From:	Eric Backus <ericb AT lsid DOT hp DOT com>
Subject:	Re: How do you eliminate dead code?
To:	pcrowley AT qdeck DOT com
Date:	Tue, 6 Jul 93 15:42:50 PDT
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu (djgpp)
Mailer:	Elm [revision: 66.25]

> #define TRACE 0
> 
> if (TRACE) fprintf(stderr...
> 
> this gets assembled as
> jmp            --\
> push             |
> ...              |
> call fprintf     |
>                <-/
> 
> I am compiling this with -O2 -m486. Does anyone know if there is a switch
> to eliminate the inaccessable code?

I am quite surprised that gcc does not eliminate the dead code.
However, I usually do this in one of two ways:

Way 1:
	/* At the beginning of the file */
	#define	DEBUG

	/* To print debug info */
	#ifdef	DEBUG
		fprintf(stderr, "stuff");
	#endif

In this case, I turn off debugging by commenting out the #define DEBUG.


Way 2:
	/* At the beginning of the file */
	#define	DEBUG(s)	s

	/* To print debug info */
	DEBUG(fprintf(stderr, "stuff"));

In this case, I turn off debugging by commenting out the "s" that is
the definition of the DEBUG macro.


In either case, if I turn off debug, the compiler doesn't even see the
debugging fprintf statements.
--
				Eric Backus
				ericb AT lsid DOT hp DOT com
				(206) 335-2495

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