Path: utzoo!attcan!uunet!clyde.concordia.ca!mcgill-vision!quiche!utility
From: utility@quiche.cs.mcgill.ca (Ronald BODKIN)
Newsgroups: comp.lang.c
Subject: Re: macro inefficiency
Message-ID: <5110@quiche.cs.mcgill.ca>
Date: 1 Oct 90 20:41:00 GMT
References: <2514@cirrusl.UUCP> <5062@quiche.cs.mcgill.ca> <1990Oct1.002217.4945@craycos.com>
Organization: SOCS - Mcgill University, Montreal, Canada
Lines: 13

In article <1990Oct1.002217.4945@craycos.com> pmk@craycos.com (Peter Klausler) writes:
[that
	#define swap (a,b) { typeof (a) tmp; tmp = a; a = b; b = tmp; }
fails for if (..) swap(a,b); else ..., while changing the original to
>	#define swap (a,b) do { typeof (a) tmp; tmp = a; a = b; b = tmp; } \
>				while (0)
	works].
		Quite right (also pointed out to me in email), although
mine was better than the original, and if one's compiler doesn't optimize
away conditionals with fixed values, it produces better code.  However,
the idea of using do { ... } while (0) to allow a statement that is
closed by a semicolon is a good one.
		Ron