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From: andy@Shasta.UUCP
Newsgroups: net.lang.c
Subject: Re: Disappearing function call
Message-ID: <947@Shasta.STANFORD.EDU>
Date: Tue, 28-Oct-86 03:11:23 EST
Article-I.D.: Shasta.947
Posted: Tue Oct 28 03:11:23 1986
Date-Received: Tue, 28-Oct-86 21:17:36 EST
References: <357@cullvax.UUCP> <162@omepd> <2865@rsch.WISC.EDU>
Reply-To: andy@Shasta.UUCP (Andy Freeman)
Organization: Stanford University
Lines: 31


#define	DEBUG	1 /* or 0 as appropriate */

#define	debug	if( DEBUG ) fprintf

(Replace fprintf with the appropriate function.)

Then you can write:
    debug( stderr, "wrong args %d, %s, %p\n", d, s, p ); /* %p is bogus */

Either your compiler eliminates dead code or it doesn't.
If it doesn't, other dead code and missed opportunities to generate
good code will swamp the overhead of checking if 0 is still 0 and
skipping the fprintf.  If it does, the fprintf (and its args) will be
removed.

-andy

ps - Yes, I know my debug will pick up a following "else".  I use "extra"
{}'s and debug( <args> ) shouldn't be followed by an "else" anyway; I'll
document that feature and let it slide.  It is difficult to handle all
possible constraints with something as limited as cpp; "debug( (<args>) )"
grates on me.

I'd rather write "if( DEBUG ) <code>" directly than "debug( <args> )"
because it doesn't restrict <code>.
-- 
Andy Freeman
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