How to turn "HASH(0x1234567)" into a real HASH

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

Monks,

While debugging some code that's printing "HASH(0x9999999)" to stdout, I'd like to be able to parse that out and convert it to a real Perl hash to be able to identify the hash's origin from looking at its contents.

I found I can peek into its data structure using the following:

   my ( $addr ) = 'HASH(0x9999999)' =~ /HASH\(0x(.*)\)/;
   $addr = hex $addr;
   my $hash_dump = pack 'L', $addr;
[download]

But unfortunately $hash_dump is not a HASH but just memory garbage.

How can I convert the address into a valid Perl HASH (or HASH ref)?

Comment on How to turn "HASH(0x1234567)" into a real HASH Select or Download Code

Replies are listed 'Best First'.
Re: How to turn "HASH(0x1234567)" into a real HASH by ikegami (Patriarch) on Oct 13, 2017 at 17:23 UTC
There's no telling if the hash still exists! If it doesn't, this could kill or corrupt your process. In other words, using this (or any other solution) is wrong! `use Carp qw( croak ); use Inline C => <<'__EOS__'; SV* _newRV(UV addr) { return newRV((SV)addr); } __EOS__ sub destringify_ref { $_[0] =~ /$([^()])$/ or croak("Invalid input"); return _newRV(hex($1)); } my %hash = ( a => 2, b => 3 ); my $ref = \%hash; $ref = "$ref"; $ref = destringify_ref($ref);` [download]	[reply] [d/l]
Re: How to turn "HASH(0x1234567)" into a real HASH by LanX (Saint) on Oct 13, 2017 at 16:49 UTC
It's not possible, to turn the stringified hash address into a reference. (At least not without meddling with internals and risking segfaults) My advice, keep the original reference. Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply]
Re^2: How to turn "HASH(0x1234567)" into a real HASH by rodd (Scribe) on Oct 13, 2017 at 17:00 UTC
Thanks, that did it! `my $hash = bless(\(0+hex $addr), "B::AV")->object_2svref;` [download]	[reply] [d/l]
Re^3: How to turn "HASH(0x1234567)" into a real HASH by LanX (Saint) on Oct 13, 2017 at 17:02 UTC
You are aware about the risks? Strings have no ref count! Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply]
Re: How to turn "HASH(0x1234567)" into a real HASH by haukex (Archbishop) on Oct 14, 2017 at 18:04 UTC
While debugging some code that's printing `"HASH(0x9999999)"` to stdout ikegami and LanX have given you some excellent answers. I am wondering why you don't just change the code you're debugging to use Data::Dumper or Data::Dump to show you the hashes? Even if you don't have full control over the code, Perl provides lots of ways to monkey-patch stuff in. If you could show some of the code that is generating this debug output, perhaps we could suggest a way to do that.	[reply] [d/l]