-D and-U parameters of gcc: Macro settings and Cancellation

-D and-U parameters of gcc: Macro settings and cancellation-Linux general technology-Linux programming and kernel information. For details, refer to the following. During the last two days, LFS noticed the gcc-D parameter: Define the macro in the gcc command. For example, I have the following code:

CODE:/* hello. c */ # Include # Ifdef YES Char * str = "Yes, this is a macro ."; # Else Char * str = "No, there is no macro ."; # Endif Int main () { Printf ("% s \ n", str ); Return 0; }