Before the application terminates its execution, COM must be shut down again. (Failure to shut down COM could result in execution errors when another program attempts to use COM services .)
The above quote implies that,right?
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23answers:
2
+1
A:
No it doesn't.
If you fail to properly release all references to an out of process COM server and correctly close down COM it could lead to that instance of that service being in an odd state (everything should be OK after releasing all references, but sometimes COM might cache part of the out of process marshalling layer).
An out of process COM service can be designed to have separate component instances for each client (within or across services) that are completely independent (even if hosted in the same process), in which case it is hard to see how a failure of one client would affect other instances (other than wasting memory on instances until COM finally times them out). If the instances share state they can of course interfere even if the clients operate perfectly to the rules.
Richard
2010-08-26 09:26:46
Can a COM service have a unique instance for all clients?
COMer
2010-08-26 09:34:38
@COMer if you mean a singtleton instance (i.e. there is only ever one instance, whether 1 or 1000 clients): Yes. You need to override the instance factory (to do this depends on how you are creating the COM component, and some tools may not have sufficient flexibility to do it).
Richard
2010-08-26 10:07:24
+1
A:
It is rather important that you quote the source of that quote so we can get the context. As near as I can see, you got that from a book about DirectShow programming. What it actually refers to is the need to call CoUninitialize().
Yes, that's kinda important. A thread should call CoInitializeEx() to initialize the COM infrastructure before it starts using any of the COM API functions. You really should call CoUninitialize() when that threads ends so stuff is properly cleaned up. Typically at the end of your program's main() function. Failure to do so may make another app fail when it finds a register class factory that in fact is dead.
This otherwise has nothing to do with a COM out-of-process server having to restrict itself in any way. You specify sharing mode with the REGCLS argument to CoRegisterClassObject(). Of course, a server should not exit and call CoUninitialize until all its objects are released.
Hans Passant
2010-08-26 16:16:03