Boost C++ Libraries

New Libraries No new libraries Updated Libraries Asio: Added ip::scope_id_type type alias. ... [More] Added ip::port_type type alias. Added std::hash specialisations for IP addresses. Added std::hash specialisations for ip::basic_endpoint<>. Refactored SFINAE usage to improve compile times. Added friendship support to customisation points, and made most customisations private. Changed any_io_executor to a "strong typedef"-style class. Fixed experimental::as_single to work with handler hook deprecation. Ensured pthread condition variable attributes are cleaned up on all platforms. Clarified thread safety notes on sockets and descriptors. Ensured errno is not overwritten if socket() fails on macOS/FreeBSD. Fixed work tracking for io_context and thread_pool executors when move-assigned. Ensured internal call_stack objects are accessed only from implementation files. Fixed I/O object move-assignment to ensure the executor is left in a valid state. Fixed detection of compiler support for defaulted template argument on functions with MSVC. Prevented the blocking.always property from being used with strand<>, as it did not produce the correct semantics. Removed deprecated file asio/impl/src.cpp. Atomic: Fixed compilation with MSVC for ARM. (PR#49) Beast: This update brings minor bug fixes and revamped 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. Bind: Add support for using the standard C++11 placeholders with boost::bind. Update boost::apply to use variadic templates and perfect forwarding. Container: Added [[no-discard]] attribute in all containers to catch bugs related to unused return values. Replaced default standard exception classes with Boost.Container own classes, reducing considerably the included files overhead. Example: in MSVC 19 boost/container/vector.hpp preprocessed file size reduces from 1,5MB to 930KB. If you still want to use standard exception classes, you can define BOOST_CONTAINER_USE_STD_EXCEPTIONS before using any Boost.Container class. Fixed bugs/issues: GitHub #102: "flat_map::insert ambiguous with initializer list & pairs that need to convert". GitHub #139: "flat_map merge and iterators". GitHub #141: "small_vector does not propagate no throw properties of move operation of contained type". GitHub #164: "Compile error when using pmr::map with a std::pair; works when using a std::tuple". GitHub #171: "deque::clear() uses undefined behaviour". Core: Add implicit conversion between compatible reference wrappers. Add boost/core/cmath.hpp, a portable implementation of the floating point classification functions from <cmath>. Add boost/core/bit.hpp, a portable implementation of the C++20 standard header <bit>. Fix BOOST_TEST_EQ, BOOST_TEST_NE for character types under C++20. Revise allocator access utilities (now support VS2013, and no workarounds use allocator_traits.) DLL: BREAKING CHANGE: boost::dll::import was renamed to boost::dll::import_symbol to avoid collision with C++20 import keyword. Updated docs, including FAQ section. Filesystem: Updated compatibility with WASI platform. (PR#169) Fixed an exception being thrown by path::remove_filename if the path is "////". (#176) Fixed create_directories disregarding errors from file status query operations issued internally. This could result in incorrect error codes returned by create_directories. (#182) Geometry: Improvements PR#670 New IOs to_wkt() and from_wkt() (thanks to Baidyanath Kundu). PR#756 Non cartesian and robust convex hulls. PR#768 Umbrella strategies for relops, setops, index, buffer and more (undocumented for now). PR#797 New azimuth() algorithm. PR#801 Improved accuracy in geographic area computations. PR#820 Parameter scale added to svg_mapper. Bugfixes PR#808 Fixed compilation error with rtree serialization enabled (thanks to Tristan Carel). PR#815 Fixed issue in buffer(). Various fixes in set operations and buffer. Breaking changes Removed strategy convex_hull::graham_andrew. GIL: BREAKING: In next release, we are going to drop support for GCC 5. We will also change the required minimum C++ version from C++11 to C++14. Histogram: This release contains critical fixes, please check that your results are not affected. See Release Notes for details. Intrusive: Reduced compile-time dependencies: linear_slist_algorithms use a simple node_ptr instead of std::pair on return. list/slist use operator </operator == instead of std::equal_to/std::less. Fixed GitHub #54: set.rbegin() looks like O(log(N)) Interprocess: Added wchar_t API support for named resources in operating systems that offer native wide character API (e.g. Windows). The following classes were updated with wchar_t name support: file_mapping managed_mapped_file managed_shared_memory managed_windows_shared_memory shared_memory_object windows_shared_memory_object file_lock named_condition named_condition_any named_mutex named_recursive_mutex named_semaphore named_sharable_mutex named_upgradable_mutex message_queue Added BOOST_INTERPROCESS_FORCE_NATIVE_EMULATION macro option to disable the use of generic emulation code for process shared synchronization primitives instead of native POSIX or Winapi functions. Fixed bugs: GitHub #76 ("Cygwin compilation errors"). GitHub #83 ("Add BOOST_INTERPROCESS_FORCE_NATIVE_EMULATION option"). GitHub #92 ("bufferstream: Correct MSVC compilation warning"). GitHub #106 ("Use fallocate on truncate_file"). GitHub #120 ("segment_manager customization"). GitHub #122 ("Mark constructors/assignment/swap noexcept where possible"). GitHub #126 ("_ReadWriteBarrier is deprecated warning when compiling with clang-cl.exe"). JSON: Security Report from Bishop Fox. (#481) Refactored value_from implementation; user customizations are now always preferred over library-provided overloads. (#484) Fix imprecise parsing for some floating point numbers. (#485) Fix link errors in standalone mode, when used alongside Boost. (#497) Fix Boost.Build builds on GCC 4.8. LexicalCast: Dropped dependency on Boost.Math (thanks to Peter Dimov #37, #39). Fixes for the CI and coverage (thanks to Sam Darwin from "The C++ Alliance" #38, #42). Log: Bug fixes: Corrected a formal race condition in the thread-safe log record queue implementation used in the unbounded_fifo_queue policy of the asynchronous_sink frontend. The race could be detected by TSAN, but it was not a real problem on most current CPU architectures and compilers. (#139) When copying a logger with a channel attribute (e.g. channel_logger), the channel attribute is now deep-copied from the original logger. This means that modifying the channel in the new logger will no longer affect the original logger. Replaced the use of std::allocator<void> in template parameters with a new tag type boost::log::use_std_allocator to silence libc++ warnings about the former being deprecated in C++17 and later. The tag indicates that the instantiated template should be using a specialization of std::allocator internally to allocate dynamic memory, so the change has no functional effect. (#141) Boost.Log no longer defines __MSVCRT_VERSION__ macro on MinGW and MinGW-w64. Defining this macro caused incompatibility with UCRT, which is available as an option in recent MinGW-w64. (PR#149) See changelog for more details. Math: Breaking Change: C++03 support is now removed, a C++11 or later conformant compiler is now required to use this library. Added Z-test. Added execution policy support to univariate and bivariate statistics: enables parallel execution (requires C++17 and <execution>). Big update/improvement on CI testing. Bivariate statistics now have integer support. T-Test now has integer support. Linear regression now has integer support. Correct PDF of the beta distribution at the endpoints. Correct use of Stirling's approximation in certain multiprecision cases, fixes #396. Eliminate -Wimplicit-int-float-conversion on clang. Fix some constexpr issues in quaternion/octonion. Minor performance fix to tanh_sinh integration. Update hypergeometric functions internal scaling to allow for 64-bit (long long) exponents with multiprecision types. Move: Git Issue #35: "New nothrow move traits are incomplete". Multiprecision: BREAKING CHANGE: Massive refactoring and code simplification makes C++11 an absolute requirement. Use BOOST_TRY/CATCH in headers so code can be used in exception-free environments. Correct corner case in pow, fixes #277. Correct exception type thrown to match docs in lsb/msb: fixes #257. Allow moves and operators between related but different types (ie types with the same allocator), fixes #278. Nowide: Fix discarding of characters for text file streams when seek or sync functions are used and newlines were converted (e.g. on Windows) Fix potential use-after-free bug when reusing (via open) a file stream that has been closed Fix potential invalid memory access when using a file stream that has been moved or swapped to where the source had a put-back character or was set to unbuffered mode Fix compatibility with ucrt runtime by not defining __MSVCRT_VERSION__ Known issues: Read performance for text files is degraded. Binary files and writing is unaffected. Optional: Fixed MSVC warning C4702. Outcome: Announcements: BREAKING CHANGE: After a year and three major Boost releases announcing this upcoming change, this is the FIRST RELEASE of the v2.2 branch. This branch has a number of major breaking changes to the Outcome v2.1 which shipped in Boost 1.75 and earlier, see the documentation for details. Enhancements: VS2019.8 changed how to enable Coroutines, which caused Outcome to not compile on that compiler. If on C++ 20, we now use C++ 20 [[likely]] instead of compiler-specific markup to indicate when TRY has likely success or failure. BREAKING CHANGE: Previously the value of spare_storage(const basic_result|basic_outcome *) noexcept was not propagated over BOOST_OUTCOME_TRY, which causes things like stack backtraces captured at the point of construction of an errored result to get dropped at every TRY point. This has been fixed by adding an optional spare_storage to success_type<T> and failure_type<T>, as well as to auto success(T &&, ...) and auto failure(T &&, ...). Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. BREAKING CHANGE #244 It came as a shock to learn that BOOST_OUTCOME_TRY had been broken since the inception of this library for certain corner case code, which required a breaking change in how TRY works. See the changelog in the documentation for more detail. Parameter: Added a workaround for MSVC 2015 code miscompilation when an rvalue was used as a default value of a named parameter of a function. (PR#109, #132) PFR: Fixed reflection of types with missing const in SFINAE expressions in template constructor. Now reflection of aggregates with std::optional<std::chrono::duration??>> fields works on any Standard Library implementation, even if LWG3050 is not fixed. Comparison functions are now constexpr #52 Fixed numerous typos in docs (thanks to Phil Miller #63) PolyCollection: Worked around GCC bug affecting GCC versions 9.3-10.2 (issue #20). Predef: Version 1.13 Add ARCH_PPC_64 predef. Fix ARCH_WORD_BITS* redefinition warnings/errors. Add ARCH_E2K, Elbrus 2000, architecture from Konstantin Ivlev. Fix not handling recent C++ version that go above 10.x version. Version 1.12 Switch to using the endian.h header on OpenBSD. (Brad Smith) Fix not handling recent versions of stdcxx that go above version 9. Fix including sub-BSD OS headers directly causing redef warnings. Add CI testing of direct inclusion of all headers. Add CI testing on FreeBSD for clang and gcc. Add WORD_BITS set of predefs to detect the architecture word size. Initial implementation inspired by submission from Mikhail Komarov. Add CI testing for Cygwin 32 and 64. PropertyTree: Property Tree has a new maintainer. Fix usage of deprecated Boost.Bind features. Link to Wikipedia fixed. Use BOOST_OVERRIDE to fix GCC warnings. Add extensive CI testing. Regex: Regex is now header only except in C++03 mode. Support for C++03 is now deprecated. The library can now be used "standalone" without the rest of Boost being present. Stacktrace: Better support for pre-C++11 builds on clang #102. Bigger warning for do not use boost::stacktrace::stacktrace in signal handlers #71. TypeTraits: Fix for Visual Studio managed code projects. Variant2: Improved generated code for the double buffered case. Updated Tools Build: Includes release of B2 version 4.4.1. Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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Known Issues Boost.Operators is currently incompatible with C++20 compilers, which in some cases may manifest as an infinite recursion or infinite loop in runtime when a comparison operator is called. The problem is ... [More] caused by the new operator rewriting behavior introduced in C++20. As a workaround, users are advised to target C++17 or older C++ standard. More details can be found in #65. New Libraries JSON: JSON parsing, serialization, and DOM in C++11, from Vinnie Falco and Krystian Stasiowski. Fast compilation requiring only C++11 Easy and safe modern API with allocator support Compile without Boost, define BOOST_JSON_STANDALONE Optional header-only, without linking to a library LEAF: A lightweight error-handling library for C++11, from Emil Dotchevski. Small single-header format, no dependencies. Designed for maximum efficiency ("happy" path and "sad" path). No dynamic memory allocations, even with heavy payloads. O(1) transport of arbitrary error types (independent of call stack depth). Can be used with or without exception handling. PFR: Basic reflection without macro or boilerplate code for user defined types, from Antony Polukhin. Updated Libraries Asio: Enabled support for UNIX domain sockets on Windows. Added executor-converting construction and assignment to ip::basic_resolver. Added compatibility between polymorphic executors and the (deprecated) handler invocation hook. Added the experimental::as_single completion token adapter. Added support for MSG_NOSIGNAL on more platforms by using _POSIX_VERSION to detect whether it is supported. Added the ability to compile using libpthread on Windows. Added workarounds for the Intel C++ compiler. Added more support for detecting and optimising for handlers that have no custom executor. Reduced lock contention for timer cancellation on Windows. Reinstated a previously removed null-pointer check, as it had a measurable impact on performance. Fixed the executor concept to test for a const-qualified execute(). Fixed any_executor support for builds without RTTI support. Fixed the thread_pool unit test to work without RTTI support. Fixed C++20 coroutines compatibility with clang on Windows. Fixed some compatibility issues with Windows Runtime. Fixed shadow name warnings caused by addition of asio::query. Fixed a "logical ‘or’ of equal expressions" warning on linux. Fixed a benign switch fallthrough warning. Added missing push/pop_options.hpp includes. Suppressed zero-as-null-pointer-constant warnings. Fixed a comma-operator warning. Updated the documentation to clarify when the select reactor is used on Windows. Fixed potential ambiguity caused by any_executor comparisons and conversion. Added detection of non-experimental C++20 coroutines on MSVC 19.8. Fixed compatibility with uClibc. Fixed strand<> adaptation of Networking TS executors when targeting older C++ versions or less conformant compilers. Consult the Revision History for further details. Atomic: Implemented SSE2 and SSE4.1 versions of address lookup algorithm, which is used in the internal lock pool implementation. This may improve performance of waiting and notifying operations in heavily contended cases. Fixed a possible compilation error on AArch64 targets caused by incorrect instructions generated for bitwise (logical) operations with immediate constants. (#41) Beast: This update brings bug fixes and support for the BOOST_ASIO_ENBALE_HANDLER_TRACKING compile flag from Boost.Asio: 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. Container: New devector container. Fixed bugs/issues: #152 Tree-based containers have troubles with move-only types. #156 Compile error with vector. PR#157 Add missing include. #159: pmr::monotonic_buffer_resource crashes on large single allocations. #160: Usage of uses_allocator needs a remove_cvref_t. #162: small_vector on MSVC x86 call-by-value crash. #161: polymorphic_allocator(memory_resource*) non-standard extension causes headache. PR#163: container_rebind for small_vector with options. #165: Link error with shared library and memory_resource inline members. PR#166: Fix encoding error in copyright headers. PR#167: error: the address of 'msg' will always evaluate as 'true' warning with GCC 4.4. #169: flood of warnings building dlmalloc_ext_2_8_6.c on clang11. Endian: endian_arithmetic no longer inherits from endian_buffer When BOOST_ENDIAN_NO_CTORS is defined, the unaligned endian_buffer and endian_arithmetic are C++03 PODs, to enable use of __attribute__((packed)) Filesystem: New: Added creation_time operation, which allows to obtain file creation time. (Inspired by PR#134) The returned value of last_write_time(p, ec) operation in case of failure has been changed to a minimal value representable by std::time_t instead of -1. The returned value of hard_link_count(p, ec) operation in case of failure has been changed to static_cast<uintmax_t>(-1) instead of 0. On POSIX systems, file_size will now indicate error code errc::function_not_supported if the path resolves to a non-regular file. Previously, errc::operation_not_permitted was reported. On Linux, many operations now use statx system call internally, when possible, which allows to reduce the amount of information queried from the filesystem and potentially improve performance. The statx system call was introduced in Linux kernel 4.11. Removed const-qualification from return types of some path methods. This could prevent move construction and move assignment at the call site in some cases. (#160) On OpenBSD 4.4 and newer, use statvfs system call to obtain filesystem space information. (Inspired by PR#162) On Windows, space now returns with an error if the provided path does not idendify an existing file. (#167) Geometry: WARNING: Following the deprecation notice of C++03 issued with Boost 1.73, from now on the Boost.Geometry requires a capable C++14 compiler. Improvements PR#726 Umbrella strategies for area, envelope, expand (undocumented for now). PR#733 Added example of adaptation of std::array<> to Point concept (thanks to Ben FrantzDale). PR#745 constexpr added in geometries and arithmetic. PR#747 Added optional traits::make (undocumented for now). PR#748 Modernized usage of type traits. PR#759 MPL_ASSERT replaced with standard static_assert. PR#767 Modernized usage of tuple. Solved issues #716 Dangling proxy references. Bugfixes Various fixes in set operations and buffer. GIL: BREAKING: In next release, we are going to drop support for GCC 5. We may also change the required minimum C++ version from C++11 to C++14. Histogram: This update brings Bug-fixes for corner-cases Small documentation improvements Fixes for new warnings from latest compilers and when compiling against the C++20 standard See the full Release Notes for a complete list of changes. Interprocess: Fixed bugs: #127: static assertion failure with boost interprocess 1.74 and basic_managed_shared_memory. Intrusive: Fixed bugs: PR#48: MSVC "assignment within conditional" warning fix. PR#49: Fix empty control statement warnings. #52: Invalid casting in BOOST_INTRUSIVE_BSR_INTRINSIC. Log: Bug fixes: Corrected the file counter that would be used in text_file_backend when generating the target file name (based on the pattern set by set_target_file_name_pattern method) when the log file is rotated. (#125) Replaced a volatile version counter in basic_sink_frontend with an atomic. (#128) In the asynchronous_sink frontend, resolved a possible conflict between flush and run methods, if run is called from a user's thread instead of the internal dedicated thread spawned by the frontend. (#131) See changelog for more details. Move: Fixed bugs: #30: (void) C-cast is a non-portable way of suppressing compiler warnings. Mp11: Added mp_pairwise_fold (suggested by Barry Revzin) Removed mp_invoke (use mp_invoke_q) Optional: boost::none is constexpr-declared. Fixed issue #78. Outcome: Announcements: After a year and three major Boost releases announcing this upcoming change, this is the FINAL RELEASE of the v2.1 branch. From Boost 1.76 onwards, the v2.2 branch becomes the default. This branch has a number of major breaking changes to Outcome v2.1, see the documentation for details. Enhancements: The ADL discovered event hooks have been replaced with policy-specified event hooks instead. This is due to brittleness (where hooks would quietly self-disable if somebody changed something), compiler bugs (a difference in compiler settings causes the wrong hooks, or some but not all hooks, to get discovered), and end user difficulty in using them at all. The policy-specified event hooks can be told to default to ADL discovered hooks for backwards compatibility: set OUTCOME_ENABLE_LEGACY_SUPPORT_FOR to less than 220 to enable emulation. Improve configuring OUTCOME_GCC6_CONCEPT_BOOL. Older GCCs had boolean based concepts syntax, whereas newer GCCs are standards conforming. However the precise logic of when to use legacy and conforming syntax was not well understood, which caused Outcome to fail to compile depending on what options you pass to GCC. The new logic always uses the legacy syntax if on GCC 8 or older, otherwise we use conforming syntax if and only if GCC is in C++ 20 mode or later. This hopefully will resolve the corner case build failures on GCC. Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. #236 In the Coroutine support the final_suspend() was not noexcept, despite being required to be so in the C++ 20 standard. This has been fixed, but only if your compiler implements noop_coroutine. Additionally, if noop_coroutine is available, we use the much more efficient coroutine handle returning variant of await_suspend() which should significantly improve codegen and context switching performance. Polygon: C++20 fixes for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) Preprocessor: When variadic data is empty in C++20 mode with __VA_OPT__ support the variadic size has been corrected to be 0. This also means that in this C++20 mode it is now valid to convert to and from empty arrays and lists and variadic data. The end-user can read the "C++20 Support For Variadic Macros" part of the "variadic macros" topic for more information about empty variadic data in the library. The macro BOOST_PP_IS_STANDARD() has been added for identifying if the currently used preprocessor is a C++ standard conforming preprocessor. A number of preprocessors which generally work correctly with the library but need various internal workarounds, including the currently default VC++ preprocessor, are not considered C++ standard conforming preprocessors. However most preprocessors, including among others gcc, clang, and the new but currently non-default VC++ preprocessor in VS2019, are C++ standard conforming preprocessors. For C++ standard conforming preprocessors a number of the limits defined in the config/limits.hpp can now be changed to higher amounts for a TU. The end-user should read the "limitations" topic to understand how and which limits can be changed. For C++ standard conforming preprocessors, in order to allow the maximum number of FOR and WHILE iterations, the beginning 'r' and 'd' iteration numbers in the user-defined macros start at 1 and not 2, as it did in previous releases. This could be a breaking change if these iteration numbers are used in the user-defined macros ( they probably would not be ), but the change was necessary to fix some arcane bugs when dealing with numerical/logical operations with maximum numbers as well to allow the user-defined macros to be called the correct possible maximum number of times. For non-C++ conforming preprocessors, this change was not made because those non-conforming C++ preprocessors generally have limitations which disallow the maximum number of looping constructs to be run, and it was felt not to introduce a possible breaking change to those more fragile preprocessors would be better. It was also felt that besides fixing some arcane preprocessor bugs and providing the possible maximum number of user-defined macro invocations, this change could be made because it has never been documented what the starting 'r' and 'd' iteration numbers actually are but only that these numbers are incremented for each iteration. The library has been upgraded to assume variadic macro support for any compiler working with the library. Ostensibly this means that the library is now a C++11 on up library, yet most of the major compilers, including gcc, clang, and VC++, also support variadic macros in C++98/C++03 mode as long as strict compliance to C++98/C++03 is not turned on when using one of those compilers. Rational: Fix Rational operators to not break under new C++20 operator== rewriting rules. (Glen Fernandes) Signals2: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes) System: The platform-specific headers windows_error.hpp, linux_error.hpp, and cygwin_error.hpp emit deprecation messages and are slated for removal. The old names for generic_category() and system_category() emit deprecation messages and are slated for removal. error_condition::failed is deprecated and is slated for removal. operator bool() for error_condition has been reverted to its old meaning of value() != 0. This is done for compatibility with std::error_condition as the next release is expected to improve interoperability with <system_error> even further. Note that this does not affect error_code::failed, which is still alive and well. The overload of error_condition::message that takes a buffer is deprecated and is slated for removal, for the same reasons. Note that this does not affect error_code::message. uBLAS: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes and Conrad Poelman) VMD: The VMD number parsing has been upgraded to support the ability for the end-user to change the number limits in the Preprocessor library. The macro BOOST_VMD_IS_GENERAL_IDENTIFIER has been added to support the parsing of input that represents a preprocessor token which matches the VMD identifier syntax, without having to register the identifier as a specific identifier. Wave: Added new C++20 tokens, including the spaceship operator <=> Fixed bugs: #94: fix incorrect behavior of __LINE__ and __FILE__ under rescanning Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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Known Issues Boost.Operators is currently incompatible with C++20 compilers, which in some cases may manifest as an infinite recursion or infinite loop in runtime when a comparison operator is called. The problem is ... [More] caused by the new operator rewriting behavior introduced in C++20. As a workaround, users are advised to target C++17 or older C++ standard. More details can be found in #65. New Libraries JSON: JSON parsing, serialization, and DOM in C++11, from Vinnie Falco and Krystian Stasiowski. Fast compilation requiring only C++11 Easy and safe modern API with allocator support Compile without Boost, define BOOST_JSON_STANDALONE Optional header-only, without linking to a library LEAF: A lightweight error-handling library for C++11, from Emil Dotchevski. Small single-header format, no dependencies. Designed for maximum efficiency ("happy" path and "sad" path). No dynamic memory allocations, even with heavy payloads. O(1) transport of arbitrary error types (independent of call stack depth). Can be used with or without exception handling. PFR: Basic reflection without macro or boilerplate code for user defined types, from Antony Polukhin. Updated Libraries Asio: Enabled support for UNIX domain sockets on Windows. Added executor-converting construction and assignment to ip::basic_resolver. Added compatibility between polymorphic executors and the (deprecated) handler invocation hook. Added the experimental::as_single completion token adapter. Added support for MSG_NOSIGNAL on more platforms by using _POSIX_VERSION to detect whether it is supported. Added the ability to compile using libpthread on Windows. Added workarounds for the Intel C++ compiler. Added more support for detecting and optimising for handlers that have no custom executor. Reduced lock contention for timer cancellation on Windows. Reinstated a previously removed null-pointer check, as it had a measurable impact on performance. Fixed the executor concept to test for a const-qualified execute(). Fixed any_executor support for builds without RTTI support. Fixed the thread_pool unit test to work without RTTI support. Fixed C++20 coroutines compatibility with clang on Windows. Fixed some compatibility issues with Windows Runtime. Fixed shadow name warnings caused by addition of asio::query. Fixed a "logical ‘or’ of equal expressions" warning on linux. Fixed a benign switch fallthrough warning. Added missing push/pop_options.hpp includes. Suppressed zero-as-null-pointer-constant warnings. Fixed a comma-operator warning. Updated the documentation to clarify when the select reactor is used on Windows. Fixed potential ambiguity caused by any_executor comparisons and conversion. Added detection of non-experimental C++20 coroutines on MSVC 19.8. Fixed compatibility with uClibc. Fixed strand<> adaptation of Networking TS executors when targeting older C++ versions or less conformant compilers. Consult the Revision History for further details. Atomic: Implemented SSE2 and SSE4.1 versions of address lookup algorithm, which is used in the internal lock pool implementation. This may improve performance of waiting and notifying operations in heavily contended cases. Fixed a possible compilation error on AArch64 targets caused by incorrect instructions generated for bitwise (logical) operations with immediate constants. (#41) Beast: This update brings bug fixes and support for the BOOST_ASIO_ENBALE_HANDLER_TRACKING compile flag from Boost.Asio: 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. Container: New devector container. Fixed bugs/issues: #152 Tree-based containers have troubles with move-only types. #156 Compile error with vector. PR#157 Add missing include. #159: pmr::monotonic_buffer_resource crashes on large single allocations. #160: Usage of uses_allocator needs a remove_cvref_t. #162: small_vector on MSVC x86 call-by-value crash. #161: polymorphic_allocator(memory_resource*) non-standard extension causes headache. PR#163: container_rebind for small_vector with options. #165: Link error with shared library and memory_resource inline members. PR#166: Fix encoding error in copyright headers. PR#167: error: the address of 'msg' will always evaluate as 'true' warning with GCC 4.4. #169: flood of warnings building dlmalloc_ext_2_8_6.c on clang11. Endian: endian_arithmetic no longer inherits from endian_buffer When BOOST_ENDIAN_NO_CTORS is defined, the unaligned endian_buffer and endian_arithmetic are C++03 PODs, to enable use of __attribute__((packed)) Filesystem: New: Added creation_time operation, which allows to obtain file creation time. (Inspired by PR#134) The returned value of last_write_time(p, ec) operation in case of failure has been changed to a minimal value representable by std::time_t instead of -1. The returned value of hard_link_count(p, ec) operation in case of failure has been changed to static_cast<uintmax_t>(-1) instead of 0. On POSIX systems, file_size will now indicate error code errc::function_not_supported if the path resolves to a non-regular file. Previously, errc::operation_not_permitted was reported. On Linux, many operations now use statx system call internally, when possible, which allows to reduce the amount of information queried from the filesystem and potentially improve performance. The statx system call was introduced in Linux kernel 4.11. Removed const-qualification from return types of some path methods. This could prevent move construction and move assignment at the call site in some cases. (#160) On OpenBSD 4.4 and newer, use statvfs system call to obtain filesystem space information. (Inspired by PR#162) On Windows, space now returns with an error if the provided path does not idendify an existing file. (#167) Geometry: WARNING: Following the deprecation notice of C++03 issued with Boost 1.73, from now on the Boost.Geometry requires a capable C++14 compiler. GIL: BREAKING: In next release, we are going to drop support for GCC 5. We may also change the required minimum C++ version from C++11 to C++14. Histogram: This update brings Bug-fixes for corner-cases Small documentation improvements Fixes for new warnings from latest compilers and when compiling against the C++20 standard See the full Release Notes for a complete list of changes. Interprocess: Fixed bugs: #127: static assertion failure with boost interprocess 1.74 and basic_managed_shared_memory. Intrusive: Fixed bugs: PR#48: MSVC "assignment within conditional" warning fix. PR#49: Fix empty control statement warnings. #52: Invalid casting in BOOST_INTRUSIVE_BSR_INTRINSIC. Log: Bug fixes: Corrected the file counter that would be used in text_file_backend when generating the target file name (based on the pattern set by set_target_file_name_pattern method) when the log file is rotated. (#125) Replaced a volatile version counter in basic_sink_frontend with an atomic. (#128) In the asynchronous_sink frontend, resolved a possible conflict between flush and run methods, if run is called from a user's thread instead of the internal dedicated thread spawned by the frontend. (#131) See changelog for more details. Move: Fixed bugs: #30: (void) C-cast is a non-portable way of suppressing compiler warnings. Mp11: Added mp_pairwise_fold (suggested by Barry Revzin) Removed mp_invoke (use mp_invoke_q) Optional: boost::none is constexpr-declared. Fixed issue #78. Outcome: Announcements: After a year and three major Boost releases announcing this upcoming change, this is the FINAL RELEASE of the v2.1 branch. From Boost 1.76 onwards, the v2.2 branch becomes the default. This branch has a number of major breaking changes to Outcome v2.1, see the documentation for details. Enhancements: The ADL discovered event hooks have been replaced with policy-specified event hooks instead. This is due to brittleness (where hooks would quietly self-disable if somebody changed something), compiler bugs (a difference in compiler settings causes the wrong hooks, or some but not all hooks, to get discovered), and end user difficulty in using them at all. The policy-specified event hooks can be told to default to ADL discovered hooks for backwards compatibility: set OUTCOME_ENABLE_LEGACY_SUPPORT_FOR to less than 220 to enable emulation. Improve configuring OUTCOME_GCC6_CONCEPT_BOOL. Older GCCs had boolean based concepts syntax, whereas newer GCCs are standards conforming. However the precise logic of when to use legacy and conforming syntax was not well understood, which caused Outcome to fail to compile depending on what options you pass to GCC. The new logic always uses the legacy syntax if on GCC 8 or older, otherwise we use conforming syntax if and only if GCC is in C++ 20 mode or later. This hopefully will resolve the corner case build failures on GCC. Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. #236 In the Coroutine support the final_suspend() was not noexcept, despite being required to be so in the C++ 20 standard. This has been fixed, but only if your compiler implements noop_coroutine. Additionally, if noop_coroutine is available, we use the much more efficient coroutine handle returning variant of await_suspend() which should significantly improve codegen and context switching performance. Polygon: C++20 fixes for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) Preprocessor: When variadic data is empty in C++20 mode with __VA_OPT__ support the variadic size has been corrected to be 0. This also means that in this C++20 mode it is now valid to convert to and from empty arrays and lists and variadic data. The end-user can read the "C++20 Support For Variadic Macros" part of the "variadic macros" topic for more information about empty variadic data in the library. The macro BOOST_PP_IS_STANDARD() has been added for identifying if the currently used preprocessor is a C++ standard conforming preprocessor. A number of preprocessors which generally work correctly with the library but need various internal workarounds, including the currently default VC++ preprocessor, are not considered C++ standard conforming preprocessors. However most preprocessors, including among others gcc, clang, and the new but currently non-default VC++ preprocessor in VS2019, are C++ standard conforming preprocessors. For C++ standard conforming preprocessors a number of the limits defined in the config/limits.hpp can now be changed to higher amounts for a TU. The end-user should read the "limitations" topic to understand how and which limits can be changed. For C++ standard conforming preprocessors, in order to allow the maximum number of FOR and WHILE iterations, the beginning 'r' and 'd' iteration numbers in the user-defined macros start at 1 and not 2, as it did in previous releases. This could be a breaking change if these iteration numbers are used in the user-defined macros ( they probably would not be ), but the change was necessary to fix some arcane bugs when dealing with numerical/logical operations with maximum numbers as well to allow the user-defined macros to be called the correct possible maximum number of times. For non-C++ conforming preprocessors, this change was not made because those non-conforming C++ preprocessors generally have limitations which disallow the maximum number of looping constructs to be run, and it was felt not to introduce a possible breaking change to those more fragile preprocessors would be better. It was also felt that besides fixing some arcane preprocessor bugs and providing the possible maximum number of user-defined macro invocations, this change could be made because it has never been documented what the starting 'r' and 'd' iteration numbers actually are but only that these numbers are incremented for each iteration. The library has been upgraded to assume variadic macro support for any compiler working with the library. Ostensibly this means that the library is now a C++11 on up library, yet most of the major compilers, including gcc, clang, and VC++, also support variadic macros in C++98/C++03 mode as long as strict compliance to C++98/C++03 is not turned on when using one of those compilers. Rational: Fix Rational operators to not break under new C++20 operator== rewriting rules. (Glen Fernandes) Signals2: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes) System: The platform-specific headers windows_error.hpp, linux_error.hpp, and cygwin_error.hpp emit deprecation messages and are slated for removal. The old names for generic_category() and system_category() emit deprecation messages and are slated for removal. error_condition::failed is deprecated and is slated for removal. operator bool() for error_condition has been reverted to its old meaning of value() != 0. This is done for compatibility with std::error_condition as the next release is expected to improve interoperability with <system_error> even further. Note that this does not affect error_code::failed, which is still alive and well. The overload of error_condition::message that takes a buffer is deprecated and is slated for removal, for the same reasons. Note that this does not affect error_code::message. uBLAS: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes and Conrad Poelman) VMD: The VMD number parsing has been upgraded to support the ability for the end-user to change the number limits in the Preprocessor library. The macro BOOST_VMD_IS_GENERAL_IDENTIFIER has been added to support the parsing of input that represents a preprocessor token which matches the VMD identifier syntax, without having to register the identifier as a specific identifier. Wave: Added new C++20 tokens, including the spaceship operator <=> Fixed bugs: #94: fix incorrect behavior of __LINE__ and __FILE__ under rescanning Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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Known Issues Boost.Operators is currently incompatible with C++20 compilers, which in some cases may manifest as an infinite recursion or infinite loop in runtime when a comparison operator is called. The problem is ... [More] caused by the new operator rewriting behavior introduced in C++20. As a workaround, users are advised to target C++17 or older C++ standard. More