach to reduce complexity.
• Odeint:

  • Breaking change: The library now explicitly requires C++14 instead of implicitly by including Boost.Math
  • Fix compatibility with Thrust 1.10.0
  • Removed C++03 Boost components:

    • Array
    • Bind
    • Function
    • Static_assert
• PFR:

  • boost::pfr::get_name now can work with local types on some compilers. Thanks to Bela Schaum for the PR PR#152!
  • Removed unused implementation details. Thanks to Denis Mikhailov for the PR PR#154.
  • Allow throwing exceptions from boost::pfr::structure_to_tuple. Thanks to Denis Mikhailov for the bug report #155.
  • Field reflection trick is now described in the docs. Thanks to all the discussion participans in #150!
• Random:

  • Added splitmix64 PRNG PR#89
• System:

  • C++03 is no longer supported; a C++11 compiler is required. (This includes GCC 4.8 or later, and MSVC 14.0 (VS 2015) or later.)
  • The deprecated header boost/system/cygwin_error.hpp has been removed.
  • The original and obsolete (32 bit) MinGW is no longer supported. MinGW-w64 (both 64 and 32 bit) is still supported.
  • operator& now works for result<void> (by way of taking a nullary function.)
  • Added operator|= for result.
• Stacktrace:

  • Big new feature: stacktrace from arbitrary exception. On some POSIX platforms std::stacktrace::from_current_exception() now returns the stacktrace of the current exception object as if the stacktrace was captures at the point of throwing the exception. Many thanks to Andrei Nekrashevich for prototyping the idea in libsfe.
  • Fixed memory consumption on Windows with boost_stacktrace_windbg. Thanks to ycyclop for reporting the issue #111, to Thiago A. Correa for providing more information, to Andrei Karpovskii for providing a possible fix.
  • Fixed library build with non hidden visibility. Thanks to Jan Bouwer for the report and information on how to fix it.
  • Added a separate section on async signal safety to the docs. Many thanks to tworonix for highlighting the problem in #131 and to itrofimow for information on the problem.
• STLInterfaces:

  • Change the behavior of iterator_interface for input iterators in C++20 and later, to more closely follow the C++20 concepts.
  • Remove hidden friends from iterator_interface to fix errors about concepts being redefined with different constraints.
  • Add a new v3 inline namespace, containing a new iterator_interface based on deducing this instead of CRTP (C++23 and later).
  • Add an rvalue-qualified overload of closure::operator(), to prevent dangling temporaries.
• Test:

  • Respect library-spcific _NO_LIB macros PR#406
  • Supress MSVC C4702 from __builtin_unreachable() on intentionally unreachable code
  • Fix boost::function streaming error PR#411
• Unordered:

  • Optimized emplace() for a value_type or init_type (if applicable) argument to bypass creating an intermediate object. The argument is already the same type as the would-be intermediate object.
  • Optimized emplace() for k,v arguments on map containers to delay constructing the object until it is certain that an element should be inserted. This optimization happens when the map’s key_type is move constructible or when the k argument is a key_type.
  • Fixed support for allocators with explicit copy constructors (PR#234).
  • Fixed bug in the const version of unordered_multimap::find(k, hash, eq) (PR#238).
• Variant:

  • Removed more of the pre-C++11 macro and workarounds.
• Wave: Fixed bugs:

  • #200: Emitted pragmas lack terminating newline
  • #202: YYMARKER not updated when fill called on BOOST_WAVE_BSIZE boundary

Updated Tools

• Build:

  • Includes release of B2 version 5.1.0.

Compilers Tested

Boost's primary test compilers are:

• Linux:

  • Clang, C++03: 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 12.0.0, 13.0.0, 14.0.0, 15.0.0
  • Clang, C++11: 3.4, 11.0.0, 13.0.0, 14.0.0, 15.0.0
  • Clang, C++14: 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 12.0.0, 13.0.0, 14.0.0, 15.0.0
  • Clang, C++17: 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0, 12.0.0, 13.0.0, 14.0.0, 15.0.0
  • Clang, C++20: 11.0.0, 12.0.0, 13.0.0, 14.0.0, 15.0.0
  • GCC, C++03: 4.6.3, 11, 12
  • GCC, C++11: 4.7.3, 4.8.5, 11, 12
  • GCC, C++14: 5.4.0, 6.4.0, 7.3.0, 8.0.1, 9.1.0, 11, 12
  • GCC, C++17: 7.3.0, 8.0.1, 9.1.0, 11, 12
  • GCC, C++20: 8.0.1, 9.1.0, 10, 11, 12
• OS X:

  • Apple Clang, C++03: 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, 14.3

Acknowledgements

Marshall Clow and Glen Fernandes managed this release.