I was looking at the program at , mentioned in [another SO answer](https://stackoverflow.com/questions/19/fastest-way-to-get-value-of-pi/39512#39512) - it's supposed to print the value of pi, about 3.142, but when I compile it and run it I get `0.250`. It looks like when the GCC preprocessor (both 4.1.2 and 3.4.6 tested) runs on the code, it converts #define _ -F