On 24-05-2012 18:10, Andrei Alexandrescu wrote:
On 5/24/12 10:27 AM, deadalnix wrote:
Le 24/05/2012 16:54, Andrei Alexandrescu a écrit :
On 5/24/12 9:28 AM, Alex Rønne Petersen wrote:
The GC should (and probably does) assume at shutdown that all objects
are unreferenced, and therefore reclaim and finalize them.
They may refer to one another.
Andrei
So what ?
Each GC passes must, mark object that have to be removed, call finalizer
on them all, THEN recycle memory.
So « zombie » object can still refer to one another in finalization.
This is possible but not trivial as the state of zombie objects must be
properly defined. Often such objects will fail their invariant (a
reasonable state of a zombie object is with the correct vtable, no
mutex, and all fields in the pre-constructor state).
The real problem is resurrection, which should be 100% forbiden and this
must be enforced by the language (ie, the scopeness of this parameter is
something important).
As one aspect, calls to new should fail during destruction.
Andrei
Finalization happens once the world has been resumed, meaning GC
allocation (and even explicit deallocation) should be perfectly safe.
This is absolutely essential: Finalization models where finalizers run
in a paused world are doomed to fail miserably.
--
Alex Rønne Petersen
a...@lycus.org
http://lycus.org
