memory leak patch

[Dmitry Karasik]

Hi,

We're using valuerange processors and they seem to be leaking memory. Please find attached patch that seems to be fixing the problem.

Dmitry

[Olly Betts]

Do you have a corresponding testcase to make sure this doesn't regress?

[Dmitry Karasik]

Yes actually, but it was written for a local database, and it runs in an infinite loop while memory was observed in top. I don't have a good idea how this could be made in a decent automated test:

use Search::Xapian;

while (1) {
        my $db = Search::Xapian::Database->new('/var/local/index');
        my $qp = new Search::Xapian::QueryParser($db);
        my $valuerangeprocessor = Search::Xapian::StringValueRangeProcessor->new(1, 'test:', 1);
        $qp->add_valuerangeprocessor($valuerangeprocessor);
}

[Olly Betts]

Ah yes, you can't subclass the VRP in Perl to detect when it's destroyed, which would work for many of the other bindings.

Something like Devel::Leak might work here:

​http://search.cpan.org/~srezic/Devel-Leak/Leak.pm

Marking for 1.2.19 (trunk has SWIG-based Perl bindings which already handle this without leaking).

[Olly Betts]

OK, I've come up with a testcase using Devel::Leak.

I had to swap the order of the push and the call to the real method, or else the tests fail because set_stopper no longer returns undef.

Also, the object's value is simply a blessed reference to a scalar holding the address of the C++ object, so I've tweaked it to just use $$self as the hash key rather than the string representation of the object (which includes its address, so it works, but the hash key is larger than necessary).

Committed to 1.2 branch in r18200.

Keeping this open for now, as we should fix the other places where we currently leak objects like this in a similar way.

[Dmitry Karasik]

I would propose another change, I didn't realize that set_stopper keeps a single object ref, while add_valuerangeprocessor holds many.

[Olly Betts]

Thanks, but I actually already addressed that in r18201.

[Olly Betts]

OK, fixed where we were similarly leaking Stopper objects in TermGenerator and Sorter objects in Enquire in commits up to r18205. Should be in Search::Xapian 1.2.19.0.