I can't a class members in working thread

Thu, 30 Aug 2007 19:30:54 -0000

Last week I got faced to a curious problem when try to access the
member pointers of my class in the worker thread. In main thread
everything is ok, but in worker thread when I try to access member
pointers I got access violation failure. The curious part is that the
pointers addresses are ok, but the place where their points seem to be
empty in the worker thread but not in main thread.

class Sound
  // Public Member Functions

  static DWORD WINAPI ThreadProc(LPVOID lpParameter) { // Helper
    Sound* info = (Sound*)&lpParameter;
    return info->ThreadProc();
  DWORD WINAPI ThreadProc();

  LPDIRECTSOUNDBUFFER8 m_lpdsb8; // OK in main thread, fails in
  DSBUFFERDESC m_dsbdesc; // OK in both threads
  LPDIRECTSOUND8 m_lpds; // I don't use it in worker thread
  HANDLE m_hEvent[2]; // OK in main thread, fails in worker
  SndFile* m_Wave; // OK in main thread, fails in worker

DWORD WINAPI Sound::ThreadProc()
  DWORD dwBytes1, dwBytes2;
  LPVOID lpvPtr1, lpvPtr2;
  DWORD dwRetIndex = 0;
  DWORD dwOffset;

  // m_hEvent address is ok but data seems to be empty
  while ((dwRetIndex = WaitForMultipleObjects( 2, m_hEvent, FALSE,
    // ACCESS VIOLATION: m_lpdsb8
    hr = m_lpdsb8->Lock( dwOffset, m_dsbdesc.dwSize / 2, &lpvPtr1,
&dwBytes1, &lpvPtr2, &dwBytes2, 0 );

    // And so on

  return 0;

The data of pointers should be correct because worker thread
terminates almost immediately(because the WaitForMultipleObjects
returns WAIT_FAILED for m_hEvent) and later when the main thread
access them everything goes fine.

Any idea?

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