fix seg fault caused by garbage collection of `ClosureData`s

If the `ClosureData`s are freed on `lua_closed`, the references to the State they may have could become invalid. This was fixed by storing a StatePtr inside LuaRef's instead of a reference

src/lref.rs

@@ -1,6 +1,6 @@
-use std::sync::Arc;
+use std::{marker::PhantomData, sync::Arc};
 
-use crate::{Error, PushToLuaStack, Result, State};
+use crate::{Error, PushToLuaStack, Result, State, StatePtr};
 
 use mlua_sys as lua;
 
@@ -11,15 +11,16 @@ use mlua_sys as lua;
 /// the inner Arc detects a single strong count.
 #[derive(Clone)]
 pub struct LuaRef<'a> {
-    lref: Arc<i32>,
+    pub(crate) lref: Arc<i32>,
-    pub(crate) state: &'a State,
+    pub(crate) state: StatePtr,
+    _marker: PhantomData<&'a State>,
 }
 
 impl<'a> Drop for LuaRef<'a> {
     fn drop(&mut self) {
         unsafe {
             if Arc::strong_count(&self.lref) == 1 {
-                let s = self.state.state_ptr();
+                let s = self.state.lua.as_ptr();
                 lua::luaL_unref(s, lua::LUA_REGISTRYINDEX, *self.lref);
             }
         }
@@ -27,10 +28,19 @@ impl<'a> Drop for LuaRef<'a> {
 }
 
 impl<'a> LuaRef<'a> {
-    pub fn new(lua_ref: i32, state: &'a State) -> Self {
+    pub(crate) fn new(lua_ref: i32, state: &'a State) -> Self {
         Self {
             lref: Arc::new(lua_ref),
-            state,
+            state: state.ptr.clone(),
+            _marker: PhantomData
+        }
+    }
+
+    pub(crate) fn from_arc(lua_ref: Arc<i32>, state: &'a State) -> Self {
+        Self {
+            lref: lua_ref,
+            state: state.ptr.clone(),
+            _marker: PhantomData
         }
     }
 

src/state.rs

@@ -101,12 +101,12 @@ struct ClosureData<'a> {
 }
 
 //#[derive(Default)]
-pub struct ExtraSpace<'a> {
+pub struct ExtraSpace {
-    pub userdata_metatables: HashMap<TypeId, LuaRef<'a>>,
+    pub userdata_metatables: HashMap<TypeId, Arc<i32>>,
-    pub state_ptr: StatePtr
+    pub state_ptr: StatePtr,
 }
 
-impl<'a> ExtraSpace<'a> {
+impl ExtraSpace {
     pub fn new(state: &State) -> Self {
         Self {
             userdata_metatables: Default::default(),
@@ -117,11 +117,11 @@ impl<'a> ExtraSpace<'a> {
 
 #[derive(Clone)]
 pub struct StatePtr {
-    lua: Arc<NonNull<lua::lua_State>>,
+    pub lua: Arc<NonNull<lua::lua_State>>,
 }
 
 pub struct State {
-    ptr: StatePtr,
+    pub(crate) ptr: StatePtr,
 }
 
 impl Default for State {
@@ -133,28 +133,31 @@ impl Default for State {
 impl Drop for State {
     fn drop(&mut self) {
         unsafe { 
-            println!("State count: {}", Arc::strong_count(&self.ptr.lua));
-            if Arc::strong_count(&self.ptr.lua) == 2 { // this owned arc, and the one in extra
             let extra = self.get_extra_space_ptr();
             
             {
                 // clear the refs to anything in lua before we close it and
                 // attempt to drop extra after
+
+                let s = self.state_ptr();
                 let extra = &mut *extra;
+                for (_, lref) in extra.userdata_metatables.drain() {
+                    lua::luaL_unref(s, lua::LUA_REGISTRYINDEX, *lref);
+                }
+
                 extra.userdata_metatables.clear();
             }
 
             lua::lua_close(self.state_ptr());
             extra.drop_in_place();
 
-                // must be dealloced since it wasn't memory created from lua (i.e. userdata)
+            // must be dealloced since it wasn't memory created from lua
             alloc::dealloc(extra.cast(), Layout::new::<ExtraSpace>());
         }
     }
 }
-}
 
