[Chicken-janitors] #1325: qt-light egg: timers may put chicken into an inconsistent state

[Chicken Trac]

#1325: qt-light egg: timers may put chicken into an inconsistent state
------------------------+--------------------------------
 Reporter:  retroj      |                 Owner:
     Type:  defect      |                Status:  new
 Priority:  major       |             Milestone:  someday
Component:  extensions  |               Version:  4.11.0
 Keywords:              |  Estimated difficulty:
------------------------+--------------------------------
 I have found that a Qt::Timer may be used to make callbacks into chicken
 faster than the callbacks themselves can finish.  This puts chicken into
 an inconsistent state and causes a crash.  Here is a test case - callback
 rate and count may need to be adjusted for faster machines.

 {{{
 (import chicken scheme)

 (use qt-light)

 (qt:init)

 (let* ((thread-rate 0.025)
        (timer (qt:timer thread-rate)))
   (define (timer-callback)
     (let loop ((i 0))
       (if (< i 1e6)
           (loop (+ i 1))
           #t)))
   (qt:connect timer "timeout()" timer-callback)
   (qt:start timer)
   (qt:run))
 }}}

 {{{
 $ ./minimal.scm

 Warning: excluded identifier doesn't exist in module foreign: foreign-
 declare

 Warning: excluded identifier doesn't exist in module foreign: foreign-
 declare
 csi: runtime.c:2797: C_save_and_reclaim: Assertion `av >
 C_temporary_stack_bottom || av < C_temporary_stack_limit' failed.
 Aborted
 }}}

 Since Qt must be used for the main event loop in a Qt program, making
 timers safe to use would be fairly important for the qt-light egg.
 Without knowing much about the internals, I think that maybe a semaphore
 could be used to block a callback if a previous callback has not finished.
 When this occurs, it would be nice if the api also exposed a way for a
 chicken program to know that a callback was dropped, so that it could take
 an appropriate action.

--
Ticket URL: <https://bugs.call-cc.org/ticket/1325>
CHICKEN Scheme <https://www.call-cc.org/>
CHICKEN Scheme is a compiler for the Scheme programming language.