gcc/testsuite/gcc.c-torture/execute/bitfld-1.c

   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 }