Question

Const functions don’t seem to care if you dereference a member-pointer into a non-const reference. It’s also possible to return non-const member-pointers. However it’s not allowed to return a reference or an address of a data member that has a value type.

Why?

class Class
{
public:
unsigned int& value2(void) const
{
    *m_ptr = 10;
    return *m_ptr; 
    //Why?
}

unsigned int* value3(void) const
{
    return m_ptr; //Why?
}

private:
unsigned int* m_ptr;
};

Answer 1

EDIT:

Regarding your code: you’re never actually changing the member or returning a reference to it.

unsigned int& value2(void) const
{
    *m_ptr = 10;
    return *m_ptr; 
                //Why?
}
//returns the value your member points to, not your member

unsigned int* value3(void) const
{
    return m_ptr; //Why?
}
//returns a copy of your member

What would be disallowed would be the version I posted in my snippet.

For example:

struct A
{
   int * x;
   int& getX() const { return *x; }
   int* getX1() const { return x; }
   int*& getX2() const { return x; } //error here
};

Only the last method will return an error, because:

• first one returns the value, which is not const. The pointer is const.
• second one returns the pointer by value, which again is ok
• the third one actually returns the member by reference, that’s why it’s illegal