Python test.support.gc_collect() Examples

def test_IOBase_finalize(self):
        # Issue #12149: segmentation fault on _PyIOBase_finalize when both a
        # class which inherits IOBase and an object of this class are caught
        # in a reference cycle and close() is already in the method cache.
        class MyIO(self.IOBase):
            def close(self):
                pass

        # create an instance to populate the method cache
        MyIO()
        obj = MyIO()
        obj.obj = obj
        wr = weakref.ref(obj)
        del MyIO
        del obj
        support.gc_collect()
        self.assertIsNone(wr(), wr) 

def test_frame_resurrect(self):
        # A generator frame can be resurrected by a generator's finalization.
        def gen():
            nonlocal frame
            try:
                yield
            finally:
                frame = sys._getframe()

        g = gen()
        wr = weakref.ref(g)
        next(g)
        del g
        support.gc_collect()
        self.assertIs(wr(), None)
        self.assertTrue(frame)
        del frame
        support.gc_collect() 

def test_refcycle(self):
        # A generator caught in a refcycle gets finalized anyway.
        old_garbage = gc.garbage[:]
        finalized = False
        def gen():
            nonlocal finalized
            try:
                g = yield
                yield 1
            finally:
                finalized = True

        g = gen()
        next(g)
        g.send(g)
        self.assertGreater(sys.getrefcount(g), 2)
        self.assertFalse(finalized)
        del g
        support.gc_collect()
        self.assertTrue(finalized)
        self.assertEqual(gc.garbage, old_garbage) 

def test_override_destructor(self):
        record = []
        class MyTextIO(self.TextIOWrapper):
            def __del__(self):
                record.append(1)
                try:
                    f = super().__del__
                except AttributeError:
                    pass
                else:
                    f()
            def close(self):
                record.append(2)
                super().close()
            def flush(self):
                record.append(3)
                super().flush()
        b = self.BytesIO()
        t = MyTextIO(b, encoding="ascii")
        del t
        support.gc_collect()
        self.assertEqual(record, [1, 2, 3]) 

def test_garbage_collection(self):
        # C TextIOWrapper objects are collected, and collecting them flushes
        # all data to disk.
        # The Python version has __del__, so it ends in gc.garbage instead.
        with support.check_warnings(('', ResourceWarning)):
            rawio = io.FileIO(support.TESTFN, "wb")
            b = self.BufferedWriter(rawio)
            t = self.TextIOWrapper(b, encoding="ascii")
            t.write("456def")
            t.x = t
            wr = weakref.ref(t)
            del t
            support.gc_collect()
        self.assertIsNone(wr(), wr)
        with self.open(support.TESTFN, "rb") as f:
            self.assertEqual(f.read(), b"456def") 

def test_getbuffer(self):
        memio = self.ioclass(b"1234567890")
        buf = memio.getbuffer()
        self.assertEqual(bytes(buf), b"1234567890")
        memio.seek(5)
        buf = memio.getbuffer()
        self.assertEqual(bytes(buf), b"1234567890")
        # Trying to change the size of the BytesIO while a buffer is exported
        # raises a BufferError.
        self.assertRaises(BufferError, memio.write, b'x' * 100)
        self.assertRaises(BufferError, memio.truncate)
        self.assertRaises(BufferError, memio.close)
        self.assertFalse(memio.closed)
        # Mutating the buffer updates the BytesIO
        buf[3:6] = b"abc"
        self.assertEqual(bytes(buf), b"123abc7890")
        self.assertEqual(memio.getvalue(), b"123abc7890")
        # After the buffer gets released, we can resize and close the BytesIO
        # again
        del buf
        support.gc_collect()
        memio.truncate()
        memio.close()
        self.assertRaises(ValueError, memio.getbuffer) 

def test_destructor(self):
        record = []
        class MyFileIO(self.FileIO):
            def __del__(self):
                record.append(1)
                try:
                    f = super().__del__
                except AttributeError:
                    pass
                else:
                    f()
            def close(self):
                record.append(2)
                super().close()
            def flush(self):
                record.append(3)
                super().flush()
        with support.check_warnings(('', ResourceWarning)):
            f = MyFileIO(support.TESTFN, "wb")
            f.write(b"xxx")
            del f
            support.gc_collect()
            self.assertEqual(record, [1, 2, 3])
            with self.open(support.TESTFN, "rb") as f:
                self.assertEqual(f.read(), b"xxx") 

