https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77690
Bug ID: 77690
Summary: -Wformat-length %s false positive after strlen check
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: nsz at gcc dot gnu.org
Target Milestone: ---
there is no obvious way to silence the sprintf %s warning.
(this currently breaks the gdb build)
$ cat a.c
int sprintf (char*, const char*, ...);
struct { char buf[12]; } s;
void f(void)
{
char foo[7];
if (__builtin_strlen(s.buf) > 3) // this check does not help
return;
sprintf(foo, "zz%s", s.buf);
}
$ gcc -Wall -c a.c
a.c: In function 'f':
a.c:10:19: warning: '%s' directive writing between 0 and 11 bytes into a region
of size 5 [-Wformat-length=]
sprintf(foo, "zz%s", s.buf);
^~ ~
a.c:10:3: note: format output between 3 and 14 bytes into a destination of size
7
sprintf(foo, "zz%s", s.buf);
^~~~~~~~~~~~~~~~~~~~~~~~~~~
