bug#73800: 30.0.91; infinite loop in c-ts-mode--anchor-prev-sibling

bug#73800: 30.0.91; infinite loop in c-ts-mode--anchor-prev-sibling

[Renato Fernandes de Queiroz]

Steps to reproduce:
1. Open a new buffer and load c-ts-mode
2. insert the following code

int
main (int argc, char *argv[])
{
   int x;

   a
}

3. Move point past 'a'
4. Hit TAB

Emacs enters a infinite loop.

I've set debug-on-quit to t and got

Debugger entered--Lisp error: (quit)
   looking-back("^[[:space:]]*" 283)
   c-ts-mode--anchor-prev-sibling(#<treesit-node expression_statement in 
304-337> #<treesit-node compound_statement in 281-390> 304)
   treesit--simple-indent-eval((c-ts-mode--anchor-prev-sibling 
#<treesit-node expression_statement in 304-337> #<treesit-node 
compound_statement in 281-390> 304))
   treesit-simple-indent(#<treesit-node expression_statement in 304-337> 
#<treesit-node compound_statement in 281-390> 304)
   apply(treesit-simple-indent (#<treesit-node expression_statement in 
304-337> #<treesit-node compound_statement in 281-390> 304))
   #[128 "\301\302\300!\2\"\207" [treesit-indent-function apply 
default-value] 4 advice--forward](#<treesit-node expression_statement in 
304-337> #<treesit-node compound_statement in 281-390> 304)
   apply(#[128 "\301\302\300!\2\"\207" [treesit-indent-function apply 
default-value] 4 advice--forward] (#<treesit-node expression_statement 
in 304-337> #<treesit-node compound_statement in 281-390> 304))
   #f(advice c-ts-base--before-indent :filter-args #[128 
"\301\302\300!\2\"\207" [treesit-indent-function apply default-value] 4 
advice--forward])(#<treesit-node expression_statement in 304-337> 
#<treesit-node compound_statement in 281-390> 304)
   treesit--indent-1()
   treesit-indent()
   indent--funcall-widened(treesit-indent)
   indent-for-tab-command(nil)
   funcall-interactively(indent-for-tab-command nil)
   command-execute(indent-for-tab-command)


Looking at the function code I saw that a form that shoud be inside the
condition. Probably a typo. The fix is trivial:


diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 576d715510d..9003201c651 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -329,8 +329,8 @@ c-ts-mode--anchor-prev-sibling
            ;; and starting the items on the same line as {.
            (_ (goto-char (treesit-node-start prev-sibling))
               (if (or (looking-back (rx bol (* whitespace))
-                                   (line-beginning-position)))
-                     (null (treesit-node-prev-sibling prev-sibling t))
+                                   (line-beginning-position))
+                     (null (treesit-node-prev-sibling prev-sibling t)))
                   (setq continue nil)
                 (setq prev-sibling
                       (treesit-node-prev-sibling prev-sibling)))))))

This bug was introduced at e49b479f869.



In GNU Emacs 30.0.91 (build 1, x86_64-pc-linux-gnu, GTK+ Version
  3.24.43, cairo version 1.18.2) of 2024-10-13 built on carcara
Repository revision: ae75ea62324598654b32ed28bf644ec2bc4c04b2
Repository branch: emacs-30
System Description: Arch Linux

Configured using:
  'configure --with-pgtk --without-gconf --with-sound=no --without-gpm
  --without-xaw3d --with-tree-sitter --with-modules --without-libotf
  --without-m17n-flt --with-native-compilation'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG
LCMS2 LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK
PNG RSVG SECCOMP SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER
WEBP XIM GTK3 ZLIB

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

Major mode: C/*

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
   minibuffer-regexp-mode: t
   line-number-mode: t
   indent-tabs-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny rfc822
mml mml-sec epa derived epg rfc6068 epg-config gnus-util mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
dired-aux dired dired-loaddefs cl-print debug backtrace find-func
cus-edit pp wid-edit cus-start cus-load time-date c++-ts-mode c-ts-mode
c-ts-common treesit cl-extra noutline outline help-fns radix-tree
help-mode vc-git diff-mode track-changes easy-mmode vc-dispatcher
cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine
cc-vars cc-defs compile text-property-search comint ansi-osc ansi-color
ring comp-run comp-common rx ffap thingatpt url-parse auth-source cl-seq
eieio eieio-core cl-macs icons cl-loaddefs cl-lib password-cache json
subr-x map byte-opt gv bytecomp byte-compile url-vars rmc iso-transl
tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/pgtk-win pgtk-win term/common-win
touch-screen pgtk-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 dynamic-setting system-font-setting
font-render-setting cairo gtk pgtk lcms2 multi-tty move-toolbar
make-network-process native-compile emacs)

Memory information:
((conses 16 170635 186225) (symbols 48 13031 15)
  (strings 32 39676 2329) (string-bytes 1 1551295) (vectors 16 21497)
  (vector-slots 8 267270 42860) (floats 8 55 133)
  (intervals 56 1333 679) (buffers 992 18))

bug#73800: 30.0.91; infinite loop in c-ts-mode--anchor-prev-sibling

[Charalampos Mitrodimas]

Hi,

I also had this issue a week but didn't bother looking into it. The
proposed fix works. Thanks Renato!