def test_dealloc_warn(self):
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        r = repr(sock)
        with self.assertWarns(ResourceWarning) as cm:
            sock = None
            support.gc_collect()
        self.assertIn(r, str(cm.warning.args[0]))
        # An open socket file object gets dereferenced after the socket
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        f = sock.makefile('rb')
        r = repr(sock)
        sock = None
        support.gc_collect()
        with self.assertWarns(ResourceWarning):
            f = None
            support.gc_collect() 

def test_IOBase_finalize(self):
        # Issue #12149: segmentation fault on _PyIOBase_finalize when both a
        # class which inherits IOBase and an object of this class are caught
        # in a reference cycle and close() is already in the method cache.
        class MyIO(self.IOBase):
            def close(self):
                pass

        # create an instance to populate the method cache
        MyIO()
        obj = MyIO()
        obj.obj = obj
        wr = weakref.ref(obj)
        del MyIO
        del obj
        support.gc_collect()
        self.assertIsNone(wr(), wr) 

def test_run_forever_keyboard_interrupt(self):
        # Python issue #22601: ensure that the temporary task created by
        # run_forever() consumes the KeyboardInterrupt and so don't log
        # a warning
        @asyncio.coroutine
        def raise_keyboard_interrupt():
            raise KeyboardInterrupt

        self.loop._process_events = mock.Mock()
        self.loop.call_exception_handler = mock.Mock()

        try:
            self.loop.run_until_complete(raise_keyboard_interrupt())
        except KeyboardInterrupt:
            pass
        self.loop.close()
        support.gc_collect()

        self.assertFalse(self.loop.call_exception_handler.called) 

def test_pipe_handle(self):
        h, _ = windows_utils.pipe(overlapped=(True, True))
        _winapi.CloseHandle(_)
        p = windows_utils.PipeHandle(h)
        self.assertEqual(p.fileno(), h)
        self.assertEqual(p.handle, h)

        # check garbage collection of p closes handle
        with warnings.catch_warnings():
            warnings.filterwarnings("ignore", "",  ResourceWarning)
            del p
            support.gc_collect()
        try:
            _winapi.CloseHandle(h)
        except OSError as e:
            self.assertEqual(e.winerror, 6)     # ERROR_INVALID_HANDLE
        else:
            raise RuntimeError('expected ERROR_INVALID_HANDLE') 

def test_subtype_resurrection(self):
        # Testing resurrection of new-style instance...

        class C(object):
            container = []

            def __del__(self):
                # resurrect the instance
                C.container.append(self)

        c = C()
        c.attr = 42

        # The most interesting thing here is whether this blows up, due to
        # flawed GC tracking logic in typeobject.c's call_finalizer() (a 2.2.1
        # bug).
        del c

        support.gc_collect()
        self.assertEqual(len(C.container), 1)

        # Make c mortal again, so that the test framework with -l doesn't report
        # it as a leak.
        del C.__del__ 

def test_subtype_resurrection(self):
        # Testing resurrection of new-style instance...

        class C(object):
            container = []

            def __del__(self):
                # resurrect the instance
                C.container.append(self)

        c = C()
        c.attr = 42

        # The most interesting thing here is whether this blows up, due to
        # flawed GC tracking logic in typeobject.c's call_finalizer() (a 2.2.1
        # bug).
        del c

        support.gc_collect()
        self.assertEqual(len(C.container), 1)

        # Make c mortal again, so that the test framework with -l doesn't report
        # it as a leak.
        del C.__del__ 

def test_pipe_handle(self):
        h, _ = windows_utils.pipe(overlapped=(True, True))
        _winapi.CloseHandle(_)
        p = windows_utils.PipeHandle(h)
        self.assertEqual(p.fileno(), h)
        self.assertEqual(p.handle, h)

