Double slash comment substituition within a macro

Question

I am developing a PIC MCU program on an ansi-compliant compiler (Microchip XC8). There are two operation modes, determined via macros during compilation time. So that I don't want to duplicate one function-like macro due to one line of code, I would like to know if there is any way to write a macro such as

#define FOO //

so that when FOO is substituted it will actually cancel the rest of the line.

Writing a function instead of a macro is out of the question because the delay generated by function calls would disrupt the tight timings of my program (around some microseconds).

Answer 1

Comments are removed from the source before macro replacement occurs, so there's no way to define a macro exactly like that. However, it is certainly possible to pass an additional parameter into the macro to specify which code it should generate, or conditionally define the macro depending on the mode for which you are compiling.