Add lua_getmetatablepointer custom helper

Author: khvzak

luau/Custom/src/lextra.cpp

@@ -0,0 +1,21 @@
+#include "lua.h"
+#include "lapi.h"
+#include "lobject.h"
+#include "lstate.h"
+
+extern "C" const void* lua_getmetatablepointer(lua_State* L, int objindex)
+{
+    const TValue* obj = luaA_toobject(L, objindex);
+    if (!obj)
+        return NULL;
+
+    switch (ttype(obj))
+    {
+    case LUA_TTABLE:
+        return hvalue(obj)->metatable;
+    case LUA_TUSERDATA:
+        return uvalue(obj)->metatable;
+    default:
+        return NULL;
+    }
+}

src/lib.rs

@@ -184,6 +184,8 @@ impl Build {
         let custom_lib_name = "luaucustom";
         config
             .clone()
+            .include(&vm_include_dir)
+            .include(&vm_source_dir)
             .include(&common_include_dir)
             .add_files_by_ext(&custom_source_dir, "cpp")
             .out_dir(&lib_dir)

testcrate/Cargo.toml

@@ -2,6 +2,7 @@
 name = "testcrate"
 version = "0.1.0"
 authors = ["Aleksandr Orlenko <[email protected]>"]
+edition = "2021"
 
 [build-dependencies.luau0-src]
 path = ".."

testcrate/src/lib.rs

@@ -33,6 +33,12 @@ extern "C" {
         cont: *const c_void,
     );
 
+    pub fn lua_createtable(state: *mut c_void, narr: c_int, nrec: c_int);
+    pub fn lua_setmetatable(state: *mut c_void, index: c_int) -> c_int;
+    pub fn lua_getmetatable(state: *mut c_void, index: c_int) -> c_int;
+    pub fn lua_getmetatablepointer(state: *mut c_void, index: c_int) -> *const c_void;
+    pub fn lua_topointer(state: *mut c_void, index: c_int) -> *const c_void;
+
     pub fn luau_compile(
         source: *const c_char,
         size: usize,
@@ -112,6 +118,27 @@ fn test_luau() {
     }
 }
 
+#[test]
+fn test_metatablepointer() {
+    use std::ptr;
+    unsafe {
+        let state = luaL_newstate();
+        assert!(state != ptr::null_mut());
+
+        lua_createtable(state, 0, 0);
+        assert!(lua_getmetatablepointer(state, -1).is_null());
+
+        lua_createtable(state, 0, 0);
+        let mt_ptr1 = lua_topointer(state, -1);
+
+        lua_setmetatable(state, -2);
+        let mt_ptr2 = lua_getmetatablepointer(state, -1);
+        assert_eq!(mt_ptr1, mt_ptr2);
+
+        lua_close(state);
+    }
+}
+
 #[test]
 fn test_exceptions() {
     use std::{ptr, slice, str};