List Iterator Access Violation

I have a list of pointers to SomeClass objects in a Main class. Whilst in Main I can iterate over the list using list::begin() and list::end().

When I do the same from an instance of SomeClass (bearing in mind that the list is a public member of the Main class) I get the following exception:

0xC0000005: Access violation reading location 0xbaadf0ad.

I am fairly new to coding in C++ coming from a Python background, so I apologise if something doesn't make sense.

Here is an example of the situation:

EDIT: The Main class codes is not actually inside the constructor, its in a method called InitialiseObjects().

EDIT: The exceptions comes from within the list::being() method with the line return (iterator(_Nextnode(_Myhead), this));

#include <list>
using namespace std;

class Main
{
public:
    Main::InitialiseObjects()
    {
        // Execution starts here
        SomeClass someClass = new SomClass(this);
        someClasses.push_back(someClass);

        // This works fine
        for (list<SomeClass*>::iterator it = someClasses.begin(); it != someClasses.end(); it++)
            ...

        someClass->AFunction();
    }
    list<SomeClass*> someClasses;
}

class SomeClass
{
public:
    SomeClass::SomeClass(Main *main) : main(main) {}
    void SomeCla开发者_JAVA技巧ss::AFunction()
    {
        // This will not work throwing the aformentioned error
        for (list<SomeClass*>::iterator it = main->someClasses.begin(); it != main->someClasses.end(); it++)
            ...
    }
private:
    Main *main;
}

0xC0000005: Access violation reading location 0xbaadf0ad.

I think that was 0xbaadf00d until you overwrote something in it, which indicates uninitialized heap memory. So, maybe you're dereferencing a non-existant Main*? E.g. main->someClasses.begin() may throw your exception, if main wasn't initialized yet.
And indeed, this is the problem in your code. someClass->AFunction(); calls the function while you're inside the Main-constructor. As such, this will not be completely valid yet, so you can't use it inside the AFunction.

As long as you remain inside the Main constructor, the this instance is not yet fully initialised!

Trying to access the instance from elsewhere leads to undefined behaviour. This is happening here since you are accessing this unfinished instance from within SomeClass.