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From John Dunlap <j...@lariat.co>
Subject Re: Random segmentation fault
Date Tue, 15 Sep 2015 21:03:05 GMT
First, let me thank you for your efforts! I doubt I could have come to the
bottom of that. Unfortunately, I have been unable to reproduce my problem
outside of a production environment and I can't risk pushing a version of
perl into production that I've built myself just to test that. As unhelpful
as it is, the best option for my customers, is to fall back to Debian
7(perl 5.14.2).

On Tue, Sep 15, 2015 at 4:58 PM, Michael Schout <mschout@gkg.net> wrote:

> Steve, John:
>
> I did a bisect today against perl git, using mod_perl 2.0.9 and apache
> 2.2.29 to find out where my two issues were caused.  It turns out that
> both of my problems, which were:
>
> - panic: attempt to copy freed scalar xxxx to yyyy
>
> and also
>
> - segmentation fault caused by a specific "return" statement
>
> Are *BOTH* caused by the following commit made to perl between 5.19.6
> and 5.19.7:
>
> > commit 437e3a7dac994ebace1195549170c81f474d9c20
> > Author: Matthew Horsfall <WolfSage@gmail.com>
> > Date:   Wed Dec 11 18:28:21 2013 -0500
> >
> >     Optimise out PUSHMARK/RETURN if return is the last statement in a
> sub.
> >
> >     This makes:
> >
> >       sub baz { return $cat; }
> >
> >     Behave like:
> >
> >       sub baz { $cat; }
> >
> >     Which is notably faster.
> ...
>
> I created a patch that reverses this (at least the change to op.c.. the
> other parts of the patch are just new macros, and a test case), then
> both of my problems are fixed.
>
> John:  I'd be interested to know if your problem is related.  If
> possible, can you build perl with the attached patch applied and see  if
> that fixes your segfault also?
>
> This seems to be mod_perl specific.  I have a very
> straightforward/minimal test case that causes the "panic" error under
> mod_perl, but the same code runs fine under the command line outside of
> mod_perl.
>
> Regards,
> Michael Schout
>



-- 
John Dunlap
*CTO | Lariat *

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*john@lariat.co <john@lariat.co>*

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