GNU bug report logs - #56818
28.1; c-mode font-lock issues in Emacs 28

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Bill Sacks <sacks <at> ucar.edu>
Subject: bug#56818: closed (Re: bug#56818: 28.1; c-mode font-lock issues
 in Emacs 28)
Date: Sat, 30 Jul 2022 13:20:02 +0000

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Your bug report

#56818: 28.1; c-mode font-lock issues in Emacs 28

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 56818 <at> debbugs.gnu.org.

-- 
56818: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=56818
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Alan Mackenzie <acm <at> muc.de>
To: Bill Sacks <sacks <at> ucar.edu>
Cc: 56818-done <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#56818: 28.1; c-mode font-lock issues in Emacs 28
Date: Sat, 30 Jul 2022 13:18:54 +0000

Hello, Bill.

On Fri, Jul 29, 2022 at 14:38:53 -0600, Bill Sacks wrote:
> Unfortunately, I still see an issue in a slightly different context. The 
> issue appears when function arguments appear on a line following the 
> function name. This one is harder to provide screen shots for, because 
> it is a bit more dynamic, but I'll try to walk through how to reproduce 
> it, referencing two attachments: The starting point is testing_start.c 
> and the end point is testing.c. If you start with testing_start.c and 
> then take some steps to get to testing.c, you will notice a few issues 
> with fontification of "somevar":

> (1) Position the cursor at the start of line 2 and hit Tab to put the 
> cursor on line 2, column 12. Type "int somevar" and notice that 
> "somevar" remains in the default face rather than being given 
> font-lock-variable-name-face.

> (2) Run M-x font-lock-fontify-buffer to make "somevar" correctly take on 
> font-lock-variable-name-face. (Interestingly, it seems fixed as soon as 
> I type "M-x" and get into the minibuffer.)

> (3) Delete then retype the "r" in "somevar", noticing that it again 
> reverts to default face

> (4) Repeat step (2) to temporarily fix the fontification

> (5) Type " // comment", noticing that "somevar" again loses its 
> fontification

> (6) Repeat step (2) to temporarily fix the fontification

> (7) Delete and retype the "t" in "comment", noticing that "somevar" 
> again loses its fontification.

> If my instructions are unclear or you cannot reproduce this, I can 
> provide a screencast where I illustrate this behavior.

Those directions are admirably clear, thanks!

> I tested briefly with Emacs 27, and it appears that the problems in (1) 
> and (3) are new issues in Emacs 28, but (5) and (7) appear in Emacs 27 
> as well.

What is happening here is a different bug, distinct from bug #56818,
with different causes.  I've opened a fresh bug for this, bug #56841,
putting you on the Cc:.

So I'm closing bug #56818 with this post, as it appears to be fixed.

[ .... ]

> Bill

-- 
Alan Mackenzie (Nuremberg, Germany).

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From: Bill Sacks <sacks <at> ucar.edu>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.1; c-mode font-lock issues in Emacs 28
Date: Thu, 28 Jul 2022 14:32:09 -0600

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Starting with Emacs 28, I have been seeing font-lock issues when editing 
C and C++ code. The situation where I see this the most (though I'm not 
sure if it's the only situation) is when I am writing a comment and 
currently have a space at the end of the comment line: in this 
situation, the fontification of a variable name or function name on the 
next line becomes broken until I type a non-space character to end the 
current line.

The attached screen shots illustrate the problem: nospaces.png shows the 
correct fontification; space_before_var.png and 
space_before_function.png show that variable and function names lose 
their fontification when there is a space at the end of the previous 
comment line. Running M-x font-lock-fontify-buffer temporarily fixes the 
issue.

The problem occurs even when using emacs -Q. I have tried the latest 
emacs28 pretest and the latest nightly build available from 
emacsformacosx (though with my customizations – NOT with emacs -Q) and 
those also exhibit the problem. The latest emacs27 from emacsformacosx 
does NOT have this issue.

(I have also been seeing slightly similar font-lock issues when editing 
python code with Emacs 28. There, I get inconsistent fontification of 
variables: variables sometimes are not fontified with 
font-lock-variable-name-face when I initially load a file, but then if I 
edit a line – e.g., by adding a space at the end of the line – then the 
variable defined on that line will become properly fontified. I realize 
that this may be a separate issue that may warrant its own bug report, 
but I thought I'd mention it in case it's related.)

Thank you,
Bill


In GNU Emacs 28.1 (build 2, aarch64-apple-darwin21.5.0, NS 
appkit-2113.50 Version 12.4 (Build 21F79))
of 2022-07-19 built on cgdm-green
Windowing system distributor 'Apple', version 10.3.2113
System Description: macOS 12.4

Configured using:
'configure --disable-dependency-tracking --disable-silent-rules
--enable-locallisppath=/opt/homebrew/share/emacs/site-lisp
--infodir=/opt/homebrew/Cellar/emacs-plus <at> 28/28.1/share/info/emacs
--prefix=/opt/homebrew/Cellar/emacs-plus <at> 28/28.1 --with-xml2
--with-gnutls --with-native-compilation --without-dbus
--without-imagemagick --with-modules --with-rsvg --with-ns
--disable-ns-self-contained 'CFLAGS=-Os -w -pipe
-mmacosx-version-min=12
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk'
'CPPFLAGS=-I/opt/homebrew/opt/zlib/include
-I/opt/homebrew/opt/icu4c/include -I/opt/homebrew/opt/sqlite/include
-I/opt/homebrew/opt/openssl <at> 1.1/include
-I/opt/homebrew/opt/readline/include -I/opt/homebrew/opt/libffi/include
-isystem/opt/homebrew/include -F/opt/homebrew/Frameworks
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk'
'LDFLAGS=-L/opt/homebrew/opt/zlib/lib -L/opt/homebrew/opt/icu4c/lib
-L/opt/homebrew/opt/sqlite/lib -L/opt/homebrew/opt/openssl <at> 1.1/lib
-L/opt/homebrew/opt/readline/lib -L/opt/homebrew/opt/libffi/lib
-L/opt/homebrew/lib -F/opt/homebrew/Frameworks
-Wl,-headerpad_max_install_names
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk''

Configured features:
ACL GLIB GMP GNUTLS JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP NOTIFY
KQUEUE NS PDUMPER PNG RSVG THREADS TIFF TOOLKIT_SCROLL_BARS XIM ZLIB

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

Major mode: C/*l

Minor modes in effect:
tooltip-mode: t
global-eldoc-mode: t
show-paren-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
indent-tabs-mode: t
transient-mark-mode: t
abbrev-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map 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 jka-compr info
vc-dispatcher vc-svn cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs cl-loaddefs cl-lib
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode 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 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 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 emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice button
loaddefs faces cus-face macroexp files window 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 native-compile emacs)

Memory information:
((conses 16 107172 9071)
(symbols 48 8698 0)
(strings 32 28953 1830)
(string-bytes 1 1020321)
(vectors 16 16903)
(vector-slots 8 352351 17895)
(floats 8 29 38)
(intervals 56 546 0)
(buffers 992 13))

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[space_before_var.png (image/png, attachment)]

[space_before_function.png (image/png, attachment)]

[nospaces.png (image/png, attachment)]

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