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6bf7aab6 | 1 | @c This is part of the Emacs manual. |
acaf905b | 2 | @c Copyright (C) 1985-1987, 1993-1995, 1997, 2001-2012 |
893db5bc | 3 | @c Free Software Foundation, Inc. |
6bf7aab6 DL |
4 | @c See file emacs.texi for copying conditions. |
5 | @iftex | |
6 | @chapter Dealing with Common Problems | |
7 | ||
8 | If you type an Emacs command you did not intend, the results are often | |
9 | mysterious. This chapter tells what you can do to cancel your mistake or | |
10 | recover from a mysterious situation. Emacs bugs and system crashes are | |
11 | also considered. | |
12 | @end iftex | |
13 | ||
0d6e9754 LT |
14 | @ifnottex |
15 | @raisesections | |
16 | @end ifnottex | |
17 | ||
d43f5a42 | 18 | @node Quitting |
6bf7aab6 DL |
19 | @section Quitting and Aborting |
20 | @cindex quitting | |
21 | ||
22 | @table @kbd | |
23 | @item C-g | |
ab26d9a1 RS |
24 | @itemx C-@key{BREAK} @r{(MS-DOS only)} |
25 | Quit: cancel running or partially typed command. | |
6bf7aab6 DL |
26 | @item C-] |
27 | Abort innermost recursive editing level and cancel the command which | |
28 | invoked it (@code{abort-recursive-edit}). | |
29 | @item @key{ESC} @key{ESC} @key{ESC} | |
30 | Either quit or abort, whichever makes sense (@code{keyboard-escape-quit}). | |
31 | @item M-x top-level | |
32 | Abort all recursive editing levels that are currently executing. | |
b2a42eb7 CY |
33 | @item C-/ |
34 | @itemx C-x u | |
35 | @itemx C-_ | |
6bf7aab6 DL |
36 | Cancel a previously made change in the buffer contents (@code{undo}). |
37 | @end table | |
38 | ||
21c80203 RS |
39 | There are two ways of canceling a command before it has finished: |
40 | @dfn{quitting} with @kbd{C-g}, and @dfn{aborting} with @kbd{C-]} or | |
41 | @kbd{M-x top-level}. Quitting cancels a partially typed command, or | |
42 | one which is still running. Aborting exits a recursive editing level | |
43 | and cancels the command that invoked the recursive edit. | |
6bf7aab6 DL |
44 | (@xref{Recursive Edit}.) |
45 | ||
46 | @cindex quitting | |
47 | @kindex C-g | |
21c80203 | 48 | Quitting with @kbd{C-g} is the way to get rid of a partially typed |
3afc838f CY |
49 | command, or a numeric argument that you don't want. Furthermore, if |
50 | you are in the middle of a command that is running, @kbd{C-g} stops | |
51 | the command in a relatively safe way. For example, if you quit out of | |
52 | a kill command that is taking a long time, either your text will | |
53 | @emph{all} still be in the buffer, or it will @emph{all} be in the | |
54 | kill ring, or maybe both. If the region is active, @kbd{C-g} | |
55 | deactivates the mark, unless Transient Mark mode is off | |
e1a3f5b1 CY |
56 | (@pxref{Disabled Transient Mark}). If you are in the middle of an |
57 | incremental search, @kbd{C-g} does special things; it may take two | |
58 | successive @kbd{C-g} characters to get out of a search. | |
59 | @xref{Incremental Search}, for details. | |
6bf7aab6 DL |
60 | |
61 | On MS-DOS, the character @kbd{C-@key{BREAK}} serves as a quit character | |
62 | like @kbd{C-g}. The reason is that it is not feasible, on MS-DOS, to | |
63 | recognize @kbd{C-g} while a command is running, between interactions | |
64 | with the user. By contrast, it @emph{is} feasible to recognize | |
92d05762 EZ |
65 | @kbd{C-@key{BREAK}} at all times. |
66 | @iftex | |
67 | @xref{MS-DOS Keyboard,,,emacs-xtra, Specialized Emacs Features}. | |
68 | @end iftex | |
69 | @ifnottex | |
70 | @xref{MS-DOS Keyboard}. | |
71 | @end ifnottex | |
72 | ||
ab26d9a1 | 73 | @findex keyboard-quit |
6bf7aab6 DL |
74 | @kbd{C-g} works by setting the variable @code{quit-flag} to @code{t} |
75 | the instant @kbd{C-g} is typed; Emacs Lisp checks this variable | |
21c80203 | 76 | frequently, and quits if it is non-@code{nil}. @kbd{C-g} is only |
6bf7aab6 | 77 | actually executed as a command if you type it while Emacs is waiting for |
ab26d9a1 | 78 | input. In that case, the command it runs is @code{keyboard-quit}. |
6bf7aab6 | 79 | |
3b6f40c5 RS |
80 | On a text terminal, if you quit with @kbd{C-g} a second time before |
81 | the first @kbd{C-g} is recognized, you activate the ``emergency | |
82 | escape'' feature and return to the shell. @xref{Emergency Escape}. | |
6bf7aab6 DL |
83 | |
84 | @cindex NFS and quitting | |
21c80203 RS |
85 | There are some situations where you cannot quit. When Emacs is |
86 | waiting for the operating system to do something, quitting is | |
87 | impossible unless special pains are taken for the particular system | |
88 | call within Emacs where the waiting occurs. We have done this for the | |
89 | system calls that users are likely to want to quit from, but it's | |
a80859d4 | 90 | possible you will encounter a case not handled. In one very common |
21c80203 RS |
91 | case---waiting for file input or output using NFS---Emacs itself knows |
92 | how to quit, but many NFS implementations simply do not allow user | |
93 | programs to stop waiting for NFS when the NFS server is hung. | |
6bf7aab6 DL |
94 | |
95 | @cindex aborting recursive edit | |
96 | @findex abort-recursive-edit | |
97 | @kindex C-] | |
98 | Aborting with @kbd{C-]} (@code{abort-recursive-edit}) is used to get | |
99 | out of a recursive editing level and cancel the command which invoked | |
100 | it. Quitting with @kbd{C-g} does not do this, and could not do this, | |
