pointer and array in struct

array_address.c

#include <stdio.h>
struct str{
    int len;
    char s[0];
};
 
struct foo {
    struct str *a;
};
 
int main(int argc, char** argv) {
    struct foo f={0};
    if (f.a->s) { //won't crash
        printf( f.a->s); //will crash
    }
    return 0;
}