From: Mauricio Fernandez <mfp@...>
Date: 2006-08-09T06:34:29+09:00
Subject: Re: Using C++ Member Function with rb_protect

On Wed, Aug 09, 2006 at 05:57:53AM +0900, Daniel Harple wrote:
> On Aug 8, 2006, at 4:45 PM, Francis Cianfrocca wrote:
> 
> >What happens if you remove the & in this line:
> >
> >VALUE val = rb_protect(&Sandbox::eval_protect,
> 
> I get this compile error:
> 
> test.cpp: In member function ‘VALUE Sandbox::eval(char*)’:
> test.cpp:15: error: argument of type ‘VALUE (Sandbox::)(VALUE)’ does  
> not match ‘VALUE (*)(VALUE)’

Of course it won't work that way, being a member function (it is given a
reference to this too...).

You'd have to do something like this (it's been a while without writing any
C++, so take this with a grain of salt):

class Sandbox {
public:
     Sandbox() {
         sandbox_ = rb_funcall(rb_const_get(rb_cObject, rb_intern("Sandbox")),
                               rb_intern("safe"),
                               0);
     }
     virtual ~Sandbox() {
     }
     VALUE eval(char * code) {
         int status = 0;
	 VALUE args[2];
	 args[0] = (VALUE)this;
	 args[1] = rb_str_new2(code);
         VALUE val = rb_protect(&call_eval_protect, (VALUE)args, &status);
         if (status) { /* handle error... */ }
         return val;
     }
private:
     static VALUE call_eval_protect(VALUE args) {
       Sandbox *me = ((Sanbox *)args)[0];
       VALUE code = ((VALUE *)args)[1];
       return rb_funcall(me->sandbox_, rb_intern("eval"), 1, code);
     }
     VALUE sandbox_;
};


-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby