Re: Release/reacquire in T3

[James Firby <firby-james@YALE.ARPA>]

I've been writing some graphics stuff for the Apollos in T3 and was forced
to write the function supplied below to do the right thing when (error ...)
is called.  I haven't thought about what to do about GC yet.  Let me know
when you find out how *pre-gc-agenda* works.

The release/reacquire in the error function works just fine unless the process
is waiting on event input.  If something happens then (I'm guessing a GC
can't) one seems to be out of luck.  Also, the error function itself should
be extended a little deeper (or augmented with another) to handle T VM faults.
It doesn't do the right thing when one occurs.

Good luck with this code.

Jim

; ------------------------------------------------------------------------------
;
; Written by: R. James Firby
;
; ------------------------------------------------------------------------------
; ** Patch to the T System so that errors don't kill the GPR System
; -----------------------------------------------------------------
;
; (1) Create a new error that doesn't choke when GPR running
; (2) Make the new error available in all the usual places
;
; This could be a lot more robust but should be fine for most users.

(set (*value t-implementation-env 'error)
     (let ( (error-old (*value t-implementation-env 'error)) )
        (lambda stuff
           (receive (count okay)
                    (gpr_$force_release nil nil)
              (ignore okay)
              (unwind-protect
                 (apply error-old stuff)
                 (do ( (count count (fx- count 1)) )
                       ((fx<= count 0) T)
                    (gpr_$acquire_display nil)))))))

(import t-implementation-env error)


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