Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!mintaka!bloom-beacon!world!burley
From: burley@world.std.com (James C Burley)
Newsgroups: comp.lang.c
Subject: Re: Using Macros
Message-ID: <BURLEY.90Aug7203411@world.std.com>
Date: 8 Aug 90 00:34:11 GMT
References: <14339@shlump.nac.dec.com> <manning.650051935@gap>
	<14404@diamond.BBN.COM>
Sender: burley@world.std.com (James C Burley)
Organization: The World
Lines: 24
In-Reply-To: mlandau@bbn.com's message of 7 Aug 90 20:00:19 GMT

In article <14404@diamond.BBN.COM> mlandau@bbn.com (Matthew Landau) writes:

   Seems like this should be on the FAQ list, since it comes up every 
   couple of months.  My preferred solution to the problem (which I 
   picked up in comp.lang.c about 10 years ago :-) is:

      #define FOO(bar, baz)  do { func1(bar); func2(baz); } while (0)

Hmmm, when I first saw the problem posted, I thought I knew the easy and
consistent answer, but all these other responses differ from mine.

Can anyone explain to me why

    #define FOO(bar,baz) (func1(bar), func2(baz))

wouldn't work in all the situations one could reasonably expect?  The macro
still expands to a single expression (as did the old version mentioned in the
original posting), right?  So a trailing semicolon causes it to be
interpreted as a statement, right?  The comma within the expansion serves
the same purpose of defining a sequence point as would the semicolon in other
solutions, right?  I have the horrible feeling I'm missing something, but I do
think I've done this before and it worked okay.

James Craig Burley, Software Craftsperson    burley@world.std.com