v17.14: VS 2022 17.14

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• Merged C++26 features:
  • P3323R1 #​5213 Forbid atomic<cv T>, Specify atomic_ref<cv T>
• Merged partial C++26 features:
  • P3471R4 #​5274 Standard Library Hardening
    • Currently disabled by default.
    • This can be enabled (for any Standard mode) by defining _MSVC_STL_HARDENING to 1 project-wide.
    • As C++26 Contracts are not yet implemented, this defaults to calling __fastfail() for hardened precondition violations.
• Related behavior enhancement:
  • Implemented "destructor tombstones" to mitigate use-after-free mistakes. #​5318
    • Currently disabled by default.
    • This can be enabled by defining _MSVC_STL_DESTRUCTOR_TOMBSTONES to 1 project-wide.
• Merged LWG issue resolutions:
  • LWG-3133 #​5157 Modernizing numeric type requirements
  • LWG-3886 #​5232 Monad mo' problems (in optional and expected)
  • LWG-3899 #​5303 co_yielding elements of an lvalue generator is unnecessarily inefficient
  • LWG-3900 #​5150 The allocator_arg_t overloads of generator::promise_type::operator new should not be constrained
  • LWG-3918 #​5135 #​5170 std::uninitialized_move/_n and guaranteed copy elision
  • LWG-3956 #​5334 chrono::parse uses from_stream as a customization point
  • LWG-4014 #​5132 LWG-3809 changes behavior of some existing std::subtract_with_carry_engine code
  • LWG-4027 #​5221 possibly-const-range should prefer returning const R&
  • LWG-4084 #​5151 std::fixed ignores std::uppercase
  • LWG-4112 #​5152 has-arrow should require operator->() to be const-qualified
  • LWG-4119 #​5220 generator::promise_type::yield_value(ranges::elements_of<R, Alloc>)'s nested generator may be ill-formed
  • LWG-4124 #​5155 Cannot format zoned_time with resolution coarser than seconds
  • LWG-4135 #​5131 The helper lambda of std::erase for list should specify return type as bool
  • LWG-4140 #​5129 Useless default constructors for bit reference types
  • LWG-4144 #​5201 Disallow unique_ptr<T&, D>
  • LWG-4169 #​5128 std::atomic<T>'s default constructor should be constrained
  • LWG-4172 #​5337 unique_lock self-move-assignment is broken
• Merged proposed resolutions for LWG issues (not yet accepted for the C++ Working Draft, but we've chosen to implement this speculatively):
  • LWG-3424 #​5232 optional::value_or should never return a cv-qualified type
• Fixed bugs:
  • Fixed system_category().message() to prefer US English, followed by the system locale, with an ultimate fallback of FormatMessageA's behavior for dwLanguageId == 0. #​5104
    • This is consistent with generic_category().message() (which always returns US English in our implementation) and has the best chance of returning something intelligible instead of "unknown error" or "???".
    • This fixed a regression that was introduced by #​2669 in VS 2022 17.3.
