Hello. I have a few questions:
1) Why do the docs say that racket_eval and racket_apply eval and apply in
the “initial” or “original” racket thread? I have verified that the thread
id returned from pthread_self when using racket_apply in c code called from
a racket place is different from the thread id of the thread i called
racket_boot on.
2) I noticed that if i racket_eval in c code called by a racket place, i
can’t evaluate things that would otherwise (in racket code) be available in
the place’s namespace. What is the correct way to get at things in the
place’s racket namespace from c code? Is my problem unique to using a
place, or would i have this problem in a non-place scenario as well?
3) (related to 2) I want to be able to put and get from a place channel
from a long-running c function. If i just pass a place channel to the
function, that is wrong because if i am correct in my thinking (and in what
i have witnessed) there is a chance that when i go to use that channel in
the future, it will have been moved by the garbage collector. Is there any
way to prevent a specific value from being garbage collected, at least for
the lifetime of my place? This is related to (2) because i actually don’t
need this functionality if i can just racket_eval to get at the place
channel from the namespace of the place’s module in the middle of a
Sactivate_thread / Sdeactivate_thread session.
3) Is there any way to pass a c callback function into racket so that
racket can call that function? I defined a ctype for the function, but i
couldn’t think of a way to cast a pointer value passed into racket from c
to an instance of my ctype (the `cast` function takes existing ctypes and
not numeric values). Is there any way to manually make a value for my
function ctype using an existing pointer value?
Regarding 2 and 3, i was able to solve the underlying problem behind those
questions by creating a module to stash the channel in and passing its
module path into c code, then importing it. I wonder if anyone has a better
solution? Previously, i was using the `place` function for brevity.
Here is what i did:
(module myplace racket/base
(provide place-main)
(require syntax/location)
(module stash racket/base
(provide client-channel)
(define client-channel (make-parameter #f)))
(require 'stash)
(define (place-main ch)
(client-channel ch)
(red_client_run_from_racket ch (quote-module-path stash))
(error "Should not get here")))
(define p (dynamic-place (quote-module-path myplace) 'place-main))
and in c code:
int red_client_run_from_racket(ptr ch, ptr path) {
...
racket_namespace_require(path);
...
}
Thank you
Nate
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