v0.11.3

This functionality is similar to `coroutine.yield` and `coroutine.resume` without C restrictions.

CHANGELOG.md

@@ -1,3 +1,12 @@
+## v0.11.3 (Aug 30, 2025)
+
+- Add `Lua::yield_with` to use as `coroutine.yield` functional replacement in async functions for any Lua
+- Do not try to yield at non-yielable points in Luau interrupt (#632)
+- Add `Buffer::cursor` method (Luau)
+- Add `Lua::create_buffer_with_capacity` method (Luau)
+- Make Lua reference values cheap to clone (only increments ref count)
+- Fix panic on large (>67M entries) table creation
+
 ## v0.11.2 (Aug 10, 2025)
 
 - Faster stack push for `Variadic<T>`

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua"
-version = "0.11.2" # remember to update mlua_derive
+version = "0.11.3" # remember to update mlua_derive
 authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@kyju.org>"]
 rust-version = "1.79.0"
 edition = "2021"

benches/benchmark.rs

@@ -128,6 +128,22 @@ fn table_traversal_sequence(c: &mut Criterion) {
     });
 }
 
+fn table_ref_clone(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    let t = lua.create_table().unwrap();
+
+    c.bench_function("table [ref clone]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                let _t2 = t.clone();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
 fn function_create(c: &mut Criterion) {
     let lua = Lua::new();
 
@@ -350,6 +366,39 @@ fn userdata_call_method(c: &mut Criterion) {
     });
 }
 
+// A userdata method call that goes through an implicit `__index` function
+fn userdata_call_method_complex(c: &mut Criterion) {
+    struct UserData(u64);
+    impl LuaUserData for UserData {
+        fn register(registry: &mut LuaUserDataRegistry<Self>) {
+            registry.add_field_method_get("val", |_, this| Ok(this.0));
+            registry.add_method_mut("inc_by", |_, this, by: u64| {
+                this.0 += by;
+                Ok(this.0)
+            });
+        }
+    }
+
+    let lua = Lua::new();
+    let ud = lua.create_userdata(UserData(0)).unwrap();
+    let inc_by = lua
+        .load("function(ud, s) return ud:inc_by(s) end")
+        .eval::<LuaFunction>()
+        .unwrap();
+
+    c.bench_function("userdata [call method complex]", |b| {
+        b.iter_batched(
+            || {
+                collect_gc_twice(&lua);
+            },
+            |_| {
+                inc_by.call::<()>((&ud, 1)).unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
 fn userdata_async_call_method(c: &mut Criterion) {
     struct UserData(i64);
     impl LuaUserData for UserData {
@@ -399,6 +448,7 @@ criterion_group! {
         table_traversal_pairs,
         table_traversal_for_each,
         table_traversal_sequence,
+        table_ref_clone,
 
         function_create,
         function_call_sum,
@@ -413,6 +463,7 @@ criterion_group! {
         userdata_create,
         userdata_call_index,
         userdata_call_method,
+        userdata_call_method_complex,
         userdata_async_call_method,
 }
 

mlua-sys/Cargo.toml

@@ -41,7 +41,7 @@ cfg-if = "1.0"
 pkg-config = "0.3.17"
 lua-src = { version = ">= 548.1.0, < 548.2.0", optional = true }
 luajit-src = { version = ">= 210.6.0, < 210.7.0", optional = true }
-luau0-src = { version = "0.15.4", optional = true }
+luau0-src = { version = "0.15.6", optional = true }
 
 [lints.rust]
 unexpected_cfgs = { level = "allow", check-cfg = ['cfg(raw_dylib)'] }

mlua-sys/src/luau/lua.rs

@@ -235,6 +235,7 @@ unsafe extern "C-unwind" {
     ) -> c_int;
     pub fn lua_call(L: *mut lua_State, nargs: c_int, nresults: c_int);
     pub fn lua_pcall(L: *mut lua_State, nargs: c_int, nresults: c_int, errfunc: c_int) -> c_int;
+    pub fn lua_cpcall(L: *mut lua_State, f: lua_CFunction, ud: *mut c_void) -> c_int;
 
     //
     // Coroutine functions

src/buffer.rs

@@ -1,3 +1,5 @@
+use std::io;
+
 #[cfg(feature = "serde")]
 use serde::ser::{Serialize, Serializer};
 
@@ -50,13 +52,18 @@ impl Buffer {
     #[track_caller]
     pub fn write_bytes(&self, offset: usize, bytes: &[u8]) {
         let lua = self.0.lua.lock();
-        let data = unsafe {
-            let (buf, size) = self.as_raw_parts(&lua);
-            std::slice::from_raw_parts_mut(buf, size)
-        };
+        let data = self.as_slice_mut(&lua);
         data[offset..offset + bytes.len()].copy_from_slice(bytes);
     }
 
+    /// Returns an adaptor implementing [`io::Read`], [`io::Write`] and [`io::Seek`] over the
+    /// buffer.
+    ///
+    /// Buffer operations are infallible, none of the read/write functions will return a Err.
+    pub fn cursor(self) -> impl io::Read + io::Write + io::Seek {
+        BufferCursor(self, 0)
+    }
+
     pub(crate) fn as_slice(&self, lua: &RawLua) -> &[u8] {
         unsafe {
             let (buf, size) = self.as_raw_parts(lua);
@@ -64,6 +71,14 @@ impl Buffer {
         }
     }
 
