https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87296
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Known to work| |7.3.0
Keywords| |diagnostic
Last reconfirmed| |2018-09-13
CC| |msebor at gcc dot gnu.org
Ever confirmed|0 |1
Summary|-Wstringop-overflow false |-Wstringop-overflow false
|positive |positive due to bogus
| |MEM_REF type
Known to fail| |8.2.0, 9.0
--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed with the simplified C test case below. The warning sees a MEM_REF
(char[4], ...) as the destination of the strncpy call. Why the type is char[4]
is a mystery to me. I guess the type in MEM_REF really can't be trusted.
gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout pr87296.c
;; Function g (g, funcdef_no=0, decl_uid=1913, cgraph_uid=1, symbol_order=0)
g (struct S * p, const char * s)
{
void * _1;
char[4] * _2;
<bb 2> [local count: 1073741824]:
_1 = &MEM[(void *)p_3(D) + 4B];
_2 = &p_3(D)->a;
f (_2, _1);
__builtin_strncpy (_1, s_6(D), 6); [tail call]
return;
}
pr87296.c: In function ‘g’:
pr87296.c:11:3: warning: ‘__builtin_strncpy’ writing 6 bytes into a region of
size 4 overflows the destination [-Wstringop-overflow=]
11 | __builtin_strncpy (p->b, s, sizeof p->b);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
