Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!rlgvax!scc
From: scc@rlgvax.UUCP (Stephen Carlson)
Newsgroups: comp.lang.c
Subject: Re: Using Macros
Message-ID: <1316@rlgvax.UUCP>
Date: 11 Aug 90 00:01:26 GMT
References: <14339@shlump.nac.dec.com> <3526@goanna.cs.rmit.oz.au>
Reply-To: scc@rlgvax.OPCR.ICL.COM (Stephen Carlson)
Organization: ICL North America, OFFICEPOWER Products Center, Reston, VA
Lines: 31

In article <3526@goanna.cs.rmit.oz.au> ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
>I wasn't going to reply to this, but the Official Free Answer[*] is
>to use the expansion
>	do { /* your statements go here */ } while (0)
>This will work in any context where a statement is allowed; it wants
>a semi-colon after it just like a simple function call would.

Another way is:
	if (1) { /* your statements go here */ } else

This is just as valid as the do { ... } while(0) trick.  The semicolon would
terminate the else with a null statement, and the else avoids a dangling else
problem:
	if (cond)
		if (1) { ... } else ;
	else
		...

As a matter of style, I prefer to define statement-like macros that have no
arguments with an empty set of parenthesis:
	#define FOO() if (1) { int a; bar(&a); } else
and invoke it with
	FOO();
anywhere a statement is valid.  This has more of the feel of a function
call.  Although this works (a #define with 0 arguments) with every
preprocessor I've ever used, is there any official sanction for this
construct?
-- 
Stephen Carlson            | ICL OFFICEPOWER Center
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