# VST3 Host initialization sequence

**URL:** <https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586>\
**Category:** VST 3 SDK\
**Created:** [November 20, 2025, 8:09pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586 "2025-11-20T20:09:39Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![Russell\_Colombo](https://avatars.discourse-cdn.com/v4/letter/r/74df32/32.png) [@Russell\_Colombo](https://forums.steinberg.net/u/Russell_Colombo)\
**Post date:** [November 20, 2025, 8:09pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/1 "2025-11-20T20:09:39Z")

</div>

I’m hoping someone can help me figure this out. I no longer have any hair.

I’ve created a VST Host DLL for our audio application, but I’m not sure I have the initialization sequence correct. Some plugins don’t load correctly, and other will crash.

The following is the diagnostic output from my load routine for 2 differnt plugins. The first seems to load correctly, but the second crashes:

20-11-25 13:49:21.94 Calling Module::create for **bx\_console SSL 4000 E**  
20-11-25 13:49:21.94 Module create success  
20-11-25 13:49:21.94 Calling factory.createInstance to create component  
20-11-25 13:49:21.94 Component creation success  
20-11-25 13:49:21.94 calling component-\>initialize  
20-11-25 13:49:22.02 component-\>initialize → 0  
20-11-25 13:49:22.02 creating IAudioProcessor from component  
20-11-25 13:49:22.02 processor creation success  
20-11-25 13:49:22.02 creating controller from component  
20-11-25 13:49:22.02 controller-\>setComponentHandler → 0  
20-11-25 13:49:22.02 isSingleComponent == true. controller ↔ component connection not required  
20-11-25 13:49:22.02 Creating editor view  
20-11-25 13:49:22.02 editor view creation success  
20-11-25 13:49:22.02 Setting bus arrangements.  
20-11-25 13:49:22.02 processor-\>setBusArrangements failed → 1.  
20-11-25 13:49:22.02 processor-\>setupProcessing → 0  
20-11-25 13:49:22.02 activateBus input → 0  
20-11-25 13:49:22.02 activateBus output → 0  
20-11-25 13:49:22.02 component-\>setActive → 0.  
20-11-25 13:49:22.02 processor-\>setProcessing → 0.  
20-11-25 13:49:22.02 BusCount in=2 out=1  
20-11-25 13:49:22.02 Loading saved Plugin settings  
20-11-25 13:49:22.02 Plugin latency is 0 samples

20-11-25 13:59:21.94 Calling Module::create for **Ozone 11 Equalizer**  
20-11-25 13:59:21.94 Module create success  
20-11-25 13:59:21.94 Calling factory.createInstance to create component  
20-11-25 13:59:21.94 Component creation success  
20-11-25 13:59:21.94 calling component-\>initialize  
20-11-25 13:59:22.02 component-\>initialize → 0  
20-11-25 13:59:22.02 creating IAudioProcessor from component  
20-11-25 13:59:22.02 processor creation success  
20-11-25 13:59:22.02 creating controller from component  
20-11-25 13:59:22.02 controller-\>setComponentHandler → 0  
20-11-25 13:49:22.02 Connecting controller ↔ component  
20-11-25 13:49:22:02 **Exception thrown in Ozone 11 Equalizer. Access violation reading location 0x0000000000000000.**

Any help is greatly appreciated.

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<div class="post-metadata">

**Author:** ![Yvan](https://dub1.discourse-cdn.com/steinberg/user_avatar/forums.steinberg.net/yvan/32/51177_2.png) [@Yvan](https://forums.steinberg.net/u/Yvan)\
**Post date:** [November 27, 2025, 10:46am UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/2 "2025-11-27T10:46:01Z")

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> [@Russell\_Colombo](#):
>
> calling component-\>initialize

are you calling controller-\>initialize ?