+    #[allow(clippy::mut_from_ref)]
+    fn as_slice_mut(&self, lua: &RawLua) -> &mut [u8] {
+        unsafe {
+            let (buf, size) = self.as_raw_parts(lua);
+            std::slice::from_raw_parts_mut(buf, size)
+        }
+    }
+
     #[cfg(feature = "luau")]
     unsafe fn as_raw_parts(&self, lua: &RawLua) -> (*mut u8, usize) {
         let mut size = 0usize;
@@ -78,6 +93,66 @@ impl Buffer {
     }
 }
 
+struct BufferCursor(Buffer, usize);
+
+impl io::Read for BufferCursor {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let lua = self.0 .0.lua.lock();
+        let data = self.0.as_slice(&lua);
+        if self.1 == data.len() {
+            return Ok(0);
+        }
+        let len = buf.len().min(data.len() - self.1);
+        buf[..len].copy_from_slice(&data[self.1..self.1 + len]);
+        self.1 += len;
+        Ok(len)
+    }
+}
+
+impl io::Write for BufferCursor {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let lua = self.0 .0.lua.lock();
+        let data = self.0.as_slice_mut(&lua);
+        if self.1 == data.len() {
+            return Ok(0);
+        }
+        let len = buf.len().min(data.len() - self.1);
+        data[self.1..self.1 + len].copy_from_slice(&buf[..len]);
+        self.1 += len;
+        Ok(len)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl io::Seek for BufferCursor {
+    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
+        let lua = self.0 .0.lua.lock();
+        let data = self.0.as_slice(&lua);
+        let new_offset = match pos {
+            io::SeekFrom::Start(offset) => offset as i64,
+            io::SeekFrom::End(offset) => data.len() as i64 + offset,
+            io::SeekFrom::Current(offset) => self.1 as i64 + offset,
+        };
+        if new_offset < 0 {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "invalid seek to a negative position",
+            ));
+        }
+        if new_offset as usize > data.len() {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "invalid seek to a position beyond the end of the buffer",
+            ));
+        }
+        self.1 = new_offset as usize;
+        Ok(self.1 as u64)
+    }
+}
+
 #[cfg(feature = "serde")]
 impl Serialize for Buffer {
     fn serialize<S: Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {

src/state.rs

@@ -37,6 +37,7 @@ use crate::{buffer::Buffer, chunk::Compiler};
 use {
     crate::types::LightUserData,
     std::future::{self, Future},
+    std::task::Poll,
 };
 
 #[cfg(feature = "serde")]
@@ -631,13 +632,13 @@ impl Lua {
     ///
     /// Any Luau code is guaranteed to call this handler "eventually"
     /// (in practice this can happen at any function call or at any loop iteration).
+    /// This is similar to `Lua::set_hook` but in more simplified form.
     ///
     /// The provided interrupt function can error, and this error will be propagated through
     /// the Luau code that was executing at the time the interrupt was triggered.
     /// Also this can be used to implement continuous execution limits by instructing Luau VM to
-    /// yield by returning [`VmState::Yield`].
-    ///
-    /// This is similar to `Lua::set_hook` but in more simplified form.
+    /// yield by returning [`VmState::Yield`]. The yield will happen only at yieldable points
+    /// of execution (not across metamethod/C-call boundaries).
     ///
     /// # Example
     ///
@@ -695,7 +696,10 @@ impl Lua {
             match result {
                 VmState::Continue => {}
                 VmState::Yield => {
-                    ffi::lua_yield(state, 0);
+                    // We can yield only at yieldable points, otherwise ignore and continue
+                    if ffi::lua_isyieldable(state) != 0 {
+                        ffi::lua_yield(state, 0);
+                    }
                 }
             }
         }
@@ -1150,7 +1154,7 @@ impl Lua {
         }
     }
 
-    /// Create and return an interned Lua string.
+    /// Creates and returns an interned Lua string.
     ///
     /// Lua strings can be arbitrary `[u8]` data including embedded nulls, so in addition to `&str`
     /// and `&String`, you can also pass plain `&[u8]` here.
@@ -1159,27 +1163,32 @@ impl Lua {
         unsafe { self.lock().create_string(s) }
     }
 
-    /// Create and return a Luau [buffer] object from a byte slice of data.
+    /// Creates and returns a Luau [buffer] object from a byte slice of data.
     ///
     /// [buffer]: https://luau.org/library#buffer-library
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-    pub fn create_buffer(&self, buf: impl AsRef<[u8]>) -> Result<Buffer> {
+    pub fn create_buffer(&self, data: impl AsRef<[u8]>) -> Result<Buffer> {
         let lua = self.lock();
-        let state = lua.state();
+        let data = data.as_ref();
         unsafe {
-            if lua.unlikely_memory_error() {
-                crate::util::push_buffer(state, buf.as_ref(), false)?;
-                return Ok(Buffer(lua.pop_ref()));
-            }
-
-            let _sg = StackGuard::new(state);
-            check_stack(state, 3)?;
-            crate::util::push_buffer(state, buf.as_ref(), true)?;
-            Ok(Buffer(lua.pop_ref()))
+            let (ptr, buffer) = lua.create_buffer_with_capacity(data.len())?;
+            ptr.copy_from_nonoverlapping(data.as_ptr(), data.len());
+            Ok(buffer)
         }
     }
 
+    /// Creates and returns a Luau [buffer] object with the specified size.
+    ///
+    /// Size limit is 1GB. All bytes will be initialized to zero.
+    ///
+    /// [buffer]: https://luau.org/library#buffer-library
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn create_buffer_with_capacity(&self, size: usize) -> Result<Buffer> {
+        unsafe { Ok(self.lock().create_buffer_with_capacity(size)?.1) }
+    }
+
     /// Creates and returns a new empty table.
     #[inline]
     pub fn create_table(&self) -> Result<Table> {
@@ -2071,6 +2080,101 @@ impl Lua {
         LightUserData(&ASYNC_POLL_TERMINATE as *const u8 as *mut std::os::raw::c_void)
     }
 
