More radical ideas about gc and reference counting

[Walter Bright via Digitalmars-d]

On 5/11/2014 5:52 AM, Michel Fortin wrote:
> On 2014-05-11 08:29:13 +0000, Walter Bright <newshound2 at digitalmars.com> said:
>
>> Again, O-C and C++/CX ARC are not memory safe because in order to make it
>> perform they provide unsafe escapes from it.
>
> But D could provide memory-safe escapes. If we keep the current GC to collect
> cycles, we could also allow raw pointers managed by the GC alongside ARC.
>
> Let's say we have two kinds of pointers: rc+gc pointers (the default) and
> gc_only pointers (on demand). When assigning from a rc+gc pointer to a gc_only
> pointer, the compiler emits code that disables destruction via the reference
> counting. This makes the GC solely responsible for destructing and deallocating
> that memory block. You can still assign the pointer to a rc+gc pointer later on,
> but the reference count is no longer reliable which is why RC-based destruction
> has been disabled.

Yes, you can make it memory safe by introducing another pointer type, as Rust 
does. But see my comments about this scheme in the message you replied to.

(Yes, I understand your proposal is a variation on that scheme.)