Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!oliveb!apple!rutgers!att!westmark!mole-end!mat
From: mat@mole-end.UUCP (Mark A Terribile)
Newsgroups: comp.lang.c++
Subject: Re: ptr to member function, even worse
Summary: Hang on a little longer ...
Message-ID: <168@mole-end.UUCP>
Date: 6 May 89 03:45:15 GMT
References: <937@garya.Solbourne.COM>
Organization: mole-end--private system.  admin: mole-end!newtnews
Lines: 30

> OK, everyone has been real helpful ... we've [figured] out what g++ and
> cfront are doing with address of virtual function references.  But ...
 
> Consider a function
 
> 	dispatch(objp,fnp)
 
> which has very little knowledge of its arguments.  It knows the following:
 
> 	objp is a pointer to a C++ object
> 	fnp  is a pointer to a member function for objp (possibly virtual)
 
> In particular, dispatch has no knowledge of the base class for objp.

 
> Anybody have other thoughts or answers for something that works today?
> This is a major hangup for us, since we have user applications inserting
> objects and callback functions in a dispatch table.

Not today, but in a few weeks.  The proper solution, which will unfortunately
affect your users, is to represent the callback operation by a base class and
to use Multiple Inheritance.  Then your users derive their classes to be called
back from the callback class, and use a virtual function derived from that
class as the callback function.

Like lots of other people, I'm looking forward to MI.
-- 

(This man's opinions are his own.)
From mole-end				Mark Terribile