/*
 clone1.c++ Creation of new thread by clone() 
*/
#include <iostream>
using namespace std;
#include <stdio.h>
#include <sched.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>

#define MAXSTACK 4096

int fact ; // global data
int what(void *p) ;

int main() {  // clone1.c++
    int chPID, status, n ;	
    char *chStack ;

    cout << "Enter a +ve integer: " ;
    cin >> n;
    chStack = (char *) malloc(MAXSTACK);  
              // Memory for new stack
    chStack = chStack  + MAXSTACK;   
              // Stack grows towards lower
              // address. Bottom of stack 
   
   chPID = clone(what, chStack, CLONE_VM, (void *)&n) ; 
              // Cloned process will execute 
              // 'what(NULL)'. 
              // CLONE_VM - same memory space
              // &n is parameter to 'what'
              // chPID - cloned process id
   cout << "Inside proc: pid = " << getpid() << "\n" ;
   cout << "Inside proc: cpid = " << chPID << "\n" ;
   waitpid(chPID, &status, __WCLONE) ; 
              // __WCLONE - wait for 
              // cloned process
   cout << "Inside proc:" << n << "! = " << fact << "\n" ;
    
   return 0 ;
}

int what(void *p) {
    int n = *(int *)p, i;

    for(fact=i=1;i<=n;++i) fact *= i; 
    return 0 ;
}