+    #[cfg(feature = "async")]
+    #[inline(always)]
+    pub(crate) fn poll_yield() -> LightUserData {
+        static ASYNC_POLL_YIELD: u8 = 0;
+        LightUserData(&ASYNC_POLL_YIELD as *const u8 as *mut std::os::raw::c_void)
+    }
+
+    /// Suspends the current async function, returning the provided arguments to caller.
+    ///
+    /// This function is similar to [`coroutine.yield`] but allow yeilding Rust functions
+    /// and passing values to the caller.
+    /// Please note that you cannot cross [`Thread`] boundaries (e.g. calling `yield_with` on one
+    /// thread and resuming on another).
+    ///
+    /// # Examples
+    ///
+    /// Async iterator:
+    ///
+    /// ```
+    /// # use mlua::{Lua, Result};
+    ///
+    /// async fn generator(lua: Lua, _: ()) -> Result<()> {
+    ///     for i in 0..10 {
+    ///         lua.yield_with::<()>(i).await?;
+    ///     }
+    ///     Ok(())
+    /// }
+    ///
+    /// fn main() -> Result<()> {
+    ///     let lua = Lua::new();
+    ///     lua.globals().set("generator", lua.create_async_function(generator)?)?;
+    ///
+    ///     lua.load(r#"
+    ///        local n = 0
+    ///        for i in coroutine.wrap(generator) do
+    ///            n = n + i
+    ///        end
+    ///        assert(n == 45)
+    ///     "#)
+    ///     .exec()
+    /// }
+    /// ```
+    ///
+    /// Exchange values on yield:
+    ///
+    /// ```
+    /// # use mlua::{Lua, Result, Value};
+    ///
+    /// async fn pingpong(lua: Lua, mut val: i32) -> Result<()> {
+    ///     loop {
+    ///         val = lua.yield_with::<i32>(val).await? + 1;
+    ///     }
+    ///     Ok(())
+    /// }
+    ///
+    /// # fn main() -> Result<()> {
+    /// let lua = Lua::new();
+    ///
+    /// let co = lua.create_thread(lua.create_async_function(pingpong)?)?;
+    /// assert_eq!(co.resume::<i32>(1)?, 1);
+    /// assert_eq!(co.resume::<i32>(2)?, 3);
+    /// assert_eq!(co.resume::<i32>(3)?, 4);
+    ///
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`coroutine.yield`]: https://www.lua.org/manual/5.4/manual.html#pdf-coroutine.yield
+    #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+    pub async fn yield_with<R: FromLuaMulti>(&self, args: impl IntoLuaMulti) -> Result<R> {
+        let mut args = Some(args.into_lua_multi(self)?);
+        future::poll_fn(move |_cx| match args.take() {
+            Some(args) => unsafe {
+                let lua = self.lock();
+                lua.push(Self::poll_yield())?; // yield marker
+                if args.len() <= 1 {
+                    lua.push(args.front())?;
+                } else {
+                    lua.push(lua.create_sequence_from(&args)?)?;
+                }
+                lua.push(args.len())?;
+                Poll::Pending
+            },
+            None => unsafe {
+                let lua = self.lock();
+                let state = lua.state();
+                let _sg = StackGuard::with_top(state, 0);
+                let nvals = ffi::lua_gettop(state);
+                Poll::Ready(R::from_stack_multi(nvals, &lua))
+            },
+        })
+        .await
+    }
+
     /// Returns a weak reference to the Lua instance.
     ///
     /// This is useful for creating a reference to the Lua instance that does not prevent it from

src/state/extra.rs

@@ -64,7 +64,7 @@ pub(crate) struct ExtraData {
     pub(super) wrapped_failure_top: usize,
     // Pool of `Thread`s (coroutines) for async execution
     #[cfg(feature = "async")]
-    pub(super) thread_pool: Vec<c_int>,
+    pub(super) thread_pool: Vec<crate::types::ValueRefIndex>,
 
     // Address of `WrappedFailure` metatable
     pub(super) wrapped_failure_mt_ptr: *const c_void,

src/state/raw.rs

@@ -523,6 +523,20 @@ impl RawLua {
         Ok(String(self.pop_ref()))
     }
 
+    #[cfg(feature = "luau")]
+    pub(crate) unsafe fn create_buffer_with_capacity(&self, size: usize) -> Result<(*mut u8, crate::Buffer)> {
+        let state = self.state();
+        if self.unlikely_memory_error() {
+            let ptr = crate::util::push_buffer(state, size, false)?;
+            return Ok((ptr, crate::Buffer(self.pop_ref())));
+        }
+
+        let _sg = StackGuard::new(state);
+        check_stack(state, 3)?;
+        let ptr = crate::util::push_buffer(state, size, true)?;
+        Ok((ptr, crate::Buffer(self.pop_ref())))
+    }
+
     /// See [`Lua::create_table_with_capacity`]
     pub(crate) unsafe fn create_table_with_capacity(&self, narr: usize, nrec: usize) -> Result<Table> {
         let state = self.state();
@@ -624,7 +638,7 @@ impl RawLua {
     #[cfg(feature = "async")]
     pub(crate) unsafe fn create_recycled_thread(&self, func: &Function) -> Result<Thread> {
         if let Some(index) = (*self.extra.get()).thread_pool.pop() {
-            let thread_state = ffi::lua_tothread(self.ref_thread(), index);
+            let thread_state = ffi::lua_tothread(self.ref_thread(), *index.0);
             ffi::lua_xpush(self.ref_thread(), thread_state, func.0.index);
 
