/* Create a new upvalue at the given level, and link it to the list of open upvalues of 'L' after entry 'prev'.  */
static UpVal* newupval(lua_State *L, int tbc, StkId level, UpVal **prev)
/* Create a new upvalue at the given level, and link it to the list of open upvalues of 'L' after entry 'prev'.  */
static UpVal* newupval(lua_State *L, int tbc, StkId level, UpVal **prev)
{
    L->twups = G(L)->twups;
    G(L)->twups = L;
  }
  return uv;
}