[Bug c/59564] New: False positive array -Warray-bounds check with -O2

[egor_suvorov at mail dot ru]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59564

            Bug ID: 59564
           Summary: False positive array -Warray-bounds check with -O2
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: egor_suvorov at mail dot ru

Created attachment 31482
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31482&action=edit
Output of gcc with '-v -save-temps'

Here's a full code:

int arr[1];
int n = 0;

int main() {
  if (n <= 0) n = 0;
  arr[n] = 0;
  if (n <= 0) n = 0;
  return 0;
}

If you compile this code with '-O2 -Warray-bounds', gcc produces warning, which
is obviously incorrect. You can also change inequality checks to >= and you'll
get another similar warning.

I've checked it on mingw 4.8.1, mingw 4.7.2 and on debian gcc 4.7.2 - works
everywhere. You can also save this file as .cpp and compile with g++ - bug
persists.