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<div class="post-metadata">

**Author:** ![Russell\_Colombo](https://avatars.discourse-cdn.com/v4/letter/r/74df32/32.png) [@Russell\_Colombo](https://forums.steinberg.net/u/Russell_Colombo)\
**Post date:** [November 27, 2025, 3:14pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/3 "2025-11-27T15:14:17Z")

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```auto
Yvan,
When the controller is created from the factory using classID, it crashes when connecting component <-> controller below.
When the controller is created from the component, it always returns 1 (fail).

Here's the code:

	// --- Create controller
	TRACE(_T("Getting controller from classID\n"));
	TUID ctrlTuid = { 0 };
	if (component->getControllerClassId(ctrlTuid) == kResultOk)
	{
		TRACE(_T("calling factory.createInstance to create controller\n"));
		controller = factory.createInstance<IEditController>(ctrlTuid);
	}

	if (!controller)
	{
		TRACE(_T("creating controller from component\n"));
		controller = FUnknownPtr<IEditController>(component);
		isSingleComponent = true;
	}

	if (controller)
	{
		TRACE("Calling controller->initialize\n");
		status = controller->initialize(hostCtx);
		TRACE(_T("controller->initialize -> %d\n"), status);

		TRACE(_T("Setting controller Component Handler\n"));
		status = controller->setComponentHandler(&componentHandler);
		TRACE(_T("controller->setComponentHandler -> %d\n"), status);
	}

	try
	{
		// --- Connect controller <-> component
		if (!isSingleComponent)
		{
			TRACE(_T("Connecting controller <-> component\n"));
			compCP = FUnknownPtr<Steinberg::Vst::IConnectionPoint>(component);
			ctrlCP = FUnknownPtr<Steinberg::Vst::IConnectionPoint>(controller);
			if (compCP && ctrlCP)
			{
====> status = compCP->connect(ctrlCP);
				TRACE(_T("compCP->connect -> %d\n"), status);
				status = ctrlCP->connect(compCP);
				TRACE(_T("ctrlCP->connect -> %d\n"), status);
			}
		}
	}
	catch (...)
	{
		TRACE("Connect controller <-> component");
	}

```

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<div class="post-metadata">

**Author:** ![Yvan](https://dub1.discourse-cdn.com/steinberg/user_avatar/forums.steinberg.net/yvan/32/51177_2.png) [@Yvan](https://forums.steinberg.net/u/Yvan)\
**Post date:** [November 28, 2025, 7:47am UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/4 "2025-11-28T07:47:50Z")

</div>

Did you try the audiohost example provided by the SDK?

check public.sdk/source/vst/hosting/plugprovider.cpp for setupPlugin where a plugin in initialized…

check type for component and controller, order of calling….

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<div class="post-metadata">

**Author:** ![Russell\_Colombo](https://avatars.discourse-cdn.com/v4/letter/r/74df32/32.png) [@Russell\_Colombo](https://forums.steinberg.net/u/Russell_Colombo)\
**Post date:** [December 2, 2025, 4:01pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/5 "2025-12-02T16:01:07Z")

</div>

Yvan, Thanks for the info. I made the changes you suggested and I’m still crashing inside connectionproxy.cpp here: **tresult res = srcConnection→connect(this);**

New source code below.

Thanks for your help, Russ…

```auto
  // create component (IComponent)
  TRACE("Calling factory.createInstance to create component\n");
  component = factory.createInstance<IComponent>(procInfo->ID());
  if (!component)
  {
     TRACE("Failed to create component instance -> %d\n", status);
     return false;
  }

  TRACE("Component creation success\n");

  // Initialize the component with your host context
  TRACE(_T("calling component->initialize\n"));
  hostCtx = new MyHostApp();

  if (auto plugBase = U::cast<IPluginBase>(component))
  {
     status = plugBase->initialize(hostCtx);
     if (status != kResultOk)
     {
        TRACE(_T("Failed to initialize component\n"));
        return false;
     }
  }
  else
  {
     TRACE(_T("Failed to get IPluginBase from component\n"));
     return false;
  }

