Bad array indexing is considered deadly

[Moritz Maxeiner via Digitalmars-d]

On Wednesday, 31 May 2017 at 22:47:38 UTC, Steven Schveighoffer 
wrote:
>
> Again, there has not been memory corruption.

Again, the runtime *cannot* know that and hence you *cannot* 
claim that. It sees an index out of bounds and it *cannot* reason 
about whether a memory corruption has already occurred or not, 
which means it *must assume* the worst case (it must *assume* 
there was).

> There is a  confusion rampant in this thread that preventing 
> *attempted* memory corruption must mean there *is* memory 
> corruption.

No, please no. Nobody has written that in the entire thread even 
once!
- An index being out of bounds is an error (lowercase!).
- The runtime sees that error when the array is accessed (what 
you describe as *attemped* memory corruption.
- The runtime does not know *why* the index is out of bounds
It does *not* mean that there *was* memory corruption (and again, 
nobody claimed that), but the runtime cannot assume that there 
was not, because that is *unsafe*.

> One  does not require the other.

Correct, but the runtime has to be safe in the *general* case, so 
it *must* assume the worst in case of a bug.