Update libcxx to 8 July 2024

{% cut "Change log" %}

```
    [libc++] Add a test case for std::bit_cast with std::complex (#97751)
    [libc++] Update status after the St. Louis meeting. (#97951)
    [libc++] Guard transitive include of `<locale>` with availability macro (#97869)
    [libc++] Restore `__synth_three_way` lambda (#90398)
    [libc++][TZDB] Makes implementation experimental. (#95657)
    [libc++] Remove dead code from the locale base API and support code (#89070)
    [libc++] Assume newer LLVM versions for not-yet-released macOS versions
    [libc++] Remove annotations for GCC 13 and update the documentation (#97744)
    [libc++][test] Updates sized deallocation tests. (#97833)
    [libc++] Adds a missing include.
    [libc++] Use __is_array if the builtin is fixed (#93037)
    [libc++] Use _Complex for multiplication and division of complex floating point types (#83575)
    [libc++] Adds a new feature-test macro generator class. (#90889)
    [libc++][chrono] Fixes leap seconds. (#90070)
    [libc++] Upgrade to GCC 14 (#97205)
    [libc++] Fix the signatures of `std::rethrow_if_nested` (#91365)
    [libc++] Use GCC compilers from compiler explorer (#97219)
    Add a regression test for recent regression in pair. (#97355)
    [libcxx][Docs] Correct link syntax in hardening docs
    [libc++] Don't use a ppa for GCC
    [libc++] Upgrade to GCC 14 in the CI (#95212)
    [libc++abi] Fix test failures with GCC 14 (#95759)
    [libc++] Clean up and update deployment target features (#96312)
    [libc++] Fix how we pass /MANIFEST flag on Windows without clang-cl (#96967)
    [libc++] Classify iota_view precondition (#96662)
    [libc++] restrict the expected conversion constructor not compete against copy constructor (#96101)
    "[libc++] Try again LWG3233 Broken requirements for shared_ptr converting constructors" (#96103)
    [libc++] LWG3382: NTTP for `pair` and `array` (#85811)
    [libc++] Get the GCC build mostly clean of warnings (#96604)
    [libc++] P3029R1: Better `mdspan`'s CTAD - `std::extents` (#89015)
    [libc++] Move allocator assertion into allocator_traits (#94750)
    [libc++] change the visibility of libc++ header to public in libcxx module (#91240)
    [libc++] Use _If for conditional_t (#96193)
    [libc++] Remove the allocator<const T> extension (#96319)
    [libc++] Fix incorrect overflow checking in std::lcm (#96310)
    [libc++] Use __is_nothrow_destructible (#95766)
    [libc++] Remove Windows-specific configuration from libcxx/test/CMakeLists.txt (#96330)
    [libc++] Build with -fsized-deallocation (#96217)
    [libc++] <experimental/simd> Add swap functions of simd reference (#86478)
    [libc++] Fix deployment target Lit features (#94791)
    [libc++] Workaround clang bug in __has_unique_object_representations (#95314)
    [libc++] Remove <ostream> include from <chrono> (#96035)
    [libc++] Fix triviality of std::pair for trivially copyable types without an assignment operator (#95444)
    [libc++] Install Python packaging to resolve LLDB data formatter issues (#95971)
    [libc++] Properly define _LIBCPP_HAS_NO_UNICODE in __config_site (#95138)
    [libc++] Refactor<__type_traits/is_swappable.h> (#86822)
    [libc++] Enable modernize-use-equals-delete (#93293)
    [libc++] Test suite adjustments on macOS (#95835)
    [libc++] Guard transitive include of `<locale>` with availability macro (#95686)
    [libc++] Mark more types as trivially relocatable (#89724)
    [libcxx] [ci] Simplify the mingw x86_64 configs (#95609)
    [libc++][TZDB] Disables a failing test. (#95659)
    [libc++] Add default copy ctor to "__chrono/exception.h" (#95338)
