$ wget -O - http://www.scs.stanford.edu/histar/src/pkg/uclibc/libc/stdlib/malloc-standard/realloc.c|grep memcpy
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int * a = malloc(5*sizeof *a);
a[1] = 1;
for ( int k=0; k < 5; k++)
printf("%i\n",a[k] == 1);
printf("%p\n",a);
a = realloc(a,100000*sizeof *a);
printf("%p\n",a);
for ( int k=0; k < 5; k++)
printf("%i\n",a[k] == 1);
}