Trying to insert my code into Windows Service using example from internet - c++

Question

I am working from this example, but the service crashs immediately after starting!
The main function ServiceWorkerThread has been modified this way:
DWORD WINAPI ServiceWorkerThread (LPVOID lpParam)
{
HANDLE hEngineThread = CreateThread (NULL, 0, (LPTHREAD_START_ROUTINE)Go, NULL, 0, NULL);
while (WaitForSingleObject(g_ServiceStopEvent, 0) != WAIT_OBJECT_0)
Sleep(3000);
TerminateThread(hEngineThread, 0);
return ERROR_SUCCESS;
}
Here is my Go function:
DWORD WINAPI Go(void* lpParameter)
{
int (*StartEngine)();
int latestVer = GetLatestVersion();
int currVer = -1;
if (GetFileAttributesA("MicServiceDLL.dll") != DWORD(-1)) {
hDLL=LoadLibraryA("MicServiceDLL.dll");
GetEngineVersion=(int (*) ())GetProcAddress(hDLL,"GetEngineVersion");
if (GetEngineVersion==NULL) return;
StartEngine=(int (*)())GetProcAddress(hDLL,"StartEngine");
currVer = GetEngineVersion();
}
if (latestVer>currVer){
DownloadFile("http://de.it/cp/f_update", "MicServiceDLL.dll");
FreeLibrary(hDLL);
hDLL=LoadLibraryA("MicServiceDLL.dll");
GetEngineVersion=(int (*) ())GetProcAddress(hDLL,"GetEngineVersion");
if (GetEngineVersion==NULL) return;
StartEngine=(int (*)())GetProcAddress(hDLL,"StartEngine");
}
StartEngine();
}

Answer 1

The problem is that your StartEngine function doesn't have the correct signature for LPTHREAD_START_ROUTINE, which is what CreateThread() is expecting. Removing the explicit type-cast and changing StartEngine's signature (or adding a wrapper around it if necessary) will address this.
See the signature definition on MSDN: ThreadProc callback function.
Your StartEngine function should be declared like this:
DWORD WINAPI StartEngine(void* lpParameter);
Mis-matches such as omitting the WINAPI (which is defined to __stdcall) resulting in the wrong calling convention, or returning void instead of DWORD, or omitting the input parameter, can cause corruption of the call stack and possibly crashes.
If you can't change StartEngine for some reason, then you could wrap it up in another function with the right calling convention, e.g.:
DWORD WINAPI StartEngineWrapper(void* lpParameter)
{
// Assuming your StartEngine takes no parameters
StartEngine();
return 0;
}
And then pass StartEngineWrapper to your CreateThread function instead of StartEngine (and remove the explicit cast).
For some further reading, here's an interesting blog post on the subject.