New Libraries

• URL: A library for parsing, modifying, and printing URLs using only C++11, from Vinnie Falco and Alan de Freitas. Features include fast compilation, strong invariants, and strict compliance using a memory-friendly approach.

Updated Libraries

• Asio:

  • Added the consign completion token adapter, which can be used to attach additional values to a completion handler.
  • Added any_completion_handler<>, which can be used to type-erase completion handlers.
  • Added experimental::co_composed to enable lightweight implementations of user-defined asynchronous operations using C++20 coroutines.
  • Add range-based experimental::make_parallel_group() overloads.
  • Added any_completion_executor, a type-erased wrapper for executors that are associated with completion handlers.
  • Added missing context query to use_future's executor.
  • Added nothrow constructor overloads to execution::any_executor<> and any_io_executor.
  • Optimised representation of empty execution::any_executor objects to improve the performance of copy and move operations.
  • Added an associated_cancellation_slot specialisation for std::reference_wrapper.
  • Changed I/O objects to return their executors by const reference.
  • Changed associated to use deduced return types for all two-argument get functions.
  • Fixed spawn implementation to catch unhandled exceptions and rethrow them outside of the spawned "thread".
  • Fixed spawn to ensure the completion handler is dispatched through the correct executor.
  • Fixed cleanup of of terminal-state spawn "thread" objects.
  • Fixed spawn and co_spawn implementations to dispatch cancellation handlers on the correct executor.
  • Changed semantics of 'dispatch' to mean the executor is used as-is.
  • Deprecated the execution::execute customisation point and sender/receiver facilities.
  • Added a C++11 parallel_group example.
  • Fixed example code to not use the deprecated resolve conversions.
  • Fixed an ambiguity in experimental::channel_traits specialisations.
  • Added a specialised channel implementation for the for R(error_code) signature.
  • Made cancelled() public on the async_compose 'self' object.
  • Added io_executor_type and get_io_executor to the async_compose 'self' object.
  • Fixed implementation of release() for Windows overlapped handles.
  • Enabled deferred awaiting for experimental::coro, regularised experimental::use_coro, and fixed allocator handling.
  • Cleaned up experimental::promise and made it an asynchronous operation object.
  • Constrained post/defer overloads on ability to require blocking.never.
  • Changed descriptor implementation to fall back to fcntl if ioctl fails with ENOTTY when setting non-blocking mode.
  • Fixed Xcode deprecation warnings related to use of sprintf.
  • Fixed the arguments passed to select_reactor::run when it is run on an internal thread.
  • Fixed compilation errors when BOOST_ASIO_DISABLE_SMALL_BLOCK_RECYCLING is defined.
  • Updated detection of C++20 coroutine support on clang 14 and later.
  • Changed standard library feature detection to always enable std::invoke_result when targeting C++17 or later.
  • Fixed detection of return type deduction with MSVC.
  • Updated the asynchronous operation requirements to relax the requirements on the associated executor.
  • Added io_uring to the implementation notes.
  • Consult the Revision History for further details.
• Beast:

  • Add buffers_generator
  • Add beast::http::message_generator
  • Added buffer_ref, so beast buffers can be used with asio.
  • Support for per-operation cancellation
  • C++20 awaitable examples.
  • websocket per-message compression options
  • websocket timeout option api
  • multiple content length error
  • Support for default-completion and rebind
• Container Hash:

  • Major update.
  • The specializations of boost::hash have been removed; it now always calls hash_value.
  • Support for BOOST_HASH_NO_EXTENSIONS has been removed. The extensions are always enabled.
  • All standard containers are now supported. This includes std::forward_list and the unordered associative containers.
  • User-defined containers (types that have begin() and end() member functions that return iterators) are now supported out of the box.
  • Described structs and classes (those annotated with BOOST_DESCRIBE_STRUCT or BOOST_DESCRIBE_CLASS) are now supported out of the box.
  • hash_combine has been improved.
  • The performance (and quality, as a result of the above change) of string hashing has been improved. boost::hash for strings now passes SMHasher in 64 bit mode.
  • The documentation has been substantially revised to reflect the changes.
• Core:

