constants - c++ const member function that returns a const pointer.. But what type of const is the returned pointer?

Question

I apologize if this has been asked, but how do I create a member function in c++ that returns a pointer in the following scenerios: 1. The returned pointer is constant, but the junk inside can be modified. 2. The junk inside is constant but the returned pointer can be modified. 3. Neither the junk, nor the pointer can be modified.

Is it like so:

1. int *const func() const
   
2. const int* func() const
3. const int * const func() const

All of the tutorials I've read don't cover this distinction.

Side note: If my method is declared const then the tutorials say that I'm stating that I won't modify the parameters.. But this is not clear enough for me in the case when a parameter is a pointer. Do my parameters need to be like:

a. void func(const int* const x) const;
b. void func(const int* x) const;
c. void func(const int* const x) const;

Answer 1

I don't know what book you have read, but if you mark a method const it means that this will be of type const MyClass* instead of MyClass*, which in its turn means that you cannot change nonstatic data members that are not declared mutable, nor can you call any non-const methods on this.

Now for the return value.

1 . int * const func () const

The function is constant, and the returned pointer is constant but the 'junk inside' can be modified. However, I see no point in returning a const pointer because the ultimate function call will be an rvalue, and rvalues of non-class type cannot be const, meaning that const will be ignored anyway

2 . const int* func () const

This is a useful thing. The "junk inside" cannot be modified

3 . const int * const func() const

semantically almost the same as 2, due to reasons in 1.

HTH