1  /* 
       2   This test checks promotion of bitfields.  Bitfields should be promoted
       3   very much like chars and shorts: 
       4  
       5   Bitfields (signed or unsigned) should be promoted to signed int if their
       6   value will fit in a signed int, otherwise to an unsigned int if their 
       7   value will fit in an unsigned int, otherwise we don't promote them (ANSI/ISO
       8   does not specify the behavior of bitfields larger than an unsigned int).
       9  
      10   We test the behavior by subtracting two from the promoted value: this will
      11   result in a negitive value for signed types, a positive value for unsigned
      12   types.  This test (of course) assumes that the compiler is correctly 
      13   implementing signed and unsigned arithmetic.
      14   */
      15  
      16  struct X {
      17    unsigned int	     u3:3;
      18      signed long int  s31:31;
      19      signed long int  s32:32;
      20    unsigned long int  u31:31;
      21    unsigned long int  u32:32;
      22    unsigned long long ull3 :3;
      23    unsigned long long ull35:35;
      24    unsigned u15:15;
      25  };
      26  
      27  struct X x;
      28  
      29  main ()
      30  {
      31    if ((x.u3 - 2) >= 0)		/* promoted value should be signed */
      32      abort ();
      33  
      34    if ((x.s31 - 2) >= 0)		/* promoted value should be signed */
      35      abort ();
      36  
      37    if ((x.s32 - 2) >= 0)		/* promoted value should be signed */
      38      abort ();
      39  
      40    if ((x.u15 - 2) >= 0)		/* promoted value should be signed */
      41      abort ();
      42  
      43    /* Conditionalize check on whether integers are 4 bytes or larger, i.e.
      44       larger than a 31 bit bitfield.  */
      45    if (sizeof (int) >= 4)
      46      {
      47        if ((x.u31 - 2) >= 0)	/* promoted value should be signed */
      48  	abort ();
      49      }
      50    else
      51      {
      52        if ((x.u31 - 2) < 0)	/* promoted value should be UNsigned */
      53  	abort ();
      54      }
      55  
      56    if ((x.u32 - 2) < 0)		/* promoted value should be UNsigned */
      57      abort ();
      58  
      59    if ((x.ull3 - 2) >= 0)	/* promoted value should be signed */
      60      abort ();
      61  
      62    if ((x.ull35 - 2) < 0)	/* promoted value should be UNsigned */
      63      abort ();
      64  
      65    exit (0);
      66  }