C++ code - 8 lines

Link:

C++, pasted on Jan 12:

#include <stdio.h>

int main(){
    int k = 10;
    int b = --k + --k;
    printf("b = %d, k = %d", b, k);
    return 0;
}

Output:

1
2
3

cc1plus: warnings being treated as errors
In function 'int main()':
Line 5: warning: operation on 'k' may be undefined