Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!taumet!steve
From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++
Subject: Re: Accessing base class constructors
Message-ID: <765@taumet.com>
Date: 13 Jun 91 17:02:10 GMT
References: <1991Jun12.183837.15084@bmw.mayo.edu>
Organization: Taumetric Corporation, San Diego
Lines: 28

bmc@mayo.edu (Bruce Cameron) writes:

>Being a novice to C++, I do not understand why I am unable to access a
>base class' constructor from a derived class...

>Yet when I try to do this with a base class that makes use of a vararg
>list I get a variety of syntax errors (using Sun C++2.1). Is it
>possible to have a base class constructor with a vararg list and
>derive classes from it that initialize the base class through its
>constructor? If not, any work arrounds for this? How are these
>supposed to work?

You can't do it.  There is no syntax to support just passing along
a variable argument list to any function, constructor or not.  You
have to use the facilities in <stdarg.h> or <varargs.h>.

Some workarounds:

1.  Don't use varargs in the constructor.  Pass an array of args,
either with a separate "count" argument, or a designated termination
value at the end of the array (like NULL for an array of pointers).

2.  Write an auxiliary private 'init' function called from constructors.
It takes a va_alist parameter.  The constructor sets up the va_alist
and passes it to the init function.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com