Use void pointer to store float numbers into array

Question

I'm new to pointers and this may be a silly question. Not able to store float numbers into float array using void pointer. Below is the code and the output:

Code:

int main()
{
int size=5;
float f_array[size];
populate(f_array, size);
// printing array below
}
void populate(void *p, int size)
{
    int i;
    for(i=0; i<size; i++)
    {
        scanf("%f", (((float *)p)+i));
    }
}

Output:

//Entering five float numbers to be stored in array

1.2 // not able to enter other numbers and gives the below output

a[0] = 1
a[1] = garbage value
a[2] = garbage value
a[3] = garbage value
a[4] = 0

it works properly if you define void populate(void *p, int size) before the main, else compiler could assume int for all your parameters: if 64 bit compiler you're toast. — Jean-François Fabre
– Jean-François Fabre ♦, Commented Nov 13, 2017 at 20:50
minimal reproducible example please. We don't see how you're printing your values. My crystal ball tells me you're using %d format — Jean-François Fabre
– Jean-François Fabre ♦, Commented Nov 13, 2017 at 20:53
I am unable to reproduce your problem. Perhaps there is a problem with the print function that you did not include? — Christian Gibbons
– Christian Gibbons, Commented Nov 13, 2017 at 20:57
Code does not have any output code. Source of "a[0] = 1 a[1] = garbage value ..." is not re-viewable. — chux
– chux, Commented Nov 13, 2017 at 22:31

Elad Hazan · Accepted Answer · 2017-11-13 20:58:59Z

1

#include <stdio.h>
#define SIZE 5
void populate(void *p, int size)
{
    int i;
    float *array = (float*)p;
    for (i = 0; i < size; i++)
    {
        scanf("%f", &array[i]);
    }
}

int main()
{

    int i;
    float f_array[SIZE];
    populate(f_array, SIZE);
    //print array
}

answered Nov 13, 2017 at 20:58

Elad Hazan

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2 Comments

Sushmita Limkar Over a year ago

at line scanf("%f", &array[i]); - it is required to use pointers instead of array

Elad Hazan Over a year ago

float array = (float)p; this is casting to your pointer, and arrays are pointers as well...

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