GNU bug report logs - #54245
29.0.50; select usage in GNUstep

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

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.0.50; select usage in GNUstep
Date: Fri, 04 Mar 2022 16:30:38 +0100

Paul noted in bug#32452 that:

---
I notice that Emacs's GNUstep code calls 'select'. For completeness this 
should be 'pselect' instead, so that Emacs never calls 'select'.
---

So that should be fixed.  (I open a new bug report, because that bug
report was already way too long.)


In GNU Emacs 29.0.50 (build 7, x86_64-pc-linux-gnu, GTK+ Version 3.24.31, cairo version 1.16.0)
 of 2022-02-25 built on giant
Repository revision: ca3858563c7ba8ee3caa82fbd2b7c386ea60c0d3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Debian GNU/Linux bookworm/sid


-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #8 received at 54245 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: 54245 <at> debbugs.gnu.org
Cc: Alan Third <alan <at> idiocy.org>
Subject: Re: bug#54245: 29.0.50; select usage in GNUstep
Date: Fri, 04 Mar 2022 17:10:00 +0100

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> Paul noted in bug#32452 that:
>
> ---
> I notice that Emacs's GNUstep code calls 'select'. For completeness this 
> should be 'pselect' instead, so that Emacs never calls 'select'.
> ---

I guess it's this code:

- (void)fd_handler:(id)unused
/* --------------------------------------------------------------------------
     Check data waiting on file descriptors and terminate if so.
   -------------------------------------------------------------------------- */
{
[...]
          result = select (selfds[0]+1, &fds, NULL, NULL, NULL);
          if (result > 0 && read (selfds[0], &c, 1) == 1 && c == 'g')
	    waiting = 0;

nsterm.m uses pselect throughout otherwise, so I guess changing this to
pselect should be unproblematic, too?  Perhaps Alan has some comments;
added to the CCs.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #15 received at 54245 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 54245 <at> debbugs.gnu.org
Subject: Re: bug#54245: 29.0.50; select usage in GNUstep
Date: Fri, 04 Mar 2022 17:15:27 +0100

>>>>> On Fri, 04 Mar 2022 16:30:38 +0100, Lars Ingebrigtsen <larsi <at> gnus.org> said:

    Lars> Paul noted in bug#32452 that:

    Lars> ---
    Lars> I notice that Emacs's GNUstep code calls 'select'. For completeness this 
    Lars> should be 'pselect' instead, so that Emacs never calls 'select'.
    Lars> ---

    Lars> So that should be fixed.  (I open a new bug report, because that bug
    Lars> report was already way too long.)

Iʼve been running with the following for a whole two days with no ill
effects (and the resulting emacs binary does not contain any calls to
'select'). Last time I looked, emacs never seems to use the sigmask
parameter to 'pselect' anyway, so itʼs kind of a moot point.

diff --git a/src/nsterm.m b/src/nsterm.m
index 670f8971df..4eb32de654 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -5830,7 +5830,7 @@ - (void)fd_handler:(id)unused
           fd_set fds;
           FD_ZERO (&fds);
           FD_SET (selfds[0], &fds);
-          result = select (selfds[0]+1, &fds, NULL, NULL, NULL);
+          result = pselect (selfds[0]+1, &fds, NULL, NULL, NULL, NULL);
           if (result > 0 && read (selfds[0], &c, 1) == 1 && c == 'g')
 	    waiting = 0;
         }

Robert
-- 

Message #18 received at 54245 <at> debbugs.gnu.org (full text, mbox):

From: Po Lu <luangruo <at> yahoo.com>
To: Robert Pluim <rpluim <at> gmail.com>
Cc: Lars Ingebrigtsen <larsi <at> gnus.org>, 54245 <at> debbugs.gnu.org
Subject: Re: bug#54245: 29.0.50; select usage in GNUstep
Date: Sat, 05 Mar 2022 08:45:03 +0800

Robert Pluim <rpluim <at> gmail.com> writes:

> Iʼve been running with the following for a whole two days with no ill
> effects (and the resulting emacs binary does not contain any calls to
> 'select'). Last time I looked, emacs never seems to use the sigmask
> parameter to 'pselect' anyway, so itʼs kind of a moot point.
>
> diff --git a/src/nsterm.m b/src/nsterm.m
> index 670f8971df..4eb32de654 100644
> --- a/src/nsterm.m
> +++ b/src/nsterm.m
> @@ -5830,7 +5830,7 @@ - (void)fd_handler:(id)unused
>            fd_set fds;
>            FD_ZERO (&fds);
>            FD_SET (selfds[0], &fds);
> -          result = select (selfds[0]+1, &fds, NULL, NULL, NULL);
> +          result = pselect (selfds[0]+1, &fds, NULL, NULL, NULL, NULL);
>            if (result > 0 && read (selfds[0], &c, 1) == 1 && c == 'g')
>  	    waiting = 0;
>          }
>
> Robert

That LGTM, but I only tested on GNUstep.  The same code is also used on
macOS, so there might be some side effects.

Though the NS port is very old and I get the feeling that we keep
bumping into relics from over two decades ago, and using `select' might
very well be one of those.

Thanks.

Message #21 received at 54245 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: Po Lu <luangruo <at> yahoo.com>
Cc: Lars Ingebrigtsen <larsi <at> gnus.org>, 54245 <at> debbugs.gnu.org
Subject: Re: bug#54245: 29.0.50; select usage in GNUstep
Date: Sat, 05 Mar 2022 12:32:18 +0100

>>>>> On Sat, 05 Mar 2022 08:45:03 +0800, Po Lu <luangruo <at> yahoo.com> said:

    Po> That LGTM, but I only tested on GNUstep.  The same code is also used on
    Po> macOS, so there might be some side effects.

Iʼm on macOS

    Po> Though the NS port is very old and I get the feeling that we keep
    Po> bumping into relics from over two decades ago, and using `select' might
    Po> very well be one of those.

Every platform has a replacement for `select', but theyʼre all
different. The only real issue I see with (p)select is that you canʼt
wait on more than FD_SETSIZE descriptors.

Robert
-- 

Message #24 received at 54245 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Robert Pluim <rpluim <at> gmail.com>
Cc: Po Lu <luangruo <at> yahoo.com>, 54245 <at> debbugs.gnu.org
Subject: Re: bug#54245: 29.0.50; select usage in GNUstep
Date: Sat, 05 Mar 2022 20:00:50 +0100

Robert Pluim <rpluim <at> gmail.com> writes:

>     Po> That LGTM, but I only tested on GNUstep.  The same code is also used on
>     Po> macOS, so there might be some side effects.
>
> Iʼm on macOS

Thanks; I've pushed Robert's patch to Emacs 29 now, and I'm therefore
closing this bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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