C++ Const Pointer – How to Declare Const Pointer in C++

c++constantspointers

I am reviewing some code and I ran across some code I am unfamiliar with. After some searching I could not come up of any example of why this is done or the benefit of this declaration.

myClass const * const myPtr = myClass->getPointer();

Is this a declaration of a const pointer or something entirely different?

Best Answer

It means "myPtr is a const pointer to a const myClass". It means that you can neither modify what the pointer is pointing at through this pointer nor can you make the pointer point somewhere else after it's initialised (by the return value of myClass->getPointer()). So yes, you're basically right, with the addition that it also points to a const object (as far as you know; it could really be non-const underneath).

Remember that const applies to the item to its left (or if there is no item to its left, the item to its right). The first const makes the myClass const (where you can't modify what the pointer points at) and the second const makes the * const (where you can't modify the pointer itself).

Related Solutions

C – Const Usage with Pointers

const char* is, as you said, a pointer to a char, where you can't change the value of the char (at least not through the pointer (without casting the constness away)).

char* const is a pointer to a char, where you can change the char, but you can't make the pointer point to a different char.

const char* const is a constant pointer to a constant char, i.e. you can change neither where the pointer points nor the value of the pointee.

C++ Const Double Pointer – Explanation and Usage

There's only one const in

double **const cp1 = arr ;
//       ^^^^^

so I'm not sure why you're expecting the other two assignments to produce an error.

If you want it to be const on all levels, you need

const double *const *const cp1 = arr;
//                         ^ cp1 is ...
//                  ^ a const pointer to ...
//           ^ a const pointer to ...
// ^ a const double

Best Answer

Related Solutions

C – Const Usage with Pointers

C++ Const Double Pointer – Explanation and Usage

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