Improve the crasher stack-overflow command.

    // Unless there's a "big enough" buffer on the stack, gcc

    // doesn't bother inserting checks.

    char buf[8];

    // If we don't write something relatively unpredicatable

    // If we don't write something relatively unpredictable

    // into the buffer and then do something with it, gcc

    // optimizes everything away and just returns a constant.

    *(int*)(&buf[7]) = (uintptr_t) &buf[0];

    return *(int*)(&buf[0]);

}

static void* global = 0; // So GCC doesn't optimize the tail recursion out of overflow_stack.

__attribute__((noinline)) static void overflow_stack(void* p) {

    fprintf(stderr, "p = %p\n", p);

    void* buf[1];

    buf[0] = p;

    global = buf;

    overflow_stack(&buf);

}