details can be found in #65. New Libraries JSON: JSON parsing, serialization, and DOM in C++11, from Vinnie Falco and Krystian Stasiowski. Fast compilation requiring only C++11 Easy and safe modern API with allocator support Compile without Boost, define BOOST_JSON_STANDALONE Optional header-only, without linking to a library LEAF: A lightweight error-handling library for C++11, from Emil Dotchevski. Small single-header format, no dependencies. Designed for maximum efficiency ("happy" path and "sad" path). No dynamic memory allocations, even with heavy payloads. O(1) transport of arbitrary error types (independent of call stack depth). Can be used with or without exception handling. PFR: Basic reflection without macro or boilerplate code for user defined types, from Antony Polukhin. Updated Libraries Asio: Enabled support for UNIX domain sockets on Windows. Added executor-converting construction and assignment to ip::basic_resolver. Added compatibility between polymorphic executors and the (deprecated) handler invocation hook. Added the experimental::as_single completion token adapter. Added support for MSG_NOSIGNAL on more platforms by using _POSIX_VERSION to detect whether it is supported. Added the ability to compile using libpthread on Windows. Added workarounds for the Intel C++ compiler. Added more support for detecting and optimising for handlers that have no custom executor. Reduced lock contention for timer cancellation on Windows. Reinstated a previously removed null-pointer check, as it had a measurable impact on performance. Fixed the executor concept to test for a const-qualified execute(). Fixed any_executor support for builds without RTTI support. Fixed the thread_pool unit test to work without RTTI support. Fixed C++20 coroutines compatibility with clang on Windows. Fixed some compatibility issues with Windows Runtime. Fixed shadow name warnings caused by addition of asio::query. Fixed a "logical ‘or’ of equal expressions" warning on linux. Fixed a benign switch fallthrough warning. Added missing push/pop_options.hpp includes. Suppressed zero-as-null-pointer-constant warnings. Fixed a comma-operator warning. Updated the documentation to clarify when the select reactor is used on Windows. Fixed potential ambiguity caused by any_executor comparisons and conversion. Added detection of non-experimental C++20 coroutines on MSVC 19.8. Fixed compatibility with uClibc. Fixed strand<> adaptation of Networking TS executors when targeting older C++ versions or less conformant compilers. Consult the Revision History for further details. Atomic: Implemented SSE2 and SSE4.1 versions of address lookup algorithm, which is used in the internal lock pool implementation. This may improve performance of waiting and notifying operations in heavily contended cases. Fixed a possible compilation error on AArch64 targets caused by incorrect instructions generated for bitwise (logical) operations with immediate constants. (#41) Beast: This update brings bug fixes and support for the BOOST_ASIO_ENBALE_HANDLER_TRACKING compile flag from Boost.Asio: 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. Container: New devector container. Fixed bugs/issues: #152 Tree-based containers have troubles with move-only types. #156 Compile error with vector. PR#157 Add missing include. #159: pmr::monotonic_buffer_resource crashes on large single allocations. #160: Usage of uses_allocator needs a remove_cvref_t. #162: small_vector on MSVC x86 call-by-value crash. #161: polymorphic_allocator(memory_resource*) non-standard extension causes headache. PR#163: container_rebind for small_vector with options. #165: Link error with shared library and memory_resource inline members. PR#166: Fix encoding error in copyright headers. PR#167: error: the address of 'msg' will always evaluate as 'true' warning with GCC 4.4. #169: flood of warnings building dlmalloc_ext_2_8_6.c on clang11. Endian: endian_arithmetic no longer inherits from endian_buffer When BOOST_ENDIAN_NO_CTORS is defined, the unaligned endian_buffer and endian_arithmetic are C++03 PODs, to enable use of __attribute__((packed)) Filesystem: New: Added creation_time operation, which allows to obtain file creation time. (Inspired by PR#134) The returned value of last_write_time(p, ec) operation in case of failure has been changed to a minimal value representable by std::time_t instead of -1. The returned value of hard_link_count(p, ec) operation in case of failure has been changed to static_cast<uintmax_t>(-1) instead of 0. On POSIX systems, file_size will now indicate error code errc::function_not_supported if the path resolves to a non-regular file. Previously, errc::operation_not_permitted was reported. On Linux, many operations now use statx system call internally, when possible, which allows to reduce the amount of information queried from the filesystem and potentially improve performance. The statx system call was introduced in Linux kernel 4.11. Removed const-qualification from return types of some path methods. This could prevent move construction and move assignment at the call site in some cases. (#160) On OpenBSD 4.4 and newer, use statvfs system call to obtain filesystem space information. (Inspired by PR#162) On Windows, space now returns with an error if the provided path does not idendify an existing file. (#167) Geometry: WARNING: Following the deprecation notice of C++03 issued with Boost 1.73, from now on the Boost.Geometry requires a capable C++14 compiler. Improvements PR#726 Umbrella strategies for area, envelope, expand (undocumented for now). PR#733 Added example of adaptation of std::array<> to Point concept (thanks to Ben FrantzDale). PR#745 constexpr added in geometries and arithmetic. PR#747 Added optional traits::make (undocumented for now). PR#748 Modernized usage of type traits. PR#759 MPL_ASSERT replaced with standard static_assert. PR#767 Modernized usage of tuple. Solved issues #716 Dangling proxy references. Bugfixes Various fixes in set operations and buffer. GIL: BREAKING: In next release, we are going to drop support for GCC 5. We may also change the required minimum C++ version from C++11 to C++14. Histogram: This update brings Bug-fixes for corner-cases Small documentation improvements Fixes for new warnings from latest compilers and when compiling against the C++20 standard See the full Release Notes for a complete list of changes. Interprocess: Fixed bugs: #127: static assertion failure with boost interprocess 1.74 and basic_managed_shared_memory. Intrusive: Fixed bugs: PR#48: MSVC "assignment within conditional" warning fix. PR#49: Fix empty control statement warnings. #52: Invalid casting in BOOST_INTRUSIVE_BSR_INTRINSIC. Log: Bug fixes: Corrected the file counter that would be used in text_file_backend when generating the target file name (based on the pattern set by set_target_file_name_pattern method) when the log file is rotated. (#125) Replaced a volatile version counter in basic_sink_frontend with an atomic. (#128) In the asynchronous_sink frontend, resolved a possible conflict between flush and run methods, if run is called from a user's thread instead of the internal dedicated thread spawned by the frontend. (#131) See changelog for more details. Move: Fixed bugs: #30: (void) C-cast is a non-portable way of suppressing compiler warnings. Mp11: Added mp_pairwise_fold (suggested by Barry Revzin) Removed mp_invoke (use mp_invoke_q) Optional: boost::none is constexpr-declared. Fixed issue #78. Outcome: Announcements: After a year and three major Boost releases announcing this upcoming change, this is the FINAL RELEASE of the v2.1 branch. From Boost 1.76 onwards, the v2.2 branch becomes the default. This branch has a number of major breaking changes to Outcome v2.1, see the documentation for details. Enhancements: The ADL discovered event hooks have been replaced with policy-specified event hooks instead. This is due to brittleness (where hooks would quietly self-disable if somebody changed something), compiler bugs (a difference in compiler settings causes the wrong hooks, or some but not all hooks, to get discovered), and end user difficulty in using them at all. The policy-specified event hooks can be told to default to ADL discovered hooks for backwards compatibility: set OUTCOME_ENABLE_LEGACY_SUPPORT_FOR to less than 220 to enable emulation. Improve configuring OUTCOME_GCC6_CONCEPT_BOOL. Older GCCs had boolean based concepts syntax, whereas newer GCCs are standards conforming. However the precise logic of when to use legacy and conforming syntax was not well understood, which caused Outcome to fail to compile depending on what options you pass to GCC. The new logic always uses the legacy syntax if on GCC 8 or older, otherwise we use conforming syntax if and only if GCC is in C++ 20 mode or later. This hopefully will resolve the corner case build failures on GCC. Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. #236 In the Coroutine support the final_suspend() was not noexcept, despite being required to be so in the C++ 20 standard. This has been fixed, but only if your compiler implements noop_coroutine. Additionally, if noop_coroutine is available, we use the much more efficient coroutine handle returning variant of await_suspend() which should significantly improve codegen and context switching performance. Polygon: C++20 fixes for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) Preprocessor: When variadic data is empty in C++20 mode with __VA_OPT__ support the variadic size has been corrected to be 0. This also means that in this C++20 mode it is now valid to convert to and from empty arrays and lists and variadic data. The end-user can read the "C++20 Support For Variadic Macros" part of the "variadic macros" topic for more information about empty variadic data in the library. The macro BOOST_PP_IS_STANDARD() has been added for identifying if the currently used preprocessor is a C++ standard conforming preprocessor. A number of preprocessors which generally work correctly with the library but need various internal workarounds, including the currently default VC++ preprocessor, are not considered C++ standard conforming preprocessors. However most preprocessors, including among others gcc, clang, and the new but currently non-default VC++ preprocessor in VS2019, are C++ standard conforming preprocessors. For C++ standard conforming preprocessors a number of the limits defined in the config/limits.hpp can now be changed to higher amounts for a TU. The end-user should read the "limitations" topic to understand how and which limits can be changed. For C++ standard conforming preprocessors, in order to allow the maximum number of FOR and WHILE iterations, the beginning 'r' and 'd' iteration numbers in the user-defined macros start at 1 and not 2, as it did in previous releases. This could be a breaking change if these iteration numbers are used in the user-defined macros ( they probably would not be ), but the change was necessary to fix some arcane bugs when dealing with numerical/logical operations with maximum numbers as well to allow the user-defined macros to be called the correct possible maximum number of times. For non-C++ conforming preprocessors, this change was not made because those non-conforming C++ preprocessors generally have limitations which disallow the maximum number of looping constructs to be run, and it was felt not to introduce a possible breaking change to those more fragile preprocessors would be better. It was also felt that besides fixing some arcane preprocessor bugs and providing the possible maximum number of user-defined macro invocations, this change could be made because it has never been documented what the starting 'r' and 'd' iteration numbers actually are but only that these numbers are incremented for each iteration. The library has been upgraded to assume variadic macro support for any compiler working with the library. Ostensibly this means that the library is now a C++11 on up library, yet most of the major compilers, including gcc, clang, and VC++, also support variadic macros in C++98/C++03 mode as long as strict compliance to C++98/C++03 is not turned on when using one of those compilers. Rational: Fix Rational operators to not break under new C++20 operator== rewriting rules. (Glen Fernandes) Signals2: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes) System: The platform-specific headers windows_error.hpp, linux_error.hpp, and cygwin_error.hpp emit deprecation messages and are slated for removal. The old names for generic_category() and system_category() emit deprecation messages and are slated for removal. error_condition::failed is deprecated and is slated for removal. operator bool() for error_condition has been reverted to its old meaning of value() != 0. This is done for compatibility with std::error_condition as the next release is expected to improve interoperability with <system_error> even further. Note that this does not affect error_code::failed, which is still alive and well. The overload of error_condition::message that takes a buffer is deprecated and is slated for removal, for the same reasons. Note that this does not affect error_code::message. uBLAS: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes and Conrad Poelman) VMD: The VMD number parsing has been upgraded to support the ability for the end-user to change the number limits in the Preprocessor library. The macro BOOST_VMD_IS_GENERAL_IDENTIFIER has been added to support the parsing of input that represents a preprocessor token which matches the VMD identifier syntax, without having to register the identifier as a specific identifier. Wave: Added new C++20 tokens, including the spaceship operator <=> Fixed bugs: #94: fix incorrect behavior of __LINE__ and __FILE__ under rescanning Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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Known Issues Boost.Operators is currently incompatible with C++20 compilers, which in some cases may manifest as an infinite recursion or infinite loop in runtime when a comparison operator is called. The problem is ... [More] caused by the new operator rewriting behavior introduced in C++20. As a workaround, users are advised to target C++17 or older C++ standard. More details can be found in #65. New Libraries JSON: JSON parsing, serialization, and DOM in C++11, from Vinnie Falco and Krystian Stasiowski. Fast compilation requiring only C++11 Easy and safe modern API with allocator support Compile without Boost, define BOOST_JSON_STANDALONE Optional header-only, without linking to a library LEAF: A lightweight error-handling library for C++11, from Emil Dotchevski. Small single-header format, no dependencies. Designed for maximum efficiency ("happy" path and "sad" path). No dynamic memory allocations, even with heavy payloads. O(1) transport of arbitrary error types (independent of call stack depth). Can be used with or without exception handling. PFR: Basic reflection without macro or boilerplate code for user defined types, from Antony Polukhin. Updated Libraries Asio: Enabled support for UNIX domain sockets on Windows. Added executor-converting construction and assignment to ip::basic_resolver. Added compatibility between polymorphic executors and the (deprecated) handler invocation hook. Added the experimental::as_single completion token adapter. Added support for MSG_NOSIGNAL on more platforms by using _POSIX_VERSION to detect whether it is supported. Added the ability to compile using libpthread on Windows. Added workarounds for the Intel C++ compiler. Added more support for detecting and optimising for handlers that have no custom executor. Reduced lock contention for timer cancellation on Windows. Reinstated a previously removed null-pointer check, as it had a measurable impact on performance. Fixed the executor concept to test for a const-qualified execute(). Fixed any_executor support for builds without RTTI support. Fixed the thread_pool unit test to work without RTTI support. Fixed C++20 coroutines compatibility with clang on Windows. Fixed some compatibility issues with Windows Runtime. Fixed shadow name warnings caused by addition of asio::query. Fixed a "logical ‘or’ of equal expressions" warning on linux. Fixed a benign switch fallthrough warning. Added missing push/pop_options.hpp includes. Suppressed zero-as-null-pointer-constant warnings. Fixed a comma-operator warning. Updated the documentation to clarify when the select reactor is used on Windows. Fixed potential ambiguity caused by any_executor comparisons and conversion. Added detection of non-experimental C++20 coroutines on MSVC 19.8. Fixed compatibility with uClibc. Fixed strand<> adaptation of Networking TS executors when targeting older C++ versions or less conformant compilers. Consult the Revision History for further details. Atomic: Implemented SSE2 and SSE4.1 versions of address lookup algorithm, which is used in the internal lock pool implementation. This may improve performance of waiting and notifying operations in heavily contended cases. Fixed a possible compilation error on AArch64 targets caused by incorrect instructions generated for bitwise (logical) operations with immediate constants. (#41) Beast: This update brings bug fixes and support for the BOOST_ASIO_ENBALE_HANDLER_TRACKING compile flag from Boost.Asio: 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. Container: New devector container. Fixed bugs/issues: #152 Tree-based containers have troubles with move-only types. #156 Compile error with vector. PR#157 Add missing include. #159: pmr::monotonic_buffer_resource crashes on large single allocations. #160: Usage of uses_allocator needs a remove_cvref_t. #162: small_vector on MSVC x86 call-by-value crash. #161: polymorphic_allocator(memory_resource*) non-standard extension causes headache. PR#163: container_rebind for small_vector with options. #165: Link error with shared library and memory_resource inline members. PR#166: Fix encoding error in copyright headers. PR#167: error: the address of 'msg' will always evaluate as 'true' warning with GCC 4.4. #169: flood of warnings building dlmalloc_ext_2_8_6.c on clang11. Endian: endian_arithmetic no longer inherits from endian_buffer When BOOST_ENDIAN_NO_CTORS is defined, the unaligned endian_buffer and endian_arithmetic are C++03 PODs, to enable use of __attribute__((packed)) Filesystem: New: Added creation_time operation, which allows to obtain file creation time. (Inspired by PR#134) The returned value of last_write_time(p, ec) operation in case of failure has been changed to a minimal value representable by std::time_t instead of -1. The returned value of hard_link_count(p, ec) operation in case of failure has been changed to static_cast<uintmax_t>(-1) instead of 0. On POSIX systems, file_size will now indicate error code errc::function_not_supported if the path resolves to a non-regular file. Previously, errc::operation_not_permitted was reported. On Linux, many operations now use statx system call internally, when possible, which allows to reduce the amount of information queried from the filesystem and potentially improve performance. The statx system call was introduced in Linux kernel 4.11. Removed const-qualification from return types of some path methods. This could prevent move construction and move assignment at the call site in some cases. (#160) On OpenBSD 4.4 and newer, use statvfs system call to obtain filesystem space information. (Inspired by PR#162) On Windows, space now returns with an error if the provided path does not idendify an existing file. (#167) Geometry: WARNING: Following the deprecation notice of C++03 issued with Boost 1.73, from now on the Boost.Geometry requires a capable C++14 compiler. GIL: BREAKING: In next release, we are going to drop support for GCC 5. We may also change the required minimum C++ version from C++11 to C++14. Histogram: This update brings Bug-fixes for corner-cases Small documentation improvements Fixes for new warnings from latest compilers and when compiling against the C++20 standard See the full Release Notes for a complete list of changes. Interprocess: Fixed bugs: #127: static assertion failure with boost interprocess 1.74 and basic_managed_shared_memory. Intrusive: Fixed bugs: PR#48: MSVC "assignment within conditional" warning fix. PR#49: Fix empty control statement warnings. #52: Invalid casting in BOOST_INTRUSIVE_BSR_INTRINSIC. Log: Bug fixes: Corrected the file counter that would be used in text_file_backend when generating the target file name (based on the pattern set by set_target_file_name_pattern method) when the log file is rotated. (#125) Replaced a volatile version counter in basic_sink_frontend with an atomic. (#128) In the asynchronous_sink frontend, resolved a possible conflict between flush and run methods, if run is called from a user's thread instead of the internal dedicated thread spawned by the frontend. (#131) See changelog for more details. Move: Fixed bugs: #30: (void) C-cast is a non-portable way of suppressing compiler warnings. Mp11: Added mp_pairwise_fold (suggested by Barry Revzin) Removed mp_invoke (use mp_invoke_q) Optional: boost::none is constexpr-declared. Fixed issue #78. Outcome: Announcements: After a year and three major Boost releases announcing this upcoming change, this is the FINAL RELEASE of the v2.1 branch. From Boost 1.76 onwards, the v2.2 branch becomes the default. This branch has a number of major breaking changes to Outcome v2.1, see the documentation for details. Enhancements: The ADL discovered event hooks have been replaced with policy-specified event hooks instead. This is due to brittleness (where hooks would quietly self-disable if somebody changed something), compiler bugs (a difference in compiler settings causes the wrong hooks, or some but not all hooks, to get discovered), and end user difficulty in using them at all. The policy-specified event hooks can be told to default to ADL discovered hooks for backwards compatibility: set OUTCOME_ENABLE_LEGACY_SUPPORT_FOR to less than 220 to enable emulation. Improve configuring OUTCOME_GCC6_CONCEPT_BOOL. Older GCCs had boolean based concepts syntax, whereas newer GCCs are standards conforming. However the precise logic of when to use legacy and conforming syntax was not well understood, which caused Outcome to fail to compile depending on what options you pass to GCC. The new logic always uses the legacy syntax if on GCC 8 or older, otherwise we use conforming syntax if and only if GCC is in C++ 20 mode or later. This hopefully will resolve the corner case build failures on GCC. Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. #236 In the Coroutine support the final_suspend() was not noexcept, despite being required to be so in the C++ 20 standard. This has been fixed, but only if your compiler implements noop_coroutine. Additionally, if noop_coroutine is available, we use the much more efficient coroutine handle returning variant of await_suspend() which should significantly improve codegen and context switching performance. Polygon: C++20 fixes for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) Preprocessor: When variadic data is empty in C++20 mode with __VA_OPT__ support the variadic size has been corrected to be 0. This also means that in this C++20 mode it is now valid to convert to and from empty arrays and lists and variadic data. The end-user can read the "C++20 Support For Variadic Macros" part of the "variadic macros" topic for more information about empty variadic data in the library. The macro BOOST_PP_IS_STANDARD() has been added for identifying if the currently used preprocessor is a C++ standard conforming preprocessor. A number of preprocessors which generally work correctly with the library but need various internal workarounds, including the currently default VC++ preprocessor, are not considered C++ standard conforming preprocessors. However most preprocessors, including among others gcc, clang, and the new but currently non-default VC++ preprocessor in VS2019, are C++ standard conforming preprocessors. For C++ standard conforming preprocessors a number of the limits defined in the config/limits.hpp can now be changed to higher amounts for a TU. The end-user should read the "limitations" topic to understand how and which limits can be changed. For C++ standard conforming preprocessors, in order to allow the maximum number of FOR and WHILE iterations, the beginning 'r' and 'd' iteration numbers in the user-defined macros start at 1 and not 2, as it did in previous releases. This could be a breaking change if these iteration numbers are used in the user-defined macros ( they probably would not be ), but the change was necessary to fix some arcane bugs when dealing with numerical/logical operations with maximum numbers as well to allow the user-defined macros to be called the correct possible maximum number of times. For non-C++ conforming preprocessors, this change was not made because those non-conforming C++ preprocessors generally have limitations which disallow the maximum number of looping constructs to be run, and it was felt not to introduce a possible breaking change to those more fragile preprocessors would be better. It was also felt that besides fixing some arcane preprocessor bugs and providing the possible maximum number of user-defined macro invocations, this change could be made because it has never been documented what the starting 'r' and 'd' iteration numbers actually are but only that these numbers are incremented for each iteration. The library has been upgraded to assume variadic macro support for any compiler working with the library. Ostensibly this means that the library is now a C++11 on up library, yet most of the major compilers, including gcc, clang, and VC++, also support variadic macros in C++98/C++03 mode as long as strict compliance to C++98/C++03 is not turned on when using one of those compilers. Rational: Fix Rational operators to not break under new C++20 operator== rewriting rules. (Glen Fernandes) Signals2: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes) System: The platform-specific headers windows_error.hpp, linux_error.hpp, and cygwin_error.hpp emit deprecation messages and are slated for removal. The old names for generic_category() and system_category() emit deprecation messages and are slated for removal. error_condition::failed is deprecated and is slated for removal. operator bool() for error_condition has been reverted to its old meaning of value() != 0. This is done for compatibility with std::error_condition as the next release is expected to improve interoperability with <system_error> even further. Note that this does not affect error_code::failed, which is still alive and well. The overload of error_condition::message that takes a buffer is deprecated and is slated for removal, for the same reasons. Note that this does not affect error_code::message. uBLAS: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes and Conrad Poelman) VMD: The VMD number parsing has been upgraded to support the ability for the end-user to change the number limits in the Preprocessor library. The macro BOOST_VMD_IS_GENERAL_IDENTIFIER has been added to support the parsing of input that represents a preprocessor token which matches the VMD identifier syntax, without having to register the identifier as a specific identifier. Wave: Added new C++20 tokens, including the spaceship operator <=> Fixed bugs: #94: fix incorrect behavior of __LINE__ and __FILE__ under rescanning Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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Known Issues Boost.Operators is currently incompatible with C++20 compilers, which in some cases may manifest as an infinite recursion or infinite loop in runtime when a comparison operator is called. The problem is ... [More] caused by the new operator rewriting behavior introduced in C++20. As a workaround, users are advised to target C++17 or older C++ standard. More details can be found in #65. New Libraries JSON: JSON parsing, serialization, and DOM in C++11, from Vinnie Falco and Krystian Stasiowski. Fast compilation requiring only C++11 Easy and safe modern API with allocator support Compile without Boost, define BOOST_JSON_STANDALONE Optional header-only, without linking to a library LEAF: A lightweight error-handling library for C++11, from Emil Dotchevski. Small single-header format, no dependencies. Designed for maximum efficiency ("happy" path and "sad" path). No dynamic memory allocations, even with heavy payloads. O(1) transport of arbitrary error types (independent of call stack depth). Can be used with or without exception handling. PFR: Basic reflection without macro or boilerplate code for user defined types, from Antony Polukhin. Updated Libraries Asio: Enabled support for UNIX domain sockets on Windows. Added executor-converting construction and assignment to ip::basic_resolver. Added compatibility between polymorphic executors and the (deprecated) handler invocation hook. Added the experimental::as_single completion token adapter. Added support for MSG_NOSIGNAL on more platforms by using _POSIX_VERSION to detect whether it is supported. Added the ability to compile using libpthread on Windows. Added workarounds for the Intel C++ compiler. Added more support for detecting and optimising for handlers that have no custom executor. Reduced lock contention for timer cancellation on Windows. Reinstated a previously removed null-pointer check, as it had a measurable impact on performance. Fixed the executor concept to test for a const-qualified execute(). Fixed any_executor support for builds without RTTI support. Fixed the thread_pool unit test to work without RTTI support. Fixed C++20 coroutines compatibility with clang on Windows. Fixed some compatibility issues with Windows Runtime. Fixed shadow name warnings caused by addition of asio::query. Fixed a "logical ‘or’ of equal expressions" warning on linux. Fixed a benign switch fallthrough warning. Added missing push/pop_options.hpp includes. Suppressed zero-as-null-pointer-constant warnings. Fixed a comma-operator warning. Updated the documentation to clarify when the select reactor is used on Windows. Fixed potential ambiguity caused by any_executor comparisons and conversion. Added detection of non-experimental C++20 coroutines on MSVC 19.8. Fixed compatibility with uClibc. Fixed strand<> adaptation of Networking TS executors when targeting older C++ versions or less conformant compilers. Consult the Revision History for further details. Atomic: Implemented SSE2 and SSE4.1 versions of address lookup algorithm, which is used in the internal lock pool implementation. This may improve performance of waiting and notifying operations in heavily contended cases. Fixed a possible compilation error on AArch64 targets caused by incorrect instructions generated for bitwise (logical) operations with immediate constants. (#41) Beast: This update brings bug fixes and support for the BOOST_ASIO_ENBALE_HANDLER_TRACKING compile flag from Boost.Asio: 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. Container: New devector container. Fixed bugs/issues: #152 Tree-based containers have troubles with move-only types. #156 Compile error with vector. PR#157 Add missing include. #159: pmr::monotonic_buffer_resource crashes on large single allocations. #160: Usage of uses_allocator needs a remove_cvref_t. #162: small_vector on MSVC x86 call-by-value crash. #161: polymorphic_allocator(memory_resource*) non-standard extension causes headache. PR#163: container_rebind for small_vector with options. #165: Link error with shared library and memory_resource inline members. PR#166: Fix encoding error in copyright headers. PR#167: error: the address of 'msg' will always evaluate as 'true' warning with GCC 4.4. #169: flood of warnings building dlmalloc_ext_2_8_6.c on clang11. Endian: endian_arithmetic no longer inherits from endian_buffer When BOOST_ENDIAN_NO_CTORS is defined, the unaligned endian_buffer and endian_arithmetic are C++03 PODs, to enable use of __attribute__((packed)) Filesystem: New: Added creation_time operation, which allows to obtain file creation time. (Inspired by PR#134) The returned value of last_write_time(p, ec) operation in case of failure has been changed to a minimal value representable by std::time_t instead of -1. The returned value of hard_link_count(p, ec) operation in case of failure has been changed to static_cast<uintmax_t>(-1) instead of 0. On POSIX systems, file_size will now indicate error code errc::function_not_supported if the path resolves to a non-regular file. Previously, errc::operation_not_permitted was reported. On Linux, many operations now use statx system call internally, when possible, which allows to reduce the amount of information queried from the filesystem and potentially improve performance. The statx system call was introduced in Linux kernel 4.11. Removed const-qualification from return types of some path methods. This could prevent move construction and move assignment at the call site in some cases. (#160) On OpenBSD 4.4 and newer, use statvfs system call to obtain filesystem space information. (Inspired by PR#162) On Windows, space now returns with an error if the provided path does not idendify an existing file. (#167) GIL: BREAKING: In next release, we are going to drop support for GCC 5. We may also change the required minimum C++ version from C++11 to C++14. Histogram: This update brings Bug-fixes for corner-cases Small documentation improvements Fixes for new warnings from latest compilers and when compiling against the C++20 standard See the full Release Notes for a complete list of changes. Interprocess: Fixed bugs: #127: static assertion failure with boost interprocess 1.74 and basic_managed_shared_memory. Intrusive: Fixed bugs: PR#48: MSVC "assignment within conditional" warning fix. PR#49: Fix empty control statement warnings. #52: Invalid casting in BOOST_INTRUSIVE_BSR_INTRINSIC. Log: Bug fixes: Corrected the file counter that would be used in text_file_backend when generating the target file name (based on the pattern set by set_target_file_name_pattern method) when the log file is rotated. (#125) Replaced a volatile version counter in basic_sink_frontend with an atomic. (#128) In the asynchronous_sink frontend, resolved a possible conflict between flush and run methods, if run is called from a user's thread instead of the internal dedicated thread spawned by the frontend. (#131) See changelog for more details. Move: Fixed bugs: #30: (void) C-cast is a non-portable way of suppressing compiler warnings. Mp11: Added mp_pairwise_fold (suggested by Barry Revzin) Removed mp_invoke (use mp_invoke_q) Optional: boost::none is constexpr-declared. Fixed issue #78. Outcome: Announcements: After a year and three major Boost releases announcing this upcoming change, this is the FINAL RELEASE of the v2.1 branch. From Boost 1.76 onwards, the v2.2 branch becomes the default. This branch has a number of major breaking changes to Outcome v2.1, see the documentation for details. Enhancements: The ADL discovered event hooks have been replaced with policy-specified event hooks instead. This is due to brittleness (where hooks would quietly self-disable if somebody changed something), compiler bugs (a difference in compiler settings causes the wrong hooks, or some but not all hooks, to get discovered), and end user difficulty in using them at all. The policy-specified event hooks can be told to default to ADL discovered hooks for backwards compatibility: set OUTCOME_ENABLE_LEGACY_SUPPORT_FOR to less than 220 to enable emulation. Improve configuring OUTCOME_GCC6_CONCEPT_BOOL. Older GCCs had boolean based concepts syntax, whereas newer GCCs are standards conforming. However the precise logic of when to use legacy and conforming syntax was not well understood, which caused Outcome to fail to compile depending on what options you pass to GCC. The new logic always uses the legacy syntax if on GCC 8 or older, otherwise we use conforming syntax if and only if GCC is in C++ 20 mode or later. This hopefully will resolve the corner case build failures on GCC. Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. #236 In the Coroutine support the final_suspend() was not noexcept, despite being required to be so in the C++ 20 standard. This has been fixed, but only if your compiler implements noop_coroutine. Additionally, if noop_coroutine is available, we use the much more efficient coroutine handle returning variant of await_suspend() which should significantly improve codegen and context switching performance. Polygon: C++20 fixes for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) Preprocessor: When variadic data is empty in C++20 mode with __VA_OPT__ support the variadic size has been corrected to be 0. This also means that in this C++20 mode it is now valid to convert to and from empty arrays and lists and variadic data. The end-user can read the "C++20 Support For Variadic Macros" part of the "variadic macros" topic for more information about empty variadic data in the library. The macro BOOST_PP_IS_STANDARD() has been added for identifying if the currently used preprocessor is a C++ standard conforming preprocessor. A number of preprocessors which generally work correctly with the library but need various internal workarounds, including the currently default VC++ preprocessor, are not considered C++ standard conforming preprocessors. However most preprocessors, including among others gcc, clang, and the new but currently non-default VC++ preprocessor in VS2019, are C++ standard conforming preprocessors. For C++ standard conforming preprocessors a number of the limits defined in the config/limits.hpp can now be changed to higher amounts for a TU. The end-user should read the "limitations" topic to understand how and which limits can be changed. For C++ standard conforming preprocessors, in order to allow the maximum number of FOR and WHILE iterations, the beginning 'r' and 'd' iteration numbers in the user-defined macros start at 1 and not 2, as it did in previous releases. This could be a breaking change if these iteration numbers are used in the user-defined macros ( they probably would not be ), but the change was necessary to fix some arcane bugs when dealing with numerical/logical operations with maximum numbers as well to allow the user-defined macros to be called the correct possible maximum number of times. For non-C++ conforming preprocessors, this change was not made because those non-conforming C++ preprocessors generally have limitations which disallow the maximum number of looping constructs to be run, and it was felt not to introduce a possible breaking change to those more fragile preprocessors would be better. It was also felt that besides fixing some arcane preprocessor bugs and providing the possible maximum number of user-defined macro invocations, this change could be made because it has never been documented what the starting 'r' and 'd' iteration numbers actually are but only that these numbers are incremented for each iteration. The library has been upgraded to assume variadic macro support for any compiler working with the library. Ostensibly this means that the library is now a C++11 on up library, yet most of the major compilers, including gcc, clang, and VC++, also support variadic macros in C++98/C++03 mode as long as strict compliance to C++98/C++03 is not turned on when using one of those compilers. Rational: Fix Rational operators to not break under new C++20 operator== rewriting rules. (Glen Fernandes) Signals2: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes) System: The platform-specific headers windows_error.hpp, linux_error.hpp, and cygwin_error.hpp emit deprecation messages and are slated for removal. The old names for generic_category() and system_category() emit deprecation messages and are slated for removal. error_condition::failed is deprecated and is slated for removal. operator bool() for error_condition has been reverted to its old meaning of value() != 0. This is done for compatibility with std::error_condition as the next release is expected to improve interoperability with <system_error> even further. Note that this does not affect error_code::failed, which is still alive and well. The overload of error_condition::message that takes a buffer is deprecated and is slated for removal, for the same reasons. Note that this does not affect error_code::message. uBLAS: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes and Conrad Poelman) VMD: The VMD number parsing has been upgraded to support the ability for the end-user to change the number limits in the Preprocessor library. The macro BOOST_VMD_IS_GENERAL_IDENTIFIER has been added to support the parsing of input that represents a preprocessor token which matches the VMD identifier