gcc/testsuite/gcc.dg/torture/pr37868.c

/* { dg-do run } */
/* { dg-options "-fno-strict-aliasing" } */
/* { dg-skip-if "unaligned access" { arc*-*-* epiphany-*-* nds32*-*-* sparc*-*-* sh*-*-* tic6x-*-* } } */

extern void abort (void);
#if (__SIZEOF_INT__ <= 2)
struct X {
  unsigned char pad : 4;
  unsigned int a : 16;
  unsigned int b : 8;
  unsigned int c : 6;
} __attribute__((packed));
#else
struct X {
  unsigned char pad : 4;
  unsigned int a : 32;
  unsigned int b : 24;
  unsigned int c : 6;
} __attribute__((packed));

#endif


int main (void)
{
  struct X x;
  unsigned int bad_bits;

  x.pad = -1;
  x.a = -1;
  x.b = -1;
  x.c = -1;

  bad_bits = ((unsigned int)-1) ^ *(1+(unsigned int *) &x);
  if (bad_bits != 0)
    abort ();
  return 0;
}