Subj : Re: regarding threads in VC++, for a beginnner
To   : comp.os.ms-windows.programmer.win32,comp.programming.threads
From : David Schwartz
Date : Tue Jan 25 2005 02:05 am


"Ian T" <nospam@spamdie.com> wrote in message 
news:41f61690$0$14721$afc38c87@news.optusnet.com.au...
> Scott McPhillips [MVP] wrote:

>> If "space" means memory space: all threads in a process use the same 
>> memory space.  If this were not so the void* thread parameter would be 
>> useless.
>
> Actually, sorry I was so imprecise. I was under the impression that each 
> thread has a stack and a "time slice".

    Yes and no about stacks.

    Since the stack is in the process' memory space, all threads share their 
staks in the sense that any thread could access any other thread's stack 
should it choose to do so. Each thread, however, has its own stack *pointer* 
which creates the illusion that the stack is local to the thread. However, a 
thread can legally pass another thread a pointer to a variable on its stack, 
so long as the other thread only uses that pointer while it remains valid.

    How threads are given CPU time can vary tremendoubly from operating 
system to operating system. Most allocate CPUs to threads that are avialable 
and pre-empt threads if a higher priority thread becomes ready to run. More 
than one thread may run at the same time on a machine with more than one 
logical CPU.

> Does the member function use the thread's stack and run in it's "time 
> slice"?

    The new thread is allocated a new stack and set up however is needed for 
it to be scheduled. It's instruction pointer points at the entry point to 
the function you passed and its stack pointer points to the stack just 
allocated for it. The thread is made 'ready to run' (or suspended for 
functions that require you to manually start the thread). The schedule will 
then allocate the thread a time slice and it will begin executing the 
function in the context of that new thread.

    DS

.