doname bounds checking bits

When ready to return, check for overlooked overflow (shouldn't happen)
and panic, or report the first excessively long but not overflown
description to paniclog, similar to xname.

Make ConcUpdate() more robust by not needing bp_eos to be previously
set.  Less efficient but I think that boat has left the barn?  :=}

Fix a comment typo.

src/objnam.c

@@ -89,7 +89,7 @@ struct Jitem {
         ConcUpdate(base);                                               \
     } while (0)
 #define ConcUpdate(base) \
-    base ## _eos = eos(base ## _eos),                                   \
+    base ## _eos = eos(base),                                           \
     /* convert signed ptrdiff_t to unsigned size_t */                   \
     base ## spaceleft = (size_t) (base ## _end - base ## _eos)
 
@@ -573,8 +573,8 @@ xname_flags(
        aside for use by doname() */
     buf = gx.xnamep + PREFIX; /* leave room for "17 -3 " */
     buf_end = gx.xnamep + BUFSZ - 1; /* last byte within the obuf[] */
-    buf[0] = '\0', buf_eos = buf; /* eos(buf) for empty buf[] */
+    buf[0] = '\0';
-    ConcUpdate(buf); /* update buf_eos (redundantly) and bufspaceleft */
+    ConcUpdate(buf); /* set buf_eos and bufspaceleft */
 
     if (Role_if(PM_SAMURAI)) {
         actualn = Japanese_item_name(typ, actualn);
@@ -922,8 +922,8 @@ xname_flags(
        it could make buf[] become shorter */
     if (pluralize) {
         obufp = makeplural(buf);
-        buf[0] = '\0', buf_eos = buf; /* replace the whole string */
+        buf[0] = '\0'; /* replace the whole string */
-        ConcUpdate(buf);
+        ConcUpdate(buf); /* reset buf_eos and bufspaceleft */
         Concat(buf, 0, obufp);
         releaseobuf(obufp);
     }
@@ -1345,7 +1345,7 @@ doname_base(
                    : doffing(obj) ? " (being doffed)"
                      : donning(obj) ? " (being donned)"
                        : " (being worn)");
-            /* we just added a parenthesized pharse, but the right paren
+            /* we just added a parenthesized phrase, but the right paren
                might be absent if the appended string got truncated */
             if (bp_eos[-1] == ')') {
                 /* slippery fingers is an intrinsic condition of the hero
@@ -1631,7 +1631,9 @@ doname_base(
         else
             ConcatF1(bp, 0, " (%u aum)", obj->owt);
 
-        /* ConcatF1(bp) updates bp_eos + bpspaceleft; we're done with them */
+        /* ConcatF1(bp) updates bp_eos and bpspaceleft but we're done
+           with them now; add a fake use so compiler won't complain
+           about a variable assignment that won't be subsequently used */
         nhUse(bp_eos);
         nhUse(bpspaceleft);
     }
@@ -1639,19 +1641,41 @@ doname_base(
     bp = strprepend(bp, prefix);
 
     /*
+     * Last gasp bounds check.
+     *
      * If caller intends this to be for a menu entry, make sure that
      * there is some room to combine with menu selector prefix without
      * exceeding BUFSZ-1.
      *
-     * 4: width of menu entry selector text: "c - " for tty.  For
+     * offsetbp=4: width of menu entry selector text: "c - " for tty.
-     * curses, that wastes a space since it only needs 3: "c) ".
+     * For curses, that wastes a char since it only needs 3: "c) ".
      *
      * Reaching full BUFSZ-1 length can't happen unless both doname
      * (BUFSZ-PREFIX) and strprepend (PREFIX) use up all available
-     * space.
+     * space or one of them overflows without being detected.
      */
-    if (for_menu && strlen(bp) + 4 > BUFSZ - 1)
+    if (strlen(bp) > BUFSZ - 1) {
-        bp[BUFSZ - 1 - 4] = '\0';
+        paniclog("doname", bp);
+        /* ideally this will never happen; if xnamep is any obuf[]
+           other than the last, overflow here would be relatively
+           benign and we could probably keep going */
+        panic("doname: long object description overflow.");
+        /*NOTREACHED*/
+    } else {
+        static int doname_full = 0;
+        int offsetbp = for_menu ? 4 : 0;
+
+        if (strlen(bp) + offsetbp >= BUFSZ - 1) {
+            /* for !offsetbp, we'll only get here if strlen(bp)==BUFSZ-1 */
+            if (!doname_full++) {
+                paniclog("doname", bp);
+                Sprintf(tmpbuf, "long object description%s.",
+                        offsetbp ? " truncated for menu use" : "");
+                paniclog("doname", tmpbuf);
+            }
+            bp[BUFSZ - 1 - offsetbp] = '\0';
+        }
+    }
 
     return bp;
 }