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[3.8] bpo-41993: Fix possible issues in remove_module() (GH-22631) #22649

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[3.8] bpo-41993: Fix possible issues in remove_module() (GH-22631) #22649

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2020-10-10-13-53-52.bpo-41993.YMzixQ.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fixed potential issues with removing not completely initialized module from
``sys.modules`` when import fails.
25 changes: 16 additions & 9 deletions Python/import.c
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Original file line number Diff line number Diff line change
Expand Up @@ -845,22 +845,29 @@ PyImport_AddModule(const char *name)
}


/* Remove name from sys.modules, if it's there. */
/* Remove name from sys.modules, if it's there.
* Can be called with an exception raised.
* If fail to remove name a new exception will be chained with the old
* exception, otherwise the old exception is preserved.
*/
static void
remove_module(PyObject *name)
{
PyObject *type, *value, *traceback;
PyErr_Fetch(&type, &value, &traceback);
PyObject *modules = PyImport_GetModuleDict();
if (!PyMapping_HasKey(modules, name)) {
goto out;

PyObject *modules = tstate->interp->modules;
if (PyDict_CheckExact(modules)) {
PyObject *mod = _PyDict_Pop(modules, name, Py_None);
Py_XDECREF(mod);
}
if (PyMapping_DelItem(modules, name) < 0) {
Py_FatalError("import: deleting existing key in "
"sys.modules failed");
else if (PyMapping_DelItem(modules, name) < 0) {
if (PyErr_ExceptionMatches(PyExc_KeyError)) {
PyErr_Clear();
}
}
out:
PyErr_Restore(type, value, traceback);

_PyErr_ChainExceptions(type, value, traceback);
}


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