Comment Re:on Single Compilers (Score 1) 333
You should read Ken Thompson's "Reflections on Trusting Trust" and the thesis that shows how to detect that attack (forgot the name of the author - Bruce Schneier has written a good summary of it, though). This will tell you why you want multiple compilers for some things.
Very short summary (probably wrong - it's confusing): You want to compile your production compiler with two different compilers to check if the binaries these resulting production compiler binaries produces are the same (e.g. you let the production compiler compile itself again using the two different binaries). Your alternate compiler does not strictly have to be up to date or fully featured for that. It must only be able to compile the compiler that was used for creating the actual product under scrutiny.