[Sbcl-devel] dynamic variables and threads

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

Currently threads act like dynamic closures that capture _all_ dynamic=20
variables. This has a number issues:

1) dynamic-extent

Suppose your package has a non-exported special, binds it, promises it's=20
going to be dynamic extent and proceeds to call user code. The user=20
code spawns a thread and the promise is broken.

2) gc

It's hard to control giving out references to objects. Yeah, it's=20
similar to 1), but colour of the smoke is different.

3) scaling

When starting up, a thread is given a snapshot of the parent thread's=20
current values for dynamic variables. This means that the minimum=20
memory required by a thread is proportional to the number of specials.


AFAIK SBCL's approach is unique. In my current state of mind I can only=20
see the drawbacks and moving to a more conventional design is luring:

  make-thread (function &key name initial-bindings)

or maybe even

  make-thread (function &key name (initial-bindings *default-bindings*))

What do you think?

G=E1bor