  TRACE("Getting controller from classID\n");
  TUID ctrlTuid = { 0 };
  // try to create the controller part from the component
  // (for Plug-ins which did not succeed to separate component from controller)
  if (component->queryInterface(IEditController::iid, (void**)&controller) == kResultTrue)
  {
     isSingleComponent = true;
  }
  else
  {
     // ask for the associated controller class ID
     if (component->getControllerClassId(ctrlTuid) == kResultTrue)
     {
        // create its controller part created from the factory
        controller = factory.createInstance<IEditController>(VST3::UID(ctrlTuid));
        if (controller)
        {
           // initialize the component with our context
           if (auto plugCtrlBase = U::cast<IPluginBase>(controller))
           {
              status = plugCtrlBase->initialize(hostCtx);
              if (status != kResultOk)
              {
                 TRACE(_T("Failed to initialize controller!\n"));
              }
           }
           else
           {
              TRACE(_T("Failed to get IPluginBase from controller\n"));
              return false;
           }
        }
     }
     else
     {
        TRACE(_T("Component does not provide a required controller class ID\n"));
     }
  }

  if (status != kResultOk)
  {
     component.reset();
     controller.reset();
  } 
  else
  {
     // --- Connect controller <-> component
     if (!isSingleComponent)
     {
        if (component && controller)
        {
           TRACE("Connecting controller <-> component\n");
           //auto compICP = U::cast<IConnectionPoint>(component);
           //auto contrICP = U::cast<IConnectionPoint>(controller);
           FUnknownPtr<Steinberg::Vst::IConnectionPoint> compICP{ nullptr };
           FUnknownPtr<Steinberg::Vst::IConnectionPoint> contrICP{ nullptr };
           compICP = FUnknownPtr<Steinberg::Vst::IConnectionPoint>(component);
           contrICP = FUnknownPtr<Steinberg::Vst::IConnectionPoint>(controller);
           if (!compICP || !contrICP)
              return false;

           componentCP = owned(new ConnectionProxy(compICP));
           controllerCP = owned(new ConnectionProxy(contrICP));

           status = componentCP->connect(contrICP);
           if (status != kResultTrue)
           {
              TRACE("componentCP->connect -> %d\n", status);
              return false;
           }
           status = controllerCP->connect(compICP);
           if (status != kResultTrue)
           {
              TRACE("controllerCP->connect -> %d\n", status);
              return false;
           }
        }
     }
  }

```

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<div class="post-metadata">

**Author:** ![Yvan](https://dub1.discourse-cdn.com/steinberg/user_avatar/forums.steinberg.net/yvan/32/51177_2.png) [@Yvan](https://forums.steinberg.net/u/Yvan)\
**Post date:** [December 3, 2025, 2:17pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/6 "2025-12-03T14:17:12Z")

</div>

Did you try the audiohost example provided by the SDK?

Does it generate the crash?

---

<div class="post-metadata">

**Author:** ![Russell\_Colombo](https://avatars.discourse-cdn.com/v4/letter/r/74df32/32.png) [@Russell\_Colombo](https://forums.steinberg.net/u/Russell_Colombo)\
**Post date:** [December 3, 2025, 3:33pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/7 "2025-12-03T15:33:05Z")

</div>

Yes I did. It crashes as well. That’s why I abandoned the PlugProvider and used the code above.

---

<div class="post-metadata">

**Author:** ![Russell\_Colombo](https://avatars.discourse-cdn.com/v4/letter/r/74df32/32.png) [@Russell\_Colombo](https://forums.steinberg.net/u/Russell_Colombo)\
**Post date:** [December 29, 2025, 8:19pm UTC](https://forums.steinberg.net/t/vst3-host-initialization-sequence/1015586/8 "2025-12-29T20:19:08Z")

</div>

Any chance I can get source code for the VST3 Plugin Test Host app to compare ?