Re: signal handling different in 1.8.3 than 1.8.1?

[Gregory Marton]

Aha!  So (sleep 0) did nothing, but interestingly (sleep 1) did -- but it 
didn't sleep 1!

So if I write this as
      (let ((sigcalled #f))
        (with-sigaction
        SIGALRM (lambda (sig) (set! sigcalled #t)) #f
        (lambda () (raise SIGALRM) (sleep 1)))
        (assert sigcalled "we set and handled an alarm"))
      (assert-equal orig (sigaction SIGALRM) "returned to the original state")
      (let ((outer "nop")
           (inner "nop"))
        (with-sigaction
           SIGALRM (lambda (sig) (set! outer "outer")) #f
           (lambda ()
             (with-sigaction
                 SIGALRM (lambda (sig) (set! inner "inner")) #f
                 (lambda ()
                   (raise SIGALRM) (sleep 1)))
             (raise SIGALRM) (sleep 1)))
        (and (assert-equal "inner" inner "inner sig got handled")
            (assert-equal "outer" outer "outer sig got handled")))
      (assert-equal orig (sigaction SIGALRM) "returned to the original state")

then it passes.  I thought it should never reach those sleeps -- what's 
going on?  Also, it effectively doesn't reach the sleeps: the program 
passes the tests very quickly.

Grem

On Tue, 3 Jun 2008, Ludovic Courtès wrote:

> The following message is a courtesy copy of an article
> that has been posted to gmane.lisp.guile.bugs as well.
>
> Hello,
>
> Gregory Marton <address@hidden> writes:
>
> > > The following message is a courtesy copy of an article
> > > that has been posted to gmane.lisp.guile.bugs as well.
> >
> > Is address@hidden now out of date?   I may have to get a
> > newsreader. Are they mirrored?
>
> No, address@hidden' is not outdated: it's just that I'm posting
> through Gmane (http://gmane.org/), which is a mail/news bi-directional
> gateway.  The above notice is issued (I think) by Gmane someone is
> explicitly Cc'd to a newsgroup post.
>
> > Nevertheless, it has consistently passed in 1.8.1 and consistently
> > fails in 1.8.3 with no other changes.
>
> Sure, but a quick glance at `NEWS' didn't reveal anything obviously
> related to the problem at hand.
>
> BTW, you might want to even switch to 1.8.5 while you're at it.
>
> > call-with-unblocked-asyncs complains:
> >     misc-error: asyncs already unblocked
>
> OK, so it's not needed.
>
> > With (sleep 0) is no different than without.
>
> I just tried and it depends on where you place it.  For instance, a
> `format' call (which also does `SCM_TICK' as a side effect) within the
> second lambda passed to `ensure' in `with-sigaction' does the trick.
>
> The key insight here is that signal delivery in Guile is asynchronous,
> so you can't know for sure when it will happen.  It'd be nice to be able
> to force system asyncs to run, though.
>
> As to why there's such a reproducible difference between 1.8.1 and
> 1.8.3, maybe you could try using `git-bisect' to find out which change
> set between tags `release_1-8-1' and `release_1-8-3' introduced the
> change in behavior.  I think it's probably a side-effect of some
> unrelated change but again, a valid side-effect.
>
> Hope this helps,
> Ludovic.

--
------ __@   Gregory A. Marton                http://csail.mit.edu/~gremio/
--- _`\<,_                                                                .
-- (*)/ (*)                  My religion . . . is kindness.
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