[VB6] - Multithreading in VB6 part 2 - the creation of Native DLL.

[The trick]

Get the address of "UserDllMain" is very simple, because we know the handle of the library (it is passed as the first parameter); call "GetProcAddress" and get the address "DllGetClassObject". Next, we obtain the values through "GetMem4". I want to note that all API functions must be declared in a type library for this I compiled "DllInitialize.tlb", after compiling it does not need. To call "VBDllGetClassObject" use as "IID - IUnknown", as "CLSID - IID_NULL". Also, for initialization "COM" function must be called "CoInitialize". If we now try to collect a DLL, it will work, but keep in mind that the first call "VBDllGetClassObject" all unit variables are initialized to default values. Therefore it is necessary to call derived variables stored in local variables, and then it is already possible to maintain a modular. You also need to consider the threading model of the project: to "Apartment", as a function of "DllMain" should not be appeals to modular variables. For both models, I created two modules:
For single threaded:

' modMainDLL.bas  - инициализация DLL (Single thread)
' © Кривоус Анатолий Анатольевич (The trick), 2014

Option Explicit

Private Type uuid
    data1       As Long
    data2       As Integer
    data3       As Integer
    data4(7)    As Byte
End Type

Public hInstance    As Long

Private lpInst_     As Long
Private lpUnk_      As Long
Private lpVBHdr_    As Long

' Точка входа
Public Function DllMain(ByVal hInstDll As Long, ByVal fdwReason As Long, ByVal lpvReserved As Long) As Long
    Dim lpProc      As Long
    Dim lpInst      As Long
    Dim lpUnk       As Long
    Dim lpVBHdr     As Long
    
    ' При создании процесса инициализируем адреса нужных переменных
    If fdwReason = DLL_PROCESS_ATTACH Then
        ' Получаем нужные нам данные, VBHeader, и два указателя необходимых для инициализации
        lpProc = GetProcAddress(hInstDll, "DllGetClassObject")
        If lpProc = 0 Then Exit Function
        GetMem4 ByVal lpProc + 2, lpVBHdr
        GetMem4 ByVal lpProc + 7, lpUnk
        GetMem4 ByVal lpProc + 12, lpInst
        DllMain = InitRuntime(lpInst, lpUnk, lpVBHdr, hInstDll, fdwReason, lpvReserved)
        lpInst_ = lpInst: lpUnk_ = lpUnk: lpVBHdr_ = lpVBHdr: hInstance = hInstDll
    ElseIf fdwReason = DLL_THREAD_ATTACH Then
        DllMain = InitRuntime(lpInst_, lpUnk_, lpVBHdr_, hInstDll, fdwReason, lpvReserved)
    Else
        vbCoUninitialize
        DllMain = UserDllMain(lpInst_, lpUnk_, hInstDll, fdwReason, ByVal lpvReserved)
    End If
    
End Function

Private Function InitRuntime(ByVal lpInst As Long, ByVal lpUnk As Long, ByVal lpVBHdr As Long, ByVal hInstDll As Long, _
                             ByVal fdwReason As Long, ByVal lpvReserved As Long) As Long
    Dim iid     As uuid
    Dim clsid   As uuid
    
    InitRuntime = UserDllMain(lpInst, lpUnk, hInstDll, fdwReason, ByVal lpvReserved)
    If InitRuntime Then
        vbCoInitialize ByVal 0&
        iid.data4(0) = &HC0: iid.data4(7) = &H46                    ' IUnknown
        VBDllGetClassObject lpInst, lpUnk, lpVBHdr, clsid, iid, 0   ' Инициализация потока
    End If
End Function

For apartment threaded:

' modMainDLL.bas  - инициализация DLL (Apartment threaded)
' © Кривоус Анатолий Анатольевич (The trick), 2014

Option Explicit

Private Type uuid
    data1       As Long
    data2       As Integer
    data3       As Integer
    data4(7)    As Byte
End Type

