winsock and new thread does not release memory - c++

Question

I have a really strange problem. Looking for the cause on the web and try everything. Nothing helps.
First case:
(This works exactly as expected. Windows task manager shows the constant memory size, and does not increase.)
unsigned long WINAPI thfun(void * arg)
{
::Sleep(50);
::ExitThread(0);
return 0;
}
int main(int argc, const wchar_t ** argv)
{
HANDLE th = 0;
DWORD thid, err;
while (true)
{
th = ::CreateThread(0, 0, thfun, 0, 0, &thid);
if (!th)
{
err = ::GetLastError();
}
::WaitForSingleObject(th, INFINITE);
}
return 0;
}
Second case:
unsigned long WINAPI thfun(void * arg)
{
::Sleep(50);
::ExitThread(0);
return 0;
}
int main(int argc, const wchar_t ** argv)
{
WORD ver;
WSADATA wsadata;
ver = MAKEWORD(2, 2);
if (WSAStartup(ver, &wsadata)) return 1;
::Sleep(50);
HANDLE th = 0;
DWORD thid, err;
while (true)
{
th = ::CreateThread(0, 0, thfun, 0, 0, &thid);
if (!th)
{
err = ::GetLastError();
}
::WaitForSingleObject(th, INFINITE);
}
return 0;
}
If I call any function from winsock least once created threads do not release memory.
Windows task manager shows ever-growing memory of my application.
What should I do so that I achieve the same behavior as in the first case when I use winsock?
I use visual studio 2013
Thank you very much for any help

Answer 1

You do not close your thread handles. A common error.
Your core loop should look like that:
while (true)
{
th = ::CreateThread(0, 0, thfun, 0, 0, &thid);
if (!th)
{
err = ::GetLastError();
}
::WaitForSingleObject(th, INFINITE);
CloseHandle(th);
}
That problem exists in both of your examples. That memory grow of the second sample can be a side effect.
ExitThread(0) is never a good idea and I do not understand why Microsoft recommand it for C. As the Winsock API should not have any destructor, it should not be a problem. Nevertheless, do not use it.
UPDATE
I tested your code as release on a Windows 7 64bit SP1 System with Antivira personal installed (my gaming machine). Also on my Windows 8 VM (parallels). Both system did not show the problems you described and show in your video. This is IMHO good news for you, because it seems a problem of your installation and not a general problem.
The video shows a leak of only a few bytes per ended thread and strict linear growing per thread. This looks for me like thread associated information, usually stored nowadays in TLS (Thread Local Storage). Also it only appears when you init The WSASocket system. If the WSASocket system itself would be the problem, we would found reports of it for sure(but I didn't). I believe a hook DLL is causing that problem, a DLL is informed over the DllMain of any started or ended thread of the process. Any virus scanner or keyboard addon(!) can cause such a problem as they usually use hook DLLs and manipulate IOs like pipes and sockets.
Unfortunatly I only know one way to find out:
Make a release canditate of your sample. Make sure the problem exist.
Make a clean install of Windows 7
Install step by step the environment you use on your produktive system. Make sure you restart the Computer after every step.
Hopefully find the culprit.
Deactivating or uninstall hooks may help but need not. Unfortunately installing programs on windows system is maximal inversive.
Sorry for not heaving the easy answer.