a;
main() {
a = 0x7D393Ep69;
printf(a);
}
How do I ensure it is a wrong code bug ?
This is definitely not a compiler bug, but rather undefined behavior, since an integer is being cast to const char * then dereferenced by printf().
Your C-Reduce interestingness test needs to include undefined behavior checks, in practice it is often sufficient to run ASan, UBSan, and also to look for some printf-related compiler warnings. These tools, together, aren't 100% reliable but they're often good enough.
John