101 | because it is used to cancel a partially typed command @emph{within} the | |
102 | recursive editing level. Both operations are useful. For example, if | |
103 | you are in a recursive edit and type @kbd{C-u 8} to enter a numeric | |
104 | argument, you can cancel that argument with @kbd{C-g} and remain in the | |
105 | recursive edit. | |
106 | ||
107 | @findex keyboard-escape-quit | |
108 | @kindex ESC ESC ESC | |
21c80203 RS |
109 | The sequence @kbd{@key{ESC} @key{ESC} @key{ESC}} |
110 | (@code{keyboard-escape-quit}) can either quit or abort. (We defined | |
111 | it this way because @key{ESC} means ``get out'' in many PC programs.) | |
112 | It can cancel a prefix argument, clear a selected region, or get out | |
113 | of a Query Replace, like @kbd{C-g}. It can get out of the minibuffer | |
114 | or a recursive edit, like @kbd{C-]}. It can also get out of splitting | |
115 | the frame into multiple windows, as with @kbd{C-x 1}. One thing it | |
116 | cannot do, however, is stop a command that is running. That's because | |
117 | it executes as an ordinary command, and Emacs doesn't notice it until | |
118 | it is ready for the next command. | |
6bf7aab6 DL |
119 | |
120 | @findex top-level | |
2e606829 CY |
121 | The command @kbd{M-x top-level} is equivalent to ``enough'' |
122 | @kbd{C-]} commands to get you out of all the levels of recursive edits | |
123 | that you are in; it also exits the minibuffer if it is active. | |
124 | @kbd{C-]} gets you out one level at a time, but @kbd{M-x top-level} | |
125 | goes out all levels at once. Both @kbd{C-]} and @kbd{M-x top-level} | |
126 | are like all other commands, and unlike @kbd{C-g}, in that they take | |
127 | effect only when Emacs is ready for a command. @kbd{C-]} is an | |
128 | ordinary key and has its meaning only because of its binding in the | |
6bf7aab6 DL |
129 | keymap. @xref{Recursive Edit}. |
130 | ||
b2a42eb7 | 131 | @kbd{C-/} (@code{undo}) is not strictly speaking a way of canceling |
6bf7aab6 | 132 | a command, but you can think of it as canceling a command that already |
b2a42eb7 CY |
133 | finished executing. @xref{Undo}, for more information about the undo |
134 | facility. | |
6bf7aab6 DL |
135 | |
136 | @node Lossage, Bugs, Quitting, Top | |
137 | @section Dealing with Emacs Trouble | |
138 | ||
139 | This section describes various conditions in which Emacs fails to work | |
9e25ea70 EZ |
140 | normally, and how to recognize them and correct them. For a list of |
141 | additional problems you might encounter, see @ref{Bugs and problems, , | |
142 | Bugs and problems, efaq, GNU Emacs FAQ}, and the file @file{etc/PROBLEMS} | |
4d715abe | 143 | in the Emacs distribution. Type @kbd{C-h C-f} to read the FAQ; type |
d4ad7b96 | 144 | @kbd{C-h C-p} to read the @file{PROBLEMS} file. |
6bf7aab6 DL |
145 | |
146 | @menu | |
84c1f5fe | 147 | * DEL Does Not Delete:: What to do if @key{DEL} doesn't delete. |
82f6ab38 EZ |
148 | * Stuck Recursive:: `[...]' in mode line around the parentheses. |
149 | * Screen Garbled:: Garbage on the screen. | |
150 | * Text Garbled:: Garbage in the text. | |
82f6ab38 EZ |
151 | * Memory Full:: How to cope when you run out of memory. |
152 | * After a Crash:: Recovering editing in an Emacs session that crashed. | |
153 | * Emergency Escape:: Emergency escape--- | |
154 | What to do if Emacs stops responding. | |
155 | * Total Frustration:: When you are at your wits' end. | |
6bf7aab6 DL |
156 | @end menu |
157 | ||
82f6ab38 | 158 | @node DEL Does Not Delete |
6bf7aab6 | 159 | @subsection If @key{DEL} Fails to Delete |
7be352a8 RS |
160 | @cindex @key{DEL} vs @key{BACKSPACE} |
161 | @cindex @key{BACKSPACE} vs @key{DEL} | |
cdf648ca | 162 | @cindex usual erasure key |
7be352a8 | 163 | |
09e80d9f | 164 | Every keyboard has a large key, usually labeled @key{Backspace}, |
b2a42eb7 CY |
165 | which is ordinarily used to erase the last character that you typed. |
166 | We call this key @dfn{the usual erasure key}. In Emacs, it is | |
167 | supposed to be equivalent to @key{DEL}. | |
7be352a8 | 168 | |
aa929821 | 169 | When Emacs starts up on a graphical display, it determines |
b2a42eb7 | 170 | automatically which key should be @key{DEL}. In some unusual cases, |
cdf648ca RS |
171 | Emacs gets the wrong information from the system. If the usual |
172 | erasure key deletes forwards instead of backwards, that is probably | |
b2a42eb7 | 173 | what happened---Emacs ought to be treating the @key{Backspace} key as |
7be352a8 RS |
174 | @key{DEL}, but it isn't. |
175 | ||
b2a42eb7 | 176 | Some keyboards also have a @key{Delete} key, which is ordinarily |
522ddc9f JB |
177 | used to delete forwards. If this key deletes backward in Emacs, that |
178 | too suggests Emacs got the wrong information---but in the opposite | |
179 | sense. | |
cdf648ca RS |
180 | |
181 | On a text-only terminal, if you find the usual erasure key prompts | |
182 | for a Help command, like @kbd{Control-h}, instead of deleting a | |
183 | character, it means that key is actually sending the @key{BS} | |
184 | character. Emacs ought to be treating @key{BS} as @key{DEL}, but it | |
185 | isn't. | |
7be352a8 RS |
186 | |
187 | In all of those cases, the immediate remedy is the same: use the | |
405d5e63 RS |
188 | command @kbd{M-x normal-erase-is-backspace-mode}. This toggles |
