[Bug c/37745] New: Segmentation Fault Exception with -O and signed array index

[Bug c/37745] New: Segmentation Fault Exception with -O and signed array index

[gcc at jme dot de]

The following code produces a segmentation fault when compiled with -O.
Environment is GCC V4.2.2 (also tested with 4.1.2) on AVR32 Linux target.
Cross compiled on Cygwin.
With GCC V3.4.4 on Cygwin Target it works correct.
Even when I insert a printf("."); between the if and the for the code works.

static const unsigned aArr[] = {31,28,31};

unsigned Bla(unsigned u8)
{
    unsigned u32;
    int i,m;

    u32=0;
    m=u8;
    if (m!=0) m--;
    //printf(".");
    for (i=0; i<m; i++) u32+=aArr[i];

    return u32;
}

int main()
{
    Bla(1);
    return 0;
}


-- 
           Summary: Segmentation Fault Exception with -O and signed array
                    index
           Product: gcc
           Version: 4.2.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gcc at jme dot de
  GCC host triplet: Cygwin
GCC target triplet: AVR32 Linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37745

[Bug c/37745] Segmentation Fault Exception with -O and signed array index

[joseph at codesourcery dot com]

------- Comment #1 from joseph at codesourcery dot com  2008-10-06 11:58 -------
Subject: Re:   New: Segmentation Fault Exception with -O and
 signed array index

On Mon, 6 Oct 2008, gcc at jme dot de wrote:

> The following code produces a segmentation fault when compiled with -O.
> Environment is GCC V4.2.2 (also tested with 4.1.2) on AVR32 Linux target.

FSF GCC does not currently support AVR32, so you need to report this bug 
to whoever you got your modified compiler with that support from.  The bug 
reporting instructions at <http://gcc.gnu.org/bugs.html> say:

  What we do not want

...

     * Bugs in releases or snapshots of GCC not issued by the GNU
       Project. Report them to whoever provided you with the release


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37745

[Bug c/37745] Segmentation Fault Exception with -O and signed array index

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2008-10-06 15:59 -------
This will invoke

for (i=0; i<0; i++)

which invokes undefined behavior on signed integer overflow.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37745

[Bug c/37745] Segmentation Fault Exception with -O and signed array index

[gcc at jme dot de]

------- Comment #3 from gcc at jme dot de  2008-10-07 23:29 -------
Hi Joseph,

because the the problem occurs only with the compiler switch -O.
And the problem occurs not if I place a "printf("xx")" between
the two statements "if" and "for". Therefore, I thought it was a
more target independend optimization problem.

But now I'd checked this behaviour with i386 Linux 
(after installing g++ with "apt-get install g++")
-> "gcc-Version 4.0.3 (Ubuntu 4.0.3-1ubuntu5)"
and it works correct there.

I'll post the bug report to the AVR32 Linux site.

Sorry about wasting your time. This was my 1st bug post.
Next time I'll compare the behaviour on my Linux PC before posting.

Thanx,
    Joe.(In reply to comment #1)
> Subject: Re:   New: Segmentation Fault Exception with -O and
>  signed array index
> 
> On Mon, 6 Oct 2008, gcc at jme dot de wrote:
> 
> > The following code produces a segmentation fault when compiled with -O.
> > Environment is GCC V4.2.2 (also tested with 4.1.2) on AVR32 Linux target.
> 
> FSF GCC does not currently support AVR32, so you need to report this bug 
> to whoever you got your modified compiler with that support from.  The bug 
> reporting instructions at <http://gcc.gnu.org/bugs.html> say:
> 
>   What we do not want
> 
> ...
> 
>      * Bugs in releases or snapshots of GCC not issued by the GNU
>        Project. Report them to whoever provided you with the release
> 

(In reply to comment #1)
> Subject: Re:   New: Segmentation Fault Exception with -O and
>  signed array index
> 
> On Mon, 6 Oct 2008, gcc at jme dot de wrote:
> 
> > The following code produces a segmentation fault when compiled with -O.
> > Environment is GCC V4.2.2 (also tested with 4.1.2) on AVR32 Linux target.
> 
> FSF GCC does not currently support AVR32, so you need to report this bug 
> to whoever you got your modified compiler with that support from.  The bug 
> reporting instructions at <http://gcc.gnu.org/bugs.html> say:
> 
>   What we do not want
> 
> ...
> 
>      * Bugs in releases or snapshots of GCC not issued by the GNU
>        Project. Report them to whoever provided you with the release
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37745