Some more attempts to prevent/catch/diagnose floating monster problems. Among

other things:

* If level generation leaves some monsters detached then this will be
  specifically noted.

* If applying _handle_monster_move() to a monster causes that monster to
  become detached it will be noted (those it won't catch *other* monster
  being detached by that monster moving).


git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8009 c06c8d41-db1a-0410-9941-cceddc491573

5 files changed, 86 insertions, 9 deletions

diff --git a/crawl-ref/source/debug.cc b/crawl-ref/source/debug.cc
index 34baa50826..79664df68b 100644
--- a/crawl-ref/source/debug.cc
+++ b/crawl-ref/source/debug.cc
@@ -2253,6 +2253,15 @@ void debug_item_scan( void )
 #endif
 
 #if DEBUG_MONS_SCAN
+static void _announce_level_prob(bool warned)
+{
+    if (!warned && Generating_Level)
+    {
+        mpr("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!", MSGCH_ERROR);
+        mpr("mgrd problem occurred during level generation", MSGCH_ERROR);
+    }
+}
+
 void debug_mons_scan()
 {
     bool warned = false;
@@ -2260,15 +2269,27 @@ void debug_mons_scan()
         for (int x = 0; x < GXM; ++x)
         {
             const int mons = mgrd[x][y];
-            if (mons != NON_MONSTER &&
-                menv[mons].pos() != coord_def(x, y))
+            if (mons == NON_MONSTER)
+                continue;
+            const monsters *m = &menv[mons];
+            if (m->pos() != coord_def(x, y))
             {
-                const monsters *m = &menv[mons];
+                _announce_level_prob(warned);
                 mprf(MSGCH_WARN,
-                     "Bogosity: mgrd at %d,%d points at %s, "
-                     "but monster is at %d,%d",
+                     "Bogosity: mgrd at (%d,%d) points at %s, "
+                     "but monster is at (%d,%d)",
                      x, y, m->name(DESC_PLAIN, true).c_str(),
                      m->pos().x, m->pos().y);
+                if (!m->alive())
+                    mpr("Additionally, it isn't alive.", MSGCH_WARN);
+                warned = true;
+            }
+            else if (!m->alive())
+            {
+                _announce_level_prob(warned);
+                mprf(MSGCH_WARN,
+                     "mgrd at (%d,%d) points at dead monster %s",
+                     x, y, m->name(DESC_PLAIN, true).c_str());
                 warned = true;
             }
         }
@@ -2280,6 +2301,7 @@ void debug_mons_scan()
             continue;
         if (mgrd(m->pos()) != i)
         {
+            _announce_level_prob(warned);
             mprf(MSGCH_WARN, "Floating monster: %s at (%d,%d)",
                  m->name(DESC_PLAIN, true).c_str(), m->pos().x, m->pos().y);
             warned = true;
@@ -2308,6 +2330,10 @@ void debug_mons_scan()
             }
         }
     }
+
+    if (warned && Generating_Level)
+        mpr("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!", MSGCH_ERROR);
+
     // If there are warnings, force the dev to notice. :P
     if (warned)
         more();
diff --git a/crawl-ref/source/dungeon.cc b/crawl-ref/source/dungeon.cc
index 71dd75dd8a..aef1bd79dd 100644
--- a/crawl-ref/source/dungeon.cc
+++ b/crawl-ref/source/dungeon.cc
@@ -313,6 +313,13 @@ bool builder(int level_number, int level_type)
             Level_Unique_Maps.clear();
             Level_Unique_Tags.clear();
             _dgn_map_colour_fixup();
+
+#if DEBUG_MONS_SCAN
+            // If debug_mons_scan() find a problem while Generating_Level is
+            // still true then it will announce that a problem was caused
+            // during level generation.
+            debug_mons_scan();
+#endif
             return (true);
         }
 
diff --git a/crawl-ref/source/mon-util.cc b/crawl-ref/source/mon-util.cc
index 79f0361fb0..91ec861bd9 100644
--- a/crawl-ref/source/mon-util.cc
+++ b/crawl-ref/source/mon-util.cc
@@ -4916,6 +4916,9 @@ bool monsters::has_base_name() const
 
 std::string monsters::name(description_level_type desc, bool force_vis) const
 {
+    if (type == -1)
+        return ("INVALID MONSTER");
+
     const bool possessive =
         (desc == DESC_NOCAP_YOUR || desc == DESC_NOCAP_ITS);
 
