C++ volatile member functions

Question

class MyClass
{
    int x, y;
    void foo() volatile {
        // do stuff with x
        // do stuff with y
    }   
};

Do I need to declare

Answer 1

The following code:

#include 

class Bar
{
    public:

        void test();
};

class Foo
{
    public:

        void test() volatile { x.test(); }

    private:

        Bar x;
};

int main()
{
    Foo foo;

    foo.test();

    return 0;
}

Raises an error upon compilation with gcc:

main.cpp: In member function 'void Foo::test() volatile':
main.cpp:14:33: error: no matching function for call to 'Bar::test() volatile'
main.cpp:7:8: note: candidate is: void Bar::test() 

And since a volatile instance can't call a non-volatile method, we can assume that, yes, x and y will be volatile in the method, even if the instance of MyClass is not declared volatile.

Note: you can remove the volatile qualifier using a const_cast<> if you ever need to; however be careful because just like const doing so can lead to undefined behavior under some cases.