New Libraries

• Bloom: Bloom filters, from Joaquín M López Muñoz.

Updated Libraries

• Any:

  • Initial support for C++20 Modules. See the docs for more info.
• Asio:

  • Added allocator constructors to execution_context, io_context and thread_pool, with the supplied allocator being used for allocating objects associated with the execution context.
  • Added a new configuration parameter "timer" / "heap_reserve" that may be used to reserve space in the vector used for a timer queue's heap.
  • Added a new configuration parameter "resolver" / "threads" that specifies the number of internal threads used by async_resolve to emulate asynchronous address resolution.
  • Removed deadline_timer, basic_deadline_timer and time_traits from the convenience header boost/asio.hpp.
  • Ensured that the Windows named pipes created by connect_pipe use unique names that do not conflict if Asio is used in multiple, independent plug-in DLLs.
  • Changed BOOST_ASIO_CONCURRENCY_HINT_SAFE to be consistent with the io_context default constructor.
  • Fixed the documentation for BOOST_ASIO_CONCURRENCY_HINT_UNSAFE_IO to reflect that registration locking is still enabled.
  • Added separate b2 and cmake build targets for optional dependencies.
  • Added the [[noreturn]] attribute to boost::asio::detail::throw_exception.
  • Fixed co_spawn to adhere to the asynchronous operation requirement for non-reentrant invocation of the completion handler.
  • Added a documentation note on basic_signal_set async signal safety.
  • Fixed various minor compilation errors on different platforms.
  • Consult the Revision History for further details.
• Atomic:

  • Added TSAN instrumentation in asm-based x86, AArch32, AArch64 and PPC backends. This silences TSAN false errors for code using Boost.Atomic for thread synchronization.
  • Following the announcement in Boost 1.84, removed support for Windows versions older than Windows 10.

    • A note to MinGW-w64 users. Since Windows SDK headers on MinGW-w64 define _WIN32_WINNT to an older Windows version by default, you may need to define _WIN32_WINNT=0x0A00 or BOOST_USE_WINAPI_VERSION=0x0A00 when compiling Boost.Atomic and the code that uses Boost.Atomic.
  • Support for Windows CE is deprecated and will be removed in a future release.
  • Added support for timed waiting operations.
  • Exposed thread_pause operation, which can be used as a backoff measure in spin loops. Added support for PowerPC and improved support for AArch64 in thread_pause.
  • Removed BOOST_ATOMIC_NO_ATOMIC_FLAG_INIT macro definition. Since the library now requires C++11, BOOST_ATOMIC_FLAG_INIT is always supported.
  • Enabled bitwise operations for atomic enumerations. This can be useful when enumerations are used to implement bit masks.
• Beast:

  • Fixes

    • Conditionally defined immediate_executor_type in async_base.
    • Added missing cstdint header to detail/cpu_info.hpp.
    • Fixed std::is_trivial deprecation warnings.
    • handshake_timeout now applies to closing handshakes during reads.
  • Improvements

    • Replaced detail/work_guard.hpp with net::executor_work_guard.
    • Fixed portability issues for building tests in MinGW.
  • Documentation

    • Removed moved sections from documentation.
    • Removed superfluous log messages from tests.
  • Acknowledgements

    • yliu1021
• Charconv:

  • Fixed a performance degradation with from_chars for integer types
  • Fixed rounding and trailing decimal place bugs with to_chars for specified precisions with floating point types
• Cobalt:

  • Move assign fixed for generator & promise.
  • Fixed internal exceptions
  • Added IO library. Cobalt.io provides a large subset of asio as a compiled library.
• Compat:

  • Added move_only_function.hpp.
• ContainerHash:

  • Added the hash_is_avalanching trait class.
• Conversion:

  • Added an ability to use polymorphic_downcast and polymorphic_cast in constexpr (requires C++20).
• Core:

  • Fixed bit_ceil to return 1 for input 0 as per specification. (PR#199)
  • Added support for std::format to boost::core::string_view. (#190)
• Detail:

  • Operators generated by BOOST_BITMASK now use underlying type of the enum to implement bitwise operators. The operators are marked noexcept and constexpr, when possible.
  • The function bitmask_set generated by BOOST_BITMASK is marked deprecated. In a future release, BOOST_BITMASK will stop producing this function. Users are recommended to use double negation (!!mask) to test if the value is zero. This affects e.g. enums defined in Boost.Filesystem.
• DLL:

  • Fixed compiling and exporting on Cygwin. Many thanks to Luohao Wang for the PR!
  • Fixed building on FreeBSD. Thanks to ash for the bug report!
  • Added BOOST_DLL_USE_STD_FS CMake option to match the preprocessor option. Thanks to Yury Bura for the PR!
• Filesystem:

  • Corrected ASAN warnings about comparing pointers to potentially unrelated objects in path::append. (#335)
• Geometry:

  • Major improvements

    • PR#1369 Rewrite of traversal
    • PR#1402 Add geometry polyhedral surface
  • Improvements

    • PR#1404 Performance improvements in buffer
    • PR#1405 Avoid static variables and functions in header files
  • Breaking changes

    • PR#1401 Remove deprecated headers
  • Solved issues

    • #1221 Difference with rectilinear multipolygon with integer coordinates produces invalid polygon with disconnected interior
    • #1295 Wrong result in intersection (result polygon is equal to the biggest of the input polygons)
    • #1349 Difference of polygons giving wrong result
    • #1382 Buffer operation creates self-intersection
    • Various fixes of errors and warnings
• Hash2:

