To reproduce:

• create a proxy factory
• duplicate it
• free both the original and the duplicate

Expected result: no runtime errors

Actual result: Whichever proxy factory is freed first is freed successfully, destroying the underlying proxy manager. Now the other proxy factory has a dangling pointer to a freed proxy manager. When the second proxy factory is freed, GLib will make an attempt to throw a critical warning:

not ok /libproxy/dup - GLib-GObject-FATAL-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed

but this is undefined behaviour, so it might equally well just crash.