C #error
Let's explore a basic illustration of employing the #error preprocessor directive.
Example
Example
#include<stdio.h>
#include <math.h>
#ifndef __MATH_H
#error First include then compile
#else
void main(){
float a;
a=sqrt(7);
printf("%f",a);
}
#endif
Output:
Output
Compile Time Error: First include then compile
However, when you include math.h, it does not produce an error.
Example
Example
#include<stdio.h>
#include<math.h>
#ifndef __MATH_H
#error First include then compile
#else
void main(){
float a;
a=sqrt(7);
printf("%f",a);
}
#endif
Output:
Output
2.645751
