Error: Label used but not defined when using && operator [closed]

Answer 1

Here && is the GNU C label address operator.

http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html

int *q = &&i;

i must be a label. You have no label i in your program.

Example of a label:

int main(void)
{
    i:
    (void) 0;

     int i = 0;
     int *p = &i;
     int *q = &&i;
     return 0;
}

I added the (void) 0; statement as labels in C can only put before statements and not before declarations.