Member Avatar for StaticX

Hi i am wondering if its possible to do the following,say i have 2 integer pointers containing numbers,and i want to add them together to a third integer pointer,is this possible?

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Short answer: yes — you can add the integers that two int* point to, but you must operate on the pointed-to values and provide valid storage for the result. Several replies already point this out: started with the basics, explained dereferencing, demonstrated creating a target location, and was right to worry about unsafe pointer initialization.

Safe patterns and idioms (avoid repeating exact code snippets from the thread):

  • Return or store the sum as a normal int (preferred when ownership is simple).

  • Write a small helper that writes the sum into an output pointer, checking for nulls:

    void add_into(const int* a, const int* b, int* out) {
    if (!a || !b || !out) return;
    *out = *a + *b;
}

  • If you need a pointer that owns the result, allocate it explicitly and manage lifetime (avoid leaks):

    int* p3 = new int((p1 ? *p1 : 0) + (p2 ? *p2 : 0));
// ... use p3 ...
delete p3;

    Or better, use RAII/smart pointers:

    auto p3 = std::make_unique<int>((p1 ? *p1 : 0) + (p2 ? *p2 : 0));

Key pitfalls to avoid: never initialize a pointer with a literal integer address (e.g., int* p = 4); that makes the pointer point at an invalid address. Don’t try to add two pointer variables themselves — that’s a type mismatch and not meaningful for getting the sum of values. Always ensure the storage you point to has an appropriate lifetime, check for null pointers before dereferencing, and prefer returning values or using smart pointers in modern C++ for safety and clarity.

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Member Avatar for Narue

>is this possible?
Is this a troll? Or a bad joke? Of course it's possible, as are most things that noobs use the "is it possible?" question to ask about.

Member Avatar for mrnutty 
int a = 1;
int b = 2;
int *p1 = &a;
int *p2 = &b;
int *p3 = *p1 + *p2;
Member Avatar for JasonHippy

Yes it is possible.

If you've been having trouble trying to do this, I'm assuming you were doing something like this:

pResult = p1 + p2

Which is definitely not what you want to do. The compiler probably wouldn't allow it anyway, but what that code would attempt to do is add the memory addresses of p1 and p2 together and assign pResult to the resultant memory address...which could contain literally anything!

But as I've said you'd more likely just get a compiler error saying that the two pointers cannot be added together like that!

Assuming you have three int pointers correctly assigned to valid int variables; To add the values of two pointers together you'd do this:

*pResult = *p1 + *p2;

Which simply adds the values stored at p1 and p2 together and stores the resultant value at pResult.

Cheers for now,
Jas.

Member Avatar for StaticX

Thanks for the replies,is this because *p1 is derefrenced here so contents can be added?

Member Avatar for mrnutty

Thanks for the replies,is this because *p1 is derefrenced here so contents can be added?

Yep, just think about it like this, if ptr is a pointer-to-int, then *ptr,
is the value that it points to , so if it points to an address, which
has the value 4, then *ptr == 4 is true.

int a = 4;
int * p = &a;

int t = *p; // same effect  as int t = 4;
Edited by mrnutty because: n/a
Member Avatar for sadanand23

i have a doubt regarding this....

int *pa =4

is considered unsafe isn't it?? so how does

int *p3=*p1+*p2

work properly...
ty in advance

Member Avatar for necrolin

i have a doubt regarding this....

int *pa =4

is considered unsafe isn't it?? so how does

int *p3=*p1+*p2

work properly...
ty in advance

Well, I tried to get adding pointers to pointers working every which way I could and all but one ways resulted in a compile time failure.

int *p3 = *p1 + *p2; //Does NOT compile

In fact it spits out: error: invalid conversion from `int' to `int*'

The way I did get it to compile though is to do something like this:

#include <iostream>

using namespace std;

int main()
{
    int a = 1;
    int b = 2;
    int c;
    int *p1 = &a;
    int *p2 = &b;
    
    //Create the pointer and make it point to something
    int *p3 = &c;

    //Then assign the value of the pointers to the new pointer
    *p3 = *p1 + *p2;

    cout << *p3 << endl;

    return 0;
}

If there's some other way to do this then I'd love for someone to show me, but this is the only way that I could figure out on my own.

A pointer is supposed to point to a memory location. If you do something like: int* p3 = *p2 + *p1; then which memory location is it supposed to be pointing to? There is no memory location to point to in this example. So first, set up the pointer then add the values to the existing memory location.

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