Public hInstance    As Long

Private lpInst_     As Long
Private lpUnk_      As Long
Private lpVBHdr_    As Long

' Точка входа, здесь не должно быть обращения к внешним переменным, т.е. public, private, static
Public Function DllMain(ByVal hInstDLL As Long, ByVal fdwReason As Long, ByVal lpvReserved As Long) As Long
    Dim iid         As uuid
    Dim clsid       As uuid
    Dim lpInst     As Long
    Dim lpUnk      As Long
    Dim lpVBHdr    As Long
    Dim lpProc  As Long
    
    ' При создании процесса или потока
    If fdwReason = DLL_PROCESS_ATTACH Or fdwReason = DLL_THREAD_ATTACH Then
        ' Получаем нужные нам данные, VBHeader, и два указателя необходимых для инициализаци
        ' Каждый поток содержит свои данные (публичные, статичные переменные и т.д.)
        lpProc = GetProcAddress(hInstDLL, "DllGetClassObject")
        If lpProc = 0 Then Exit Function
        GetMem4 ByVal lpProc + 2, lpVBHdr
        GetMem4 ByVal lpProc + 7, lpUnk
        GetMem4 ByVal lpProc + 12, lpInst
        ' Инициализация COM
        vbCoInitialize ByVal 0&
        ' Эта функция вызывается из ActiveX DLL
        DllMain = UserDllMain(lpInst, lpUnk, hInstDLL, fdwReason, ByVal lpvReserved)
        If DllMain = 0 Then Exit Function
        iid.data4(0) = &HC0: iid.data4(7) = &H46                            ' IUnknown
        VBDllGetClassObject lpInst, lpUnk, lpVBHdr, clsid, iid, 0           ' Инициализация потока
        ' Тут глобальные и статичные переменные обнуляются, восстанавливаем их
        SetPublicVariable lpInst, lpUnk, lpVBHdr, hInstDLL
    Else
        vbCoUninitialize
        DllMain = DefMainDLL(hInstDLL, fdwReason, ByVal lpvReserved)
    End If

End Function

Private Sub SetPublicVariable(ByVal lpInst As Long, ByVal lpUnk As Long, ByVal lpVBHdr As Long, ByVal hInstDLL As Long)
    lpInst_ = lpInst: lpUnk_ = lpUnk: lpVBHdr_ = lpVBHdr: hInstance = hInstDLL
End Sub
Private Function DefMainDLL(ByVal hInstDLL As Long, ByVal fdwReason As Long, ByVal lpvReserved As Long) As Long
    DefMainDLL = UserDllMain(lpInst_, lpUnk_, hInstDLL, fdwReason, ByVal lpvReserved)
End Function

So now we know how to initialize the runtime and can begin to compile a native DLL. In the project file add these lines for specifying additional compiler and linker keys:

[VBCompiler]
LinkSwitches= /ENTRY:DllMain /EXPORT:Brightness /EXPORT:Contrast /EXPORT:Saturation /EXPORT:GaussianBlur /EXPORT:EdgeDetect /EXPORT:Sharpen /EXPORT:Emboss /EXPORT:Minimum /EXPORT:Maximum /EXPORT:FishEye

And adjusts the threading model of the project in single threaded, also need to add a class to the project, otherwise the project will not compile. Optionally, you can also add functionality ActiveX DLL, then you can work with this DLL and how ActiveX, and as with the conventional native importing function.

[Bonnie West]

In the project file add these lines for specifying additional compiler and linker keys:

[VBCompiler]
LinkSwitches= /ENTRY:DllMain /EXPORT:Brightness /EXPORT:Contrast /EXPORT:Saturation /EXPORT:GaussianBlur /EXPORT:EdgeDetect /EXPORT:Sharpen /EXPORT:Emboss /EXPORT:Minimum /EXPORT:Maximum /EXPORT:FishEye

Fantastic trick!



