Store the signal index in QObjectPrivate::Connection, thereby making it available in "implicit" disconnect contexts (i.e., receiver deletion). This change does not cause the size of QObjectPrivate::Connection to grow (still 40 bytes on 32-bit Linux, 72 bytes on 64-bit Mac). Valgrinding the new benchmark indicates that the percentage of the time spent in the QObject destructor increased from 7.8% to 8.4% on ia32, for that particular stress test; the increase is the combined cost of calling metaObject(), QMetaObjectPrivate::signal(), and disconnectNotify() for one connection. In practice, the measured wallclock time increased by about 3ms for a 500ms run (which repeatedly constructs, connects, and destroys an object). Task-number: QTBUG-4844 Change-Id: I1beb01c753f31542fc0acb62edb4c6d165fcc5b4 Reviewed-by: Olivier Goffart <ogoffart@woboq.com> Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>