Conditional compile/assembly is a great means of having several (somewhat) similar products generated from the same source. I guarantees that if you fix a problem it will be fixed globally, one version will not be forgotten. I am very much a proponent of conditionals in product series code.
That much said, it sometimes makes it very difficult to read/follow the flow of a version of program. Does anyone know of a program creating a "clean source" for a given version i. e. a source with all ifdefs removed and only the lines that will be compiled for this version left?.

Erik