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From: kenny@uiucdcsb.cs.uiuc.edu
Newsgroups: net.lang.c
Subject: Re: Disappearing function call
Message-ID: <139200038@uiucdcsb>
Date: Fri, 3-Oct-86 10:49:00 EDT
Article-I.D.: uiucdcsb.139200038
Posted: Fri Oct  3 10:49:00 1986
Date-Received: Tue, 7-Oct-86 19:06:39 EDT
References: <357@cullvax.UUCP>
Lines: 46
Nf-ID: #R:cullvax.UUCP:357:uiucdcsb:139200038:000:1458
Nf-From: uiucdcsb.cs.uiuc.edu!kenny    Oct  3 09:49:00 1986


/* Written 12:44 pm  Oct  2, 1986 by marcus@ihlpl.UUCP in uiucdcsb:net.lang.c */
>In article <357@cullvax.UUCP> drw@cullvax.UUCP (Dale Worley) writes:
>>What I want to do is to write a function call of a variable number of
>>arguments:
>>
>>	debug(x, y, z, ...)
>>
>>that will generate no code when the symbol DEBUG is not defined,
[...]
>How about this:
>
>#ifndef	DEBUG
>#define debug
>#endif
>
>and writing in the code:
>
>	debug(a,b,c)
>
>If DEBUG is turned on, nothing will happen to the debug statements, so a
>call to debug will be produced (as you would expect).  If DEBUG isn't
>defined, the symbol "debug" will be pre-processed out of existance, so
>the compiler will see an expression like:
>
>	(a,b,c)
[...]
>Are there any problems with doing this?  I suppose that some pre-processors
>could choke on the parenthesis after debug in the invocation, since debug
>is #defined as a parameter-less macro, but my pre-processor (SVR2) doesn't.
>
>Marcus Hall
/* End of text from uiucdcsb:net.lang.c */

If you invoke it in the code as

	debug (a, b, c)
	     ^ Note the space!

then no preprocessor should ever confuse it; macros with parameters are
recognized only if no space intervenes between the macro name and the
left parenthesis.

Kevin Kenny			     UUCP: {ihnp4,pur-ee,convex}!uiucdcs!kenny
University of Illinois at Urbana-Champaign	       CSNET: kenny@UIUC.CSNET
``Don't worry; I'm a New Yorker!'' ARPA: kenny@B.CS.UIUC.EDU (kenny@UIUC.ARPA)