https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85778
Bug ID: 85778
Summary: unexpected results with -O2, wrong code?
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: doko at gcc dot gnu.org
Target Milestone: ---
seen with GCC 5 and all newer version. Is this wrong-code?
$ cat testcase.c
#include <stdio.h>
#include <sys/stat.h>
#define PRINT \
if (foo == NULL) \
printf("foo in func() is %p, NULL (expected)\n", foo); \
else \
printf("foo in func() is %p, not NULL (NOT EXPECTED!)\n", foo);
void func(const char *foo) {
struct stat stat_buf;
PRINT;
stat(foo, &stat_buf);
PRINT;
}
int main() {
const char *foo = NULL;
struct stat stat_buf;
func(NULL);
PRINT;
stat(foo, &stat_buf);
PRINT;
return 0;
}
$ gcc -O0 testcase.c && ./a.out
foo in func() is (nil), NULL (expected)
foo in func() is (nil), NULL (expected)
foo in func() is (nil), NULL (expected)
foo in func() is (nil), NULL (expected)
$ gcc -O2 testcase.c && ./a.out
foo in func() is (nil), NULL (expected)
foo in func() is (nil), not NULL (NOT EXPECTED!)
foo in func() is (nil), NULL (expected)
foo in func() is (nil), NULL (expected)
