From: Sergei Organov <osv@javad.com>
To: help-gnu-emacs@gnu.org
Subject: Re: Problem advising nreverse.
Date: Mon, 14 Dec 2009 18:05:23 +0300 [thread overview]
Message-ID: <hg5k7n$1lu$1@ger.gmane.org> (raw)
In-Reply-To: 87bpi1n1z7.fsf@galatea.local
pjb@informatimago.com (Pascal J. Bourguignon) writes:
> Sergei Organov <osv@javad.com> writes:
>
>> pjb@informatimago.com (Pascal J. Bourguignon) writes:
>>> Sergei Organov <osv@javad.com> writes:
>>>
>>>> Hello,
>>>>
>>>> It seems that an advice set for `nreverse' function fails to be called
>>>> when `nreverse' is called from a byte compiled function:
>>
>> [...]
>>
>>>> Is it bug or feature? What's going on here?
>>>
>>> Indeed, it is a feature.
>>>
>>> Advices are not available from several call points:
>>>
>>> 1- when the advised function is called from C code.
>>>
>>> 2- when the advised function is a an opcode of the virtual machine.
>>> You can observe the difference between the two primitives nreverse
>>> and buffer-name for example, with:
>>>
>>> (disassemble (byte-compile (lambda (x) (nreverse x))))
>>> vs.:
>>> (disassemble (byte-compile (lambda (x) (buffer-name x))))
>>>
>>> In the former case, nreverse is a byte code, and therefore no
>>> advice applies. In the later case, buffer-name is called with the
>>> call byte code, which will go thru the advice.
>>>
>>> Notice that if you really want to advice such a low level primitive
>>> function as nreverse, you can replace it with a lisp function (and
>>> recompile all the code that uses it).
>>
>> Thanks a lot for the explanations and suggestion.
>>
>> Unfortunately this is not an option as intention was to advise
>> `nreverse' during calls to a possibly buggy `ewoc-collect' function that
>> for a long time errorneously called `nreverse' at the end (fixed since
>> 2008).
>
> Redefining nreverse and reloading the ewoc-collect function would help
> as indicated...
Yeah, but:
1. I don't really want `nreverse' to be always redefined.
2. I don't know how to reload `ewoc-collect' (from elisp) provided it's
already byte-compiled.
Here what I've actually originally tried (that didn't work):
(defadvice ewoc-collect (around fix-ewoc-collect activate)
"Fix buggy `ewoc-collect' by reversing its result provided it
was altered by `nreverse'."
(let ((last-nreverse-result))
(unwind-protect
(progn
(defadvice nreverse (after notice-nreverse activate)
(setq last-nreverse-result ad-return-value))
ad-do-it)
(ad-unadvise 'nreverse))
(if (eq last-nreverse-result ad-return-value)
(setq ad-return-value (nreverse ad-return-value)))))
This starts to work as soon as I re-evaluate the (defun ewoc-collect
...) in the ewoc.el file after the above defadvice is evaluated and
continues to work even if I byte-compile the (defun ewoc-collect...)
after that (though I still don't understand why it works after
byte-compiling), but then it's both easier and cleaner to just re-define
ewoc-collect to a correct version.
-- Sergei.
next prev parent reply other threads:[~2009-12-14 15:05 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.12764.1260538816.2239.help-gnu-emacs@gnu.org>
2009-12-12 12:18 ` Problem advising nreverse Pascal J. Bourguignon
2009-12-14 11:07 ` Sergei Organov
[not found] ` <mailman.12932.1260788943.2239.help-gnu-emacs@gnu.org>
2009-12-14 13:01 ` Pascal J. Bourguignon
2009-12-14 15:05 ` Sergei Organov [this message]
2009-12-15 8:19 ` Kevin Rodgers
2009-12-15 12:02 ` Sergei Organov
[not found] ` <mailman.12940.1260803316.2239.help-gnu-emacs@gnu.org>
2009-12-14 15:23 ` Pascal J. Bourguignon
2009-12-14 16:01 ` Sergei Organov
[not found] ` <mailman.12941.1260806509.2239.help-gnu-emacs@gnu.org>
2009-12-14 17:56 ` Pascal J. Bourguignon
2009-12-14 19:59 ` Sergei Organov
[not found] ` <mailman.12952.1260820780.2239.help-gnu-emacs@gnu.org>
2009-12-15 1:47 ` Pascal J. Bourguignon
2009-12-15 12:06 ` Sergei Organov
[not found] ` <mailman.13009.1260879016.2239.help-gnu-emacs@gnu.org>
2009-12-15 19:54 ` Pascal J. Bourguignon
2009-12-15 20:38 ` Sergei Organov
[not found] ` <mailman.13027.1260909564.2239.help-gnu-emacs@gnu.org>
2009-12-15 21:12 ` Barry Margolin
2009-12-16 11:27 ` Sergei Organov
[not found] ` <mailman.13051.1260962896.2239.help-gnu-emacs@gnu.org>
2009-12-17 16:52 ` Barry Margolin
2009-12-11 13:22 Sergei Organov
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