New submission from Robin Schreiber:
As with every type, that has been created and initialized, HeapTypes created
form PyType_FromSpecWithBases() have to pass through PyType_Ready(). Here the
function inherit_special might be called, which, among other things, does the
following:
....
3892 if (base != &PyBaseObject_Type ||
3893 (type->tp_flags & Py_TPFLAGS_HEAPTYPE)) {
3894 if (type->tp_new == NULL)
3895 type->tp_new = base->tp_new;
3896 }
....
The code does not know of Heaptypes that have been created from extension-types
by the PEP 384 refactorings. This includes extension-types that do not specify
a tp_new method but instead have seperate factory methods, that are only used
within the extension module. inherit_special() might consequently assign
inappropriate new-methods to these type objects.
To circumvent this issue, I propose to enhance PyType_FromSpecWithBases in the
following way: If no tp_new has been specified, we assign the newly defined
PySpec_New() method to tp_new which simply denies the user to create an
instance of this type. This also prohibits inherit_special to falsely inherit
inappropriate new-methods.
----------
components: Interpreter Core
files: PyType_FromSpecWithBases_tp_new_fix.patch
keywords: patch
messages: 168579
nosy: Robin.Schreiber, loewis
priority: normal
severity: normal
status: open
title: PyType_FromSpecWithBases tp_new bugfix
type: behavior
versions: Python 3.4
Added file:
http://bugs.python.org/file26897/PyType_FromSpecWithBases_tp_new_fix.patch
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<http://bugs.python.org/issue15727>
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