How to pass a pointer to array in a function, modify it, and return back properly?

Question

I am attempting to pass a pointer to array in a function and return it back. The problem is that after correct initializing the function returns a NULL-pointer. Can anyone tell me, what is the issue with my logic?

Here is my function, where array is declared:

void main()
{
     int errCode;
     float *pol1, *pol2;
     pol1 = pol2 = NULL;
     errCode = inputPol("A", pol1);
     if (errCode != 0)
     { 
         return;
     }

     // using pol1 array

     c = getchar();
}

And here is the function with initialization:

int inputPol(char* c, float *pol)
{
    pol= (float *) calloc(13, sizeof( float ) );
    while( TRUE )
    {
         // While smth happens
         pol[i] = 42;
         i++;
    };
}

You need to turn up your compiler warning level (or pay attention to your warnings) so you don't write non-void functions without return statements. :-/ — HostileFork says dont trust SE
– HostileFork says dont trust SE, Commented Nov 24, 2012 at 11:31
Is the code that you are posting the complete code you are running? I see and infinite loop in the inputPol function and you are not returning the error code. — Hernan Velasquez
– Hernan Velasquez, Commented Nov 24, 2012 at 11:31

Daniel Rose · Accepted Answer · 2012-11-24 11:29:59Z

5

You need to pass the address of pol1, so main knows where the allocated memory is:

void main()
{
    int errCode;
    float *pol1, *pol2;
    pol1 = pol2 = NULL;
    errCode = inputPol("A", &pol1);
    if (errCode != 0)
    { 
         return;
    }

    // using pol1 array

    c = getchar();
}

int inputPol(char* c, float **pol)
{
    *pol= (float *) calloc(13, sizeof( float ) );
    while( TRUE )
    {
         // While smth happens
         (*pol)[i] = 42;
         i++;
    };
}

answered Nov 24, 2012 at 11:29

Daniel Rose

17.7k9 gold badges72 silver badges94 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to pass a pointer to array in a function, modify it, and return back properly?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related