C++ - Check if pointer is pointing to valid memory (Can't use NULL checks here)

Question

I am creating scripting language. When I allocate thing ,it\'s allocate the thing and returns the address and then I do whatever with it and then delete it. I can\'t contro

Answer 1

You can use shared_ptr<> to hold your pointer, and use weak_ptr<> to pass your pointer around to consumers of the object. You delete the object by destroying the shared_ptr<> object, and then all the weak_ptr<>s will become expired.

std::weak_ptr wptr;
assert(wptr.expired());
{
    std::shared_ptr intptr(new int);
    wptr = intptr;
    assert(!wptr.expired());
}
assert(wptr.expired());

So, your exists check would be to check if the weak_ptr<> is expired or not.

To make the usage of the construct a little more concrete:

Script code                 Hypothetical C++ code that gets executed
----                        ----
var MyVar=new MyStruct();   var_map["MyVar"]
                                = std::shared_ptr(new Obj("MyStruct"));
Func(MyVar);                invoke("Func", std::weak_ptr(var_map["MyVar"]));
exists(arg0)                !args[0].expired()
delete(MyVar);              var_map.erase("MyVar");

If the script is to operate in a multi-threaded environment, then the weak_ptr<> state is a critical section.