From: Gary <gapjunk@...>
Date: 2007-10-21T00:20:02+09:00
Subject: Re: Building an extension in C++


Thank you mental!!!  It works.  I should have figured it out myself,
but I needed your help.

I'm I bit confused about a C-linkage interface to the C++ portion.  Is
this going to be more than wrapping the C++ calls in try catch(...)
In other words having something like

extern "C" VALUE t_init(VALUE self)
{
  //declare any Ruby C++ data conversion vars in C
  try
    {
    //call C++ functions
    }
  catch(...)
    {
    //process exceptions
    }
  //Do any data interactions between C++ and Ruby
}

Once again, thanks!  I spent several hours stumped.

     -Gary

On Oct 19, 3:33 pm, MenTaLguY <men...@rydia.net> wrote:
> On Sat, 20 Oct 2007 07:15:05 +0900, Gary <gapj...@gmail.com> wrote:
> > I'm using cygwin to try to build an extension in C++.  I've stripped
> > down the pickaxe book's example (http://www.rubycentral.com/pickaxe/
> > ext_ruby.html) to the bare minimum.  It looks like:
>
> > #include "ruby.h
>
> > VALUE cTest;
>
> > void Init_Test() {
> >   cTest = rb_define_class("Test", rb_cObject);
> > }
>
> Although it is not the source of the problem with the shared object
> not being found, you need to declare Init_Test with C linkage
> (extern "C"), or else Ruby will not be able to find the entry point.
>
> Besides this, though, safe handling of C++ and Ruby exceptions is
> extremely difficult when writing an extension in C++.  You should
> probably consider writing the Ruby-facing portion of extension in
> C, with a C-linkage interface to the C++ portion of the extension,
> and be sure to intercept any C++ exceptions before they can cross
> into C or Ruby and create havoc.  Similarly, C++ code should not
> raise Ruby exceptions or call anything which could raise them.
>
> -mental