Constant Pointers
This article is quite advanced and assumes you have an understanding of C++. If not, please refer to the C++ section of this book!
Constant Pointers are quite straightforward - as with any other standard const variable in C++, it’s a type of pointer that cannot be reassigned to point to a different memory address. It still allows read-write access to the pointed-to variable though!
int someVar = 69;
int* const constPointer = &someVar;
// It is illegal to go:
// constPointer = &someOtherVar;
It offers a few benefits:
- The pointer itself is constant and cannot be reassigned to point to a different memory location. This enforces that the pointer always points to the same memory address.
- The value pointed to by constPtr can be modified, but the pointer itself cannot be used to modify the pointed-to value. This ensures that the memory address remains constant, but the data it points to can be read and modified.
- Helps prevent accidental reassignment of the pointer to a different memory location, reducing the risk of unintended side effects in the code.
- Offers a consistent and clear contract about the immutability of the pointer, making the code more readable and maintainable.
- When used in function parameters or class member functions, const pointers contribute to designing safer interfaces by indicating that the function/method will not modify the pointer itself, offering const-correctness.
- Allows the compiler to make certain optimizations based on const-correctness, potentially leading to more efficient code.
#include <iostream>
int main()
{
int value = 69;
// Constant pointer to int
int* const constPtr = &value;
// Cannot reassign constPtr to point to a different integer
// constPtr = &anotherValue; // Error: Cannot reassign a const pointer
// Can modify the pointed-to value through constPtr
*constPtr = 420;
// Access to the modified value
std::cout << "Value: " << *constPtr << std::endl;
return 0;
}