It's not enough that the attackers aren't in communication, but rather that
they are mutually ignorant, which seems highly unlikely. I suspect even
benevolent compiler writers pay reasonably close attention to the work of
other compiler writers, and our malevolent compiler subverters seem likely
to pay even more attention to other compilers.
The attacker who inserted a back door into your gcc may have been smart
enough to make it also able to insert the same back door into pcc, or any
other compiler you can imagine. Which means that if you start out with
only one binary compiler, gcc, then you are out of luck, since you won't be
able to get an unsubverted compiler. Yes, this is harder, but we're
already talking about attackers who are creating very, very tricky code...
I suppose anything to raise the bar on the attack would seem worthwhile.
But it seems like it'd be a more effective approach to write a C compiler
in Forth or something else that is simple enough that you could write a
compiler for *it* in assembler (or machine code, if you don't trust the