crash.c

#include <stdio.h>

struct str
{
	int len;
	char s[0];
};

struct foo
{
	struct str *a;
};

int main(void) {
	struct foo f = {0};
	printf("int:%d\n", sizeof(int));
	printf("char:%d\n", sizeof(char));
	printf("str:%d\n", sizeof(struct str));
	printf("foo:%d\n", sizeof(struct foo));
	if(f.a->s) {
		puts("====");
		printf("f.a:%d\n", (int)(f.a));
		printf("f.a->s:%d\n", (int)(f.a->s));
		printf("f.a->len:%d\n", (int)(&(f.a->len)));
		printf(f.a->s);		// crash
	}

	return;
}