Re: CoInitialize/CoUninitialize

From:

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

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 30 Jun 2008 13:15:49 +0200

Message-ID:

<3qednWHwtcT0XfXVnZ2dnUVZ_ojinZ2d@posted.comnet>

* Alf P. Steinbach:

* 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 )

Uh, "==".

      {
          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

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