bug#29223: 26.0.90; [Regression][Emacs26] Problem in network stack

[Damien Cassou <damien@cassou.me>]

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The commit "Avoid unnecessary rounding errors in timestamps" (3aee7b)
introduces a regression in the network stack. This can be seen while
using org-caldav and I managed to reproduce with emacs -Q (see attached
files).

Among the attached files, script.el is of the most importance. The first
call to `contact-server' works fine whereas the second triggers a
server-side error: 503 Service Unavailable. Unfortunately, you can't
directly reuse this script as it depends on a personal nextcloud
instance.

Reverting the commit fixes the bug. I added its author on CC.

commit 3aee7be62eaf8caef6f2fab31bee79674b3abbb7
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Sun Oct 22 01:04:36 2017 -0700

    Avoid unnecessary rounding errors in timestamps
    
    Avoid the rounding errors of float-time when it’s easy.  E.g.,
    replace (< (float-time a) (float-time b)) with (time-less-p a b).
    * lisp/desktop.el (desktop-save):
    * lisp/ecomplete.el (ecomplete-add-item):
    * lisp/epg.el (epg-wait-for-completion):
    * lisp/files.el (dir-locals-find-file, dir-locals-read-from-dir):
    * lisp/image-dired.el (image-dired-get-thumbnail-image)
    (image-dired-create-thumb-1):
    * lisp/info.el (info-insert-file-contents):
    * lisp/ls-lisp.el (ls-lisp-format-time):
    * lisp/net/ange-ftp.el (ange-ftp-file-newer-than-file-p)
    (ange-ftp-verify-visited-file-modtime):
    * lisp/net/rcirc.el (rcirc-ctcp-sender-PING):
    * lisp/textmodes/remember.el (remember-store-in-mailbox):
    * lisp/url/url-cookie.el (url-cookie-expired-p):
    Bypass float-time to avoid rounding errors.
    
    * lisp/files.el (dir-locals-find-file):



In GNU Emacs 26.0.90 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.21)
 of 2017-11-09 built on luz4
Repository revision: b23adf48bfe03332f508f088265a0c8162747cae
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:	Fedora release 26 (Twenty Six)

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

Configured using:
 'configure --cache-file=/tmp/emacs.config.cache'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 LIBSYSTEMD LCMS2

Important settings:
  value of $LC_MONETARY: fr_FR.UTF-8
  value of $LC_NUMERIC: fr_FR.UTF-8
  value of $LC_TIME: fr_FR.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  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 byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache 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 elec-pair time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd 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 dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 94504 6564)
 (symbols 48 20339 1)
 (miscs 40 45 119)
 (strings 32 28291 1407)
 (string-bytes 1 748828)
 (vectors 16 13964)
 (vector-slots 8 492182 6318)
 (floats 8 49 68)
 (intervals 56 224 0)
 (buffers 992 12))

-- 
Damien Cassou
http://damiencassou.seasidehosting.st

"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill

[-- Attachment #2: bisect.log --]
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git bisect start
# good: [da62c1532e479bbac4ce242ee1d170df9c435591] Improve the documentation of filesets
git bisect good da62c1532e479bbac4ce242ee1d170df9c435591
# bad: [255ba01148f69f452937e67feb7af5d4c1466fed] Fix handling of nil PRED2 arg for completion-table-with-predicate
git bisect bad 255ba01148f69f452937e67feb7af5d4c1466fed
# good: [fd42a19260841a2e3c39fd983c7601a3f517bf4b] When opening new eww buffers, use buffer names based on the host name
git bisect good fd42a19260841a2e3c39fd983c7601a3f517bf4b
# good: [65b323e14e09fa6024fee93fd484deea4b7f51a2] Don't put deleted packages in the trash (bug#14967)
git bisect good 65b323e14e09fa6024fee93fd484deea4b7f51a2
# good: [bf0045d7a4cd4c7d4df3fa34b8a12795e8ee73aa] Avoid aborting in 'waitpid' on MS-Windows
git bisect good bf0045d7a4cd4c7d4df3fa34b8a12795e8ee73aa
# good: [1c30f9fc08649649676ed812f1579f0948558ceb] Flymake diagnostics now apply to arbitrary buffer regions
git bisect good 1c30f9fc08649649676ed812f1579f0948558ceb
# good: [dc8812829b81540d385eaa5577fa31397a8181d3] Remove resizable attribute on macOS undecorated frames (bug#28512)
git bisect good dc8812829b81540d385eaa5577fa31397a8181d3
# bad: [82a16c547bc32fda6073c97b6c8989b473f0315b] Fix some duplicate word typos
git bisect bad 82a16c547bc32fda6073c97b6c8989b473f0315b
# bad: [b51009d7f02b796bcdf9b0893bc4ad348460e844] * admin/authors.el (authors-canonical-author-name): Ignore name issues in "lax" ChangeLogs.
git bisect bad b51009d7f02b796bcdf9b0893bc4ad348460e844
# good: [4587d8e0ef3302e9a2d99e2981897537eb320168] Document 'minibuffer-with-setup-hook'
git bisect good 4587d8e0ef3302e9a2d99e2981897537eb320168
# good: [237e96bc5259e59ac5623a93a47f64abffab4e0b] Test that advice doesn't trigger bytecomp warnings (Bug#28803)
git bisect good 237e96bc5259e59ac5623a93a47f64abffab4e0b
# bad: [6360611457a39292e11980bb522a14a5c9a58716] Port to OpenIndiana
git bisect bad 6360611457a39292e11980bb522a14a5c9a58716
# bad: [3aee7be62eaf8caef6f2fab31bee79674b3abbb7] Avoid unnecessary rounding errors in timestamps
git bisect bad 3aee7be62eaf8caef6f2fab31bee79674b3abbb7
# good: [2bfa42855bf0278497f2e4540eac2086dab254c3] Fix xdg timestamp error on 32-bit Emacs
git bisect good 2bfa42855bf0278497f2e4540eac2086dab254c3
# first bad commit: [3aee7be62eaf8caef6f2fab31bee79674b3abbb7] Avoid unnecessary rounding errors in timestamps

[-- Attachment #3: script.el --]
[-- Type: text/plain, Size: 1212 bytes --]

(defun contact-server ()
  "Contact server."
  (let* ((username "damien")
         (password "the password")
         (authorization (format "Basic %s" (base64-encode-string (format "%s:%s" username password))))
         (url "https://damien@some-nextcloud.foo/personal")
         (url-request-method "OPTIONS")
         (url-request-data nil)
         (url-request-extra-headers `(("Authorization" . ,authorization)))
         (buffer (url-retrieve-synchronously url)))
    (with-current-buffer buffer
      (goto-char (point-min))
      (when (not (re-search-forward "^HTTP[^ ]* \\([0-9]+ .*\\)$"
				    (point-at-eol) t))
        (user-error "No valid HTTP response from URL %s" url))
      (let ((response (match-string 1)))
        (when (not (string-match "2[0-9][0-9].*" response))
	  (user-error "Error while checking for OPTIONS at URL %s: %s" url response)))
      (mail-narrow-to-head)
      (let ((davheader (mail-fetch-field "dav")))
        (when (not davheader)
	  (user-error "The URL %s does not accept DAV requests" url)))
      (message "Success contacting server"))))

(progn
  (message "Contacting server (1/2)")
  (contact-server)
  (message "Contacting server (2/2)")
  (contact-server))

[-- Attachment #4: script.sh --]
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