[perl #129177] No autovivification, for loop aliasing,

On Fri Sep 02 13:54:24 2016, leszek@dubiel.pl wrote:
> 
> This is a bug report for perl from leszek@dubiel.pl,
> generated with the help of perlbug 1.40 running under perl 5.20.2.
> 
> 
> -----------------------------------------------------------------
> [Please describe your issue here]
> 
> 
> This is after the discussion here:
> http://www.perlmonks.org/?node_id=1171041
> 
> Data structure:
> 
> my $n = {
>      a => [1, 2 ],
>      b => [3, 4],
> };
> 
> This throws exception:
> 
> @{$$n{'x'}};
> 
> And this doesn't:
> 
> for my $e (@{$$n{'x'}}) {
> }
> 
> Maybe it is somehow connected with autovivification.
> 
> 

Perhaps it does -- but since you are referencing the 'autovivification' module from CPAN (http://search.cpan.org/~vpit/autovivification-0.16/lib/autovivification.pm#BUGS), you first have to rule out the possibility that this is a bug in that library.  Reports sent to rt.perl.org should be concerned only with the Perl 5 core distribution.  The 'autovivification' library is not part of the core distribution.

Please report this problem first to the CPAN maintainer of 'autovivification' via sending mail to:

bug-autovivification [at] rt.cpan.org

If the discussion there discloses a bug in the Perl 5 core distribution, then we can open a new ticket here or re-open this one.

> 
> 
> Here is program:
> 
> #!/usr/bin/perl -CSDA
> 
> use utf8;
> use strict;
> use warnings;
> no warnings qw{uninitialized numeric};
> no autovivification; #  qw{fetch exists delete store};
> use Data::Dumper;
> 

Note for when you report this problem at rt.cpan.org:  Much of what you have above is superfluous for the purpose of filing a bug report.  You can and should eliminate the '-CSDA'; the 'use utf8'; and the 'no warnings qw{uninitialized numeric}'.  Strip down the code sample to the minimum code that reproduces the problematic behavior.


> print "\n\ninitialize data structures, no autovivification\n";
> my $n = {
>      a => [1, 2 ],
>      b => [3, 4],
> };
> $$n{'x'}{'y'}{'z'} and die;
> $$n{'x'}{'y'}[0] and die;
> $$n{'x'}{'y'} and die;
> $$n{'x'} and die;
> print "so far, so good, no 'x' autovivified:\n";
> print Dumper $n;
> 
> # "Can't use an undefined value as an ARRAY reference":
> # @{$$n{'x'}} and die;
> 
> print "\n\nnow the same but in loop:\n";
> for my $e (@{$$n{'x'}}) {
> }
> print "why 'x' autovivified?\n";
> print Dumper $n;
> 
> print "\n\nnow the same but in loop:\n";
> for my $e (@{[ $$n{'y'} ]}) {
> }
> print "why 'y' NOT autovivified?\n";
> print Dumper $n;

Thank you very much.

-- 
James E Keenan (jkeenan@cpan.org)

---
via perlbug:  queue: perl5 status: new
https://rt.perl.org/Ticket/Display.html?id=129177

• [perl #129177] No autovivification, for loop aliasing, by Father Chrysostomos via RT
• Re: [perl #129177] No autovivification, for loop aliasing, by Aristotle Pagaltzis
• Re: [perl #129177] No autovivification, for loop aliasing, by Leszek Dubiel
• [perl #129177] No autovivification, for loop aliasing, by James E Keenan via RT
• [perl #129177] No autovivification, for loop aliasing, by James E Keenan via RT
• [perl #129177] No autovivification, for loop aliasing, by James E Keenan via RT
• [perl #129177] No autovivification, for loop aliasing, by Leszek Dubiel