Pointer to a pointer

[jugador]

Another option is to use the Global Interface Table to pass object pointers.

[Nine]

13 hours ago, jugador said:

Another option is to use the Global Interface Table to pass object pointers.

  

On 5/21/2025 at 3:18 PM, jugador said:

the answer to the original post is CoMarshalInterface and CoUnmarshalInterface.

Interesting.  I wouldn't mind having a working example of both your "solutions".  As far I can remember, those cannot be used between processes but only between threads of a single process.

[jugador]

Yes, the Global Interface Table is used to pass object pointers between threads within a single process.

Using CoMarshalInterface and CoUnmarshalInterface, you can pass pointers between multiple processes (tested with Scripting.Dictionary).

[argumentum]

16 hours ago, Nine said:

I wouldn't mind having a working example

6 hours ago, jugador said:

Using CoMarshalInterface and CoUnmarshalInterface, you can pass pointers between multiple processes (tested with Scripting.Dictionary).

@jugador, would you post an example script to show it working ?

[jugador]

Get time to test custom object with CoMarshalInterface and CoUnmarshalInterface function.
worked well between threads within a single process.

But I failed to make it worked between multiple process as the CLSID and IID is not registered.
So to make it work one have to implement IMarshal interface https://learn.microsoft.com/en-us/windows/win32/api/objidl/nn-objidl-imarshal
If the IMarshal interface is not implemented properly then IMarshal::UnmarshalInterface may not be invoked when CoUnmarshalInterface is called.

Global $IID_IMyInterface = "{12345678-9abc-4def-8901-23456789abcd}"
Local $t_TestObj
Local $tagMessage_IUnknown = "GetMessage hresult();"
Local $o_TestObj = _ObjectFromTag("__MyInterface_", $tagMessage_IUnknown, $t_TestObj, Default, $IID_IMyInterface)

 

Code for CoMarshalInterface & CoUnmarshalInterface

; #FUNCTION# =============================================================================
; Name ..........: __CoMarshalInterface
; ========================================================================================
Func __CoMarshalInterface($pStm, $pUnk, $riid = "{00000000-0000-0000-C000-000000000046}", $dwDestContext = 0, $mshlflags = 0)
    Local $triid = __CLSIDFromString($riid)
    Local $aResult = DllCall("ole32.dll", "int", "CoMarshalInterface", "ptr", $pStm, _                      ;~ A pointer to the stream to be used during marshaling.
                                                                       "ptr", DllStructGetPtr($triid), _    ;~ This interface must be derived from the IUnknown interface.
                                                                       "ptr", $pUnk, _                      ;~ This interface must be derived from the IUnknown interface.
                                                                       "dword", $dwDestContext, _           ;~ MSHCTX_LOCAL = 0
                                                                       "ptr", 0, _
                                                                       "dword", $mshlflags)                 ;~ MSHLFLAGS_NORMAL = 0
    If @error Or $aResult[0] <> 0 Then Return SetError(1)
    Return $aResult[0]
EndFunc

; #FUNCTION# =============================================================================
; Name ..........: __CoUnmarshalInterface
; ========================================================================================
Func __CoUnmarshalInterface($pStm, $riid)
    Local $triid = __CLSIDFromString($riid)
    Local $aResult = DllCall("ole32.dll", "int", "CoUnmarshalInterface", "ptr", $pStm, "ptr", DllStructGetPtr($triid), "ptr*", 0)
    If @error Or $aResult[0] <> 0 Then Return SetError(1)
    Return $aResult[3]  ;~ <<==(ppv)Pointer to the unmarshaled interface
EndFunc

I will not try further with a custom object to make it work across multiple processes, as implementing the IMarshal interface is out of my league.

Edit:

I am bad at giving up 

I managed to implement the IMarshal interface and made a custom object work across multiple processes,
with the help of the IClassFactory interface for temporary registration of the CLSID.
 

Edited May 29 by jugador