The only error I found where the code compiled but was wrong was from it assuming a particular symmetry in the instruction set. It tried to use an addressing m

The only error I found where the code compiled but was wrong was from it assuming a particular symmetry in the instruction set. It tried to use an addressing mode on an instruction that didn't support it and consequently output two completely different instructions. Errors in the run-time library and errors that crash the compiler are much more common. While many eyes cover a lot of search space. The space they have to cover has grown immensely. If you step off the trodden path you can find problems much more often. Just recently I encountered a function in a run-time library that freed the amount of memory the alloc asked for instead of the amount of memory the alloc function actually returned (Sometimes it returned slightly more if the remaining space was not enough to hold a free-memory structure). It would not surprise me if the population using that particular compiler/platform combination numbered less than a thousand.