function returning array as an pointer

Question

I have tried to implement a simple function which returns the pointer to first element in array.

#include<iostream>
using namespace std;
int * func(int n)
{
    int arr[n];
    for (int a = 0; a <n; a++)
    {
        arr[a]=a;
    }
    return arr;
}
int main()
{
    int n;
    cin>>n;
    int * arr=func(n);
    for (int i = 0; i <n; i++)
    {
        cout<<*(arr+i)<<endl;
    }

 }

I have assumed that array occupies contiguous block of memory,then why the output of this program isn't what expected.

if n=10 then output is

0
-1216233191
-1215824576
-1215824576
-1215855028
-1215820256
-1074779464
-1215820256
-1074779464
134514382

score 2 · Accepted Answer · answered Nov 09 '14 at 14:19

2

int * func(int n)
{
    int arr[n];       <<<<<<<<<<<<<<<local variable to this function.
    for (int a = 0; a <n; a++)
    {
        arr[a]=a;
    }
    return arr;
}

You should not return address of local variables...

answered Nov 09 '14 at 14:19

ravi

10,994
1
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36

You can, it's just not advised. – Nov 09 '14 at 14:20
1

Oh yes, you can. The pit of hell is open for all comers. – Deduplicator Nov 09 '14 at 14:20
Corrected to avoid misinterpretation – ravi Nov 09 '14 at 14:21
The key expressions here are "can" and "should not". ;) – E_net4 Nov 09 '14 at 14:21
if it is not safe to do that than what is the use of any function like this int *func() and can you please also tell me if there is another way to accomplish the same thing i was trying to do. – arpit mishra Nov 09 '14 at 14:50
Yes you can create object on heap and return it... – ravi Nov 09 '14 at 15:22
then how we can use any function of type int *func() safely. it would be good if you give me a example. – arpit mishra Nov 09 '14 at 18:03
example would be:- int* func() { int* ptr = new int; return ptr; } – ravi Nov 09 '14 at 18:08
and isn't the ptr local variable or it remains in the memory and it will be there until we use delete??and also can you please tell me any source to learn c++ or how you learnt it? – arpit mishra Nov 09 '14 at 22:13

function returning array as an pointer

1 Answers1