- added null pointer validation to any relevant exported function. In most cases null pointers were already being treated as 'do nothing', but there's several places where this can make the code silently fail so in these cases a VM exception will be raised, once the VM's exception handling has been repaired to provide useful diagnostics. (Right now all it does is catch the exception, print a useless message and return to the caller as if nothing has happened.)

src/g_inventory/a_pickups.cpp

@@ -261,7 +261,7 @@ bool AInventory::SpecialDropAction (AActor *dropper)
 DEFINE_ACTION_FUNCTION(AInventory, SpecialDropAction)
 {
 	PARAM_SELF_PROLOGUE(AInventory);
-	PARAM_OBJECT(dropper, AActor);
+	PARAM_OBJECT_NOT_NULL(dropper, AActor);
 	ACTION_RETURN_BOOL(self->SpecialDropAction(dropper));
 }
 
@@ -429,7 +429,7 @@ bool AInventory::HandlePickup (AInventory *item)
 DEFINE_ACTION_FUNCTION(AInventory, HandlePickup)
 {
 	PARAM_SELF_PROLOGUE(AInventory);
-	PARAM_OBJECT(item, AInventory);
+	PARAM_OBJECT_NOT_NULL(item, AInventory);
 	ACTION_RETURN_BOOL(self->HandlePickup(item));
 }
 
@@ -1416,7 +1416,7 @@ bool AInventory::TryPickup (AActor *&toucher)
 DEFINE_ACTION_FUNCTION(AInventory, TryPickup)
 {
 	PARAM_SELF_PROLOGUE(AInventory);
-	PARAM_POINTER(toucher, AActor*);
+	PARAM_POINTER_NOT_NULL(toucher, AActor*);
 	ACTION_RETURN_BOOL(self->TryPickup(*toucher));
 }
 
@@ -1434,7 +1434,7 @@ bool AInventory::TryPickupRestricted (AActor *&toucher)
 DEFINE_ACTION_FUNCTION(AInventory, TryPickupRestricted)
 {
 	PARAM_SELF_PROLOGUE(AInventory);
-	PARAM_POINTER(toucher, AActor*);
+	PARAM_POINTER_NOT_NULL(toucher, AActor*);
 	ACTION_RETURN_BOOL(self->TryPickupRestricted(*toucher));
 }
 
@@ -1613,7 +1613,7 @@ void AInventory::AttachToOwner (AActor *other)
 DEFINE_ACTION_FUNCTION(AInventory, AttachToOwner)
 {
 	PARAM_SELF_PROLOGUE(AInventory);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	self->AttachToOwner(other);
 	return 0;
 }

src/g_shared/a_morph.cpp

@@ -363,7 +363,7 @@ bool P_UndoPlayerMorph (player_t *activator, player_t *player, int unmorphflag,
 DEFINE_ACTION_FUNCTION(_PlayerInfo, UndoPlayerMorph)
 {
 	PARAM_SELF_STRUCT_PROLOGUE(player_t);
-	PARAM_POINTER(player, player_t);
+	PARAM_POINTER_NOT_NULL(player, player_t);
 	PARAM_INT_DEF(unmorphflag);
 	PARAM_BOOL_DEF(force);
 	ACTION_RETURN_BOOL(P_UndoPlayerMorph(self, player, unmorphflag, force));

src/g_shared/a_specialspot.cpp

@@ -265,6 +265,7 @@ DEFINE_ACTION_FUNCTION(DSpotState, GetSpotState)
 
 FSpotList *DSpotState::FindSpotList(PClassActor *type)
 {
+	if (type == nullptr) return nullptr;
 	for(unsigned i = 0; i < SpotLists.Size(); i++)
 	{
 		if (SpotLists[i].Type == type) return &SpotLists[i];
@@ -404,7 +405,7 @@ void ASpecialSpot::Destroy()
 DEFINE_ACTION_FUNCTION(AActor, A_SpawnSingleItem)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_CLASS		(cls, AActor);
+	PARAM_CLASS_NOT_NULL(cls, AActor);
 	PARAM_INT_DEF	(fail_sp) 
 	PARAM_INT_DEF	(fail_co) 
 	PARAM_INT_DEF	(fail_dm) 

src/p_actionfunctions.cpp

@@ -247,7 +247,7 @@ DEFINE_ACTION_FUNCTION(AActor, CheckClass)
 		PARAM_BOOL_DEF	(match_superclass);
 
 		self = COPY_AAPTR(self, pick_pointer);
-		if (self == NULL)
+		if (self == nullptr || checktype == nullptr)
 		{
 			ret->SetInt(false);
 		}