189 | between the two modes that Emacs supports for handling @key{DEL}, so | |
21c80203 RS |
190 | if Emacs starts in the wrong mode, this should switch to the right |
191 | mode. On a text-only terminal, if you want to ask for help when | |
192 | @key{BS} is treated as @key{DEL}, use @key{F1}; @kbd{C-?} may also | |
193 | work, if it sends character code 127. | |
7be352a8 RS |
194 | |
195 | @findex normal-erase-is-backspace-mode | |
196 | To fix the problem automatically for every Emacs session, you can | |
197 | put one of the following lines into your @file{.emacs} file | |
b2a42eb7 | 198 | (@pxref{Init File}). For the first case above, where @key{Backspace} |
79ea1938 | 199 | deletes forwards instead of backwards, use this line to make |
b2a42eb7 | 200 | @key{Backspace} act as @key{DEL} (resulting in behavior compatible |
405d5e63 | 201 | with Emacs 20 and previous versions): |
7be352a8 RS |
202 | |
203 | @lisp | |
204 | (normal-erase-is-backspace-mode 0) | |
205 | @end lisp | |
206 | ||
207 | @noindent | |
b2a42eb7 | 208 | For the other two cases, use this line: |
7be352a8 RS |
209 | |
210 | @lisp | |
211 | (normal-erase-is-backspace-mode 1) | |
212 | @end lisp | |
213 | ||
214 | @vindex normal-erase-is-backspace | |
215 | Another way to fix the problem for every Emacs session is to | |
216 | customize the variable @code{normal-erase-is-backspace}: the value | |
217 | @code{t} specifies the mode where @key{BS} or @key{BACKSPACE} is | |
218 | @key{DEL}, and @code{nil} specifies the other mode. @xref{Easy | |
219 | Customization}. | |
6bf7aab6 DL |
220 | |
221 | @node Stuck Recursive | |
222 | @subsection Recursive Editing Levels | |
223 | ||
224 | Recursive editing levels are important and useful features of Emacs, but | |
aa929821 | 225 | they can seem like malfunctions if you do not understand them. |
6bf7aab6 DL |
226 | |
227 | If the mode line has square brackets @samp{[@dots{}]} around the parentheses | |
228 | that contain the names of the major and minor modes, you have entered a | |
229 | recursive editing level. If you did not do this on purpose, or if you | |
230 | don't understand what that means, you should just get out of the recursive | |
231 | editing level. To do so, type @kbd{M-x top-level}. This is called getting | |
232 | back to top level. @xref{Recursive Edit}. | |
233 | ||
234 | @node Screen Garbled | |
235 | @subsection Garbage on the Screen | |
236 | ||
3b6f40c5 RS |
237 | If the text on a text terminal looks wrong, the first thing to do is |
238 | see whether it is wrong in the buffer. Type @kbd{C-l} to redisplay | |
239 | the entire screen. If the screen appears correct after this, the | |
240 | problem was entirely in the previous screen update. (Otherwise, see | |
241 | the following section.) | |
6bf7aab6 | 242 | |
21c80203 RS |
243 | Display updating problems often result from an incorrect terminfo |
244 | entry for the terminal you are using. The file @file{etc/TERMS} in | |
245 | the Emacs distribution gives the fixes for known problems of this | |
246 | sort. @file{INSTALL} contains general advice for these problems in | |
247 | one of its sections. To investigate the possibility that you have | |
248 | this sort of problem, try Emacs on another terminal made by a | |
249 | different manufacturer. If problems happen frequently on one kind of | |
250 | terminal but not another kind, it is likely to be a bad terminfo entry, | |
251 | though it could also be due to a bug in Emacs that appears for | |
252 | terminals that have or that lack specific features. | |
6bf7aab6 DL |
253 | |
254 | @node Text Garbled | |
255 | @subsection Garbage in the Text | |
256 | ||
21c80203 RS |
257 | If @kbd{C-l} shows that the text is wrong, first type @kbd{C-h l} to |
258 | see what commands you typed to produce the observed results. Then try | |
259 | undoing the changes step by step using @kbd{C-x u}, until it gets back | |
260 | to a state you consider correct. | |
6bf7aab6 DL |
261 | |
262 | If a large portion of text appears to be missing at the beginning or | |
263 | end of the buffer, check for the word @samp{Narrow} in the mode line. | |
264 | If it appears, the text you don't see is probably still present, but | |
265 | temporarily off-limits. To make it accessible again, type @kbd{C-x n | |
266 | w}. @xref{Narrowing}. | |
267 | ||
6bf7aab6 DL |
268 | @node Memory Full |
269 | @subsection Running out of Memory | |
270 | @cindex memory full | |
271 | @cindex out of memory | |
272 | ||
180ff2e5 RS |
273 | If you get the error message @samp{Virtual memory exceeded}, save |
274 | your modified buffers with @kbd{C-x s}. This method of saving them | |
275 | has the smallest need for additional memory. Emacs keeps a reserve of | |
276 | memory which it makes available when this error happens; that should | |
277 | be enough to enable @kbd{C-x s} to complete its work. When the | |
278 | reserve has been used, @samp{!MEM FULL!} appears at the beginning of | |
279 | the mode line, indicating there is no more reserve. | |
280 | ||
281 | Once you have saved your modified buffers, you can exit this Emacs | |
282 | session and start another, or you can use @kbd{M-x kill-some-buffers} | |
283 | to free space in the current Emacs job. If this frees up sufficient | |
284 | space, Emacs will refill its memory reserve, and @samp{!MEM FULL!} | |
285 | will disappear from the mode line. That means you can safely go on | |
