#error in C
The #error preprocessor directive indicates error. The compiler gives fatal error if #error directive is found and skips further compilation process.
C #error example
Let’s see a simple example to use #error preprocessor directive.
- #include<stdio.h>
- #ifndef __MATH_H
- #error First include then compile
- #else
- void main(){
- float a;
- a=sqrt(7);
- printf(“%f”,a);
- }
- #endif
Output:
Compile Time Error: First include then compile
But, if you include math.h, it does not gives error.
- #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:
2.645751