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bpo-32379: Faster MRO computation for single inheritance (#4932) 

* bpo-32379: Faster MRO computation for single inheritance
This commit is contained in:
Antoine Pitrou 2017-12-20 15:58:21 +01:00 committed by GitHub
parent 776407fe89
commit 1f1a34c314
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3 changed files with 43 additions and 4 deletions
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6
Lib/test/test_descr.py
View File

@ -1783,6 +1783,12 @@ order (MRO) for bases """
def f(self): return "C"
class D(B, C):
pass
self.assertEqual(A.mro(), [A, object])
self.assertEqual(A.__mro__, (A, object))
self.assertEqual(B.mro(), [B, A, object])
self.assertEqual(B.__mro__, (B, A, object))
self.assertEqual(C.mro(), [C, A, object])
self.assertEqual(C.__mro__, (C, A, object))
self.assertEqual(D.mro(), [D, B, C, A, object])
self.assertEqual(D.__mro__, (D, B, C, A, object))
self.assertEqual(D().f(), "C")

1
Misc/NEWS.d/next/Core and Builtins/2017-12-19-21-14-41.bpo-32379.B7mOmI.rst Normal file
View File

@ -0,0 +1 @@
Make MRO computation faster when a class inherits from a single base.

40
Objects/typeobject.c
View File

@ -1761,6 +1761,36 @@ mro_implementation(PyTypeObject *type)
return NULL;
}
bases = type->tp_bases;
n = PyTuple_GET_SIZE(bases);
if (n == 1) {
/* Fast path: if there is a single base, constructing the MRO
* is trivial.
*/
PyTypeObject *base = (PyTypeObject *)PyTuple_GET_ITEM(bases, 0);
Py_ssize_t k;
if (base->tp_mro == NULL) {
PyErr_Format(PyExc_TypeError,
"Cannot extend an incomplete type '%.100s'",
base->tp_name);
return NULL;
}
k = PyTuple_GET_SIZE(base->tp_mro);
result = PyTuple_New(k + 1);
if (result == NULL) {
return NULL;
}
Py_INCREF(type);
PyTuple_SET_ITEM(result, 0, (PyObject *) type);
for (i = 0; i < k; i++) {
PyObject *cls = PyTuple_GET_ITEM(base->tp_mro, i);
Py_INCREF(cls);
PyTuple_SET_ITEM(result, i + 1, cls);
}
return result;
}
/* Find a superclass linearization that honors the constraints
of the explicit lists of bases and the constraints implied by
each base class.
@ -1770,9 +1800,6 @@ mro_implementation(PyTypeObject *type)
to_merge is the declared list of bases.
*/
bases = type->tp_bases;
n = PyTuple_GET_SIZE(bases);
to_merge = PyList_New(n+1);
if (to_merge == NULL)
return NULL;
@ -1830,7 +1857,12 @@ static PyObject *
type_mro_impl(PyTypeObject *self)
/*[clinic end generated code: output=bffc4a39b5b57027 input=28414f4e156db28d]*/
{
return mro_implementation(self);
PyObject *seq;
seq = mro_implementation(self);
if (seq != NULL && !PyList_Check(seq)) {
Py_SETREF(seq, PySequence_List(seq));
}
return seq;
}
static int