GCC left shift overflow

The following little program is very awkward using GCC version 4.2.1 (Apple Inc. build 5664) on a Mac.

#include <stdio.h>

int main(){
        int x = 1 << 32;
        int y = 32;
        int z = 1 << y;
        printf("x:%d, z: %d\n", x, z);
}

The result is x:0, z: 1.
Any idea why the values of x and z are different?
Thanks a lot.