At least with a recent GCC 7 trunk build ("gcc (GCC) 7.0.1 20170221
(experimental)"), I noticed that -Wformat-truncation warnings happen to
not be emitted if and only if -Og is given:
$ cat test.c
#include <stdio.h>
int main() {
char buf[3];
snprintf(buf, sizeof buf, "%s", "foo");
return 0;
}
$ gcc -Wformat-truncation -Og ~/test.c
$ gcc -Wformat-truncation -O ~/test.c
test.c: In function ‘main’:
test.c:4:34: warning: ‘snprintf’ output truncated before the last format
character [-Wformat-truncation=]
snprintf(buf, sizeof buf, "%s", "foo");
^
test.c:4:5: note: ‘snprintf’ output 4 bytes into a destination of size 3
snprintf(buf, sizeof buf, "%s", "foo");
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Any other optimization level (-O1..3/s/fast) does emit the warning. The
documentation makes it clear that the behavior of that warning may be
coupled to the optimization level, but this difference between -Og and
everything else still looks somewhat odd. Could it be by mistake?