src/p_ceiling.cpp

@@ -461,7 +461,7 @@ bool P_CreateCeiling(sector_t *sec, DCeiling::ECeiling type, line_t *line, int t
 DEFINE_ACTION_FUNCTION(DCeiling, CreateCeiling)
 {
 	PARAM_PROLOGUE;
-	PARAM_POINTER(sec, sector_t);
+	PARAM_POINTER_NOT_NULL(sec, sector_t);
 	PARAM_INT(type);
 	PARAM_POINTER(ln, line_t);
 	PARAM_FLOAT(speed);

src/p_enemy.cpp

@@ -1307,6 +1307,11 @@ bool P_IsVisible(AActor *lookee, AActor *other, INTBOOL allaround, FLookExParams
 	double mindist;
 	DAngle fov;
 
+	if (other == nullptr)
+	{
+		return false;
+	}
+
 	if (params != NULL)
 	{
 		maxdist = params->maxDist;
@@ -3095,7 +3100,7 @@ void A_FaceTarget(AActor *self)
 DEFINE_ACTION_FUNCTION(AActor, A_Face)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(faceto, AActor)
+	PARAM_OBJECT_NOT_NULL(faceto, AActor)
 	PARAM_ANGLE_DEF(max_turn)		
 	PARAM_ANGLE_DEF(max_pitch)		
 	PARAM_ANGLE_DEF(ang_offset)		
@@ -3323,15 +3328,6 @@ AInventory *P_DropItem (AActor *source, PClassActor *type, int dropamount, int c
 	return NULL;
 }
 
-DEFINE_ACTION_FUNCTION(AActor, DoDropItem)
-{
-	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_CLASS(cls, AActor);
-	PARAM_INT(amt);
-	PARAM_INT(chance);
-	ACTION_RETURN_OBJECT(P_DropItem(self, cls, amt, chance));
-}
-
 //============================================================================
 //
 // P_TossItem

src/p_floor.cpp

@@ -495,7 +495,7 @@ bool P_CreateFloor(sector_t *sec, DFloor::EFloor floortype, line_t *line,
 DEFINE_ACTION_FUNCTION(DFloor, CreateFloor)
 {
 	PARAM_PROLOGUE;
-	PARAM_POINTER(sec, sector_t);
+	PARAM_POINTER_NOT_NULL(sec, sector_t);
 	PARAM_INT(floortype);
 	PARAM_POINTER(ln, line_t);
 	PARAM_FLOAT(speed);

src/p_interaction.cpp

@@ -1639,7 +1639,7 @@ void P_PoisonMobj (AActor *target, AActor *inflictor, AActor *source, int damage
 DEFINE_ACTION_FUNCTION(AActor, PoisonMobj)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(inflictor, AActor);
+	PARAM_OBJECT_NOT_NULL(inflictor, AActor);
 	PARAM_OBJECT(source, AActor);
 	PARAM_INT(damage);
 	PARAM_INT(duration);

src/p_map.cpp

@@ -4513,6 +4513,7 @@ DEFINE_ACTION_FUNCTION(AActor, LineAttack)
 	PARAM_POINTER_DEF(victim, FTranslatedLineTarget);
 
 	int acdmg;
+	if (puffType == nullptr) puffType = PClass::FindActor("BulletPuff");	// P_LineAttack does not work without a puff to take info from.
 	auto puff = P_LineAttack(self, angle, distance, pitch, damage, damageType, puffType, flags, victim, &acdmg);
 	if (numret > 0) ret[0].SetPointer(puff, ATAG_OBJECT);
 	if (numret > 1) ret[1].SetInt(acdmg), numret = 2;
@@ -4716,7 +4717,7 @@ DEFINE_ACTION_FUNCTION(_FTranslatedLineTarget, TraceBleed)
 {
 	PARAM_SELF_STRUCT_PROLOGUE(FTranslatedLineTarget);
 	PARAM_INT(damage);
-	PARAM_OBJECT(missile, AActor);
+	PARAM_OBJECT_NOT_NULL(missile, AActor);
 