@@ -5280,6 +5283,7 @@ int monsters::get_experience_level() const
 
 void monsters::moveto( const coord_def& c )
 {
+    ASSERT(mgrd(c) == NON_MONSTER || c == pos());
     position = c;
 }
 
diff --git a/crawl-ref/source/monplace.cc b/crawl-ref/source/monplace.cc
index 4141730bc7..84a128e5e1 100644
--- a/crawl-ref/source/monplace.cc
+++ b/crawl-ref/source/monplace.cc
@@ -975,6 +975,8 @@ static int _place_monster_aux( const mgen_data &mg,
             return (-1);
     }
 
+    ASSERT(mgrd(fpos) == NON_MONSTER);
+
     // Now, actually create the monster. (Wheeee!)
     menv[id].type         = mg.cls;
     menv[id].base_monster = mg.base_type;
diff --git a/crawl-ref/source/monstuff.cc b/crawl-ref/source/monstuff.cc
index da64131419..83da543cf5 100644
--- a/crawl-ref/source/monstuff.cc
+++ b/crawl-ref/source/monstuff.cc
@@ -1972,11 +1972,9 @@ bool monster_blink(monsters *monster)
 
     mons_clear_trapping_net(monster);
 
-    mgrd(monster->pos()) = NON_MONSTER;
     const coord_def oldplace = monster->pos();
-
-    monster->moveto(near);
-    mgrd(near) = monster_index(monster);
+    if (!monster->move_to_pos(near))
+        return (false);
 
     if (player_monster_visible(monster) && mons_near(monster))
         seen_monster(monster);
@@ -2124,6 +2122,12 @@ bool swap_places(monsters *monster, const coord_def &loc)
     ASSERT(map_bounds(loc));
     ASSERT(_habitat_okay(monster, grd(loc)));
 
+    if (mgrd(loc) != NON_MONSTER)
+    {
+        mpr("Something prevents you from swapping places.");
+        return (false);
+    }
+
     mpr("You swap places.");
 
     mgrd(monster->pos()) = NON_MONSTER;
@@ -4681,6 +4685,14 @@ static bool _siren_movement_effect(const monsters *monster)
 
                 if (swapping)
                 {
+                    if (mgrd(oldpos) != NON_MONSTER)
+                    {
+                        mprf("Something prevents you from swapping places "
+                             "with %s.",
+                             mon->name(DESC_NOCAP_THE).c_str());
+                        return (do_resist);
+                    }
+
                     int swap_mon = mgrd(newpos);
                     // Pick the monster up.
                     mgrd(newpos) = NON_MONSTER;
@@ -6386,12 +6398,38 @@ static void _handle_monster_move(int i, monsters *monster)
     int non_move_energy = std::min(entry->energy_usage.move,
                                    entry->energy_usage.swim);
 
+#if DEBUG_MONS_SCAN
+    bool monster_was_floating = mgrd(monster->pos()) != monster->mindex();
+#endif
+
     while (monster->has_action_energy())
     {
         // The continues & breaks are WRT this.
         if (!monster->alive())
             break;
 
+#if DEBUG_MONS_SCAN
+        if (!monster_was_floating
+            && mgrd(monster->pos()) != monster->mindex())
+        {
+            mprf(MSGCH_ERROR, "Monster %s became detached from mgrd "
+                              "in _handle_monster_move() loop",
+                 monster->name(DESC_PLAIN, true).c_str());
+            mpr("[[[[[[[[[[[[[[[[[[", MSGCH_WARN);
+            debug_mons_scan();
+            mpr("]]]]]]]]]]]]]]]]]]", MSGCH_WARN);
+            monster_was_floating = true;
+        }
+        else if (monster_was_floating
+                 && mgrd(monster->pos()) == monster->mindex())
+        {
+            mprf(MSGCH_DIAGNOSTICS, "Monster %s re-attached itself to mgrd "
+                                    "in _handle_monster_move() loop",
+                 monster->name(DESC_PLAIN, true).c_str());
+            monster_was_floating = false;
+        }
+#endif
+
         if (monster->speed_increment >= old_energy)
         {
 #if DEBUG