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Re: Padlist NULL pointer?

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From:
Marc Lehmann
Date:
October 30, 2013 13:42
Subject:
Re: Padlist NULL pointer?
Message ID:
20131030134243.GA4317@schmorp.de
On Wed, Oct 30, 2013 at 10:39:35AM +0000, Zefram <zefram@fysh.org> wrote:
> >What I've noticed is that depth is 8, and svp[7] is 0x0.  So, unsurprisingly, 
> >this crashes.  But then the question is, why is it allocated (within 
> >PadlistMAX(padlist) ), but NULL?
> 
> The representation of pads changed substantially in 5.18.  Chances are
> that the nullness is an interaction between the new pad system and
> Coro's dynamic stack swapping, for which Coro will need an update.

I can't imagine this to be the case, i.e. Coro somehow introducing a null
pointer anywhere.

I also see in the code of Perl_pad_push that it does handle 0 pad
pointers, as long as they are for pads not in use, so something in Perl
(or a module that isn't Coro) seems to replace pointers by 0 somewhere.

> You'll need to apply a debugger to figure out exactly how you get to
> the crashing state, and how it differs from 5.16.

5.16 differs in that all pad pointers between 2 and max are != 0. It also
differs in that pad_push doesn't support 0 pointers, so some of the changes
in the pad system must have made this legal somewhere.

Since I don't really like blindly applying patches, does anybody in p5p
udnerstand where 0-pad pointers are introduced, and point me at it so I cna
understand what actually happens?

Being able to maintain coro myself would doubtlessly be good for everybody
:)

-- 
                The choice of a       Deliantra, the free code+content MORPG
      -----==-     _GNU_              http://www.deliantra.net
      ----==-- _       generation
      ---==---(_)__  __ ____  __      Marc Lehmann
      --==---/ / _ \/ // /\ \/ /      schmorp@schmorp.de
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