https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84212
Bug ID: 84212
Summary: -Wno-* does not disable warnings from -flto link stage
Product: gcc
Version: 7.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: jay.foad at gmail dot com
CC: marxin at gcc dot gnu.org
Target Milestone: ---
See example below: I'm getting warnings emitted by the -flto link stage. I'd
like to selectively disable these warnings in my build scripts, but the usual
-Wno-* option doesn't seem to have any effect.
(I know the warning is justified in this simple example. But in my real
proprietary application code I'm getting false positive warnings from the lto
link stage that I'd really like to be able to disable.)
$ gcc --version
gcc (Ubuntu 7.2.0-8ubuntu3) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ cat a.c
#include <string.h>
void a(char * x, int n) {
memset(x, 0, n);
}
$ cat b.c
void a(char *, int);
int main() {
char x[3];
a(x, 4);
}
$ gcc -O3 -flto -c a.c b.c -Wno-stringop-overflow
$ gcc -O3 -flto a.o b.o -Wno-stringop-overflow
In function ‘memset’,
inlined from ‘main’ at a.c:3:2:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:71:10: warning:
‘__builtin___memset_chk’ writing 4 bytes into a region of size 3 overflows the
destination [-Wstringop-overflow=]
return __builtin___memset_chk (__dest, __ch, __len, __bos0 (__dest));
^
