Question

I have the following code snippet:

#ifdef DO_LOG
#define log(p) record(p)
#else
#define log(p)
#endif

void record(char *data){
.....
.....
}

Now if I call log("hello world") in my code and DO_LOG isn’t defined, will the line be compiled, in other words will it eat up the memory for the string “hello world”?

P.S. There are a lot of record calls in the program and it is memory sensitive, so is there any other way to conditionally compile so that it only depends on the #define DO_LOG?

Answer 1

This should be trivial to verify for yourself by inspecting the resulting binary.

I would say “no”, since the expression totally goes away, the compiler will never see the string (it’s removed by the preprocessor’s macro expansion).