problem using #define to substitute functions This might be more a general programming question, but I am using the Arduino compiler, and I've created my own ISR driven version of millis(), which I simply call myMillis(). So let's say I'd like to use this addition to a working project. Rather than do a global search and replace, I got the idea to simply put this define near the top of the program...

#define millis myMillis

uint32_t myMillis() 
  { // my code ...
  }


So when I compile, every instance of millis() does indeed compile as if I did a global search and replace. I like that, because it means I don't have to make the change permanent, and can easily comment out my defines to compare program operation.

My question is, if I do as I just explained, what if, for whatever reason, there is some place within the project where I actually WANT to call the original version. A simple example might be if I wanted to occasionally output a message via serial.println(), comparing the returned value of millis() and myMillis(). I think there is a way to specify such an exception to my #define MACRO, but I'm not sure how.
There is no way to suppress define substitution. You could use #undef and then #define again in required section.

Name the define MILLIS and use this name in code, except where you want the original millis() function.