AddRef and Release function of COM inteface

[Guest]

Hello everyone,


I have noticed a lot of COM samples that the function AddRef and Release
function of COM inteface is not synchronized to make it thread safe when
dealing with adding/decreasing reference count.

Is it needed to synchronize AddRef and Release? Or the COM runtime
underlying implementation handles thread safe issue by itself (i.e.
transparent to upper layer COM server developer)

I am using Visual Studio 2005 to develop native (unmanaged C++) COM. No
other framework is used (e.g. ATL).


thanks in advance,
George

 

[Crest Teethgel]

Is it needed to synchronize AddRef and Release? Or the COM runtime

Yes.
Why and how are described in Don Box's Essential COM (p. 53)

 

[Guest]

Thanks Crest,


I want to confirm with you that you mean we need to add thread safe
synchronization approach to AddRef and Release to make counter value thread
safe manually by developers (i.e. COM runtime engine does not provide such
function)?


regards,
George

 

[Carl Daniel [VC++ MVP]]

Thanks Crest,


I want to confirm with you that you mean we need to add thread safe
synchronization approach to AddRef and Release to make counter value
thread safe manually by developers (i.e. COM runtime engine does not
provide such function)?

Yes, that's correct. AddRef/Release are typically implemented using
InterlockedIncrement and InterlockedDecrement.

-cd

 

[Ben Voigt [C++ MVP]]

Thanks Crest,


I want to confirm with you that you mean we need to add thread safe
synchronization approach to AddRef and Release to make counter value
thread
safe manually by developers (i.e. COM runtime engine does not provide such
function)?

*If* you mark your component with the single-threaded or apartment threading
model then you needn't worry.

Other threading models need to use InterlockedXYZ functions as Carl
mentioned.

 

[Guest]

Thanks for all of your help, cd!


regards,
George

 

[Guest]

Hi Ben,


I am interested to learn the basics of apartment thread model. Could you
recommend some learning materials?


regards,
George

 

[Guest]

http://www.codeproject.com/com/#COM

 

[Guest]

http://www.codeproject.com/com/#COM

 

[Guest]

Thanks Alex,


regards,
George

http://www.codeproject.com/com/#COM