Problem in memcpy using non-char data as parameters!

Question

Hi guyz,

The following program doesn't output desired data (on VC2008 compiler)

#include <stdio.h>
#include <string.h>

int main(void)
{
    int i;
    int dest[10] = {1};
    int src [] = {2, 3, 4, 5, 6};

    memcpy(dest, src, 5);
    for (i=0; i<10; i++) printf("%i\n", dest[i]);

    return 0;
}

whereas using char arrays instead, every thing goes fine! where is the problem here?

Answer 1

memcpy takes a number of bytes to copy - not a number of objects.

 memcpy(dest,src,5*sizeof(int))

Answer 2

Try memcpy(dest,scr,sizeof(int)*5)

Answer 3

memcpy copies bytes only. you need to tell it how many bytes to copy by multiplying the number of objects by the size of each object like so:

memcpy(dest, src, 5 * sizeof(int));

Answer 4

You need to add the sizeof(int):

#include <stdio.h>
#include <string.h>

int main(void)
{
    int i;
    int dest[10] = {1};
    int src [] = {2, 3, 4, 5, 6};

    memcpy(dest, src, sizeof(int) * 5);
    for (i=0; i<10; i++) printf("%i\n", dest[i]);

    return 0;
}

Answer 5

You want to call memcpy with a sizeof( x ) where "x" stands for the object. Here you'd do

memcpy( dest, src, 5*sizeof(int) );

Answer 6

Better is

memcpy( dest, src, 5*sizeof*src) );

If you change array-type to an other type, the code must not changed.