https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117983
Bug ID: 117983
Summary: [13.2 regression] -Wstringop-overflow false positive
for __builtin_memmove from vector::insert
Product: gcc
Version: 13.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gasper.azman at gmail dot com
Target Milestone: ---
Repro on GCC 13.3 and 14: https://godbolt.org/z/EdfGEfGcr
code:
```
#include <cstdint>
#include <vector>
class buffer {
void push(std::vector<std::uint8_t> chunk);
std::vector<std::uint8_t> _data;
};
void buffer::push(std::vector<std::uint8_t> chunk) {
if (_data.empty()) {
_data.swap(chunk);
} else {
_data.insert(_data.end(), chunk.begin(), chunk.end());
}
}
```
As you can see, perfectly normal.
Compiling with `-Wall -Wextra -O3`:
x86-64 gcc 14.2 - 661ms (257546B) ~16635 lines filtered
In file included from
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/vector:62,
from <source>:2:
In static member function 'static _Up* std::__copy_move<_IsMove, true,
std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp =
unsigned char; _Up = unsigned char; bool _IsMove = false]',
inlined from '_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove =
false; _II = unsigned char*; _OI = unsigned char*]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_algobase.h:521:30,
inlined from '_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove =
false; _II = unsigned char*; _OI = unsigned char*]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_algobase.h:548:42,
inlined from '_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove =
false; _II = __gnu_cxx::__normal_iterator<unsigned char*, vector<unsigned char>
>; _OI = unsigned char*]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_algobase.h:555:31,
inlined from '_OI std::copy(_II, _II, _OI) [with _II =
__gnu_cxx::__normal_iterator<unsigned char*, vector<unsigned char> >; _OI =
unsigned char*]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_algobase.h:651:7,
inlined from 'static _ForwardIterator
std::__uninitialized_copy<true>::__uninit_copy(_InputIterator, _InputIterator,
_ForwardIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<unsigned
char*, std::vector<unsigned char> >; _ForwardIterator = unsigned char*]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_uninitialized.h:147:27,
inlined from '_ForwardIterator std::uninitialized_copy(_InputIterator,
_InputIterator, _ForwardIterator) [with _InputIterator =
__gnu_cxx::__normal_iterator<unsigned char*, vector<unsigned char> >;
_ForwardIterator = unsigned char*]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_uninitialized.h:185:15,
inlined from '_ForwardIterator std::__uninitialized_copy_a(_InputIterator,
_InputIterator, _ForwardIterator, allocator<_Tp>&) [with _InputIterator =
__gnu_cxx::__normal_iterator<unsigned char*, vector<unsigned char> >;
_ForwardIterator = unsigned char*; _Tp = unsigned char]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_uninitialized.h:373:37,
inlined from 'void std::vector<_Tp, _Alloc>::_M_range_insert(iterator,
_ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with
_ForwardIterator = __gnu_cxx::__normal_iterator<unsigned char*,
std::vector<unsigned char> >; _Tp = unsigned char; _Alloc =
std::allocator<unsigned char>]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/vector.tcc:1022:38,
inlined from 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp,
_Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with
_InputIterator = __gnu_cxx::__normal_iterator<unsigned char*,
std::vector<unsigned char> >; <template-parameter-2-2> = void; _Tp = unsigned
char; _Alloc = std::allocator<unsigned char>]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_vector.h:1488:19,
inlined from 'void buffer::push(std::vector<unsigned char>)' at
<source>:12:21:
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_algobase.h:452:30:
warning: 'void* __builtin_memcpy(void*, const void*, long unsigned int)'
writing between 2 and 9223372036854775807 bytes into a region of size 0
overflows the destination [-Wstringop-overflow=]
452 | __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/x86_64-linux-gnu/bits/c++allocator.h:33,
from
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/allocator.h:46,
from
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/vector:63:
In member function '_Tp* std::__new_allocator<_Tp>::allocate(size_type, const
void*) [with _Tp = unsigned char]',
inlined from 'static _Tp* std::allocator_traits<std::allocator<_Tp1>
>::allocate(allocator_type&, size_type) [with _Tp = unsigned char]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/alloc_traits.h:478:28,
inlined from 'std::_Vector_base<_Tp, _Alloc>::pointer
std::_Vector_base<_Tp, _Alloc>::_M_allocate(std::size_t) [with _Tp = unsigned
char; _Alloc = std::allocator<unsigned char>]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_vector.h:380:33,
inlined from 'void std::vector<_Tp, _Alloc>::_M_range_insert(iterator,
_ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with
_ForwardIterator = __gnu_cxx::__normal_iterator<unsigned char*,
std::vector<unsigned char> >; _Tp = unsigned char; _Alloc =
std::allocator<unsigned char>]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/vector.tcc:1013:40,
inlined from 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp,
_Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with
_InputIterator = __gnu_cxx::__normal_iterator<unsigned char*,
std::vector<unsigned char> >; <template-parameter-2-2> = void; _Tp = unsigned
char; _Alloc = std::allocator<unsigned char>]' at
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/stl_vector.h:1488:19,
inlined from 'void buffer::push(std::vector<unsigned char>)' at
<source>:12:21:
/opt/compiler-explorer/gcc-14.2.0/include/c++/14.2.0/bits/new_allocator.h:151:55:
note: at offset [-9223372036854775808, -1] into destination object of size [1,
9223372036854775807] allocated by 'operator new'
151 | return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n *
sizeof(_Tp)));
| ^
Compiler returned: 0
