Messages in this thread | | | Date | Wed, 09 May 2001 11:01:18 -0400 | From | Jeremy Hogan <> | Subject | Re: bug in redhat gcc 2.96 |
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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/
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