[Bug c/42142] New: GCC 4.5 doesn't compile a certain quicksort implementation correctly when optimizing with -O1 or higher

[maister at archlinux dot us]

I have a reproducible test case which shows that GCC 4.5 (20091112) doesn't
compile a certain quicksort implementation correctly. It runs fine, but the
sorting is plain wrong when trying to optimize with -O1 or higher. There might
be something wrong with the quicksort implementation itself, but it compiles
and runs fine when not optimizing anything with GCC 4.5. It also runs, and
executes correctly on 4.3 and 4.4 with all optimizations applied.

The code in question is here:
http://pastebin.com/m270ad2a5


Output when compiling with
   gcc-4.5 -o qsort qsort.c -O

http://pastebin.com/m44c8f6f2


Output with
   gcc-4.5 -o qsort qsort.c

http://pastebin.com/m6ee486a0


Output with
   gcc-4.4 -o qsort qsort.c $CRAZYSTUFF_HERE

http://pastebin.com/m78d55249


-- 
           Summary: GCC 4.5 doesn't compile a certain quicksort
                    implementation correctly when optimizing with -O1 or
                    higher
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: maister at archlinux dot us
  GCC host triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42142