Const correctness: const char const * const GetName const (//stuff);

Question

Labelled as homework because this was a question on a midterm I wrote that I don\'t understand the answer to. I was asked to explain the purpose of each const in the follow

Answer 1

Given:

const char const * const GetName() const { return m_name; };

The first and second const are equivalent, but only one of them is allowed -- i.e. you can put const before or after the type (char in this case) but only one or the other, not both. Either, however, says that the characters pointed to by the pointer cannot be written to.

The const after the '*' means the pointer returned by the function cannot itself be modified. This is rarely seen on a return type -- what you're returning is a value, which can't be modified in any case (it's normally just assigned to some variable). This can, however, be meaningful in other contexts.

The third const is only allowed on a member function. It says that when this function is called, the this pointer that's received will be a T const * const rather than a T * const, so the member function can only modify static or mutable members of the object, and if it invokes other member functions, they must be const as well. There is, however, a caveat, that it can also cast away the const'ness, in which case it can modify what it sees fit (with the further caveat that if the object was originally defined as const, rather than just having a const pointer to a normal (non-const) object, the results will be undefined).