Merge branch 'backport/jc/http-clear-finished-pointer' into maint-2.30

Meant to go with js/ci-gcc-12-fixes.
source: <xmqq7d68ytj8.fsf_-_@gitster.g>

* jc/http-clear-finished-pointer:
  http.c: clear the 'finished' member once we are done with it

http.c

@@ -1523,6 +1523,32 @@ void run_active_slot(struct active_request_slot *slot)
 		finish_active_slot(slot);
 	}
 #endif
+
+	/*
+	 * The value of slot->finished we set before the loop was used
+	 * to set our "finished" variable when our request completed.
+	 *
+	 * 1. The slot may not have been reused for another requst
+	 *    yet, in which case it still has &finished.
+	 *
+	 * 2. The slot may already be in-use to serve another request,
+	 *    which can further be divided into two cases:
+	 *
+	 * (a) If call run_active_slot() hasn't been called for that
+	 *     other request, slot->finished would have been cleared
+	 *     by get_active_slot() and has NULL.
+	 *
+	 * (b) If the request did call run_active_slot(), then the
+	 *     call would have updated slot->finished at the beginning
+	 *     of this function, and with the clearing of the member
+	 *     below, we would find that slot->finished is now NULL.
+	 *
+	 * In all cases, slot->finished has no useful information to
+	 * anybody at this point.  Some compilers warn us for
+	 * attempting to smuggle a pointer that is about to become
+	 * invalid, i.e. &finished.  We clear it here to assure them.
+	 */
+	slot->finished = NULL;
 }
 
 static void release_active_slot(struct active_request_slot *slot)