syntax, without having to register the identifier as a specific identifier. Wave: Added new C++20 tokens, including the spaceship operator <=> Fixed bugs: #94: fix incorrect behavior of __LINE__ and __FILE__ under rescanning Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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Known Issues Boost.Operators is currently incompatible with C++20 compilers, which in some cases may manifest as an infinite recursion or infinite loop in runtime when a comparison operator is called. The problem is ... [More] caused by the new operator rewriting behavior introduced in C++20. As a workaround, users are advised to target C++17 or older C++ standard. More details can be found in #65. New Libraries JSON: JSON parsing, serialization, and DOM in C++11, from Vinnie Falco and Krystian Stasiowski. Fast compilation requiring only C++11 Easy and safe modern API with allocator support Compile without Boost, define BOOST_JSON_STANDALONE Optional header-only, without linking to a library LEAF: A lightweight error-handling library for C++11, from Emil Dotchevski. Small single-header format, no dependencies. Designed for maximum efficiency ("happy" path and "sad" path). No dynamic memory allocations, even with heavy payloads. O(1) transport of arbitrary error types (independent of call stack depth). Can be used with or without exception handling. PFR: Basic reflection without macro or boilerplate code for user defined types, from Antony Polukhin. Updated Libraries Asio: Enabled support for UNIX domain sockets on Windows. Added executor-converting construction and assignment to ip::basic_resolver. Added compatibility between polymorphic executors and the (deprecated) handler invocation hook. Added the experimental::as_single completion token adapter. Added support for MSG_NOSIGNAL on more platforms by using _POSIX_VERSION to detect whether it is supported. Added the ability to compile using libpthread on Windows. Added workarounds for the Intel C++ compiler. Added more support for detecting and optimising for handlers that have no custom executor. Reduced lock contention for timer cancellation on Windows. Reinstated a previously removed null-pointer check, as it had a measurable impact on performance. Fixed the executor concept to test for a const-qualified execute(). Fixed any_executor support for builds without RTTI support. Fixed the thread_pool unit test to work without RTTI support. Fixed C++20 coroutines compatibility with clang on Windows. Fixed some compatibility issues with Windows Runtime. Fixed shadow name warnings caused by addition of asio::query. Fixed a "logical ‘or’ of equal expressions" warning on linux. Fixed a benign switch fallthrough warning. Added missing push/pop_options.hpp includes. Suppressed zero-as-null-pointer-constant warnings. Fixed a comma-operator warning. Updated the documentation to clarify when the select reactor is used on Windows. Fixed potential ambiguity caused by any_executor comparisons and conversion. Added detection of non-experimental C++20 coroutines on MSVC 19.8. Fixed compatibility with uClibc. Fixed strand<> adaptation of Networking TS executors when targeting older C++ versions or less conformant compilers. Consult the Revision History for further details. Atomic: Implemented SSE2 and SSE4.1 versions of address lookup algorithm, which is used in the internal lock pool implementation. This may improve performance of waiting and notifying operations in heavily contended cases. Fixed a possible compilation error on AArch64 targets caused by incorrect instructions generated for bitwise (logical) operations with immediate constants. (#41) Beast: This update brings bug fixes and support for the BOOST_ASIO_ENBALE_HANDLER_TRACKING compile flag from Boost.Asio: 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. Container: New devector container. Fixed bugs/issues: #152 Tree-based containers have troubles with move-only types. #156 Compile error with vector. PR#157 Add missing include. #159: pmr::monotonic_buffer_resource crashes on large single allocations. #160: Usage of uses_allocator needs a remove_cvref_t. #162: small_vector on MSVC x86 call-by-value crash. #161: polymorphic_allocator(memory_resource*) non-standard extension causes headache. PR#163: container_rebind for small_vector with options. #165: Link error with shared library and memory_resource inline members. PR#166: Fix encoding error in copyright headers. PR#167: error: the address of 'msg' will always evaluate as 'true' warning with GCC 4.4. #169: flood of warnings building dlmalloc_ext_2_8_6.c on clang11. Endian: endian_arithmetic no longer inherits from endian_buffer When BOOST_ENDIAN_NO_CTORS is defined, the unaligned endian_buffer and endian_arithmetic are C++03 PODs, to enable use of __attribute__((packed)) Filesystem: New: Added creation_time operation, which allows to obtain file creation time. (Inspired by PR#134) The returned value of last_write_time(p, ec) operation in case of failure has been changed to a minimal value representable by std::time_t instead of -1. The returned value of hard_link_count(p, ec) operation in case of failure has been changed to static_cast<uintmax_t>(-1) instead of 0. On POSIX systems, file_size will now indicate error code errc::function_not_supported if the path resolves to a non-regular file. Previously, errc::operation_not_permitted was reported. On Linux, many operations now use statx system call internally, when possible, which allows to reduce the amount of information queried from the filesystem and potentially improve performance. The statx system call was introduced in Linux kernel 4.11. Removed const-qualification from return types of some path methods. This could prevent move construction and move assignment at the call site in some cases. (#160) On OpenBSD 4.4 and newer, use statvfs system call to obtain filesystem space information. (Inspired by PR#162) On Windows, space now returns with an error if the provided path does not idendify an existing file. (#167) GIL: BREAKING: In next release, we are going to drop support for GCC 5. We may also change the required minimum C++ version from C++11 to C++14. Histogram: This update brings Bug-fixes for corner-cases Small documentation improvements Fixes for new warnings from latest compilers and when compiling against the C++20 standard See the full Release Notes for a complete list of changes. Interprocess: Fixed bugs: #127: static assertion failure with boost interprocess 1.74 and basic_managed_shared_memory. Intrusive: Fixed bugs: PR#48: MSVC "assignment within conditional" warning fix. PR#49: Fix empty control statement warnings. #52: Invalid casting in BOOST_INTRUSIVE_BSR_INTRINSIC. Log: Bug fixes: Corrected the file counter that would be used in text_file_backend when generating the target file name (based on the pattern set by set_target_file_name_pattern method) when the log file is rotated. (#125) Replaced a volatile version counter in basic_sink_frontend with an atomic. (#128) In the asynchronous_sink frontend, resolved a possible conflict between flush and run methods, if run is called from a user's thread instead of the internal dedicated thread spawned by the frontend. (#131) See changelog for more details. Move: Fixed bugs: #30: (void) C-cast is a non-portable way of suppressing compiler warnings. Mp11: Added mp_pairwise_fold (suggested by Barry Revzin) Removed mp_invoke (use mp_invoke_q) Optional: boost::none is constexpr-declared. Fixed issue #78. Outcome: Announcements: After a year and three major Boost releases announcing this upcoming change, this is the FINAL RELEASE of the v2.1 branch. From Boost 1.76 onwards, the v2.2 branch becomes the default. This branch has a number of major breaking changes to Outcome v2.1, see the documentation for details. Enhancements: The ADL discovered event hooks have been replaced with policy-specified event hooks instead. This is due to brittleness (where hooks would quietly self-disable if somebody changed something), compiler bugs (a difference in compiler settings causes the wrong hooks, or some but not all hooks, to get discovered), and end user difficulty in using them at all. The policy-specified event hooks can be told to default to ADL discovered hooks for backwards compatibility: set OUTCOME_ENABLE_LEGACY_SUPPORT_FOR to less than 220 to enable emulation. Improve configuring OUTCOME_GCC6_CONCEPT_BOOL. Older GCCs had boolean based concepts syntax, whereas newer GCCs are standards conforming. However the precise logic of when to use legacy and conforming syntax was not well understood, which caused Outcome to fail to compile depending on what options you pass to GCC. The new logic always uses the legacy syntax if on GCC 8 or older, otherwise we use conforming syntax if and only if GCC is in C++ 20 mode or later. This hopefully will resolve the corner case build failures on GCC. Bug fixes: Boost.Outcome should now compile with BOOST_NO_EXCEPTIONS defined. Thanks to Emil, maintainer of Boost.Exception, making a change for me, Boost.Outcome should now compile with C++ exceptions globally disabled. You won't be able to use boost::exception_ptr as it can't be included if C++ exceptions are globally disabled. #236 In the Coroutine support the final_suspend() was not noexcept, despite being required to be so in the C++ 20 standard. This has been fixed, but only if your compiler implements noop_coroutine. Additionally, if noop_coroutine is available, we use the much more efficient coroutine handle returning variant of await_suspend() which should significantly improve codegen and context switching performance. Polygon: C++20 fixes for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) Preprocessor: When variadic data is empty in C++20 mode with __VA_OPT__ support the variadic size has been corrected to be 0. This also means that in this C++20 mode it is now valid to convert to and from empty arrays and lists and variadic data. The end-user can read the "C++20 Support For Variadic Macros" part of the "variadic macros" topic for more information about empty variadic data in the library. The macro BOOST_PP_IS_STANDARD() has been added for identifying if the currently used preprocessor is a C++ standard conforming preprocessor. A number of preprocessors which generally work correctly with the library but need various internal workarounds, including the currently default VC++ preprocessor, are not considered C++ standard conforming preprocessors. However most preprocessors, including among others gcc, clang, and the new but currently non-default VC++ preprocessor in VS2019, are C++ standard conforming preprocessors. For C++ standard conforming preprocessors a number of the limits defined in the config/limits.hpp can now be changed to higher amounts for a TU. The end-user should read the "limitations" topic to understand how and which limits can be changed. For C++ standard conforming preprocessors, in order to allow the maximum number of FOR and WHILE iterations, the beginning 'r' and 'd' iteration numbers in the user-defined macros start at 1 and not 2, as it did in previous releases. This could be a breaking change if these iteration numbers are used in the user-defined macros ( they probably would not be ), but the change was necessary to fix some arcane bugs when dealing with numerical/logical operations with maximum numbers as well to allow the user-defined macros to be called the correct possible maximum number of times. For non-C++ conforming preprocessors, this change was not made because those non-conforming C++ preprocessors generally have limitations which disallow the maximum number of looping constructs to be run, and it was felt not to introduce a possible breaking change to those more fragile preprocessors would be better. It was also felt that besides fixing some arcane preprocessor bugs and providing the possible maximum number of user-defined macro invocations, this change could be made because it has never been documented what the starting 'r' and 'd' iteration numbers actually are but only that these numbers are incremented for each iteration. The library has been upgraded to assume variadic macro support for any compiler working with the library. Ostensibly this means that the library is now a C++11 on up library, yet most of the major compilers, including gcc, clang, and VC++, also support variadic macros in C++98/C++03 mode as long as strict compliance to C++98/C++03 is not turned on when using one of those compilers. Rational: Fix Rational operators to not break under new C++20 operator== rewriting rules. (Glen Fernandes) Signals2: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes) System: The platform-specific headers windows_error.hpp, linux_error.hpp, and cygwin_error.hpp emit deprecation messages and are slated for removal. The old names for generic_category() and system_category() emit deprecation messages and are slated for removal. error_condition::failed is deprecated and is slated for removal. operator bool() for error_condition has been reverted to its old meaning of value() != 0. This is done for compatibility with std::error_condition as the next release is expected to improve interoperability with <system_error> even further. Note that this does not affect error_code::failed, which is still alive and well. The overload of error_condition::message that takes a buffer is deprecated and is slated for removal, for the same reasons. Note that this does not affect error_code::message. uBLAS: Correct C++ allocator model support to fix compilation in C++20 standards mode. (Glen Fernandes and Conrad Poelman) VMD: The VMD number parsing has been upgraded to support the ability for the end-user to change the number limits in the Preprocessor library. The macro BOOST_VMD_IS_GENERAL_IDENTIFIER has been added to support the parsing of input that represents a preprocessor token which matches the VMD identifier syntax, without having to register the identifier as a specific identifier. Wave: Added new C++20 tokens, including the spaceship operator <=> Fixed bugs: #94: fix incorrect behavior of __LINE__ and __FILE__ under rescanning Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0, 9.0.0, 10.0.0, 11.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++17: 9.1.0, 10.0.0, 11.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0, 11.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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New Libraries STLInterfaces: A library of CRTP bases to ease the writing of STL views, iterators, and sequence containers, from Zach Laine. Updated Libraries ... [More] Asio: Added an implementation of the proposed standard executors (P0443r13, P1348r0, and P1393r0). Added support for the proposed standard executors to Asio's I/O facilities. The supplied executors now meet the requirements for the proposed standard executors. These classes also continue to meet the existing requirements for the Networking TS model of executors. All I/O objects, asynchronous operations, and utilities will interoperate with both new proposed standard executors, and with existing Networking TS executors. The any_io_executor type alias has been introduced as the default runtime-polymorphic executor for all I/O objects. This defaults to the execution::any_executor<> template. If required for backward compatibility, BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT can be defined to use the old asio::executor polymorphic wrapper instead. Support for the existing Networking TS model of executors can be disabled by defining BOOST_ASIO_NO_TS_EXECUTORS. Added converting move construction and assignment to basic_waitable_timer. Enabled C++20 coroutine support when using gcc 10. Added overloads of co_spawn that launch an awaitable. Added a new constructor overload to use_awaitable_t's default executor adapter, to enable conversion between executor types. Added support for using detached_t as a default completion token, by adding members as_default_on() and as_default_on_t<>. Added a move constructor to ssl::stream<>. Changed ssl::stream<> write operations to linearise gather-write buffer sequences. Added compile-time detection of the deprecated asio_handler_invoke, asio_handler_allocate, and asio_handler_deallocate hooks, when BOOST_ASIO_NO_DEPRECATED is defined. Implemented a number of performance optimisations. Added source location support to handler tracking. Implemented various improvements to the handlerviz.pl tool. Added the handlerlive.pl tool, which processes handler tracking output to produce a list of "live" handlers. Added the handlertree.pl tool, which filters handler tracking output to include only those events in the tree that produced the nominated handlers. Added changes for clang-based Embarcadero C++ compilers. Fixed a deadlock that can occur when multiple threads concurrently initialise the Windows I/O completion port backend. Fixed async_compose to work with copyable handlers when passed by lvalue. Fixed completion signature deduction in co_spawn. Removed a spurious Executor base class from the executor_binder implementation. Various fixes and improvements in the documentation and examples. Consult the Revision History for further details. Atomic: Added missing const qualifiers to some operations in atomic_ref. Added support for yield instruction on ARMv8-A. The instruction is used internally in spin loops to reduce CPU power consumption. Added support for C++20 waiting and notifying operations. The implementation includes generic backend that involves the internal lock pool, as well as specialized backends for Windows, Linux, FreeBSD, DragonFly BSD and NetBSD. Atomic types provide a new method has_native_wait_notify, a static boolean constant always_has_native_wait_notify and a set of capability macros that allow to detect if the implementation supports native waiting and notifying operations for a given type. Changed internal representation of atomic_flag to use 32-bit storage. This allows for more efficient waiting and notifying operations on atomic_flag on some platforms. Added support for build-time configuration of the internal lock pool size. The user can define the BOOST_ATOMIC_LOCK_POOL_SIZE_LOG2 macro to specify binary logarithm of the size of the lock pool. The default value is 8, meaning that the size of the lock pool is 256, up from 64 used in the previous release. Added support for a new set of atomic types dedicated for inter-process communication: ipc_atomic_flag, ipc_atomic and ipc_atomic_ref. Users are recommended to port their code using non-IPC types for inter-process communication to the new types. The new types provide the same set of operations as their non-IPC counterparts, with the following differences: Most operations have an added precondition that is_lock_free returns true for the given atomic object. The library will issue a compile time error if this precondition is known to be not satisfied at compile time. All provided operations are address-free, meaning that the atomic object (in case of ipc_atomic_ref - the referenced object) may be located in process-shared memory or mapped into the same process at multiple different addresses. The new has_native_wait_notify operation and always_has_native_wait_notify constant indicate support for native inter-process waiting and notifying operations. When that support is not present, the operations are implemented with a busy loop, which is less efficient, but still is address-free. A separate set of capability macros is also provided to indicate this support. Added new atomic_unsigned_lock_free and atomic_signed_lock_free types introduced in C++20. The types indicate the atomic object type for an unsigned or signed integer, respectively, that is lock-free and preferably has native support for waiting and notifying operations. Added new gcc assembler backends for ARMv8-A (for both AArch32 and AArch64). The new backends are used to implement operations not supported by compiler intrinsics (including 128-bit operations on AArch64) and can also be used when compiler intrinsics are not available. Both little and big endian targets are supported. AArch64 backend supports extensions defined in ARMv8.1 and ARMv8.3. Added support for big endian targets in the legacy ARM backend based on gcc assembler blocks (this backend is used on ARMv7 and older targets). Previously, the backend assumed little endian memory layout, which is significant for 64-bit operations. Improved performance of seq_cst stores and thread fences on x86 by using lock-prefixed instructions instead of mfence. This means that the operations no longer affect non-temporal stores, which was also not guaranteed before. Use specialized instructions and intrinsics to order non-temporal memory accesses. Fixed capability macros for 80-bit long double on x86 targets not indicating lock-free operations even if 128-bit atomic operations were available. Fixed compilation of gcc asm blocks on Alpha targets. In the gcc __sync* intrinsics backend, fixed that store and load operations of large objects (larger than a pointer size) could be non-atomic. The implementation currently assumes that small objects can be stored with a single instruction atomically on all modern architectures. Beast: This update brings bug fixes and support for the following changes changes in Boost.Asio: Beast supports BOOST_ASIO_NO_DEPRECATED. Define this to help identify areas of your Beast and Asio code which use deprecated Asio interfaces. Beast also supports BOOST_ASIO_NO_TS_EXECUTORS. Define this to identify uses of executors from the now potentially outdated Networking TS Asio will use the Standard Executors model by default. You can prevent this behaviour by defining BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT in which the Networking TS model will be used by default. Setting this flag does not prevent a program from using executors from the Standard Executors model explicitly. 