https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98158
Bug ID: 98158
Summary: Gcc generates warning about its own generated move
assignment operator
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: darklythinking at yahoo dot com
Target Milestone: ---
Version:
$ gcc --version
gcc (Gentoo 10.2.0-r3 p4) 10.2.0
System:
The bug doesn't happen if no arch is specified but with -march=skylake or
-march=znver2 the warning appears(and probably others but those are the 2 I
tested)
Code:
#include <string>
#include <cstdint>
struct test
{
std::string a;
std::uint8_t b[16];
std::uint8_t c[16];
};
test function(test blah)
{
blah = {};
return blah;
}
int main(int argc, char *argv[])
{
return 0;
}
Output:
$ g++ -O3 -march=skylake test.cpp
In member function ‘test& test::operator=(test&&)’,
inlined from ‘test function(test)’ at test.cpp:13:10:
test.cpp:4:8: warning: writing 32 bytes into a region of size 16
[-Wstringop-overflow=]
4 | struct test
| ^~~~
test.cpp: In function ‘test function(test)’:
test.cpp:7:15: note: at offset 0 to object ‘test::b’ with size 16 declared here
7 | std::uint8_t b[16];
| ^
Note that the warning actually happens in a move assignment operator generated
by gcc itself.
The warning also appears if std::vector is used instead of the std::string but
I wasn't able to replace it with a struct or static array of any size and
reproduce the bug that way.