 	P_TraceBleed(damage, self, missile);
 	return 0;

src/p_maputl.cpp

@@ -1193,7 +1193,7 @@ IMPLEMENT_CLASS(DBlockThingsIterator, false, false);
 DEFINE_ACTION_FUNCTION(DBlockThingsIterator, Create)
 {
 	PARAM_PROLOGUE;
-	PARAM_OBJECT(origin, AActor);
+	PARAM_OBJECT_NOT_NULL(origin, AActor);
 	PARAM_FLOAT_DEF(radius);
 	PARAM_BOOL_DEF(ignore);
 	ACTION_RETURN_OBJECT(new DBlockThingsIterator(origin, radius, ignore));

src/p_mobj.cpp

@@ -751,7 +751,7 @@ void AActor::AddInventory (AInventory *item)
 DEFINE_ACTION_FUNCTION(AActor, AddInventory)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(item, AInventory);
+	PARAM_OBJECT_NOT_NULL(item, AInventory);
 	self->AddInventory(item);
 	return 0;
 }
@@ -819,7 +819,7 @@ bool AActor::GiveInventory(PClassInventory *type, int amount, bool givecheat)
 DEFINE_ACTION_FUNCTION(AActor, Inventory)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(item, AInventory);
+	PARAM_OBJECT_NOT_NULL(item, AInventory);
 	ACTION_RETURN_BOOL(self->UseInventory(item));
 }
 
@@ -854,7 +854,7 @@ void AActor::RemoveInventory(AInventory *item)
 DEFINE_ACTION_FUNCTION(AActor, RemoveInventory)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(item, AInventory);
+	PARAM_OBJECT_NOT_NULL(item, AInventory);
 	self->RemoveInventory(item);
 	return 0;
 }
@@ -1009,7 +1009,7 @@ bool AActor::UseInventory (AInventory *item)
 DEFINE_ACTION_FUNCTION(AActor, UseInventory)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(item, AInventory);
+	PARAM_OBJECT_NOT_NULL(item, AInventory);
 	ACTION_RETURN_BOOL(self->UseInventory(item));
 }
 
@@ -1042,7 +1042,7 @@ AInventory *AActor::DropInventory (AInventory *item)
 DEFINE_ACTION_FUNCTION(AActor, DropInventory)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(item, AInventory);
+	PARAM_OBJECT_NOT_NULL(item, AInventory);
 	ACTION_RETURN_OBJECT(self->DropInventory(item));
 }
 
@@ -1263,7 +1263,7 @@ void AActor::CopyFriendliness (AActor *other, bool changeTarget, bool resetHealt
 DEFINE_ACTION_FUNCTION(AActor, CopyFriendliness)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	PARAM_BOOL_DEF(changetarget);
 	PARAM_BOOL_DEF(resethealth);
 	self->CopyFriendliness(other, changetarget, resethealth);
@@ -1486,7 +1486,7 @@ void AActor::Touch (AActor *toucher)
 DEFINE_ACTION_FUNCTION(AActor, Touch)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(toucher, AActor);
+	PARAM_OBJECT_NOT_NULL(toucher, AActor);
 	self->Touch(toucher);
 	return 0;
 }
@@ -2000,7 +2000,7 @@ bool AActor::CanSeek(AActor *target) const
 DEFINE_ACTION_FUNCTION(AActor, CanSeek)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(target, AActor);
+	PARAM_OBJECT_NOT_NULL(target, AActor);
 	ACTION_RETURN_BOOL(self->CanSeek(target));
 }
 
@@ -4669,7 +4669,7 @@ AActor *AActor::StaticSpawn (PClassActor *type, const DVector3 &pos, replace_t a
 DEFINE_ACTION_FUNCTION(AActor, Spawn)
 {
 	PARAM_PROLOGUE;
-	PARAM_CLASS(type, AActor);
+	PARAM_CLASS_NOT_NULL(type, AActor);
 	PARAM_FLOAT_DEF(x);
 	PARAM_FLOAT_DEF(y);
 	PARAM_FLOAT_DEF(z);
@@ -5656,6 +5656,8 @@ AActor *P_SpawnPuff (AActor *source, PClassActor *pufftype, const DVector3 &pos1
 	AActor *puff;
 	DVector3 pos = pos1;
 
+	if (pufftype == nullptr) return nullptr;
+
 	if (!(flags & PF_NORANDOMZ)) pos.Z += pr_spawnpuff.Random2() / 64.;
 	puff = Spawn(pufftype, pos, ALLOW_REPLACE);
 	if (puff == NULL) return NULL;
@@ -6163,7 +6165,7 @@ foundone:
 DEFINE_ACTION_FUNCTION(AActor, HitWater)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_POINTER(sec, sector_t);
+	PARAM_POINTER_NOT_NULL(sec, sector_t);
 	PARAM_FLOAT(x);
 	PARAM_FLOAT(y);
 	PARAM_FLOAT(z);
@@ -6383,7 +6385,7 @@ void P_PlaySpawnSound(AActor *missile, AActor *spawner)
 DEFINE_ACTION_FUNCTION(AActor, PlaySpawnSound)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(missile, AActor);
+	PARAM_OBJECT_NOT_NULL(missile, AActor);
 	P_PlaySpawnSound(missile, self);
 	return 0;
 }
@@ -6415,47 +6417,11 @@ DEFINE_ACTION_FUNCTION(AActor, GetDefaultSpeed)
 //
 //---------------------------------------------------------------------------
 