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. Bimap: Correct allocator usage (fixes C++20 compilation). (Glen Fernandes) Config: Implement BOOST_NO_CXX11_OVERRIDE and BOOST_OVERRIDE. (Glen Fernandes) Core: Implemented the allocator access utilities which provide a replacement for allocator_traits with individual traits and functions for each facility. They support the C++11 allocator model when possible and provide a fallback for C++98 compatibility. These are now used in Circular_Buffer, Wave, Lockfree, Heap, Smart_Ptr, Dynamic_Bitset, Format, Bimap and more. (Glen Fernandes) DLL: Multiple fixes for the library_info work on empty shared objects. Compilation fixes for C++98 and C++11 modes (#28). Fixes for smart_library manglings (thanks to XiaLiChao82 #37). Endian: Enabled scoped enumeration types in endian_reverse. Enabled bool, enum, float, double in endian_reverse_inplace. Added an overload of endian_reverse_inplace for arrays. Filesystem: Removed compile-time checks for support for symlinks and hardlink on Windows. Instead, a runtime check is used. (PR#142) Fixed handling of reparse points in canonical and read_symlink on Windows. This also affects other algorithms that involve canonical and read_symlink in their implementation. (PR#100, #85, #99, #123, #125) Fixed that read_symlink on Windows could potentially fail or cause failures elsewhere with a sharing violation error, if the same symlink was opened concurrently. (#138) Fixed that is_symlink(directory_entry) would always return false, even if the directory entry actually referred to a symlink. (PR#148) Added missing status inspection operation overloads for directory_entry and error_code (e.g. is_directory(directory_entry, error_code&)). Removed incorrect noexcept specifications for the overloads not taking the error_code arguments. copy_file implementation has been updated to perform checks on the source and target files, as required by C++20 ([fs.op.copy.file]/4.1). In particular, the operation will fail if the source or target file is not a regular file or the source and target paths identify the same file. copy_file on POSIX systems will now also copy the source file permissions to the target file, if the target file is overwritten. New: Added copy_file implementations based on sendfile and copy_file_range system calls on Linux, which may improve file copying performance, especially on network filesystems. Deprecated: The copy_option enumeration that is used with the copy_file operation is deprecated. As a replacement, the new enum copy_options (note the trailing 's') has been added. The new enum contains values similar to the copy_options enum from C++20. The old enum values are mapped onto the new enum. The old enum will be removed in a future release. New: Added copy_options::skip_existing option, which allows copy_file operation to succeed without overwriting the target file, if it exists. New: Added copy_options::update_existing option, which allows copy_file operation to conditionally overwrite the target file, if it exists, if its last write time is older than that of the replacement file. New: copy_file now returns bool, which indicates whether the file was copied. New, breaking change: copy operation has been extended and reworked to implement behavior specified in C++20 [fs.op.copy]. This includes support for copy_options::recursive, copy_options::copy_symlinks, copy_options::skip_symlinks, copy_options::directories_only, copy_options::create_symlinks and copy_options::create_hard_links options. The operation performs additional checks based on the specified options. Applying copy to a directory with default copy_options will now also copy files residing in that directory (but not nested directories or files in those directories). New: Added create_directory overload taking two paths. The second path is a path to an existing directory, which is used as a source of permission attributes to use in the directory to create. Deprecated: copy_directory operation has been deprecated in favor of the new create_directory overload. Note that the two operations have reversed order of the path arguments. equivalent on POSIX systems now returns the actual error code from the OS if one of the paths does not resolve to a file. Previously the function would return an error code of 1. (#141) equivalent no longer considers file size and last modification time in order to test whether the two paths refer to the same file. These checks could result in a false negative if the file was modified during the equivalent call. New: Added absolute overloads taking error_code argument. Operations that have current_path() as the default value of their arguments and also have an error_code argument will use the current_path(error_code& ec) overload to obtain the current path, so that its failure is reported via the error_code argument instead of an exception. space now initializes the space_info structure members to -1 values on error, as required by C++20 ([fs.op.space]/1). space on Windows now accepts paths referring to arbitrary files, not only directories. This is similar to POSIX systems and corresponds to the operation description in C++20. (#73) New: Added implementation of temp_directory_path for Windows CE. (PR#25) New: Improved compatibility with WASI platform. (PR#144) New: Improved support for Embarcadero compilers. (PR#130) New: Added implementations of unique_path operation based on getrandom (Linux), arc4random_buf (OpenBSD/FreeBSD/CloudABI) and BCrypt (Windows) system APIs. Deprecated: Auto-linking against system libraries on Windows with MSVC-compatible compilers is deprecated and will be removed in a future release. This affects users linking against static library of Boost.Filesystem. Users are advised to update their project build systems to either use a shared library of Boost.Filesystem, or explicitly specify the dependencies of Boost.Filesystem in the linker command line. Users of shared library of Boost.Filesystem are not affected. Flyweight: Maintenance work. Format: Correct allocator usage (fixes C++20 compilation). (Glen Fernandes) Geometry: Improvements PR#720 Additional R-tree constructors (thanks to Caian Benedicto). Various improvements in buffer, set and relational operations. Solved issues #709 memcpy called for object with no trivial copy-assignment. #721 Compilation error in bgi::detail::rtree::visitors::insert. #727 MSVC warning: conditional expression is constant. Bugfixes PR#700 Missing cases for default strategies in distance algorithm. PR#738 Longitudes out of range in direct geodesic formulas. GIL: Added Added new constructor initializing any_image from r-value reference to any image (PR#486). Implemented mechanism to reverse kernel_2d (PR#489). Changed BREAKING: Replace Boost.Variant with Boost.Variant2 (PR#474) which completes removal on uses of Boost.MPL (missing from Boost 1.72.0 change added PR#274). Use perfect forwarding from apply_operation to visit (PR#491). Removed BREAKING: Removed dependency on Boost.Variant Fixed Fixed invalid conversion from RGB8 to CMYK32 due to overflow (PR#470). Fixed image constructor from other image (PR#477). Fixed error plane_view_t is not a class or namespace name (PR#481). Fixed interleaved_view factory using point<std::ptrdiff_t> for dimension (PR#487). Fixed documentation replacing uses MPL with MP11 in tutorial (PR#494). Fixed missing header in numeric/kernel.hpp to make it self-contained (PR#502). Acknowledgements Samuel Debionne, Pranam Lashkari, Mateusz Loskot, Debabrata Mandal Heap: Correct destruction of top node in skew_heap. (Glen Fernandes) Correct and simplify allocator use. (Glen Fernandes) Integer: Fixed compilation of gcd in C++20 mode with clang 10. Improved support for Embarcadero compilers. (PR#21) Iterator: boost/function_output_iterator.hpp header is now deprecated. Users should replace its inclusion with boost/iterator/function_output_iterator.hpp. (PR#51) Improved support for Embarcadero compilers. (PR#55) LexicalCast: Fixed warnings on missing override (thanks to EugeneZelenko #35, #34). Fixes for the the Embarcadero compilers (thanks to Edward Diener). Log: Bug fixes: The syslog sink backend now verifies the IP version of the local and target addresses set by user. The addresses must have the same IP version as was specified in the ip_version named parameter on the sink backend construction (by default, IPv4 is assumed). When an address is obtained as a result of host name resolution, only addresses with matching IP version are considered. (#119) New Features: Move constructors and assignment operators of various components were marked noexcept. Added a new range_manip stream manipulator that can be used for outputting elements of a range, optionally separated by a delimiter. Added a new tuple_manip stream manipulator that can be used for outputting elements of a tuple or any other heterogeneous sequence, optionally separated by a delimiter. Added a new optional_manip stream manipulator that can be used for outputting optionally present values. See changelog for more details. Mp11: Improved compilation performance of mp_with_index<N> for large N. Added tuple_transform (contributed by Hans Dembinski.) Multi-index Containers: Added node extraction and insertion following the analogous interface of associative containers as introduced in C++17. This feature has also been extended to non key-based indices, in contrast to C++ standard library sequence containers, which do not provide such functionality. Clarified documentation on read/write key extractors (issue #32). Maintenance work. Nowide: The library now requires a C++11-compliant compiler and stdlib LFS: Add support for files > 2 GB where the underlying system supports it Generic UTF conversion functions are now available in the boost::nowide::utf namespace Add support for stat with UTF-8 paths Outcome: Announcements: The v2.1 branch is expected to be retired end of 2020, with the v2.2 branch becoming the default. You can use the future v2.2 branch now using better_optimisation. This branch has a number of major breaking changes to Outcome v2.1, see the front page for details. Enhancements: BREAKING CHANGE void results and outcomes no longer default construct types during explicit construction. Previously if you explicitly constructed a result<T> from a non-errored result<void>, it default constructed T. This was found to cause unhelpful surprise, so it has been disabled. New macro OUTCOME_ENABLE_LEGACY_SUPPORT_FOR. The macro OUTCOME_ENABLE_LEGACY_SUPPORT_FOR can be used to enable aliasing of older naming and features to newer naming and features when using a newer version of Outcome. Concepts now have snake case style naming instead of camel case style. When Outcome was first implemented, it was thought that C++ 20 concepts were going to have camel case style. This was changed before the C++ 20 release, and Outcome's concepts have been renamed similarly. This won't break any code in Outcome v2.1, as compatibility aliases are provided. However code compiled against Outcome v2.2 will need to be upgraded, unless OUTCOME_ENABLE_LEGACY_SUPPORT_FOR is set to 210 or lower. Concepts now live in OUTCOME_V2_NAMESPACE::concepts namespace. Previously concepts lived in the convert namespace, now they live in their own namespace. New concepts basic_result<T> and basic_outcome<T> added. End users were finding an unhelpful gap in between is_basic_result<T> and value_or_error<T> where they wanted a concept that matched types which were basic_result, but not exactly one of those. Concepts filling that gap were added. Operation TRY works differently from Outcome v2.2 onwards. This is a severely code breaking change which change the syntax of how one uses OUTCOME_TRY(). A regular expression suitable for upgrading code can be found in the list of changes between Outcome v2.1 and v2.2. Bug fixes: #224 The clang Apple ships in Xcode 11.4 (currently the latest) has not been patched with the fixes to LLVM clang that fix noexcept(std::is_constructible<T, void>) failing to compile which I originally submitted years ago. So give up waiting on Apple to fix their clang, add a workaround to Outcome. Spare storage could not be used from within no-value policy classes. Due to an obvious brain fart when writing the code at the time, the spare storage APIs had the wrong prototype which prevented them working from within policy classes. Sorry. PolyCollection: Fixed internal ambiguity problem between boost::type_erasure::any and boost::any (issue #17). Maintenance work. Polygon: C++20 fixed for event_comparison_type, vertex_equality_predicate_type, and voronoi_predicates. (Glen Fernandes) SmartPtr: Added owner_equals to shared_ptr, weak_ptr, local_shared_ptr. Added owner_hash_value to shared_ptr, weak_ptr. Added owner_equal_to, owner_hash. Added std::hash specializations for shared_ptr, local_shared_ptr. Added boost::hash support to, and std::hash, std::equal_to specializations for, weak_ptr. Stacktrace: Fixed a build error when compiled with -fno-exceptions (thanks to Jeremiah Rodriguez #91). System: operator bool() now returns failed() instead of value() != 0. Type_Traits: Implemented conjunction, disjunction, negation, is_trivially_copyable, is_scoped_enum, and is_unscoped_enum. (Glen Fernandes) Variant: Fixed warnings on missing override (thanks to EugeneZelenko #78). Fixes for the the Embarcadero compilers (thanks to Edward Diener #79). Updated header locations to avoid warnings about using deprecated headers (thanks to Andrey Semashev #80) Variant2: Added support for derived types in visit. Improved compilation performance for many (hundreds of) alternatives. Added support for visit<R>. Wave: Implement C++20 features for variadics, including __VA_OPT__ (PR#75) Implement __has_include (PR#102) Introduce new sample: check_macro_naming, useful with Boost itself (PR#97) Fix compilation issue caused by std::allocator member removal in C++20 (PR#72) Repair Xpressive lexer and token_statistics sample (PR#79) Repair lexertl lexer (PR#78) Ensure hooks are run on predefined macros as well (PR#87) Various minor bug fixes C++98/03 support is now deprecated and will be removed in 1.77 YAP: Fixed compilation errors for placeholders; they now work in the general case, and in particular work with yap::print(). constexpr all the YAP. Fix printing of correct value category in yap::print(). Doc clarification. Updated Tools Boostbook: Change encoding of generated documentation from US-ASCII to UTF-8. (Glen Fernandes) Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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New Libraries STLInterfaces: A library of CRTP bases to ease the writing of STL views, iterators, and sequence containers, from Zach Laine. Updated Libraries ... [More] Asio: Added an implementation of the proposed standard executors (P0443r13, P1348r0, and P1393r0). Added support for the proposed standard executors to Asio's I/O facilities. The supplied executors now meet the requirements for the proposed standard executors. These classes also continue to meet the existing requirements for the Networking TS model of executors. All I/O objects, asynchronous operations, and utilities will interoperate with both new proposed standard executors, and with existing Networking TS executors. The any_io_executor type alias has been introduced as the default runtime-polymorphic executor for all I/O objects. This defaults to the execution::any_executor<> template. If required for backward compatibility, BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT can be defined to use the old asio::executor polymorphic wrapper instead. Support for the existing Networking TS model of executors can be disabled by defining BOOST_ASIO_NO_TS_EXECUTORS. Added converting move construction and assignment to basic_waitable_timer. Enabled C++20 coroutine support when using gcc 10. Added overloads of co_spawn that launch an awaitable. Added a new constructor overload to use_awaitable_t's default executor adapter, to enable conversion between executor types. Added support for using detached_t as a default completion token, by adding members as_default_on() and as_default_on_t<>. Added a move constructor to ssl::stream<>. Changed ssl::stream<> write operations to linearise gather-write buffer sequences. Added compile-time detection of the deprecated asio_handler_invoke, asio_handler_allocate, and asio_handler_deallocate hooks, when BOOST_ASIO_NO_DEPRECATED is defined. Implemented a number of performance optimisations. Added source location support to handler tracking. Implemented various improvements to the handlerviz.pl tool. Added the handlerlive.pl tool, which processes handler tracking output to produce a list of "live" handlers. Added the handlertree.pl tool, which filters handler tracking output to include only those events in the tree that produced the nominated handlers. Added changes for clang-based Embarcadero C++ compilers. Fixed a deadlock that can occur when multiple threads concurrently initialise the Windows I/O completion port backend. Fixed async_compose to work with copyable handlers when passed by lvalue. Fixed completion signature deduction in co_spawn. Removed a spurious Executor base class from the executor_binder implementation. Various fixes and improvements in the documentation and examples. Consult the Revision History for further details. Atomic: Added missing const qualifiers to some operations in atomic_ref. Added support for yield instruction on ARMv8-A. The instruction is used internally in spin loops to reduce CPU power consumption. Added support for C++20 waiting and notifying operations. The implementation includes generic backend that involves the internal lock pool, as well as specialized backends for Windows, Linux, FreeBSD, DragonFly BSD and NetBSD. Atomic types provide a new method has_native_wait_notify, a static boolean constant always_has_native_wait_notify and a set of capability macros that allow to detect if the implementation supports native waiting and notifying operations for a given type. Changed internal representation of atomic_flag to use 32-bit storage. This allows for more efficient waiting and notifying operations on atomic_flag on some platforms. Added support for build-time configuration of the internal lock pool size. The user can define the BOOST_ATOMIC_LOCK_POOL_SIZE_LOG2 macro to specify binary logarithm of the size of the lock pool. The default value is 8, meaning that the size of the lock pool is 256, up from 64 used in the previous release. Added support for a new set of atomic types dedicated for inter-process communication: ipc_atomic_flag, ipc_atomic and ipc_atomic_ref. Users are recommended to port their code using non-IPC types for inter-process communication to the new types. The new types provide the same set of operations as their non-IPC counterparts, with the following differences: Most operations have an added precondition that is_lock_free returns true for the given