GNU bug report logs - #19438
24.4; system-name bad cache

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Leo Liu <sdl.web <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.4; system-name bad cache
Date: Thu, 25 Dec 2014 18:21:31 +0800

I just moved from one network to another and find that my long running
Emacs no longer has the right value for (system-name).

I am seeing this: (system-name) => Leos-MacBook.local

but a freshly-started emacs gives me: 014136144036.static.ctinets.com

It turns out system name is not computed dynamically. Could someone fix
this problem? Thanks.

Leo

Message #8 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Leo Liu <sdl.web <at> gmail.com>
Cc: 19438 <at> debbugs.gnu.org
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Thu, 25 Dec 2014 22:57:13 -0500

> I am seeing this: (system-name) => Leos-MacBook.local
> but a freshly-started emacs gives me: 014136144036.static.ctinets.com

AFAIK neither of those two names correspond to the intended meaning of
`system-name', which should be "the name of machine" (something that
ideally won't change until the machine is retired or at most
re-purposed), rather than "some DNS name you can use to access the
machine".


        Stefan

Message #11 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Cc: 19438 <at> debbugs.gnu.org, Leo Liu <sdl.web <at> gmail.com>
Subject: Re: 24.4; system-name bad cache
Date: Fri, 26 Dec 2014 08:07:55 -0800

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

Unfortunately even "the name of the machine" can change; e.g., I can invoke the 
shell command "hostname garfield" to change my machine's name to garfield. 
Also, I expect that if Emacs has its process migrated (LinuxPMI, anybody?) it 
will then be running on a different machine with a different name.

How about the attached patch?  The idea is that (system-name) actually inquires 
for the current system name, and system-name caches the result.  If an Emacs 
lisp program assigns to system-name, though, it's no longer updated thereafter.

[0001-system-name-s-returned-value-can-vary.patch (text/x-diff, attachment)]

Message #14 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Leo Liu <sdl.web <at> gmail.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 19438 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Sat, 27 Dec 2014 09:10:57 +1100

On 2014-12-27 03:07 +1100, Paul Eggert wrote:
> How about the attached patch?  The idea is that (system-name) actually
> inquires for the current system name, and system-name caches the
> result.  If an Emacs lisp program assigns to system-name, though, it's
> no longer updated thereafter.

Why not get rid of the variable system-name? It seems what it provides
can be easily achieved without it. Thanks for looking into the issue.

Leo

Message #17 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Leo Liu <sdl.web <at> gmail.com>
Cc: 19438 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Fri, 26 Dec 2014 14:16:48 -0800

Leo Liu wrote:
> Why not get rid of the variable system-name? It seems what it provides
> can be easily achieved without it.

It's documented so we shouldn't just remove it; we'd need to mark it as obsolescent.

Its documented behavior is "you can set the variable @code{system-name} in case 
Emacs is confused about the name of your system".  I've never found this feature 
to be useful, though I understand it was useful for others long ago.  Perhaps 
some people still find it useful?  Anyway, if there's consensus to mark the 
variable as obsolescent I can prepare a patch along those lines.

Message #20 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 19438 <at> debbugs.gnu.org, Leo Liu <sdl.web <at> gmail.com>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Sat, 27 Dec 2014 10:13:43 -0500

>> Why not get rid of the variable system-name?  It seems what it provides
>> can be easily achieved without it.
> It's documented so we shouldn't just remove it; we'd need to mark it
> as obsolescent.
> Its documented behavior is "you can set the variable @code{system-name} in
> case Emacs is confused about the name of your system".  I've never found
> this feature to be useful, though I understand it was useful for others long
> ago.  Perhaps some people still find it useful?  Anyway, if there's
> consensus to mark the variable as obsolescent I can prepare a patch along
> those lines.

Maybe we could mark it obsolete, tho I'm not completely sure what
replaces it.  Random thoughts:
- "it" is unclear, since currently the var and the function are just identical.
- this not-very-useful functionality occasionally causes 30s wait at
  startup time, so it would be good to get rid of the DNS lookup.

Maybe we could make the system-name function return the same as
`hostname` (and do it dynamically).

> How about the attached patch?  The idea is that (system-name) actually
> inquires for the current system name, and system-name caches the result.
> If an Emacs lisp program assigns to system-name, though, it's no longer
> updated thereafter.

Sounds OK.


        Stefan

Message #23 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Leo Liu <sdl.web <at> gmail.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 19438 <at> debbugs.gnu.org, Paul Eggert <eggert <at> cs.ucla.edu>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Sun, 28 Dec 2014 10:30:33 +1100

On 2014-12-28 02:13 +1100, Stefan Monnier wrote:
> Maybe we could mark it obsolete, tho I'm not completely sure what
> replaces it.  Random thoughts:
> - "it" is unclear, since currently the var and the function are just identical.
> - this not-very-useful functionality occasionally causes 30s wait at
>   startup time, so it would be good to get rid of the DNS lookup.

I am mostly against having a variable and a function for a simple small
feature. Such feature should be straightforward to use with either the
variable or the function public. With Paul's change it only makes sense
to use (system-name), the variable system-name just provides a way to
override it. Worst comes to worst, they can advise it.

Leo

Message #26 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Leo Liu <sdl.web <at> gmail.com>
Cc: 19438 <at> debbugs.gnu.org, Paul Eggert <eggert <at> cs.ucla.edu>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Sat, 27 Dec 2014 20:11:33 -0500

> variable or the function public. With Paul's change it only makes sense
> to use (system-name), the variable system-name just provides a way to
> override it. Worst comes to worst, they can advise it.

That's right.  But we have to take backward compatibility into account.


        Stefan

Message #29 received at 19438 <at> debbugs.gnu.org (full text, mbox):

From: Leo Liu <sdl.web <at> gmail.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: "19438 <at> debbugs.gnu.org" <19438 <at> debbugs.gnu.org>,
 Paul Eggert <eggert <at> cs.ucla.edu>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Sun, 28 Dec 2014 13:03:38 +1100

> On 2014年12月28日, at 12:11, Stefan Monnier <monnier <at> iro.umontreal.ca> wrote:
> 
> That's right.  But we have to take backward compatibility into account.

Agreed. I meant to say phase out:)

Leo

Message #34 received at 19438-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 19438-done <at> debbugs.gnu.org, Leo Liu <sdl.web <at> gmail.com>
Subject: Re: bug#19438: 24.4; system-name bad cache
Date: Mon, 29 Dec 2014 12:47:16 -0800

Stefan Monnier wrote:
> Maybe we could make the system-name function return the same as
> `hostname` (and do it dynamically).

OK, thanks, I revised the patch to do that, and made the var obsolete, and 
installed something along those lines into the master.  (It was 3 patches not 
one because I installed the wrong version first, sorry.)  Marking this as done.

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