https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111118
Bug ID: 111118 Summary: Bogus -Wstringop-overread with -std=gnu++20 -O2 and std::vector<bool> Product: gcc Version: 13.2.0 Status: UNCONFIRMED Keywords: alias, diagnostic, missed-optimization, patch Severity: normal Priority: P3 Component: middle-end Assignee: unassigned at gcc dot gnu.org Reporter: rogerio.souza at gmail dot com Target Milestone: --- The following C++ code compiled with "-c -O1 -std=gnu++20 -Werror=stringop-overread" emits a bogus warning/error with gcc trunk, while it works without problem when using "-O1 -std=gnu++17" or "-O0 -std=gnu++20" instead. Tested on compiler explorer on x64 Linux "https://godbolt.org/z/491jTvj65": #include <vector> struct S { std::vector<bool> p; void foo(); }; #ifdef INLINE inline #endif void S::foo() { p.reserve(64); } ======================= The code above works fine when running on GCC 12.3.0, but GCC starts raising the warning bellow sicne GCC v13.1. In file included from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/vector:62, from <source>:1: In static member function 'static constexpr _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp = long unsigned int; _Up = long unsigned int; bool _IsMove = false]', inlined from 'constexpr _OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false; _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:506:30, inlined from 'constexpr _OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = false; _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:533:42, inlined from 'constexpr _OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false; _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:540:31, inlined from 'constexpr _OI std::copy(_II, _II, _OI) [with _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:633:7, inlined from 'constexpr std::vector<bool, _Alloc>::iterator std::vector<bool, _Alloc>::_M_copy_aligned(const_iterator, const_iterator, iterator) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:1303:28, inlined from 'constexpr void std::vector<bool, _Alloc>::_M_reallocate(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/vector.tcc:851:40, inlined from 'constexpr void std::vector<bool, _Alloc>::reserve(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:1091:17, inlined from 'void S::foo()' at <source>:12:14: /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:437:30: warning: 'void* __builtin_memmove(void*, const void*, long unsigned int)' writing between 9 and 9223372036854775807 bytes into a region of size 8 overflows the destination [-Wstringop-overflow=] 437 | __builtin_memmove(__result, __first, sizeof(_Tp) * _Num); | ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/x86_64-linux-gnu/bits/c++allocator.h:33, from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/allocator.h:46, from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/vector:63: In member function '_Tp* std::__new_allocator<_Tp>::allocate(size_type, const void*) [with _Tp = long unsigned int]', inlined from 'constexpr _Tp* std::allocator< <template-parameter-1-1> >::allocate(std::size_t) [with _Tp = long unsigned int]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/allocator.h:198:40, inlined from 'static constexpr _Tp* std::allocator_traits<std::allocator<_Up> >::allocate(allocator_type&, size_type) [with _Tp = long unsigned int]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/alloc_traits.h:482:28, inlined from 'constexpr std::_Bvector_base<_Alloc>::_Bit_pointer std::_Bvector_base<_Alloc>::_M_allocate(std::size_t) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:643:48, inlined from 'constexpr void std::vector<bool, _Alloc>::_M_reallocate(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/vector.tcc:849:43, inlined from 'constexpr void std::vector<bool, _Alloc>::reserve(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:1091:17, inlined from 'void S::foo()' at <source>:12:14: /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/new_allocator.h:147:55: note: destination object of size 8 allocated by 'operator new' 147 | return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp))); | ^ ASM generation compiler returned: 0 In file included from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/vector:62, from <source>:1: In static member function 'static constexpr _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp = long unsigned int; _Up = long unsigned int; bool _IsMove = false]', inlined from 'constexpr _OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false; _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:506:30, inlined from 'constexpr _OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = false; _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:533:42, inlined from 'constexpr _OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false; _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:540:31, inlined from 'constexpr _OI std::copy(_II, _II, _OI) [with _II = long unsigned int*; _OI = long unsigned int*]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:633:7, inlined from 'constexpr std::vector<bool, _Alloc>::iterator std::vector<bool, _Alloc>::_M_copy_aligned(const_iterator, const_iterator, iterator) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:1303:28, inlined from 'constexpr void std::vector<bool, _Alloc>::_M_reallocate(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/vector.tcc:851:40, inlined from 'constexpr void std::vector<bool, _Alloc>::reserve(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:1091:17, inlined from 'void S::foo()' at <source>:12:14: /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_algobase.h:437:30: warning: 'void* __builtin_memmove(void*, const void*, long unsigned int)' writing between 9 and 9223372036854775807 bytes into a region of size 8 overflows the destination [-Wstringop-overflow=] 437 | __builtin_memmove(__result, __first, sizeof(_Tp) * _Num); | ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/x86_64-linux-gnu/bits/c++allocator.h:33, from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/allocator.h:46, from /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/vector:63: In member function '_Tp* std::__new_allocator<_Tp>::allocate(size_type, const void*) [with _Tp = long unsigned int]', inlined from 'constexpr _Tp* std::allocator< <template-parameter-1-1> >::allocate(std::size_t) [with _Tp = long unsigned int]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/allocator.h:198:40, inlined from 'static constexpr _Tp* std::allocator_traits<std::allocator<_Up> >::allocate(allocator_type&, size_type) [with _Tp = long unsigned int]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/alloc_traits.h:482:28, inlined from 'constexpr std::_Bvector_base<_Alloc>::_Bit_pointer std::_Bvector_base<_Alloc>::_M_allocate(std::size_t) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:643:48, inlined from 'constexpr void std::vector<bool, _Alloc>::_M_reallocate(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/vector.tcc:849:43, inlined from 'constexpr void std::vector<bool, _Alloc>::reserve(size_type) [with _Alloc = std::allocator<bool>]' at /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/stl_bvector.h:1091:17, inlined from 'void S::foo()' at <source>:12:14: /opt/compiler-explorer/gcc-13.1.0/include/c++/13.1.0/bits/new_allocator.h:147:55: note: destination object of size 8 allocated by 'operator new' 147 | return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp))); | ================================= This issue now is realted with "std::vector<bool>", but the issue "Bug 98465 - Bogus -Wstringop-overread with -std=gnu++20 -O2 and std::string::insert" is very similar, although it is related with "std::string::insert". Regards, Rogerio