-AActor *P_SpawnMissile (AActor *source, AActor *dest, PClassActor *type, AActor *owner)
-{
-	if (source == NULL)
-	{
-		return NULL;
-	}
-	return P_SpawnMissileXYZ (source->PosPlusZ(32 + source->GetBobOffset()), source, dest, type, true, owner);
-}
-
-DEFINE_ACTION_FUNCTION(AActor, SpawnMissile)
-{
-	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(dest, AActor);
-	PARAM_CLASS(type, AActor);
-	PARAM_OBJECT_DEF(owner, AActor);
-	ACTION_RETURN_OBJECT(P_SpawnMissile(self, dest, type, owner));
-}
-
-AActor *P_SpawnMissileZ (AActor *source, double z, AActor *dest, PClassActor *type)
-{
-	if (source == NULL)
-	{
-		return NULL;
-	}
-	return P_SpawnMissileXYZ (source->PosAtZ(z), source, dest, type);
-}
-
-DEFINE_ACTION_FUNCTION(AActor, SpawnMissileZ)
-{
-	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_FLOAT(z);
-	PARAM_OBJECT(dest, AActor);
-	PARAM_CLASS(type, AActor);
-	ACTION_RETURN_OBJECT(P_SpawnMissileZ(self, z, dest, type));
-}
-
 AActor *P_SpawnMissileXYZ (DVector3 pos, AActor *source, AActor *dest, PClassActor *type, bool checkspawn, AActor *owner)
 {
-	if (source == NULL)
+	if (source == nullptr || type == nullptr)
 	{
-		return NULL;
+		return nullptr;
 	}
 
 	if (dest == NULL)
@@ -6530,19 +6496,56 @@ DEFINE_ACTION_FUNCTION(AActor, SpawnMissileXYZ)
 	PARAM_FLOAT(x);
 	PARAM_FLOAT(y);
 	PARAM_FLOAT(z);
-	PARAM_OBJECT(dest, AActor);
+	PARAM_OBJECT_NOT_NULL(dest, AActor);
 	PARAM_CLASS(type, AActor);
 	PARAM_BOOL_DEF(check);
 	PARAM_OBJECT_DEF(owner, AActor);
 	ACTION_RETURN_OBJECT(P_SpawnMissileXYZ(DVector3(x,y,z), self, dest, type, check, owner));
 }
 
+AActor *P_SpawnMissile(AActor *source, AActor *dest, PClassActor *type, AActor *owner)
+{
+	if (source == nullptr)
+	{
+		return nullptr;
+	}
+	return P_SpawnMissileXYZ(source->PosPlusZ(32 + source->GetBobOffset()), source, dest, type, true, owner);
+}
+
+DEFINE_ACTION_FUNCTION(AActor, SpawnMissile)
+{
+	PARAM_SELF_PROLOGUE(AActor);
+	PARAM_OBJECT_NOT_NULL(dest, AActor);
+	PARAM_CLASS(type, AActor);
+	PARAM_OBJECT_DEF(owner, AActor);
+	ACTION_RETURN_OBJECT(P_SpawnMissile(self, dest, type, owner));
+}
+
+AActor *P_SpawnMissileZ(AActor *source, double z, AActor *dest, PClassActor *type)
+{
+	if (source == nullptr)
+	{
+		return nullptr;
+	}
+	return P_SpawnMissileXYZ(source->PosAtZ(z), source, dest, type);
+}
+
+DEFINE_ACTION_FUNCTION(AActor, SpawnMissileZ)
+{
+	PARAM_SELF_PROLOGUE(AActor);
+	PARAM_FLOAT(z);
+	PARAM_OBJECT_NOT_NULL(dest, AActor);
+	PARAM_CLASS(type, AActor);
+	ACTION_RETURN_OBJECT(P_SpawnMissileZ(self, z, dest, type));
+}
+
+
 
 AActor *P_OldSpawnMissile(AActor *source, AActor *owner, AActor *dest, PClassActor *type)
 {
-	if (source == NULL)
+	if (source == nullptr || type == nullptr)
 	{
-		return NULL;
+		return nullptr;
 	}
 	AActor *th = Spawn (type, source->PosPlusZ(32.), ALLOW_REPLACE);
 