286 | editing in the same Emacs session. | |
6bf7aab6 DL |
287 | |
288 | Do not use @kbd{M-x buffer-menu} to save or kill buffers when you run | |
acead980 | 289 | out of memory, because the buffer menu needs a fair amount of memory |
6bf7aab6 DL |
290 | itself, and the reserve supply may not be enough. |
291 | ||
292 | @node After a Crash | |
293 | @subsection Recovery After a Crash | |
294 | ||
295 | If Emacs or the computer crashes, you can recover the files you were | |
296 | editing at the time of the crash from their auto-save files. To do | |
297 | this, start Emacs again and type the command @kbd{M-x recover-session}. | |
298 | ||
299 | This command initially displays a buffer which lists interrupted | |
300 | session files, each with its date. You must choose which session to | |
301 | recover from. Typically the one you want is the most recent one. Move | |
302 | point to the one you choose, and type @kbd{C-c C-c}. | |
303 | ||
21c80203 RS |
304 | Then @code{recover-session} considers each of the files that you |
305 | were editing during that session; for each such file, it asks whether | |
306 | to recover that file. If you answer @kbd{y} for a file, it shows the | |
307 | dates of that file and its auto-save file, then asks once again | |
308 | whether to recover that file. For the second question, you must | |
309 | confirm with @kbd{yes}. If you do, Emacs visits the file but gets the | |
310 | text from the auto-save file. | |
6bf7aab6 DL |
311 | |
312 | When @code{recover-session} is done, the files you've chosen to | |
313 | recover are present in Emacs buffers. You should then save them. Only | |
314 | this---saving them---updates the files themselves. | |
315 | ||
615cdecf NF |
316 | As a last resort, if you had buffers with content which were not |
317 | associated with any files, or if the autosave was not recent enough to | |
318 | have recorded important changes, you can use the | |
16540869 NF |
319 | @file{etc/emacs-buffer.gdb} script with GDB (the GNU Debugger) to |
320 | retrieve them from a core dump--provided that a core dump was saved, | |
321 | and that the Emacs executable was not stripped of its debugging | |
322 | symbols. | |
323 | ||
21c80203 RS |
324 | As soon as you get the core dump, rename it to another name such as |
325 | @file{core.emacs}, so that another crash won't overwrite it. | |
326 | ||
5cf98ab4 RS |
327 | To use this script, run @code{gdb} with the file name of your Emacs |
328 | executable and the file name of the core dump, e.g. @samp{gdb | |
16540869 NF |
329 | /usr/bin/emacs core.emacs}. At the @code{(gdb)} prompt, load the |
330 | recovery script: @samp{source /usr/src/emacs/etc/emacs-buffer.gdb}. | |
5cf98ab4 RS |
331 | Then type the command @code{ybuffer-list} to see which buffers are |
332 | available. For each buffer, it lists a buffer number. To save a | |
333 | buffer, use @code{ysave-buffer}; you specify the buffer number, and | |
334 | the file name to write that buffer into. You should use a file name | |
335 | which does not already exist; if the file does exist, the script does | |
a5cecf92 | 336 | not make a backup of its old contents. |
615cdecf | 337 | |
6bf7aab6 DL |
338 | @node Emergency Escape |
339 | @subsection Emergency Escape | |
340 | ||
21c80203 RS |
341 | On text-only terminals, the @dfn{emergency escape} feature suspends |
342 | Emacs immediately if you type @kbd{C-g} a second time before Emacs can | |
343 | actually respond to the first one by quitting. This is so you can | |
344 | always get out of GNU Emacs no matter how badly it might be hung. | |
345 | When things are working properly, Emacs recognizes and handles the | |
346 | first @kbd{C-g} so fast that the second one won't trigger emergency | |
347 | escape. However, if some problem prevents Emacs from handling the | |
348 | first @kbd{C-g} properly, then the second one will get you back to the | |
349 | shell. | |
6bf7aab6 | 350 | |
21c80203 RS |
351 | When you resume Emacs after a suspension caused by emergency escape, |
352 | it asks two questions before going back to what it had been doing: | |
6bf7aab6 DL |
353 | |
354 | @example | |
355 | Auto-save? (y or n) | |
356 | Abort (and dump core)? (y or n) | |
357 | @end example | |
358 | ||
359 | @noindent | |
360 | Answer each one with @kbd{y} or @kbd{n} followed by @key{RET}. | |
361 | ||
21c80203 RS |
362 | Saying @kbd{y} to @samp{Auto-save?} causes immediate auto-saving of |
363 | all modified buffers in which auto-saving is enabled. Saying @kbd{n} | |
364 | skips this. | |
365 | ||
366 | Saying @kbd{y} to @samp{Abort (and dump core)?} causes Emacs to | |
367 | crash, dumping core. This is to enable a wizard to figure out why | |
368 | Emacs was failing to quit in the first place. Execution does not | |
369 | continue after a core dump. | |
6bf7aab6 | 370 | |
21c80203 RS |
371 | If you answer this question @kbd{n}, Emacs execution resumes. With |
372 | luck, Emacs will ultimately do the requested quit. If not, each | |
373 | subsequent @kbd{C-g} invokes emergency escape again. | |
6bf7aab6 DL |
374 | |
375 | If Emacs is not really hung, just slow, you may invoke the double | |
21c80203 RS |
376 | @kbd{C-g} feature without really meaning to. Then just resume and |
377 | answer @kbd{n} to both questions, and you will get back to the former | |
378 | state. The quit you requested will happen by and by. | |