                        C. Mitrodimas

Renato Fernandes de Queiroz <renatofq@gmail.com> writes:

> Steps to reproduce:
> 1. Open a new buffer and load c-ts-mode
> 2. insert the following code
>
> int
> main (int argc, char *argv[])
> {
>   int x;
>
>   a
> }
>
> 3. Move point past 'a'
> 4. Hit TAB
>
> Emacs enters a infinite loop.
>
> I've set debug-on-quit to t and got
>
> Debugger entered--Lisp error: (quit)
>   looking-back("^[[:space:]]*" 283)
>   c-ts-mode--anchor-prev-sibling(#<treesit-node expression_statement
>   in 304-337> #<treesit-node compound_statement in 281-390> 304)
>   treesit--simple-indent-eval((c-ts-mode--anchor-prev-sibling
>   #<treesit-node expression_statement in 304-337> #<treesit-node
>   compound_statement in 281-390> 304))
>   treesit-simple-indent(#<treesit-node expression_statement in
>   304-337> #<treesit-node compound_statement in 281-390> 304)
>   apply(treesit-simple-indent (#<treesit-node expression_statement in
>   304-337> #<treesit-node compound_statement in 281-390> 304))
>   #[128 "\301\302\300!\2\"\207" [treesit-indent-function apply
>    default-value] 4 advice--forward](#<treesit-node
>    expression_statement in 304-337> #<treesit-node compound_statement
>   in 281-390> 304)
>   apply(#[128 "\301\302\300!\2\"\207" [treesit-indent-function apply
>   default-value] 4 advice--forward] (#<treesit-node
>   expression_statement in 304-337> #<treesit-node compound_statement
>  in 281-390> 304))
>   #f(advice c-ts-base--before-indent :filter-args #[128
>    "\301\302\300!\2\"\207" [treesit-indent-function apply
>    default-value] 4 advice--forward])(#<treesit-node
>    expression_statement in 304-337> #<treesit-node compound_statement
>   in 281-390> 304)
>   treesit--indent-1()
>   treesit-indent()
>   indent--funcall-widened(treesit-indent)
>   indent-for-tab-command(nil)
>   funcall-interactively(indent-for-tab-command nil)
>   command-execute(indent-for-tab-command)
>
>
> Looking at the function code I saw that a form that shoud be inside the
> condition. Probably a typo. The fix is trivial:
>
>
> diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
> index 576d715510d..9003201c651 100644
> --- a/lisp/progmodes/c-ts-mode.el
> +++ b/lisp/progmodes/c-ts-mode.el
> @@ -329,8 +329,8 @@ c-ts-mode--anchor-prev-sibling
>            ;; and starting the items on the same line as {.
>            (_ (goto-char (treesit-node-start prev-sibling))
>               (if (or (looking-back (rx bol (* whitespace))
> -                                   (line-beginning-position)))
> -                     (null (treesit-node-prev-sibling prev-sibling t))
> +                                   (line-beginning-position))
> +                     (null (treesit-node-prev-sibling prev-sibling t)))
>                   (setq continue nil)
>                 (setq prev-sibling
>                       (treesit-node-prev-sibling prev-sibling)))))))
>
> This bug was introduced at e49b479f869.
>
>
>
> In GNU Emacs 30.0.91 (build 1, x86_64-pc-linux-gnu, GTK+ Version
>  3.24.43, cairo version 1.18.2) of 2024-10-13 built on carcara
> Repository revision: ae75ea62324598654b32ed28bf644ec2bc4c04b2
> Repository branch: emacs-30
> System Description: Arch Linux
>
> Configured using:
>  'configure --with-pgtk --without-gconf --with-sound=no --without-gpm
>  --without-xaw3d --with-tree-sitter --with-modules --without-libotf
>  --without-m17n-flt --with-native-compilation'
>
> Configured features:
> ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG
> LCMS2 LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK
> PNG RSVG SECCOMP SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER
> WEBP XIM GTK3 ZLIB
>
> Important settings:
>   value of $LANG: pt_BR.UTF-8
>   locale-coding-system: utf-8-unix
>
> Major mode: C/*
>
> 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
>   minibuffer-regexp-mode: t
>   line-number-mode: t
>   indent-tabs-mode: t
>   transient-mark-mode: t
>   auto-composition-mode: t
>   auto-encryption-mode: t
>   auto-compression-mode: t
>
> Load-path shadows:
> None found.
>
> Features:
> (shadow sort mail-extr emacsbug message mailcap yank-media puny rfc822
> mml mml-sec epa derived epg rfc6068 epg-config gnus-util mm-decode
> mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
> sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
> dired-aux dired dired-loaddefs cl-print debug backtrace find-func
> cus-edit pp wid-edit cus-start cus-load time-date c++-ts-mode c-ts-mode
> c-ts-common treesit cl-extra noutline outline help-fns radix-tree
> help-mode vc-git diff-mode track-changes easy-mmode vc-dispatcher
> cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine
> cc-vars cc-defs compile text-property-search comint ansi-osc ansi-color
> ring comp-run comp-common rx ffap thingatpt url-parse auth-source cl-seq
> eieio eieio-core cl-macs icons cl-loaddefs cl-lib password-cache json
> subr-x map byte-opt gv bytecomp byte-compile url-vars rmc iso-transl
> tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks
> lisp-float-type elisp-mode mwheel term/pgtk-win pgtk-win term/common-win
> touch-screen pgtk-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 dynamic-setting system-font-setting
> font-render-setting cairo gtk pgtk lcms2 multi-tty move-toolbar
> make-network-process native-compile emacs)
>
> Memory information:
> ((conses 16 170635 186225) (symbols 48 13031 15)
>  (strings 32 39676 2329) (string-bytes 1 1551295) (vectors 16 21497)
>  (vector-slots 8 267270 42860) (floats 8 55 133)
>  (intervals 56 1333 679) (buffers 992 18))