Win32 Mutex not waiting

I am creating an application that implements inter process communication. For this purpose I have set up a shared buffer, which seems to work fine. Now, I need a way for the data generating application (written in c++) to tell the data receiving application (written in freepascal/lazarus) when it should read the data.

I was trying to use a mutex for this purpose. I do not have much experience with windows api programming.

So, my problem is, in the FreePascal code below, the mutex won't wait. I can call the TMutex.Wait() function, it doesn't return an error or anything, but it simply won't wait.

constructor TMutex.Create(sName: AnsiString);

begin

  sName := 'Local\Mutex'+sName;

  hMutex := CreateMutexA(

        nil, // default access

      开发者_StackOverflow中文版;  True, // initially not owned

        PChar(sName)); // named mutex

  if hMutex = 0 then

  begin

    raise Exception.Create('mutex creation failed');

  end;

end;

destructor TMutex.Destroy;

begin

  CloseHandle(hMutex);

end;

procedure TMutex.Wait;

begin

  if (WaitForSingleObject(hMutex, INFINITE) <> 0) then ShowMessage('debug: wait returned something');

end;

procedure TMutex.Post;

begin

  ReleaseMutex(hMutex);

end;

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It looks like your problem is at:

    True, // initially not owned

You have things backwards -- true means it initially IS owned, so waiting on it will return immediately.

---

you don't show us the code that calls the Wait, method of TMutex. however, you have to know that a mutex is reentrant: if a thread owns a mutex, it will always be granted access to it, thus a wait will never block. this is built into the mutex to avoid deadlocks.

try acquiring the mutex from another thread, the wait should block.