6bf7aab6 | 379 | |
58af1784 RS |
380 | Emergency escape is active only for text terminals. On graphical |
381 | displays, you can use the mouse to kill Emacs or switch to another | |
382 | program. | |
6bf7aab6 | 383 | |
21c80203 RS |
384 | On MS-DOS, you must type @kbd{C-@key{BREAK}} (twice) to cause |
385 | emergency escape---but there are cases where it won't work, when | |
386 | system call hangs or when Emacs is stuck in a tight loop in C code. | |
6bf7aab6 DL |
387 | |
388 | @node Total Frustration | |
389 | @subsection Help for Total Frustration | |
390 | @cindex Eliza | |
391 | @cindex doctor | |
392 | ||
393 | If using Emacs (or something else) becomes terribly frustrating and none | |
394 | of the techniques described above solve the problem, Emacs can still help | |
395 | you. | |
396 | ||
397 | First, if the Emacs you are using is not responding to commands, type | |
398 | @kbd{C-g C-g} to get out of it and then start a new one. | |
399 | ||
400 | @findex doctor | |
401 | Second, type @kbd{M-x doctor @key{RET}}. | |
402 | ||
21c80203 RS |
403 | The Emacs psychotherapist will help you feel better. Each time you |
404 | say something to the psychotherapist, you must end it by typing | |
405 | @key{RET} @key{RET}. This indicates you are finished typing. | |
6bf7aab6 DL |
406 | |
407 | @node Bugs, Contributing, Lossage, Top | |
408 | @section Reporting Bugs | |
409 | ||
410 | @cindex bugs | |
63e1eaa1 GM |
411 | If you think you have found a bug in Emacs, please report it. We |
412 | cannot promise to fix it, or always to agree that it is a bug, but we | |
413 | certainly want to hear about it. The same applies for new features | |
414 | you would like to see added. The following sections will help you to | |
415 | construct an effective bug report. | |
9e25ea70 | 416 | |
6bf7aab6 | 417 | @menu |
63e1eaa1 | 418 | * Known Problems:: How to read about known problems and bugs. |
8838673e GM |
419 | * Criteria: Bug Criteria. Have you really found a bug? |
420 | * Understanding Bug Reporting:: How to report a bug effectively. | |
421 | * Checklist:: Steps to follow for a good bug report. | |
422 | * Sending Patches:: How to send a patch for GNU Emacs. | |
6bf7aab6 DL |
423 | @end menu |
424 | ||
63e1eaa1 GM |
425 | @node Known Problems |
426 | @subsection Reading Existing Bug Reports and Known Problems | |
427 | ||
428 | Before reporting a bug, if at all possible please check to see if it | |
429 | is already known about. Indeed, it may already have been fixed in a | |
430 | later release of Emacs, or in the development version. Here is a list | |
431 | of the main places you can read about known issues: | |
432 | ||
433 | @itemize | |
434 | @item | |
435 | The @file{etc/PROBLEMS} file in the Emacs distribution; type @kbd{C-h | |
436 | C-p} to read it. This file contains a list of particularly well-known | |
437 | issues that have been encountered in compiling, installing and running | |
438 | Emacs. Often, there are suggestions for workarounds and solutions. | |
439 | ||
440 | @item | |
441 | Some additional user-level problems can be found in @ref{Bugs and | |
442 | problems, , Bugs and problems, efaq, GNU Emacs FAQ}. | |
443 | ||
444 | @item | |
445 | The @samp{bug-gnu-emacs} mailing list (also available as the newsgroup | |
ae742cb5 | 446 | @samp{gnu.emacs.bug}). You can read the list archives at |
63e1eaa1 GM |
447 | @url{http://lists.gnu.org/mailman/listinfo/bug-gnu-emacs}. If you |
448 | like, you can also subscribe to the list. Be aware that the sole | |
449 | purpose of this list is to provide the Emacs maintainers with | |
450 | information about bugs and feature requests. Reports may contain | |
451 | fairly large amounts of data; spectators should not complain about | |
452 | this. | |
453 | ||
454 | @item | |
455 | The bug tracker at @url{http://debbugs.gnu.org}. From early 2008, | |
ae742cb5 CY |
456 | reports from the @samp{bug-gnu-emacs} list have also been sent here. |
457 | The tracker contains the same information as the mailing list, just in | |
458 | a different format. You may prefer to browse and read reports using | |
459 | the tracker. | |
63e1eaa1 GM |
460 | |
461 | @item | |
462 | The @samp{emacs-pretest-bug} mailing list. This list is no longer | |
463 | used, and is mainly of historical interest. At one time, it was used | |
464 | for bug reports in development (i.e., not yet released) versions of | |
465 | Emacs. You can read the archives for 2003 to mid 2007 at | |
466 | @url{http://lists.gnu.org/archive/html/emacs-pretest-bug/}. From | |
467 | late 2007 to mid 2008, the address was an alias for the | |
468 | @samp{emacs-devel} mailing list. From mid 2008 onwards, it has been | |
469 | an alias for @samp{bug-gnu-emacs}. | |
470 | ||
471 | @item | |
472 | The @samp{emacs-devel} mailing list. Sometimes people report bugs to | |
473 | this mailing list. This is not the main purpose of the list, however, | |
474 | and it is much better to send bug reports to the bug list. You should | |
475 | not feel obliged to read this list before reporting a bug. | |
476 | ||
477 | @end itemize | |
478 | ||
479 | ||
6bf7aab6 DL |
480 | @node Bug Criteria |
481 | @subsection When Is There a Bug | |
482 | ||
21c80203 RS |
483 | If Emacs accesses an invalid memory location (``segmentation |
484 | fault''), or exits with an operating system error message that | |
