From: Lyle Johnson <ljohnson@...>
Date: 2002-04-05T02:52:17+09:00
Subject: Re: Help: Ruby<->C++ callbacks

> Also, now that I knew what to look for, I noticed that SWIG doesn't pass
> the "mark" function to Data_Wrap_Struct, only the "free" function...
> Lyle, are you reading? Can we do something about this? Or should I inject
> the relevant code by hand, instead of relying upon SWIG_NewPointerObj?

Actually, I added this feature to SWIG 1.3.12 (i.e. the CVS development
version) awhile back and have been meaning to get around to documenting it
;)

You can use SWIG's %markfunc directive to specify the name of a "mark"
function for a class:

    %markfunc RubyCallback "RubyCallback_markfunc";

    %{
    static void RubyCallback_markfunc(void *ptr) {
        RubyCallback *callback = static_cast<RubyCallback *>(ptr);
        rb_gc_mark(callback->p_);
    }
    %}

    class RubyCallback {
        // whatever
    };

For this example, SWIG should pass the function name "RubyCallback_markfunc"
to Data_Wrap_Struct() when it calls that. I'm using this all over the place
in FXRuby. Let me know if you run into any trouble with it.