@@ -6568,7 +6571,7 @@ AActor *P_OldSpawnMissile(AActor *source, AActor *owner, AActor *dest, PClassAct
 DEFINE_ACTION_FUNCTION(AActor, OldSpawnMissile)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(dest, AActor);
+	PARAM_OBJECT_NOT_NULL(dest, AActor);
 	PARAM_CLASS(type, AActor);
 	PARAM_OBJECT_DEF(owner, AActor);
 	ACTION_RETURN_OBJECT(P_OldSpawnMissile(self, owner, dest, type));
@@ -6586,7 +6589,7 @@ DEFINE_ACTION_FUNCTION(AActor, OldSpawnMissile)
 
 AActor *P_SpawnMissileAngle (AActor *source, PClassActor *type, DAngle angle, double vz)
 {
-	if (source == NULL)
+	if (source == nullptr || type == nullptr)
 	{
 		return NULL;
 	}
@@ -6595,14 +6598,18 @@ AActor *P_SpawnMissileAngle (AActor *source, PClassActor *type, DAngle angle, do
 
 AActor *P_SpawnMissileAngleZ (AActor *source, double z, PClassActor *type, DAngle angle, double vz)
 {
+	if (type == nullptr)
+	{
+		return nullptr;
+	}
 	return P_SpawnMissileAngleZSpeed (source, z, type, angle, vz, GetDefaultSpeed (type));
 }
 
 AActor *P_SpawnMissileZAimed (AActor *source, double z, AActor *dest, PClassActor *type)
 {
-	if (source == NULL)
+	if (source == nullptr || type == nullptr)
 	{
-		return NULL;
+		return nullptr;
 	}
 	DAngle an;
 	double dist;
@@ -6626,7 +6633,7 @@ DEFINE_ACTION_FUNCTION(AActor, SpawnMissileZAimed)
 {
 	PARAM_SELF_PROLOGUE(AActor);
 	PARAM_FLOAT(z);
-	PARAM_OBJECT(dest, AActor);
+	PARAM_OBJECT_NOT_NULL(dest, AActor);
 	PARAM_CLASS(type, AActor);
 	ACTION_RETURN_OBJECT(P_SpawnMissileZAimed(self, z, dest, type));
 }
@@ -6643,9 +6650,9 @@ DEFINE_ACTION_FUNCTION(AActor, SpawnMissileZAimed)
 AActor *P_SpawnMissileAngleZSpeed (AActor *source, double z,
 	PClassActor *type, DAngle angle, double vz, double speed, AActor *owner, bool checkspawn)
 {
-	if (source == NULL)
+	if (source == nullptr || type == nullptr)
 	{
-		return NULL;
+		return nullptr;
 	}
 	AActor *mo;
 
@@ -6689,9 +6696,9 @@ AActor *P_SpawnSubMissile(AActor *source, PClassActor *type, AActor *target)
 {
 	AActor *other = Spawn(type, source->Pos(), ALLOW_REPLACE);
 
-	if (other == NULL)
+	if (source == nullptr || type == nullptr)
 	{
-		return NULL;
+		return nullptr;
 	}
 
 	other->target = target;
@@ -6723,7 +6730,7 @@ DEFINE_ACTION_FUNCTION(AActor, SpawnSubMissile)
 {
 	PARAM_SELF_PROLOGUE(AActor);
 	PARAM_CLASS(cls, AActor);
-	PARAM_OBJECT(target, AActor);
+	PARAM_OBJECT_NOT_NULL(target, AActor);
 	ACTION_RETURN_OBJECT(P_SpawnSubMissile(self, cls, target));
 }
 /*
@@ -6753,6 +6760,11 @@ AActor *P_SpawnPlayerMissile (AActor *source, double x, double y, double z,
 							  PClassActor *type, DAngle angle, FTranslatedLineTarget *pLineTarget, AActor **pMissileActor,
 							  bool nofreeaim, bool noautoaim, int aimflags)
 {
+	if (source == nullptr || type == nullptr)
+	{
+		return nullptr;
+	}
+
 	static const double angdiff[3] = { -5.625, 5.625, 0 };
 	DAngle an = angle;
 	DAngle pitch;
@@ -6760,10 +6772,6 @@ AActor *P_SpawnPlayerMissile (AActor *source, double x, double y, double z,
 	AActor *defaultobject = GetDefaultByType(type);
 	DAngle vrange = nofreeaim ? 35. : 0.;
 
