Function lua_newuserdata

third-party/lua-5.2.4/src/lapi.c:1175–1184

LUA_API void *lua_newuserdata (lua_State *L, size_t size) {
  Udata *u;
  lua_lock(L);
  luaC_checkGC(L);
  u = luaS_newudata(L, size, NULL);
  setuvalue(L, L->top, u);
  api_incr_top(L);
  lua_unlock(L);
  return u + 1;
}