Re: XML libs (was Re: gconf backend)

[Sander Vesik <Sander Vesik Sun COM>]

Havoc Pennington wrote:

> >  Well libxml2 uses callback for errors, that's the model everybody
> > uses and I'm not sure that was ever questionned by the relatively large
> > user base. Since your model seems to impose an asynchronous processing
> > I think this will need some discussion on the mailing-list. I cannot
> > change radically to a new model without at list a bit of explanation.
>
>
> Basically I want to write a function:
>
>  MyAppDataStructure*  load_xml_file (const char *filename, GError
> **error);
>
> So the question is how to do that. The problem is that functions such as
> xmlLoadACatalog() (totally random example) don't return any explanation
> of the error; you can look at errno, but you don't know if the errno is
> for stat() or open() or read() or there could be a parse error or
> out-of-memory and errno is junk. So the only possible error to display
> to the user is "failed to load catalog" or something, with no further
> diagnostic. Also, sometimes on failure it looks to me like
> xmlGenericError was called and sometimes it wasn't.
>
> What you want to display for a parse error is the line where the error
> happened and a problem description; for an I/O error you want strerror
> (errno). GError/DBusError/CORBA_environment/C++exceptions are a way to
> propagate this detailed information.
>
> Not that I really advocate doing this for libxml2; it seems like it
> would basically double your API size by adding
> xmlLoadACatalogWithError() and so forth. I _don't_ think this is a good
> idea, for the record.

So basicly you want a simple function that would do all and any 
boilerplate you would ever need (including turning off going to network 
if you haven't specifly told it it may do so) gives you GError feedback 
when something goes wrong and from then on lets you deal with the input 
just as if it was a flat stream of bytes which might be xml? The only 
not trivialy copy-paste part in that is dealing with GError.

> Havoc