cpython/Lib/test/test_frame.py

447 lines
14 KiB
Python

import gc
import operator
import re
import sys
import textwrap
import threading
import types
import unittest
import weakref
try:
import _testcapi
except ImportError:
_testcapi = None
from test import support
from test.support import threading_helper
from test.support.script_helper import assert_python_ok
class ClearTest(unittest.TestCase):
"""
Tests for frame.clear().
"""
def inner(self, x=5, **kwargs):
1/0
def outer(self, **kwargs):
try:
self.inner(**kwargs)
except ZeroDivisionError as e:
exc = e
return exc
def clear_traceback_frames(self, tb):
"""
Clear all frames in a traceback.
"""
while tb is not None:
tb.tb_frame.clear()
tb = tb.tb_next
def test_clear_locals(self):
class C:
pass
c = C()
wr = weakref.ref(c)
exc = self.outer(c=c)
del c
support.gc_collect()
# A reference to c is held through the frames
self.assertIsNot(None, wr())
self.clear_traceback_frames(exc.__traceback__)
support.gc_collect()
# The reference was released by .clear()
self.assertIs(None, wr())
def test_clear_does_not_clear_specials(self):
class C:
pass
c = C()
exc = self.outer(c=c)
del c
f = exc.__traceback__.tb_frame
f.clear()
self.assertIsNot(f.f_code, None)
self.assertIsNot(f.f_locals, None)
self.assertIsNot(f.f_builtins, None)
self.assertIsNot(f.f_globals, None)
def test_clear_generator(self):
endly = False
def g():
nonlocal endly
try:
yield
self.inner()
finally:
endly = True
gen = g()
next(gen)
self.assertFalse(endly)
# Cannot clear a suspended frame
with self.assertRaisesRegex(RuntimeError, r'suspended frame'):
gen.gi_frame.clear()
self.assertFalse(endly)
def test_clear_executing(self):
# Attempting to clear an executing frame is forbidden.
try:
1/0
except ZeroDivisionError as e:
f = e.__traceback__.tb_frame
with self.assertRaises(RuntimeError):
f.clear()
with self.assertRaises(RuntimeError):
f.f_back.clear()
def test_clear_executing_generator(self):
# Attempting to clear an executing generator frame is forbidden.
endly = False
def g():
nonlocal endly
try:
1/0
except ZeroDivisionError as e:
f = e.__traceback__.tb_frame
with self.assertRaises(RuntimeError):
f.clear()
with self.assertRaises(RuntimeError):
f.f_back.clear()
yield f
finally:
endly = True
gen = g()
f = next(gen)
self.assertFalse(endly)
# Cannot clear a suspended frame
with self.assertRaisesRegex(RuntimeError, 'suspended frame'):
f.clear()
self.assertFalse(endly)
def test_lineno_with_tracing(self):
def record_line():
f = sys._getframe(1)
lines.append(f.f_lineno-f.f_code.co_firstlineno)
def test(trace):
record_line()
if trace:
sys._getframe(0).f_trace = True
record_line()
record_line()
expected_lines = [1, 4, 5]
lines = []
test(False)
self.assertEqual(lines, expected_lines)
lines = []
test(True)
self.assertEqual(lines, expected_lines)
@support.cpython_only
def test_clear_refcycles(self):
# .clear() doesn't leave any refcycle behind
with support.disable_gc():
class C:
pass
c = C()
wr = weakref.ref(c)
exc = self.outer(c=c)
del c
self.assertIsNot(None, wr())
self.clear_traceback_frames(exc.__traceback__)
self.assertIs(None, wr())
class FrameAttrsTest(unittest.TestCase):
def make_frames(self):
def outer():
x = 5
y = 6
def inner():
z = x + 2
1/0
t = 9
return inner()
try:
outer()
except ZeroDivisionError as e:
tb = e.__traceback__
frames = []
while tb:
frames.append(tb.tb_frame)
tb = tb.tb_next
return frames
def test_locals(self):
f, outer, inner = self.make_frames()
outer_locals = outer.f_locals
self.assertIsInstance(outer_locals.pop('inner'), types.FunctionType)
self.assertEqual(outer_locals, {'x': 5, 'y': 6})
inner_locals = inner.f_locals
self.assertEqual(inner_locals, {'x': 5, 'z': 7})
def test_clear_locals(self):
# Test f_locals after clear() (issue #21897)
f, outer, inner = self.make_frames()
outer.clear()
inner.clear()
self.assertEqual(outer.f_locals, {})
self.assertEqual(inner.f_locals, {})
def test_locals_clear_locals(self):
# Test f_locals before and after clear() (to exercise caching)
f, outer, inner = self.make_frames()
outer.f_locals
inner.f_locals
outer.clear()
inner.clear()
self.assertEqual(outer.f_locals, {})
self.assertEqual(inner.f_locals, {})
def test_f_lineno_del_segfault(self):
f, _, _ = self.make_frames()
with self.assertRaises(AttributeError):
del f.f_lineno
class ReprTest(unittest.TestCase):
"""
Tests for repr(frame).
