Array returning issues with pointers

Asked Dec 11 '19 at 19:35

Active Dec 11 '19 at 19:35

Viewed 26 times

I know that I can return an array with pointers. But when try to make this in two functions like that;

    int* decToBin(int num){
    int binAr[100], i = 0;
    while(num != 0){
        binAr[i] = num % 2;
        num /= 2;
        i++;
    }
    binAr[i+1] = '\0';

    return binAr;
}

int modExp(int b, int e, int m){
    int* expoBin = decToBin(e);
    int i = 0;
    while(expoBin[i] != '\0'){
        printf("%d", expoBin[i]);
        i++;
    }

    return expoBin;

}

I cant get any output. I know that I'm missing a silly point but I can't figure out.

asked Dec 11 '19 at 19:35

Levent Kaya

1

There must be a duplicate Q for returning a pointer to a local variable... – Weather Vane Dec 11 '19 at 19:37
Perhaps [How to access a local variable from a different function using pointers?](https://stackoverflow.com/questions/4570366/how-to-access-a-local-variable-from-a-different-function-using-pointers) – Weather Vane Dec 11 '19 at 19:39
where? At the expoBin part? – Levent Kaya Dec 11 '19 at 19:40
`int binAr[100]` dies immediately after `return binAr;` it no longer exists although an unreliable ghost might linger for a while. – Weather Vane Dec 11 '19 at 19:40
So should I open memory with malloc function? – Levent Kaya Dec 11 '19 at 19:41
Yes, use `malloc` and `free` the memory later. – Weather Vane Dec 11 '19 at 19:42
It didnt fix ''' int *binAr = malloc(sizeof(int) * 100); ''' I used like that but the outpu is still the same – Levent Kaya Dec 11 '19 at 19:47
1

Well, if `expoBin[0]` is `0` then you won't "get any output". And if `num` is *even* then it will be `0`. – Weather Vane Dec 11 '19 at 19:57
Please update your code and provide a [minimal verifiable example](https://stackoverflow.com/help/minimal-reproducible-example). That is, provide a `main` and show the inputs the functions are being called with. – kaylum Dec 11 '19 at 19:57
Did you intend `binAr[i] = num % 2 + '0';` and a `char` array, followed by `printf("%c", expoBin[i])` ? – Weather Vane Dec 11 '19 at 19:58
well its worked but when i enter '2' the output is 0. But it should be 10 – Levent Kaya Dec 11 '19 at 20:03

Array returning issues with pointers

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