atomic object. The library will issue a compile time error if this precondition is known to be not satisfied at compile time. All provided operations are address-free, meaning that the atomic object (in case of ipc_atomic_ref - the referenced object) may be located in process-shared memory or mapped into the same process at multiple different addresses. The new has_native_wait_notify operation and always_has_native_wait_notify constant indicate support for native inter-process waiting and notifying operations. When that support is not present, the operations are implemented with a busy loop, which is less efficient, but still is address-free. A separate set of capability macros is also provided to indicate this support. Added new atomic_unsigned_lock_free and atomic_signed_lock_free types introduced in C++20. The types indicate the atomic object type for an unsigned or signed integer, respectively, that is lock-free and preferably has native support for waiting and notifying operations. Added new gcc assembler backends for ARMv8-A (for both AArch32 and AArch64). The new backends are used to implement operations not supported by compiler intrinsics (including 128-bit operations on AArch64) and can also be used when compiler intrinsics are not available. Both little and big endian targets are supported. AArch64 backend supports extensions defined in ARMv8.1 and ARMv8.3. Added support for big endian targets in the legacy ARM backend based on gcc assembler blocks (this backend is used on ARMv7 and older targets). Previously, the backend assumed little endian memory layout, which is significant for 64-bit operations. Improved performance of seq_cst stores and thread fences on x86 by using lock-prefixed instructions instead of mfence. This means that the operations no longer affect non-temporal stores, which was also not guaranteed before. Use specialized instructions and intrinsics to order non-temporal memory accesses. Fixed capability macros for 80-bit long double on x86 targets not indicating lock-free operations even if 128-bit atomic operations were available. Fixed compilation of gcc asm blocks on Alpha targets. In the gcc __sync* intrinsics backend, fixed that store and load operations of large objects (larger than a pointer size) could be non-atomic. The implementation currently assumes that small objects can be stored with a single instruction atomically on all modern architectures. Beast: This update brings bug fixes and support for the following changes changes in Boost.Asio: Beast supports BOOST_ASIO_NO_DEPRECATED. Define this to help identify areas of your Beast and Asio code which use deprecated Asio interfaces. Beast also supports BOOST_ASIO_NO_TS_EXECUTORS. Define this to identify uses of executors from the now potentially outdated Networking TS Asio will use the Standard Executors model by default. You can prevent this behaviour by defining BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT in which the Networking TS model will be used by default. Setting this flag does not prevent a program from using executors from the Standard Executors model explicitly. 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. Bimap: Correct allocator usage (fixes C++20 compilation). (Glen Fernandes) Config: Implement BOOST_NO_CXX11_OVERRIDE and BOOST_OVERRIDE. (Glen Fernandes) Core: Implemented the allocator access utilities which provide a replacement for allocator_traits with individual traits and functions for each facility. They support the C++11 allocator model when possible and provide a fallback for C++98 compatibility. These are now used in Circular_Buffer, Wave, Lockfree, Heap, Smart_Ptr, Dynamic_Bitset, Format, Bimap and more. (Glen Fernandes) DLL: Multiple fixes for the library_info work on empty shared objects. Compilation fixes for C++98 and C++11 modes (#28). Fixes for smart_library manglings (thanks to XiaLiChao82 #37). Endian: Enabled scoped enumeration types in endian_reverse. Enabled bool, enum, float, double in endian_reverse_inplace. Added an overload of endian_reverse_inplace for arrays. Filesystem: Removed compile-time checks for support for symlinks and hardlink on Windows. Instead, a runtime check is used. (PR#142) Fixed handling of reparse points in canonical and read_symlink on Windows. This also affects other algorithms that involve canonical and read_symlink in their implementation. (PR#100, #85, #99, #123, #125) Fixed that read_symlink on Windows could potentially fail or cause failures elsewhere with a sharing violation error, if the same symlink was opened concurrently. (#138) Fixed that is_symlink(directory_entry) would always return false, even if the directory entry actually referred to a symlink. (PR#148) Added missing status inspection operation overloads for directory_entry and error_code (e.g. is_directory(directory_entry, error_code&)). Removed incorrect noexcept specifications for the overloads not taking the error_code arguments. copy_file implementation has been updated to perform checks on the source and target files, as required by C++20 ([fs.op.copy.file]/4.1). In particular, the operation will fail if the source or target file is not a regular file or the source and target paths identify the same file. copy_file on POSIX systems will now also copy the source file permissions to the target file, if the target file is overwritten. New: Added copy_file implementations based on sendfile and copy_file_range system calls on Linux, which may improve file copying performance, especially on network filesystems. Deprecated: The copy_option enumeration that is used with the copy_file operation is deprecated. As a replacement, the new enum copy_options (note the trailing 's') has been added. The new enum contains values similar to the copy_options enum from C++20. The old enum values are mapped onto the new enum. The old enum will be removed in a future release. New: Added copy_options::skip_existing option, which allows copy_file operation to succeed without overwriting the target file, if it exists. New: Added copy_options::update_existing option, which allows copy_file operation to conditionally overwrite the target file, if it exists, if its last write time is older than that of the replacement file. New: copy_file now returns bool, which indicates whether the file was copied. New, breaking change: copy operation has been extended and reworked to implement behavior specified in C++20 [fs.op.copy]. This includes support for copy_options::recursive, copy_options::copy_symlinks, copy_options::skip_symlinks, copy_options::directories_only, copy_options::create_symlinks and copy_options::create_hard_links options. The operation performs additional checks based on the specified options. Applying copy to a directory with default copy_options will now also copy files residing in that directory (but not nested directories or files in those directories). New: Added create_directory overload taking two paths. The second path is a path to an existing directory, which is used as a source of permission attributes to use in the directory to create. Deprecated: copy_directory operation has been deprecated in favor of the new create_directory overload. Note that the two operations have reversed order of the path arguments. equivalent on POSIX systems now returns the actual error code from the OS if one of the paths does not resolve to a file. Previously the function would return an error code of 1. (#141) equivalent no longer considers file size and last modification time in order to test whether the two paths refer to the same file. These checks could result in a false negative if the file was modified during the equivalent call. New: Added absolute overloads taking error_code argument. Operations that have current_path() as the default value of their arguments and also have an error_code argument will use the current_path(error_code& ec) overload to obtain the current path, so that its failure is reported via the error_code argument instead of an exception. space now initializes the space_info structure members to -1 values on error, as required by C++20 ([fs.op.space]/1). space on Windows now accepts paths referring to arbitrary files, not only directories. This is similar to POSIX systems and corresponds to the operation description in C++20. (#73) New: Added implementation of temp_directory_path for Windows CE. (PR#25) New: Improved compatibility with WASI platform. (PR#144) New: Improved support for Embarcadero compilers. (PR#130) New: Added implementations of unique_path operation based on getrandom (Linux), arc4random_buf (OpenBSD/FreeBSD/CloudABI) and BCrypt (Windows) system APIs. Deprecated: Auto-linking against system libraries on Windows with MSVC-compatible compilers is deprecated and will be removed in a future release. This affects users linking against static library of Boost.Filesystem. Users are advised to update their project build systems to either use a shared library of Boost.Filesystem, or explicitly specify the dependencies of Boost.Filesystem in the linker command line. Users of shared library of Boost.Filesystem are not affected. Flyweight: Maintenance work. Format: Correct allocator usage (fixes C++20 compilation). (Glen Fernandes) Geometry: Improvements PR#720 Additional R-tree constructors (thanks to Caian Benedicto). Various improvements in buffer, set and relational operations. Solved issues #709 memcpy called for object with no trivial copy-assignment. #721 Compilation error in bgi::detail::rtree::visitors::insert. #727 MSVC warning: conditional expression is constant. Bugfixes PR#700 Missing cases for default strategies in distance algorithm. PR#738 Longitudes out of range in direct geodesic formulas. GIL: Added Added new constructor initializing any_image from r-value reference to any image (PR#486). Implemented mechanism to reverse kernel_2d (PR#489). Changed BREAKING: Replace Boost.Variant with Boost.Variant2 (PR#474) which completes removal on uses of Boost.MPL (missing from Boost 1.72.0 change added PR#274). Use perfect forwarding from apply_operation to visit (PR#491). Removed BREAKING: Removed dependency on Boost.Variant Fixed Fixed invalid conversion from RGB8 to CMYK32 due to overflow (PR#470). Fixed image constructor from other image (PR#477). Fixed error plane_view_t is not a class or namespace name (PR#481). Fixed interleaved_view factory using point<std::ptrdiff_t> for dimension (PR#487). Fixed documentation replacing uses MPL with MP11 in tutorial (PR#494). Fixed missing header in numeric/kernel.hpp to make it self-contained (PR#502). Acknowledgements Samuel Debionne, Pranam Lashkari, Mateusz Loskot, Debabrata Mandal Heap: Correct destruction of top node in skew_heap. (Glen Fernandes) Correct and simplify allocator use. (Glen Fernandes) Integer: Fixed compilation of gcd in C++20 mode with clang 10. Improved support for Embarcadero compilers. (PR#21) Iterator: boost/function_output_iterator.hpp header is now deprecated. Users should replace its inclusion with boost/iterator/function_output_iterator.hpp. (PR#51) Improved support for Embarcadero compilers. (PR#55) LexicalCast: Fixed warnings on missing override (thanks to EugeneZelenko #35, #34). Fixes for the the Embarcadero compilers (thanks to Edward Diener). Log: Bug fixes: The syslog sink backend now verifies the IP version of the local and target addresses set by user. The addresses must have the same IP version as was specified in the ip_version named parameter on the sink backend construction (by default, IPv4 is assumed). When an address is obtained as a result of host name resolution, only addresses with matching IP version are considered. (#119) New Features: Move constructors and assignment operators of various components were marked noexcept. Added a new range_manip stream manipulator that can be used for outputting elements of a range, optionally separated by a delimiter. Added a new tuple_manip stream manipulator that can be used for outputting elements of a tuple or any other heterogeneous sequence, optionally separated by a delimiter. Added a new optional_manip stream manipulator that can be used for outputting optionally present values. See changelog for more details. Mp11: Improved compilation performance of mp_with_index<N> for large N. Added tuple_transform (contributed by Hans Dembinski.) Multi-index Containers: Added node extraction and insertion following the analogous interface of associative containers as introduced in C++17. This feature has also been extended to non key-based indices, in contrast to C++ standard library sequence containers, which do not provide such functionality. Clarified documentation on read/write key extractors (issue #32). Maintenance work. Nowide: The library now requires a C++11-compliant compiler and stdlib LFS: Add support for files > 2 GB where the underlying system supports it Generic UTF conversion functions are now available in the boost::nowide::utf namespace Add support for stat with UTF-8 paths Outcome: Announcements: The v2.1 branch is expected to be retired end of 2020, with the v2.2 branch becoming the default. You can use the future v2.2 branch now using better_optimisation. This branch has a number of major breaking changes to Outcome v2.1, see the front page for details. Enhancements: BREAKING CHANGE void results and outcomes no longer default construct types during explicit construction. Previously if you explicitly constructed a result<T> from a non-errored result<void>, it default constructed T. This was found to cause unhelpful surprise, so it has been disabled. New macro OUTCOME_ENABLE_LEGACY_SUPPORT_FOR. The macro OUTCOME_ENABLE_LEGACY_SUPPORT_FOR can be used to enable aliasing of older naming and features to newer naming and features when using a newer version of Outcome. Concepts now have snake case style naming instead of camel case style. When Outcome was first implemented, it was thought that C++ 20 concepts were going to have camel case style. This was changed before the C++ 20 release, and Outcome's concepts have been renamed similarly. This won't break any code in Outcome v2.1, as compatibility aliases are provided. However code compiled against Outcome v2.2 will need to be upgraded, unless OUTCOME_ENABLE_LEGACY_SUPPORT_FOR is set to 210 or lower. Concepts now live in OUTCOME_V2_NAMESPACE::concepts namespace. Previously concepts lived in the convert namespace, now they live in their own namespace. New concepts basic_result<T> and basic_outcome<T> added. End users were finding an unhelpful gap in between is_basic_result<T> and value_or_error<T> where they wanted a concept that matched types which were basic_result, but not exactly one of those. Concepts filling that gap were added. Operation TRY works differently from Outcome v2.2 onwards. This is a severely code breaking change which change the syntax of how one uses OUTCOME_TRY(). A regular expression suitable for upgrading code can be found in the list of changes between Outcome v2.1 and v2.2. Bug fixes: #224 The clang Apple ships in Xcode 11.4 (currently the latest) has not been patched with the fixes to LLVM clang that fix noexcept(std::is_constructible<T, void>) failing to compile which I originally submitted years ago. So give up waiting on Apple to fix their clang, add a workaround to Outcome. Spare storage could not be used from within no-value policy classes. Due to an obvious brain fart when writing the code at the time, the spare storage APIs had the wrong prototype which prevented them working from within policy classes. Sorry. PolyCollection: Fixed internal ambiguity problem between boost::type_erasure::any and boost::any (issue #17). Maintenance work. SmartPtr: Added owner_equals to shared_ptr, weak_ptr, local_shared_ptr. Added owner_hash_value to shared_ptr, weak_ptr. Added owner_equal_to, owner_hash. Added std::hash specializations for shared_ptr, local_shared_ptr. Added boost::hash support to, and std::hash, std::equal_to specializations for, weak_ptr. Stacktrace: Fixed a build error when compiled with -fno-exceptions (thanks to Jeremiah Rodriguez #91). System: operator bool() now returns failed() instead of value() != 0. Type_Traits: Implemented conjunction, disjunction, negation, is_trivially_copyable, is_scoped_enum, and is_unscoped_enum. (Glen Fernandes) Variant: Fixed warnings on missing override (thanks to EugeneZelenko #78). Fixes for the the Embarcadero compilers (thanks to Edward Diener #79). Updated header locations to avoid warnings about using deprecated headers (thanks to Andrey Semashev #80) Variant2: Added support for derived types in visit. Improved compilation performance for many (hundreds of) alternatives. Added support for visit<R>. Wave: Implement C++20 features for variadics, including __VA_OPT__ (PR#75) Implement __has_include (PR#102) Introduce new sample: check_macro_naming, useful with Boost itself (PR#97) Fix compilation issue caused by std::allocator member removal in C++20 (PR#72) Repair Xpressive lexer and token_statistics sample (PR#79) Repair lexertl lexer (PR#78) Ensure hooks are run on predefined macros as well (PR#87) Various minor bug fixes C++98/03 support is now deprecated and will be removed in 1.77 YAP: Fixed compilation errors for placeholders; they now work in the general case, and in particular work with yap::print(). constexpr all the YAP. Fix printing of correct value category in yap::print(). Doc clarification. Updated Tools Boostbook: Change encoding of generated documentation from US-ASCII to UTF-8. (Glen Fernandes) Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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New Libraries STLInterfaces: A library of CRTP bases to ease the writing of STL views, iterators, and sequence containers, from Zach Laine. Updated Libraries ... [More] Asio: Added an implementation of the proposed standard executors (P0443r13, P1348r0, and P1393r0). Added support for the proposed standard executors to Asio's I/O facilities. The supplied executors now meet the requirements for the proposed standard executors. These classes also continue to meet the existing requirements for the Networking TS model of executors. All I/O objects, asynchronous operations, and utilities will interoperate with both new proposed standard executors, and with existing Networking TS executors. The any_io_executor type alias has been introduced as the default runtime-polymorphic executor for all I/O objects. This defaults to the execution::any_executor<> template. If required for backward compatibility, BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT can be defined to use the old asio::executor polymorphic wrapper instead. Support for the existing Networking TS model of executors can be disabled by defining BOOST_ASIO_NO_TS_EXECUTORS. Added converting move construction and assignment to basic_waitable_timer. Enabled C++20 coroutine support when using gcc 10. Added overloads of co_spawn that launch an awaitable. Added a new constructor overload to use_awaitable_t's default executor adapter, to enable conversion between executor types. Added support for using detached_t as a default completion token, by adding members as_default_on() and as_default_on_t<>. Added a move constructor to ssl::stream<>. Changed ssl::stream<> write operations to linearise gather-write buffer sequences. Added compile-time detection of the deprecated asio_handler_invoke, asio_handler_allocate, and asio_handler_deallocate hooks, when BOOST_ASIO_NO_DEPRECATED is defined. Implemented a number of performance optimisations. Added source location support to handler tracking. Implemented various improvements to the handlerviz.pl tool. Added the handlerlive.pl tool, which processes handler tracking output to produce a list of "live" handlers. Added the handlertree.pl tool, which filters handler tracking output to include only those events in the tree that produced the nominated handlers. Added changes for clang-based Embarcadero C++ compilers. Fixed a deadlock that can occur when multiple threads concurrently initialise the Windows I/O completion port backend. Fixed async_compose to work with copyable handlers when passed by lvalue. Fixed completion signature deduction in co_spawn. Removed a spurious Executor base class from the executor_binder implementation. Various fixes and improvements in the documentation and examples. Consult the Revision History for further details. Atomic: Added missing const qualifiers to some operations in atomic_ref. Added support for yield