From: Sylvain Joyeux <sylvain.joyeux@...>
Date: 2007-06-19T16:07:52+09:00
Subject: Re: Problem wrapping the C++ STL

> g++ -Wall -I. -I/opt/lib/ruby/1.8/i686-darwin8.9.1
> -I/opt/lib/ruby/1.8/i686-darwin8.9.1 -I.  -fno-common -g -O2 -pipe
> -fno-common  -c cvector.c
> cvector.c: In function 'void Init_cvector()':
> cvector.c:10: error: invalid conversion from 'VALUE (*)(int, VALUE*,
> VALUE)' to 'VALUE (*)(...)'
> cvector.c:10: error:   initializing argument 3 of 'void
> rb_define_method(VALUE, const char*, VALUE (*)(...), int)'
> make: *** [cvector.o] Error 1

C++ is more pissy than C about type convertions. You have to use the 
RUBY_METHOD_FUNC macro to convert cvector_init into the right type:

  rb_define_method(cVector, "initialize",
      RUBY_METHOD_FUNC(cvector_init), -1);

> > Note that you can wrap std::vector directly (no need to go through an
> > intermediate cvector structure)
>
> I guess I could store it as an instance variable within the constructor
> and refer back to it that way. I don't think it's faster, though. Or,
> did you have something else in mind?
The idea is *not* to use a cvector structure. Since you'll have to provide 
an alloc/free method pair anyway, allocate std::vector in them. Check 
value_set_alloc/value_set_free in 
http://www.laas.fr/~sjoyeux/darcs/utilrb/ext/value_set.cc

Sylvain