             #[cfg(feature = "luau")]
@@ -645,8 +659,9 @@ impl RawLua {
     pub(crate) unsafe fn recycle_thread(&self, thread: &mut Thread) {
         let extra = &mut *self.extra.get();
         if extra.thread_pool.len() < extra.thread_pool.capacity() {
-            extra.thread_pool.push(thread.0.index);
-            thread.0.drop = false; // Prevent thread from being garbage collected
+            if let Some(index) = thread.0.index_count.take() {
+                extra.thread_pool.push(index);
+            }
         }
     }
 
@@ -827,13 +842,6 @@ impl RawLua {
         ValueRef::new(self, index)
     }
 
-    #[inline]
-    pub(crate) unsafe fn clone_ref(&self, vref: &ValueRef) -> ValueRef {
-        ffi::lua_pushvalue(self.ref_thread(), vref.index);
-        let index = (*self.extra.get()).ref_stack_pop();
-        ValueRef::new(self, index)
-    }
-
     pub(crate) unsafe fn drop_ref(&self, vref: &ValueRef) {
         let ref_thread = self.ref_thread();
         mlua_debug_assert!(
@@ -1270,6 +1278,13 @@ impl RawLua {
                 let mut ctx = Context::from_waker(rawlua.waker());
                 match fut.as_mut().map(|fut| fut.as_mut().poll(&mut ctx)) {
                     Some(Poll::Pending) => {
+                        let fut_nvals = ffi::lua_gettop(state);
+                        if fut_nvals >= 3 && ffi::lua_tolightuserdata(state, -3) == Lua::poll_yield().0 {
+                            // We have some values to yield
+                            ffi::lua_pushnil(state);
+                            ffi::lua_replace(state, -4);
+                            return Ok(3);
+                        }
                         ffi::lua_pushnil(state);
                         ffi::lua_pushlightuserdata(state, Lua::poll_pending().0);
                         Ok(2)
@@ -1340,6 +1355,7 @@ impl RawLua {
             local poll = get_poll(...)
             local nres, res, res2 = poll()
             while true do
+                -- Poll::Ready branch, `nres` is the number of results
                 if nres ~= nil then
                     if nres == 0 then
                         return
@@ -1355,10 +1371,20 @@ impl RawLua {
                         return unpack(res, nres)
                     end
                 end
-                -- `res` is a "pending" value
-                -- `yield` can return a signal to drop the future that we should propagate
-                -- to the poller
-                nres, res, res2 = poll(yield(res))
+
+                -- Poll::Pending branch
+                if res2 == nil then
+                    -- `res` is a "pending" value
+                    -- `yield` can return a signal to drop the future that we should propagate
+                    -- to the poller
+                    nres, res, res2 = poll(yield(res))
+                elseif res2 == 0 then
+                    nres, res, res2 = poll(yield())
+                elseif res2 == 1 then
+                    nres, res, res2 = poll(yield(res))
+                else
+                    nres, res, res2 = poll(yield(unpack(res, res2)))
+                end
             end
             "#,
         )
@@ -1370,14 +1396,14 @@ impl RawLua {
 
     #[cfg(feature = "async")]
     #[inline]
-    pub(crate) unsafe fn waker(&self) -> &Waker {
-        (*self.extra.get()).waker.as_ref()
+    pub(crate) fn waker(&self) -> &Waker {
+        unsafe { (*self.extra.get()).waker.as_ref() }
     }
 
     #[cfg(feature = "async")]
     #[inline]
-    pub(crate) unsafe fn set_waker(&self, waker: NonNull<Waker>) -> NonNull<Waker> {
-        mem::replace(&mut (*self.extra.get()).waker, waker)
+    pub(crate) fn set_waker(&self, waker: NonNull<Waker>) -> NonNull<Waker> {
+        unsafe { mem::replace(&mut (*self.extra.get()).waker, waker) }
     }
 }
 

src/table.rs

@@ -884,7 +884,7 @@ impl ObjectLike for Table {
         R: FromLuaMulti,
     {
         // Convert table to a function and call via pcall that respects the `__call` metamethod.
-        Function(self.0.copy()).call(args)
+        Function(self.0.clone()).call(args)
     }
 
     #[cfg(feature = "async")]
@@ -893,7 +893,7 @@ impl ObjectLike for Table {
     where
         R: FromLuaMulti,
     {
-        Function(self.0.copy()).call_async(args)
+        Function(self.0.clone()).call_async(args)
     }
 
     #[inline]
@@ -941,7 +941,7 @@ impl ObjectLike for Table {
 
     #[inline]
     fn to_string(&self) -> Result<StdString> {
-        Value::Table(Table(self.0.copy())).to_string()
+        Value::Table(Table(self.0.clone())).to_string()
     }
 }
 

src/thread.rs

@@ -156,7 +156,6 @@ impl Thread {
         let thread_state = self.state();
         unsafe {
             let _sg = StackGuard::new(state);
-            let _thread_sg = StackGuard::with_top(thread_state, 0);
 
             let nargs = args.push_into_stack_multi(&lua)?;
             if nargs > 0 {
@@ -165,6 +164,7 @@ impl Thread {
                 pushed_nargs += nargs;
             }
 
