lapointd has asked for the wisdom of the Perl Monks concerning the following question:

I've frequently run into the following problem. I've searched Perlmonks, and seen a few similar situations , but I didn't see a clear answer. It sounds like it is a bug in Perl? When passing an array as a reference to a subroutine, like this: 
subroutine(\@list)

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and using it internal to the subroutine, like this: 
$count=$#(@$listref);

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I get the folling error message, only in debug mode: 
"Bizarre copy of ARRAY in leave at..."

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The code works fine, and does the right thing, it just fails in debug mode. The inelegant work-around is to do an intermediate step: 
my @local_array=@$list;
my $count=$#local_array;

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Any ideas on this problem?

Replies are listed 'Best First'.
Re: Bizarre copy of ARRAY in leave at...
by BrowserUk (Patriarch) on Jan 19, 2004 at 17:36 UTC

    Actually, the problem is your syntax is bizarre :)

    To get the highest index of an array from a reference to it the syntax should be $#{ $aref } not $#{ @$aref } which you have. The fact that your code works silently, is probably a bug:) 

    #! perl -slw
use strict;

sub get_size{
       my ($aref ) = @_;
       return $#{@$aref};
}

my @a = ( 1..10 );

print get_size( \@a );

__END__
P:\test>322384
9

P:\test>perl -d 322384.pl

Loading DB routines from perl5db.pl version 1.22
Editor support available.

Enter h or `h h' for help, or `perldoc perldebug' for more help.

main::(322384.pl:9):    my @a = ( 1..10 );
  DB<1> s
main::(322384.pl:11):   print get_size( \@a );
  DB<1> s
main::get_size(322384.pl:5):            my ($aref ) = @_;
  DB<1> s
main::get_size(322384.pl:6):            return $#{@$aref};
  DB<1> s
main::get_size(322384.pl:6):            return $#{@$aref};
  DB<1> s
Bizarre copy of ARRAY in leave at 322384.pl line 6.
        main::get_size('ARRAY(0x19ede94)') called at 322384.pl line 11
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.
  DB<1> Config::DESTROY(c:/Perl/lib/Config.pm:1198):
1198:   sub DESTROY { }
  DB<1> q


#### change $#{@$aref} to $#{ $aref }


P:\test>322384
9

P:\test>perl -d 322384.pl

Loading DB routines from perl5db.pl version 1.22
Editor support available.

Enter h or `h h' for help, or `perldoc perldebug' for more help.

main::(322384.pl:9):    my @a = ( 1..10 );
  DB<1> s
main::(322384.pl:11):   print get_size( \@a );
  DB<1> s
main::get_size(322384.pl:5):            my ($aref ) = @_;
  DB<1> s
main::get_size(322384.pl:6):            return $#{$aref};
  DB<1> s
main::get_size(322384.pl:6):            return $#{$aref};
  DB<1> s
9
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.
  DB<1> q

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    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail
    Timing (and a little luck) are everything!
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      ...not $#{ @$aref } which you have.

      But he doesn't have {}, he has (), as in 

      $round = [ 1 .. 10];
die $#( $round );
__END__
Missing comma after first argument to die function at - line 2, near "
+);"
Execution of - aborted due to compilation errors.

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Re: Bizarre copy of ARRAY in leave at...
by Zaxo (Archbishop) on Jan 20, 2004 at 06:45 UTC

    Along the same lines as BrowserUK points out, my $last_index = $#$listref; works fine.

    After Compline,
    Zaxo

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Re: Bizarre copy of ARRAY in leave at...
by Abigail-II (Bishop) on Jan 19, 2004 at 16:39 UTC
    It's probably a bug in Perl, but you haven't told us the entire story. Where are $listref and $list coming from? Do you have a small self-contained program that exhibits this behaviour?

    Abigail

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Re: Bizarre copy of ARRAY in leave at...
by ysth (Canon) on Jan 20, 2004 at 07:45 UTC
    Please expunge the word "listref" from your vocabulary. There is no such thing, and using the term it will only lead you into confusion. A list is not an array, and you can only take a reference to an array.
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