/* Duff's device is legal C; test to make sure the compiler doesn't complain about it. Jason Thorpe Derived from Tom Duff's original usenet message about the device. */ /* { dg-do run } */ /* { dg-options "-O2" } */ extern void abort (void); extern void exit (int); typedef __SIZE_TYPE__ size_t; extern int memcmp (const void *, const void *, size_t); void duffcpy (char *dst, const char *src, unsigned long size) { unsigned long n = (size + 7) / 8; switch (size % 8) { case 0: do { *dst++ = *src++; case 7: *dst++ = *src++; case 6: *dst++ = *src++; case 5: *dst++ = *src++; case 4: *dst++ = *src++; case 3: *dst++ = *src++; case 2: *dst++ = *src++; case 1: *dst++ = *src++; } while (--n > 0); } } const char testpat[] = "The quick brown fox jumped over the lazy dog."; int main() { char buf[64]; duffcpy (buf, testpat, sizeof (testpat)); if (memcmp (buf, testpat, sizeof (testpat)) != 0) abort (); exit (0); }