Yes. I can't see what im doing wrong

the map is string, int

Here the method

bange::function::Add(lua_State *vm){  
 //userdata, function  
 if (!lua_isfunction(vm, 2)){  
  cout << "bange: AddFunction: First argument isn't a function." << endl;  
  return false;}  
 void *pfunction = const_cast<void *>(lua_topointer(vm, 2));  
 char key[32] = {0};  
 snprintf(key, 32, "%p", pfunction);  
 cout << "Key: " << key << endl;  
 string strkey = key;  
 if (this->functions.find(strkey) != this->functions.end()){  
     luaL_unref(vm, LUA_REGISTRYINDEX, this->functions[strkey]);}  
 this->functions[strkey] = luaL_ref(vm, LUA_REGISTRYINDEX);  
 return true;  

Ok, when the code is executed...

Program received signal SIGSEGV, Segmentation fault.  
0x00007ffff6e6caa9 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >
::compare(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const () from /usr/lib/libstdc++.so.6

Seriously, what's wrong with my code. Thanks for help.

Edit 1:

Ok, I've done the solution and still fails. I've tried directly insert a string but gives the same error.

Let's see, the object is a bange::scene inherited from bange::function. I create the object with lua_newuserdata:

bange::scene *scene = static_cast<bange::scene *>(lua_newuserdata(vm, sizeof(bange::scene)));
(...)
scene = new (scene) bange::scene(width, height, nlayers, vm);

I need this for LUA garbage collection. Now the access to bange::function::Add from Lua:

static int bangefunction_Add(lua_State *vm){
    //userdata, function
    bange::function *function = reinterpret_cast<bange::function *>(lua_touserdata(vm, 1));
    cout &lt&lt "object with bange::function: " &lt&lt function << endl;
    bool added = function->bange::function::Add(vm);
    lua_pushboolean(vm, static_cast<int>(added));
    return 1;
}

Userdata is bange::scene stored in Lua. Knowing that userdata is scene, in fact, the object's direction is the same when I've created the scene before. I need the reinterpret_cast, and then call the method. The pointer "this" is still the same direction inside the method.

solved

I did a small test in the bange::function constructor which works without problems.

bange::function::function(){  
    string test("test");  
    this->functions["test"] = 2;  
}  

I finally noticed that the problem is

bange::function *function = reinterpret_cast<bange::function *>(lua_touserdata(vm, 1));

because the object is bange::scene and no bange::function (i admit it, a pointer corruption) and this seems more a code design issue. So this, in a way, is solved. Thanks everybody.