On Tue, 10 Aug 2010 17:23:39 -0400, foobar <f...@bar.com> wrote:
Steven Schveighoffer Wrote:
On Tue, 10 Aug 2010 16:33:08 -0400, foo <f...@bar.com> wrote:
> In light on recent discussions of clear() and the distructor it seems
to
> me that we are going backwards from one of D's great improvements over
> C++ - the difference in semantics between structs and classes.
>
> IMO, instead of enhancing class desteructors they should be completely
> removed and only allowed on structs with deterministic semantics and
all
> uses cases of class desteructors should be replaced with structs.
> Examples:
> class SocketConnection : Connection {
> // struct instance allocated inline
> SocketHandle handle;
> ...
> }
>
> OR:
>
> class SocketConnection : Connection {
> struct {
> this() { acquireHandle(); }
> ~this() { releaseHandle(); }
> } handle;
> ...
> }
>
> The suggested semantics of the above code would be that creating a
> SocketConnection object would also construct a SocketHandle as part of
> the object's memory and in turn that would call the struct's ctor.
> On destruction of the object, the struct member would be also
destructed
> and it's d-tor is called. This is safe since the struct is part of the
> same memory as the object.
>
> in short, struct instances should be treated just like built-in types.
>
That doesn't help. deterministic destruction is not a struct-vs-class
problem, its a GC-vs-manual-memory problem. A struct on the heap that
is
finalized by the GC has the same issues as a class destructor. In fact,
struct destructors are not currently called when they are heap-allocated
because the GC has no idea what is stored in those memory locations.
-Steve
Let me add to the above, that the GC should NOT manage structs allocated
on the heap. structs should only provide deterministic semantics.
So either you are saying that structs that are in classes are never
destroyed, and you have a resource leak, or every class has an
auto-generated destructor that calls the struct destructors, and we have
the same determinism problem you purport to solve. If a struct is in a
class, it's on the heap. You have not solved the problem.
-Steve
