def test_alias_delay_initialization1(capture):
"""`A` only initializes its trampoline class when we inherit from it
If we just create and use an A instance directly, the trampoline initialization is
bypassed and we only initialize an A() instead (for performance reasons).
"""
class B(m.A):
def __init__(self):
super(B, self).__init__()
def f(self):
print("In python f()")
# C++ version
with capture:
a = m.A()
m.call_f(a)
del a
pytest.gc_collect()
assert capture == "A.f()"
# Python version
with capture:
b = B()
m.call_f(b)
del b
pytest.gc_collect()
assert capture == """
def test_alias_delay_initialization1(capture):
"""`A` only initializes its trampoline class when we inherit from it
If we just create and use an A instance directly, the trampoline initialization is
bypassed and we only initialize an A() instead (for performance reasons).
"""
class B(m.A):
def __init__(self):
super(B, self).__init__()
def f(self):
print("In python f()")
# C++ version
with capture:
a = m.A()
m.call_f(a)
del a
pytest.gc_collect()
assert capture == "A.f()"
# Python version
with capture:
b = B()
m.call_f(b)
del b
pytest.gc_collect()
assert capture == """
def test_alias_delay_initialization2(capture):
"""`A2`, unlike the above, is configured to always initialize the alias
While the extra initialization and extra class layer has small virtual dispatch
performance penalty, it also allows us to do more things with the trampoline
class such as defining local variables and performing construction/destruction.
"""
class B2(m.A2):
def __init__(self):
super(B2, self).__init__()
def f(self):
print("In python B2.f()")
# No python subclass version
with capture:
a2 = m.A2()
m.call_f(a2)
del a2
pytest.gc_collect()
assert capture == """
PyA2.PyA2()
PyA2.f()
A2.f()
PyA2.~PyA2()
"""
# Python subclass version
with capture:
b2 = B2()
m.call_f(b2)
del b2
pytest.gc_collect()
assert capture == """