Object slicing is what happens when you have an inheritance hierarchy but pass an object of a derived type to a function that accepts a base object by value, or perform an assignment to a variable of the base type.
struct A {
A(int _a) : a(_a) {}
int a;
};
struct B : public A {
B(int _a, float _b) : A(_a), b(_b) {}
float b;
};
void foo( A x ) {
std::cout << x.a << std::endl;
}
int main() {
B y = { 1, 2 };
foo(y); // "slices" just the A part of y and sends it to foo.
A z = y; // Also "slices" in initialization.
foo(z);
}
That the language allows this value-conversion implicitly at all can be seen as problematic on its own, but the use of virtual functions can cause slicing behavior to be even more surprising: https://www.geeksforgeeks.org/object-slicing-in-c/
