Generic and fundamental language design issue

[deadalnix]

Le 04/11/2012 18:35, Tommi a écrit :
> I have a fundamental language design talking point for you. It's not
> specific to D. I claim that, most of the time, a programmer cannot, and
> shouldn't have to, make the decision of whether to allocate on stack or
> heap. For example:
>
> void func(T)()
> {
> auto t = <allocate T from heap or stack?>
> ...
> }
>
> The question of whether variable t should lay in heap or stack, depends
> not only on the sizeof(T), but also on the context in which func is
> called at. If func is called at a context in which allocating T on stack
> would cause a stack overflow, then t should be allocated from the heap.
> On the other hand, if func is called at a context where T still fits
> nicely on the stack, it would probably be better and faster to allocate
> t on stack.
>
> So, the question of whether to allocate that variable t on stack or heap
> is something that only the compiler (or runtime) can answer. Is there
> any language where you have the ability to say "allocate T from wherever
> it's best"?
>
> I wonder if it would be possible in D to let the compiler allocate
> dynamic arrays on stack when it can statically guarantee that it's safe
> to do so (no dangling references, never increasing the size of the
> array, etc).

BTW, Why can't we allocate 1Gb stack or something insanely big on 64bits 
systems ?

It will not use actual physical memory unless it is used, and much more 
stuffs can be allocated on stack.