gcc/testsuite/gcc.dg/duff-3.c

   1 /* Duff's device is legal C; test to make sure the compiler
   2    doesn't complain about it.
   3
   4    Jason Thorpe <thorpej@wasabisystems.com>
   5    Derived from Tom Duff's original usenet message about the device.  */
   6
   7 /* { dg-do run } */
   8 /* { dg-options "-O2" } */
   9
  10 extern void abort (void);
  11 extern void exit (int);
  12
  13 typedef __SIZE_TYPE__ size_t;
  14 extern int memcmp (const void *, const void *, size_t);
  15
  16 void
  17 duffcpy (char *dst, const char *src, unsigned long size)
  18 {
  19   unsigned long n = (size + 7) / 8;
  20
  21   switch (size % 8)
  22     {
  23     case 0:     do {    *dst++ = *src++;
  24     case 7:             *dst++ = *src++;
  25     case 6:             *dst++ = *src++;
  26     case 5:             *dst++ = *src++;
  27     case 4:             *dst++ = *src++;
  28     case 3:             *dst++ = *src++;
  29     case 2:             *dst++ = *src++;
  30     case 1:             *dst++ = *src++;
  31                 } while (--n > 0);
  32     }
  33 }
  34
  35 const char testpat[] = "The quick brown fox jumped over the lazy dog.";
  36
  37 int
  38 main()
  39 {
  40   char buf[64];
  41
  42   duffcpy (buf, testpat, sizeof (testpat));
  43   if (memcmp (buf, testpat, sizeof (testpat)) != 0)
  44     abort ();
  45
  46   exit (0);
  47 }