IMA error when dynamically loading a DLL

[breeze4me]

This is about a bug that has been fixed in the past.
https://www.purebasic.fr/english/viewtopic.php?t=43173

I've been testing that code and found a problem: it works fine when using the lib file, but crashes when dynamically loading the dll.

dll code:

Code: Select all

ProcedureDLL addScrollArea(hWnd)
  oldGadgetList = UseGadgetList(hWnd)
  gadget = ContainerGadget(#PB_Any, 0, 0, 400, 400)
    CloseGadgetList()
    SetGadgetColor(gadget, #PB_Gadget_BackColor, #Red)
  UseGadgetList(oldGadgetList)
EndProcedure

main code(OK):

Code: Select all

Import "dll.lib"
  CompilerIf #PB_Compiler_Processor = #PB_Processor_x86
    addScrollArea(a) As "_addScrollArea@4"
  CompilerElse
    addScrollArea(a)
  CompilerEndIf
EndImport

#win = 16  ;Change to 15 or less to remove the crash!

If OpenWindow(#win, 0, 0, 600, 600, "", #PB_Window_SystemMenu|#PB_Window_MinimizeGadget|#PB_Window_MaximizeGadget|#PB_Window_SizeGadget|#PB_Window_ScreenCentered)
  addScrollArea(WindowID(#win))
  Repeat 
    event=WaitWindowEvent() 
  Until Event = #PB_Event_CloseWindow
EndIf

main code (IMA in PB x86 / debugger crashes in PB x64):

Code: Select all

#win = 16  ;Change to 15 or less to remove the crash!

Prototype addScrollArea(a)
Define addScrollArea_.addScrollArea

If OpenLibrary(0, "dll.dll")
  addScrollArea_ = GetFunction(0, "addScrollArea")
  If OpenWindow(#win, 0, 0, 600, 600, "", #PB_Window_SystemMenu|#PB_Window_MinimizeGadget|#PB_Window_MaximizeGadget|#PB_Window_SizeGadget|#PB_Window_ScreenCentered)
    If addScrollArea_
      addScrollArea_(WindowID(#win))
    EndIf
    Repeat 
      event=WaitWindowEvent() 
    Until Event = #PB_Event_CloseWindow
  EndIf
  CloseLibrary(0)
EndIf     ; Invalid memory access. (read error at address 1387796518)

[mk-soft]

It doesn't work that way. A DLL has its own object management and is not coupled with the main executable.
Link: Access gadget from libray

[breeze4me]

Anyway, I found a workaround.
If the CloseLibrary(0) line is removed, there is no error.

Edit:
I tested a complex case and the workaround didn't work.
The ".lib" file must be used for this to work properly.

@mk-soft
I read that post a long time ago.
What I'm trying to do is not share the object management system, I'm just researching how to create gadgets from DLLs like the way srod used in the original post.

[mk-soft]

@mk-soft
I read that post a long time ago.
What I'm trying to do is not share the object management system, I'm just researching how to create gadgets from DLLs like the way srod used in the original post.

But the gadget is then in the wrong object list. In the DLL and not in the Main ...

[breeze4me]

But the gadget is then in the wrong object list. In the DLL and not in the Main ...

I know. I plan to have the main code manipulate the gadgets created by DLLs in a way that calls functions inside DLLs.
This is enough to support custom gadgets via DLLs in a form designer app.

[Fred]

I fixed the crash when the DLL is dynamically loaded and auto-freed at end in 6.21 beta 5 (ie: CloseLibrary() not called). But if you close the DLL before exiting, there is still some callbacks registered from the DLL in the main process and it will crash because the window will try to call the callback when doing its cleanup. So you can either let the program unload the DLL automatically at end or close all the windows before calling CloseLibrary().

[breeze4me]

I fixed the crash when the DLL is dynamically loaded and auto-freed at end in 6.21 beta 5 (ie: CloseLibrary() not called). But if you close the DLL before exiting, there is still some callbacks registered from the DLL in the main process and it will crash because the window will try to call the callback when doing its cleanup. So you can either let the program unload the DLL automatically at end or close all the windows before calling CloseLibrary().

Thank you for the explanation.