Notice of Dropping C++03 Support

The following libraries will be dropping C++03 support in release 1.84, two releases from now:

• Align
• Any
• Bind
• Chrono
• ContainerHash
• Conversion
• DLL
• Endian
• Function
• Functional
• Io
• LexicalCast
• Random
• Ratio
• SmartPtr
• System
• Stacktrace
• Thread
• Timer
• TypeIndex
• Typeof
• Unordered
• Variant

This release (1.82) and the next (1.83) will be the last releases offering C++03 support for the above libraries and most of their dependencies.

The new baseline requirement for the above libraries, and for most of Boost, will be C++11. Since old compiler versions often implement C++11 only partially, due to missing support or bugs, what compilers are considered to meet the C++11 requirement may vary by library.

However, a general rule is that if a compiler does not recognize a C++11 keyword or syntax at all (e.g. use of noexcept, use of constexpr, or defining a =deleted function results in an immediate compile error), or if a compiler does not provide a required C++11 header at all (e.g. trying to include <atomic> or <chrono> fails), or the compiler provides a C++11 feature or a header that is completely unusable, this compiler is not considered a C++11 compiler.

This rules out, for instance, Microsoft Visual C++ before 14.0, or GCC before 4.8.

New Libraries

• Mysql: a C++11 client for the MySQL database server, based on Boost.Asio, from Reuben Perez.

Updated Libraries

• Any:

  • Now uses core/enable_if instead of the deprecated utility/enable_if. Thanks to Michael Ford for the PR PR#25.
• ContainerHash:

  • Added an overload of hash_value for std::nullptr_t.
  • Added is_tuple_like and an overload of hash_value for tuple-like types.
  • Changed string hashing to use mulxp1_hash. This improves both quality and speed.
• DLL:

  • Avoid implicit cast from size_t to uint32_t, thanks to Travers Biddle for the PR PR#57.
• Math:

  • Deprecated C++11 support: We now require C++14 as a minimum standard. Our minimum tested compiler versions are now Clang-5, GCC-5 or MSVC-14.1.
  • Added Estrin's method for polynomial evaluation.
  • Fix various issues in non-central distributions to allow for larger non-centralities see 939.
  • Added CMake install target.
  • Fix special_functions.hpp to disable anything which can't be used in an exception-free environment.
  • Get condition number calculation working in C++14.
  • Fix constexpr table driven functions to avoid massive slowdown when the code is not actually constexpr, see 923.
  • Improve tanh_sinh boundary handling, see 894.
  • Add Linux arm64, s390x and Apple M1 testing, fix up test cases to handle 128-bit long doubles.
  • Improve constexpr math functions to better handle infinities and NaN's.
  • Make the integrators const-correct.
  • Fix tanh_sinh integrator in case the function underflows, see 898.
  • Don't use std::cbrt as some platforms still don't support it.
  • Stop non-central T from raising spurious FE_INVALID exceptions, see 892.
  • Fix binomial distribution edge case.
  • Improve ibeta handling of very small arguments, see 884.
  • Improve ibeta handling of infinities and NaN's, see 878.
  • Improve error handling in powm1, see 781.
  • Improve root-finder bracketing to bracket faster when the exponent is super-large or small.
  • Fix root finding edge cases, see 873.
  • Lots of miscellaneous warning fixes.
  • Add assertions when using features which require C++17 for better error messages when invoking the compiler in a lower std version.
• Multi-index Containers:

  • Serialization now uses unsigned long instead of collection_size_type, and multi_index_container serialization class version has been bumped from 2 to 3 to reflect this change. Reading old archives may fail for custom archive types giving special treatment to collection_size_type values: if this is the case, globally define the macro BOOST_MULTI_INDEX_ENABLE_SERIALIZATION_COMPATIBILITY_V2 to ensure backwards compatibility in reading operations.
  • Maintenance work.
• Multiprecision:

