Re: [PATCH] Fix refcounting bug in typecaster

Federico Di Gregorio <fog-NGVKUo/i/[email protected]> Thu, 08 Apr 2010 18:24:01 +0200

Newsgroups	gmane.comp.python.db.psycopg.devel
Message-ID	<[email protected]>

On 07/04/2010 21:19, Michael Tharp wrote:
> I have found the cause of the assertion error from earlier. The key was
> getting it through my insufficiently-caffeinated skull that the crash
> was happening in the middle of a call to the caster function, where a
> new object being instantiated triggered a garbage collection. The GC
> then trips over a too-small refcount on the type object which is
> reachable twice even though the refcnt is only 1.

I created a test case out of your example code but my psycopg2 on Python
2.5 passes the test here. Can you please run the test and confirm that
it shows the problem? Test code attached to this email.

federico

-- 
Federico Di Gregorio                                       fog-NGVKUo/i/[email protected]
                  Beh un bacio, se ben dato, non si rifiuta. --  <laura>

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bug_gc.py (text/x-python, 784 B)

#!/usr/bin/env python

import psycopg2
import psycopg2.extensions
import time
import unittest
import gc

import sys
if sys.version_info < (3,):
    import tests
else:
    import py3tests as tests

class StolenReferenceTestCase(unittest.TestCase):
    def test_stolen_reference_bug(self):
        def fish(val, cur):
            gc.collect()
            return 42
        conn = psycopg2.connect(tests.dsn)
        UUID = psycopg2.extensions.new_type((2950,), "UUID", fish)
        psycopg2.extensions.register_type(UUID, conn)
        curs = conn.cursor()
        curs.execute("select 'b5219e01-19ab-4994-b71e-149225dc51e4'::uuid")
        curs.fetchone()

def test_suite():
    return unittest.TestLoader().loadTestsFromName(__name__)

if __name__ == "__main__":
    unittest.main()

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