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[perl #106864] refcount for anonymous sub is 2 instead of 1

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From:
Father Chrysostomos via RT
Date:
December 24, 2011 18:55
Subject:
[perl #106864] refcount for anonymous sub is 2 instead of 1
Message ID:
rt-3.6.HEAD-14510-1324781703-263.106864-15-0@perl.org
On Sat Dec 24 15:55:23 2011, ikegami@adaelis.com wrote:
> 2011/12/22 Olivier Mengu� <perlbug-followup@perl.org>
> 
> > # New Ticket Created by  Olivier Mengu�
> > # Please include the string:  [perl #106864]
> > # in the subject line of all future correspondence about this issue.
> > # <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=106864 >
> >
> >
> > This is a bug report for perl from dolmen@cpan.org,
> > generated with the help of perlbug 1.39 running under perl 5.10.1.
> >
> >
> > -----------------------------------------------------------------
> >
> >
> > With the following expression:
> >
> >    my $x = sub { };
> >
> > the refcount of $x is 2 instead of 1.
> > There is no such problem if the sub, instead of behind a simple sub,
> > is a closure.
> >
> 
> >perl -MDevel::Peek -e"for (1..3) { push @a, sub {}; } Dump($a[0]);"
> SV = IV(0x57b650) at 0x57b654
>   REFCNT = 1
>   FLAGS = (ROK)
>   RV = 0x57b624
>   SV = PVCV(0x4a9dd4) at 0x57b624
>     REFCNT = 4
>     FLAGS = (PADMY,ANON,WEAKOUTSIDE,CVGV_RC)
>     COMP_STASH = 0x57b444       "main"
>     START = 0x4d2cb8 ===> 0
>     ROOT = 0x4d2c9c
>     GVGV::GV = 0x4a961c "main" :: "__ANON__"
>     FILE = "-e"
>     DEPTH = 0
>     FLAGS = 0x490
>     OUTSIDE_SEQ = 96
>     PADLIST = 0x4a954c
>     PADNAME = 0x4a960c(0x4a12f4) PAD = 0x4a98fc(0x4a0c64)
>     OUTSIDE = 0x57b6b4 (MAIN)
> 
> 4, one for each element in @a, and one to the sub alive until sub {} needs
> it next.
> 
> With closures, there would be 4 CVs with one reference each instead of
1 CV
> with 4 reference.

I think this is a bug, in that mentioning a variable in a sub shouldn’t
change whether $x has the only reference after ‘$x = sub{}’.

It also causes the blessing bug in ticket #3306.

-- 

Father Chrysostomos


---
via perlbug:  queue: perl5 status: rejected
https://rt.perl.org:443/rt3/Ticket/Display.html?id=106864

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