Re: Preventing type extensions

[Florian Weimer <fw@deneb.enyo.de>]

* Ludovic Brenta:

> Another area where Ada helps certification is where it distinguishes
> pool-specific from general access types.  C and C++ are both completely
> helpless in this respect.  Consider:
>
> type T_Access is access T'Class; -- no equivalent in C++
> type T_General_Access is access all T'Class; -- equivalent to T* in C++

Iterators are examples of pool-specific allocators in C++.  It's also
common to define your own pointer types in C++.  It's hard to beat the
C++ type system in terms of expressiveness.

> Hey, just a wild idea: how about
>
> type T_Stack_Access is access aliased T;
>
> which indicates that access values of this type can *only* designate
> aliased objects that are on the stack, and never on the heap?

I don't think this would provide useful information.  Tasks blur the
boundary between heap and stack allocation.