Re: CoInitialize/CoUninitialize

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 30 Jun 2008 13:13:33 +0200

Message-ID:

<3qednWbwtcR8IvXVnZ2dnUVZ_ojinZ2d@posted.comnet>

* George:

Thanks Alf,

1.

I have to set manually ole32!CoInitialize, or else if I only type
CoInitialize, WinDbg will think the function resides in Kernel32.dll, and
will never stop on the breakpoint, even if it is called.

Do you think it is a bug of WinDbg?

I think you're concentrating on entirely the wrong thing.

2.

"You don't want to call CoInitialize/CoUninitialize locally anywhere, because
that doesn't work with e.g. Internet Explorer machinery." and "Don't rely on
any local calls." -- could you say the comments in some other words please?
Sorry, my English is not good.

Here is bad code, relying on local COM initialization:

   void doAnHTMLDialog()
   {
       if( !SUCCEEDED( CoInitialize() ) )
       {
           throwX( "Unable to initalize COM" );
       }

       // Do HTML dialog using COM-based IE machinery, then

       CoUninitialize();
       // Dontcha know, there might still be some thread using COM! Splat!
   }

   int main()
   {
       doAnHTMLDialog();
       // Perhaps do other things here, then:
       return EXIT_SUCCESS;
   }

Here is less bad code, which might even be counted as good if one ignores
exception safety aspects and lack of abstraction and reusability:

   void doAnHTMLDialog()
   {
       HRESULT const initResult = CoInitialize();
       if( FAILED( initResult ) )
       {
           throwX( "Unable to initalize COM" );
       }
       else if( initResult != S_OK )
       {
           CoUninitialize();
           throwX( "COM was not initialized before calling doAnHTMLDialog." );
       }
       CoUninitialize(); // "Undo" the checking call of CoInitialize.

       // Do HTML dialog using COM-based IE machinery.
   }

   int main()
   {
       if( !SUCCEEDED( CoInitialize ) ) { return EXIT_FAILURE; }
       doAnHTMLDialog();
       // Perhaps do other things here, then:
       CoUninitialize();

       return EXIT_SUCCESS;
       // It's unclear exactly why terminating the process never invokes fatal
       // errors and undefined behavior for still running COM things, but, in
       // practice it's always worked. It's about the best one /can/ do with
       // ugly bug-ridden MS library software that gives no means of waiting
       // for finished cleanup, or of forcing cleanup.
   }

Cheers, & hth.,

- Alf

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?