label-lineno-1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

/* Ensure that diagnostics for labels appear on the correct lineno.
   by Kaveh R. Ghazi <[e-mail]> 8/23/2000.  */

void
foo(int i)
{
 my_label:

  i++;

 my_label: /* { dg-error "duplicate label" "label lineno" } */

  i++;
}