-	if (source == NULL)
-	{
-		return NULL;
-	}
 	if (!pLineTarget) pLineTarget = &scratch;
 	if (source->player && source->player->ReadyWeapon && ((source->player->ReadyWeapon->WeaponFlags & WIF_NOAUTOAIM) || noautoaim))
 	{
@@ -6910,7 +6918,7 @@ bool AActor::IsTeammate (AActor *other)
 DEFINE_ACTION_FUNCTION(AActor, isTeammate)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	ACTION_RETURN_BOOL(self->IsTeammate(other));
 }
 
@@ -6982,7 +6990,7 @@ bool AActor::IsFriend (AActor *other)
 DEFINE_ACTION_FUNCTION(AActor, isFriend)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	ACTION_RETURN_BOOL(self->IsFriend(other));
 }
 
@@ -7019,7 +7027,7 @@ bool AActor::IsHostile (AActor *other)
 DEFINE_ACTION_FUNCTION(AActor, isHostile)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	ACTION_RETURN_BOOL(self->IsHostile(other));
 }
 
@@ -7058,7 +7066,7 @@ int AActor::DoSpecialDamage (AActor *target, int damage, FName damagetype)
 DEFINE_ACTION_FUNCTION(AActor, DoSpecialDamage)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(target, AActor);
+	PARAM_OBJECT_NOT_NULL(target, AActor);
 	PARAM_INT(damage);
 	PARAM_NAME(damagetype);
 	ACTION_RETURN_INT(self->DoSpecialDamage(target, damage, damagetype));
@@ -7580,14 +7588,14 @@ DEFINE_ACTION_FUNCTION(AActor, absangle)	// should this be global?
 DEFINE_ACTION_FUNCTION(AActor, Distance2D)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	ACTION_RETURN_FLOAT(self->Distance2D(other));
 }
 
 DEFINE_ACTION_FUNCTION(AActor, Distance3D)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(other, AActor);
+	PARAM_OBJECT_NOT_NULL(other, AActor);
 	ACTION_RETURN_FLOAT(self->Distance3D(other));
 }
 
@@ -7620,7 +7628,7 @@ DEFINE_ACTION_FUNCTION(AActor, GetDefaultByType)
 {
 	PARAM_PROLOGUE;
 	PARAM_CLASS(cls, AActor);
-	ACTION_RETURN_OBJECT(GetDefaultByType(cls));
+	ACTION_RETURN_OBJECT(cls == nullptr? nullptr : GetDefaultByType(cls));
 }
 
 DEFINE_ACTION_FUNCTION(AActor, GetBobOffset)
@@ -7692,7 +7700,7 @@ DEFINE_ACTION_FUNCTION(AActor, Thrust)
 DEFINE_ACTION_FUNCTION(AActor, AngleTo)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(targ, AActor);
+	PARAM_OBJECT_NOT_NULL(targ, AActor);
 	PARAM_BOOL_DEF(absolute);
 	ACTION_RETURN_FLOAT(self->AngleTo(targ, absolute).Degrees);
 }
@@ -7717,7 +7725,7 @@ DEFINE_ACTION_FUNCTION(AActor, RotateVector)
 DEFINE_ACTION_FUNCTION(AActor, DistanceBySpeed)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(targ, AActor);
+	PARAM_OBJECT_NOT_NULL(targ, AActor);
 	PARAM_FLOAT(speed);
 	ACTION_RETURN_FLOAT(self->DistanceBySpeed(targ, speed));
 }
@@ -7745,14 +7753,14 @@ DEFINE_ACTION_FUNCTION(AActor, Vec2Angle)
 DEFINE_ACTION_FUNCTION(AActor, Vec3To)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(t, AActor)
+	PARAM_OBJECT_NOT_NULL(t, AActor)
 	ACTION_RETURN_VEC3(self->Vec3To(t));
 }
 
 DEFINE_ACTION_FUNCTION(AActor, Vec2To)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(t, AActor)
+	PARAM_OBJECT_NOT_NULL(t, AActor)
 		ACTION_RETURN_VEC2(self->Vec2To(t));
 }
 

src/p_pspr.cpp

@@ -1605,7 +1605,8 @@ void player_t::DestroyPSprites()
 
 void P_SetSafeFlash(AWeapon *weapon, player_t *player, FState *flashstate, int index)
 {
-
+	if (flashstate != nullptr)
+	{
 		PClassActor *cls = weapon->GetClass();
 		while (cls != RUNTIME_CLASS(AWeapon))
 		{
@@ -1638,13 +1639,14 @@ void P_SetSafeFlash(AWeapon *weapon, player_t *player, FState *flashstate, int i
 		{ // Invalid state. With no index offset, it should at least be valid.
 			index = 0;
 		}
+	}
 	P_SetPsprite(player, PSP_FLASH, flashstate + index, true);
 }
 
