Fix bogus CALLED_AS_TRIGGER() defenses.

contrib/lo's lo_manage() thought it could use
trigdata->tg_trigger->tgname in its error message about
not being called as a trigger.  That naturally led to a core dump.

unique_key_recheck() figured it could Assert that fcinfo->context
is a TriggerData node in advance of having checked that it's
being called as a trigger.  That's harmless in production builds,
and perhaps not that easy to reach in any case, but it's logically
wrong.

The first of these per bug #16340 from William Crowell;
the second from manual inspection of other CALLED_AS_TRIGGER
call sites.

Back-patch the lo.c change to all supported branches, the
other to v10 where the thinko crept in.

Discussion: https://postgr.es/m/16340-591c7449dc7c8c47@postgresql.org

Author: tglsfdc

contrib/lo/lo.c

@@ -33,8 +33,7 @@ lo_manage(PG_FUNCTION_ARGS)
 	HeapTuple	trigtuple;		/* The original value of tuple	*/
 
 	if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
-		elog(ERROR, "%s: not fired by trigger manager",
-			 trigdata->tg_trigger->tgname);
+		elog(ERROR, "lo_manage: not fired by trigger manager");
 
 	if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) /* internal error */
 		elog(ERROR, "%s: must be fired for row",

src/backend/commands/constraint.c

@@ -40,7 +40,7 @@
 Datum
 unique_key_recheck(PG_FUNCTION_ARGS)
 {
-	TriggerData *trigdata = castNode(TriggerData, fcinfo->context);
+	TriggerData *trigdata = (TriggerData *) fcinfo->context;
 	const char *funcname = "unique_key_recheck";
 	ItemPointerData checktid;
 	ItemPointerData tmptid;