Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!ccu.umanitoba.ca!ubitrex.mb.ca!dab
From: dab@ubitrex.mb.ca (Danny Boulet)
Newsgroups: comp.lang.c++
Subject: Re: call C++ from C
Keywords: C++/C
Message-ID: <1991Jun28.153143.5476@ccu.umanitoba.ca>
Date: 28 Jun 91 15:31:43 GMT
References: <359@soleil.jupiter.UUCP> <20463@alice.att.com>
Sender: news@ccu.umanitoba.ca
Organization: Ubitrex Corporation, Winnipeg, Manitoba, Canada
Lines: 51

In article <20463@alice.att.com> ark@alice.UUCP () writes:
>In article <359@soleil.jupiter.UUCP> rh@jupiter.UUCP (#Rachid Himmi) writes:
>
>> I'm looking for the way to call a C++ module from a C program through
>> the declaration of a class and the call of its function members.

In your C++ code, write C callable functions that invoke the C++ members.
For example:

---------------------- C++ code ------------------------

class fred {

public:
	.
	.
	.
    int doit(int x);
	.
	.
	.
};

extern "C" int
freddoit(void *ptr,int x)
{
    fred *p = (fred *)ptr;
    return( p->doit(x) );
}

----------------------------------------------------------

Call "freddoit" from C with a pointer to an instance of "fred" as the first
parameter and (in this example) an appropriate value for "x" as the
second parameter:

---------------------- C code ----------------------------

    w = freddoit(fredptr,124);

----------------------------------------------------------

I've no idea if this is supposed to work but it does for me.

>
>Turn your C program into a C++ program and it's easy.
>Otherwise, it's a matter between you and your implementer(s)
>and it's not guaranteed to work no matter what you do.
>-- 
>				--Andrew Koenig
>				  ark@europa.att.com