Re: Re move an object from the lua state!

I am not sure but I would say allocate your enemy from C++ side with a
factory for example instead of using luabind bound constructor. The
moment you call Enemy.__init(self, name); you create something lua
will collect on lua_close.
Plus you override your C++ function "Enemy * CreateEnemy(std::string
const & name)" by creating a lua one "function CreateEnemy(name)".

when you do  "delete e;" I would say you delete from C++ memory
allocated by lua via "return(Zombie(name));". When you call lua_close,
lua still has references towards that zombie and tries to delete it
despite you've already deleted it ?
I may be wrong but that's how I see it.

Some posts that might interest you:
http://lua-list.2524044.n2.nabble.com/Lunar-C-and-premature-object-destruction-td3193945.html
http://stackoverflow.com/questions/1047212/detecting-stale-c-references-in-lua



On Tue, Aug 2, 2011 at 6:37 AM, Sympaval <[email protected]> wrote:
>
> Hi all!
>
> I a  problem since two days now, while integreting lua to C++. I look at all
> message corresponding to that issue here, but the answers are not clearly
> explaned to help me, and here I would like to get the ritght way to achieve
> what I would like to do.
>
> In fact I have a c++ class wraped with luabind and exported to lua. I would
> like to be able to create a new instance of my class in lua, get it and
> delete it from c++.
> Actually i can create new instances of my object, and delete them without
> problem, but when I close the lua state with lua_close(myLuaState), the
> programme segfault. When i comment thje lua_close function all thinks are
> ok. I realise that it's beacause when the lua_close is called, it tries to
> call the destructor of all objects in the  lua state.
> Then I would like to delete the object from the c++ side when i want, and
> remove it from the lua state. How can i achieve that?
> This question has been already posted here in another way, but i didn't find
> a answer which solve my problem.
> I read the programming in lua documentation but I do not see how to proceed.
> This is my code.
>
> extern "C" {
> #include <lua.h>
> }
>
> #include <iostream>
> #include <lua.hpp>
> #include <luabind.hpp>
> #include <stdio.h>
>
> class Enemy {
> private:
>  std::string name;
>
> public:
>  Enemy(const std::string& n)
>    : name(n)
>  {
>    std::cout << "New enemy born with name : " << name << ".\n";
>  }
>
>  Enemy(Enemy const & other)
>    : name(other.name)
>  {
>    std::cout << "Copy of enemy made : " << other.name << ".\n";
>  }
>
>  const std::string& getName() const
>  {
>    std::cout << "Enamy name has been asked and given.\n";
>    return name;
>  }
>
>  void setName(const std::string& n) {
>    name = n;
>  }
>
>  virtual int update()
>  {
>    std::cout << "Enemy::update() called.\n";
>    return (43);
>  }
> };
>
> class EnemyWrapper : public Enemy, public luabind::wrap_base {
> public:
>  EnemyWrapper(const std::string& n)
>    : Enemy(n) {
>  }
>
>  virtual int update() {
>    return (call<int>("update"));
>  }
> }
>
> Enemy * CreateEnemy(std::string const & name)
> {
>  return new Enemy(name);
> }
>
>
> int main() {
> lua_State *  L = lua_open()
>  luabind::open(L);
>  luaL_openlibs(L);
>
>  luabind::module(L) [
>                      luabind::class_<Enemy, EnemyWrapper>("Enemy")
>                      .def(luabind::constructor<const std::string&>())
>                      .property("name", &Enemy::getName, &Enemy::setName)
>                      .def("update", &Enemy::update,
> &EnemyWrapper::default_update)
>                      .def("CreateEnemy", &CreateEnemy)
>                      ];
>
>  if (luaL_dofile(L, "wrapping.lua") != 0)
>    std::cout << lua_tostring(L, -1) << std::endl;
>  int i = 1;
>  for (; i <= 10; ++i)
>    {
>      std::cout << i << " " ;
>      Enemy * e = luabind::call_function<Enemy *>(L, "CreateEnemy", "toto");
>      printf("%p :", e);
>      std::cout << e->update() << std::endl;
>      sleep(1);
>      delete e;
>    }
>  lua_close(L);
> }
>
> Lua code:
> print("Start the  script");
>
> class 'Zombie' (Enemy)
>
> function Zombie:__init(name)
>   Enemy.__init(self, name);
> end
>
> function Zombie:update()
>   print('Zombie:update() called.');
>   self.talk();
>   return (72);
> end
>
> function Zombie:talk()
>   print("Yeah I'm a monster");
> end
>
> function CreateEnemy(name)
> return(Zombie(name));
> end
>
>
>
>
>
>
>
>
>
> --
> View this message in context: http://old.nabble.com/Remove-an-object-from-the-lua-state%21-tp32174811p32174811.html
> Sent from the Lua C++ Bind mailing list archive at Nabble.com.
>
>
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