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

[Daniel Gustafsson]

> On 15 Mar 2023, at 22:38, Tom Lane  wrote:

> 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.

2.9.7 is from November 2017 and 2.10.3 is from October 2022, so depending on
when in that timespan the issue was fixed it might be in a release which will
be with us for quite some time.  The lack of reports (that I was able to find)
indicate that it might be rare in production though?

--
Daniel Gustafsson

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

[Tom Lane]

I wrote:
> BTW, the libxml leak problem seems to extend to other cases too.
> I tested with code like

> do $$
> declare x xml; t text;
> begin
> x := ' encoding="utf8"?>73';
> for i in 1..1000 loop
>   t := xmlserialize(document x as text);
> end loop;
> raise notice 't = %', t;
> end;
> $$;

> 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