GNU bug report logs - #17379
24.3.90.1 pretest: (ag-get-arg 0) somehow returns nil in the middle of advice

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#17379: closed (24.3.90.1 pretest: (ag-get-arg 0) somehow
 returns nil in the middle of advice)
Date: Thu, 01 May 2014 03:55:03 +0000

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Your message dated Wed, 30 Apr 2014 23:54:48 -0400
with message-id <jwv61lqp386.fsf-monnier+emacsbugs <at> gnu.org>
and subject line Re: bug#17379: 24.3.90.1 pretest: (ag-get-arg 0) somehow returns nil in the middle of advice
has caused the debbugs.gnu.org bug report #17379,
regarding 24.3.90.1 pretest: (ag-get-arg 0) somehow returns nil in the middle of advice
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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17379: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=17379
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Le Wang <l26wang <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.90.1 pretest: (ag-get-arg 0) somehow returns nil in the middle
 of advice
Date: Wed, 30 Apr 2014 22:58:41 -0400

Ok the repro steps are very specific.  I've tried to make a simpler
repro, but could not with the time I had.

The important 2 line of code is here:

https://github.com/lewang/flx/blob/test-bug-report/flx-ido.el#L226-227

The advice around it is very basic.  The only interesting thing is

after

      (setq test (ad-get-arg 0))

test is nil, but original-items is correct.

-----------------------------------------------------

Repro steps

1. clone git <at> github.com:lewang/flx.git
2. switch to branch "test-bug-report"
3. open "flx-ido.el"
4. follow installation instructions: in header
https://github.com/lewang/flx/blob/test-bug-report/flx-ido.el#L48-54
5. press "C-x b"
6. Look at "*Messages*" buffer.

The advice isn't complicated I have no idea what's going on there.


-- 
Le

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Le Wang <l26wang <at> gmail.com>
Cc: 17379-done <at> debbugs.gnu.org
Subject: Re: bug#17379: 24.3.90.1 pretest: (ag-get-arg 0) somehow returns nil
 in the middle of advice
Date: Wed, 30 Apr 2014 23:54:48 -0400

tags 17379 wontfix
thanks

> Ok the repro steps are very specific.  I've tried to make a simpler
> repro, but could not with the time I had.
> The important 2 line of code is here:
> https://github.com/lewang/flx/blob/test-bug-report/flx-ido.el#L226-227
> The advice around it is very basic.  The only interesting thing is
> after (setq test (ad-get-arg 0))
> test is nil, but original-items is correct.

The arglist of ido-set-matches-1 is (items &optional do-full), so
(ad-get-arg 0) is `items', which you have rebound to nil.

AFAICT, this bug is very old.  And, AFAICT, you can't fix it without
breaking backward compatibility.  The new advice mechanism in 24.4
(i.e. advice-add) does not suffer from these problems, tho.


        Stefan

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