DO mkinvokearea() TODO

When performing the invocation, you would get
|The floor shakes violently under you!
|The walls around you begin to bend and crumble!
even if all the nearby walls had been dug away or the level's maze was
made of lava pools instead of walls.  Suppress the second message when
it isn't applicable.

src/mklev.c

@@ -17,6 +17,9 @@ static boolean find_okay_roompos(struct mkroom *, coord *) NONNULLARG12;
 static void mksink(struct mkroom *);
 static void mkaltar(struct mkroom *);
 static void mkgrave(struct mkroom *);
+static void mkinvpos(coordxy, coordxy, int);
+static int mkinvk_check_wall(coordxy x, coordxy y);
+static void mk_knox_portal(coordxy, coordxy);
 static void makevtele(void);
 static void fill_ordinary_room(struct mkroom *, boolean) NONNULLARG1;
 static void makelevel(void);
@@ -38,8 +41,6 @@ static void do_room_or_subroom(struct mkroom *,
 static void makerooms(void);
 static boolean door_into_nonjoined(coordxy, coordxy);
 static boolean finddpos(coord *, coordxy, coordxy, coordxy, coordxy);
-static void mkinvpos(coordxy, coordxy, int);
-static void mk_knox_portal(coordxy, coordxy);
 
 #define create_vault() create_room(-1, -1, 2, 2, -1, -1, VAULT, TRUE)
 #define init_vault() gv.vault_x = -1
@@ -2171,19 +2172,50 @@ mkgrave(struct mkroom *croom)
 void
 mkinvokearea(void)
 {
-    int dist;
+    int dist, wallct;
-    coordxy xmin = gi.inv_pos.x, xmax = gi.inv_pos.x,
+    coordxy xmin, xmax, ymin, ymax;
-          ymin = gi.inv_pos.y, ymax = gi.inv_pos.y;
     register coordxy i;
 
     /* slightly odd if levitating, but not wrong */
     pline_The("floor shakes violently under you!");
-    /*
+    /* decide whether to issue the crumbling walls message */
-     * TODO:
+    {
-     *  Suppress this message if player has dug out all the walls
+        xmin = xmax = gi.inv_pos.x;
-     *  that would otherwise be affected.
+        ymin = ymax = gi.inv_pos.y;
-     */
+        wallct = mkinvk_check_wall(xmin, ymin);
-    pline_The("walls around you begin to bend and crumble!");
+        /* this replicates the somewhat convoluted loop below, working
+           out from the stair position, except for stopping early when
+           walls are found */
+        for (dist = 1; !wallct && dist < 7; ++dist) {
+            xmin--, xmax++;
+            /* top and bottom */
+            if (dist != 3) { /* the area is wider that it is high */
+                ymin--, ymax++;
+                for (i = xmin + 1; i < xmax; i++) {
+                    if (mkinvk_check_wall(i, ymin))
+                        ++wallct; /* we could break after finding first wall
+                                   * but it isn't a significant optimization
+                                   * for code which only executes once */
+                    if (mkinvk_check_wall(i, ymax))
+                        ++wallct;
+                }
+            }
+            /* left and right */
+            if (!wallct) { /* skip y loop if x loop found any walls */
+                for (i = ymin; i <= ymax; i++) {
+                    if (mkinvk_check_wall(xmin, i))
+                        ++wallct;
+                    if (mkinvk_check_wall(xmax, i))
+                        ++wallct;
+                }
+            }
+        }
+        /* message won't appear if the maze 'walls' on this level are lava
+           or if all the walls within range have been dug away; when it does
+           appear, it will describe iron bars as "walls" (which is ok) */
+        if (wallct)
+            pline_The("walls around you begin to bend and crumble!");
+    }
     display_nhwindow(WIN_MESSAGE, TRUE);
 
     /* any trap hero is stuck in will be going away now */
@@ -2192,6 +2224,9 @@ mkinvokearea(void)
             buried_ball_to_punishment();
         reset_utrap(FALSE);
     }
+
+    xmin = xmax = gi.inv_pos.x; /* reset after the check for walls */
+    ymin = ymax = gi.inv_pos.y;
     mkinvpos(xmin, ymin, 0); /* middle, before placing stairs */
 
     for (dist = 1; dist < 7; dist++) {
@@ -2314,6 +2349,21 @@ mkinvpos(coordxy x, coordxy y, int dist)
     newsym(x, y);
 }
 
+/* reduces clutter in mkinvokearea() while avoiding potential static analyzer
+   confusion about using isok(x,y) to control access to levl[x][y] */
+static int
+mkinvk_check_wall(coordxy x, coordxy y)
+{
+    unsigned ltyp;
+
+    if (!isok(x, y))
+        return 0;
+    assert(x > 0 && x < COLNO);
+    assert(y >= 0 && y < ROWNO);
+    ltyp = levl[x][y].typ;
+    return (IS_STWALL(ltyp) || ltyp == IRONBARS) ? 1 : 0;
+}
+
 /*
  * The portal to Ludios is special.  The entrance can only occur within a
  * vault in the main dungeon at a depth greater than 10.  The Ludios branch