What is slicing problem in C++/cpp?

What is slicing problem in C++?

Slicing is where you assign an object of a derived class to an instance of a base class, thereby losing part of the information - some of it is “sliced” away.

For example,

class A {
int foo;

class B : public A
int bar;

So an object of type B has two data members, foo and bar

Then if you were to write this:

B b;

A a = b;

Then the information in b about member bar is lost in a.