    [libcxx][test][AIX] address more platform differences in locale tests (#94826)
    [libc++] Remove unnecessary #ifdef guards around PSTL implementation details (#95268)
    [libc++] Mark local_time test as a long test (#95170)
    Update actions-runner version for libc++ builder images
    [libc++] Move the implementation of CPU-based basis operations to namespace __pstl (#95267)
    [libc++][modules] Mark as implemented. (#90091)
    [libc++] Adds __cpp_lib_three_way_comparison FTM. (#91515)
    [libc++] Overhaul the PSTL dispatching mechanism (#88131)
    [libcxx] Correct and clean-up filesystem operations error_code paths (#88341)
    [libc++][z/OS] Disable portion of formatter.char.funsigned-char.pass.cpp for no unicode (#94044)
    [libc++] Mark a few functions in the dylib as noexcept (#94098)
    [libc++] Fix UB in filesystem::__copy for non-existent destination. (#87615)
    [libc++] Simplify the definition of string::operator== (#95000)
    [libc++] Update with LWG issue number for shared-ptr constructor
    [libc++] Tweak how we check constraints on shared_ptr(nullptr_t) (#94996)
    [HWASan] make get_info.local_time.pass.cpp UNSUPPORTED
     [libc++] Fix endianness for algorithm mismatch (#93082)
    [HWASan] skip libcxx test that times out with hwasan
    [libc++][TZDB] Implements zoned_traits. (#91059)
    [libc++][test] Avoid `-Wunused-variable` warnings in mutex tests (#94907)
    [libc++] Fix invalid escape sequences in Python comments (#94032)
    [libc++][TZDB] Implements time_zone::to_local. (#91003)
    [libc++][TZDB] Implements time_zone::to_sys. (#90901)
    [libc++][TZDB] Implements time_zone::to_sys. (#90394)
    [libc++][TZDB] Implements time_zone get_info(local_time). (#89537)
    [libc++] Undeprecate shared_ptr atomic access APIs (#92920)
    [libc++][regex] Correctly adjust match prefix for zero-length matches. (#94550)
    [libc++][test][AIX] Only XFAIL atomic tests for before clang 19 (#94646)
    [libc++] Fix naming of value template parameters (#76888)
    [libc++][hardening] Finish documenting hardening. (#92021)
    Fix detection of __datasizeof with Clang. (#94174)
    [libc++] Fix SyntaxWarning messages from python 3.12 (#93637)
    [libc++] [test] Consistently use `REQUIRES: has-unix-headers` (#94122)
    [libc++] Add missing noexcept to span constructor (#94381)
    Remove act from builder image. It never turned out to be useful
    [libc++] Adjust XFAIL for quick_exit (#94274)
    [libc++] Properly detect whether C++20 modules are supported by the compiler (#94275)
    [libc++] Handle 0 size case for testing support operator new (#93834)
    [libc++] Fix regression about parsing leading decimal points (#93989)
    [libc++][test] Mark `optional` test functions as `TEST_CONSTEXPR_CXX20` (#94172)
    [clang][Modules] Remove unnecessary includes of `Module.h` (#93417)
    [libc++] Don't give functions C linkage (#94102)
    [libc++] [test] Cleanup compile-only tests (#94121)
    [libc++] [test] Fix `__has_include` usage, expand condvarany and spaceship coverage (#94120)
    [libc++] Fix `std::atomic::wait` ulock wait UL_COMPARE_AND_WAIT64 (#92783)
    Fix order of include flags for the target & regular include paths. (#93547)
     [libc++] Fix failures with GCC 14 (#92663)
    [libc++] Remove the inline namespace for std::filesystem in ABIv2 (#92971)
    [runtimes] Correctly apply libdir subdir for multilib (#93354)
    [clang] Preserve Qualifiers and type sugar in TemplateNames (#93433)
    [libc++][test] Close LWG3018 and add tests (#93047)
    [runtimes][CMake] Simplify the propagation of test dependencies (#93558)
