Oh, I see, generate two different binaries of the same compiler with different compilers, and you know something is up if the same source compiled by those two separate binaries of the same compiler differ. Assuming the compiler is deterministic, that should work pretty well.

I wonder how well that would work in practice. There are actually quite a few bugs in C compilers[1], and compilers are complicated enough that I could see them hitting some of them when they are compiled. Has anyone done this before?

1: http://www.stanford.edu/class/cs343/resources/finding-bugs-c...