Re^4: A Net::FTP and DBM::Deep clash

Hello, this is Joseph Huckaby, author of DBM::Deep. I was able to reproduce the crash in WinXP ActivePerl 5.8.7 + Net::FTP WITHOUT using DBM::Deep at all. All you have to do is:

#!/usr/bin/perl

use strict;
use warnings;
use Net::FTP;

$| = 1;

my $words_all = {
  kosovar => [qw(33 35 28 44)],
};

my %pack;
  
while (my ($word, $url_list) = each %{$words_all}){
  my $url_list_packed = pack 'v*', @{$url_list};
  $pack{$word} = $url_list_packed;
}

warn "calling isa on kosovar\n";
warn UNIVERSAL::isa($pack{'kosovar'}, "ARRAY") . "\n";

warn "you should never see this, because it crashed.\n";
[download]

The crash occurs when you call isa() on the kosovar key in the hash. This should be a perfectly valid call, which should return true. Instead, it crashes the VM. I conclude that this is probably a bug in Net::FTP, or ActiveState Perl on WinXP.

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Re^5: A Net::FTP and DBM::Deep clash by BrowserUk (Patriarch) on Oct 13, 2005 at 06:01 UTC
Then you have my apologies for casting errant aspersions. It certainly looked like a DBM::Deep bug. Very nice module BTW. This should be a perfectly valid call, which should return true. Actually not. `pack 'v', 33, 35, 28, 44;` is just a scalar containing some binary data. Still, it shouldn't crash when you pass it to `UNIVERSAL::isa()` The problem isn't directly the fault of Net::FTP either, though it may be related, as the bug also manifests in the presence of IO::Socket. This also crashes, and again, only when a value of 33 is packed and passed: `P:\test>p1 perl> use IO::Socket;; perl> print $_, UNIVERSAL::isa( pack( 'v', $_ ), 'SCALAR' ) for 0 .. +33;; 0 1 2 [...] 30 31 32 P:\test>rem It segfaulted.` [download] So the bug appears to be that UNIVERAL::isa() attempts to use the passed value as a reference, and dies if you pass it binary data that isn't--but only if it is/contains "dirty knee", 33! And only if some networking module is loaded? Beyond that is the province of the internals guys. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". The "good enough" maybe good enough for the now, and perfection maybe unobtainable, but that should not preclude us from striving for perfection, when time, circumstance or desire allow.	[reply] [d/l] [select]
Re^5: A Net::FTP and DBM::Deep clash by wfsp (Abbot) on Oct 13, 2005 at 06:15 UTC
Hi Joseph, Many thanks for your response and many apologies for jumping to the wrong conclusion. John Sharpe	[reply]