GNU bug report logs - #18282
24.3.93; Tab completion in gud-gdb at the start of a line overwrites the prompt.

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#18282: closed (24.3.93; Tab completion in gud-gdb at the
 start of a line overwrites the prompt.)
Date: Tue, 02 Sep 2014 18:18:02 +0000

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

Your message dated Tue, 02 Sep 2014 14:17:10 -0400
with message-id <jwvr3ztewba.fsf-monnier+emacsbugs <at> gnu.org>
and subject line Re: bug#18282: 24.3.93; Tab completion in gud-gdb at the start of a line overwrites the prompt.
has caused the debbugs.gnu.org bug report #18282,
regarding 24.3.93; Tab completion in gud-gdb at the start of a line overwrites the prompt.
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
18282: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18282
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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

From: Mat Smiglarski <penthief <at> SDF.ORG>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.93; Tab completion in gud-gdb at the start of a line
 overwrites the prompt.
Date: Sun, 17 Aug 2014 11:07:42 +0100

Hello,
Tab completion in gud-gdb replaces the prompt with the completed
string. As a result this string is not sent to the gdb process.

This bug does not occur in 24.3.1. It does occur on trunk and
24.3.92, as well as 24.3.93.

To reproduce:

1. emacs -Q
2. M-: (gud-gdb "gdb")
3. Type the following at the gdb prompt "hel<TAB><RET>"

What happens is the command "help" is correctly completed, but the
prompt "(gdb)" is overwritten. This completed
string has the face "comint-highlight-prompt" and is not evaluated by 
the gdb process.

For what it is worth, the bug does not occur with "M-x gdb", only "M-x
gud-gdb".

Regards,
Mat


In GNU Emacs 24.3.93.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.8)
 of 2014-08-16 on zz
Windowing system distributor `The X.Org Foundation', version 
11.0.11501000
System Description:	Ubuntu 14.04.1 LTS

Configured using:
 `configure 'CFLAGS=-O0 -g3''

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Debugger

Minor modes in effect:
  tooltip-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

Recent input:
M-x M-p g u d - g d b <return> C-a M-f C-k <return>
h e <tab> <return> M-x r e p <tab> - e - b <tab> <
return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
user-error: Beginning of history; no preceding item
Making completion list...

Load-path shadows:
None found.

Features:
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gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
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fringe tabulated-list newcomment lisp-mode prog-mode register page
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Memory information:
((conses 16 79181 7387)
 (symbols 48 18300 0)
 (miscs 40 49 200)
 (strings 32 11682 4841)
 (string-bytes 1 317029)
 (vectors 16 10558)
 (vector-slots 8 397115 7916)
 (floats 8 66 210)
 (intervals 56 233 0)
 (buffers 960 13)
 (heap 1024 17278 783))

[Message part 3 (message/rfc822, inline)]

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Mat Smiglarski <penthief <at> SDF.ORG>
Cc: Glenn Morris <rgm <at> gnu.org>, 18282-done <at> debbugs.gnu.org
Subject: Re: bug#18282: 24.3.93;
 Tab completion in gud-gdb at the start of a line overwrites the
 prompt.
Date: Tue, 02 Sep 2014 14:17:10 -0400

>> 1. emacs -Q
>> 2. M-: (gud-gdb "gdb")
>> 3. Type the following at the gdb prompt "hel<TAB><RET>"
>> 
>> What happens is the command "help" is correctly completed, but the
>> prompt "(gdb)" is overwritten.

I installed the patch below which seems to fix it for now.


        Stefan


=== modified file 'lisp/progmodes/gud.el'
--- lisp/progmodes/gud.el	2014-02-10 01:34:22 +0000
+++ lisp/progmodes/gud.el	2014-09-02 18:14:45 +0000
@@ -809,18 +809,6 @@
 					   (current-buffer)
 					   ;; From string-match above.
 					   (length context))))
-    ;; `gud-gdb-run-command-fetch-lines' has some nasty side-effects on the
-    ;; buffer (via `gud-delete-prompt-marker'): it removes the prompt and then
-    ;; re-adds it later, thus messing up markers and overlays along the way.
-    ;; This is a problem for completion-in-region which uses an overlay to
-    ;; create a field.
-    ;; So we restore completion-in-region's field if needed.
-    ;; FIXME: change gud-gdb-run-command-fetch-lines so it doesn't modify the
-    ;; buffer at all.
-    (when (/= start (- (point) (field-beginning)))
-      (dolist (ol (overlays-at (1- (point))))
-        (when (eq (overlay-get ol 'field) 'completion)
-          (move-overlay ol (- (point) start) (overlay-end ol)))))
     ;; Protect against old versions of GDB.
     (and complete-list
 	 (string-match "^Undefined command: \"complete\"" (car complete-list))
@@ -859,7 +847,14 @@
          (save-excursion
            (skip-chars-backward "^ " (comint-line-beginning-position))
            (point))))
-    (list start end
+    ;; FIXME: `gud-gdb-run-command-fetch-lines' has some nasty side-effects on
+    ;; the buffer (via `gud-delete-prompt-marker'): it removes the prompt and
+    ;; then re-adds it later, thus messing up markers and overlays along the
+    ;; way (bug#18282).
+    ;; We use an "insert-before" marker for `start', since it's typically right
+    ;; after the prompt, which works around the problem, but is a hack (and
+    ;; comes with other downsides, e.g. if completion adds text at `start').
+    (list (copy-marker start t) end
           (completion-table-dynamic
            (apply-partially gud-gdb-completion-function
                             (buffer-substring (comint-line-beginning-position)

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