> to make sure that a compiler cannot do anything other than reading its input files (and system headers/libraries/etc) Define "input files." Tools have to do

> to make sure that a compiler cannot do anything other than reading its input files (and system headers/libraries/etc) Define "input files." Tools have to do a combination of reading, parsing, and sometimes even version unification/downloads just to get the complete set of inputs to feed to the compiler. Of course you can define the compiler as the tool that parses text and writes machine code, but then you're just shoveling dirty water around.