instruction on ARMv8-A. The instruction is used internally in spin loops to reduce CPU power consumption. Added support for C++20 waiting and notifying operations. The implementation includes generic backend that involves the internal lock pool, as well as specialized backends for Windows, Linux, FreeBSD, DragonFly BSD and NetBSD. Atomic types provide a new method has_native_wait_notify, a static boolean constant always_has_native_wait_notify and a set of capability macros that allow to detect if the implementation supports native waiting and notifying operations for a given type. Changed internal representation of atomic_flag to use 32-bit storage. This allows for more efficient waiting and notifying operations on atomic_flag on some platforms. Added support for build-time configuration of the internal lock pool size. The user can define the BOOST_ATOMIC_LOCK_POOL_SIZE_LOG2 macro to specify binary logarithm of the size of the lock pool. The default value is 8, meaning that the size of the lock pool is 256, up from 64 used in the previous release. Added support for a new set of atomic types dedicated for inter-process communication: ipc_atomic_flag, ipc_atomic and ipc_atomic_ref. Users are recommended to port their code using non-IPC types for inter-process communication to the new types. The new types provide the same set of operations as their non-IPC counterparts, with the following differences: Most operations have an added precondition that is_lock_free returns true for the given atomic object. The library will issue a compile time error if this precondition is known to be not satisfied at compile time. All provided operations are address-free, meaning that the atomic object (in case of ipc_atomic_ref - the referenced object) may be located in process-shared memory or mapped into the same process at multiple different addresses. The new has_native_wait_notify operation and always_has_native_wait_notify constant indicate support for native inter-process waiting and notifying operations. When that support is not present, the operations are implemented with a busy loop, which is less efficient, but still is address-free. A separate set of capability macros is also provided to indicate this support. Added new atomic_unsigned_lock_free and atomic_signed_lock_free types introduced in C++20. The types indicate the atomic object type for an unsigned or signed integer, respectively, that is lock-free and preferably has native support for waiting and notifying operations. Added new gcc assembler backends for ARMv8-A (for both AArch32 and AArch64). The new backends are used to implement operations not supported by compiler intrinsics (including 128-bit operations on AArch64) and can also be used when compiler intrinsics are not available. Both little and big endian targets are supported. AArch64 backend supports extensions defined in ARMv8.1 and ARMv8.3. Added support for big endian targets in the legacy ARM backend based on gcc assembler blocks (this backend is used on ARMv7 and older targets). Previously, the backend assumed little endian memory layout, which is significant for 64-bit operations. Improved performance of seq_cst stores and thread fences on x86 by using lock-prefixed instructions instead of mfence. This means that the operations no longer affect non-temporal stores, which was also not guaranteed before. Use specialized instructions and intrinsics to order non-temporal memory accesses. Fixed capability macros for 80-bit long double on x86 targets not indicating lock-free operations even if 128-bit atomic operations were available. Fixed compilation of gcc asm blocks on Alpha targets. In the gcc __sync* intrinsics backend, fixed that store and load operations of large objects (larger than a pointer size) could be non-atomic. The implementation currently assumes that small objects can be stored with a single instruction atomically on all modern architectures. Beast: This update brings bug fixes and support for the following changes changes in Boost.Asio: Beast supports BOOST_ASIO_NO_DEPRECATED. Define this to help identify areas of your Beast and Asio code which use deprecated Asio interfaces. Beast also supports BOOST_ASIO_NO_TS_EXECUTORS. Define this to identify uses of executors from the now potentially outdated Networking TS Asio will use the Standard Executors model by default. You can prevent this behaviour by defining BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT in which the Networking TS model will be used by default. Setting this flag does not prevent a program from using executors from the Standard Executors model explicitly. 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. Bimap: Correct allocator usage (fixes C++20 compilation). (Glen Fernandes) Config: Implement BOOST_NO_CXX11_OVERRIDE and BOOST_OVERRIDE. (Glen Fernandes) Core: Implemented the allocator access utilities which provide a replacement for allocator_traits with individual traits and functions for each facility. They support the C++11 allocator model when possible and provide a fallback for C++98 compatibility. These are now used in Circular_Buffer, Wave, Lockfree, Heap, Smart_Ptr, Dynamic_Bitset, Format, Bimap and more. (Glen Fernandes) DLL: Multiple fixes for the library_info work on empty shared objects. Compilation fixes for C++98 and C++11 modes (#28). Fixes for smart_library manglings (thanks to XiaLiChao82 #37). Endian: Enabled scoped enumeration types in endian_reverse. Enabled bool, enum, float, double in endian_reverse_inplace. Added an overload of endian_reverse_inplace for arrays. Filesystem: Removed compile-time checks for support for symlinks and hardlink on Windows. Instead, a runtime check is used. (PR#142) Fixed handling of reparse points in canonical and read_symlink on Windows. This also affects other algorithms that involve canonical and read_symlink in their implementation. (PR#100, #85, #99, #123, #125) Fixed that read_symlink on Windows could potentially fail or cause failures elsewhere with a sharing violation error, if the same symlink was opened concurrently. (#138) Fixed that is_symlink(directory_entry) would always return false, even if the directory entry actually referred to a symlink. (PR#148) Added missing status inspection operation overloads for directory_entry and error_code (e.g. is_directory(directory_entry, error_code&)). Removed incorrect noexcept specifications for the overloads not taking the error_code arguments. copy_file implementation has been updated to perform checks on the source and target files, as required by C++20 ([fs.op.copy.file]/4.1). In particular, the operation will fail if the source or target file is not a regular file or the source and target paths identify the same file. copy_file on POSIX systems will now also copy the source file permissions to the target file, if the target file is overwritten. New: Added copy_file implementations based on sendfile and copy_file_range system calls on Linux, which may improve file copying performance, especially on network filesystems. Deprecated: The copy_option enumeration that is used with the copy_file operation is deprecated. As a replacement, the new enum copy_options (note the trailing 's') has been added. The new enum contains values similar to the copy_options enum from C++20. The old enum values are mapped onto the new enum. The old enum will be removed in a future release. New: Added copy_options::skip_existing option, which allows copy_file operation to succeed without overwriting the target file, if it exists. New: Added copy_options::update_existing option, which allows copy_file operation to conditionally overwrite the target file, if it exists, if its last write time is older than that of the replacement file. New: copy_file now returns bool, which indicates whether the file was copied. New, breaking change: copy operation has been extended and reworked to implement behavior specified in C++20 [fs.op.copy]. This includes support for copy_options::recursive, copy_options::copy_symlinks, copy_options::skip_symlinks, copy_options::directories_only, copy_options::create_symlinks and copy_options::create_hard_links options. The operation performs additional checks based on the specified options. Applying copy to a directory with default copy_options will now also copy files residing in that directory (but not nested directories or files in those directories). New: Added create_directory overload taking two paths. The second path is a path to an existing directory, which is used as a source of permission attributes to use in the directory to create. Deprecated: copy_directory operation has been deprecated in favor of the new create_directory overload. Note that the two operations have reversed order of the path arguments. equivalent on POSIX systems now returns the actual error code from the OS if one of the paths does not resolve to a file. Previously the function would return an error code of 1. (#141) equivalent no longer considers file size and last modification time in order to test whether the two paths refer to the same file. These checks could result in a false negative if the file was modified during the equivalent call. New: Added absolute overloads taking error_code argument. Operations that have current_path() as the default value of their arguments and also have an error_code argument will use the current_path(error_code& ec) overload to obtain the current path, so that its failure is reported via the error_code argument instead of an exception. space now initializes the space_info structure members to -1 values on error, as required by C++20 ([fs.op.space]/1). space on Windows now accepts paths referring to arbitrary files, not only directories. This is similar to POSIX systems and corresponds to the operation description in C++20. (#73) New: Added implementation of temp_directory_path for Windows CE. (PR#25) New: Improved compatibility with WASI platform. (PR#144) New: Improved support for Embarcadero compilers. (PR#130) New: Added implementations of unique_path operation based on getrandom (Linux), arc4random_buf (OpenBSD/FreeBSD/CloudABI) and BCrypt (Windows) system APIs. Deprecated: Auto-linking against system libraries on Windows with MSVC-compatible compilers is deprecated and will be removed in a future release. This affects users linking against static library of Boost.Filesystem. Users are advised to update their project build systems to either use a shared library of Boost.Filesystem, or explicitly specify the dependencies of Boost.Filesystem in the linker command line. Users of shared library of Boost.Filesystem are not affected. Flyweight: Maintenance work. Format: Correct allocator usage (fixes C++20 compilation). (Glen Fernandes) Geometry: Improvements PR#720 Additional R-tree constructors (thanks to Caian Benedicto). Various improvements in buffer, set and relational operations. Solved issues #709 memcpy called for object with no trivial copy-assignment. #721 Compilation error in bgi::detail::rtree::visitors::insert. #727 MSVC warning: conditional expression is constant. Bugfixes PR#700 Missing cases for default strategies in distance algorithm. PR#738 Longitudes out of range in direct geodesic formulas. GIL: Added Added new constructor initializing any_image from r-value reference to any image (PR#486). Implemented mechanism to reverse kernel_2d (PR#489). Changed BREAKING: Replace Boost.Variant with Boost.Variant2 (PR#474) which completes removal on uses of Boost.MPL (missing from Boost 1.72.0 change added PR#274). Use perfect forwarding from apply_operation to visit (PR#491). Removed BREAKING: Removed dependency on Boost.Variant Fixed Fixed invalid conversion from RGB8 to CMYK32 due to overflow (PR#470). Fixed image constructor from other image (PR#477). Fixed error plane_view_t is not a class or namespace name (PR#481). Fixed interleaved_view factory using point<std::ptrdiff_t> for dimension (PR#487). Fixed documentation replacing uses MPL with MP11 in tutorial (PR#494). Fixed missing header in numeric/kernel.hpp to make it self-contained (PR#502). Acknowledgements Samuel Debionne, Pranam Lashkari, Mateusz Loskot, Debabrata Mandal Heap: Correct destruction of top node in skew_heap. (Glen Fernandes) Correct and simplify allocator use. (Glen Fernandes) Integer: Fixed compilation of gcd in C++20 mode with clang 10. Improved support for Embarcadero compilers. (PR#21) Iterator: boost/function_output_iterator.hpp header is now deprecated. Users should replace its inclusion with boost/iterator/function_output_iterator.hpp. (PR#51) Improved support for Embarcadero compilers. (PR#55) LexicalCast: Fixed warnings on missing override (thanks to EugeneZelenko #35, #34). Fixes for the the Embarcadero compilers (thanks to Edward Diener). Log: Bug fixes: The syslog sink backend now verifies the IP version of the local and target addresses set by user. The addresses must have the same IP version as was specified in the ip_version named parameter on the sink backend construction (by default, IPv4 is assumed). When an address is obtained as a result of host name resolution, only addresses with matching IP version are considered. (#119) New Features: Move constructors and assignment operators of various components were marked noexcept. Added a new range_manip stream manipulator that can be used for outputting elements of a range, optionally separated by a delimiter. Added a new tuple_manip stream manipulator that can be used for outputting elements of a tuple or any other heterogeneous sequence, optionally separated by a delimiter. Added a new optional_manip stream manipulator that can be used for outputting optionally present values. See changelog for more details. Mp11: Improved compilation performance of mp_with_index<N> for large N. Added tuple_transform (contributed by Hans Dembinski.) Multi-index Containers: Added node extraction and insertion following the analogous interface of associative containers as introduced in C++17. This feature has also been extended to non key-based indices, in contrast to C++ standard library sequence containers, which do not provide such functionality. Clarified documentation on read/write key extractors (issue #32). Maintenance work. Nowide: The library now requires a C++11-compliant compiler and stdlib LFS: Add support for files > 2 GB where the underlying system supports it Generic UTF conversion functions are now available in the boost::nowide::utf namespace Add support for stat with UTF-8 paths Outcome: Announcements: The v2.1 branch is expected to be retired end of 2020, with the v2.2 branch becoming the default. You can use the future v2.2 branch now using better_optimisation. This branch has a number of major breaking changes to Outcome v2.1, see the front page for details. Enhancements: BREAKING CHANGE void results and outcomes no longer default construct types during explicit construction. Previously if you explicitly constructed a result<T> from a non-errored result<void>, it default constructed T. This was found to cause unhelpful surprise, so it has been disabled. New macro OUTCOME_ENABLE_LEGACY_SUPPORT_FOR. The macro OUTCOME_ENABLE_LEGACY_SUPPORT_FOR can be used to enable aliasing of older naming and features to newer naming and features when using a newer version of Outcome. Concepts now have snake case style naming instead of camel case style. When Outcome was first implemented, it was thought that C++ 20 concepts were going to have camel case style. This was changed before the C++ 20 release, and Outcome's concepts have been renamed similarly. This won't break any code in Outcome v2.1, as compatibility aliases are provided. However code compiled against Outcome v2.2 will need to be upgraded, unless OUTCOME_ENABLE_LEGACY_SUPPORT_FOR is set to 210 or lower. Concepts now live in OUTCOME_V2_NAMESPACE::concepts namespace. Previously concepts lived in the convert namespace, now they live in their own namespace. New concepts basic_result<T> and basic_outcome<T> added. End users were finding an unhelpful gap in between is_basic_result<T> and value_or_error<T> where they wanted a concept that matched types which were basic_result, but not exactly one of those. Concepts filling that gap were added. Operation TRY works differently from Outcome v2.2 onwards. This is a severely code breaking change which change the syntax of how one uses OUTCOME_TRY(). A regular expression suitable for upgrading code can be found in the list of changes between Outcome v2.1 and v2.2. Bug fixes: #224 The clang Apple ships in Xcode 11.4 (currently the latest) has not been patched with the fixes to LLVM clang that fix noexcept(std::is_constructible<T, void>) failing to compile which I originally submitted years ago. So give up waiting on Apple to fix their clang, add a workaround to Outcome. Spare storage could not be used from within no-value policy classes. Due to an obvious brain fart when writing the code at the time, the spare storage APIs had the wrong prototype which prevented them working from within policy classes. Sorry. PolyCollection: Fixed internal ambiguity problem between boost::type_erasure::any and boost::any (issue #17). Maintenance work. SmartPtr: Added owner_equals to shared_ptr, weak_ptr, local_shared_ptr. Added owner_hash_value to shared_ptr, weak_ptr. Added owner_equal_to, owner_hash. Added std::hash specializations for shared_ptr, local_shared_ptr. Added boost::hash support to, and std::hash, std::equal_to specializations for, weak_ptr. Stacktrace: Fixed a build error when compiled with -fno-exceptions (thanks to Jeremiah Rodriguez #91). System: operator bool() now returns failed() instead of value() != 0. Type_Traits: Implemented conjunction, disjunction, negation, is_trivially_copyable, is_scoped_enum, and is_unscoped_enum. (Glen Fernandes) Variant: Fixed warnings on missing override (thanks to EugeneZelenko #78). Fixes for the the Embarcadero compilers (thanks to Edward Diener #79). Updated header locations to avoid warnings about using deprecated headers (thanks to Andrey Semashev #80) Variant2: Added support for derived types in visit. Improved compilation performance for many (hundreds of) alternatives. Added support for visit<R>. Wave: Implement C++20 features for variadics, including __VA_OPT__ (PR#75) Implement __has_include (PR#102) Introduce new sample: check_macro_naming, useful with Boost itself (PR#97) Fix compilation issue caused by std::allocator member removal in C++20 (PR#72) Repair Xpressive lexer and token_statistics sample (PR#79) Repair lexertl lexer (PR#78) Ensure hooks are run on predefined macros as well (PR#87) Various minor bug fixes C++98/03 support is now deprecated and will be removed in 1.77 YAP: Fixed compilation errors for placeholders; they now work in the general case, and in particular work with yap::print(). constexpr all the YAP. Fix printing of correct value category in yap::print(). Doc clarification. Updated Tools Boostbook: Change encoding of generated documentation from US-ASCII to UTF-8. (Glen Fernandes) Compilers Tested Boost's primary test compilers are: Linux: Clang: 3.0, 4.0.1, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 5.4.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Boost's additional test compilers include: Linux: Clang: 3.0, 3.8.1, 3.9.1, 4.0.1, 5.0.2, 6.0.1 Clang, C++0x: 3.0 Clang, C++11: 3.0, 3.1, 3.2, 3.3, 3.4, 4.0.1, 6.0.1, 7.0.0, 8.0.0 Clang, C++14: 3.5.0, 3.6.0, 3.7.1, 3.8.0, 3.9.1, 4.0.0, 4.0.1, 5.0.2, 6.0.1, 7.0.0, 8.0.0 Clang, C++17: 5.0.2, 6.0.1, 7.0.0, 8.0.0 GCC: 4.4.7, 4.5.3, 4.6.3, 4.9.4, 5.4.0, 5.5.0, 8.0.1 GCC, C++0x: 4.4.7 GCC, C++11: 4.7.3, 4.8.5, 4.9.4, 5.4.0, 6.4.0, 7.1.0, 8.0.1 GCC, C++14: 5.4.0, 5.5.0, 6.3.0, 6.4.0, 7.1.0, 7.3.0, 8.0.1, 8.1.0 GCC, C++17: 7.3.0, 8.0.1 Intel, C++14: 18.0 OS X: Apple Clang: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++11: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++14: 9.0.0, 9.1.0, 10.0.0 Apple Clang, C++17: 9.1.0, 10.0.0 Apple Clang, C++1z: 9.0.0 Apple Clang, C++2a: 10.0.0 Windows: GCC: 3.4.5, 4.1.2, 4.2.4, 4.3.3, 4.4.0, 4.5.4 GCC, C++0x: 4.6.4 GCC, C++11: 4.7.3, 4.8.1, 4.9.3 GCC, C++14: 5.1.0, 5.2.0, 5.3.0, 6.1.0, 6.2.0, 6.3.0, 6.4.0 GCC, C++17: 7.1.0, 7.2.0, 7.3.0 Visual C++: 7.1, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 14.1 FreeBSD: Clang: 4.0.0 Clang, C++11: 4.0.0 Clang, C++14: 4.0.0 Clang, C++1z: 4.0.0 Acknowledgements Marshall Clow, Michael Caisse and Glen Fernandes managed this release. 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