Bad array indexing is considered deadly

[Arafel via Digitalmars-d]

On 06/02/2017 02:12 PM, Steven Schveighoffer wrote:
>> Perhaps an intermediate solution would be to offer a compiler switch
>> that allows Errors to be safely caught (that is, they behave as
>> exceptions). As far as I understand from reading this thread, that's
>> already the case in debug builds, so it cannot be that bad practice, but
>> it would be nice to have a mode that it's otherwise "release", only with
>> this feature turned on.
> 
> I don't think this is workable, simply because of nothrow. An Error is 
> allowed to be thrown in nothrow code, and the compiler can 
> simultaneously assume that nothrow functions won't throw. Therefore it 
> can legally omit the scaffolding for deallocating scope variables when 
> an Exception is thrown (for performance reasons), and leave your program 
> in an invalid state.
> 

Well, as I understood from this thread this is already possible in debug 
mode:

> An Exception leads to unwinding&cleanup, an Error to termination (with unwinding&cleanup in debug mode for debugging purposes).

If it is indeed so, then adding a switch that only removes this 
optimization (from @nothrow code) but is otherwise a release version 
shouldn't be too hard to implement? Even if not, making @nothrow a no-op 
w.r.t. unwinding should still be possible and not too hard (sorry if I'm 
being naïve here, I don't know how hard it would be to implement, but 
conceptually it seems straightforward).

Of course, one must be willing to take the performance hit.