🚀 go-pugleaf

This question concerns the 4th parameter passed to _beginthread().
This is the void * that can point to anything the programmer wants
it to.

I have a function that loops and starts 'n' separate threads (pls see
example below).  In order to be safe, do I need to guarantee that the
memory pointed to by that pointer I pass is active and dedicated
exclusively to that thread for the thread's lifetime?  (Assuming I
don't *want* any interference from other threads.)

For example, I assume that the code below will not work properly because
the contents pointed to by &n may change before the newly started thread
can read it:


void _Optlink my_thread_func( void *args)
{
	int the_number_passed = * (int *) args;  /* ... */
}


void my_thread_starting_func()
{
	for( int n = 0; n < 4; n++)
		_beginthread( my_thread_func, 0, 32 * 1024, &n);
}


But how about if I change this to:

void my_thread_starting_func()
{
	int n[4];

	n[0] = 0; n[1] = 1; n[2] = 2; n[3] = 3;

	for( int i = 0; i < 4; i++)
		_beginthread( my_thread_func, 0, 32 * 1024, &n[i]);
}

What if 'my_thread_starting_func()' finishes before one or more of my
'my_thread_func()''s reads the value, and that stack area is already
overwritten by another function?

So, am I correct in assuming that in this situation I must absolutely
guarantee that this memory will be used exclusively by that thread
for as long as the thread might need it?  And therefore, that I should
probably use a static int array?

Thanks for your help.
- Keith
-- 
--------------------------------------------------------------------------
Keith Bennett                            Bennett Business Solutions, Inc.
C++/C Software Development               1852 Middlebridge Drive
kbennett@cpcug.org                       Silver Spring, MD USA 20906