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Diamond inheritance is its own special kind of hell, but “protected virtual” members of java and c# are the “evil at scale” that’s still with us today. An easy pattern that leads to combinatorial explosion beyond the atoms in the universe. Trivially.

People need to look at a playing deck. 52 cards, and you get 8×10^67 possible orders of the deck. Don’t replicate this in code.

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At least C# methods are not virtual by default like in Java.

Why do protected virtual methods lead to an explosion?

Protected = subclasses can call them.

Virtual = subclasses can override them.

So basically, any subclass can call the method, and that method may be overridden in any other subclass.

What is the issue with those overrides? They only affect that one path in the hierarchy of inheritance, no? Not a C++ user here, but I imagine it would be catastrophic, if an unrelated (not on path to root superclass) class could override a method and affect unrelated classes/objects.

> They only affect that one path in the hierarchy of inheritance, no?

Not necessarily. If you create a diamond (or a spiderweb :) inheritence pattern, the amount of places the method can be called and overriden grows fast.

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