BTW, don't know if you already came across this, but I thought you might be interested in seeing this guy's similar guide to constructing standard DLLs using VB6.

[firehacker]

So now we know how to initialize the runtime and can begin to compile a native DLL. In the project file add these lines for specifying additional compiler and linker keys:

[VBCompiler]
LinkSwitches= /ENTRY:DllMain /EXPORT:Brightness /EXPORT:Contrast /EXPORT:Saturation /EXPORT:GaussianBlur /EXPORT:EdgeDetect /EXPORT:Sharpen /EXPORT:Emboss /EXPORT:Minimum /EXPORT:Maximum /EXPORT:FishEye

Isn't that fair to mention who actually discovered these undocumented keys?

[Bonnie West]

Isn't that fair to mention who actually discovered these undocumented keys?

... there are a few tricks you can use to create a native DLL, from the substitution of the linker and ending undocumented sections in vbp-file.

Special thanks I would like to express Vladislav Petrovsky (aka. Hacker) for the discovery of undocumented keys compiler / linker.

[firehacker]

I was using "Hybrid" topic display mode. In this mode links such as your:

Yet another way of setting the /LARGEADDRESSAWARE flag is by exploiting the undocumented [VBCompiler] option for .VBP files:

brings me to this (http://www.vbforums.com/showthread.p...id#post4835355) post which is displayed alone (i.e. without preceding posts) in hybrid mode.

So, since this post (post #3 when in linear topic display mode) that mentions [VBCompiler] doesn't contain a word about me, I mistakenly thought The trick decided not to mention me.

[xiaoyao]

vb STANDAND DLL,a api show form1,vb crash,maybe need use "COMDllLoader"?

' References:
' VBoostTypes6.olb (VBoost Object Types (6.0))
' ObjCreate.olb (VBoost: Object Creation and Security)
' This file is from the CD-ROM accompanying the book:
' Advanced Visual Basic 6: Power Techniques for Everyday Programs

Option Explicit

Private m_fInit As Boolean
Public IID_IClassFactory As IID
Public IID_IUnknown As IID
Private m_FDDllGetClassObject As FunctionDelegator
Private m_pCallDllGetClassObject As ICallDllGetClassObject
Private m_FDDllCanUnloadNow As FunctionDelegator
Private m_pCallDllCanUnloadNow As ICallDllCanUnloadNow

Private Sub Init()
    IID_IClassFactory = IIDFromString(strIID_IClassFactory)
    IID_IUnknown = IIDFromString(strIID_IUnknown)
    Set m_pCallDllGetClassObject = InitDelegator(m_FDDllGetClassObject)
    Set m_pCallDllCanUnloadNow = InitDelegator(m_FDDllCanUnloadNow)
    m_fInit = True
End Sub

Public Function GetDllClassObject(ByVal DllPath As String, CLSID As CLSID, hModDll As hInstance) As IClassFactory
    If Not m_fInit Then Init
    If hModDll = 0 Then
        hModDll = LoadLibraryEx(DllPath, 0, LOAD_WITH_ALTERED_SEARCH_PATH)
        If hModDll = 0 Then
            Err.Raise &H80070000 + Err.LastDllError
        End If
    End If
    m_FDDllGetClassObject.pfn = GetProcAddress(hModDll, "DllGetClassObject")
    If m_FDDllGetClassObject.pfn = 0 Then
        Err.Raise &H80070000 + Err.LastDllError
    End If
    Set GetDllClassObject = m_pCallDllGetClassObject.Call(CLSID, IID_IClassFactory)
End Function

Public Sub TestUnloadDll(hModDll As hInstance)
    If hModDll Then
        If Not m_fInit Then Init
        m_FDDllCanUnloadNow.pfn = GetProcAddress(hModDll, "DllCanUnloadNow")
        If m_FDDllCanUnloadNow.pfn = 0 Then
            Err.Raise &H80070000 + Err.LastDllError
        End If
        If m_pCallDllCanUnloadNow.Call = 0 Then
            FreeLibrary hModDll
            hModDll = 0
        End If
    End If
End Sub