485 | indicates a problem in the program (as opposed to something like | |
486 | ``disk full''), then it is certainly a bug. | |
6bf7aab6 DL |
487 | |
488 | If Emacs updates the display in a way that does not correspond to what is | |
489 | in the buffer, then it is certainly a bug. If a command seems to do the | |
490 | wrong thing but the problem corrects itself if you type @kbd{C-l}, it is a | |
491 | case of incorrect display updating. | |
492 | ||
493 | Taking forever to complete a command can be a bug, but you must make | |
494 | certain that it was really Emacs's fault. Some commands simply take a | |
495 | long time. Type @kbd{C-g} (@kbd{C-@key{BREAK}} on MS-DOS) and then @kbd{C-h l} | |
496 | to see whether the input Emacs received was what you intended to type; | |
497 | if the input was such that you @emph{know} it should have been processed | |
498 | quickly, report a bug. If you don't know whether the command should | |
499 | take a long time, find out by looking in the manual or by asking for | |
500 | assistance. | |
501 | ||
502 | If a command you are familiar with causes an Emacs error message in a | |
503 | case where its usual definition ought to be reasonable, it is probably a | |
504 | bug. | |
505 | ||
506 | If a command does the wrong thing, that is a bug. But be sure you know | |
507 | for certain what it ought to have done. If you aren't familiar with the | |
508 | command, or don't know for certain how the command is supposed to work, | |
509 | then it might actually be working right. Rather than jumping to | |
510 | conclusions, show the problem to someone who knows for certain. | |
511 | ||
ba3ce288 GM |
512 | Finally, a command's intended definition may not be the best |
513 | possible definition for editing with. This is a very important sort | |
514 | of problem, but it is also a matter of judgment. Also, it is easy to | |
515 | come to such a conclusion out of ignorance of some of the existing | |
516 | features. It is probably best not to complain about such a problem | |
517 | until you have checked the documentation in the usual ways, feel | |
518 | confident that you understand it, and know for certain that what you | |
21c80203 RS |
519 | want is not available. Ask other Emacs users, too. If you are not |
520 | sure what the command is supposed to do after a careful reading of the | |
521 | manual, check the index and glossary for any terms that may be | |
522 | unclear. | |
6bf7aab6 DL |
523 | |
524 | If after careful rereading of the manual you still do not understand | |
525 | what the command should do, that indicates a bug in the manual, which | |
526 | you should report. The manual's job is to make everything clear to | |
527 | people who are not Emacs experts---including you. It is just as | |
528 | important to report documentation bugs as program bugs. | |
529 | ||
530 | If the on-line documentation string of a function or variable disagrees | |
531 | with the manual, one of them must be wrong; that is a bug. | |
532 | ||
533 | @node Understanding Bug Reporting | |
534 | @subsection Understanding Bug Reporting | |
535 | ||
536 | @findex emacs-version | |
537 | When you decide that there is a bug, it is important to report it and to | |
538 | report it in a way which is useful. What is most useful is an exact | |
539 | description of what commands you type, starting with the shell command to | |
540 | run Emacs, until the problem happens. | |
541 | ||
542 | The most important principle in reporting a bug is to report | |
543 | @emph{facts}. Hypotheses and verbal descriptions are no substitute for | |
544 | the detailed raw data. Reporting the facts is straightforward, but many | |
545 | people strain to posit explanations and report them instead of the | |
546 | facts. If the explanations are based on guesses about how Emacs is | |
547 | implemented, they will be useless; meanwhile, lacking the facts, we will | |
548 | have no real information about the bug. | |
549 | ||
550 | For example, suppose that you type @kbd{C-x C-f /glorp/baz.ugh | |
21c80203 RS |
551 | @key{RET}}, visiting a file which (you know) happens to be rather |
552 | large, and Emacs displays @samp{I feel pretty today}. The best way to | |
553 | report the bug is with a sentence like the preceding one, because it | |
554 | gives all the facts. | |
6bf7aab6 DL |
555 | |
556 | A bad way would be to assume that the problem is due to the size of | |
557 | the file and say, ``I visited a large file, and Emacs displayed @samp{I | |
558 | feel pretty today}.'' This is what we mean by ``guessing | |
559 | explanations.'' The problem is just as likely to be due to the fact | |
560 | that there is a @samp{z} in the file name. If this is so, then when we | |
561 | got your report, we would try out the problem with some ``large file,'' | |
562 | probably with no @samp{z} in its name, and not see any problem. There | |
563 | is no way in the world that we could guess that we should try visiting a | |
564 | file with a @samp{z} in its name. | |
565 | ||
566 | Alternatively, the problem might be due to the fact that the file starts | |
567 | with exactly 25 spaces. For this reason, you should make sure that you | |
568 | inform us of the exact contents of any file that is needed to reproduce the | |
569 | bug. What if the problem only occurs when you have typed the @kbd{C-x C-a} | |