  • Added Blake2 algorithm (blake2s_256, blake2b_512).
  • Added XXH3 algorithm (xxh3_128).
• Iterator:

  • Fixed filter_iterator copy/converting constructor, which could previously produce an invalid iterator. (#92)
  • Removed usage of is_trivial in iterator_facade as it is deprecated in C++26. (#93)
  • iterator_facade::operator[] now always returns a proxy rather than conditionally returning a value or a proxy. This allows users to bind a reference to the result of the operator, regardless of whether the value type is trivially-copyable. (#61)
  • The proxy returned by iterator_facade::operator[] now supports forwarding dereferencing operators to the referenced value. This allows it[n]->foo() and (*it[n]).foo() expressions to compile.
  • The proxy returned by iterator_facade::operator[] now implementes perfect forwarding in its assignment operator.
• JSON:

  • Revamped documentation.
  • Optionals that are ranges are categorised as optionals.
  • Described class support is enabled for types with bases.
• Log:

  • Added support for BOOST_LOG_WITHOUT_ASIO configuration macro, which can be used to remove the dependency on Boost.Asio and disable the related functionality.
  • Use locale-independent formatting of the file counter in text_file_backend when composing log file names. This fixes failures in the subsequent parsing of the file names in file_collector::scan_for_files. (PR#246)
  • Added a new wrap_filter utility that simplifies injecting user-defined function objects in filtering expressions. (#195)
• Math:

  • Add explicit C++14 <type_traits> and constexpr requirement to builds
  • Collected fixes for GPU support on a variety of platforms
  • Fix lower incomplete gamma function with x = 0
  • Fix the external archive error in the jSO algorithm
  • Fix numeric underflow in ibeta
  • Fix inverse ibeta for large values of a and b
  • Fix variadic functions to make them safe with C++26
• MQTT5:

  • Fixed incorrect parsing of URI paths in the list of brokers (#31).
  • Default Maximum Packet Size now explicitly set in the CONNECT packet. (#33).
  • Fixed high CPU usage with large Maximum Packet Size values (#33).
• Multiprecision:

  • Major update.
  • Adds a new backend type: cpp_double_fp_backend
  • Fixes a namespace collision with Boost.Serialization
• MySQL:

  • The caching_sha2_password authentication plugin can now be used without TLS. This is the default in MySQL 8 and above. Plaintext connections that attempt to use this plugin no longer fail with client_errc::auth_plugin_requires_ssl (#313).
  • Fixed a problem causing client_errc::incomplete_message to be returned during connection establishment when the target database does not exist and the caching_sha2_password is used. The appropriate server-generated diagnostic is now returned. See issues #468 and #488.
  • The handshake algorithm is now more resilient to protocol violations (#469).
  • Fixed a build failure with gcc-15 due to a missing include (PR#475). Thanks hhoffstaette for the PR.
  • Added benchmarks against the official drivers.
  • Optimized metadata representation to be faster to construct and take less memory (#461).
• PFR:

  • Rewrite C++20 module following the new recommended Boost practice. See the docs for more info.
  • Fixed C++26 compilation on modern clang compilers. Thanks to Valery Mironov for the report!
  • Support types that use 'Arrays of Length Zero' compiler extension.
  • Fixed typos. Thanks to Egor for highlighting the issues!
  • Return std::array<std::string_view, 0> type for boost::pfr::names_as_array(empty_struct{}) to allow compilation of for (std::string_view name : boost::pfr::names_as_array(empty_struct{})). Many thanks to sabudilovskiy for the bug report!
• process:

  • Added v1.hpp to emulate v1 process.hpp include.
  • Fix to windows path escaping
  • Fixed exit-code issue wehre terminate & async_wait lead to a loss of the exit-code value.
• Random:

  • Fix NAN being generated by beta_distribution
  • Improve the performance of beta_distribution::operator()
• System:

  • The stub compiled library has been removed; System has been header-only since release 1.69.
  • This may affect CMakeLists.txt files containing find_package(Boost COMPONENTS system ...). The easiest fix is to just remove system from the list of components as it's no longer required. If compatibility with Boost releases earlier than 1.69 is to be preserved, one can use find_package(Boost COMPONENTS ... OPTIONAL_COMPONENTS system).
• TypeIndex:

  • Initial support for C++20 Modules. See the docs for more info.
• Unordered:

  • Deprecated boost::unordered::hash_is_avalanching is now a using-declaration of boost::hash_is_avalanching in <boost/container_hash/hash_is_avalanching.hpp>. Use that header directly instead. <boost/unordered/hash_traits.hpp> will be removed in the future.
  • Added pull(const_iterator) to open-addressing containers. This operation allows for efficient removal and retrieval of an element via move construction.
• Histogram:

  • Update CMake minimum version and Python detection in CMake
  • Improve documentation

    • Add example on how to make an axis which accepts multiple value types that are not implicitly convertible
    • Show how to use histogram::fill with a multidimensional histogram efficiently when data per dimension is already available as contiguous data
  • Don't use deprecated form of user-defined literal operator
  • Add support for modular build structure with b2
  • Fixed warnings in MSVC about narrowed types
  • Added collector accumulator, which stores all values in a bin
  • Internal changes to tests and classes in detail namespace

Updated Tools

• Build:

  • Includes release of B2 version 5.3.2.

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, Glen Fernandes and Ion Gaztañaga managed this release.