General activex dll multithreading clarification

[smkperu]

Hello Trick,

I wrote a simple multithreaded activex dll which can create its private objects in the new thread.
I can understand that it works when set to apartment threaded.
But I don't understand how it is able to create dll private objects in the new thread even when set to single threaded model without crashing.
Project attached. actx dll(myactsingle1) and std exe(myactsingle1use)

Thanks

[smkperu]

Hello Trick,

What is the mistake I have to correct in actxdllwithapt_threaded1 https://www.vbforums.com/attachment....5&d=1696428326
so that it can work similar to myactsingle1 of https://www.vbforums.com/attachment....7&d=1696260349 project in General-activex-dll-multithreading-clarification above.


Thanks

[The trick]

You shouldn't create objects from single-threaded dll in different threads.

[smkperu]

You shouldn't create objects from single-threaded dll in different threads.

Hello Trick,
Ok.
Still what I did'nt understand is that myactsingle1 of https://www.vbforums.com/attachment....7&d=1696260349 project in General-activex-dll-multithreading-clarification runs without crash even in single threaded mode.How it is possible.

When compared both actxdllwithapt_threaded1 https://www.vbforums.com/attachment....5&d=1696428326 and myactsingle1 of https://www.vbforums.com/attachment....7&d=1696260349 are similar activex projects using same logic
and single threaded.I compared both project files (.vbp) and could not notice any difference.

Thanks

[smkperu]

Hello Trick,
Ok.
Still what I did'nt understand is that myactsingle1 of https://www.vbforums.com/attachment....7&d=1696260349 project in General-activex-dll-multithreading-clarification runs without crash even in single threaded mode.How it is possible.

When compared both actxdllwithapt_threaded1 https://www.vbforums.com/attachment....5&d=1696428326 and myactsingle1 of https://www.vbforums.com/attachment....7&d=1696260349 are similar activex projects using same logic
and single threaded.I compared both project files (.vbp) and could not notice any difference.

Thanks

Hello Trick,

After deep debugging I identified the problem is

using App object in Form1.frm of actxdllwithapt_threaded project at https://www.vbforums.com/attachment....5&d=1696428326.

Private Sub Form_Load()
Me.Caption = App.ThreadID
End Sub


I corrected it by using GetCurrentThreadId API instead of App.ThreadID ie., by not using App object.

Is there any way to use the App object directly in new thread without crash in activex dll(single threaded).


Thanks

[smkperu]

Hello Trick,

After deep debugging I identified the problem is

using App object in Form1.frm of actxdllwithapt_threaded project at https://www.vbforums.com/attachment....5&d=1696428326.

Private Sub Form_Load()
Me.Caption = App.ThreadID
End Sub


I corrected it by using GetCurrentThreadId API instead of App.ThreadID ie., by not using App object.

Is there any way to use the App object directly in new thread without crash in activex dll(single threaded).


Thanks

Hello Trick,

1. it is possible to access App object in new thread

in standard exe in any new thread when runtime is initialized in ThreadProc as follows from modMultithreading2.bas using vbCreateThread in https://www.vbforums.com/showthread....n-Standart-EXE

' // Initialize runtime for new thread and run procedure
Private Function ThreadProc( _
                 ByVal pParameter As Long) As Long
    Dim cExpSrv     As IUnknown
    Dim bIsInIDE    As Boolean
    Dim tClsId      As tCurGUID
    Dim tIID        As tCurGUID
    Dim tThreadData As tThreadData
    Dim hHeap       As Long
    Dim pNewHeader  As Long
    
    Debug.Assert MakeTrue(bIsInIDE)
    
    If Not bIsInIDE Then
        Set cExpSrv = CreateIExprSrvObj(0, 4, 0)
    End If
    
    CoInitialize ByVal 0&
    
    hHeap = GetProcessHeap()
    
    TlsSetValue lTlsSlot, ByVal pParameter
    
    GetMem8 ByVal pParameter, tThreadData

    If bIsInIDE Then
        FakeMain
    Else
        
        pNewHeader = CreateVBHeaderCopy()
        
        If pNewHeader Then
        
            tIID.c2 = 504403158265495.5712@

            VBDllGetClassObject hModule, 0, pNewHeader, tClsId, tIID, 0

            ' // Becasue of a header will be used by MSVBVM60 in DllMain (with DLL_THREAD_DETACH)
            ' // we can't free it now. To avoid memory leak we will free it later
            
        End If
        
    End If
    
    GetMem8 ByVal pParameter, tThreadData
    
    ThreadProc = tThreadData.lpParameter
    
    HeapFree hHeap, 0, pParameter

    CoUninitialize
    
End Function

2. it is possible to access App object in new thread as follows

 // Initialize App object
        lUnused = App.ThreadID

in standard dll in any new thread when we use as follows from modDllInitialize.bas in https://www.vbforums.com/attachment....7&d=1578834223

' // Initilaize the runtime
Public Function InitializeRuntimeForProject( _
                ByVal hInstance As Long, _
                ByVal bIsFirst As Boolean) As Boolean
    Dim pNewHeader  As Long
    Dim tClsId      As tCurGUID
    Dim tIID        As tCurGUID
    Dim lUnused     As Long
    
    pNewHeader = VBDll.TlsGetValue(mlTlsSlot)
    
    ' // Check if the module already initialized
    If pNewHeader Then

        InitializeRuntimeForProject = True
        Exit Function
        
    End If
    
    VBDll.CoInitialize ByVal 0&
    
    If mpVbHeader = 0 Then
        
        ' // Search for VBHeader (EXEPROJECTINFO)
        mpVbHeader = SearchForVbHeader(hInstance)
        If mpVbHeader = 0 Then Exit Function
        
