• Source 
    1. #include <stdio.h>
    2. #include <assert.h>
    3.  
    4. int main()
    5. {
    6.     char x = 7;
    7.  
    8.     /*  Some big code in between and let's say x
    9.        is accidentally changed to 9  */
    10.     x = 20;
    11.  
    12.     // Programmer assumes x to be 7 in rest of the code
    13.     #warning "this is warning message"
    14.     #error "there is error message"
    15.     assert(x==7);
    16.  
    17.     /* Rest of the code */
    18.  
    19.     return 0;
    20. }
    21.