how to print pointer in C++ with loop

Question

I want to print pointer value after get the address from function return processing but, when i try to print 1 by 1 the program is fine ... but when i try to use loop, something happen ..

heres my code :

    int *fibo(int input){
        int a=0,b=0,fib=1;
        int arrfibo[input];
        int *arrfib;

        for(int i=0;i<input;i++){
            a = b;
            b = fib;
            arrfibo[i] = fib;
            fib = a + b;
        }

        arrfib = arrfibo;

        cout << arrfib << endl;

        return arrfib;
    }

    main(){
        int inp;
        cout << "Enter number of fibonancci = ";
        cin >> inp;
        int *arr;

        arr = fibo(inp);


        for(int i=0;i<inp;i++){
            cout << *(arr + i) << " ";
        } // something wrong here the result is (1 1 4462800 4663360 0)
    }

thanks, :)

you're returning a local variable address. Undefined behaviour when it goes out of scope. — Jean-François Fabre
– Jean-François Fabre ♦, Commented Nov 24, 2016 at 16:03
Maybe you are accessing a memory location which is't properly assigned, i.e, contains garbage value. — Ébe Isaac
– Ébe Isaac, Commented Nov 24, 2016 at 16:04
VLA's aren't standard c++. You should turn off gcc extensions for more portable code. — StoryTeller - Unslander Monica
– StoryTeller - Unslander Monica, Commented Nov 24, 2016 at 16:12

Jean-François Fabre · Accepted Answer · 2016-11-24 16:05:32Z

1

you're returning a local variable address. Undefined behaviour when it goes out of scope.

Instead, use new to create an array

 int *fibo(int input){
        int a=0,b=0,fib=1;
        int arrfibo = new int[input];   // <-- minimal line to change
        int *arrfib;   // <-- this is useless, you can directly return arrfibo

(of course you have to delete [] the array when not used anymore. An alternative is to use vector<int> to avoid all that new/delete problems)

answered Nov 24, 2016 at 16:05

Jean-François Fabre♦

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Comments

gbehar · Accepted Answer · 2016-11-24 16:07:20Z

0

This array was allocated on the stack in "fibo", when you are accessing it in main it was already released and you cannot access it

edited Nov 24, 2016 at 16:07

answered Nov 24, 2016 at 16:05

gbehar

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