How can we select the highest value from 3 disfferent #defined values???

Question

Hello,
Sometimes I come across the requirement of having the program automatically select the highest value
among several defined preprocessor command statements. For example:
#include "stdio.h"
#include <math.h>
#define _K_BUF_OTHERS 20
#define _k_BUF_ENV_TAGS 30
#define _k_BUF_REGS 40
#define _k_MAX(x, y, z) (max((max(x, y)), z))
int main(){
unsigned int u;
u = _k_MAX(_k_BUF_OTHERS,_k_BUF_ENV_TAGS, _k_BUF_REGS);
return 0;
In the sample above we have three (3) different define statements called :
_k_BUF_OTHERS
_k_BUF_ENV_TAGS
_k_BUF_REGS
but at any given time in certain C modules (In this case above, the main.c module) I require for the program to know
which of the three is the highest and get that highest value so I can use it downstream of my code. In this case the highest would be 40. So therefore putting the following macro anywhere in my code should make a text substitution of the macro's value
and return 40 to u:
u = _k_MAX(_k_BUF_OTHERS, _k_BUF_ENV_TAGS, _k_BUF_REGS);
But I can't even compile the program!
Here's the error I get in VC++:
1>------ Build started: Project: MinMax, Configuration: Debug Win32 ------
1>  Source1.cpp
1>c:\c++_tests\minmax\minmax\source1.cpp(15): error C3861: 'max': identifier not found
1>c:\c++_tests\minmax\minmax\source1.cpp(15): error C3861: 'max': identifier not found
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
Can someone please have a look and see what I am doing wrong.
All help appreciated...
Thanks
r

Answer 1

On 4/12/2015 4:30 PM, roberto wrote:
 1>c:\c++_tests\minmax\minmax\source1.cpp(15): error C3861: 'max': identifier not found
So implement or #define one. C standard library doesn't provide a function named "max".
Igor Tandetnik