Manual py3k backport: [svn r74155] Issue #6242: Fix deallocator of io.StringIO and io.BytesIO
diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index ed2f7cc..f477550 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -616,11 +616,14 @@
 static void
 bytesio_dealloc(bytesio *self)
 {
+    _PyObject_GC_UNTRACK(self);
     if (self->buf != NULL) {
         PyMem_Free(self->buf);
         self->buf = NULL;
     }
-    Py_TYPE(self)->tp_clear((PyObject *)self);
+    Py_CLEAR(self->dict);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *) self);
     Py_TYPE(self)->tp_free(self);
 }
 
@@ -674,7 +677,6 @@
 bytesio_traverse(bytesio *self, visitproc visit, void *arg)
 {
     Py_VISIT(self->dict);
-    Py_VISIT(self->weakreflist);
     return 0;
 }
 
@@ -682,8 +684,6 @@
 bytesio_clear(bytesio *self)
 {
     Py_CLEAR(self->dict);
-    if (self->weakreflist != NULL)
-        PyObject_ClearWeakRefs((PyObject *)self);
     return 0;
 }
 
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index ddb081d..95180a9 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -515,11 +515,15 @@
 stringio_dealloc(stringio *self)
 {
     _PyObject_GC_UNTRACK(self);
+    self->ok = 0;
+    if (self->buf) {
+        PyMem_Free(self->buf);
+        self->buf = NULL;
+    }
     Py_CLEAR(self->readnl);
     Py_CLEAR(self->writenl);
     Py_CLEAR(self->decoder);
-    if (self->buf)
-        PyMem_Free(self->buf);
+    Py_CLEAR(self->dict);
     if (self->weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *) self);
     Py_TYPE(self)->tp_free(self);