From: Alex Fenton <alex@...>
Date: 2008-12-12T23:28:10+09:00
Subject: Re: Q: FFI and C++?

Jeremy Henty wrote:
> On 2008-12-11, Alex Fenton <alex@deleteme.pressure.to> wrote:
> 
>> Latest SWIG does  include C as a target language.  In other words it
>> can generate ANSI C wrapper code around C++ classes / libraries.
> 
> Very interesting!  Thanks.
> 
>> SWIG can also output a parse  of C++ classes and methods to XML. But
>> if this is all you want to  do, probably the Rb++ route is better as
>> it has existing Ruby classes for making use of the parse. I guess in
>> theory you might also be able  to generate the FFI code from this at
>> the same time.
> 
> That's my plan, but SWIG is an interesting option too.


Once you've had a chance to try things out, I'd be very interested in 
hearing about your experiences. I work on the bindings for a large C++ 
library (wxWidgets) and I'm looking at options for the next version.

We use SWIG at the moment to generate a (MRI-only) wrapper, but this 
means that hacking on the core library is a daunting prospect (SWIG is 
powerful but complex, C++ is hard and requires a compiler).

I looked a Rb++ for the whole work but there didn't seem to be enough 
gain for the pain of switching over a large code base. SWIG deals with 
several C++ features that aren't supported in Rb++ as far as I can tell: 
overloaded methods, implementing virtual methods in Ruby, keeping a 
one-to-one link between Ruby instances and C++ objects.

So I'm keen to find out if there's a way of reducing the complexity of 
the SWIG/C++ code and doing more of the wrapping work in Ruby - as well 
as being able to potentially run wxRuby on JRuby.

a