Calling volatile member function using not volatile object in C++

Question

What happens, If calling volatile member function using not volatile object?

#include <iostream>
using namespace std;

class A 
{
private:
    int x;
public:
    void func(int a) volatile //volatile function
    {
        x = a;
        cout<<x<<endl;
    }
};

int main() 
{
    A a1; // non volatile object
    a1.func(10);
    return 0;
}

Answer 1

The rule is same as const member function. A volatile member function could be called on a non-volatile object, but a non-volatile member function couldn't be called on a volatile object.

For your case, A::func() will be invoked fine. If you make them opposite, the compilation would fail.

class A 
{
private:
    int x;
public:
    void func(int a) // non-volatile member function
    {
        x = a;
        cout<<x<<endl;
    }
};

int main() 
{
    volatile A a1;   // volatile object
    a1.func(10);     // fail
    return 0;
}