"""
def test_repr(self):
def outer():
x = 5
y = 6
def inner():
z = x + 2
1/0
t = 9
return inner()
offset = outer.__code__.co_firstlineno
try:
outer()
except ZeroDivisionError as e:
tb = e.__traceback__
frames = []
while tb:
frames.append(tb.tb_frame)
tb = tb.tb_next
else:
self.fail("should have raised")
f_this, f_outer, f_inner = frames
file_repr = re.escape(repr(__file__))
self.assertRegex(repr(f_this),
r"^<frame at 0x[0-9a-fA-F]+, file %s, line %d, code test_repr>$"
% (file_repr, offset + 23))
self.assertRegex(repr(f_outer),
r"^<frame at 0x[0-9a-fA-F]+, file %s, line %d, code outer>$"
% (file_repr, offset + 7))
self.assertRegex(repr(f_inner),
r"^<frame at 0x[0-9a-fA-F]+, file %s, line %d, code inner>$"
% (file_repr, offset + 5))
class TestIncompleteFrameAreInvisible(unittest.TestCase):
def test_issue95818(self):
# See GH-95818 for details
code = textwrap.dedent(f"""
import gc
gc.set_threshold(1,1,1)
class GCHello:
def __del__(self):
print("Destroyed from gc")
def gen():
yield
fd = open({__file__!r})
l = [fd, GCHello()]
l.append(l)
del fd
del l
gen()
""")
assert_python_ok("-c", code)
@support.cpython_only
def test_sneaky_frame_object(self):
def trace(frame, event, arg):
"""
Don't actually do anything, just force a frame object to be created.
"""
def callback(phase, info):
"""
Yo dawg, I heard you like frames, so I'm allocating a frame while
you're allocating a frame, so you can have a frame while you have a
frame!
"""
nonlocal sneaky_frame_object
sneaky_frame_object = sys._getframe().f_back.f_back
# We're done here:
gc.callbacks.remove(callback)
def f():
while True:
yield
old_threshold = gc.get_threshold()
old_callbacks = gc.callbacks[:]
old_enabled = gc.isenabled()
old_trace = sys.gettrace()
try:
# Stop the GC for a second while we set things up:
gc.disable()
# Create a paused generator:
g = f()
next(g)
# Move all objects to the oldest generation, and tell the GC to run
# on the *very next* allocation:
gc.collect()
gc.set_threshold(1, 0, 0)
# Okay, so here's the nightmare scenario:
# - We're tracing the resumption of a generator, which creates a new
# frame object.
# - The allocation of this frame object triggers a collection
# *before* the frame object is actually created.
# - During the collection, we request the exact same frame object.
# This test does it with a GC callback, but in real code it would
# likely be a trace function, weakref callback, or finalizer.
# - The collection finishes, and the original frame object is
# created. We now have two frame objects fighting over ownership
# of the same interpreter frame!
sys.settrace(trace)
gc.callbacks.append(callback)
sneaky_frame_object = None
gc.enable()
next(g)
# g.gi_frame should be the frame object from the callback (the
# one that was *requested* second, but *created* first):
self.assertIs(g.gi_frame, sneaky_frame_object)
finally:
gc.set_threshold(*old_threshold)
gc.callbacks[:] = old_callbacks
sys.settrace(old_trace)
if old_enabled:
gc.enable()
@support.cpython_only
@threading_helper.requires_working_threading()
def test_sneaky_frame_object_teardown(self):
class SneakyDel:
def __del__(self):
"""
Stash a reference to the entire stack for walking later.
