On debug method(How to implement the "TRACE" macro?)

Many thanks,Davis.You give a very smart way.But the following statements

typedef unsigned long ULONG;
ULONG xdata * data pMem = 0;
TRACE (("Read Value:%lXH\n", *pMem));

//debug.h
#ifndef __DEBUG_H__
#define __DEBUG_H__

#ifdef _RELEASE
//release mode
#define TRACE(const char * format, ...)//cause error
#else
//debug mode
#include <stdio.h>
void TRACE (const char * format, ...);
#endif //_RELEASE

#endif //__DEBUG_H__

//debug.c
#include <stdio.h>
#include <stdarg.h>

void TRACE (const char * format, ...)
{
	va_list ap;
	va_start (ap, format);
	printf (format, ap)
	va_end (ap);
}

Many thanks,Davis.You give a very smart way.But the following statements

typedef unsigned long ULONG;
ULONG xdata * data pMem = 0;
TRACE (("Read Value:%lXH\n", *pMem));

//debug.h
#ifndef __DEBUG_H__
#define __DEBUG_H__

#ifdef _RELEASE
//release mode
#define TRACE(const char * format, ...)//cause error
#else
//debug mode
#include <stdio.h>
void TRACE (const char * format, ...);
#endif //_RELEASE

#endif //__DEBUG_H__

//debug.c
#include <stdio.h>
#include <stdarg.h>

void TRACE (const char * format, ...)
{
	va_list ap;
	va_start (ap, format);
	printf (format, ap)
	va_end (ap);
}

That error C214 you got almost certainly has nothing to do with the TRACE macro as such, but with the argument list you passed it.

#defining DEBUG or RELEASE is supposed to be done by the project / makefile, so you can decide at compile time, outside the code, which modules to compile with the debug printouts active.

Seriously, though: if you need to look into Microsoft SDKs to rip off a HIBYTE() macro instead of rolling your own, that's a strong sign you're in well over your head already. You'll have to brush up your knowledge of the C programming language considerably before you go on working on embedded software, I think.

What's wrong with my arg list?

"macros such as HIBYTE,LOBYTE etc,we must define it ourselves.A direct way is to steal the codes from the windows SDK or MFC"

Be very careful!

Not only are you dealing with a different Compiler, but also a completely different target.

You can't just steal them - you will need to read them carefully & fully understand them to be able to decide if they will give the right resuls with Keil C51, or what modifications are required!

You need something like this:

ifdef DEBUG
//Debug mode - TRACE causes printf output
#include <stdio.h>
#define TRACE(params) printf params;
#else
//Release mode - TRACE expands to nothing!
#define TRACE(params)
#endif // DEBUG

void some_func( char x )
{
   TRACE( ("Entered some_func( %bX )", x) )
   :
   :
}