I am currently working on code where at any given build less than 1/3 is actually compiled. I have no qualms with it, it is the natural way to build this project (and many others). However, I found 2 large files with basically one #if COND at top #else in the middle and #endif at the end. These files I divided into xxxb1.c and xxxb2.c and made a conditional in the "builder code" (xxx.bat) copy the appropiate file to the original name. The story here is that, as we all know, "there is no one way to skin a cat". Use the method that gives maximum readability WITHOUT EVER HAVING TO MAKE THE SAME CHANGE IN 2 FILES, you WILL one day forget the other place.

Have fun, choose wisely

Erik