Suppose you need a c compiler. It would be preferable to write that compiler in a c-like language, given the complexity of a compiler of that degree. At best, the c compiler would be written in c, but that would require a c compiler to begin with. If a mistake is made in the making of one of the early iterations of compilers, it could propagate. How do compilers make sure that this doesn't happen? Obviously, no code is flawless, not even the processor is, but if you haven't somehow measured the stability, you don't even know if your compiler is stable. What assumptions are made and how is it justified? I would imagine it would be architecture-dependent too.
Edit: By stability, I mean that the code runs as intended.