+            let _thread_sg = StackGuard::with_top(thread_state, 0);
             let (_, nresults) = self.resume_inner(&lua, pushed_nargs)?;
             check_stack(state, nresults + 1)?;
             ffi::lua_xmove(thread_state, state, nresults);
@@ -192,12 +192,12 @@ impl Thread {
         let thread_state = self.state();
         unsafe {
             let _sg = StackGuard::new(state);
-            let _thread_sg = StackGuard::with_top(thread_state, 0);
 
             check_stack(state, 1)?;
             error.push_into_stack(&lua)?;
             ffi::lua_xmove(state, thread_state, 1);
 
+            let _thread_sg = StackGuard::with_top(thread_state, 0);
             let (_, nresults) = self.resume_inner(&lua, ffi::LUA_RESUMEERROR)?;
             check_stack(state, nresults + 1)?;
             ffi::lua_xmove(thread_state, state, nresults);
@@ -604,7 +604,7 @@ impl<R: FromLuaMulti> Future for AsyncThread<R> {
 
             if status.is_yielded() {
                 if !(nresults == 1 && is_poll_pending(thread_state)) {
-                    // Ignore value returned via yield()
+                    // Ignore values returned via yield()
                     cx.waker().wake_by_ref();
                 }
                 return Poll::Pending;
@@ -635,7 +635,7 @@ struct WakerGuard<'lua, 'a> {
 impl<'lua, 'a> WakerGuard<'lua, 'a> {
     #[inline]
     pub fn new(lua: &'lua RawLua, waker: &'a Waker) -> Result<WakerGuard<'lua, 'a>> {
-        let prev = unsafe { lua.set_waker(NonNull::from(waker)) };
+        let prev = lua.set_waker(NonNull::from(waker));
         Ok(WakerGuard {
             lua,
             prev,
@@ -647,7 +647,7 @@ impl<'lua, 'a> WakerGuard<'lua, 'a> {
 #[cfg(feature = "async")]
 impl Drop for WakerGuard<'_, '_> {
     fn drop(&mut self) {
-        unsafe { self.lua.set_waker(self.prev) };
+        self.lua.set_waker(self.prev);
     }
 }
 

src/types.rs

@@ -20,6 +20,9 @@ pub use either::Either;
 pub use registry_key::RegistryKey;
 pub(crate) use value_ref::ValueRef;
 
+#[cfg(feature = "async")]
+pub(crate) use value_ref::ValueRefIndex;
+
 /// Type of Lua integer numbers.
 pub type Integer = ffi::lua_Integer;
 /// Type of Lua floating point numbers.

src/types/value_ref.rs

@@ -1,22 +1,39 @@
 use std::fmt;
 use std::os::raw::{c_int, c_void};
 
+use super::XRc;
 use crate::state::{RawLua, WeakLua};
 
 /// A reference to a Lua (complex) value stored in the Lua auxiliary thread.
+#[derive(Clone)]
 pub struct ValueRef {
     pub(crate) lua: WeakLua,
+    // Keep index separate to avoid additional indirection when accessing it.
     pub(crate) index: c_int,
-    pub(crate) drop: bool,
+    // If `index_count` is `None`, the value does not need to be destroyed.
+    pub(crate) index_count: Option<ValueRefIndex>,
+}
+
+/// A reference to a Lua value index in the auxiliary thread.
+/// It's cheap to clone and can be used to track the number of references to a value.
+#[derive(Clone)]
+pub(crate) struct ValueRefIndex(pub(crate) XRc<c_int>);
+
+impl From<c_int> for ValueRefIndex {
+    #[inline]
+    fn from(index: c_int) -> Self {
+        ValueRefIndex(XRc::new(index))
+    }
 }
 
 impl ValueRef {
     #[inline]
-    pub(crate) fn new(lua: &RawLua, index: c_int) -> Self {
+    pub(crate) fn new(lua: &RawLua, index: impl Into<ValueRefIndex>) -> Self {
+        let index = index.into();
         ValueRef {
             lua: lua.weak().clone(),
-            index,
-            drop: true,
+            index: *index.0,
+            index_count: Some(index),
         }
     }
 
@@ -25,16 +42,6 @@ impl ValueRef {
         let lua = self.lua.lock();
         unsafe { ffi::lua_topointer(lua.ref_thread(), self.index) }
     }
-
-    /// Returns a copy of the value, which is valid as long as the original value is held.
-    #[inline]
-    pub(crate) fn copy(&self) -> Self {
-        ValueRef {
-            lua: self.lua.clone(),
-            index: self.index,
-            drop: false,
-        }
-    }
 }
 
 impl fmt::Debug for ValueRef {
@@ -43,17 +50,15 @@ impl fmt::Debug for ValueRef {
     }
 }
 
-impl Clone for ValueRef {
-    fn clone(&self) -> Self {
-        unsafe { self.lua.lock().clone_ref(self) }
-    }
-}
-
 impl Drop for ValueRef {
     fn drop(&mut self) {
-        if self.drop {
-            if let Some(lua) = self.lua.try_lock() {
-                unsafe { lua.drop_ref(self) };
+        if let Some(ValueRefIndex(index)) = self.index_count.take() {
+            // It's guaranteed that the inner value returns exactly once.
+            // This means in particular that the value is not dropped.
+            if XRc::into_inner(index).is_some() {
+                if let Some(lua) = self.lua.try_lock() {
+                    unsafe { lua.drop_ref(self) };
+                }
             }
         }
     }

src/userdata/object.rs

@@ -15,14 +15,14 @@ impl ObjectLike for AnyUserData {
     fn get<V: FromLua>(&self, key: impl IntoLua) -> Result<V> {
         // `lua_gettable` method used under the hood can work with any Lua value
         // that has `__index` metamethod
-        Table(self.0.copy()).get_protected(key)
+        Table(self.0.clone()).get_protected(key)
     }
 
