Variable length arg lists for macros

[Kristian Wedberg]

In article <438 at ucsvc.unimelb.edu.au>, u5565522 at ucsvc.unimelb.edu.au (David Clunie) writes:
> How do people feel about the idea of preprocessor macros with variable
> length argument lists ?
> 
> The concept has already been enshrined for true functions, allowing
> protoypes for things like the printf() family of functions, and a set of
> portable functions and macros to access the list of arguments.
> 
> However this can not be done with macro calls. Wouldn't it be nice to be
> able to do something like ...
> 
> 
> 	#ifdef TRACE
> 
> 	#define	tracef(s,...)	printf(s,...)
> 
> 	#else
> 
> 	#define	tracef(s,...)	/* nothing */
> 
> 	#endif
> 
	...
 
> 	Regards ... David Clunie


My solution for the debugging-part of this is to use several macros.
The following is a (very) small extract from my debug-includefile:


#ifndef DEBUG_H
#define DEBUG_H

/* name:  debug.h
 *
 * description:  Header-file with debug-macros & prototypes.
 *
	pr(text)		: print text (no " " or \n, & NO COMMAS!)
	pr0("..\n") - pr6(...)	: print string (with 0 - 6 arguments)
 *
 * problems:
 *	??? No commas in pr() ???
 */

/* pr(), pr1() -> pr6()
 * Produces no code when NPRINTING is defined! Just an empty statement
 * from the semicolon.
 */

/*	Print without arguments. "..." NOT needed */
#ifndef NPRINTING
#define pr(s)	printf("s\n")
#else
#define pr(x)
#endif

/*	Print with 0 to 6 arguments & "...\n" */
#ifndef NPRINTING
#define pr0(s)				printf(s)
#define pr1(s,a1)			printf(s,a1)
#define pr1(s,a1)			printf(s,a1)
#define pr2(s,a1,a2)			printf(s,a1,a2)
#define pr3(s,a1,a2,a3)			printf(s,a1,a2,a3)
#define pr4(s,a1,a2,a3,a4)		printf(s,a1,a2,a3,a4)
#define pr5(s,a1,a2,a3,a4,a5)		printf(s,a1,a2,a3,a4,a5)
#define pr6(s,a1,a2,a3,a4,a5,a6)	printf(s,a1,a2,a3,a4,a5,a6)
#else
#define pr0(x)
#define pr1(x,x1)
#define pr2(x,x1,x2)
#define pr3(x,x1,x2,x3)
#define pr4(x,x1,x2,x3,x4)
#define pr5(x,x1,x2,x3,x4,x5)
#define pr6(x,x1,x2,x3,x4,x5,x6)
#endif


Hope you'll find it useful...

					Kristian Wedberg