luaL_newmetatable sets __name on all Lua versions.

Author: siffiejoe

c-api/compat-5.3.h

@@ -259,6 +259,9 @@ COMPAT53_API size_t lua_stringtonumber (lua_State *L, const char *s);
 #define luaL_getmetafield(L, o, e) \
   (luaL_getmetafield(L, o, e) ? lua_type(L, -1) : LUA_TNIL)
 
+#define luaL_newmetatable(L, tn) \
+  (luaL_newmetatable(L, tn) ? (lua_pushstring(L, tn), lua_setfield(L, -2, "__name"), 1) : 0)
+
 #define luaL_requiref COMPAT53_CONCAT(COMPAT53_PREFIX, L_requiref_53)
 COMPAT53_API void luaL_requiref (lua_State *L, const char *modname,
                                  lua_CFunction openf, int glb );

tests/testmod.c

@@ -205,7 +205,10 @@ static int test_udata (lua_State *L) {
   (void)u2;
   lua_pushlightuserdata(L, luaL_testudata(L, u1pos, tname));
   lua_pushlightuserdata(L, luaL_testudata(L, u2pos, tname));
-  return 2;
+  luaL_getmetatable(L, "utype1");
+  lua_getfield(L, -1, "__name");
+  lua_replace(L, -2);
+  return 3;
 }
 
 static int test_subtable (lua_State *L) {