connection != NULL assertion in dbus-python

[Simon McVittie]

J5,
This commit (in my dbus-python git branch on fd.o) might fix your crash -
it's the only way I can see that a referenced Connection might get a NULL
DBusConnection. I'll introduce some more checks anyway, though.

commit 380b44d38d333092bc9fe2eae8b7a836cb2791c7
Author: Simon McVittie <simon.mcvittie at collabora.co.uk>
Date:   Fri Dec 8 16:10:12 2006 +0000

    _dbus_bindings/conn-impl.h: Be more careful that referenced Connections always have a DBusConnection

---
 _dbus_bindings/conn-impl.h |   26 ++++++++++++++++++++++----
 1 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/_dbus_bindings/conn-impl.h b/_dbus_bindings/conn-impl.h
index 3c87e4e..4396a04 100644
--- a/_dbus_bindings/conn-impl.h
+++ b/_dbus_bindings/conn-impl.h
@@ -243,11 +243,19 @@ static dbus_int32_t _connection_python_slot;
 static DBusConnection *
 Connection_BorrowDBusConnection(PyObject *self)
 {
+    DBusConnection *dbc;
+
     if (!Connection_Check(self)) {
         PyErr_SetString(PyExc_TypeError, "A dbus.Connection is required");
         return NULL;
     }
-    return ((Connection *)self)->conn;
+    dbc = ((Connection *)self)->conn;
+    if (!dbc) {
+        PyErr_SetString(PyExc_RuntimeError, "Connection is in an invalid "
+                        "state: no DBusConnection");
+        return NULL;
+    }
+    return dbc;
 }
 
 /* Internal C API =================================================== */
@@ -480,10 +488,22 @@ Connection_tp_new(PyTypeObject *cls, PyObject *args, PyObject *kwargs)
 static void Connection_tp_dealloc(Connection *self)
 {
     DBusConnection *conn = self->conn;
-    self->conn = NULL;
+    PyObject *filters = self->filters;
+    PyObject *object_paths = self->object_paths;
 
     DBG("Deallocating Connection at %p (DBusConnection at %p)", self, conn);
 
+    self->filters = NULL;
+    Py_XDECREF(filters);
+    self->object_paths = NULL;
+    Py_XDECREF(object_paths);
+
+    /* make sure to do this last to preserve the invariant that 
+     * self->conn is always non-NULL for any referenced Connection
+     * (until the filters and object paths were freed, we might have been
+     * in a reference cycle!)
+     */
+    self->conn = NULL;
     if (conn) {
         Py_BEGIN_ALLOW_THREADS
         dbus_connection_close(conn);
@@ -492,8 +512,6 @@ static void Connection_tp_dealloc(Connection *self)
         dbus_connection_unref(conn);
     }
 
-    Py_XDECREF(self->filters);
-    Py_XDECREF(self->object_paths);
     (self->ob_type->tp_free)((PyObject *)self);
 }