  • Fixed regex's behavior:
    • To reject bogus character class ranges like R"([\d-e])". #​5158
    • For negated character class escapes (\D for non-digits, \S for non-whitespace, \W for non-words) when matching against Unicode characters:
      • Outside square-bracket character classes. #​5160
      • Inside square-bracket character classes (partially fixed). #​5214
    • For character ranges in case-insensitive mode. #​5164
    • For the basic grammar to parse a single digit for backreferences. #​5167
    • For its internal buffers to grow geometrically. #​5175
    • For the special character . (dot). #​5192
    • For its constructor to accept (null, zero) arguments. #​5211
  • Fixed filesystem::equivalent() to return correct results when shared folders are involved. #​5130
  • Fixed chrono::weekday's constructor to avoid integer overflow for extreme inputs. #​5156
  • Fixed push_range() for stack, queue, and priority_queue to forward the range to c.append_range() when possible, exactly as depicted in the Standard. #​5168
  • Fixed code to call ranges::begin and ranges::end exactly as depicted in the Standard:
    • ranges::to. #​5173
    • range_formatter. #​5178
  • Fixed compiler errors in range_formatter involving highly unusual contiguous ranges. #​5187
  • Fixed heterogeneous lookup for unordered containers to follow the Standard, allowing braced initializer lists to be used as arguments. #​5208
  • Fixed compiler errors in views::counted involving highly unusual types. #​5223
  • Fixed integer overflow in this_thread::sleep_for() with extremely small units (e.g. picoseconds). #​5237
  • Fixed basic_string::reserve()'s ASan annotations to detect writes to its unused capacity. #​5252
  • Fixed how <format> handles field width for alternate form general floating-point. #​5261
  • Fixed compiler errors when constructing a basic_ispanstream from a modifiable basic_string. #​5309
    • This fixed a regression that was introduced by #​4938 in VS 2022 17.13.
  • Fixed compiler errors when using <format> in a CUDA project, by adding a compiler bug workaround. #​5335
  • Fixed compiler errors when converting between different specializations of basic_const_iterator. #​5325
• Improved performance:
  • Added vectorized implementations of:
    • basic_string::find() for a character. #​5101
  • Improved the vectorized implementations of:
    • basic_string::find_first_of() and basic_string::find_last_of(). #​5029
  • regex_traits::translate() is now an identity function, as required by the Standard, instead of an expensive locale operation. #​5209
  • The STL now takes advantage of compiler support for C++23 P1169R4 static operator() in earlier Standard modes, slightly improving codegen. #​5284 #​5312
  • Optimized the minstd_rand and minstd_rand0 random number engines by avoiding constant divisions. #​5256
  • Slightly improved move_only_function's constructors to do less work when setting the object to be empty. #​5328
• Enhanced behavior:
  • std::expected, std::unexpected, and all STL exception types are now marked [[nodiscard]]. #​5174
    • This affects all user-defined functions returning these types by value. It also affects any directly constructed temporaries that are immediately discarded.
  • Deprecated the non-Standard locale::empty() static member function. #​5197
  • Changed the STL to avoid using is_trivial, which is being deprecated in C++26. #​5202
  • Improved the STL's debug checks with better messages and fewer branches. #​5270
• Improved debugger visualization:
  • Improved the visualizers for basic_string_view and its iterators by suppressing irrelevant pointer values. #​5176
  • Dramatically simplified how the visualizers for basic_string and its iterators are implemented. #​5177
• Improved test coverage:
  • Simplified the test harness by dropping ctest. Now we always directly invoke stl-lit.py. #​5169
  • Improved the test harness to warn only once when a compiler is missing. #​5199
  • Categorized libcxx test failures. #​5231
  • Updated our LLVM submodule, including new tests. #​5235
  • Added test coverage for the ASan annotations in basic_string::reserve() and vector::reserve(). #​5241
  • Skipped libcxx tests in response to a new compiler warning C5321, which warns when the resolution to CWG-1656 affects a u8 string literal. #​5283
• Code cleanups:
  • Removed compiler bug workarounds. #​5186 #​5247 #​5257 #​5284 #​5335
  • Removed usage of [[likely]] and [[unlikely]], which are discouraged by the compiler team. #​5255
  • Various cleanups (described in detail in the PRs, not repeated here). #​5336
• Infrastructure improvements:
  • Updated dependencies. #​5186 #​5247 #​5257 #​5284 #​5335
    • Updated build compiler to VS 2022 17.14 Preview 2 (now required).
    • Updated Clang to 19.1.5 (now required).
    • Updated Google Benchmark to 1.9.1.
    • Updated Python to 3.13.2.
    • Updated VMs to compute-optimized F32as_v6.
• Updated _MSVC_STL_UPDATE. #​5162 #​5217 #​5264 #​5323