    [runtimes] Reintroduce a way to select the compiler used for the test suite (#93542)
    [libc++] Make the __availability header a sub-header of __config (#93083)
    [libc++][test] Close LWG3238 and add tests (#93043)
    [libc++] LWG3223 Broken requirements for shared_ptr converting constructors (#93071)
    [libc++][test] Close LWG3382 and add tests (#93039)
    [libc++] [test] Fix portability issues for MSVC (#93259)
    [libc++] [test] Fix MSVC warnings (#93257)
    [libc++] Mark P2845R8 `__cpp_lib_format_path` and P2587R3 `__cpp_lib_to_string` as C++26 (#93255)
    [libc++] Split up ABI and platform configuration to their own headers (#90863)
    [libc++][pstl] Merge all frontend functions for the PSTL (#89219)
    [libcxx][test][AIX] Fix the thousands_sep expectation for fr_FR locales (#92312)
    [libcxx] [test] Use `shlex.quote()` to fix Python 3.13 compatibility (#93376)
    [libc++] Remove libcxx/include/libcxx.imp
    Revise IDE folder structure (#89755)
    [libc++][test] Close LWG3045 (#93053)
    [libc++] Remove a few unused includes of trivially_copyable.h (#93200)
    [test][libcxx] Update deallocation after #90373 (#93145)
    [libc++] Refactor tests for std::condition_variable (#91530)
    Removed redundant template in '__delete_node()' member function of '__forward_list_base' and '__list_imp' classes. (#84323)
    [libc++][pstl] Improve exception handling (#88998)
    [WebAssembly] Upstream misc. EH changes (#92990)
    [libc++] <experimental/simd> Add copy functions for class simd/simd_mask (#78935)
    [libc++][vector] Inline remaining constructors filling vector with the same value (#82068)
    Reland "[clang] Enable sized deallocation by default in C++14 onwards" (#90373)
    [libc++] Implement C++20 atomic_ref (#76647)
    [libc++] Refactor flaky tests for std::shared_lock (#91779)
    [libcxx] [test] Detect mingw-w64 headers compatible with C++ module builds (#92893)
    [libc++] LWG2381: Inconsistency in parsing floating point numbers (#77948)
    [libcxx] removes unnecessary traits from `has_unique_object_representations` (#69241)
    [libc++][z/OS] Switch to use TEST_HAS_NO_INT128 as per comment in PR 92261 (#92434)
    [libcxx] Add cast to avoid pointer casting warning on Windows (#92738)
    [libcxx] locale.cpp: Move build_name helper into unnamed namespace (#92461)
    [libcxx][libcxxabi] Fix build for OpenBSD (#92186)
    [libc++] LWG3672: `common_iterator::operator->()` should return by value (#87899)
    [libc++][z/OS] Correct a definition of __native_vector_size (#91995)
    [libc++][z/OS] Fixup two linear_congruential_engine tests (#92261)
    [libc++][test] `__cpp_lib_within_lifetime` -> `__cpp_lib_is_within_lifetime` (#91896)
    Fix typo "indicies" (#92232)
    [libcxx][test] Fix numpunct grouping tests on AIX (#91781)
    [libcxx] [test] Fix the locale ctype widen tests on AIX (#91744)
    [libc++] Vectorize std::mismatch with trivially equality comparable types (#87716)
    [libc++] Make `constexpr std::variant`. Implement P2231R1 (#83335)
    [libc++][doc] Updates Spaceship status page.
    [libc++][ASan] Fix std::basic_string trait type (#91590)
    [libc++][test] Fixes constexpr char_traits. (#90981)
    [libc++][functional] P2944R3 (partial): Comparisons for `reference_wrapper` (`reference_wrapper` operators only) (#88384)
    [libc++][CI] Reenables clang-tidy. (#90077)
    [libc++] Implement std::gcd using the binary version (#77747)
    [ASan][libc++] Turn on ASan annotations for short strings (#79536)
    [AIX][libc++] Enable clang_modules_include.gen.py tests (#90971)