        # check garbage collection of p closes handle
        with warnings.catch_warnings():
            warnings.filterwarnings("ignore", "",  ResourceWarning)
            del p
            support.gc_collect()
        try:
            _winapi.CloseHandle(h)
        except OSError as e:
            self.assertEqual(e.winerror, 6)     # ERROR_INVALID_HANDLE
        else:
            raise RuntimeError('expected ERROR_INVALID_HANDLE') 

def test_destructor(self):
        record = []
        class MyFileIO(self.FileIO):
            def __del__(self):
                record.append(1)
                try:
                    f = super().__del__
                except AttributeError:
                    pass
                else:
                    f()
            def close(self):
                record.append(2)
                super().close()
            def flush(self):
                record.append(3)
                super().flush()
        with support.check_warnings(('', ResourceWarning)):
            f = MyFileIO(support.TESTFN, "wb")
            f.write(b"xxx")
            del f
            support.gc_collect()
            self.assertEqual(record, [1, 2, 3])
            with self.open(support.TESTFN, "rb") as f:
                self.assertEqual(f.read(), b"xxx") 

def test_dealloc_warn(self):
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        r = repr(sock)
        with self.assertWarns(ResourceWarning) as cm:
            sock = None
            support.gc_collect()
        self.assertIn(r, str(cm.warning.args[0]))
        # An open socket file object gets dereferenced after the socket
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        f = sock.makefile('rb')
        r = repr(sock)
        sock = None
        support.gc_collect()
        with self.assertWarns(ResourceWarning):
            f = None
            support.gc_collect() 

def test_getbuffer(self):
        memio = self.ioclass(b"1234567890")
        buf = memio.getbuffer()
        self.assertEqual(bytes(buf), b"1234567890")
        memio.seek(5)
        buf = memio.getbuffer()
        self.assertEqual(bytes(buf), b"1234567890")
        # Trying to change the size of the BytesIO while a buffer is exported
        # raises a BufferError.
        self.assertRaises(BufferError, memio.write, b'x' * 100)
        self.assertRaises(BufferError, memio.truncate)
        self.assertRaises(BufferError, memio.close)
        self.assertFalse(memio.closed)
        # Mutating the buffer updates the BytesIO
        buf[3:6] = b"abc"
        self.assertEqual(bytes(buf), b"123abc7890")
        self.assertEqual(memio.getvalue(), b"123abc7890")
        # After the buffer gets released, we can resize and close the BytesIO
        # again
        del buf
        support.gc_collect()
        memio.truncate()
        memio.close()
        self.assertRaises(ValueError, memio.getbuffer) 

def test_refcycle(self):
        # A generator caught in a refcycle gets finalized anyway.
        old_garbage = gc.garbage[:]
        finalized = False
        def gen():
            nonlocal finalized
            try:
                g = yield
                yield 1
            finally:
                finalized = True

        g = gen()
        next(g)
        g.send(g)
        self.assertGreater(sys.getrefcount(g), 2)
        self.assertFalse(finalized)
        del g
        support.gc_collect()
        self.assertTrue(finalized)
        self.assertEqual(gc.garbage, old_garbage) 

def test_override_destructor(self):
        record = []
        class MyTextIO(self.TextIOWrapper):
            def __del__(self):
                record.append(1)
                try:
                    f = super().__del__
                except AttributeError:
                    pass
                else:
                    f()
            def close(self):
                record.append(2)
                super().close()
            def flush(self):
                record.append(3)
                super().flush()
        b = self.BytesIO()
        t = MyTextIO(b, encoding="ascii")
        del t
        support.gc_collect()
        self.assertEqual(record, [1, 2, 3]) 

def test_garbage_collection(self):
        # C TextIOWrapper objects are collected, and collecting them flushes
        # all data to disk.
        # The Python version has __del__, so it ends in gc.garbage instead.
        with support.check_warnings(('', ResourceWarning)):
            rawio = io.FileIO(support.TESTFN, "wb")
            b = self.BufferedWriter(rawio)
            t = self.TextIOWrapper(b, encoding="ascii")
            t.write("456def")
            t.x = t
            wr = weakref.ref(t)
            del t
            support.gc_collect()
        self.assertIsNone(wr(), wr)
        with self.open(support.TESTFN, "rb") as f:
            self.assertEqual(f.read(), b"456def") 

def test_run_forever_keyboard_interrupt(self):
        # Python issue #22601: ensure that the temporary task created by
        # run_forever() consumes the KeyboardInterrupt and so don't log
        # a warning
        @asyncio.coroutine
        def raise_keyboard_interrupt():
            raise KeyboardInterrupt

