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Asked: 2026-05-15T07:39:34+00:00

I was curious about C++ and virtual inheritance – in particular, the way that

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I was curious about C++ and virtual inheritance – in particular, the way that vtable conflicts are resolved between bass and child classes. I won’t pretend to understand the specifics on how they work, but what I’ve gleamed so far is that their is a small delay caused by using virtual functions due to that resolution. My question then is if the base class is blank – ie, its virtual functions are defined as:

virtual void doStuff() = 0;

Does this mean that the resolution is not necessary, because there’s only one set of functions to pick from?

Forgive me if this is an stupid question – as I said, I don’t understand how vtables work so I don’t really know any better.

EDIT

So if I have an abstract class with two seperate child classes:

    A
   / \
  /   \
 B     C

There is no performance hit when calling functions from the child classes compared to say, just a single inheritance free class?

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1 Answer

  1. Editorial Team

    There is no hit for calling nonvirtual functions in the child class. If you’re calling an overridden version of your pure virtual function as in your example, then the virtual penalty may still exist. In general it’s difficult for compilers to optimize away the use of the virtual table except under very specific circumstances, where it knows the exact by-value type of the object in question (from context).

    But seriously don’t worry about the overhead. It’s going to be so little that in practice you will almost certainly never encounter a situation where it’s the part of code causing performance bottlenecks. Use virtual functions where they make sense for your design and don’t worry about the (tiny) performance penalty.

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