    [libc++] Rename _LIBCPP_INTRODUCED_foo_MARKUP to _LIBCPP_INTRODUCED_foo_ATTRIBUTE (#91269)
    [libc++] Fix P1206R7 feature test macros (#90914)
    [libc++] Adjust some of the [rand.dist] critical values that are too strict (#88669)
    [libc++][modules] Uses _LIBCPP_USING_IF_EXISTS. (#90409)
    Bump actions runner image used for libc++'s builders.
    [libcxx] Align `__recommend() + 1`  by __endian_factor (#90292)
    [libc++] Granularize <ostream> (#85537)
    [libc++] Remove a few __has_foo defines in __config (#90511)
    [libc++] Remove _LIBCPP_DISABLE_ADDITIONAL_DIAGNOSTICS (#90512)
    [libcxx][ci] In picolib build, ask clang for the normalised triple (#90722)
    [libc++][ranges] Implement LWG4053 and LWG4054 (#88612)
    [libc++] Some tests are missing include for `numeric_limits` (#90345)
    [libc++] Mark scoped_lock and unique_lock constructors as [[nodiscard]] (#89397)
    [libc++] Improve libc++ tests when using optimizations (#88897)
    [libc++][modules] Enable installation by default. (#90094)
    [libc++][format] Improves escaping performance. (#88533)
    [libcxx] Remove empty ~__no_destroy (#89882)
    [libc++][ranges] Exports operator|. (#90071)
    [C++17] Support __GCC_[CON|DE]STRUCTIVE_SIZE (#89446)
    [libc++][ranges] LWG3984: ranges::to's recursion branch may be ill-formed (#87964)
    [clang] Enable sized deallocation by default in C++14 onwards (#83774)
    [libc++][format] Improves escaping. (#88283)
    [libc++] Implement LWG4023 (#87513)
    [libc++] Reformulate availability in terms of LLVM releases (#87563)
    [libc++] Reorganize the std::variant macros (#89419)
    [libc++][format] Adds an escaped output benchmark. (#88020)
    [libc++] Makes saturation functions privately available. (#89503)
    [libcxx] [modules] Add _LIBCPP_USING_IF_EXISTS on aligned_alloc (#89827)
    [libc++][TZDB] Fixes reverse time lookups. (#89502)
    [libc++][doc] Updates module build instructions. (#89413)
    [libc++][chrono] Fixes format output of negative values. (#89408)
    [libc++][ranges] export `std::ranges::range_adaptor_closure` (#89793)
    [libc++][ranges] P2387R3: Pipe support for user-defined range adaptors (#89148)
    [libc++] Add some private headers to libcxx.imp (#89568)
    [libc++] Remove _LIBCPP_DISABLE_NODISCARD_EXTENSIONS and refactor the tests (#87094)
    [libc++] Remove stray CMake install step for modulemap file (#89394)
    [libc++] Don't commit libcxx.imp (#89391)
    [libc++] Removes a Clang 16 Windows workaround. (#88560)
    [libc++][TZDB] Renames incomplete. (#89250)
    [libc++] Optimize char_traits a bit (#72799)
    [libc++] Fix usage of 'exclude_from_explicit_instantiation' attribute on local class members (#89377)
    linear_congruential_engine: add using more precision to prevent overflow (#81583)
    CompilerRT: Normalize COMPILER_RT_DEFAULT_TARGET_TRIPLE (#89234)
    [libc++][TZDB] Adds local_info formatter. (#86256)
    [libc++][pstl] Move the CPU algorithm implementations to __pstl (#89109)
    [libc++][TZDB] Adds sys_info formatter. (#85896)
    [libc++][pstl] Promote CPU backends to top-level backends (#88968)
    [libc++][chrono] Improves date formatting. (#86127)
    [libc++] Add missing iterator requirement checks in the PSTL (#88127)
    [libc++][TZDB] Improves time zone format specifiers. (#85797)
    [libc++][chrono] Disables a test.
    [libc++][doc] Documents -DLIBCXX_INSTALL_MODULES=ON. (#88547)
    [libc++][test] Removes Clang 16 validation. (#88558)
    [libc++] Removes deprecated _LIBCPP_ENABLE_<VERSION>_REMOVED_FEATURES macros (#88548)
    [libc++][modules] Removes some validation quirks. (#88031)
