https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79956
--- Comment #3 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Testcase that only warns with -O3
int a, b, c;
void fn1() {
int d[1];
int e, n = a;
for (; 0; n++)
;
c = 1;
while (c) {
if (a)
for (;;)
;
while (d[0]) {
e -= 0;
if (b)
break;
}
}
}
% gcc -c -Wall -Wextra -O2 parity_l8.i -Werror -Wfatal-errors
% gcc -c -Wall -Wextra -O3 parity_l8.i -Werror -Wfatal-errors
parity_l8.i: In function ‘fn1’:
parity_l8.i:12:13: error: ‘d[0]’ is used uninitialized in this function
[-Werror=uninitialized]
while (d[0]) {
~^~~
compilation terminated due to -Wfatal-errors.
cc1: all warnings being treated as errors
% clang -c -Wall -Wextra -O3 parity_l8.i -Werror -Wfatal-errors
% clang --analyze -c -Wall -Wextra -O3 parity_l8.i -Werror -Wfatal-errors
parity_l8.i:4:14: warning: Value stored to 'n' during its initialization is
never read
int e = 0, n = a;
^ ~
parity_l8.i:12:12: warning: Branch condition evaluates to a garbage value
while (d[0]) {
^~~~
2 warnings generated.
