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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: Questions on X3J11 draft
Message-ID: <5446@brl-smoke.ARPA>
Date: Mon, 15-Dec-86 10:50:34 EST
Article-I.D.: brl-smok.5446
Posted: Mon Dec 15 10:50:34 1986
Date-Received: Tue, 16-Dec-86 20:59:28 EST
References: <351@danews.ATT.COM> <7373@utzoo.UUCP> <3800@watmath.UUCP> <775@axis.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) )
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 6

In article <775@axis.UUCP> philip@axis.UUCP (Philip Peake) writes:
>How can I know, when trying to write portable code, if the 'library'
>function I am going to use is a real function or a macro ?

The only time it can matter is if it's a macro and you need a function.
In this case, #undef it first (this is harmless if it's not a macro).