    [libc++] Deprecate the C++20 synchronization library before C++20 (#86410)
    [libc++] Use availability to rely on key functions for bad_expected_access and bad_function_call (#87390)
    [libc++] Rename __cpu_traits functions (#88741)
    [libc++][CI] Tests LLDB libc++ data formatters. (#88312)
    [libc++] Add a utility to check whether a range is valid (#87665)
    [libc++][PSTL] Introduce cpu traits (#88134)
    [libc++][RFC] Only include what is required by-version in the umbrella headers (#83740)
    [libc++] Deprecated `shared_ptr` Atomic Access APIs as per P0718R2 & Implemented P2869R3: Remove Deprecated `shared_ptr` Atomic Access APIs from C++26 (#87111)
    [libc++][TZDB] Removes test_indian_kerguelen test.
    [libc++][TZDZ] Validates the database version.
    [libc++] Undeprecate POSIX STREAM macros. (#88296)
    [libc++] Marks a variable const. (#88562)
    [libc++][CMake] Removes LIBCXX_ENABLE_CLANG_TIDY. (#85794)
    [tzdb] Replace shared_mutex with mutex. (#87929)
    [libc++] P3029R1: Better `mdspan`'s CTAD (#87873)
    [libc++][ranges] LWG3736: move_iterator missing disable_sized_sentinel_for specialization (#85611)
    [libc++] LWG3643: Missing `constexpr` in `std::counted_iterator` (#87901)
    [libcxx] applies changes regarding post-commit feedback to #75259 (#76534)
    [libc++] Fix -Wgnu-include-next in stddef.h (#88214)
    [libcxx] Use generic builtins for popcount, clz and ctz (#86563)
    [libc++] Adds a global private constructor tag. (#87920)
    [libc++] Removes Clang-16 support. (#87810)
    [lib++][CI] Changes bootstrap build type. (#88175)
    [libc++][CI] Updates Docker LLDB dependencies. (#88174)
    [libc++][chrono] Adds the sys_info class. (#85619)
    [libc++][format] Switches to Unicode 15.1. (#86543)
    [libc++] Avoids using ENODATA. (#86165)
    [libc++][TZDB] Fixes relative path resolving. (#87882)
    [libc++][format] adds a basic fuzzer test. (#87883)
    [libc++] Add test coverage for our implementation of LWG4031 (#87508)
    [libc++] Implement `bind_back` (#81055)
    [libc++][format] Fixed `println.blank_line.sh.cpp` test on llvm-clang-win-x-* configurations (#88011)
    [libc++][doc] Updates format status page.
    [libc++][format] P3142R0: Printing Blank Lines with `println` (#87277)
    [libc++] Optimize ranges::minmax (#87335)
    [libc++] Implement LWG3430 disallow implicit conversion of the source arguments to `std::filesystem::path` when constructing `std::basic_*fstream` (#85079)
    [libc++] P2872R3: Remove ``wstring_convert`` From C++26 (#87100)
    Fix issue with never-constexpr __construct_at in C++ < 20. (#87403)
    [libcxx] coerce formatter precision to int (#87738)
    [libc++][CI] Updates to Clang 19. (#85301)
    [libc++][chrono] Completes the tzdb class. (#82157)
    [libc++][oss-fuzz] Updates C++ version used. (#87531)
    [libc++] P2867R1: Remove Deprecated `strstream`s From C++26 (#87107)
    [libc++] Fix copy/pasta error in atomic tests for `atomic_compare_exchange_{weak,strong}` (#87135)
    [libc++] Mark some recent LWG issues and papers as done (#87502)
    [libc++][chrono] Loads leap-seconds.list in tzdb. (#82113)
    [libc++] Disables -Wweak-vtables diagnostics. (#85577)
    [libc++] Update status page after the Tokyo meeting (#87395)
    [libc++] Upstream ptrauth support in libc++ and libc++abi (#84573)
    [libc++] Fix tests on musl (#85085) (#86934)
    [libc++] Add a static_assert for a Mandates in seed_seq (#86992)
    [libc++][ranges] Avoid using `distance` in `ranges::contains_subrange` (#87155)
    [libc++] `std::ranges::advance`: avoid unneeded bounds checks when advancing iterator (#84126)
```

