[Chicken-janitors] #1638: Signal handling and parameters

[Chicken Trac]

#1638: Signal handling and parameters
---------------------------------------+--------------------------------
 Reporter:  mario                      |                 Owner:
     Type:  defect                     |                Status:  new
 Priority:  major                      |             Milestone:  someday
Component:  unknown                    |               Version:  5.1.0
 Keywords:  signals, parameters, load  |  Estimated difficulty:
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 I'm facing a difference in behavior between C4 and C5 regarding signal
 handling, parameters and load.

 The code below hopefully helps illustrate the problem.

 There's a loop printing the value of a parameter, and a signal handler
 that catches SIGHUP and loads a file which sets the parameter.

 Case 1: In C4, when the process catches SIGHUP and loads the configuration
 file, the value of the parameter changes.  In C5, the value doesn't
 change.

 Case 2: if we call {{{(load conf-file)}}} in the toplevel, both C4 and C5
 behave the same (expected behavior).

 The problem seems to be related to parameters.  I tried this code with a
 regular variable instead of a parameter (using {{{set!}}} to set it), and
 in that scenario the program behaves as expected.

 {{{
 $ cat hup.scm
 (cond-expand
  (chicken-4
   (use posix))
  (chicken-5
   (import
    (chicken base)
    (chicken process signal)
    (chicken process-context))))

 (define param (make-parameter 42))

 (define conf-file (car (command-line-arguments)))

 ; (load conf-file)

 (set-signal-handler!
  signal/hup
  (lambda (signum)
    (print "reloading conf file")
    (load conf-file)))

 (let loop ()
   (print (param))
   (sleep 1)
   (loop))


 $ cat conf.scm
 (param 4)


 ;;; Case 1: `(load conf-file)` in the toplevel commented out
 ;;; Steps:
 ;;;  1. run hup.scm
 ;;;  2. go to another terminal and kill it with signal 1

 $ ~/local/chicken-4.13.0/bin/csi -s hup.scm conf.scm
 42
 42
 42
 reloading conf file
 4
 4
 4

 $ ~/local/chicken-5.1.0/bin/csi -s hup.scm conf.scm
 42
 42
 42
 reloading conf file
 42
 42
 42


 ;;; Case 2: `(load conf-file)` in the toplevel uncommented.
 ;;; Notice that now the conf file is loaded in the toplevel and
 ;;; the configuration file contains `(param 4)'.
 ;;; Steps:
 ;;;  1. run hup.scm
 ;;;  2. go to another terminal change param in conf.scm (to 10)
 ;;;     and kill csi with signal 1
 $ ~/local/chicken-4.13.0/bin/csi -s hup.scm conf.scm
 4
 4
 4
 reloading conf file
 10
 10
 10

 ;;; Here the config file has the param set to 10 (previous execution)
 ;;; and I set it to 12 before sending signal 1 to csi.
 $ ~/local/chicken-5.1.0/bin/csi -s hup.scm conf.scm
 10
 10
 10
 reloading conf file
 12
 12
 12
 }}}

--
Ticket URL: <https://bugs.call-cc.org/ticket/1638>
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