Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!hplabs!hpl-opus!hpnmdla!hpmwtd!jeffa
From: jeffa@hpmwtd.HP.COM (Jeff Aguilera)
Newsgroups: comp.lang.c++
Subject: Re: function modifiers
Message-ID: <1520013@hpmwjaa.HP.COM>
Date: 10 Jan 90 22:40:20 GMT
References: <14940@robin.cs.nott.ac.uk>
Organization: HP Microwave Tech. - Santa Rosa, Ca.
Lines: 46

> In the code for the NIH library, there are several declarations of the
> following form:
> 
>     const Object* Object::method() const;
> 
> and also:
> 
>           friend const Object* Object::method() const;
> 
> I've tried to compile this with g++-1.36.2 and discovered that friends
> aren't allowed to have function modifiers in g++ i.e the terminating const. 
> Looking at the gnu manual, it seems that the use of the terminating const
> (see 6.12) supposedly has a meaning unique to g++, yet must be legal syntax
> for AT&T 2.0 since the library is written for that compiler.  
> 
> Removing the terminating const causes lots of other related error messages
> to do with const member functions calling non-const member functions etc.
> Unfortunately, we don't have AT&T C++ or a reference manual, so I'm unsure
> of the precise effect the use of const.
> 
> Could someone clarify this for me please and perhaps clear up the differences
> between AT&T and G++ ?
> 
> Alan Shepherd
> ----------

Within a non-static member function of a class X, this implicitly has one of
four types:

    X *const
    const X *const
    volatile X *const
    volatile const X *const //like boiling ice

That is, this cannot be modified (it's a *const), and *this is an X, const X,
volatile X, or volatile const X.  An X can be promoted to a const X, but not
the conversely.

Your problem with const friends can probably be circumvented by delegating
broader access rights:

    friend class Object;

If gnu doesn't compile the const member function, you're up a creek.
-----
jeffa