Is it possible to convert an integer pointer to the actual integer located at that memory location?

Question

Normally, we declare variables like this in C++:

int exampleInteger;

What if I have a pointer to the address of an integer? Can I declare an integer located at a certain memory address?

int* exampleIntegerPtr = (int*) 0x457FB;
int exampleInteger = *exampleIntegerPtr;

Unfortunately, exampleInteger in the second example isn't like exampleInteger in the first example. The second example creates a new variable that has the same value as the integer located at exampleIntegerPtr. Is it possible to somehow grab the actual integer located at exampleIntegerPtr?

you can just use *aPtr in whatever calculation you want to use the integer in. Or declare a new integer and copy that value into it. — Kate Gregory, Jun 08 '13 at 02:10

score 4 · Accepted Answer · answered Jun 08 '13 at 02:10

4

Yes, you can do it using references, like this:

int &a(*aPtr);

At this point, any changes done to the int stored at aPtr will be reflected in a:

*aPtr = 123;
cout << a << endl; // 123 is printed
*aPtr = 456;
cout << a << endl; // 456 is printed

Of course in order for this to work you need to ensure that the constant 0x457FB indeed represents a valid address available for reading and writing by your program.

answered Jun 08 '13 at 02:10

Sergey Kalinichenko

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Wow. Thank you! I was almost sure that it would be impossible. – user2465415 Jun 08 '13 at 02:13
You are welcome! In case you'd like to learn more about C++ references, [Wikipedia has an article on them](http://en.wikipedia.org/wiki/Reference_(C%2B%2B)). – Sergey Kalinichenko Jun 08 '13 at 02:15
One more question. I get how `int& a = *aPtr;` works but how does `int &a(*aPtr);` work? You're using brackets on a primitive declaration? – user2465415 Jun 08 '13 at 02:25
@user2465415 It's the same thing. I prefer the syntax with parentheses because it is easier to distinguish it from assignments. – Sergey Kalinichenko Jun 08 '13 at 02:36

score 1 · Answer 2 · edited May 23 '17 at 11:57

As dasblinkenlight said you can use references to accomplish what you desire. I would add one things to this, since we are using C++ you should prefer reinterpret_cast over C style casts since you are being explicit about your intention and they are easier to find and stand out more, this previous thread goes into this in more detail. The code would look as follows:

int* exampleIntegerPtr = reinterpret_cast<int*>(0x457FB);
int &exampleInteger = *exampleIntegerPtr;

Is it possible to convert an integer pointer to the actual integer located at that memory location?

2 Answers2