[Bug other/59384] New: Cilk Plus array notation with for loop after segfaults

[Bug other/59384] New: Cilk Plus array notation with for loop after segfaults

[nick.tomlinson at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384

            Bug ID: 59384
           Summary: Cilk Plus array notation with for loop after segfaults
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nick.tomlinson at arm dot com
                CC: bviyer at gcc dot gnu.org

Created attachment 31380
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31380&action=edit
Minimal reproducer

When I compile the attached file, GCC segfaults. This appears to be a result of
having a Cilk Plus array notation assignment followed by a for loop using the
array assigned to.

The attached file is a minimal (un-preprocessed to preserve comments; there are
no includes or preprocessor macros) reproducer. The comments include
observations about what triggers the bug, a stack trace from GCC, the output of
gcc -v, and the command line used to compile it.

[Bug other/59384] Cilk Plus array notation with for loop after segfaults

[bviyer at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384

--- Comment #1 from Balaji V. Iyer <bviyer at gmail dot com> ---
Hi Nick,
     I am sorry for taking a while to get back to you. As you can tell from
gcc-patches mailing list, we are actively pursuing to try and push Cilk
Plus into trunk. We have submitted a updated patch for _Cilk_for for review
for trunk in this thread (
http://gcc.gnu.org/ml/gcc-patches/2014-01/msg00235.html).

I looked at this bug and it looks like this bug does not appear if you use
_Cilk_for implementation in the thread mentioned above.

Thanks,

Balaji V. Iyer.

PS. The code snippet could have a race-condition. I think if you switch the
for and _Cilk_for the race might go away.


On Mon, Dec 16, 2013 at 6:09 AM, nick.tomlinson at arm dot com <
gcc-bugzilla@gcc.gnu.org> wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384
>
> Nick Tomlinson <nick.tomlinson at arm dot com> changed:
>
>            What    |Removed                     |Added
>
> ----------------------------------------------------------------------------
>              Target|                            |x86_64
>                Host|                            |x86_64
>
> --
> You are receiving this mail because:
> You are on the CC list for the bug.
>

[Bug other/59384] Cilk Plus array notation with for loop after segfaults

[nick.tomlinson at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384

--- Comment #2 from Nick Tomlinson <nick.tomlinson at arm dot com> ---
I tried that patch against the latest CilkPlus branch, but could not apply it.
I also tried building GCC 4.9 from trunk, but could not use cilk_for. Please
could you let me know if there is a branch that supports both cilk_for and
array notation?

Thanks

[Bug other/59384] Cilk Plus array notation with for loop after segfaults

[bviyer at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384

Balaji V. Iyer <bviyer at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bviyer at gmail dot com

--- Comment #3 from Balaji V. Iyer <bviyer at gmail dot com> ---
Try this patch and the trunk revision mentioned in the thread:
http://gcc.gnu.org/ml/gcc-patches/2014-01/msg01170.html

[Bug other/59384] Cilk Plus array notation with for loop after segfaults

[nick.tomlinson at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384

--- Comment #4 from Nick Tomlinson <nick.tomlinson at arm dot com> ---
Created attachment 31944
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31944&action=edit
Example that is broken when the suggested patch is used.

[Bug other/59384] Cilk Plus array notation with for loop after segfaults

[nick.tomlinson at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59384

--- Comment #5 from Nick Tomlinson <nick.tomlinson at arm dot com> ---
Hello

I tried the new patch against the suggested revision (patch and revision from
http://gcc.gnu.org/ml/gcc-patches/2014-01/msg01170.html). While I was able to
patch and build GCC, I get an incorrect warning from GCC when using _Cilk_for,
and the resulting program segfaults. See the attached reproducer.

Thanks