570 | command previously? This is why we ask you to give the exact sequence of | |
571 | characters you typed since starting the Emacs session. | |
572 | ||
573 | You should not even say ``visit a file'' instead of @kbd{C-x C-f} unless | |
574 | you @emph{know} that it makes no difference which visiting command is used. | |
575 | Similarly, rather than saying ``if I have three characters on the line,'' | |
576 | say ``after I type @kbd{@key{RET} A B C @key{RET} C-p},'' if that is | |
21c80203 | 577 | the way you entered the text. |
6bf7aab6 DL |
578 | |
579 | So please don't guess any explanations when you report a bug. If you | |
580 | want to actually @emph{debug} the problem, and report explanations that | |
581 | are more than guesses, that is useful---but please include the facts as | |
582 | well. | |
583 | ||
584 | @node Checklist | |
585 | @subsection Checklist for Bug Reports | |
586 | ||
587 | @cindex reporting bugs | |
63e1eaa1 GM |
588 | |
589 | Before reporting a bug, first try to see if the problem has already | |
590 | been reported (@pxref{Known Problems}). | |
591 | ||
592 | If you are able to, try the latest release of Emacs to see if the | |
593 | problem has already been fixed. Even better is to try the latest | |
594 | development version. We recognize that this is not easy for some | |
595 | people, so do not feel that you absolutely must do this before making | |
596 | a report. | |
6bf7aab6 | 597 | |
6bf7aab6 | 598 | @findex report-emacs-bug |
63e1eaa1 GM |
599 | The best way to write a bug report for Emacs is to use the command |
600 | @kbd{M-x report-emacs-bug}. This sets up a mail buffer | |
601 | (@pxref{Sending Mail}) and automatically inserts @emph{some} of the | |
602 | essential information. However, it cannot supply all the necessary | |
603 | information; you should still read and follow the guidelines below, so | |
604 | you can enter the other crucial information by hand before you send | |
605 | the message. You may feel that some of the information inserted by | |
606 | @kbd{M-x report-emacs-bug} is not relevant, but unless you are | |
607 | absolutely sure it is best to leave it, so that the developers can | |
608 | decide for themselves. | |
609 | ||
610 | When you have finished writing your report, type @kbd{C-c C-c} and it | |
611 | will be sent to the Emacs maintainers at @email{bug-gnu-emacs@@gnu.org}. | |
612 | (If you want to suggest an improvement or new feature, use the same | |
613 | address.) If you cannot send mail from inside Emacs, you can copy the | |
614 | text of your report to your normal mail client and send it to that | |
615 | address. Or you can simply send an email to that address describing | |
616 | the problem. | |
617 | ||
618 | Your report will be sent to the @samp{bug-gnu-emacs} mailing list, and | |
619 | stored in the tracker at @url{http://debbugs.gnu.org}. Please try to | |
620 | include a valid reply email address, in case we need to ask you for | |
621 | more information about your report. Submissions are moderated, so | |
622 | there may be a delay before your report appears. | |
623 | ||
624 | You do not need to know how the @url{http://debbugs.gnu.org} bug | |
625 | tracker works in order to report a bug, but if you want to, you can | |
626 | read the tracker's online documentation to see the various features | |
627 | you can use. | |
628 | ||
629 | All mail sent to the @samp{bug-gnu-emacs} mailing list is also | |
ffda048b | 630 | gatewayed to the @samp{gnu.emacs.bug} newsgroup. The reverse is also |
da3930f3 GM |
631 | true, but we ask you not to post bug reports (or replies) via the |
632 | newsgroup. It can make it much harder to contact you if we need to ask | |
633 | for more information, and it does not integrate well with the bug | |
634 | tracker. | |
63e1eaa1 GM |
635 | |
636 | If your data is more than 500,000 bytes, please don't include it | |
637 | directly in the bug report; instead, offer to send it on request, or | |
638 | make it available by ftp and say where. | |
6bf7aab6 DL |
639 | |
640 | To enable maintainers to investigate a bug, your report | |
641 | should include all these things: | |
642 | ||
643 | @itemize @bullet | |
644 | @item | |
63e1eaa1 GM |
645 | The version number of Emacs. Without this, we won't know whether there is any |
646 | point in looking for the bug in the current version of GNU Emacs. | |
6bf7aab6 | 647 | |
63e1eaa1 GM |
648 | @kbd{M-x report-emacs-bug} includes this information automatically, |
649 | but if you are not using that command for your report you can get the | |
650 | version number by typing @kbd{M-x emacs-version @key{RET}}. If that | |
651 | command does not work, you probably have something other than GNU | |
652 | Emacs, so you will have to report the bug somewhere else. | |
6bf7aab6 DL |
653 | |
654 | @item | |
655 | The type of machine you are using, and the operating system name and | |
63e1eaa1 GM |
656 | version number (again, automatically included by @kbd{M-x |
657 | report-emacs-bug}). @kbd{M-x emacs-version @key{RET}} provides this | |
658 | information too. Copy its output from the @samp{*Messages*} buffer, | |
659 | so that you get it all and get it accurately. | |
6bf7aab6 DL |
660 | |
661 | @item | |
662 | The operands given to the @code{configure} command when Emacs was | |
63e1eaa1 | 663 | installed (automatically included by @kbd{M-x report-emacs-bug}). |
