1 files changed, 26 insertions, 29 deletions

diff --git a/src/p_mobj.c b/src/p_mobj.c
index 29dafdec..bb72166d 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -922,6 +922,28 @@ void P_CheckMissileSpawn (mobj_t* th)
 	P_ExplodeMissile (th);
 }
 
+// Certain functions assume that a mobj_t pointer is non-NULL,
+// causing a crash in some situations where it is NULL.  Vanilla
+// Doom did not crash because of the lack of proper memory 
+// protection. This function substitutes NULL pointers for
+// pointers to a dummy mobj, to avoid a crash.
+
+mobj_t *P_SubstNullMobj(mobj_t *mobj)
+{
+    if (mobj == NULL)
+    {
+        static mobj_t dummy_mobj;
+
+        dummy_mobj.x = 0;
+        dummy_mobj.y = 0;
+        dummy_mobj.z = 0;
+        dummy_mobj.flags = 0;
+
+        mobj = &dummy_mobj;
+    }
+
+    return mobj;
+}
 
 //
 // P_SpawnMissile
@@ -935,31 +957,6 @@ P_SpawnMissile
     mobj_t*	th;
     angle_t	an;
     int		dist;
-    fixed_t     dest_x, dest_y, dest_z, dest_flags;
-
-    // fraggle: This prevents against *crashes* when dest == NULL.
-    // For example, when loading a game saved when a mancubus was 
-    // in the middle of firing, mancubus->target == NULL.  SpawnMissile
-    // then gets called with dest == NULL.
-    //
-    // However, this is not the *correct* behavior.  At the moment,
-    // the missile is aimed at 0,0,0.  In reality, monsters seem to aim
-    // somewhere else.
-
-    if (dest)
-    {
-        dest_x = dest->x;
-        dest_y = dest->y;
-        dest_z = dest->z;
-        dest_flags = dest->flags;
-    }
-    else
-    {
-        dest_x = 0;
-        dest_y = 0;
-        dest_z = 0;
-        dest_flags = 0;
-    }
 
     th = P_SpawnMobj (source->x,
 		      source->y,
@@ -969,10 +966,10 @@ P_SpawnMissile
 	S_StartSound (th, th->info->seesound);
 
     th->target = source;	// where it came from
-    an = R_PointToAngle2 (source->x, source->y, dest_x, dest_y);	
+    an = R_PointToAngle2 (source->x, source->y, dest->x, dest->y);
 
     // fuzzy player
-    if (dest_flags & MF_SHADOW)
+    if (dest->flags & MF_SHADOW)
 	an += (P_Random()-P_Random())<<20;	
 
     th->angle = an;
@@ -980,13 +977,13 @@ P_SpawnMissile
     th->momx = FixedMul (th->info->speed, finecosine[an]);
     th->momy = FixedMul (th->info->speed, finesine[an]);
 	
-    dist = P_AproxDistance (dest_x - source->x, dest_y - source->y);
+    dist = P_AproxDistance (dest->x - source->x, dest->y - source->y);
     dist = dist / th->info->speed;
 
     if (dist < 1)
 	dist = 1;
 
-    th->momz = (dest_z - source->z) / dist;
+    th->momz = (dest->z - source->z) / dist;
     P_CheckMissileSpawn (th);
 	
     return th;