[Bug sanitizer/55679] new asan tests from r194458 fail on x86_64-apple-darwin10

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55679

--- Comment #16 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2012-12-16 18:23:24 UTC ---
(In reply to comments #12 and #13)
With -O1, the invalid tests c-c++-common/asan/global-overflow-1.c and
c-c++-common/asan/stack-overflow-1.c are optimized to a valid "return 0" as
shown by the following differences between the outputs of -dump-tree-optimized
with and without -fno-tree-fre:

--- stack-overflow-1.c.164t.optimized    2012-12-16 17:26:13.000000000 +0100
+++ stack-overflow-1.c.164t_f.optimized    2012-12-16 17:25:13.000000000 +0100
@@ -3,18 +3,14 @@

 main ()
 {
-  int res;
   char x[10];
   int ten.1;
-  char _4;

   <bb 2>:
   __builtin_memset (&x, 0, 10);
   ten.1_3 ={v} ten;
-  _4 = x[ten.1_3];
-  res_5 = (int) _4;
   x ={v} {CLOBBER};
-  return res_5;
+  return 0;

 }

So the problem for these two tests has nothing to do with asan. Note that they
regress cleanly if I add '-fno-tree-fre -fno-tree-pre' to '-fno-builtin-memset'
in the dg-options. The optimization is also defeated If I add a line such as

  x[1] = 1;

Although I doubt this behavior is a bug, I'll open a new PR for it tomorrow
unless there is some objection.