Just constructing one of these guys on the stack willy nilly will leak
the first reference to them. There might be other C_OBJECTs that have
public constructors, seems like a good place for some static analysis
checks :).
Force users to call the construct() method for it.
Previously, the Mixer class would only check for an added BufferQueue
if the list of active queues was empty. If more than one client
connected to AudioServer, its queue would never be added to the list of
active queues.
This fix adds a flag that, when set, will cause the sound thread to wait
for a new BufferQueue.
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
