Re: Warning 303: %extend defined for an undeclared class opencascade::handle.

On Mon, 27 Jul 2020 at 12:56, Kustaa Nyholm <[email protected]>
wrote:

>
>
> > On 27 Jul 2020, at 11.18, Kustaa Nyholm <[email protected]>
> wrote:
> >
> > I get the 303 for following, although the test_ball seems to compile
> fine?
> >
> > I just can't figure this out.
> >
> >
> > %{
> > #include <Standard_Transient.hxx>
> >
> > opencascade::handle<int> test_ball;
> >
> > %}
> >
> > %extend opencascade::handle
> > {
> >
> > };
> >
> > I've looked into Standard_Transient.hxx and there handle is forward
> declared as:
> >
> > namespace opencascade {
> >  template <class T> class handle;
> > }
> >
> > I cannot seem to find the actual class def for handle though.
> >
> > wbr Kusti
> >
>
> Found the actual class def and I think I know how to solve this, but
> I still not understand why the above does not work.
>
> You have correctly observed that you have a forward class declaration but
no definition, SWIG should really technically warn:
  Warning 303: %extend defined for an undefined class opencascade::handle
rather than:
  Warning 303: %extend defined for an undeclared class opencascade::handle
in this case, subtle difference!


> First of all I figure I should be working on class 'Standard_Handle', not
> handle,
> but to make it work I need to introduce Standard_Handle to SWIG like this:
>
>
> class Standard_Handle {
>     Standard_Handle()=0;
> };
>
The above is not valid C++, so I wouldn't much to work!


> %ignore operator Standard_Transient*();
>
> %extend Standard_Handle
> {
>     operator Standard_Transient* ()
>     {
>       return static_cast<Standard_Transient*>(this);
>     }
>
> };
>
>
> And this is because the actual header that contains the declaration is
> never seen by
> SWIG cause I'm / the SWIG .i files I'm working on do not feed that/those
> headers to it, right?
> The include above is only processed by the C++ compiler.
>
> Ok, so above produces no warnings, however it does not fix the actual
> problem
> I'm having but I will make an other post of it.
>
>
I suggest reading the SWIG Basics chapter at
http://swig.org/Doc4.0/SWIG.html. It should describe the areas which aren't
clear to you; namely the differences between %include, #include, what SWIG
parses, the SWIG preprocessor and C preprocessor.

William

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