[boost] Re: Interest in C function pointer utility?

From: David Abrahams (dave_at_[hidden])
Date: 2005-05-20 10:19:11

Rene Rivera <grafik.list_at_[hidden]> writes:

> In rewriting a plugin interface I use, which for language portability 
> uses C function pointers as the entry points, I came up with a 
> "make_c_function" utility. I use it to translate C++ functions, any of 
> objects, binds, function, members, et. to _real_ C function pointers. 
> For example:
>
> class P
> {
>   public: int foo(int);
> };
>
> P p;
>
> extern "C"
> {
>   void * get_plugin_call(int n)
>   {
>     if (1 == n)
>     {
>       return make_c_function<P,int(int)>(
>         boost::bind(&p,p::foo,_1));
>     }
>     else { return 0; }
>   }
> }
>
> [example much abbreviated from real life use]

I don't see how this can work.  

P p;
Q q;

extern "C" int (*f1)(int) 
       = make_c_function<P,int(int)>(boost::bind(&p,P::foo,_1));
               
extern "C" int (*f2)(int) 
       = make_c_function<P,int(int)>(boost::bind(&q,P::foo,_1));

Don't these call the same function with the same stored data?

ooh, sneaky idea... do you specailize a class template on the address
of the argument to make_c_function, thus generating unique functions?

I would've used that idea in Boost.Python had I thought of it.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com