Re: PG_CATCH used without PG_RETHROW

Hi, I think this is a bug because this function's CATCH clause does not
restore memroycontext. Thus when leaving the function, the
CurrentMemroyContext
will be ErrorMemroyContext.

I see this part of code is refactored in master branch, but in
REL_16_STABLE, the code
is still there.

The following SQL might lead to PANIC (reference to memory that just reset)

zlyu=# select version();
version
-------------------------------------------------------------------------------------------------------------
PostgreSQL 15.3 on aarch64-unknown-linux-gnu, compiled by gcc (Ubuntu
11.4.0-1ubuntu1~22.04) 11.4.0, 64-bit
(1 row)

zlyu=# select xml_is_well_formed('<a>') or
array_length(array_append(array[random(), random()], case when
xml_is_well_formed('<a>') then random() else random() end), 1) > 1;
ERROR: cache lookup failed for type 2139062143
zlyu=#

Simple fix is to backport the change from master branch or restore the
context.

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> 于2023年8月2日周三 16:32写道：

> Greg Stark <stark(at)mit(dot)edu> writes:
> > My understanding is that PG_TRY/PG_CATCH doesn't save enough state to
> > avoid rethrowing errors and if you want to actually continue the
> > transaction you must use a subtransaction. As a result I was under the
> > impression it was mandatory to PG_RETHROW as a result.
>
> > If that's the case then I think I just came across a bug in
> > utils/adt/xml.c where there's no PG_RETHROW:
>
> The reason we think that's OK is that we assume libxml2 does not call back
> into the general backend code, so there is no PG state we'd have to undo.
>
> regards, tom lane
>
>
> --
> Sent via pgsql-hackers mailing list (pgsql-hackers(at)postgresql(dot)org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-hackers
>
>
>