Fixed: Fatal error during game change

An attempt was made to dereference a dangling pointer to the objlink
blockmap once a map had been played and the game subsequently changed.

The objlink blockmaps are allocated with a Zone purge level >= PU_MAP
thus pointers to them will be invalid after a game change.

doomsday/engine/portable/include/p_objlink.h

@@ -39,6 +39,17 @@ typedef enum {
 
 #define VALID_OBJTYPE(val) ((val) >= OT_MOBJ && (val) < NUM_OBJ_TYPES)
 
+/**
+ * To be called during a game change/on shutdown to destroy the objlink
+ * blockmap. This is necessary because the blockmaps are allocated from
+ * the Zone with a >= PU_MAP purge level and access to them is handled
+ * with global pointers.
+ *
+ * \todo Encapsulate allocation of and access to the objlink blockmaps
+ *       within de::Map
+ */
+void R_DestroyObjlinkBlockmap(void);
+
 /**
  * Construct the objlink blockmap for the current map.
  */

doomsday/engine/portable/src/dd_main.c

@@ -1073,7 +1073,7 @@ boolean DD_ChangeGame2(Game* game, boolean allowReload)
         Con_SaveDefaults();
 
         LO_Clear();
-        //R_DestroyObjlinks();
+        R_DestroyObjlinkBlockmap();
         R_ClearAnimGroups();
 
         P_PtcShutdown();
@@ -1514,7 +1514,7 @@ int DD_Main(void)
 
     // Try to locate all required data files for all registered games.
     Con_InitProgress(200);
-    Con_Busy(BUSYF_STARTUP | BUSYF_PROGRESS_BAR | BUSYF_PROGRESS_BAR | (verbose? BUSYF_CONSOLE_OUTPUT : 0),
+    Con_Busy(BUSYF_STARTUP | BUSYF_PROGRESS_BAR | (verbose? BUSYF_CONSOLE_OUTPUT : 0),
              "Locating game resources...", DD_LocateAllGameResourcesWorker, 0);
 
     // Unless we reenter busy-mode due to automatic game selection, we won't be

doomsday/engine/portable/src/p_objlink.c

@@ -249,6 +249,23 @@ void R_InitObjlinkBlockmapForMap(void)
     ssecContacts = Z_Calloc(sizeof *ssecContacts * numSSectors, PU_MAPSTATIC, 0);
 }
 
+void R_DestroyObjlinkBlockmap(void)
+{
+    int i;
+    for(i = 0; i < NUM_OBJ_TYPES; ++i)
+    {
+        objlinkblockmap_t* obm = chooseObjlinkBlockmap((objtype_t)i);
+        if(!obm->gridmap) continue;
+        Gridmap_Delete(obm->gridmap);
+        obm->gridmap = NULL;
+    }
+    if(ssecContacts)
+    {
+        Z_Free(ssecContacts);
+        ssecContacts = NULL;
+    }
+}
+
 int clearObjlinkBlock(void* obj, void* paramaters)
 {
     objlinkblock_t* block = (objlinkblock_t*)obj;