IUnknown::AddRef method (unknwn.h)

Increments the reference count for an interface pointer to a COM object. You should call this method whenever you make a copy of an interface pointer


ULONG AddRef();

Return value

The method returns the new reference count. This value is intended to be used only for test purposes.


A COM object uses a per-interface reference-counting mechanism to ensure that the object doesn't outlive references to it. You use AddRef to stabilize a copy of an interface pointer. It can also be called when the life of a cloned pointer must extend beyond the lifetime of the original pointer. The cloned pointer must be released by calling IUnknown::Release on it.

The internal reference counter that AddRef maintains should be a 32-bit unsigned integer.

Notes to callers

Call this method for every new copy of an interface pointer that you make. For example, if you return a copy of a pointer from a method, then you must call AddRef on that pointer. You must also call AddRef on a pointer before passing it as an in-out parameter to a method; the method will call IUnknown::Release before copying the out-value on top of it.


Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header unknwn.h

See also