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cunions

Why is the output 0 2 all the time when it should be garbage?

#include<stdio.h>
int main()
{
    union a
    {
        int i;
        char ch[2];
    };  
    union a z = {512};
    printf("%d %d",z.ch[0],z.ch[1]);
    return 0;
}

The output is: 0 2
Why is the output 0 2, when it should be some garbage value?

Solution

  • I am not sure why you expect the compiler to generate garbage for you, when you have just told it to initialize to i to 512. The least two significant bytes of 512 are 0 and 2.

    Implementation-specific behavior is not the same as garbage.