Re: [Sbcl-devel] dynamic variables and threads

[<me...@ho...>]

On Wednesday 12 October 2005 15:58, Tim Daly Jr. wrote:
> I guess I don't quite understand the difference here.  Currently,
> each thread has its own binding for every special variable, right?

If the parent thread has a non-global binding then the child also gets a=20
binding that's a copy of the parent's (it's a different binding with=20
the same value).

(defparameter *x* 0)
(let ((*x* 1))
  (sb-thread:make-thread (lambda () (assert (=3D *x* 1)) (setq *x* 2)))
  (assert (=3D *x* 1)))

> And you are proposing that they share all bindings except for the
> ones listed in INITIAL-BINDINGS?

I realized after sending it that 'a more conventional design' is not the=20
most precise description.

I mean that they share no binding except the global binding:

(defparameter *x* 0)
(let ((*x* 1))
  (sb-thread:make-thread (lambda () (assert (=3D *x* 0)) (setq *x* 2)))
  (assert (=3D *x* 1)))

Not even the initial bindings are shared, the initial-bindings argument=20
is to make a thread perform bindings on startup as documented in:

http://www.franz.com/support/documentation/7.0/doc/multiprocessing.htm#dyna=
mic-environments-1

A way to establish a binding that's not global but shared between a=20
number of threads (a session?) might be useful, too.

>
> -Tim

Hopefully, I didn't butcher the terminology too badly.

G=E1bor