[xiaoyao]

Get the address of "UserDllMain" is very simple, because we know the handle of the library (it is passed as the first parameter); call "GetProcAddress" and get the address "DllGetClassObject". Next, we obtain the values through "GetMem4". I want to note that all API functions must be declared in a type library for this I compiled "DllInitialize.tlb", after compiling it does not need. To call "VBDllGetClassObject" use as "IID - IUnknown", as "CLSID - IID_NULL". Also, for initialization "COM" function must be called "CoInitialize". If we now try to collect a DLL, it will work, but keep in mind that the first call "VBDllGetClassObject" all unit variables are initialized to default values. Therefore it is necessary to call derived variables stored in local variables, and then it is already possible to maintain a modular. You also need to consider the threading model of the project: to "Apartment", as a function of "DllMain" should not be appeals to modular variables. For both models, I created two modules:
For single threaded:[CODE]' modMainDLL.bas - инициализация DLL (Single thread)
' © Кривоус Анатолий Анатольевич (The trick), 2014

Option Explicit

Private Type uuid
data1 As Long
data2 As Integer
data3 As Integer
data4(7) As Byte
End Type

Public hInstance As Long

Private lpInst_ As Long
Private lpUnk_ As Long
Private lpVBHdr_ As Long

' Точка входа
Public Function DllMain(ByVal hInstDll As Long, ByVal fdwReason As Long, ByVal lpvReserved As Long) As Long
Dim lpProc As Long
Dim lpInst As Long
Dim lpUnk As Long
Dim lpVBHdr As Long

' При создании процесса инициализируем адреса нужных переменных
If fdwReason = DLL_PROCESS_ATTACH Then
' Получаем нужные нам данные, VBHeader, и два указателя необходимых для инициализации
lpProc = GetProcAddress(hInstDll, "DllGetClassObject")
If lpProc = 0 Then Exit Function
GetMem4 ByVal lpProc + 2, lpVBHdr
GetMem4 ByVal lpProc + 7, lpUnk
GetMem4 ByVal lpProc + 12, lpInst
DllMain = InitRuntime(lpInst, lpUnk, lpVBHdr, hInstDll, fdwReason, lpvReserved)
lpInst_ = lpInst: lpUnk_ = lpUnk: lpVBHdr_ = lpVBHdr: hInstance = hInstDll
ElseIf fdwReason = DLL_THREAD_ATTACH Then
DllMain = InitRuntime(lpInst_, lpUnk_, lpVBHdr_, hInstDll, fdwReason, lpvReserved)
Else
vbCoUninitialize
DllMain = UserDllMain(lpInst_, lpUnk_, hInstDll, fdwReason, ByVal lpvReserved)
End If

End Function

[VBCompiler]
LinkSwitches=/DLL /ENTRYllMain /EXPORT:Sum /EXPORT:ShowForm

Public Sub ShowForm()
IntDll  'InitRuntime
Msg "ShowForm"
Dim f As Form1
Set f = New Form1
f.Show 1
Set f = Nothing
vbCoUninitialize
End Sub

when i call "ShowForm" in vc++ or (visual freebasic)
it's successful,but when exe unload ,it's error happend(crash),how to fix vb standad.
if we USE " DLL injection" to other exe(application),for best we can DLL_PROCESS_ATTACH AND unload dll more times.
but it's can't unload dll.
i want to fireevents "DLL_PROCESS_ATTACH " when load dll
load dll
unload dll
load dll
unload dll
****
I want to load and unload the DLL several times, the operation will not crash
maybe we need call api "DllCanUnloadNow","DllUnregisterServer"?
chinese:我想多次加载卸载DLL,随便操作都不会崩溃就好了