Address of address of a variable

I was experimenting the behaviors of pointer in C. I wrote the following program:

#include <stdio.h>
main(){
    int a = 1;
    printf("%p\n", &&a);
}

I knew that this program would give error. Because an address of address would be ambiguous and this would become extremely recursive. But when I tried to compile the program, it gave an error which I couldn't understand.

error: label ‘a’ used but not defined

printf("%p\n", &&a);

What does it mean by label ‘a’ used but not defined?