1  /* Copyright 2002 Free Software Foundation, Inc.
       2  
       3     Tests correct signedness of operations on bitfields; in particular
       4     that integer promotions are done correctly, including the case when
       5     casts are present.
       6  
       7     The C front end was eliding the cast of an unsigned bitfield to
       8     unsigned as a no-op, when in fact it forces a conversion to a
       9     full-width unsigned int. (At the time of writing, the C++ front end
      10     has a different bug; it erroneously promotes the uncast unsigned
      11     bitfield to an unsigned int).
      12  
      13     Source: Neil Booth, 25 Jan 2002, based on PR 3325 (and 3326, which
      14     is a different manifestation of the same bug).
      15  */
      16  
      17  extern void abort ();
      18  
      19  int
      20  main(int argc, char *argv[])
      21  {
      22    struct x { signed int i : 7; unsigned int u : 7; } bit;
      23  
      24    unsigned int u;
      25    int i;
      26    unsigned int unsigned_result = -13U % 61;
      27    int signed_result = -13 % 61;
      28  
      29    bit.u = 61, u = 61; 
      30    bit.i = -13, i = -13;
      31  
      32    if (i % u != unsigned_result)
      33      abort ();
      34    if (i % (unsigned int) u != unsigned_result)
      35      abort ();
      36  
      37    /* Somewhat counter-intuitively, bit.u is promoted to an int, making
      38       the operands and result an int.  */
      39    if (i % bit.u != signed_result)
      40      abort ();
      41  
      42    if (bit.i % bit.u != signed_result)
      43      abort ();
      44  
      45    /* But with a cast to unsigned int, the unsigned int is promoted to
      46       itself as a no-op, and the operands and result are unsigned.  */
      47    if (i % (unsigned int) bit.u != unsigned_result)
      48      abort ();
      49  
      50    if (bit.i % (unsigned int) bit.u != unsigned_result)
      51      abort ();
      52  
      53    return 0;
      54  }