        ' // Modify header
        ModifyVBHeader
        
    End If
    
    ' // Create the new copy of headers for new instance
    pNewHeader = CreateVBHeaderCopy()
    
    ' // Save it
    VBDll.TlsSetValue mlTlsSlot, ByVal pNewHeader

    If pNewHeader = 0 Then
        Exit Function
    End If
    
    ' // IID_IUnknown
    tIID.c2 = 504403158265495.5712@
    
    ' // Call CThreadPool::InitDllAccess
    VBDll.VBDllGetClassObject hInstance, 0, pNewHeader, tClsId, tIID, 0
    
    If bIsFirst Then
        ' // Initialize App object
        lUnused = App.ThreadID
    End If
    
    InitializeRuntimeForProject = True
    
End Function

When it is possible to use App object in new thread in 1. standard exe and 2. standard dll is there any similar method to make App object work in new thread in activex dll(single threaded).


Thanks

[xiaoyao]

where is modMultiThreading.Initialize?
can't find this code

[smkperu]

Hello Trick,

1. it is possible to access App object in new thread

in standard exe in any new thread when runtime is initialized in ThreadProc as follows from modMultithreading2.bas using vbCreateThread in https://www.vbforums.com/showthread....n-Standart-EXE

' // Initialize runtime for new thread and run procedure
Private Function ThreadProc( _
                 ByVal pParameter As Long) As Long
    Dim cExpSrv     As IUnknown
    Dim bIsInIDE    As Boolean
    Dim tClsId      As tCurGUID
    Dim tIID        As tCurGUID
    Dim tThreadData As tThreadData
    Dim hHeap       As Long
    Dim pNewHeader  As Long
    
    Debug.Assert MakeTrue(bIsInIDE)
    
    If Not bIsInIDE Then
        Set cExpSrv = CreateIExprSrvObj(0, 4, 0)
    End If
    
    CoInitialize ByVal 0&
    
    hHeap = GetProcessHeap()
    
    TlsSetValue lTlsSlot, ByVal pParameter
    
    GetMem8 ByVal pParameter, tThreadData

    If bIsInIDE Then
        FakeMain
    Else
        
        pNewHeader = CreateVBHeaderCopy()
        
        If pNewHeader Then
        
            tIID.c2 = 504403158265495.5712@

            VBDllGetClassObject hModule, 0, pNewHeader, tClsId, tIID, 0

            ' // Becasue of a header will be used by MSVBVM60 in DllMain (with DLL_THREAD_DETACH)
            ' // we can't free it now. To avoid memory leak we will free it later
            
        End If
        
    End If
    
    GetMem8 ByVal pParameter, tThreadData
    
    ThreadProc = tThreadData.lpParameter
    
    HeapFree hHeap, 0, pParameter

    CoUninitialize
    
End Function

2. it is possible to access App object in new thread as follows

 // Initialize App object
        lUnused = App.ThreadID

in standard dll in any new thread when we use as follows from modDllInitialize.bas in https://www.vbforums.com/attachment....7&d=1578834223

' // Initilaize the runtime
Public Function InitializeRuntimeForProject( _
                ByVal hInstance As Long, _
                ByVal bIsFirst As Boolean) As Boolean
    Dim pNewHeader  As Long
    Dim tClsId      As tCurGUID
    Dim tIID        As tCurGUID
    Dim lUnused     As Long
    
    pNewHeader = VBDll.TlsGetValue(mlTlsSlot)
    
    ' // Check if the module already initialized
    If pNewHeader Then

        InitializeRuntimeForProject = True
        Exit Function
        
    End If
    
    VBDll.CoInitialize ByVal 0&
    
    If mpVbHeader = 0 Then
        
        ' // Search for VBHeader (EXEPROJECTINFO)
        mpVbHeader = SearchForVbHeader(hInstance)
        If mpVbHeader = 0 Then Exit Function
        
        ' // Modify header
        ModifyVBHeader
        
    End If
    
    ' // Create the new copy of headers for new instance
    pNewHeader = CreateVBHeaderCopy()
    
    ' // Save it
    VBDll.TlsSetValue mlTlsSlot, ByVal pNewHeader

    If pNewHeader = 0 Then
        Exit Function
    End If
    
    ' // IID_IUnknown
    tIID.c2 = 504403158265495.5712@
    
    ' // Call CThreadPool::InitDllAccess
    VBDll.VBDllGetClassObject hInstance, 0, pNewHeader, tClsId, tIID, 0
    
    If bIsFirst Then
        ' // Initialize App object
        lUnused = App.ThreadID
    End If
    
    InitializeRuntimeForProject = True
    
End Function

When it is possible to use App object in new thread in 1. standard exe and 2. standard dll is there any similar method to make App object work in new thread in activex dll(single threaded).


Thanks

Hello Trick,

I got access to the App object in new thread in activex dll(single threaded) by just accessing it once in main thread in the same activex dll just as you showed in 2.standard dll.Thank you.

Having solved my App object problem can you tell me what are the
situations where activex dll(single threaded) crashes if we don't use
activex dll(apartment threaded) in new thread thru code.

Thanks

[smkperu]

Hello Trick,

In a activex dll in new thread we can create private objects of std exe (in which the activex dll is loaded) by using callbacks thru InitCurrentThreadAndCallFunction of modMultithreading2.bas in std exe.

How can we create the private objects of std exe in the loaded activex dll in its new thread without using callbacks of standard exe.

Thanks