const char* allows to modify the string?

August 12, 2022

I understand that using const char* is a modifiable pointer to a constant character. As such, I can only modify the pointer, but not the character. Because of this, I do not understand why I am allowed to do this:

const char* str{"Hello World"};

str = "I change the pointer and in turns it changes the string, but not really.";

How does this work? Is there somewhere in memory where all the characters are stored and I can just point to them as I wish? Furthermore, the adress of str does not change throughout this process. Since the only thing that can change is the address, I really don’t understand what’s going on.

Maybe part of the problem is that I try to understand this as if the string was an integer. If I do:

int number{3};
const int* p_number{&number};

*p_number = 4;

This is not valid, hence why I expect str to not by modifiable. In order words, where am I pointing so that "Hello World" becomes "I change the pointer and this changes the string"?

EDIT:

I get that I create a new string at another address, but when I do:

const char *str{"HelloWorld"};
std::cout << &str << std::endl;
str = "I create new string, but I get same address";
std::cout << &str << std::endl;

I always get the same address twice.

>Solution :

No string was replaced, you just reassigned str a new string which is stored on stack-memory.

Try this snippet, that the address was changed

#include <stdio.h>

int main(void)
{
    const char *ptr = "Hello";
    printf("Before: %p\n", ptr);

    ptr = "World";
    printf("After: %p\n", ptr);
}

Output [RESULT MAY VARY]: