https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110807
Bug ID: 110807
Summary: Copy list initialisation of a vector<bool> raises a
warning with -O2
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: twic at urchin dot earth.li
Target Milestone: ---
Created attachment 55631
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55631&action=edit
the source coded needed to reproduce the problem
If you have a class with a vector<bool> member:
struct Foo {
std::vector<bool> byCallSpread;
};
And try to initialise it with copy list initialisation:
Foo() { byCallSpread = {true, false}; }
Then that works fine with the default optimisation level, but gets a warning at
-O2 saying:
/usr/local/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);
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(i believe this is the relevant error - i am not very good at reading error
messages, so apologies if not)
The warning goes away if the initialisation uses an explicit constructor:
Foo() { byCallSpread = std::vector<bool>({true, false}); }
I did not get this warning with GCC 7.2.0. According to Compiler Explorer, it
does not occur with GCC 12.3.
Here is a transcript of a self-contained session using the GCC 13.1.0 official
Docker image (official for Docker, perhaps not for GCC!) which demonstrates the
problem:
$ sudo docker run -it gcc:13.1.0
root@4694030a8bea:/# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-linux-gnu/13.1.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: /usr/src/gcc/configure --build=x86_64-linux-gnu
--disable-multilib --enable-languages=c,c++,fortran,go
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.1.0 (GCC)
root@4694030a8bea:/# cat >foo.cpp
#include <vector>
struct Foo {
std::vector<bool> byCallSpread;
Foo() { byCallSpread = {true, false}; }
};
Foo f;
int main(int argc, char** argv) {}
root@4694030a8bea:/# g++ foo.cpp
root@4694030a8bea:/# g++ -O2 foo.cpp
In file included from /usr/local/include/c++/13.1.0/vector:62,
from foo.cpp:1:
In static member function 'static _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 '_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove =
false; _II = long unsigned int*; _OI = long unsigned int*]' at
/usr/local/include/c++/13.1.0/bits/stl_algobase.h:506:30,
inlined from '_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove =
false; _II = long unsigned int*; _OI = long unsigned int*]' at
/usr/local/include/c++/13.1.0/bits/stl_algobase.h:533:42,
inlined from '_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove =
false; _II = long unsigned int*; _OI = long unsigned int*]' at
/usr/local/include/c++/13.1.0/bits/stl_algobase.h:540:31,
inlined from '_OI std::copy(_II, _II, _OI) [with _II = long unsigned int*;
_OI = long unsigned int*]' at
/usr/local/include/c++/13.1.0/bits/stl_algobase.h:633:7,
inlined from 'std::vector<bool, _Alloc>::iterator std::vector<bool,
_Alloc>::_M_copy_aligned(const_iterator, const_iterator, iterator) [with _Alloc
= std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:1303:28,
inlined from 'void std::vector<bool, _Alloc>::_M_insert_range(iterator,
_ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with
_ForwardIterator = const bool*; _Alloc = std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/vector.tcc:915:33,
inlined from 'std::vector<bool, _Alloc>::iterator std::vector<bool,
_Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with
_InputIterator = const bool*; <template-parameter-2-2> = void; _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:1180:19,
inlined from 'void std::vector<bool,
_Alloc>::_M_assign_aux(_ForwardIterator, _ForwardIterator,
std::forward_iterator_tag) [with _ForwardIterator = const bool*; _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:1440:14,
inlined from 'void std::vector<bool, _Alloc>::assign(_InputIterator,
_InputIterator) [with _InputIterator = const bool*; <template-parameter-2-2> =
void; _Alloc = std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:935:17,
inlined from 'std::vector<bool, _Alloc>& std::vector<bool,
_Alloc>::operator=(std::initializer_list<bool>) [with _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:915:14,
inlined from 'Foo::Foo()' at foo.cpp:6:40,
inlined from 'void __static_initialization_and_destruction_0()' at
foo.cpp:9:5,
inlined from '(static initializers for foo.cpp)' at foo.cpp:11:34:
/usr/local/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
/usr/local/include/c++/13.1.0/x86_64-linux-gnu/bits/c++allocator.h:33,
from /usr/local/include/c++/13.1.0/bits/allocator.h:46,
from /usr/local/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 'static _Tp* std::allocator_traits<std::allocator<_Tp1>
>::allocate(allocator_type&, size_type) [with _Tp = long unsigned int]' at
/usr/local/include/c++/13.1.0/bits/alloc_traits.h:482:28,
inlined from 'std::_Bvector_base<_Alloc>::_Bit_pointer
std::_Bvector_base<_Alloc>::_M_allocate(std::size_t) [with _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:643:48,
inlined from 'void std::vector<bool, _Alloc>::_M_insert_range(iterator,
_ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with
_ForwardIterator = const bool*; _Alloc = std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/vector.tcc:913:39,
inlined from 'std::vector<bool, _Alloc>::iterator std::vector<bool,
_Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with
_InputIterator = const bool*; <template-parameter-2-2> = void; _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:1180:19,
inlined from 'void std::vector<bool,
_Alloc>::_M_assign_aux(_ForwardIterator, _ForwardIterator,
std::forward_iterator_tag) [with _ForwardIterator = const bool*; _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:1440:14,
inlined from 'void std::vector<bool, _Alloc>::assign(_InputIterator,
_InputIterator) [with _InputIterator = const bool*; <template-parameter-2-2> =
void; _Alloc = std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:935:17,
inlined from 'std::vector<bool, _Alloc>& std::vector<bool,
_Alloc>::operator=(std::initializer_list<bool>) [with _Alloc =
std::allocator<bool>]' at
/usr/local/include/c++/13.1.0/bits/stl_bvector.h:915:14,
inlined from 'Foo::Foo()' at foo.cpp:6:40,
inlined from 'void __static_initialization_and_destruction_0()' at
foo.cpp:9:5,
inlined from '(static initializers for foo.cpp)' at foo.cpp:11:34:
/usr/local/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)));
| ^
I have attached the code from this session to this issue.