 DEFINE_ACTION_FUNCTION(_PlayerInfo, SetSafeFlash)
 {
 	PARAM_SELF_STRUCT_PROLOGUE(player_t);
-	PARAM_OBJECT(weapon, AWeapon);
+	PARAM_OBJECT_NOT_NULL(weapon, AWeapon);
 	PARAM_POINTER(state, FState);
 	PARAM_INT(index);
 	P_SetSafeFlash(weapon, self, state, index);

src/p_sight.cpp

@@ -908,7 +908,7 @@ done:
 DEFINE_ACTION_FUNCTION(AActor, CheckSight)
 {
 	PARAM_SELF_PROLOGUE(AActor);
-	PARAM_OBJECT(target, AActor);
+	PARAM_OBJECT_NOT_NULL(target, AActor);
 	PARAM_INT_DEF(flags);
 	ACTION_RETURN_BOOL(P_CheckSight(self, target, flags));
 }

src/p_states.cpp

@@ -1083,11 +1083,12 @@ DEFINE_ACTION_FUNCTION(FState, DistanceTo)
 {
 	PARAM_SELF_STRUCT_PROLOGUE(FState);
 	PARAM_POINTER(other, FState);
-
+	int retv = INT_MIN;
+	if (other != nullptr)
+	{
 		// Safely calculate the distance between two states.
 		auto o1 = FState::StaticFindStateOwner(self);
-	int retv;
+		if (other >= o1->OwnedStates && other < o1->OwnedStates + o1->NumOwnedStates) retv = int(other - self);
-	if (other < o1->OwnedStates || other >= o1->OwnedStates + o1->NumOwnedStates) retv =  INT_MIN;
+	}
-	else retv = int(other - self);
 	ACTION_RETURN_INT(retv);
 }

src/scripting/codegeneration/codegen.cpp

@@ -9697,7 +9697,7 @@ int BuiltinClassCast(VMValue *param, TArray<VMValue> &defaultparam, int numparam
 	PARAM_PROLOGUE;
 	PARAM_CLASS(from, DObject);
 	PARAM_CLASS(to, DObject);
-	ACTION_RETURN_OBJECT(from->IsDescendantOf(to) ? from : nullptr);
+	ACTION_RETURN_OBJECT(from && to && from->IsDescendantOf(to) ? from : nullptr);
 }
 
 ExpEmit FxClassPtrCast::Emit(VMFunctionBuilder *build)

src/scripting/vm/vm.h

@@ -951,6 +951,9 @@ void VMDisasm(FILE *out, const VMOP *code, int codesize, const VMScriptFunction
 
 // Use these to collect the parameters in a native function.
 // variable name <x> at position <p>
+void NullParam(const char *varname);
+
+#define PARAM_NULLCHECK(ptr, var) (ptr == nullptr? NullParam(#var), ptr : ptr)
 
 // For required parameters.
 #define PARAM_INT_AT(p,x)			assert((p) < numparam); assert(param[p].Type == REGT_INT); int x = param[p].i;
@@ -966,6 +969,9 @@ void VMDisasm(FILE *out, const VMOP *code, int codesize, const VMScriptFunction
 #define PARAM_POINTER_AT(p,x,type)	assert((p) < numparam); assert(param[p].Type == REGT_POINTER); type *x = (type *)param[p].a;
 #define PARAM_OBJECT_AT(p,x,type)	assert((p) < numparam); assert(param[p].Type == REGT_POINTER && (param[p].atag == ATAG_OBJECT || param[p].a == NULL)); type *x = (type *)param[p].a; assert(x == NULL || x->IsKindOf(RUNTIME_CLASS(type)));
 #define PARAM_CLASS_AT(p,x,base)	assert((p) < numparam); assert(param[p].Type == REGT_POINTER && (param[p].atag == ATAG_OBJECT || param[p].a == NULL)); base::MetaClass *x = (base::MetaClass *)param[p].a; assert(x == NULL || x->IsDescendantOf(RUNTIME_CLASS(base)));
+#define PARAM_POINTER_NOT_NULL_AT(p,x,type)	assert((p) < numparam); assert(param[p].Type == REGT_POINTER); type *x = (type *)PARAM_NULLCHECK(param[p].a, #x);
+#define PARAM_OBJECT_NOT_NULL_AT(p,x,type)	assert((p) < numparam); assert(param[p].Type == REGT_POINTER && (param[p].atag == ATAG_OBJECT || param[p].a == NULL)); type *x = (type *)PARAM_NULLCHECK(param[p].a, #x); assert(x == NULL || x->IsKindOf(RUNTIME_CLASS(type)));
+#define PARAM_CLASS_NOT_NULL_AT(p,x,base)	assert((p) < numparam); assert(param[p].Type == REGT_POINTER && (param[p].atag == ATAG_OBJECT || param[p].a == NULL)); base::MetaClass *x = (base::MetaClass *)PARAM_NULLCHECK(param[p].a, #x); assert(x == NULL || x->IsDescendantOf(RUNTIME_CLASS(base)));
 
