WindowsProcess: unable to detect closure of program

[massimilianodelliubaldini]

Hello again! Thanks for your fix to #13! I'm making more progress on using PME because of it. Unfortunately I'm back to report another problem. On Windows, it seems that the __closed property of a WindowsProcess is not set to True correctly when I close out of a program (hitting the X on the window).

This leaves my code in a state where I can still read_process_memory on the closed process. Naturally, this returns all 0's. But my use case is a 1/10th of a second polling function just to check that process is still alive, and show the user a message if it crashes/dies. Even if I was checking the value of __closed rather than reading memory, it still holds False.

Here's a shell window showing me creating an OpenProcess instance of a running program, closing the program, and then reading its memory.

>>> gk = OpenProcess(process_name="gk.exe")
>>> gk
<PyMemoryEditor.win32.process.WindowsProcess object at 0x00000293B1CB1BE0>

...
I close the app here.
...

>>> gk.pid
4224
>>> gk.read_process_memory(0, bytes, 1)
b'\x00'
>>> gk.read_process_memory(0, bytes, 100)
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'

[massimilianodelliubaldini]

Here's my use-case code, the poller for checking the aliveness of the program.

 try:
    self.gk_process.read_process_memory(0, bytes, 1)  # Ping to see if it's alive.
except (ProcessNotFoundError, ProcessIDNotExistsError, ClosedProcess):
    msg = f"Error reading game memory! (Did the game crash?)"
    self.log_error(logger, msg)

I know you have a defense against reading from closed processes in read_process_memory but I think the problem may lie further upstream, when the call is made to kernel32 to close a process.

def CloseProcessHandle(process_handle: int) -> int:
    """
    Close the process handle.
    """
    return kernel32.CloseHandle(process_handle)

...

class WindowsProcess(AbstractProcess):
...
    def close(self) -> bool:
        # Check the documentation of this method in the AbstractProcess superclass for more information.
        if self.__closed: return True

        self.__closed = CloseProcessHandle(self.__process_handle) != 0
        return self.__closed

Let me know if I misunderstood the purpose of the close function, or if you need any other info. Thanks!