Question

Whilst trawling through some old code I came across something similar to the following:

class Base { public:     virtual int Func();     ... };  class Derived : public Base { public:     int Func(); // Missing 'virtual' qualifier     ... }; 

The code compiles fine (MS VS2008) with no warnings (level 4) and it works as expected – Func is virtual even though the virtual qualifier is missing in the derived class. Now, other than causing some confusion, are there any dangers with this code or should I change it all, adding the virtual qualifier?

Answer 1

The virtual will be carried down to all overriding functions in derived classes. The only real benefit to adding the keyword is to signify your intent a casual observer of the Derived class definition will immediately know that Func is virtual.

Even classes that extend Derived will have virtual Func methods.

Reference: Virtual Functions on MSDN. Scroll down the page to see

The virtual keyword can be used when declaring overriding functions in a derived class, but it is unnecessary; overrides of virtual functions are always virtual.