  • Deprecated C++11 support: We now require C++14 as a minimum standard. Our minimum tested compiler versions are now Clang-5, GCC-5 or MSVC-14.1.
  • Added a new forward declaration header.
  • Update Eigen interoperability so we no longer rely on Eigen's details, see 479.
  • Add Cmake install target.
  • Fix cpp_dec_float construction from string in standalone case for better error handling, see 499.
  • Remove redundent definitions when in C++17 mode, see 530.
  • Fix the error handling in standalone itrunc and ltrunc.
  • Fix potentially uninitialized storage when parsing octal strings.
  • Add arm64 and s390x CI testing.
  • Add some missing expression template unpacking code for powm, see 506.
• PFR:

  • Implemented the boost::pfr::is_implicitly_reflectable and the machinery for specializing aggregates as reflectable or not, thanks to Denis Mikhailov for the PR PR#111.
  • Implemented the BOOST_PFR_ENABLED to macro to detect library support, thanks to Denis Mikhailov for the PR PR#86.
  • Fixed missing terminating character, thanks to Denis Mikhailov for the PR PR#114.
  • Fixed for the boost/pfr/config.hpp on older compilers, thanks to Denis Mikhailov for the PR PR#118.
  • Workaround for broken C++17 stuctured binding in old compilers, thanks to Denis Mikhailov for the PR PR#119.
  • Avoid -Wzero-as-null-pointer-constant warnings, thanks to Markus F.X.J. Oberhumer for the PR PR#117.
  • Fixed multiple typos, thanks to Denis Mikhailov for the fixes.
  • Added missing #pragma once, thanks to caozhanhao for the PR PR#121.
  • Implemented boost::pfr::get by type of an element in the aggregate.
  • Multiple fixes and improvements for the docs.
• StaticString:

  • Boost.Core string_view and std::string_view interoperability
• Test:

  • Fixed several unused variable warnings
  • Fixed sprintf deprecation warnings
  • Fixed undefined behavior in basic_cstring::rfind
  • Added CI through Github Actions
• Unordered:

  • Major update.
  • Added node-based, open-addressing containers boost::unordered_node_map and boost::unordered_node_set.
  • Extended heterogeneous lookup to more member functions as specified in P2363.
  • Replaced the previous post-mixing process for open-addressing containers with a new algorithm based on extended multiplication by a constant.
  • Fixed bug in internal emplace impl where stack-local types were not properly constructed using the allocator of the container which breaks uses-allocator construction.
• URL:

  • Add url::format with automatic percent-encoding
  • URL router example
  • set_params convenience function
  • Support implicit conversions to string_view
  • Parsing constructors are implicit
  • string_token::arg has virtual destructor and slice protection
  • Support BOOST_URL_DISABLE_THREADS
  • Improvements and Bug fixes:

    • WIN32_LEAN_AND_MEAN macro redefinition warning
    • Comparison differentiates absent and empty components
    • Detect hier_part_rule with empty-port-like segments
    • Segments comparison as if normalized works above root
    • hier-part path-rootless considers invalid segments
    • port as number is set to 0 when it overflows
    • ipv4 to string overflow detection algorithm
• Variant:

  • Now uses core/enable_if instead of the deprecated utility/enable_if. Thanks to Michael Ford for the PR PR#105.

Updated Tools

• Build:

  • Includes release of B2 version 4.9.4.

Compilers Tested

Boost's primary test compilers are:

• Linux:

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

  • Apple Clang, C++03: 11.0.3
  • Apple Clang, C++11: 11.0.3
  • Apple Clang, C++14: 11.0.3
  • Apple Clang, C++17: 11.0.3
  • Apple Clang, C++20: 11.0.3
• Windows:

  • Visual C++: 10.0, 11.0, 12.0, 14.0, 14.1, 14.2, 14.3

Acknowledgements

Marshall Clow and Glen Fernandes managed this release.