Assigning value to int passed by reference stops program execution

Question

void assignVal(int *loopCount)
{
    //lots of stuff with print statements to know where func stop executing

    cout << "before assign resultCount" << endl;

    *loopCount = 3; //I want the loopSize int in the main function to be equal to 3;

    cout << "after assign resultCount" << endl;

    return;
}

int main() 
{
    int loopSize;

    assignVal(&loopSize);
    //Doesn't get here or below
    for(int i = 0; i < loopSize; i++)
    {
        cout << i << endl;
    }
}

I am trying to pass in the variable loopSize to be assigned inside the function assignVal(int*). I have no control over the main function, this is for hackerank (this is obviously not the code from the problem, i am just showing a heavily modified version of the small part that isn't working for me. I also have no control of the assignVal(int*) function signature. I need to receive this int*, change it within the function, and then just return. I don't know why this isn't working, this is how I would do it anywhere else. The cout "after assign resultCount" never gets printed, and the program stops executing there. I can confirm it IS compiling.

Edit: It should be noted that if I assign loopCount like this

int* arr = {3};
loopCount = arr;

The function continues to execute just fine, but the value outside the function is incorrect for some reason.

It seems something is wrong inside the "lots of stuff with print statements to know where func stop executing" — Pezzza, Apr 22 '19 at 01:25
[No repro](http://coliru.stacked-crooked.com/a/0da28ff938b782ec) — πάντα ῥεῖ, Apr 22 '19 at 01:25
@Pezzza There's not, i have print statements in there to see that everything is going smoothly. Even the value I am assigning to `loopCount` is what it should be, but as soon as I assign it, it stops. See Edit Also — user11392753, Apr 22 '19 at 01:27
That wouldn't really make sense, since `loopSize` is declared as `int` and it's used like `i < loopSize` — user11392753, Apr 22 '19 at 01:32
Test in a debugger, step by step. Does something change the pointer value? Does something delete it? Does something corrupt the stack/heap? — Fire Lancer, Apr 22 '19 at 01:32
@user11392753 can you send a link to the Hackerank problem ? — Pezzza, Apr 22 '19 at 01:33
@user11392753 Your edited `loopCount = arr` sets the pointer itself, it isn't setting the data being originally pointed to. — Fire Lancer, Apr 22 '19 at 01:33
right @FireLancer , I was just trying to add extra info, i know it won't work. What I am trying initially should be working I just don't know why it isn't. — user11392753, Apr 22 '19 at 01:35
You should still be able to make a runnable example of the problem. Did you change the pointer at all? If not possibly stack corruption. — Fire Lancer, Apr 22 '19 at 02:11

score 0 · Answer 1 · answered Apr 22 '19 at 07:09

It is not passed by reference, it is a pointer. Raw pointers need careful management to avoid problems. You can pass by reference like this:

void assignVal(int & loopCount)

You can read more here: What's the difference between passing by reference vs. passing by value?

Assigning value to int passed by reference stops program execution

1 Answers1