Re: BUG #18943: Return value of a function 'xmlBufferCreate' is dereferenced at xpath.c:177 without checking for NUL

Michael Paquier <michael(at)paquier(dot)xyz> writes:
> On Tue, Jul 08, 2025 at 09:49:20AM +0000, Robin Haberkorn wrote:
>> I know this has already been committed, but why are we still using
>> PG_XML_STRICTNESS_LEGACY in xpath.c? As we are always checking
>> pg_xml_error_occurred() this should no longer be necessary.

> Are you sure that you can do that?

The comment in xml_errorHandler() argues

* Legacy error handling mode. err_occurred is never set, we just add the
* message to err_buf. This mode exists because the xml2 contrib module
* uses our error-handling infrastructure, but we don't want to change its
* behaviour since it's deprecated anyway. This is also why we don't
* distinguish between notices, warnings and errors here --- the old-style
* generic error handler wouldn't have done that either.

So switching to _ALL (or even _WELL_FORMED) mode would result in
nontrivial differences in the behavior of xpath.c's functions with
bad input. Maybe that's a reasonable thing to do, but it's a
question of user-visible behavior not just code cleanliness.

regards, tom lane