Re: [xml] [bug] external subset ignored by 2.9.0 when parsing in incremental mode

[Stefan Behnel <stefan_ml behnel de>]

[bump]

See patch in original e-mail.

Stefan Behnel, 28.09.2012 13:44:
> Hi,
>
> there is an unfortunate interaction between the "progressive" parsing mode
> and the loading of an external DTD, e.g. to inject defaulted attribute
> values. I see this in lxml's iterparse() implementation that started
> failing to inject them in libxml2 2.9.0. It uses incremental push parsing.
>
> The problem results from the fact that xmlSAX2ExternalSubset() in SAX2.c
> reuses the existing parser context, which, in this case, is in progressive
> mode. When it calls into xmlParseExternalSubset(), that starts by running
> the "GROW" macro, which is a no-opt in progressive mode. Thus, no data is
> available and xmlParseExternalSubset() terminates without doing anything.
>
> I'm not currently sure why it worked in older releases. I suspect that one
> of the many additional places that now set the ctxt->progressive field to 1
> might have triggered it.
>
> I'm not entirely sure about the right way to fix this. Maybe
> xmlSAX2ExternalSubset() should also back up and restore the "progressive"
> field of the context and then set it to 0 before calling
> xmlParseExternalSubset()? I attached a patch that does that and that fixes
> the problem for me.
>
> BTW, is it correct that "ctxt->progressive" is sometimes set to "1" and
> sometimes to things like "XML_PARSER_COMMENT" or "XML_PARSER_PI" in
> parser.c? Those values are more commonly assigned to the "instate" field.
>
> Stefan