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From Joe Orton <jor...@redhat.com>
Subject Re: [PATCH] infinite loop with xlc -O2 and APR_BUCKET_REMOVE
Date Sat, 18 Aug 2007 13:11:36 GMT
On Wed, Aug 15, 2007 at 02:40:04PM -0400, Greg Ames wrote:
...
> the loop happens with our normal xlc -O2 optimization.  turning off
> optimization makes the problem go away.  when walking thru the optimized
> code with dbx, it looks like neither the APR_BRIGADE_EMPTY nor the
> APR_BRIGADE_FIRST are accessing the bb head pointers in memory after the
> loop is initialized.  at first I was convinced this was an xlc optimizer
> bug, but Googling did not reveal any known problems like this.

Nice.  There was discussion about a pointer aliasing issue in this code 
before, though I can't find a reference.  I think the issue you describe 
matches that of a pointer aliasing bug, anyway; if xlc has an equivalent 
of gcc's -fno-strict-aliasing that could be used to perhaps confirm it?
joe


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