[Python-Dev] Deallocation of a pointer not malloced, any tips?

[Kumar McMillan]

On 4/20/07, Josiah Carlson <jcarlson at uci.edu> wrote:
> You may want the python-list mailing list or the equivalent
> comp.lang.python newsgroup, unless this is a bug with Python itself (you
> may try running Python 2.4.4, which is the next bugfix of the Python 2.4
> series).

yes, seems like it's either a bug in python or the mac os x malloc library.

>
> Regardless, you can help those who want to help you by providing the
> code that you have written that causes the error.  A doubly nested
> try/except isn't all that exciting, so I would guess many would be
> surprised that you are getting double free errors.

again, sorry for being vague.  i tried my best at reproducing it in a
test case but couldn't.  However, I finally experimented with trying
to force deallocation within the block of code and got something that
worked!

Here is a very small portion of it, with the fix, which was putting a
ref to the exc_info vars outside the tries and specifically del'ing
them in the finally block:

def load_or_rescue(self, load):
    etype, val, tb = None, None, None
    try:
        try:
            try:
                load()
            except Exception, exc:
                etype, val, tb = sys.exc_info()
                if not self.rescue_load((etype, val, tb), exc):
                    log.critical("EXCEPTION %s while processing %s",
                                                etype, self.ext_event)
                    raise exc, None, tb
        except NonFatalError, e:
            self.handle_non_fatal_error(e)
    finally:
        del etype, val, tb

to put this in perspective a little more, the warning/crash happens
when the code is getting called more or less like this...

def load():
    self.start_file(fileobj)
        for row in self.file_reader(fileobj):
            self.load_or_rescue(lambda: self.load_row(row))
self.load_or_rescue(load)