get segfault when creating a pointer c++

Question

I got a Segmentation fault error when I compile it on an online c++ compiler. (The line that throws the error will be pointed out by a comment in the code)

#include <iostream>
#include <memory>

class A
{

};

class B:public A
{

};


using namespace std;
class Base
{
public:
    int b;
    std::shared_ptr<A> Display()
    {
        cout<<"Base: Non-virtual display."<<endl;
    };
    virtual void vDisplay()
    {
        cout<<"Base: Virtual display."<<endl;
    };
};

class Derived : public Base
{
public:
    int d;
    std::shared_ptr<B> Display()
    {
        cout<<"Derived: Non-virtual display."<<endl;
    };
    virtual void vDisplay()
    {
        cout<<"Derived: Virtual display."<<endl;
    };
};

int main()
{
    cout<<"Hello World"<<endl;
    Derived d;
    d.Display();

    Base *b = new Derived; // this line thorws the error
    b->vDisplay();
    return 0;
}

I got a bit confused; if I just create an object instead of pointer, then it's good. Where did I make a mistake?

Answer 1

Error actually happens on the previous line d.Display(); . Control flow leaves Derived::Display() function without returning std::shared_ptr<B> causing Undefined Behavior.

As other people suggest, it would be a good idea to enable compiler warnings and / or actually pay attention to them. This is that one rare case when compilers tend to actually warn about potentially Undefined behavior in your program.