     #[inline]
     fn set(&self, key: impl IntoLua, value: impl IntoLua) -> Result<()> {
         // `lua_settable` method used under the hood can work with any Lua value
         // that has `__newindex` metamethod
-        Table(self.0.copy()).set_protected(key, value)
+        Table(self.0.clone()).set_protected(key, value)
     }
 
     #[inline]
@@ -30,7 +30,7 @@ impl ObjectLike for AnyUserData {
     where
         R: FromLuaMulti,
     {
-        Function(self.0.copy()).call(args)
+        Function(self.0.clone()).call(args)
     }
 
     #[cfg(feature = "async")]
@@ -39,7 +39,7 @@ impl ObjectLike for AnyUserData {
     where
         R: FromLuaMulti,
     {
-        Function(self.0.copy()).call_async(args)
+        Function(self.0.clone()).call_async(args)
     }
 
     #[inline]
@@ -88,6 +88,6 @@ impl ObjectLike for AnyUserData {
 
     #[inline]
     fn to_string(&self) -> Result<StdString> {
-        Value::UserData(AnyUserData(self.0.copy())).to_string()
+        Value::UserData(AnyUserData(self.0.clone())).to_string()
     }
 }

src/util/mod.rs

@@ -101,15 +101,13 @@ pub(crate) unsafe fn push_string(state: *mut ffi::lua_State, s: &[u8], protect:
 // Uses 3 stack spaces (when protect), does not call checkstack.
 #[cfg(feature = "luau")]
 #[inline(always)]
-pub(crate) unsafe fn push_buffer(state: *mut ffi::lua_State, b: &[u8], protect: bool) -> Result<()> {
-    let data = if protect {
-        protect_lua!(state, 0, 1, |state| ffi::lua_newbuffer(state, b.len()))?
+pub(crate) unsafe fn push_buffer(state: *mut ffi::lua_State, size: usize, protect: bool) -> Result<*mut u8> {
+    let data = if protect || size > const { 1024 * 1024 * 1024 } {
+        protect_lua!(state, 0, 1, |state| ffi::lua_newbuffer(state, size))?
     } else {
-        ffi::lua_newbuffer(state, b.len())
+        ffi::lua_newbuffer(state, size)
     };
-    let buf = slice::from_raw_parts_mut(data as *mut u8, b.len());
-    buf.copy_from_slice(b);
-    Ok(())
+    Ok(data as *mut u8)
 }
 
 // Uses 3 stack spaces, does not call checkstack.
@@ -122,7 +120,7 @@ pub(crate) unsafe fn push_table(
 ) -> Result<()> {
     let narr: c_int = narr.try_into().unwrap_or(c_int::MAX);
     let nrec: c_int = nrec.try_into().unwrap_or(c_int::MAX);
-    if protect || narr >= const { 1 << 30 } || nrec >= const { 1 << 27 } {
+    if protect || narr >= const { 1 << 26 } || nrec >= const { 1 << 26 } {
         protect_lua!(state, 0, 1, |state| ffi::lua_createtable(state, narr, nrec))
     } else {
         ffi::lua_createtable(state, narr, nrec);

src/util/short_names.rs

@@ -1,6 +1,6 @@
-//! Mostly copied from [bevy_utils]
+//! Inspired by bevy's [disqualified]
 //!
-//! [bevy_utils]: https://github.com/bevyengine/bevy/blob/main/crates/bevy_utils/src/short_names.rs
+//! [disqualified]: https://github.com/bevyengine/disqualified/blob/main/src/short_name.rs
 
 use std::any::type_name;
 
@@ -23,8 +23,7 @@ pub(crate) fn short_type_name<T: ?Sized>() -> String {
     while index < end_of_string {
         let rest_of_string = full_name.get(index..end_of_string).unwrap_or_default();
 
-        // Collapse everything up to the next special character,
-        // then skip over it
+        // Collapse everything up to the next special character, then skip over it
         if let Some(special_character_index) =
             rest_of_string.find(|c: char| [' ', '<', '>', '(', ')', '[', ']', ',', ';'].contains(&c))
         {
@@ -32,11 +31,16 @@ pub(crate) fn short_type_name<T: ?Sized>() -> String {
             parsed_name += collapse_type_name(segment_to_collapse);
             // Insert the special character
             let special_character = &rest_of_string[special_character_index..=special_character_index];
-            parsed_name.push_str(special_character);
+            parsed_name += special_character;
+
+            // Remove lifetimes like <'_> or <'_, '_, ...>
+            if parsed_name.ends_with("<'_>") || parsed_name.ends_with("<'_, ") {
+                _ = parsed_name.split_off(parsed_name.len() - 4);
+            }
 
             match special_character {
                 ">" | ")" | "]" if rest_of_string[special_character_index + 1..].starts_with("::") => {
-                    parsed_name.push_str("::");
+                    parsed_name += "::";
                     // Move the index past the "::"
                     index += special_character_index + 3;
                 }
@@ -53,14 +57,18 @@ pub(crate) fn short_type_name<T: ?Sized>() -> String {
 }
 
 #[inline(always)]
-fn collapse_type_name(string: &str) -> &str {
-    string.rsplit("::").next().unwrap()
+fn collapse_type_name(segment: &str) -> &str {
+    segment.rsplit("::").next().unwrap()
 }
 
