Path: utzoo!attcan!uunet!lll-winken!csd4.milw.wisc.edu!bionet!ames!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: signal & sigvec error return codes
Keywords: signal sigvec error
Message-ID: <10319@smoke.BRL.MIL>
Date: 25 May 89 16:40:40 GMT
References: <8044@batcomputer.tn.cornell.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Distribution: comp
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 18

In article <8044@batcomputer.tn.cornell.edu> lijewski@batcomputer.tn.cornell.edu (Mike Lijewski) writes:
>Why not document the error return as being something
>along the lines of SIG_ERR, where SIG_ERR is defined as
>#define SIG_ERR ((int(*)())-1)
>in <signal.h>?

That's exactly what pANSI X3.159 requires (the macro, not the
particular value), except you have the type wrong -- it should be
((void(*)())-1).  Some older <signal.h>s also use the wrong types;
we got AT&T to fix theirs with SVR3, and other vendors will also need
to straighten this out for ANSI C and POSIX conformance.

Since you can't count on SIG_ERR being defined by non-ANSI <signal.h>,
what you should write is
	#include <signal.h>
	#ifndef SIG_ERR	/* assume the traditional implementation */
	#define SIG_ERR ((void(*)())-1)
	#endif