Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: Notesfiles $Revision: 1.7.0.10 $; site uiucdcsb
Path: utzoo!watmath!clyde!cbosgd!ihnp4!inuxc!pur-ee!uiucdcsb!kenny
From: kenny@uiucdcsb.CS.UIUC.EDU
Newsgroups: net.lang.c
Subject: Re: NULL ROUTINE POINTERS
Message-ID: <139200018@uiucdcsb>
Date: Tue, 3-Dec-85 15:01:00 EST
Article-I.D.: uiucdcsb.139200018
Posted: Tue Dec  3 15:01:00 1985
Date-Received: Fri, 6-Dec-85 06:54:40 EST
References: <139@brl-tgr.ARPA>
Lines: 42
Nf-ID: #R:brl-tgr.ARPA:139:uiucdcsb:139200018:000:1064
Nf-From: uiucdcsb.CS.UIUC.EDU!kenny    Dec  3 14:01:00 1985


/* Written  7:08 pm  Nov 27, 1985 by jeff@isi-vaxa.arpa in uiucdcsb:net.lang.c */
/* ---------- "NULL ROUTINE POINTERS" ---------- */
After all the talk about null object pointers on machines with non-zero
null addresses, how would you portably define a null routine pointer?:

Assume that the routine returns a short, -
The following don't seem to work:

#define		NULLROUTINE		((short *()) 0)
#define		NULLROUTINE		((short *) 0())

And:

#define		NULLROUTINE		((short *0)())
or
#define		NULLROUTINE		((short)(*0)())

If all of the above make no sense...Then what?

						Jeff /* End of text from
uiucdcsb:net.lang.c */

To make a cast, write a (fully-parenthesized) declaration of one item of the
desired type, and then take out the name.  So, if you want a pointer to a
function returning short, you might say

short (*pfs) ();

To cast 0 to this type, it's

(short (*) ()) 0;

so

#define NULL_FUNCTION ((short (*) ()) 0)

Kevin
kenny@Uiuc.ARPA	kenny@Uiuc.CSNET
{ihnp4, pur-ee, convex}!uiucdcs!kenny

No opinions are expressed here, so no disclaimer is needed.