PostEvent in DLL fails when procedure called from a thread

[Olby]

Hi,

Can anyone please explain why the code below fails:

Code: Select all

CompilerIf #PB_Compiler_ExecutableFormat=#PB_Compiler_DLL
	
	Procedure thread(*p) ; api func
		PostEvent(#PB_Event_FirstCustomValue)
		Delay(5000)
		PostEvent(#PB_Event_FirstCustomValue+1)
	EndProcedure
	
	Procedure.i run() ; wait thread func
		If OpenWindow(0,0,0,320,240,"Module Window",#PB_Window_SystemMenu)
			If CreateThread(@thread(),0)
				Repeat
					Protected event.i=WaitWindowEvent()
					If event=#PB_Event_FirstCustomValue+1
						ProcedureReturn 2001
					EndIf
				ForEver
			EndIf
		EndIf
	EndProcedure
	
	ProcedureDLL.i test() ; run func
		ProcedureReturn run()
	EndProcedure

CompilerElse
	
	Procedure calltest(*p) ; module caller thread
		Debug "Calling test() in dll"
		Debug CallFunction(0,"test")
	EndProcedure
	
	If OpenLibrary(0,"_test.dll")
		If OpenWindow(0,0,0,800,600,"Window",#PB_Window_SystemMenu)
			Debug "Waiting for 2001 response in 5 seconds"
			
			test.b=1
			
			If test=1
				calltest(0)
			Else
				If CreateThread(@calltest(),0)
					Repeat 
						WaitWindowEvent()
						Delay(1000)
						Debug "..."
					ForEver
				EndIf
			EndIf
			
		EndIf
	EndIf
	
CompilerEndIf

Flags: ThreadSafe, Unicode, WinXP & OnError

First compile a DLL to _test.dll, then switch back to regular executable mode and run the code again.

If test =1 everything is fine. We call the dll function directly and after 5 seconds the internal postevent signals the DLL func to return 2001 back to the main process.

Now the issue I have is with test <>1 mode. In this case the DLL function is called from a thread within the main process. And it will never return because the PostEvent(#PB_Event_FirstCustomValue+1) in the DLL will never reach its destination and the DLL function will keep on running for ever.

Is this a PB bug or there is an issue with clashing event streams or something similar?

Thanks!

[Danyfirex]

Hello. If you're createing a thread safe library you must use PostThreadMessage and pass the thread id to the subthread.

Code: Select all

Global threadid=0

Procedure thread(*p) ; api func
      PostEvent(#PB_Event_FirstCustomValue)
      Delay(5000)
      ;PostEvent(#PB_Event_FirstCustomValue+1)
      PostThreadMessage_(*p,#PB_Event_FirstCustomValue+1,0,0)
 EndProcedure
   
   Procedure.i run() ; wait thread func
     If OpenWindow(0,0,0,320,240,"Module Window",#PB_Window_SystemMenu)
       threadid=GetCurrentThreadId_()
         If CreateThread(@thread(),threadid)
            Repeat
               Protected event.i=WaitWindowEvent()
               If event=#PB_Event_FirstCustomValue+1
                  ProcedureReturn 2001
               EndIf
            ForEver
         EndIf
      EndIf
   EndProcedure
   
   ProcedureDLL.i test() ; run func
      ProcedureReturn run()
   EndProcedure

other alternative if you want to use your dll code is compiling your dll as not thread safe. that way you don't need PostThreadMessage




Saludos

[Olby]

That seems like a good solution. So my guess was right each thread has its own event queue. Thanks, Danyfirex.

[Danyfirex]

You're Wellcome.

Saludos