Bug in RefCounted?

[monarch_dodra]

On Sunday, 27 October 2013 at 21:02:01 UTC, Rene Zwanenburg wrote:
> On Thursday, 24 October 2013 at 16:46:37 UTC, Ali Çehreli wrote:
>> Technically, it is a problem with FooWrapper. Regardless of 
>> whether RefCounted's behavior, by default, structs in D are 
>> freely copyable and movable value types. The compiler can do 
>> those things as it sees fit.
>>
>> Since FooWrapper owns a resource, it must also define the 
>> post-blit to make a copy of Foo.
>>
>> (As an aside, dmd at git head does not make such a copy.)
>>
>> Ali
>
> Thanks, that's indeed an oversight on my part. Still, I think 
> there's something strange going on.
>
> The problem is that the FooWrapper destructor is called twice, 
> one time with a garbage foo pointer. The example prints:
> Destroying Foo 40CED748
> Destroying Foo 4002DFF0
> There is only one Foo instance created. A null pointer would 
> make sense, but where's that second pointer coming from?

This is indeed strange. I don't have access to my development
platform, but it *could* be an (older) emplace bug. Do you
reproduce with head? I'll investigate further as soon as I can.
This is not normal behavior.

Also, keep in mind that DMD *is* allowed to destroy the same
object several times. YOur destructor should look like this:
~this()
{
      if (foo)
          destroyFoo(foo);
      foo = null;
}

This doesn't explain what you are seeing, but keep it in mind.