{% endcut %}
commit_hash:45feb9db5b173f12bf29de2a3ee73006d4371a4e

1 files changed, 38 insertions, 27 deletions

diff --git a/contrib/libs/cxxsupp/libcxx/include/regex b/contrib/libs/cxxsupp/libcxx/include/regex
index dc3db93744b..b8141351213 100644
--- a/contrib/libs/cxxsupp/libcxx/include/regex
+++ b/contrib/libs/cxxsupp/libcxx/include/regex
@@ -792,7 +792,6 @@ typedef regex_token_iterator<wstring::const_iterator> wsregex_token_iterator;
 #include <__algorithm/find.h>
 #include <__algorithm/search.h>
 #include <__assert>
-#include <__availability>
 #include <__config>
 #include <__iterator/back_insert_iterator.h>
 #include <__iterator/default_sentinel.h>
@@ -1346,13 +1345,12 @@ struct __state {
 
 template <class _CharT>
 class __node {
-  __node(const __node&);
-  __node& operator=(const __node&);
-
 public:
   typedef std::__state<_CharT> __state;
 
   _LIBCPP_HIDE_FROM_ABI __node() {}
+  __node(const __node&)            = delete;
+  __node& operator=(const __node&) = delete;
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL
   virtual ~__node() {}
 
@@ -1953,14 +1951,14 @@ class __match_char : public __owns_one_state<_CharT> {
 
   _CharT __c_;
 
-  __match_char(const __match_char&);
-  __match_char& operator=(const __match_char&);
-
 public:
   typedef std::__state<_CharT> __state;
 
   _LIBCPP_HIDE_FROM_ABI __match_char(_CharT __c, __node<_CharT>* __s) : base(__s), __c_(__c) {}
 
+  __match_char(const __match_char&)            = delete;
+  __match_char& operator=(const __match_char&) = delete;
+
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
 };
 
@@ -1985,15 +1983,15 @@ class __match_char_icase : public __owns_one_state<_CharT> {
   _Traits __traits_;
   _CharT __c_;
 
-  __match_char_icase(const __match_char_icase&);
-  __match_char_icase& operator=(const __match_char_icase&);
-
 public:
   typedef std::__state<_CharT> __state;
 
   _LIBCPP_HIDE_FROM_ABI __match_char_icase(const _Traits& __traits, _CharT __c, __node<_CharT>* __s)
       : base(__s), __traits_(__traits), __c_(__traits.translate_nocase(__c)) {}
 
+  __match_char_icase(const __match_char_icase&)            = delete;
+  __match_char_icase& operator=(const __match_char_icase&) = delete;
+
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
 };
 
@@ -2018,15 +2016,15 @@ class __match_char_collate : public __owns_one_state<_CharT> {
   _Traits __traits_;
   _CharT __c_;
 
-  __match_char_collate(const __match_char_collate&);
-  __match_char_collate& operator=(const __match_char_collate&);
-
 public:
   typedef std::__state<_CharT> __state;
 
   _LIBCPP_HIDE_FROM_ABI __match_char_collate(const _Traits& __traits, _CharT __c, __node<_CharT>* __s)
       : base(__s), __traits_(__traits), __c_(__traits.translate(__c)) {}
 
+  __match_char_collate(const __match_char_collate&)            = delete;
+  __match_char_collate& operator=(const __match_char_collate&) = delete;
+
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
 };
 
@@ -2062,9 +2060,6 @@ class __bracket_expression : public __owns_one_state<_CharT> {
   bool __collate_;
   bool __might_have_digraph_;
 
-  __bracket_expression(const __bracket_expression&);
-  __bracket_expression& operator=(const __bracket_expression&);
-
 public:
   typedef std::__state<_CharT> __state;
 
@@ -2079,6 +2074,9 @@ public:
         __collate_(__collate),
         __might_have_digraph_(__traits_.getloc().name() != "C") {}
 
+  __bracket_expression(const __bracket_expression&)            = delete;
+  __bracket_expression& operator=(const __bracket_expression&) = delete;
+
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
 
