unused-2.c

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

/* Copyright (C) 2000  Free Software Foundation.

   by Alexandre Oliva  <[e-mail]>  */

/* { dg-do compile } */
/* { dg-options "-O2 -finline-functions -Wunused -Wreturn-type" } */

static void
foo ()
{
  skip_it: ; /* { dg-warning "defined but not used" "unused label warning" } */
}

void
bar ()
{
  foo ();
}