GNU bug report logs - #65834
29.1; highlighting bug in CPerl mode: here-document false positive

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

From: Vincent Lefevre <vincent <at> vinc17.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.1; highlighting bug in CPerl mode: here-document false positive
Date: Fri, 08 Sep 2023 23:29:18 +0200

Open a file containing the following code, in CPerl mode:

# -*- mode: cperl -*-
if ($t->[3]<<5) {
  return 0;
}
# comment

The contents are highlighted like a here-document starting at
"return 0;" probably due to the "<<" (but this is a left shift,
not a here-document declaration).

GNU Emacs 27.1, 28.2 and 29.1 are affected.

Note: I initially found when reading the "mailgraph" Perl script.


In GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
 cairo version 1.16.0) of 2023-08-30, modified by Debian built on
 x86-csail-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Debian GNU/Linux trixie/sid

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/29.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/29.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils
 --with-native-compilation --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/29.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/29.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils
 --with-native-compilation --with-cairo --with-x=yes
 --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -ffile-prefix-map=/build/reproducible-path/emacs-29.1+1=.
 -fstack-protector-strong -Wformat -Werror=format-security -Wall'
 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3
THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2
XPM GTK3 ZLIB

Important settings:
  value of $LC_COLLATE: POSIX
  value of $LC_CTYPE: C.UTF-8
  value of $LC_TIME: en_DK.utf8
  value of $LANG: POSIX
  locale-coding-system: utf-8-unix

Major mode: CPerl

Minor modes in effect:
  display-time-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-11/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-11/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-11/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-12/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-12/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-12/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-13/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-13/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-13/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-14/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-14/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-14/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-15/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-15/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-15/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-16/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-16/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-16/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-3.5/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-3.5/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-3.5/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-3.6/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-3.6/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-3.6/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-3.7/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-3.7/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-3.7/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-7/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-7/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-7/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-8/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-8/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-8/tablegen-mode
/usr/share/emacs/site-lisp/llvm-10/llvm-mode hides /usr/share/emacs/site-lisp/llvm-9/llvm-mode
/usr/share/emacs/site-lisp/llvm-10/emacs hides /usr/share/emacs/site-lisp/llvm-9/emacs
/usr/share/emacs/site-lisp/llvm-10/tablegen-mode hides /usr/share/emacs/site-lisp/llvm-9/tablegen-mode
/usr/share/emacs/site-lisp/elpa/po-mode-0.21/po-mode hides /usr/share/emacs/site-lisp/elpa-src/po-mode-0.21/po-mode
/usr/share/emacs/site-lisp/elpa/po-mode-0.21/po-mode-pkg hides /usr/share/emacs/site-lisp/elpa-src/po-mode-0.21/po-mode-pkg
/usr/share/emacs/site-lisp/elpa/po-mode-0.21/po-mode-autoloads hides /usr/share/emacs/site-lisp/elpa-src/po-mode-0.21/po-mode-autoloads
/usr/share/emacs/site-lisp/latex-cjk-thai/thai-word hides /usr/share/emacs/29.1/lisp/language/thai-word

Features:
(shadow sort mail-extr emacsbug message yank-media puny dired
dired-loaddefs rfc822 mml mml-sec epa derived epg rfc6068 epg-config
gnus-util text-property-search time-date mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils comp comp-cstr warnings
cl-extra help-mode cperl-mode rx facemenu cus-edit pp cus-start icons
wid-edit time cus-load cc-styles cc-align cc-engine cc-vars cc-defs
mmm-auto mmm-vars mmm-utils mmm-compat package browse-url url url-proxy
url-privacy url-expand url-methods url-history url-cookie
generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse
auth-source cl-seq eieio eieio-core cl-macs password-cache json subr-x
map byte-opt gv bytecomp byte-compile url-vars cl-loaddefs cl-lib rmc
iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode 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 lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
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 emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting cairo move-toolbar gtk x-toolkit xinput2 x multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 153873 9302)
 (symbols 48 12400 1)
 (strings 32 36098 2125)
 (string-bytes 1 1153829)
 (vectors 16 22304)
 (vector-slots 8 679647 81235)
 (floats 8 50 40)
 (intervals 56 318 0)
 (buffers 984 13))

Message #8 received at 65834 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Vincent Lefevre <vincent <at> vinc17.net>
Cc: Harald Jörg <haj <at> posteo.de>, 65834 <at> debbugs.gnu.org
Subject: Re: bug#65834: 29.1; highlighting bug in CPerl mode: here-document
 false positive
Date: Sun, 10 Sep 2023 00:45:37 -0700

Vincent Lefevre <vincent <at> vinc17.net> writes:

> Open a file containing the following code, in CPerl mode:
>
> # -*- mode: cperl -*-
> if ($t->[3]<<5) {
>   return 0;
> }
> # comment
>
> The contents are highlighted like a here-document starting at
> "return 0;" probably due to the "<<" (but this is a left shift,
> not a here-document declaration).
>
> GNU Emacs 27.1, 28.2 and 29.1 are affected.
>
> Note: I initially found when reading the "mailgraph" Perl script.

Copying in Harald Jörg.

> In GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
>  cairo version 1.16.0) of 2023-08-30, modified by Debian built on
>  x86-csail-01
> Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
> System Description: Debian GNU/Linux trixie/sid

Message #15 received at 65834-done <at> debbugs.gnu.org (full text, mbox):

From: Harald Jörg <haj <at> posteo.de>
To: 65834-done <at> debbugs.gnu.org
Subject: Re: 29.1; highlighting bug in CPerl mode: here-document false positive
Date: Sat, 14 Oct 2023 18:03:10 +0000

Thanks for spotting this.  Indeed, the "<<" has been mistaken as a
here-document starter.

In particular, CPerl mode treated it as a here-document with an empty
delimiter: In "<<5", the "5" is not a valid identifier.  A line checking
for digits following the "<<" has been commented out in 1999 for reasons
unrecoverable by now, but luckily this check is not required.

Empty, unquoted delimiters have been deprecated in Perl in 2013 and are
illegal as of Perl 5.28.  They are now no longer allowed in CPerl mode
as well, which avoids mis-interpreting the code from the bug report.

This also fixes the display of the mailgraph script.

Therefore, I'm closing this bug report.

-- 
Cheers,
haj

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