From: Elias Athanasopoulos <elathan@...>
Date: 2004-09-12T22:47:27+09:00
Subject: Re: Extending ruby with crypto++

On Wed, Sep 08, 2004 at 05:25:07PM +0900, Dominik Werder wrote:
>    bash-2.05b$ g++ -c cRubyTest.c
>    cRubyTest.c: In function `void Init_cRubyTest()':
>    cRubyTest.c:56: error: invalid conversion from `VALUE (*)(long
> unsigned int)'
>       to `VALUE (*)(...)'

This macro is taken from SWIG:

#ifdef __cplusplus
#  ifndef RUBY_METHOD_FUNC      /* These definitions should work for Ruby 1.4.6 
*/
#    define VALUEFUNC(f) ((VALUE (*)()) f)
#    define VOIDFUNC(f)  ((void (*)()) f)
#  else
#    ifndef ANYARGS             /* These definitions should work for Ruby 1.6 */
#      define VALUEFUNC(f) ((VALUE (*)()) f)
#      define VOIDFUNC(f)  ((RUBY_DATA_FUNC) f)
#    else /* These definitions should work for Ruby 1.7 */
#      define VALUEFUNC(f) ((VALUE (*)(ANYARGS)) f)
#      define VOIDFUNC(f)  ((RUBY_DATA_FUNC) f)
#    endif
#  endif
#else
#  define VALUEFUNC(f) (f)
#  define VOIDFUNC(f) (f)
#endif

It's pretty safe to use it in your extension. You should 
use this macro in rb_define_method() and similar functions:

/* Define method.  */
rb_define_method(klass, name, VALUEFUNC(f), -1);
            
Regards,
-- 
University of Athens			I bet the human brain 
Physics Department				is a kludge --Marvin Minsky