//-------------------------------------------------------------------
//	tryclone.cpp
//
//	This program illustrates use of the Linux 'clone()' function
//	to create (1) a separate 'thread' executing within same task
//	address-space, and (2) another 'thread' that executes within
//	a copy of the original task's address-space.   
//
//	programmer: ALLAN CRUSE
//	written on: 26 SEP 2004
//-------------------------------------------------------------------

#include <stdio.h>	// for printf() 
#include <stdlib.h>	// for malloc() 
#include <unistd.h>	// for getpid() 
#include <sched.h>	// for clone() 
#include <sys/wait.h>	// for wait()

#define STACKSIZE 4096
#define FLAGS1 ( SIGCHLD | CLONE_VM )
#define FLAGS2 SIGCHLD

int mythread( void *data )
{
	int	*info = (int*)data;
	
	printf( "\nHello from thread (pid=%d)\n", getpid() );
	printf( "info=%d (initial)  ", info[0] );
	info[0] += 1;
	printf( "info=%d (final) \n", info[0] );
	return	0x12345678;
}


int main( int argc, char **argv )
{
	int	info = 0, status, retval;   // local variables
	
	// allocate memory for the thread's stack
	void 	*thread_stack = malloc( STACKSIZE );
	void	*tos = 	(void*)((int)thread_stack + STACKSIZE );

	// execute a separate thread within this same address-space
	retval = clone( mythread, tos, FLAGS1, &info );
	wait( &status );
	printf( "\nparent (pid=%d) reports retval=%d \n", getpid(), retval );
	printf( "status=%08X  info=%d \n", status, info );

	// execute another thread in a copy of this address-space
	retval = clone( mythread, tos, FLAGS2, &info );
	wait( &status );
	printf( "\nparent (pid=%d) reports retval=%d \n", getpid(), retval );
	printf( "status=%08X  info=%d \n", status, info );

	// release the allocated storage-area
	free( thread_stack );
}