Are stack variables aligned by the GCC __attribute__((aligned(x)))?

i have the following code:

#include <stdio.h>

int
main(void)
{
        float a[4] __attribute__((aligned(0x1000))) = {1.0, 2.0, 3.0, 4.0};
        printf("%p %p %p %p\n", &a[0], &a[1], &a[2], &a[3]);
}

And i have the following output:

0x7fffbfcd2da0 0x7fffbfcd2da4 0x7fffbfcd2da8 0x7fffbfcd2dac

Why the address of a[0] is not a multiple of 0x1000?

What exactly __attribute__((aligned(x))) does? I misunderstood this explanation?

I'm using gcc 4.1.2.