 #define PARAM_EXISTS(p)					((p) < numparam)
 #define ASSERTINT(p)					assert((p).Type == REGT_INT)
@@ -988,6 +994,7 @@ void VMDisasm(FILE *out, const VMOP *code, int codesize, const VMScriptFunction
 #define PARAM_POINTER_DEF_AT(p,x,t)		t *x; if (PARAM_EXISTS(p)) { ASSERTPOINTER(param[p]); x = (t*)param[p].a; } else { ASSERTPOINTER(defaultparam[p]); x = (t*)defaultparam[p].a; }
 #define PARAM_OBJECT_DEF_AT(p,x,t)		t *x; if (PARAM_EXISTS(p)) { ASSERTOBJECT(param[p]); x = (t*)param[p].a; } else { ASSERTOBJECT(defaultparam[p]); x = (t*)defaultparam[p].a; }
 #define PARAM_CLASS_DEF_AT(p,x,t)		t::MetaClass *x; if (PARAM_EXISTS(p)) { ASSERTOBJECT(param[p]); x = (t::MetaClass*)param[p].a; } else { ASSERTOBJECT(defaultparam[p]); x = (t::MetaClass*)defaultparam[p].a; }
+#define PARAM_CLASS_DEF_NOT_NULL_AT(p,x,t)		t::MetaClass *x; if (PARAM_EXISTS(p)) { ASSERTOBJECT(param[p]); x = (t::MetaClass*)PARAM_NULLCHECK(param[p].a, #x); } else { ASSERTOBJECT(defaultparam[p]); x = (t::MetaClass*)PARAM_NULLCHECK(defaultparam[p].a, #x); }
 
 // The above, but with an automatically increasing position index.
 #define PARAM_PROLOGUE				int paramnum = -1;
@@ -1005,6 +1012,9 @@ void VMDisasm(FILE *out, const VMOP *code, int codesize, const VMScriptFunction
 #define PARAM_POINTER(x,type)		++paramnum; PARAM_POINTER_AT(paramnum,x,type)
 #define PARAM_OBJECT(x,type)		++paramnum; PARAM_OBJECT_AT(paramnum,x,type)
 #define PARAM_CLASS(x,base)			++paramnum; PARAM_CLASS_AT(paramnum,x,base)
+#define PARAM_POINTER_NOT_NULL(x,type)		++paramnum; PARAM_POINTER_NOT_NULL_AT(paramnum,x,type)
+#define PARAM_OBJECT_NOT_NULL(x,type)		++paramnum; PARAM_OBJECT_NOT_NULL_AT(paramnum,x,type)
+#define PARAM_CLASS_NOT_NULL(x,base)		++paramnum; PARAM_CLASS_NOT_NULL_AT(paramnum,x,base)
 
 #define PARAM_INT_DEF(x)			++paramnum; PARAM_INT_DEF_AT(paramnum,x)
 #define PARAM_BOOL_DEF(x)			++paramnum; PARAM_BOOL_DEF_AT(paramnum,x)
@@ -1019,6 +1029,7 @@ void VMDisasm(FILE *out, const VMOP *code, int codesize, const VMScriptFunction
 #define PARAM_POINTER_DEF(x,type)	++paramnum; PARAM_POINTER_DEF_AT(paramnum,x,type)
 #define PARAM_OBJECT_DEF(x,type)	++paramnum; PARAM_OBJECT_DEF_AT(paramnum,x,type)
 #define PARAM_CLASS_DEF(x,base)		++paramnum; PARAM_CLASS_DEF_AT(paramnum,x,base)
+#define PARAM_CLASS_DEF_NOT_NULL(x,base)	++paramnum; PARAM_CLASS_DEF_NOT_NULL_AT(paramnum,x,base)
 
 typedef int(*actionf_p)(VMValue *param, TArray<VMValue> &defaultparam, int numparam, VMReturn *ret, int numret);/*(VM_ARGS)*/
 

src/scripting/vm/vmexec.cpp

@@ -228,3 +228,7 @@ void VMFillParams(VMValue *params, VMFrame *callee, int numparam)
 		}
 	}
 }
+
+void NullParam(const char *varname)
+{
+}