Rewrite tp_dealloc() of fused types functions to correctly disable GC before...

Rewrite tp_dealloc() of fused types functions to correctly disable GC before starting to clean up references.

CHANGES.rst

@@ -38,6 +38,9 @@ Bugs fixed
 * Annotations could be parsed (and rejected) as types even with
   ``annotation_typing=False``.
 
+* Deallocating fused types functions and methods kept their GC tracking enabled,
+  which could lead to crashes.
+
 
 0.27 (2017-09-23)
 =================

Cython/Utility/CythonFunction.c

@@ -505,15 +505,20 @@ __Pyx_CyFunction_clear(__pyx_CyFunctionObject *m)
     return 0;
 }
 
-static void __Pyx_CyFunction_dealloc(__pyx_CyFunctionObject *m)
+static void __Pyx__CyFunction_dealloc(__pyx_CyFunctionObject *m)
 {
-    PyObject_GC_UnTrack(m);
     if (__Pyx_CyFunction_weakreflist(m) != NULL)
         PyObject_ClearWeakRefs((PyObject *) m);
     __Pyx_CyFunction_clear(m);
     PyObject_GC_Del(m);
 }
 
+static void __Pyx_CyFunction_dealloc(__pyx_CyFunctionObject *m)
+{
+    PyObject_GC_UnTrack(m);
+    __Pyx__CyFunction_dealloc(m);
+}
+
 static int __Pyx_CyFunction_traverse(__pyx_CyFunctionObject *m, visitproc visit, void *arg)
 {
     Py_VISIT(m->func_closure);
@@ -830,9 +835,14 @@ __pyx_FusedFunction_New(PyTypeObject *type, PyMethodDef *ml, int flags,
     return (PyObject *) fusedfunc;
 }
 
-static void __pyx_FusedFunction_dealloc(__pyx_FusedFunctionObject *self) {
-    __pyx_FusedFunction_clear(self);
-    __pyx_FusedFunctionType->tp_free((PyObject *) self);
+static void
+__pyx_FusedFunction_dealloc(__pyx_FusedFunctionObject *self)
+{
+    PyObject_GC_UnTrack(self);
+    Py_CLEAR(self->self);
+    Py_CLEAR(self->type);
+    Py_CLEAR(self->__signatures__);
+    __Pyx__CyFunction_dealloc((__pyx_CyFunctionObject *) self);
 }
 
 static int