 #[cfg(test)]
 mod tests {
     use super::short_type_name;
     use std::collections::HashMap;
+    use std::marker::PhantomData;
+
+    struct MyData<'a, 'b>(PhantomData<&'a &'b ()>);
+    struct MyDataT<'a, T>(PhantomData<&'a T>);
 
     #[test]
     fn tests() {
@@ -73,5 +81,7 @@ mod tests {
             "HashMap<String, Option<[i32; 3]>>"
         );
         assert_eq!(short_type_name::<dyn Fn(i32) -> i32>(), "dyn Fn(i32) -> i32");
+        assert_eq!(short_type_name::<MyDataT<&str>>(), "MyDataT<&str>");
+        assert_eq!(short_type_name::<(&MyData, [MyData])>(), "(MyData, [MyData])");
     }
 }

tests/async.rs

@@ -8,7 +8,7 @@ use futures_util::stream::TryStreamExt;
 use tokio::sync::Mutex;
 
 use mlua::{
-    Error, Function, Lua, LuaOptions, MultiValue, ObjectLike, Result, StdLib, Table, UserData,
+    Error, Function, Lua, LuaOptions, MultiValue, ObjectLike, Result, StdLib, Table, ThreadStatus, UserData,
     UserDataMethods, UserDataRef, Value,
 };
 
@@ -667,3 +667,35 @@ async fn test_async_hook() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn test_async_yield_with() -> Result<()> {
+    let lua = Lua::new();
+
+    let func = lua.create_async_function(|lua, (mut a, mut b): (i32, i32)| async move {
+        let zero = lua.yield_with::<MultiValue>(()).await?;
+        assert!(zero.is_empty());
+        let one = lua.yield_with::<MultiValue>(a + b).await?;
+        assert_eq!(one.len(), 1);
+
+        for _ in 0..3 {
+            (a, b) = lua.yield_with((a + b, a * b)).await?;
+        }
+        Ok((0, 0))
+    })?;
+
+    let thread = lua.create_thread(func)?;
+
+    let zero = thread.resume::<MultiValue>((2, 3))?; // function arguments
+    assert!(zero.is_empty());
+    let one = thread.resume::<i32>(())?; // value of "zero" is passed here
+    assert_eq!(one, 5);
+
+    assert_eq!(thread.resume::<(i32, i32)>(1)?, (5, 6)); // value of "one" is passed here
+    assert_eq!(thread.resume::<(i32, i32)>((10, 11))?, (21, 110));
+    assert_eq!(thread.resume::<(i32, i32)>((11, 12))?, (23, 132));
+    assert_eq!(thread.resume::<(i32, i32)>((12, 13))?, (0, 0));
+    assert_eq!(thread.status(), ThreadStatus::Finished);
+
+    Ok(())
+}

tests/buffer.rs

@@ -1,5 +1,7 @@
 #![cfg(feature = "luau")]
 
+use std::io::{Read, Seek, SeekFrom, Write};
+
 use mlua::{Lua, Result, Value};
 
 #[test]
@@ -41,7 +43,7 @@ fn test_buffer() -> Result<()> {
 }
 
 #[test]
-#[should_panic(expected = "range end index 14 out of range for slice of length 13")]
+#[should_panic(expected = "out of range for slice of length 13")]
 fn test_buffer_out_of_bounds_read() {
     let lua = Lua::new();
     let buf = lua.create_buffer(b"hello, world!").unwrap();
@@ -49,9 +51,73 @@ fn test_buffer_out_of_bounds_read() {
 }
 
 #[test]
-#[should_panic(expected = "range end index 16 out of range for slice of length 13")]
+#[should_panic(expected = "out of range for slice of length 13")]
 fn test_buffer_out_of_bounds_write() {
     let lua = Lua::new();
     let buf = lua.create_buffer(b"hello, world!").unwrap();
     buf.write_bytes(14, b"!!");
 }
+
+#[test]
+fn create_large_buffer() {
+    let lua = Lua::new();
+    let err = lua.create_buffer_with_capacity(1_073_741_824 + 1).unwrap_err(); // 1GB
+    assert!(err.to_string().contains("memory allocation error"));
+
+    // Normal buffer is okay
+    let buf = lua.create_buffer_with_capacity(1024 * 1024).unwrap();
+    assert_eq!(buf.len(), 1024 * 1024);
+}
+
+#[test]
+fn test_buffer_cursor() -> Result<()> {
+    let lua = Lua::new();
+    let mut cursor = lua.create_buffer(b"hello, world")?.cursor();
+
+    let mut data = Vec::new();
+    cursor.read_to_end(&mut data)?;
+    assert_eq!(data, b"hello, world");
+
+    // No more data to read
+    let mut one = [0u8; 1];
+    assert_eq!(cursor.read(&mut one)?, 0);
+
+    // Seek to start
+    cursor.seek(SeekFrom::Start(0))?;
+    cursor.read_exact(&mut one)?;
+    assert_eq!(one, [b'h']);
+
+    // Seek to end -5
+    cursor.seek(SeekFrom::End(-5))?;
+    let mut five = [0u8; 5];
+    cursor.read_exact(&mut five)?;
+    assert_eq!(&five, b"world");
+
+    // Seek to current -1
+    cursor.seek(SeekFrom::Current(-1))?;
+    cursor.read_exact(&mut one)?;
+    assert_eq!(one, [b'd']);
+
+    // Invalid seek
+    assert!(cursor.seek(SeekFrom::Current(-100)).is_err());
+    assert!(cursor.seek(SeekFrom::End(1)).is_err());
+
+    // Write data
+    let buf = lua.create_buffer_with_capacity(100)?;
+    cursor = buf.clone().cursor();
+
+    cursor.write_all(b"hello, ...")?;
+    cursor.seek(SeekFrom::Current(-3))?;
+    cursor.write_all(b"Rust!")?;
+
+    assert_eq!(&buf.read_bytes::<12>(0), b"hello, Rust!");
+
+    // Writing beyond the end of the buffer does nothing
+    cursor.seek(SeekFrom::End(0))?;
+    assert_eq!(cursor.write(b".")?, 0);
+
+    // Flush is no-op
+    cursor.flush()?;
+
+    Ok(())
+}

