Horton

Memory leak in libxml2 (was Re: [PATCH] Add pretty-printed XML output option)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jim Jones <jim.jones@uni-muenster.de>
Cc: Peter Smith <smithpb2250@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Nikolay Samokhvalov <samokhvalov@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andrey Borodin <amborodin86@gmail.com>
Date: 2023-03-15T21:38:37Z
Lists: pgsql-hackers 
I wrote:
> BTW, the libxml leak problem seems to extend to other cases too.
> I tested with code like

> do $$
> declare x xml; t text;
> begin
> x := '<?xml version="1.0" encoding="utf8"?><foo><bar><val>73</val></bar></foo>';
> for i in 1..10000000 loop
>   t := xmlserialize(document x as text);
> end loop;
> raise notice 't = %', t;
> end;
> $$;

> That case is fine, but if you change the encoding spec to "latin1",
> it leaks like mad.  That problem is not the fault of this patch,
> I don't think.  I wonder if we need to do something to prevent
> libxml from seeing encoding declarations other than utf8?

After a bit of further testing: the leak is present in libxml2 2.9.7
which is what I have on this RHEL8 box, but it seems not to occur
in libxml2 2.10.3 (tested on Fedora 37, and I verified that Fedora
isn't carrying any relevant local patch).

So maybe it's worth working around that, or maybe it isn't.

			regards, tom lane

Commits

  1. Fix memory leak in XMLSERIALIZE(... INDENT).

  2. doc: Move documentation of md5_password_warnings to a better place

  3. Support [NO] INDENT option in XMLSERIALIZE().

  4. Add an expected-file to match behavior of latest libxml2.