On 7/26/17 7:28 PM, Moritz Maxeiner wrote:
On Wednesday, 26 July 2017 at 22:33:23 UTC, Steven Schveighoffer wrote:
On 7/26/17 2:33 PM, Moritz Maxeiner wrote:
On Wednesday, 26 July 2017 at 17:38:28 UTC, Dgame wrote:
I don't get it. The GC collects the objects which aren't in use
anymore. The order in which this is currently happening is not
specified. So, how are the destructors supposed to be called in the
right order? Manually? ARC?
After the split:
Destructors are only for deterministic end of object lifetime, so
yes, they are to be called by any scheme (such as manual management
via destroy and reference counting - which is likely also implemented
as calling destroy) that is deterministic.
Finalizers are for nondeterministic schemes such as the GC.
The GC *never* calls destructors directly, only finalizers.
A finalizer might manually call a destructor, but a destructor may
never call a finalizer.
Actually, it's the opposite.
It's a matter of definition and this is the behaviour I would define,
because
A finalizer can never call anything on its members because it doesn't
know if it's being destroyed by the GC.
This falsely assumes that all members point into the GC pool.
Yes, I should have qualified GC members.
A
finalizer may freely work on non-pointer members and pointer members
that target objects outside the GC pool which the programmer knows to be
valid at finalization (e.g. they are manually managed).
Whether or not it makes sense for the finalizer to call the destructor
is something the programmer has to decide on a per use case basis.
No, because a destructor can safely assume it can look at GC members'
data. So a finalizer can never call it.
The destructor is ensured that the entire structure is intact, so it
can do whatever it wants.
The point is that I saw (and see) no reason for a destructor to ever
call a finalizer.
An example:
class File
{
int fd;
ubyte[] buffer;
// avoiding bikeshed issues by using clear names
destructor() { finalizer(); delete buffer; }
finalizer() { close(fd); }
}
No reason to repeat the finalizer code in the destructor.
-Steve