It may look crazy, but you'd be surprised how common this is
when using a test runner (like pytest). The typical recipe is:
ResourceWarning + -Werror + a custom sys.unraisablehook.
"""
nonlocal sneaky_frame_object
sneaky_frame_object = sys._getframe()
class SneakyThread(threading.Thread):
"""
A separate thread isn't needed to make this code crash, but it does
make crashes more consistent, since it means sneaky_frame_object is
backed by freed memory after the thread completes!
"""
def run(self):
"""Run SneakyDel.__del__ as this frame is popped."""
ref = SneakyDel()
sneaky_frame_object = None
t = SneakyThread()
t.start()
t.join()
# sneaky_frame_object can be anything, really, but it's crucial that
# SneakyThread.run's frame isn't anywhere on the stack while it's being
# torn down:
self.assertIsNotNone(sneaky_frame_object)
while sneaky_frame_object is not None:
self.assertIsNot(
sneaky_frame_object.f_code, SneakyThread.run.__code__
)
sneaky_frame_object = sneaky_frame_object.f_back
def test_entry_frames_are_invisible_during_teardown(self):
class C:
"""A weakref'able class."""
def f():
"""Try to find globals and locals as this frame is being cleared."""
ref = C()
# Ignore the fact that exec(C()) is a nonsense callback. We're only
# using exec here because it tries to access the current frame's
# globals and locals. If it's trying to get those from a shim frame,
# we'll crash before raising:
return weakref.ref(ref, exec)
with support.catch_unraisable_exception() as catcher:
# Call from C, so there is a shim frame directly above f:
weak = operator.call(f) # BOOM!
# Cool, we didn't crash. Check that the callback actually happened:
self.assertIs(catcher.unraisable.exc_type, TypeError)
self.assertIsNone(weak())
@unittest.skipIf(_testcapi is None, 'need _testcapi')
class TestCAPI(unittest.TestCase):
def getframe(self):
return sys._getframe()
def test_frame_getters(self):
frame = self.getframe()
self.assertEqual(frame.f_locals, _testcapi.frame_getlocals(frame))
self.assertIs(frame.f_globals, _testcapi.frame_getglobals(frame))
self.assertIs(frame.f_builtins, _testcapi.frame_getbuiltins(frame))
self.assertEqual(frame.f_lasti, _testcapi.frame_getlasti(frame))
def test_getvar(self):
current_frame = sys._getframe()
x = 1
self.assertEqual(_testcapi.frame_getvar(current_frame, "x"), 1)
self.assertEqual(_testcapi.frame_getvarstring(current_frame, b"x"), 1)
with self.assertRaises(NameError):
_testcapi.frame_getvar(current_frame, "y")
with self.assertRaises(NameError):
_testcapi.frame_getvarstring(current_frame, b"y")
# wrong name type
with self.assertRaises(TypeError):
_testcapi.frame_getvar(current_frame, b'x')
with self.assertRaises(TypeError):
_testcapi.frame_getvar(current_frame, 123)
def getgenframe(self):
yield sys._getframe()
def test_frame_get_generator(self):
gen = self.getgenframe()
frame = next(gen)
self.assertIs(gen, _testcapi.frame_getgenerator(frame))
def test_frame_fback_api(self):
"""Test that accessing `f_back` does not cause a segmentation fault on
a frame created with `PyFrame_New` (GH-99110)."""
def dummy():
pass
frame = _testcapi.frame_new(dummy.__code__, globals(), locals())
# The following line should not cause a segmentation fault.
self.assertIsNone(frame.f_back)
if __name__ == "__main__":
unittest.main()