gcc/testsuite/gcc.dg/Wrestrict-2.c

   1 /* Test to verify that the temporary doesn't trigger a bogus -Warray-bounds
   2    warning.  Distilled from libat_exchange_large_inplace in libatomic/gexch.c.
   3    { dg-do compile }
   4    { dg-options "-O2 -Wall" }  */
   5
   6 typedef typeof (sizeof 0) size_t;
   7
   8 extern void *memcpy (void*, const void*, size_t);
   9
  10 void libat_exchange_large_inplace (size_t n, void *mptr, void *vptr)
  11 {
  12   char temp[1024];
  13
  14   size_t i = 0;
  15
  16   for (i = 0; n >= 1024; i += 1024, n -= 1024)
  17     {
  18       memcpy (temp, mptr + i, 1024);
  19
  20       /* The memcpy call below results in the following:
  21          unsigned long ivtmp.7;
  22
  23          ivtmp.7_4 = (unsigned long) mptr_9(D);
  24          ...
  25          <bb 4>
  26          # ivtmp.7_22 = PHI <ivtmp.7_4(3), ivtmp.7_5(4)>
  27          ...
  28          _1 = (void *) ivtmp.7_22;
  29          ...
  30          memcpy (_1, _2, 1024);
  31
  32          Treating _1 as a pointer results in the bogus:
  33            warning: 'memcpy' offset 0 is out of the bounds [0, 8] of object 'ivtmp.7' with type 'long unsigned int' [-Warray-bounds]
  34            memcpy (mptr + i, vptr + i, 1024);
  35            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  36       */
  37       memcpy (mptr + i, vptr + i, 1024);
  38
  39       memcpy (vptr + i, temp, 1024);
  40     }
  41 }