wplua: implement reference counting of the lua_State

modules/module-lua-scripting/module.c

@@ -178,7 +178,7 @@ wp_lua_scripting_plugin_disable (WpPlugin * plugin)
 {
   WpLuaScriptingPlugin * self = WP_LUA_SCRIPTING_PLUGIN (plugin);
 
-  g_clear_pointer (&self->L, wplua_free);
+  g_clear_pointer (&self->L, wplua_unref);
   g_clear_object (&self->export_core);
 }
 

modules/module-lua-scripting/wplua/wplua.c

@@ -101,14 +101,39 @@ wplua_new (void)
     lua_settable (L, LUA_REGISTRYINDEX);
   }
 
+  /* refcount */
+  lua_pushinteger (L, 1);
+  lua_rawsetp (L, LUA_REGISTRYINDEX, L);
+
+  return L;
+}
+
+lua_State *
+wplua_ref (lua_State *L)
+{
+  lua_Integer refcount;
+  lua_rawgetp (L, LUA_REGISTRYINDEX, L);
+  refcount = lua_tointeger (L, -1);
+  lua_pushinteger (L, refcount + 1);
+  lua_rawsetp (L, LUA_REGISTRYINDEX, L);
+  lua_pop (L, 1);
   return L;
 }
 
 void
-wplua_free (lua_State * L)
+wplua_unref (lua_State * L)
 {
-  wp_debug ("closing lua_State %p", L);
-  lua_close (L);
+  lua_Integer refcount;
+  lua_rawgetp (L, LUA_REGISTRYINDEX, L);
+  refcount = lua_tointeger (L, -1);
+  if (refcount > 1) {
+    lua_pushinteger (L, refcount - 1);
+    lua_rawsetp (L, LUA_REGISTRYINDEX, L);
+    lua_pop (L, 1);
+  } else {
+    wp_debug ("closing lua_State %p", L);
+    lua_close (L);
+  }
 }
 
 void

modules/module-lua-scripting/wplua/wplua.h

@@ -49,7 +49,8 @@ typedef enum {
 } WpLuaSandboxFlags;
 
 lua_State * wplua_new (void);
-void wplua_free (lua_State * L);
+lua_State * wplua_ref (lua_State *L);
+void wplua_unref (lua_State * L);
 
 void wplua_enable_sandbox (lua_State * L, WpLuaSandboxFlags flags);
 int wplua_push_sandbox (lua_State * L);
@@ -94,7 +95,7 @@ gboolean wplua_load_path (lua_State * L, const gchar *path, GError **error);
 
 gboolean wplua_pcall (lua_State * L, int nargs, int nres, GError **error);
 
-G_DEFINE_AUTOPTR_CLEANUP_FUNC(lua_State, wplua_free)
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(lua_State, wplua_unref)
 
 G_END_DECLS