// Clause: 6.2.6.1 / 6.7.9 — _Bool is not an unsigned char; reading its indeterminate value is undefined behavior.
#include <stdio.h>
#include <stdbool.h>
int main(void){
    _Bool b;   // uninitialized
    if (b) {   // UB: use of indeterminate value
        puts("true");
    } else {
        puts("false");
    }
    return 0;
}