Fixes for degenerate RNG

Assume a degenerate RNG that always returns the same number.
With these fixes, the game starts and is almost playable.
There are still some places that will go into infinite loop, eg.
the mines level generation.

src/mklev.c

@@ -812,6 +812,7 @@ makelevel()
 
     /* for each room: put things inside */
     for (croom = g.rooms; croom->hx > 0; croom++) {
+        int trycnt = 0;
         if (croom->rtype != OROOM)
             continue;
 
@@ -833,7 +834,7 @@ makelevel()
         x = 8 - (level_difficulty() / 6);
         if (x <= 1)
             x = 2;
-        while (!rn2(x))
+        while (!rn2(x) && (++trycnt < 1000))
             mktrap(0, 0, croom, (coord *) 0);
         if (!rn2(3))
             (void) mkgold(0L, somex(croom), somey(croom));
@@ -1121,6 +1122,7 @@ coord *mp;
     if (g.nroom == 0) {
         mazexy(mp); /* already verifies location */
     } else {
+        int cnt = 0;
         /* not perfect - there may be only one stairway */
         if (g.nroom > 2) {
             int tryct = 0;
@@ -1135,9 +1137,9 @@ coord *mp;
         do {
             if (!somexy(croom, mp))
                 impossible("Can't place branch!");
-        } while (occupied(mp->x, mp->y)
+        } while ((occupied(mp->x, mp->y)
                  || (levl[mp->x][mp->y].typ != CORR
-                     && levl[mp->x][mp->y].typ != ROOM));
+                     && levl[mp->x][mp->y].typ != ROOM)) && (++cnt < 1000));
     }
     return croom;
 }

src/mkmaze.c

@@ -1035,6 +1035,7 @@ const char *s;
         mazexy(&mm);
         mkstairs(mm.x, mm.y, 0, (struct mkroom *) 0); /* down */
     } else { /* choose "vibrating square" location */
+        int trycnt = 0;
 #define x_maze_min 2
 #define y_maze_min 2
 /*
@@ -1064,6 +1065,8 @@ const char *s;
             y = rn1(y_range, y_maze_min + INVPOS_Y_MARGIN + 1);
             /* we don't want it to be too near the stairs, nor
                to be on a spot that's already in use (wall|trap) */
+            if (++trycnt > 1000)
+                break;
         } while (x == xupstair || y == yupstair /*(direct line)*/
                  || abs(x - xupstair) == abs(y - yupstair)
                  || distmin(x, y, xupstair, yupstair) <= INVPOS_DISTANCE

src/role.c

@@ -2028,9 +2028,19 @@ role_init()
 
     /* Fix up the god names */
     if (flags.pantheon == -1) {             /* new game */
+        int trycnt = 0;
         flags.pantheon = flags.initrole;    /* use own gods */
-        while (!roles[flags.pantheon].lgod) /* unless they're missing */
+        /* unless they're missing */
+        while (!roles[flags.pantheon].lgod && ++trycnt < 100)
             flags.pantheon = randrole(FALSE);
+        if (!roles[flags.pantheon].lgod) {
+            int i;
+            for (i = 0; i < SIZE(roles) - 1; i++)
+                if (roles[i].lgod) {
+                    flags.pantheon = i;
+                    break;
+                }
+        }
     }
     if (!g.urole.lgod) {
         g.urole.lgod = roles[flags.pantheon].lgod;

src/u_init.c

@@ -979,6 +979,7 @@ register struct trobj *trop;
         if (otyp != UNDEF_TYP) {
             obj = mksobj(otyp, TRUE, FALSE);
         } else { /* UNDEF_TYP */
+            int trycnt = 0;
             /*
              * For random objects, do not create certain overly powerful
              * items: wand of wishing, ring of levitation, or the
@@ -1019,6 +1020,8 @@ register struct trobj *trop;
                 dealloc_obj(obj);
                 obj = mkobj(trop->trclass, FALSE);
                 otyp = obj->otyp;
+                if (++trycnt > 1000)
+                    break;
             }
 
             /* Don't start with +0 or negative rings */