mayalias-1.c

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

/* Tests that the may_alias attribute works as expected.
   Author: Osku Salerma <[e-mail]> Apr 2002.  */
 
extern void abort(void);
extern void exit(int);

typedef short __attribute__((__may_alias__)) short_a;

int
main (void)
{
  int a = 0x12345678;
  short_a *b = (short_a*) &a;

  b[1] = 0;

  if (a == 0x12345678)
    abort();

  exit(0);
}