Question

I have polymorphic classes and I want to convert an object via dynamic_cast<B>(A) although with compiler optimization /GR I receive a message that it may cause undefined behavior. I’m using static_cast instead, but it does no run-time checks and is unsafe for my classes. Also is it valid to return a stack CString object from a class?

CString CKingdomWar::GetTeamName( eUserTeam eTeam )
{
    if( eTeam == ELDAR )
        return CString( "Eldar" );
    else if( eTeam == ELWYN )
        return CString( "Elwyn" );
    else if( eTeam == NORGNAGON )
        return CString( "Norgnagon" );

    return CString( " " );
}

Answer 1

As already commented, your CString is returned by value and it’s not a problem.

Regarding the static/dynamic casting, you should show the specific code that gives the warning. You don’t normally get such warnings if you use dynamic_cast correctly (that is, to convert pointers or references between compatible types).

If dynamic_cast<B>(A) is to work, then A and B should both be a pointer or reference to an object in the same inheritance tree. For instance, if you had:

class A {
    // ...
};

class B : public A {
    // ...
};

A* inst = new B;

Then dynamic_cast<B*>(inst) is okay. Same deal with references. If inst is not of type B then the pointer version will return NULL, or the reference version will throw an exception.

However, you can’t do this:

A inst;
B nonono = dynamic_cast<B>(inst);