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Re: pltcl.so patch

From: Neil Conway <neilc(at)samurai(dot)com>
To: "Nigel J(dot) Andrews" <nandrews(at)investsystems(dot)co(dot)uk>
Cc: Ian Harding <ianh(at)tpchd(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: pltcl.so patch
Date: 2002-09-25 04:56:32
Message-ID: 877khazmyn.fsf@mailbox.samurai.com (view raw or flat)
Thread:
Lists: pgsql-hackers
"Nigel J. Andrews" <nandrews(at)investsystems(dot)co(dot)uk> writes:
> Yes, I do get the similar results.
> 
> A quick investigation shows that the SPI_freetuptable at the end of
> pltcl_SPI_exec is trying to free a tuptable of value 0x82ebe64
> (which looks sensible to me) but which has a memory context of
> 0x7f7f7f7f (the unallocated marker).

Attached is a patch against CVS HEAD which fixes this, I believe. The
problem appears to be the newly added free of the tuptable at the end
of pltcl_SPI_exec(). I've added a comment to that effect:

	/*
	 * Do *NOT* free the tuptable here. That's because if the loop
	 * body executed any SQL statements, it will have already free'd
	 * the tuptable itself, so freeing it twice is not wise. We could
	 * get around this by making a copy of SPI_tuptable->vals and
	 * feeding that to pltcl_set_tuple_values above, but that would
	 * still leak memory (the palloc'ed copy would only be free'd on
	 * context reset).
	 */

At least, I *think* that's the problem -- I've only been looking at
the code for about 20 minutes, so I may be wrong. In any case, this
makes both memleak() and memleak(1) work on my machine. Let me know if
it works for you, and/or if someone knows of a better solution.

I also added some SPI_freetuptable() calls in some places where Nigel
didn't, and added some paranoia when dealing with statically sized
buffers (snprintf() rather than sprintf(), and so on). I also didn't
include Nigel's changes to some apparently unrelated PL/Python stuff
-- this patch includes only the PL/Tcl changes.

Cheers,

Neil

-- 
Neil Conway <neilc(at)samurai(dot)com> || PGP Key ID: DB3C29FC

Attachment: tcl-fix.patch
Description: text/x-patch (12.7 KB)

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