  • empty_value members are now marked as constexpr.
  • Added fclose_deleter, a deleter that calls std::fclose on a pointer to std::FILE.
  • Bit manipulation utilities in boost/core/bit.hpp now explicitly require unsigned integers on input. (#129)
  • bit_width now returns int instead of a value of the input argument type. This follows resolution of LWG3656.
• Describe:

  • To allow the inclusion of enumerators.hpp, bases.hpp, and members.hpp when the option -pedantic is used, the invocation of BOOST_DESCRIBE_ENUM has been moved from modifiers.hpp into a separate header, modifier_description.hpp. As a consequence, modifiers.hpp no longer includes enum.hpp. Code that has been relying on this implicit inclusion may fail, and will need to be fixed to include enum.hpp.
• DLL:

  • Fixed path_from_handle implementation for Windows platforms, thanks to @SaltfishAmi for the bug report 57.
• Filesystem:

  • Deprecated: path construction, assignment and appending from containers of characters, such as std::vector<char> or std::list<wchar_t>, is deprecated in v3 and removed in v4. Please use string types or iterators instead.
  • Deprecated: boost/filesystem/path_traits.hpp header is deprecated and will be removed in a future release. The header contained implementation details of path and should not be used in user's code.
  • Previously deprecated APIs will now generate compilation warnings on use. To suppress these warnings, BOOST_FILESYSTEM_ALLOW_DEPRECATED macro can be defined when compiling user's code.
  • Fixed compilation due to a missing include on POSIX systems that do not support *at APIs. (#250)
  • On Windows prior to 10, added a workaround for network share filesystem that produces ERROR_INVALID_PARAMETER when constructing directory iterators. (PR#246, #245)
  • On Windows, fixed weakly_canonical failing with an ERROR_INVALID_FUNCTION error code if the path started with the "\\?\" prefix. (#247)
  • Added support for std::string_view, boost::string_view and boost::container::string (as well as respective wchar_t counterparts) in path constructors, assignment and appending operations. (#208)
  • path constructors, assignment and appending operations taking a pair of iterators will no longer accept iterators with value types that are not one of the supported path character types.
  • On Windows, improved compatibility of directory_iterator with various mounted filesystems and Wine releases prior to 7.21. (#255, #266)
  • On Windows, deduplicated files are now reported as regular files rather than reparse files. (#262)
• Fusion:

  • Added fusion::identity_view (PR#240)
  • Added support for associative sequences on fusion::transform_view (PR#239)
  • Fixed compilation for the case when fusion::reverse_view used with an associative sequence (PR#237)
  • Fixed Clang 13 -Wdeprecated-copy warnings (PR#261)
  • A small dependency reorganization. Now boost::ref and boost::noncopyable are used from Boost.Core (PR#249)
  • Added CI testing on Linux and MacOS for clang and gcc, fixed CI testing on Windows (PR#245, PR#236)
  • Improved docs and fixed typos (#234, PR#235, PR#238)
• Geometry:

  • Solved issues

    • #1048 Index: Fix dangling references when Indexable is returned by value by IndexableGetter
    • #1076 Union: in rare cases it might miss one polygon
    • #1081 Union: due to precision it might miss interior rings
  • Bugfixes

    • #1063 Intersection: fix a bug in intersection of simple spherical polygons
    • #1064 Formulas: fix a consistency issue in geodesic direct formulas
    • #1088 Point: Fix regression for custom point types
    • Various fixes for missing include files, warnings, C++20 compilation errors and documentation
• Histogram:

  • Major update.
  • Added new accumulators::fraction to compute fractions, their variance, and confidence intervals
  • Added interval computers for fractions: utility::clopper_pearson, utility::wilson_interval, utility::jeffreys_interval, utility::wald_interval which can compute intervals with arbitrary confidence level
  • Added utility::confidence_level and utility::deviation types to pass confidence levels as probabilities or in multiples of standard deviation for all interval computers, respectively
  • Fixed internal sub_array and span in C++20
• Iterator:

  • function_output_iterator now supports perfect forwarding of the assigned values to the wrapped function object. (PR#73)
  • Fixed compilation of constructing a function_input_iterator from result of post-incrementing another function_input_iterator. (#75)
  • The result of post-incrementing an iterator based on iterator_facade now supports operator->. (it++)->foo is equivalent to (*it++).foo, which was supported before.
• JSON:

  • Added object::stable_erase.
  • Added parse overload for std::istream and operator>> for value.
  • Added rvalue ref-qualified accessors for value.
  • Conversion traits were redesigned.
  • Added conversion support for described classes and enums, std::optional, std::variant, and null-like types (including std::nullptr_t, std::nullopt_t, and std::monotype).
  • Added non-throwing conversion from value to user types.
• LexicalCast:

  • Fixed compilation while casting volatile arithmetic types. Thanks to Giovanni Cerretani for the bug report #50.
  • Removed usage of deprecated headers. Thanks to Michael Ford for the PR PR#53.
• Locale:

  • Major update with some breaking changes.
  • C++11 support is now required, support for C++03 and earlier is dropped
  • Some enums have been converted to enum classes - Avoids name clashes
  • Replace -sICU_LINK_LOCALE & -sICU_LINK by fine-grained configuration options as done in Boost.RegEx
  • Fix detection of libiconv allowing Boost.Locale to be build (again) on some platforms
  • Remove use of and support for std::auto_ptr
  • Make the codecvt using wchar_t on Windows assume/use UTF-16 enconding
  • Performance improvements: Make basic_format, date_time & hold_ptr movable, Fix use of format cache
  • Make Boost.Locale compatible with more ICU versions (especially the tests)
  • Fix RTTI definitions for some classes (visibility issues)
  • Fix compatibility of the ICU backend with some libc++ versions
  • Fix return value of some operators to correctly return non-const *this
  • Fix int-overflow on negative roll of years in date_time
  • Handle or suppress many warnings which makes the build log cleaner
  • Add support for more Windows codepages
  • Fix support for Windows codepages like ISO-2022-JP
• Nowide:

  • Fix build failure of tests on MSVC
• Stacktrace:

  • The library does not use COM initialization any more. Thanks to Alex Guteniev for the bug report, clarifications and PR PR#123!
  • The library now may use BOOST_STACKTRACE_BACKTRACE_INCLUDE_FILE macro value while detecting the libbacktrace availability in b2, thanks to Ben Gemmill for the bug report #115.
  • Added BOOST_STACKTRACE_BACKTRACE_FORCE_STATIC macro to force a single backtrace_state static instance while using the libbacktrace. Thanks to the Rasmus Thomsen for the bug report #118!
  • Avoid unresolved references when including only the boost/stacktrace/stacktrace.hpp header. Thanks to the Long Deng for the bug report #116.
  • Optimized stacktrace printing by not calling strlen on Windows platforms. Thanks to Alex Guteniev for the bug report #122
• PFR:

  • Improved detection of aggregate initializables in C++14 mode, thanks to Denis Mikhailov for the PR PR#97.
  • Suppress clang-tidy warnings, thanks to Alexander Malkov for the PRs PR#109, PR#104.
  • Use fold expressions if they are supported by the compiler. Thanks to Jean-Michaël Celerier for the PR PR#96.
• STLInterfaces:

  • Fix two ill-formed iterator_interface operators in pre-C++20 iterators with a const value_type.
• System:

  • The macro BOOST_SYSTEM_DISABLE_THREADS can now be defined to disable the use of <mutex> (e.g. on single-threaded libstdc++).
  • Added value_type, error_type, in_place_value, in_place_error to result<>.
  • Added emplace to result<>.
• Unordered:

  • Major update.
  • Added fast containers boost::unordered_flat_map and boost::unordered_flat_set based on open addressing.
  • Added CTAD deduction guides for all containers.
  • Added missing constructors as specified in LWG issue 2713.
• Variant:

  • Avoid recursive inclusion of headers, thanks to Nathan Sidwell for the bug report #101.
  • Removed usage of deprecated headers, thanks to Michael Ford for the PR PR#96.
  • Fixed compilation on clang in C++23 mode, thanks to Ed Catmur for the PR PR#98.
• Variant2:

  • Added support for boost::json::value_from and boost::json::value_to.

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, 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: 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: 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.