A "clone" doubt

[prafu]

include<stdio.h>
#include<sched.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
int fn(void *a)
{
        int *p;
        printf("Value of a is = %d",*p);
        printf("\n");
        return 0;
}
int main()
{
        int *i,a=125;
        pid_t child;
        printf("\n This is parent with id : %d",getppid());
        i=(int*)malloc(100*sizeof(int))+100;
        child=clone(&fn,i,CLONE_PARENT,&a);
        printf("\n Got the child id as : %d",child);
        return 0;
}

In the above program, In function "fun()" the first printf statement (i.e, printing the value of a) is not printing anything in the screen. If i give the second printf(simply a new line) i'm getting the output.

1. can anyone explain me why?

2. My friends are telling that I should not use "printf", if I create a process by using "clone()". They are telling me to use "write()" instead.
If they are telling the correct answer, also explain me why I should not use printf in clone?