On 5/11/2014 5:52 AM, Michel Fortin wrote:
On 2014-05-11 08:29:13 +0000, Walter Bright <newshou...@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.)
