https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114615
Bug ID: 114615
Summary: spurious warning on mingw-w64: 'memcpy' reading 4 or
more bytes from a region of size 2 with
std::wstring{L""} and -flto -O1 [Wstringop-overread]
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: bugzilla.gcc.simon at arlott dot org
Target Milestone: ---
This only happens on MinGW, when compiling with -flto, -municode and
optimisations. I get a spurious warning and it fails to optimise away the
constructor/destructor:
$ x86_64-w64-mingw32-g++ -o test.exe test.cc -flto -municode -O1
In function ‘wmemcpy’,
inlined from ‘copy’ at
/usr/lib/gcc/x86_64-w64-mingw32/12-win32/include/c++/bits/char_traits.h:558:16,
inlined from ‘_S_copy’ at
/usr/lib/gcc/x86_64-w64-mingw32/12-win32/include/c++/bits/basic_string.h:423:21,
inlined from ‘_S_copy_chars’ at
/usr/lib/gcc/x86_64-w64-mingw32/12-win32/include/c++/bits/basic_string.h:477:16,
inlined from ‘_M_construct’ at
/usr/lib/gcc/x86_64-w64-mingw32/12-win32/include/c++/bits/basic_string.tcc:243:21,
inlined from ‘__ct_comp ’ at
/usr/lib/gcc/x86_64-w64-mingw32/12-win32/include/c++/bits/basic_string.h:642:14,
inlined from ‘wmain’ at test.cc:5:23:
/usr/share/mingw-w64/include/wchar.h:1502:31: warning: ‘memcpy’ reading 4 or
more bytes from a region of size 2 [-Wstringop-overread]
1502 | return (wchar_t *) memcpy (_S1,_S2,_N*sizeof(wchar_t));
| ^
test.cc:
#include <windows.h>
#include <string>
int wmain(int argc, wchar_t *argv[], wchar_t *envp[]) {
std::wstring test{L""};
return 0;
}
I can reproduce it here on MinGW GCC 12.1.0 and 12.2.0:
https://godbolt.org/z/dv7Pb8nx4 (the MinGW GCC 13 compiler on there is
currently not working at all)
MinGW GCC 11.3.0 is ok.
