Memory leak when leaving 'each' loop prematurely

[Terris]

use DBM::Deep;

my %db;

tie %db, "DBM::Deep", "foo.db";

$db{ 'a' } = { 'b' => { } };

untie %db;

for ( ;; ) {

    tie %db, "DBM::Deep", "foo.db";

    my $hash = $db{'a'};

    while ( each %{$hash} ) {

        last;

    }

   untie %db;

}

If you comment out the 'last' in the while loop, the leak will disappear. I also tied the next_key API. That didn't fix the problem. I tried many things - e.g., weaken, calling keys on the 'a' hash, using OO instead of tie, closing via stuff like "tied %db->engine->close" and on and on (I spent several days working on alternatives). The only thing that fixes the leak is to use "each" all the way to the end of the hash prior to untie.

This isn't a special case, either. For me, it happens to every hash stored in DBM::Deep.

Terris

[Rob Kinyon]

I'm really sorry to hear that there's a memory leak that's causing you
issues. Could you take this work and bundle it as a test we can put
into our t/ folder? I would be delighted to take a pull request
against https://github.com/robkinyon/dbm-deep with this failing test.

Thanks,
Rob

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Thanks,
Rob Kinyon
http://greenfishbluefish.com/

[Terris Linenbach]

Hello,

How do you make a test for a memory leak? I can see the leak happening with top and ps. How do you make Perl see it?

Thanks,

Terris

[Rob Kinyon]

I'm sorry about taking so long to respond. I switched gmail clients
and didn't realize some emails weren't visible in my new client.

Memory leaks in Perl only happen when there are cycles. So, look at
http://search.cpan.org/~petdance/Test-Memory-Cycle-1.04/Cycle.pm

[Terris]

memory_cycle_ok fails to find any cycles in \%db or $hash, so I'm still at a loss for how to write a unit test. 

Something is holding onto memory allocated by DBM::Deep that I am unable to get to.

Thanks,

Terris

[Terris]

By the way, the above program eventually terminates with the error:

DBM::Deep: Cannot sysopen file 'foo.db': Too many open files