GNU bug report logs - #39811
Missing dynwind exit application

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Stefan Israelsson Tampe <stefan.itampe <at> gmail.com>
To: bug-guile <at> gnu.org
Subject: Missing dynwind exit application
Date: Thu, 27 Feb 2020 19:59:25 +0100

[Message part 1 (text/plain, inline)]

Executing this code on guile-3.0.0:

(dynamic-wind
 (lambda () (pk 'enter))
 (lambda () (catch #t
              (lambda () (throw 1))
              (lambda x (pk 'catch x) (apply throw x))))
 (lambda () (pk 'leave)))

Leads to the output:

scheme@(guile-user)> (load "bug.scm")
;;; (enter)
;;; (catch (a))

ice-9/boot-9.scm:1669:16: In procedure raise-exception:
Throw to key `a' with args `()'.

What, it does not execute the leave part of the dynamic wind.

This works however,

(catch #t
  (lambda ()
    (dynamic-wind
      (lambda () (pk 'enter))
      (lambda () (catch #t
                   (lambda () (throw 'a))
                   (lambda x (pk 'catch x) (apply throw x))))
      (lambda () (pk 'leave))))
  (lambda x #f))

So is this how it should be?

[Message part 2 (text/html, inline)]

Message #10 received at 39811-close <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> igalia.com>
To: Stefan Israelsson Tampe <stefan.itampe <at> gmail.com>
Cc: 39811-close <at> debbugs.gnu.org
Subject: Re: bug#39811: Missing dynwind exit application
Date: Tue, 03 Mar 2020 21:33:47 +0100

Stefan Israelsson Tampe <stefan.itampe <at> gmail.com> writes:

> Executing this code on guile-3.0.0:
>
> (dynamic-wind
>  (lambda () (pk 'enter))
>  (lambda () (catch #t
>               (lambda () (throw 1))
>               (lambda x (pk 'catch x) (apply throw x))))
>  (lambda () (pk 'leave)))
>
> Leads to the output:
>
> scheme@(guile-user)> (load "bug.scm") 
> ;;; (enter) 
> ;;; (catch (a)) 
>
> ice-9/boot-9.scm:1669:16: In procedure raise-exception: 
> Throw to key `a' with args `()'. 
>
> What, it does not execute the leave part of the dynamic wind.

That is because the REPL leaves you in the context of where the uncaught
error was thrown.  If you ,quit the REPL to go back to the outer REPL,
it will print "leave" as expected.  Please reopen if I have
misunderstood :)

Cheers,

Andy

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