lkml.org 
[lkml]   [2001]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: bug in redhat gcc 2.96
This bug is fixed in gcc-2.96-82 and higher, as per
http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=37054. I've posted
gcc-2.96-84.src.rpm at your enterprise ftp folder.

--jeremy


Jim Wright wrote:
>
> We believe we have found a bug in gcc. We have been trying to track
> down why the .../drivers/scsi/sym53c8xx.c driver oopses with a divide
> by zero when initializing at line 5265, which reads:
>
> period = (4 * div_10M[0] + np->clock_khz - 1) / np->clock_khz;
>
> We believe the bug is that gcc is generating incorrect code for this:
>
> if (f1 < 55000) f1 = 40000;
> else f1 = 80000;
>
> Here is the test code to demonstrate this:
>
> % cat bug.c
> int main (int argc, char *argv[])
> {
> unsigned f1;
>
> f1 = (unsigned)argc;
>
> if (f1 < 5) {
> f1 = 4;
> } else {
> f1 = 8;
> }
> exit (f1);
> }
>
> And here are commands to exhibit the problem.
>
> % for i in 0 1 2 3 4 5 6 ; do ln bug.c bug$i.c ; done
> % for i in 0 1 2 3 4 5 6 ; do gcc -save-temps -O$i -o bug$i bug$i.c ; done
> % for i in 0 1 2 3 4 5 6 ; do ./bug$i 1 2 ; echo $? ; done
> % for i in 0 1 2 3 4 5 6 ; do ./bug$i 1 2 3 4 5 6 7 ; echo $? ; done
>
> The level 0 optimization assembly code appears correct. For level 1 and
> above, the compiler emits a long-subtract-with-borrow statement which
> leaves EAX either 0 filled or 1 filled, based on the carry flag.
>
> As this is with Red Hat's version of gcc, I'm not sending
> this to the gcc folks. RPMs of gcc with this problem
> include gcc-2.96-69 and gcc-2.96-81. This has been logged
> as http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=39764.
> Any suggestions for a way to cope with this? We have a
> customer who's system fails due to this.
>
> --
> Jim Wright Software Engineer Penguin Computing
> jwright@penguincomputing.com v:415-358-2609 f:415-358-2646
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:52    [W:0.066 / U:0.508 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site