Btukfyl

When creating a new Windows Service in Delphi, it inserts the following:

if not Application.DelayInitialize or Application.Installing then

  Application.Initialize;

The author didn't bother including parentheses, so I'm trying to wrap my head around this. It translates to:

if (not Application.DelayInitialize) or Application.Installing then

  Application.Initialize;

From what I understand, if both Application.DelayInitialize and Application.Installing are True, then it will go ahead and Initialize the service application. I don't understand why it would be initialized in this scenario - I'm pretty sure it shouldn't be initialized.

Can someone give me some clarification what I'm looking at here?

On a side note, I would never need to enable DelayInitialize as there's no need to be concerned with Server 2003. I would just like to understand what this code is actually meant to do the way it's written.

As the comment inserted in the project source when you create a service application explains, DelayInitialize exists for a specific reason: the requirement to call StartServiceCtrlDispatcher before CoRegisterClassObject. Whether you would need to set it or not, I presume, would really depend on if you need to call CoRegisterClassObject, not if you're targeting server 2003 or not ^(*). IOW, I wouldn't expect that comment to be updated with every new server version. YMMV, testing might be required.

The implied design here is that you use System.InitProc to call CoRegisterClassObject ^(**), similar to how the CoInitializeEx call is made by ComObj.pas. InitProc is called from Vcl.Forms.Application.Initialize which is called from Vcl.SvcMgr.TServiceApplication.Initialize.

Now, when Vcl.SvcMgr.TServiceApplication.Installing returns true, that means StartServiceCtrlDispatcher will not to be called. Because the main thread is not going to connect with the service control manager. Instead it will either install or uninstall services and then exit. Then the need for any delayed initialization will become void and in fact a delayed initialization cannot run since no service thread will run ^(***).

And so this is why the expression is written the way it is, there are no forgotten/missing parenthesis.

^{(*) D2007 has the comment at which time 2003 R2 is the last server.}

^{(**) From the comment in the project source:}

^{Windows 2003 Server requires StartServiceCtrlDispatcher to be called before CoRegisterClassObject, which can be called indirectly by Application.Initialize.}

^{(***) This is where a delayed initialization is called, guarded by a flag in case there is more than one service in the executable.}