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: Le Wang <l26wang <at> gmail.com>
Subject: bug#17379: closed (Re: bug#17379: 24.3.90.1 pretest: (ag-get-arg
 0) somehow returns nil in the middle of advice)
Date: Thu, 01 May 2014 03:55:05 +0000

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

Your bug report

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

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 17379 <at> debbugs.gnu.org.

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

[Message part 2 (message/rfc822, inline)]

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

[Message part 3 (message/rfc822, inline)]

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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