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# Test the most dynamic corner cases of Python's runtime semantics.
import builtins
import sys
import unittest
from test.support import swap_item, swap_attr
class RebindBuiltinsTests(unittest.TestCase):
"""Test all the ways that we can change/shadow globals/builtins."""
def configure_func(self, func, *args):
"""Perform TestCase-specific configuration on a function before testing.
By default, this does nothing. Example usage: spinning a function so
that a JIT will optimize it. Subclasses should override this as needed.
Args:
func: function to configure.
*args: any arguments that should be passed to func, if calling it.
Returns:
Nothing. Work will be performed on func in-place.
"""
pass
def test_globals_shadow_builtins(self):
# Modify globals() to shadow an entry in builtins.
def foo():
return len([1, 2, 3])
self.configure_func(foo)
self.assertEqual(foo(), 3)
with swap_item(globals(), "len", lambda x: 7):
self.assertEqual(foo(), 7)
def test_modify_builtins(self):
# Modify the builtins module directly.
def foo():
return len([1, 2, 3])
self.configure_func(foo)
self.assertEqual(foo(), 3)
with swap_attr(builtins, "len", lambda x: 7):
self.assertEqual(foo(), 7)
def test_modify_builtins_while_generator_active(self):
# Modify the builtins out from under a live generator.
def foo():
x = range(3)
yield len(x)
yield len(x)
self.configure_func(foo)
g = foo()
self.assertEqual(next(g), 3)
with swap_attr(builtins, "len", lambda x: 7):
self.assertEqual(next(g), 7)
def test_modify_builtins_from_leaf_function(self):
# Verify that modifications made by leaf functions percolate up the
# callstack.
with swap_attr(builtins, "len", len):
def bar():
builtins.len = lambda x: 4
def foo(modifier):
l = []
l.append(len(range(7)))
modifier()
l.append(len(range(7)))
return l
self.configure_func(foo, lambda: None)
self.assertEqual(foo(bar), [7, 4])
def test_cannot_change_globals_or_builtins_with_eval(self):
def foo():
return len([1, 2, 3])
self.configure_func(foo)
# Note that this *doesn't* change the definition of len() seen by foo().
builtins_dict = {"len": lambda x: 7}
globals_dict = {"foo": foo, "__builtins__": builtins_dict,
"len": lambda x: 8}
self.assertEqual(eval("foo()", globals_dict), 3)
self.assertEqual(eval("foo()", {"foo": foo}), 3)
def test_cannot_change_globals_or_builtins_with_exec(self):
def foo():
return len([1, 2, 3])
self.configure_func(foo)
globals_dict = {"foo": foo}
exec("x = foo()", globals_dict)
self.assertEqual(globals_dict["x"], 3)
# Note that this *doesn't* change the definition of len() seen by foo().
builtins_dict = {"len": lambda x: 7}
globals_dict = {"foo": foo, "__builtins__": builtins_dict,
"len": lambda x: 8}
exec("x = foo()", globals_dict)
self.assertEqual(globals_dict["x"], 3)
def test_cannot_replace_builtins_dict_while_active(self):
def foo():
x = range(3)
yield len(x)
yield len(x)
self.configure_func(foo)
g = foo()
self.assertEqual(next(g), 3)
with swap_item(globals(), "__builtins__", {"len": lambda x: 7}):
self.assertEqual(next(g), 3)
def test_cannot_replace_builtins_dict_between_calls(self):
def foo():
return len([1, 2, 3])
self.configure_func(foo)
self.assertEqual(foo(), 3)
with swap_item(globals(), "__builtins__", {"len": lambda x: 7}):
self.assertEqual(foo(), 3)
def test_eval_gives_lambda_custom_globals(self):
globals_dict = {"len": lambda x: 7}
foo = eval("lambda: len([])", globals_dict)
self.configure_func(foo)
self.assertEqual(foo(), 7)
def test_load_global_specialization_failure_keeps_oparg(self):
# https://github.com/python/cpython/issues/91625
class MyGlobals(dict):
def __missing__(self, key):
return int(key.removeprefix("_number_"))
# Need more than 256 variables to use EXTENDED_ARGS
variables = 400
code = "lambda: " + "+".join(f"_number_{i}" for i in range(variables))
sum_func = eval(code, MyGlobals())
expected = sum(range(variables))
# Warm up the function for quickening (PEP 659)
for _ in range(30):
self.assertEqual(sum_func(), expected)
class TestTracing(unittest.TestCase):
def setUp(self):
self.addCleanup(sys.settrace, sys.gettrace())
sys.settrace(None)
def test_after_specialization(self):
def trace(frame, event, arg):
return trace
turn_on_trace = False
class C:
def __init__(self, x):
self.x = x
def __del__(self):
if turn_on_trace:
sys.settrace(trace)
def f():
# LOAD_GLOBAL[_BUILTIN] immediately follows the call to C.__del__
C(0).x, len
def g():
# BINARY_SUSCR[_LIST_INT] immediately follows the call to C.__del__
[0][C(0).x]
def h():
# BINARY_OP[_ADD_INT] immediately follows the call to C.__del__
0 + C(0).x
for func in (f, g, h):
with self.subTest(func.__name__):
for _ in range(58):
func()
turn_on_trace = True
func()
sys.settrace(None)
turn_on_trace = False
if __name__ == "__main__":
unittest.main()
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