tests/luau.rs

@@ -330,6 +330,15 @@ fn test_interrupts() -> Result<()> {
     assert_eq!(yield_count.load(Ordering::Relaxed), 7);
     assert_eq!(co.status(), ThreadStatus::Finished);
 
+    // Test no yielding at non-yieldable points
+    yield_count.store(0, Ordering::Relaxed);
+    let co = lua.create_thread(lua.create_function(|lua, arg: Value| {
+        (lua.load("return (function(x) return x end)(...)")).call::<Value>(arg)
+    })?)?;
+    let res = co.resume::<String>("abc")?;
+    assert_eq!(res, "abc".to_string());
+    assert_eq!(yield_count.load(Ordering::Relaxed), 3);
+
     //
     // Test errors in interrupts
     //

tests/scope.rs

@@ -382,7 +382,8 @@ fn test_scope_userdata_ref() -> Result<()> {
         modify_userdata(&lua, &ud)?;
 
         // We can only borrow userdata scoped
-        assert!((matches!(ud.borrow::<MyUserData>(), Err(Error::UserDataTypeMismatch))));
+        #[rustfmt::skip]
+        assert!(matches!(ud.borrow::<MyUserData>(), Err(Error::UserDataTypeMismatch)));
         ud.borrow_scoped::<MyUserData, ()>(|ud_inst| {
             assert_eq!(ud_inst.0.get(), 2);
         })?;
@@ -419,7 +420,8 @@ fn test_scope_userdata_ref_mut() -> Result<()> {
         let ud = scope.create_userdata_ref_mut(&mut data)?;
         modify_userdata(&lua, &ud)?;
 
-        assert!((matches!(ud.borrow_mut::<MyUserData>(), Err(Error::UserDataTypeMismatch))));
+        #[rustfmt::skip]
+        assert!(matches!(ud.borrow_mut::<MyUserData>(), Err(Error::UserDataTypeMismatch)));
         ud.borrow_mut_scoped::<MyUserData, ()>(|ud_inst| {
             ud_inst.0 += 10;
         })?;

tests/table.rs

@@ -61,6 +61,15 @@ fn test_table() -> Result<()> {
     Ok(())
 }
 
+#[test]
+#[cfg(target_os = "linux")] // Linux allow overcommiting the memory (relevant for CI)
+fn test_table_with_large_capacity() {
+    let lua = Lua::new();
+
+    let t = lua.create_table_with_capacity(1 << 26, 1 << 26);
+    assert!(t.is_ok());
+}
+
 #[test]
 fn test_table_push_pop() -> Result<()> {
     let lua = Lua::new();

tests/thread.rs

@@ -1,6 +1,6 @@
 use std::panic::catch_unwind;
 
-use mlua::{Error, Function, Lua, Result, Thread, ThreadStatus};
+use mlua::{Error, Function, IntoLua, Lua, Result, Thread, ThreadStatus, Value};
 
 #[test]
 fn test_thread() -> Result<()> {
@@ -252,3 +252,24 @@ fn test_thread_resume_error() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn test_thread_resume_bad_arg() -> Result<()> {
+    let lua = Lua::new();
+
+    struct BadArg;
+
+    impl IntoLua for BadArg {
+        fn into_lua(self, _lua: &Lua) -> Result<Value> {
+            Err(Error::runtime("bad arg"))
+        }
+    }
+
+    let f = lua.create_thread(lua.create_function(|_, ()| Ok("okay"))?)?;
+    let res = f.resume::<()>((123, BadArg));
+    assert!(matches!(res, Err(Error::RuntimeError(msg)) if msg == "bad arg"));
+    let res = f.resume::<String>(()).unwrap();
+    assert_eq!(res, "okay");
+
+    Ok(())
+}

tests/userdata.rs

@@ -525,6 +525,11 @@ fn test_fields() -> Result<()> {
                 Ok(())
             });
 
+            // Field that emulates method
+            fields.add_field_function_get("val_fget", |lua, ud| {
+                lua.create_function(move |_, ()| Ok(ud.borrow::<MyUserData>()?.0))
+            });
+
             // Use userdata "uservalue" storage
             fields.add_field_function_get("uval", |_, ud| ud.user_value::<Option<String>>());
             fields.add_field_function_set("uval", |_, ud, s: Option<String>| ud.set_user_value(s));
@@ -537,6 +542,10 @@ fn test_fields() -> Result<()> {
                 })
             })
         }
+
+        fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
+            methods.add_method("dummy", |_, _, ()| Ok(()));
+        }
     }
 
     globals.set("ud", MyUserData(7))?;
@@ -546,6 +555,7 @@ fn test_fields() -> Result<()> {
         assert(ud.val == 7)
         ud.val = 10
         assert(ud.val == 10)
+        assert(ud:val_fget() == 10)
 
         assert(ud.uval == nil)
         ud.uval = "hello"