WeakReferenceable: Return NULL in GetReference if the pointer is gone.

Fixes a major API footgun that caused #18759.

WeakReferenceable: Clear fUseCount when it is 1.

Otherwise, if there are remaining weak references, they could
potentially try to acquire the object and trigger a use-after-free.

BPrivate::WeakReferenceable: Move implementation to a .cpp.

No functional change to the implementation, just getting it
out of a header.

kernel: atomic_*() functions rework

* No need for the atomically changed variables to be declared as
volatile.
* Drop support for atomically getting and setting unaligned data.
* Introduce atomic_get_and_set[64]() which works the same as
atomic_set[64]() used to. atomic_set[64]() does not return the
previous value anymore.

Style fixes. Thanks Axel and Ingo.

Make BReference and BWeakReference behave more like a normal pointer.
* Casts like BReference<Derived> to BReference<Base> are now possible.
* This cast for BWeakReference is, because of the underlying structure, not automatically type safe. I used a simple hack to make the compiler complain if the cast
is not type safe. Please take a look if that can be done better.
* Smaller style and bug fixes.

Use nothrow and add InitCheck method to check if allocation went fine.



git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42765 a95241bf-73f2-0310-859d-f6bbb57e9c96

New BWeakReferenceable API.



git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42763 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Removed the obsolescent [B]Reference[able] API and replaced the remaining
uses. Fixes the gcc 2 acpi build.
* Renamed WeakReferenceable::{Add,Remove}Reference() to
{Acquire,Release}Reference() for consistency.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39871 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Made _GetUnchecked() return nothing, as it was ignored anyway.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@30359 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Made the WeakReferenceable class templatized. Not really sure yet I like that
better, though :-)
* Also fixed a mixup of the unintuitive argument order of our
atomic_test_and_set(); I guess I will change that sooner or later.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29994 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Added a WeakReferenceable implementation, completely untested yet.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29990 a95241bf-73f2-0310-859d-f6bbb57e9c96

kernel: atomic_*() functions rework

* No need for the atomically changed variables to be declared as
volatile.
* Drop support for atomically getting and setting unaligned data.
* Introduce atomic_get_and_set[64]() which works the same as
atomic_set[64]() used to. atomic_set[64]() does not return the
previous value anymore.

Style fixes. Thanks Axel and Ingo.

Make BReference and BWeakReference behave more like a normal pointer.
* Casts like BReference<Derived> to BReference<Base> are now possible.
* This cast for BWeakReference is, because of the underlying structure, not automatically type safe. I used a simple hack to make the compiler complain if the cast
is not type safe. Please take a look if that can be done better.
* Smaller style and bug fixes.

Use nothrow and add InitCheck method to check if allocation went fine.



git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42765 a95241bf-73f2-0310-859d-f6bbb57e9c96

New BWeakReferenceable API.



git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42763 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Removed the obsolescent [B]Reference[able] API and replaced the remaining
uses. Fixes the gcc 2 acpi build.
* Renamed WeakReferenceable::{Add,Remove}Reference() to
{Acquire,Release}Reference() for consistency.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39871 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Made _GetUnchecked() return nothing, as it was ignored anyway.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@30359 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Made the WeakReferenceable class templatized. Not really sure yet I like that
better, though :-)
* Also fixed a mixup of the unintuitive argument order of our
atomic_test_and_set(); I guess I will change that sooner or later.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29994 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Added a WeakReferenceable implementation, completely untested yet.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29990 a95241bf-73f2-0310-859d-f6bbb57e9c96