engraving with empty wand

From a bug report:  if you
attempted to engrave with an empty wand while levitating, it wouldn't use
a turn unless you successfully wrested an extra charge out of the wand.
So you could always get such charge in a single elapsed turn of game time
if you didn't care about zapping in any particular direction; extremely
useful for wishing.

     Noticed when checking this:  when you did wrest the extra charge,
the engraving code accessed freed memory for the wand after it had been
used up.

     Lastly, wands producing certain effects always become discovered,
even when you don't yet know what they look like.  (This part of the patch
is trunk-only since it utilizes the routine which fixes similar case for
zapping.)

doc/fixes34.4

@@ -297,6 +297,9 @@ can't throw if poly'd into form which lacks hands
 can't eat an artifact you're unable to touch
 attempting to kick beyond map edge performed an out of array bounds memory
 	access; symptom seen was "show_glyph: bad pos" warning when blind
+attempting to engrave with an empty wand should use a turn even when hero is
+	levitating--trying and failing to wrest a charge takes time
+don't access freed memory after engraving "wrests one last charnge" from wand
 
 
 Platform- and/or Interface-Specific Fixes

include/extern.h

@@ -2578,6 +2578,7 @@ E int FDECL(dowrite, (struct obj *));
 
 /* ### zap.c ### */
 
+E void FDECL(learnwand, (struct obj *));
 E int FDECL(bhitm, (struct monst *,struct obj *));
 E void FDECL(probe_monster, (struct monst *));
 E boolean FDECL(get_obj_location, (struct obj *,xchar *,xchar *,int));

src/engrave.c

@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)engrave.c	3.5	2006/12/06	*/
+/*	SCCS Id: @(#)engrave.c	3.5	2007/01/26	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -618,7 +618,7 @@ doengrave()
 			return 1;
 		    }
 		    zapwand = TRUE;
-		    if (Levitation) ptext = FALSE;
+		    if (!can_reach_floor(TRUE)) ptext = FALSE;
 
 		    switch (otmp->otyp) {
 		    /* DUST wands */
@@ -771,11 +771,12 @@ doengrave()
 		    /* type = MARK wands */
 		    /* type = ENGR_BLOOD wands */
 		    }
-		} else /* end if zappable */
-		    if (!can_reach_floor(TRUE)) {
-			cant_reach_floor(u.ux, u.uy, FALSE, TRUE);
-			return(0);
-		    }
+		} else { /* end if zappable */
+		    /* failing to wrest one last charge takes time */
+		    ptext = FALSE;	/* use "early exit" below, return 1 */
+		    /* cancelled wand turns to dust unless hero can't write */
+		    if (otmp->spe < 0 && can_reach_floor(TRUE)) zapwand = TRUE;
+		}
 		break;
 
 	    case WEAPON_CLASS:
@@ -855,8 +856,8 @@ doengrave()
 
 	/* Identify stylus */
 	if (doknown) {
-	    makeknown(otmp->otyp);
-	    more_experienced(0,10);
+	    learnwand(otmp);
+	    if (objects[otmp->otyp].oc_name_known) more_experienced(0, 10);
 	}
 
 	if (teleengr) {
@@ -884,11 +885,12 @@ doengrave()
      "are not going to get anywhere trying to write in the %s with your dust.",
 		    is_ice(u.ux,u.uy) ? "frost" : "dust");
 	    useup(otmp);
+	    otmp = 0;	/* wand is now gone */
 	    ptext = FALSE;
 	}
 
 	if (!ptext) {		/* Early exit for some implements. */
-	    if (otmp->oclass == WAND_CLASS && !can_reach_floor(TRUE))
+	    if (otmp && otmp->oclass == WAND_CLASS && !can_reach_floor(TRUE))
 		cant_reach_floor(u.ux, u.uy, FALSE, TRUE);
 	    return(1);
 	}

src/zap.c

@@ -19,7 +19,6 @@ extern boolean notonhead;	/* for long worms */
 /* kludge to use mondied instead of killed */
 extern boolean m_using;
 
-STATIC_DCL void FDECL(learnwand, (struct obj *));
 STATIC_DCL void FDECL(polyuse, (struct obj *,int,int));
 STATIC_DCL void FDECL(create_polymon, (struct obj *,int));
 STATIC_DCL boolean FDECL(zap_updown, (struct obj *));
@@ -117,7 +116,7 @@ const char * const flash_types[] = {	/* also used in buzzmu(mcastu.c) */
  */
 
 /* wand discovery gets special handling when hero is blinded */
-STATIC_OVL void
+void
 learnwand(obj)
 struct obj *obj;
 {