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From: Maxim Cournoyer <>
To: Ricardo Wurmus <>
Subject: bug#60799: Bogus 'Error while printing exception' message when raising srfi-35 exception
Date: Sat, 14 Jan 2023 09:52:55 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (Ricardo Wurmus's message of "Sat, 14 Jan 2023 08:25:29 +0100")

Hello Ricardo,

Ricardo Wurmus <> writes:

> Hi Maxim,
>> When raising a srfi-35 defined exception type like in the following, a
>> generic (and unhelpful) "Error while printing exception" message is
>> shown, with not even the exception type mentioned:
>> (use-modules (srfi srfi-35))
>> (define-condition-type &platform-not-found-error &error
>>   platform-not-found-error?)
>> (raise-exception &platform-not-found-error)
>> Produces:
>> Backtrace:
>> In ice-9/boot-9.scm:
>>   1752:10  5 (with-exception-handler _ _ #:unwind? _ # _)
>> In unknown file:
>>            4 (apply-smob/0 #<thunk 7f236157a2e0>)
>> In ice-9/boot-9.scm:
>>     724:2  3 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
>> In ice-9/eval.scm:
>>     619:8  2 (_ #(#(#<directory (guile-user) 7f2361580c80>)))
>> In ice-9/boot-9.scm:
>>    2836:4  1 (save-module-excursion _)
>>   4388:12  0 (_)
>> ice-9/boot-9.scm:4388:12: Error while printing exception.
>> This is probably not by design, right?
> Perhaps not, but conditions are expected to be raised with “raise”:
> (use-modules (srfi srfi-34) (srfi srfi-35))
> (define-condition-type &platform-not-found-error &error
>   platform-not-found-error?)
> (raise (condition (&platform-not-found-error)))
> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
>   1. &platform-not-found-error

Thanks for pointing that.  The above with 'raise' doesn't produce the
same output for my Guile 3.0.8:

--8<---------------cut here---------------start------------->8---
(use-modules (srfi srfi-35))

(define-condition-type &platform-not-found-error &error

(raise (condition (&platform-not-found-error)))
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Wrong type (expecting exact integer): #<&platform-not-found-error>
--8<---------------cut here---------------end--------------->8---

Using 'raise-exception' instead of 'raise' fixes it for me:

--8<---------------cut here---------------start------------->8---
(raise-exception (condition (&platform-not-found-error)))
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
  1. &platform-not-found-error

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
--8<---------------cut here---------------end--------------->8---

So my initial issue was attempting to raise on a type rather than an
object (which works both ways in other languages such as Python).

If I also import srfi-34, then it works as expected:

--8<---------------cut here---------------start------------->8---
(use-modules (srfi srfi-34) (srfi srfi-35))

(define-condition-type &platform-not-found-error &error

(raise (condition (&platform-not-found-error)))
--8<---------------cut here---------------end--------------->8---

So my original confusing was that there exists a 'raise' procedure in
Guile, which has nothing to do with exceptions (it's used to send a
signal to the current process).

What I'll take from this is to use exclusively 'raise-exception', which
is not subject to the above srfi-34 vs builtin raise confusion.

Closing, thanks for helping me untangle things!


      reply	other threads:[~2023-01-14 14:52 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-14  1:30 bug#60799: Bogus 'Error while printing exception' message when raising srfi-35 exception Maxim Cournoyer
2023-01-14  7:25 ` Ricardo Wurmus
2023-01-14 14:52   ` Maxim Cournoyer [this message]

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