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[perl #134252] BBC: f23e1643 breaks Data::Alias and possiblySyntax::Keyword::Try

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From:
James E Keenan
Date:
July 2, 2019 03:02
Subject:
[perl #134252] BBC: f23e1643 breaks Data::Alias and possiblySyntax::Keyword::Try
Message ID:
rt-4.0.24-32286-1562036522-782.134252-75-0@perl.org
# New Ticket Created by  James E Keenan 
# Please include the string:  [perl #134252]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=134252 >


This was first reported to me off list by Carlos Guevara, based on his 
smoke testing rigs.


http://matrix.cpantesters.org/?dist=Data-Alias

http://matrix.cpantesters.org/?dist=Syntax-Keyword-Try

Carlos also reported that test(s) in the latter distro hung.  I can 
confirm that on FreeBSD-11, Syntax::Keyword::Try's test t/11loop.t hung 
indefinitely and had to be Ctrl-C-ed for smoking to proceed.  I was 
consequently not able to get a definitive bisection for that module.

On Linux I was able to bisect the problem with Data::Alias to:

#####
f23e164367e8b9494783181262bf4a1a16d26961 is the first bad commit
commit f23e164367e8b9494783181262bf4a1a16d26961
Author: David Mitchell <davem@iabyn.com>
Date:   Tue Jun 18 15:11:12 2019 +0100

Perl_list() tail-call optimise

The part of this function that scans the children of e.g.

@a = do { void; void; list }

applying list context only to the last child, tail call
optimise that call to list().

(See also a few commits later entitled "Perl_scalar()
tail-call optimise" for a discourse on setting PL_curcop
(in)correctly.)

:100644 100644 77dc177ec9bfd8c488d2a62aacaaaedc4f2658b7 
a30740f2a5a449b1644665331ba560cbc9c167ee M	op.c
#####

No further diagnose yet attempted.

Thank you very much.
Jim Keenan

perl perl perl


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