gcc/testsuite/gcc.dg/duff-1.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 PR 3846.  */
   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   switch (size & 3)
  20     {
  21     for (;;)
  22       {
  23         *dst++ = *src++;
  24     case 3:
  25         *dst++ = *src++;
  26     case 2:
  27         *dst++ = *src++;
  28     case 1:
  29         *dst++ = *src++;
  30     case 0:
  31         if (size <= 3)
  32           break;
  33         size -= 4;
  34       }
  35     }
  36 }
  37
  38 const char testpat[] = "The quick brown fox jumped over the lazy dog.";
  39
  40 int
  41 main()
  42 {
  43   char buf[64];
  44
  45   duffcpy (buf, testpat, sizeof (testpat));
  46   if (memcmp (buf, testpat, sizeof (testpat)) != 0)
  47     abort ();
  48
  49   exit (0);
  50 }