Thread: vector resizing

I thought vectors were supposed to resize themselves. But this crashes on my compiler:

Code:

#include <vector>

int main(void) {
    std::vector<int> v;

    for(int x = 0; x < 10; x ++) {
        v[x] = x;
    }

    return 0;
}

But this doesn't:

Code:

#include <vector>

int main(void) {
    std::vector<int> v(10);

    for(int x = 0; x < 10; x ++) {
        v[x] = x;
    }

    return 0;
}

What's happening here?