        self.loop._process_events = mock.Mock()
        self.loop.call_exception_handler = mock.Mock()

        try:
            self.loop.run_until_complete(raise_keyboard_interrupt())
        except KeyboardInterrupt:
            pass
        self.loop.close()
        support.gc_collect()

        self.assertFalse(self.loop.call_exception_handler.called) 

def test_pipe_handle(self):
        h, _ = windows_utils.pipe(overlapped=(True, True))
        _winapi.CloseHandle(_)
        p = windows_utils.PipeHandle(h)
        self.assertEqual(p.fileno(), h)
        self.assertEqual(p.handle, h)

        # check garbage collection of p closes handle
        with warnings.catch_warnings():
            warnings.filterwarnings("ignore", "",  ResourceWarning)
            del p
            support.gc_collect()
        try:
            _winapi.CloseHandle(h)
        except OSError as e:
            self.assertEqual(e.winerror, 6)     # ERROR_INVALID_HANDLE
        else:
            raise RuntimeError('expected ERROR_INVALID_HANDLE') 

def test_delete_hook(self):
        # Testing __del__ hook...
        log = []
        class C(object):
            def __del__(self):
                log.append(1)
        c = C()
        self.assertEqual(log, [])
        del c
        support.gc_collect()
        self.assertEqual(log, [1])

        class D(object): pass
        d = D()
        try: del d[0]
        except TypeError: pass
        else: self.fail("invalid del() didn't raise TypeError") 

def test_delete_hook(self):
        # Testing __del__ hook...
        log = []
        class C(object):
            def __del__(self):
                log.append(1)
        c = C()
        self.assertEqual(log, [])
        del c
        support.gc_collect()
        self.assertEqual(log, [1])

        class D(object): pass
        d = D()
        try: del d[0]
        except TypeError: pass
        else: self.fail("invalid del() didn't raise TypeError") 

def test_rwpair_cleared_before_textio(self):
        # Issue 13070: TextIOWrapper's finalization would crash when called
        # after the reference to the underlying BufferedRWPair's writer got
        # cleared by the GC.
        for i in range(1000):
            b1 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
            t1 = self.TextIOWrapper(b1, encoding="ascii")
            b2 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
            t2 = self.TextIOWrapper(b2, encoding="ascii")
            # circular references
            t1.buddy = t2
            t2.buddy = t1
        support.gc_collect() 

def test_lock_lifetime(self):
        name = "xyzzy"
        self.assertNotIn(name, self.bootstrap._module_locks)
        lock = self.bootstrap._get_module_lock(name)
        self.assertIn(name, self.bootstrap._module_locks)
        wr = weakref.ref(lock)
        del lock
        support.gc_collect()
        self.assertNotIn(name, self.bootstrap._module_locks)
        self.assertIsNone(wr()) 

def test_destructor(self):
        writer = self.MockRawIO()
        bufio = self.tp(writer, 8)
        bufio.write(b"abc")
        del bufio
        support.gc_collect()
        self.assertEqual(b"abc", writer._write_stack[0]) 

def test_AST_garbage_collection(self):
        class X:
            pass
        a = ast.AST()
        a.x = X()
        a.x.a = a
        ref = weakref.ref(a.x)
        del a
        support.gc_collect()
        self.assertIsNone(ref()) 

def test_override_destructor(self):
        tp = self.tp
        record = []
        class MyBufferedIO(tp):
            def __del__(self):
                record.append(1)
                try:
                    f = super().__del__
                except AttributeError:
                    pass
                else:
                    f()
            def close(self):
                record.append(2)
                super().close()
            def flush(self):
                record.append(3)
                super().flush()
        rawio = self.MockRawIO()
        bufio = MyBufferedIO(rawio)
        writable = bufio.writable()
        del bufio
        support.gc_collect()
        if writable:
            self.assertEqual(record, [1, 2, 3])
        else:
            self.assertEqual(record, [1, 2]) 

def test_nonbuffered_textio(self):
        with warnings.catch_warnings(record=True) as recorded:
            with self.assertRaises(ValueError):
                self.open(support.TESTFN, 'w', buffering=0)
            support.gc_collect()
        self.assertEqual(recorded, [])