Well, if you are unsure if you can trust the second compiler (e.g. you didn't write it, audit it, bootstrap it yourself) you can just add a third (slightly more

Well, if you are unsure if you can trust the second compiler (e.g. you didn't write it, audit it, bootstrap it yourself) you can just add a third (slightly more trustedworthy) compiler. After that the infinite stack of turtles will take over and make sure it is asymptotically trustworthy.