GNU bug report logs -
#18116
24.3.92; url-http calls CALLBACK recursively with malformed CBARGS if the former calls `delete-process'
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Reported by: Dmitry <dgutov <at> yandex.ru>
Date: Sun, 27 Jul 2014 03:14:02 UTC
Severity: minor
Found in version 24.3.92
Fixed in version 24.3.93.4
Done: Dmitry Gutov <dgutov <at> yandex.ru>
Bug is archived. No further changes may be made.
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Your bug report
#18116: 24.3.92; url-http calls CALLBACK recursively with malformed CBARGS if the former calls `delete-process'
which was filed against the emacs package, has been closed.
The explanation is attached below, along with your original report.
If you require more details, please reply to 18116 <at> debbugs.gnu.org.
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18116: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18116
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Version: 24.3.93.4
On 09/12/2014 09:22 PM, Stefan Monnier wrote:
> I think there is indeed a change of behavior in that the sentinel used
> to be nil'd while running it.
> [ This was changed because it prevented the sentinel from modifying itself. ]
Okay, I guess.
>> To me, "When retrieval is completed, execute the function CALLBACK, using
>> the arguments listed in CBARGS." means that it will be called exactly with
>> the value of CBARGS passed to `url-http', whereas instead the list gets
>> prepended with stuff before it's passed to CALLBACK.
>
> Can you improve those docstrings, to avoid such confusion in the future?
Done, I think (r117511). Although maybe we should remove the middle
paragraph in `url-http' docstring and replace it with a reference to
`url-retrieve-internal': its second sentence has very much the same
contents, only using different words.
[Message part 3 (message/rfc822, inline)]
Note: this could be considered a regression from Emacs 24.3
With this test case:
```
(require 'url-http)
(defvar uht-counter 0)
(defun uht-callback (status)
(declare (special url-http-process))
(message "%s %s" uht-counter status)
(delete-process url-http-process))
(defun uht-test ()
(setq uht-counter (1+ uht-counter))
;; The port must not be open.
(url-http (url-generic-parse-url "http://localhost:3333") #'uht-callback (list 'foo)))
```
Evaluate `(uht-test)' and see two messages in the message log with the
same counter value. The second message outputs a different STATUS value,
caused by modification of `url-callback-arguments' in
`url-http-async-sentinel', like this:
4 (:error (error connection-failed failed with code 111
:host localhost :service 3333) . foo)
4 (:error (error connection-failed deleted
:host localhost :service 3333) :error (error connection-failed failed with code 111
:host localhost :service 3333) . foo)
If the callback expects STATUS to contain some specific data structure,
that can cause breakage, see https://github.com/marijnh/tern/issues/350
for an example.
Now, I'm not entirely sure the problem is in `url-http'. It does not
manifest in Emacs 24.3, possibly because in the current pretest, when
the connection fails, the `url-http-process' is still alive when
`delete-process' is called in `uht-callback'. This is not the case in
the current stable Emacs (wherein, as a consequence, `uht-callback'
doesn't get called the second time), so this could be a regression in
the processes subsystem.
In GNU Emacs 24.3.92.3 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.8)
of 2014-07-24 on axl
Repository revision: 117398 stephen.berman <at> gmx.net-20140722213204-51v7bp0chfei6wbx
Windowing system distributor `The X.Org Foundation', version 11.0.11501000
System Description: Ubuntu 14.04.1 LTS
This bug report was last modified 10 years and 327 days ago.
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