[Lazarus] Mutlithreaded Dll Callback crashes my Application

[Alexander Grau]

José Mejuto schrieb:
> Hello Lazarus-List,
>
> Wednesday, August 25, 2010, 8:44:53 AM, you wrote:
>
> MW> I've packed the runtime env dlls and put them on my ftp server.
> MW> They are too big to attach to the mail on the list.
>
> Do you have compiled the "vcmtdll.dll" with Multithread runtime
> library (/MT) ?
>
> To avoid crashes just simply:
>
> // start threads
> for index := 0 to FThreads.Count-1 do
> begin
>    TVCMTThread(FThreads.Items[index]).Start(10);
>    Sleep(50);
> end;
>
> Adding the Sleep(50) avoids any crash, and the AsyncWrite works as
> expected. You should also add a Sleep(50) after each FThreads[n].free
>
> If a multithread problem is solved with sleeps usually it is a race
> condition in the RTL, in this case you create a new thread while the
> provious one is being created (or destroyed), so to me looks like a
> VC++ non multithread RTL problem.
>
> It is also desirable to add the line "IsMultithread:=true" in the
> first line of .lpr (after the begin) to activate the Multithread RTL
> in the FPC, otherwise it could not be active.
>
> I had tested it with 200 threads and using the sleeps no problem at
> all.
>   
Hello José,

I have tried to reduce the DLL problem into a test that doesn't need any 
external DLL. It crashes too.

Here's the test program:

http://grauonline.de/alexwww/tmp/extthread.zip

Can you see any analogy to the problem? I have tried to add your 
suggested "IsMultithread:=true" and it doesn't make any difference. I 
think there's something wrong in the FPC runtime.

Regards,
Alexander