gistfile1.txt

bool
BindingInstance::construct()
{
  ink_release_assert(this->lua == nullptr);

  if ((this->lua = luaL_newstate())) {
    luaL_openlibs(this->lua);

    // Push a pointer to ourself into the well-known registry key.

    // We do not use lightuserdata here because BindingInstance variables
    // are often declared on stack which would make "this" a stack variable.
    // While this might seem fine and actually work on many platforms, those
    // 64bit platforms with split VA space where heap and stack may live in
    // a separate 47bit VA will violate internal assumptions that luajit
    // places on lightuserdata. Plain userdata will provide luajit-happy
    // address in which we have the full 64bits to store our pointer to this.
    // see: https://www.circonus.com/2016/07/luajit-illumos-vm/

    BindingInstance **lua_surrogate;
    lua_surrogate = (BindingInstance **)lua_newuserdata(this->lua, sizeof(BindingInstance *));
    *lua_surrogate = this;
    lua_setfield(this->lua, LUA_REGISTRYINDEX, selfkey);

    ink_release_assert(BindingInstance::self(this->lua) == this);
  }

  return this->lua;
}