- added runtime checks for the state usage flags.

src/p_actionfunctions.cpp

@@ -128,6 +128,13 @@ bool ACustomInventory::CallStateChain (AActor *actor, FState *state)
 
 	while (state != NULL)
 	{
+		if (!(state->UseFlags & SUF_ITEM))
+		{
+			auto so = FState::StaticFindStateOwner(state);
+			Printf("State %s.%d not flagged for use in CustomInventory state chains.\n", so->TypeName.GetChars(), int(state - so->OwnedStates));
+			return false;
+		}
+
 		this->state = state;
 		nextstate = NULL;	// assume no jump
 

src/p_mobj.cpp

@@ -626,6 +626,14 @@ bool AActor::SetState (FState *newstate, bool nofunction)
 		{
 			prevsprite = -1;
 		}
+		if (!(newstate->UseFlags & SUF_ACTOR))
+		{
+			auto so = FState::StaticFindStateOwner(newstate);
+			Printf("State %s.%d in %s not flagged for use as an actor sprite\n", so->TypeName.GetChars(), int(newstate - so->OwnedStates), GetClass()->TypeName.GetChars());
+			state = nullptr;
+			Destroy();
+			return false;
+		}
 		state = newstate;
 		tics = GetTics(newstate);
 		renderflags = (renderflags & ~RF_FULLBRIGHT) | ActorRenderFlags::FromInt (newstate->GetFullbright());

src/p_pspr.cpp

@@ -296,6 +296,16 @@ void DPSprite::SetState(FState *newstate, bool pending)
 			Destroy();
 			return;
 		}
+
+		if (!(newstate->UseFlags & (SUF_OVERLAY|SUF_WEAPON)))	// Weapon and overlay are mostly the same, the main difference is that weapon states restrict the self pointer to class Actor.
+		{
+			auto so = FState::StaticFindStateOwner(newstate);
+			Printf("State %s.%d not flagged for use in overlays or weapons\n", so->TypeName.GetChars(), int(newstate - so->OwnedStates));
+			State = nullptr;
+			Destroy();
+			return;
+		}
+
 		State = newstate;
 
 		if (newstate->sprite != SPR_FIXED)

src/scripting/zscript/zcc_compile.cpp

@@ -2437,6 +2437,7 @@ void ZCCCompiler::CompileStates()
 					auto sl = static_cast<ZCC_StateLine *>(st);
 					FState state;
 					memset(&state, 0, sizeof(state));
+					state.UseFlags = flags;
 					if (sl->Sprite->Len() != 4)
 					{
 						Error(sl, "Sprite name must be exactly 4 characters. Found '%s'", sl->Sprite->GetChars());