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From: rlk@chinet.UUCP (Richard Klappal)
Newsgroups: comp.lang.c
Subject: Re: How can I use #define to make something completely disappear?
Message-ID: <1817@chinet.UUCP>
Date: Tue, 3-Nov-87 22:57:23 EST
Article-I.D.: chinet.1817
Posted: Tue Nov  3 22:57:23 1987
Date-Received: Tue, 10-Nov-87 07:16:36 EST
References: <10083@brl-adm.ARPA>
Reply-To: rlk@chinet.UUCP (Richard Klappal)
Organization: Chinet - Public Access Unix
Lines: 70



In article <10083@brl-adm.ARPA> ultra!wayne@ames.arpa (Wayne Hathaway) writes:
>Time for my dumb question of the month ...
>I have the following sequence many times in a piece of code:
>        #ifdef DEBUG
>            printf("XYZ entry, p1=%x, p2=%x\n", p1, p2);
>        #endif DEBUG
>Normal old obvious stuff, right?  What I would like to do is replace
>all of these sequences with something like:
>
>            DBPRINT("XYZ entry, p1=%x, p2=%x\n", p1, p2);
>
>and then have one instance of something like:
>
>        #ifdef DEBUG
>        #define DBPRINT printf
>        #else
>        #define DBPRINT
>

Two ways I can think of:
	1) Check back a couple of weeks in the sources archives for
	Fred Fish's DBUG package.  It does exactly what you want, plus
	a whole lot more.

	2) When you edit the file to change the printf(...) to
	DBPRINT(...)  make it as follows:

#ifdef DEBUG
#define DBPRINT(args) printf args
#else
#define DBPRINT(args)
#endif

main()
{
	DBPRINT((x, y, z));
}


cc -E ... produces:

	# 1 "def.c"
	# 3 "def.c"

	main()
	{
		;
	}


cc -DDEBUG -E ... produces

	# 1 "def.c"

	# 5 "def.c"

	main()
	{
		printf (x, y, z);
	}

The extra set of parens does it.  This is adapted from Fred's
technique, to give credit where its due.  Thanks Fred.
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