Re: [xml] initGenericErrorDefaultFunc weirdness.

["William M. Brack" <wbrack mmm com hk>]

OK, sorry about that - I must be more careful to respond accurately!

Basic C programming example follows:-
---------------------------------------
  bill billsuper work $ cat bb.c
  #include <libxml/xmlerror.h>
  void MyXMLErrorFunction(void *ctx, const char *msg, ...)
  {
    return;
  }

  int main(int argc, char **argv) {
    initGenericErrorDefaultFunc(
      (xmlGenericErrorFunc *)&MyXMLErrorFunction
     );
  return 0;
  }
  bill billsuper work $ gcc -Wall \
    `../xmlinstall/bin/xml2-config --cflags --libs` \
    -o bb bb.c
  bill billsuper work $
-------------------------------------------

The function initGenericErrorDefaultFunc takes a single argument
which is the *address* of a function of type xmlGenericErrorFunc. 
Therefore, since MyXMLErrorFunction is declared as type void, it is
necessary to specify a type override.  The required type is the
address (i.e. a pointer to) a xmlGenericErrorFunc, and in C that is
written as (xmlGenericErrorFunc *).

HTH

Bill


Jose Commins said:
>       With your suggestion below, I get ' main.c:109: error: invalid
> lvalue
> in unary `&' '
>       With this:
> initGenericErrorDefaultFunc((xmlGenericErrorFunc)&MyXMLErrorFunction)
> I
> still get: 'main.c:109: passing arg 1 of
> `initGenericErrorDefaultFunc'
> from incompatible pointer type' error.
>       Argh!
>
>
> Regards,
>               Jose.
>
> --
>   Death, taxes and Microsoft. If you put it that way, the first two
> don't seem so bad.
>
> On 2 Jun 2004, at 3:37 am, William M. Brack wrote:
>
> > Jose Commins said:
> > >     Odd, I am trying to use:
> > >
> > >     initGenericErrorDefaultFunc((xmlGenericErrorFunc)MyXMLErrorFunction);
> > >
> > >     But I get this error on compilation:
> > >
> > >     main.c:109: passing arg 1 of `initGenericErrorDefaultFunc' from
> > > incompatible pointer type
> > >
> > >     And here's my function:
> > >
> > > void MyXMLErrorFunction(void *ctx, const char *msg, ...)
> > > {
> > >     printf("Aiee!  And error has occured!\n");
> > > }
> > >
> > >
> > >     I've tried everything: using the direct address, different
> > > assignments
> > > and so on, but I either get the same error or bus errors.  I *do*
> > > have
> > > this working:
> > >
> > >     xmlSetGenericErrorFunc(NULL,
> > > (xmlGenericErrorFunc)MyXMLErrorFunction);
> > >
> > >     And that works fine.
> > >
> > >     But, am I doing something wrong with the declaration/assignment
> > > of
> > > 'initGenericErrorDefaultFunc' or is it b0rked?
> > >
> > >
> > > Regards,
> > >             Jose.
> >
> > From xmlerror.h:
> > XMLPUBFUN void XMLCALL
> >     xmlSetGenericErrorFunc      (void *ctx,
> >                                  xmlGenericErrorFunc handler);
> > XMLPUBFUN void XMLCALL
> >     initGenericErrorDefaultFunc (xmlGenericErrorFunc *handler);
> >
> > so perhaps you could try
> >
> > initGenericErrorDefaultFunc(&(xmlGenericErrorFunc)MyXMLErrorFunction);
> >
> > (i.e. use the '&' address-of operator)?
> >
> > Regards,
> >
> > Bill
>
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