GNU bug report logs - #47535
27.2; comint shell hangs on long input

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

From: David Biesack <David.Biesack <at> Apiture.com>
To: "bug-gnu-emacs <at> gnu.org" <bug-gnu-emacs <at> gnu.org>
Subject: 27.2; comint shell hangs on long input
Date: Wed, 31 Mar 2021 22:11:18 +0000

Start Emacs with emacs -Q

M-x shell

in the shell buffer, enter

echo <C-u> 1 0 0 0 x <Return>

to echo 1,000 x's. Works fine.

echo <C-u> 1 0 2 4 x <Return>

to echo 1,024 x's. The shell buffer prints the command, then "hangs" and
the output is never printed, and the command prompt not issued. no
character input works (Return, etc.)

A ^G character does show up for some reason, although I did not press Ctrl-G.
If

You must use C-c C-c comint-interrupt-subjob to get back to the shell prompt.

In GNU Emacs 27.2 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 Version 10.14.6 (Build 18G95))
 of 2021-03-27 built on builder10-14.porkrind.org
Windowing system distributor 'Apple', version 10.3.1894
System Description:  Mac OS X 10.15.7

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'

Configured features:
NOTIFY KQUEUE ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES
THREADS JSON PDUMPER GMP

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs text-property-search seq
byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date subr-x
cl-loaddefs cl-lib tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/ns-win ns-win ucs-normalize mule-util
term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads kqueue cocoa ns multi-tty make-network-process emacs)

Memory information:
((conses 16 45079 7412)
 (symbols 48 5929 1)
 (strings 32 15297 2156)
 (string-bytes 1 507876)
 (vectors 16 10216)
 (vector-slots 8 127221 7646)
 (floats 8 19 52)
 (intervals 56 190 0)
 (buffers 1000 13))


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

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: David Biesack via "Bug reports for GNU Emacs, the Swiss army knife of
 text editors" <bug-gnu-emacs <at> gnu.org>
Cc: David Biesack <David.Biesack <at> Apiture.com>, 47535 <at> debbugs.gnu.org
Subject: Re: bug#47535: 27.2; comint shell hangs on long input
Date: Thu, 01 Apr 2021 10:04:05 +0200

On Mär 31 2021, David Biesack via "Bug reports for GNU Emacs, the Swiss army knife of text editors" wrote:

> Start Emacs with emacs -Q
>
> M-x shell
>
> in the shell buffer, enter
>
> echo <C-u> 1 0 0 0 x <Return>
>
> to echo 1,000 x's. Works fine.
>
> echo <C-u> 1 0 2 4 x <Return>
>
> to echo 1,024 x's. The shell buffer prints the command, then "hangs" and
> the output is never printed, and the command prompt not issued. no
> character input works (Return, etc.)

That's a limitation of the BSD tty interface.  Once the input buffer is
full, no more characters can be sent, not even a newline or the EOF
character.  The Linux tty interface instead discards further input until
the newline or EOF.

Andreas.

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Message #14 received at 47535 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Andreas Schwab <schwab <at> linux-m68k.org>
Cc: David.Biesack <at> Apiture.com, 47535 <at> debbugs.gnu.org
Subject: Re: bug#47535: 27.2; comint shell hangs on long input
Date: Sat, 08 May 2021 13:52:16 +0200

Andreas Schwab <schwab <at> linux-m68k.org> writes:

> That's a limitation of the BSD tty interface.  Once the input buffer is
> full, no more characters can be sent, not even a newline or the EOF
> character. 

Is this something that can be fixed in Emacs, then?

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

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