   _LIBCPP_HIDE_FROM_ABI bool __negated() const { return __negate_; }
@@ -2700,9 +2698,6 @@ class __lookahead : public __owns_one_state<_CharT> {
   unsigned __mexp_;
   bool __invert_;
 
-  __lookahead(const __lookahead&);
-  __lookahead& operator=(const __lookahead&);
-
 public:
   typedef std::__state<_CharT> __state;
 
@@ -2710,6 +2705,9 @@ public:
   __lookahead(const basic_regex<_CharT, _Traits>& __exp, bool __invert, __node<_CharT>* __s, unsigned __mexp)
       : base(__s), __exp_(__exp), __mexp_(__mexp), __invert_(__invert) {}
 
+  __lookahead(const __lookahead&)            = delete;
+  __lookahead& operator=(const __lookahead&) = delete;
+
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __exec(__state&) const;
 };
 
@@ -4215,11 +4213,7 @@ public:
   _LIBCPP_HIDE_FROM_ABI int compare(const string_type& __s) const { return str().compare(__s); }
   _LIBCPP_HIDE_FROM_ABI int compare(const value_type* __s) const { return str().compare(__s); }
 
-  _LIBCPP_HIDE_FROM_ABI void swap(sub_match& __s)
-#ifndef _LIBCPP_CXX03_LANG
-      _NOEXCEPT(__is_nothrow_swappable<_BidirectionalIterator>::value)
-#endif // _LIBCPP_CXX03_LANG
-  {
+  _LIBCPP_HIDE_FROM_ABI void swap(sub_match& __s) _NOEXCEPT_(__is_nothrow_swappable_v<_BidirectionalIterator>) {
     this->pair<_BidirectionalIterator, _BidirectionalIterator>::swap(__s);
     std::swap(matched, __s.matched);
   }
@@ -4583,7 +4577,7 @@ public:
   // size:
   _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __matches_.size(); }
   _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return __matches_.max_size(); }
-  _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT { return size() == 0; }
+  _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT { return size() == 0; }
 
   // element access:
   _LIBCPP_HIDE_FROM_ABI difference_type length(size_type __sub = 0) const {
@@ -4701,6 +4695,9 @@ private:
 
   template <class, class>
   friend class __lookahead;
+
+  template <class, class, class>
+  friend class regex_iterator;
 };
 
 template <class _BidirectionalIterator, class _Allocator>
@@ -5411,7 +5408,9 @@ template <class _BidirectionalIterator, class _CharT, class _Traits>
 regex_iterator<_BidirectionalIterator, _CharT, _Traits>&
 regex_iterator<_BidirectionalIterator, _CharT, _Traits>::operator++() {
   __flags_ |= regex_constants::__no_update_pos;
-  _BidirectionalIterator __start = __match_[0].second;
+  _BidirectionalIterator __start        = __match_[0].second;
+  _BidirectionalIterator __prefix_start = __start;
+
   if (__match_[0].first == __match_[0].second) {
     if (__start == __end_) {
       __match_ = value_type();
@@ -5425,9 +5424,21 @@ regex_iterator<_BidirectionalIterator, _CharT, _Traits>::operator++() {
     else
       ++__start;
   }
+
   __flags_ |= regex_constants::match_prev_avail;
-  if (!std::regex_search(__start, __end_, __match_, *__pregex_, __flags_))
+  if (!std::regex_search(__start, __end_, __match_, *__pregex_, __flags_)) {
     __match_ = value_type();
+
+  } else {
+    // The Standard mandates that if `regex_search` returns true ([re.regiter.incr]), "`match.prefix().first` shall be
+    // equal to the previous value of `match[0].second`... It is unspecified how the implementation makes these
+    // adjustments." The adjustment is necessary if we incremented `__start` above (the branch that deals with
+    // zero-length matches).
+    auto& __prefix   = __match_.__prefix_;
+    __prefix.first   = __prefix_start;
+    __prefix.matched = __prefix.first != __prefix.second;
+  }
+
   return *this;
 }