-unsafe fn extra_space<'a>(state: *mut lua::lua_State) -> *mut ExtraSpace<'a> {
+unsafe fn extra_space(state: *mut lua::lua_State) -> *mut ExtraSpace {
     let extra = lua::lua_getextraspace(state)
         .cast::<*mut ExtraSpace>();
     *extra
@@ -432,16 +435,15 @@ impl State {
             }
         };
 
+        unsafe {
+            let s = self.state_ptr();
+            let _g = StackGuard::new(self);
+            self.ensure_stack(4)?;
+            
             let data = ClosureData {
                 wrapper_fn: Box::new(wrapper_fn),
             };
 
-        let s = self.state_ptr();
-        
-        unsafe {
-            let _g = StackGuard::new(self);
-            self.ensure_stack(3)?;
-
             let ptr = lua::lua_newuserdata(s, mem::size_of::<ClosureData>());
             let ptr = ptr.cast();
             ptr::write(ptr, data);
@@ -480,8 +482,11 @@ impl State {
                 let mt = self.create_userdata_metatable::<T>()?;
                 mt.push_to_lua_stack(self)?;
             } else {
-                let mt = udmts.get(&TypeId::of::<T>()).unwrap();
+                let mt = self.get_userdata_metatable::<T>();
                 mt.push_to_lua_stack(self)?;
+
+                /* let mt = udmts.get(&TypeId::of::<T>()).unwrap();
+                mt.push_to_lua_stack(self)?; */
             }
 
             lua::lua_setmetatable(s, -2);
@@ -494,7 +499,7 @@ impl State {
         let extra = self.get_extra_space();
         let mt = extra.userdata_metatables.get(&TypeId::of::<T>());
 
-        mt.map(|r| Table::with_ref(self, r.clone(), true).unwrap())
+        mt.map(|r| Table::with_ref(self, LuaRef::from_arc(r.clone(), self), true).unwrap())
     }
 
     pub(crate) fn create_userdata_metatable<'a, T: Userdata + 'static>(&'a self) -> Result<Table<'a>> {
@@ -577,7 +582,7 @@ impl State {
         }
 
         let extra = self.get_extra_space();
-        extra.userdata_metatables.insert(TypeId::of::<T>(), mt.lref.clone());
+        extra.userdata_metatables.insert(TypeId::of::<T>(), mt.lref.lref.clone());
 
         Ok(mt)
     }

src/table_iter.rs

@@ -1,6 +1,6 @@
-use std::marker::PhantomData;
+use std::{marker::PhantomData, mem};
 
-use crate::{FromLua, FromLuaStack, LuaRef, PushToLuaStack, StackGuard, Value};
+use crate::{FromLua, FromLuaStack, LuaRef, PushToLuaStack, StackGuard, State, Value};
 
 use mlua_sys as lua;
 
@@ -25,15 +25,16 @@ impl<'a, T: FromLua<'a>> Iterator for TableIter<'a, T> {
 
     fn next(&mut self) -> Option<Self::Item> {
         unsafe {
-            let state = self.lref.state;
+            let state: &State = mem::transmute(&self.lref.state.lua);
+
             let s = state.state_ptr();
 
             if let Err(e) = state.ensure_stack(1) {
                 return Some(Err(e));
             }
-            let _g = StackGuard::new(state);
+            let _g = StackGuard::new(&state);
 
-            if let Err(e) = self.lref.push_to_lua_stack(state) {
+            if let Err(e) = self.lref.push_to_lua_stack(&state) {
                 return Some(Err(e));
             }
 

src/table_pairs.rs

@@ -1,6 +1,6 @@
-use std::marker::PhantomData;
+use std::{marker::PhantomData, mem};
 
-use crate::{AsLua, FromLua, FromLuaStack, LuaRef, PushToLuaStack, StackGuard, Value};
+use crate::{AsLua, FromLua, FromLuaStack, LuaRef, PushToLuaStack, StackGuard, State, Value};
 
 use mlua_sys as lua;
 
@@ -20,7 +20,7 @@ impl<'a, K: FromLua<'a>, V: FromLua<'a>> TablePairs<'a, K, V> {
     }
 
     unsafe fn get_item(&mut self) -> crate::Result<Option<(K, V)>> {
-        let state = self.lref.state;
+        let state: &State = mem::transmute(&self.lref.state.lua);
         let s = state.state_ptr();
 
         let _g = StackGuard::new(state);