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gh-118272: Clear generator frame's locals when the generator is closed #118277

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Merged
merged 2 commits into from
Apr 30, 2024
Merged

gh-118272: Clear generator frame's locals when the generator is closed #118277

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gh-118272: Clear generator frame's locals when the generator is closed
iritkatriel Apr 25, 2024
8a23ce1
support.gc_collect()
iritkatriel Apr 25, 2024
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gh-118272: Clear generator frame's locals when the generator is closed
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@iritkatriel
iritkatriel committed Apr 25, 2024
commit 66519f687708a5b0e697540df86103617d48455f
3 changes: 3 additions & 0 deletions Include/internal/pycore_frame.h
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Expand Up @@ -227,6 +227,9 @@ _PyFrame_GetFrameObject(_PyInterpreterFrame *frame)
return _PyFrame_MakeAndSetFrameObject(frame);
}

void
_PyFrame_ClearLocals(_PyInterpreterFrame *frame);

/* Clears all references in the frame.
* If take is non-zero, then the _PyInterpreterFrame frame
* may be transferred to the frame object it references
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20 changes: 20 additions & 0 deletions Lib/test/test_generators.py
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Expand Up @@ -532,6 +532,26 @@ def f():
with self.assertRaises(RuntimeError):
gen.close()

def test_close_releases_frame_locals(self):
# See gh-118272

class Foo:
pass

f = Foo()
f_wr = weakref.ref(f)

def genfn():
a = f
yield

g = genfn()
next(g)
del f
g.close()
gc.collect()
self.assertIsNone(f_wr())


class GeneratorThrowTest(unittest.TestCase):

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2024-04-25-12-55-47.gh-issue-118272.5ptjk_.rst
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@@ -0,0 +1,2 @@
Fix bug where ``generator.close`` does not free the generator frame's
locals.
1 change: 1 addition & 0 deletions Objects/genobject.c
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Expand Up @@ -380,6 +380,7 @@ gen_close(PyGenObject *gen, PyObject *args)
// RESUME after YIELD_VALUE and exception depth is 1
assert((oparg & RESUME_OPARG_LOCATION_MASK) != RESUME_AT_FUNC_START);
gen->gi_frame_state = FRAME_COMPLETED;
_PyFrame_ClearLocals((_PyInterpreterFrame *)gen->gi_iframe);
Py_RETURN_NONE;
}
}
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17 changes: 12 additions & 5 deletions Python/frame.c
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Expand Up @@ -94,6 +94,17 @@ take_ownership(PyFrameObject *f, _PyInterpreterFrame *frame)
}
}

void
_PyFrame_ClearLocals(_PyInterpreterFrame *frame)
{
assert(frame->stacktop >= 0);
for (int i = 0; i < frame->stacktop; i++) {
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I think frame->stacktop = 0; needs to come before the loop to prevent the GC seeing freed objects.

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@gvanrossum gvanrossum May 1, 2024 •
edited
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Let me make a fix for that. NM, approved gh-118478 instead.

Py_XDECREF(frame->localsplus[i]);
}
frame->stacktop = 0;
Py_CLEAR(frame->f_locals);
}

void
_PyFrame_ClearExceptCode(_PyInterpreterFrame *frame)
{
Expand All @@ -114,11 +125,7 @@ _PyFrame_ClearExceptCode(_PyInterpreterFrame *frame)
}
Py_DECREF(f);
}
assert(frame->stacktop >= 0);
for (int i = 0; i < frame->stacktop; i++) {
Py_XDECREF(frame->localsplus[i]);
}
Py_XDECREF(frame->f_locals);
_PyFrame_ClearLocals(frame);
Py_DECREF(frame->f_funcobj);
}

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