Thread local storage problem, and fix

["Phil Frisbie, Jr." <phil@hawksoft.com>]

While converting the simple per thread error storage in HawkNL over to POSIX and
native Windows thread local storage, I came across some problems. I store a
HawkNL error code for the thread, and if it is a Winsock error I set the error
to NL_SOCKET_ERROR so the application can retrieve the real error code. But
Winsock errors seemed to be cleared whenever pthread_getspecific() was called.
They were also cleared by calling the native Windows TlsGetValue().

So, I looked at the Pthreads-win32 source code for pthread_getspecific(), and
found this:

void *
pthread_getspecific (pthread_key_t key)
{
  int lasterror = GetLastError();

  void *ptr = TlsGetValue (key->key);

  SetLastError( lasterror );

  return ptr;
}

I guess someone already found out TlsGetValue() clears out the last error, but
they did not know it also clears out the last Winsock error. The fix is to
change the code to:

void *
pthread_getspecific (pthread_key_t key)
{
  int lasterror = GetLastError();
  int lastWSAerror = WSAGetLastError();

  void *ptr = TlsGetValue (key->key);

  SetLastError( lasterror );
  WSASetLastError( lastWSAerror );

  return ptr;
}

I have added a work around to HawkNL until this gets fixed.


Phil Frisbie, Jr.
Lead Developer, Hawk Software
http://www.hawksoft.com