GNU bug report logs - #33839
26.1.90; Emacs occasionally fails to receive asynchronous subprocess output in batch mode

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Philipp <p.stephani2 <at> gmail.com>
Subject: bug#33839: closed (26.1.90; Emacs occasionally fails to receive
 asynchronous subprocess output in batch mode)
Date: Thu, 27 Dec 2018 21:08:02 +0000

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

Your bug report

#33839: 26.1.90; Emacs occasionally fails to receive asynchronous subprocess output in batch mode

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 33839 <at> debbugs.gnu.org.

-- 
33839: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=33839
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Philipp <p.stephani2 <at> gmail.com>
Cc: 33839-done <at> debbugs.gnu.org
Subject: 26.1.90; Emacs occasionally fails to receive asynchronous subprocess
 output in batch mode
Date: Thu, 27 Dec 2018 13:06:54 -0800

[Message part 3 (text/plain, inline)]

[This is a corrected version of email I mistakenly sent elsewhere.]

> I don't think the manual states that output can
> arrive after the process has finished, but if that's the case, then it
> should do so.

Good point, and I installed the attached patch into emacs-26 to try to do that.

As this bug report seems to stem from a misunderstanding of 
accept-process-output (quite understandable, as its functionality is obscure) 
I'm taking the liberty of closing the report. If I'm wrong please feel free to 
reopen it.

[0001-Improve-accept-process-process-doc.patch (text/x-patch, attachment)]

[Message part 5 (message/rfc822, inline)]

From: Philipp <p.stephani2 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.1.90;
 Emacs occasionally fails to receive asynchronous subprocess output in
 batch mode
Date: Sun, 23 Dec 2018 03:28:53 +0100

Add the following code to /tmp/form.el:

(require 'cl-lib)
(with-temp-buffer
  (let ((proc (make-process :name "test"
                            :command '("bash" "-c" "echo stdout; echo stderr >&2")
                            :buffer (current-buffer)
                            :connection-type 'pipe
                            :sentinel #'ignore
                            :noquery t
                            :coding '(utf-8-unix . utf-8-unix))))
    (when (process-live-p proc)
      (process-send-eof proc))
    (while (process-live-p proc)
      (accept-process-output proc))
    (cl-assert (equal (buffer-string) "stdout\nstderr\n") :show-args)))

Then evaluate this form repeatedly.  Occasionally the buffer is empty
and the assertion triggers.  For example:

$ for i in {1..100}; do emacs -Q -batch -l /tmp/form.el ; done
Assertion failed: (equal (buffer-string) "stdout
stderr
"), ""
Assertion failed: (equal (buffer-string) "stdout
stderr
"), ""

i.e. here the output didn't arrive in 2 of 100 iterations.


In GNU Emacs 26.1.90 (build 5, x86_64-apple-darwin18.0.0, NS appkit-1671.10 Version 10.14.1 (Build 18B75))
 of 2018-12-22
Repository revision: 24ddea074a2e61f7accde60cdf941ba67b1ce82a
Windowing system distributor 'Apple', version 10.3.1671
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --enable-checking --enable-check-lisp-object-type
 --enable-gtk-deprecation-warnings --with-modules --without-xml2
 --without-pop --with-mailutils --enable-gcc-warnings=warn-only
 MAKEINFO=/usr/local/opt/texinfo/bin/makeinfo 'CFLAGS=-O0 -ggdb3'
 LDFLAGS=-O0'

Configured features:
JPEG NOTIFY ACL GNUTLS ZLIB TOOLKIT_SCROLL_BARS NS MODULES THREADS LCMS2

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

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  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
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq dired
dired-loaddefs format-spec rfc822 mml easymenu mml-sec epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils phst pcase ffap
thingatpt url-parse auth-source cl-seq eieio byte-opt bytecomp
byte-compile cconv eieio-core cl-macs gv eieio-loaddefs password-cache
url-vars subr-x rx gnutls dbus xml cl-loaddefs cl-lib elec-pair
time-date 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 menu-bar rfn-eshadow isearch timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame 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 minibuffer 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 lcms2 multi-tty make-network-process
emacs)

Memory information:
((conses 16 216710 8580)
 (symbols 48 21650 0)
 (miscs 40 59 186)
 (strings 32 32914 1496)
 (string-bytes 1 892039)
 (vectors 16 37089)
 (vector-slots 8 751562 17790)
 (floats 8 56 60)
 (intervals 56 210 0)
 (buffers 992 11))

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