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From: david@sun.uucp (David DiGiacomo)
Newsgroups: comp.lang.c
Subject: Re: cpp of Sun's Unix version 3.2.
Message-ID: <17801@sun.uucp>
Date: Fri, 1-May-87 13:03:25 EDT
Article-I.D.: sun.17801
Posted: Fri May  1 13:03:25 1987
Date-Received: Sun, 3-May-87 01:20:56 EDT
References: <641@gama.is.tsukuba.junet>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 35

In article <641@gama.is.tsukuba.junet> yoshiki@gama.is.tsukuba.junet 
(Yoshiki Watanabe) writes:

>I have a trouble on cpp of Sun's Unix version 3.2.  I tryed to expand a text
>like the following.
>
># define Macro(f) f
>
>Macro(Func(a,
># ifdef B
>     b,
># endif
>     c))
>
>I want to get Func(a, c) if B is not defined...
>
>I can get what I want by other cpps (4.2BSD on VAX and Sequent).  Is this a
>bug of the cpp, or dependent on implementation?

As Guy has pointed out, it is implementation dependent.  However, there
is an easy way to get the result you want out of the Sun/SystemV cpp if
you don't mind defining an extra macro:

#define Macro(f) f

#ifdef B
#define IFB(x) x,
#else
#define	IFB(x)
#endif

Macro(Func(a, IFB(b) c)

-- 
David DiGiacomo, Sun Microsystems, Mt. View, CA  sun!david david@sun.com