6bf7aab6 DL |
664 | |
665 | @item | |
666 | A complete list of any modifications you have made to the Emacs source. | |
667 | (We may not have time to investigate the bug unless it happens in an | |
668 | unmodified Emacs. But if you've made modifications and you don't tell | |
669 | us, you are sending us on a wild goose chase.) | |
670 | ||
671 | Be precise about these changes. A description in English is not | |
672 | enough---send a context diff for them. | |
673 | ||
674 | Adding files of your own, or porting to another machine, is a | |
675 | modification of the source. | |
676 | ||
677 | @item | |
678 | Details of any other deviations from the standard procedure for installing | |
679 | GNU Emacs. | |
680 | ||
681 | @item | |
682 | The complete text of any files needed to reproduce the bug. | |
683 | ||
684 | If you can tell us a way to cause the problem without visiting any files, | |
685 | please do so. This makes it much easier to debug. If you do need files, | |
686 | make sure you arrange for us to see their exact contents. For example, it | |
21c80203 | 687 | can matter whether there are spaces at the ends of lines, or a |
6bf7aab6 DL |
688 | newline after the last line in the buffer (nothing ought to care whether |
689 | the last line is terminated, but try telling the bugs that). | |
690 | ||
691 | @item | |
692 | The precise commands we need to type to reproduce the bug. | |
63e1eaa1 GM |
693 | If at all possible, give a full recipe for an Emacs started with the |
694 | @samp{-Q} option (@pxref{Initial Options}). This bypasses your | |
695 | @file{.emacs} customizations. | |
6bf7aab6 DL |
696 | |
697 | @findex open-dribble-file | |
698 | @cindex dribble file | |
34a41968 | 699 | @cindex logging keystrokes |
63e1eaa1 | 700 | One way to record the input to Emacs precisely is to write a dribble |
fb23ecc2 LMI |
701 | file. To start the file, use the @kbd{M-x open-dribble-file |
702 | @key{RET}} command. From then on, Emacs copies all your input to the | |
6bf7aab6 DL |
703 | specified dribble file until the Emacs process is killed. |
704 | ||
705 | @item | |
706 | @findex open-termscript | |
707 | @cindex termscript file | |
60a96371 | 708 | @cindex @env{TERM} environment variable |
6bf7aab6 | 709 | For possible display bugs, the terminal type (the value of environment |
60a96371 | 710 | variable @env{TERM}), the complete termcap entry for the terminal from |
6bf7aab6 DL |
711 | @file{/etc/termcap} (since that file is not identical on all machines), |
712 | and the output that Emacs actually sent to the terminal. | |
713 | ||
714 | The way to collect the terminal output is to execute the Lisp expression | |
715 | ||
716 | @example | |
717 | (open-termscript "~/termscript") | |
718 | @end example | |
719 | ||
720 | @noindent | |
721 | using @kbd{M-:} or from the @samp{*scratch*} buffer just after | |
722 | starting Emacs. From then on, Emacs copies all terminal output to the | |
723 | specified termscript file as well, until the Emacs process is killed. | |
724 | If the problem happens when Emacs starts up, put this expression into | |
725 | your @file{.emacs} file so that the termscript file will be open when | |
726 | Emacs displays the screen for the first time. | |
727 | ||
728 | Be warned: it is often difficult, and sometimes impossible, to fix a | |
729 | terminal-dependent bug without access to a terminal of the type that | |
21c80203 | 730 | stimulates the bug. |
6bf7aab6 | 731 | |
d527b615 | 732 | @item |
76dd3692 | 733 | If non-@acronym{ASCII} text or internationalization is relevant, the locale that |
e6830948 | 734 | was current when you started Emacs. On GNU/Linux and Unix systems, or |
892c6176 | 735 | if you use a Posix-style shell such as Bash, you can use this shell |
e6830948 | 736 | command to view the relevant values: |
d527b615 | 737 | |
520e10f5 | 738 | @smallexample |
d881eade | 739 | echo LC_ALL=$LC_ALL LC_COLLATE=$LC_COLLATE LC_CTYPE=$LC_CTYPE \ |
b72d30a7 | 740 | LC_MESSAGES=$LC_MESSAGES LC_TIME=$LC_TIME LANG=$LANG |
520e10f5 | 741 | @end smallexample |
d527b615 | 742 | |
2cd8b7f6 EZ |
743 | Alternatively, use the @command{locale} command, if your system has it, |
744 | to display your locale settings. | |
745 | ||
746 | You can use the @kbd{M-!} command to execute these commands from | |
d527b615 | 747 | Emacs, and then copy the output from the @samp{*Messages*} buffer into |
c1cb46c7 | 748 | the bug report. Alternatively, @kbd{M-x getenv @key{RET} LC_ALL |
1ba2ce68 | 749 | @key{RET}} will display the value of @code{LC_ALL} in the echo area, and |
c1cb46c7 | 750 | you can copy its output from the @samp{*Messages*} buffer. |
d527b615 | 751 | |
6bf7aab6 DL |
752 | @item |
753 | A description of what behavior you observe that you believe is | |
754 | incorrect. For example, ``The Emacs process gets a fatal signal,'' or, | |
755 | ``The resulting text is as follows, which I think is wrong.'' | |
756 | ||
757 | Of course, if the bug is that Emacs gets a fatal signal, then one can't | |
758 | miss it. But if the bug is incorrect text, the maintainer might fail to | |
759 | notice what is wrong. Why leave it to chance? | |
760 | ||
761 | Even if the problem you experience is a fatal signal, you should still | |
762 | say so explicitly. Suppose something strange is going on, such as, your | |
763 | copy of the source is out of sync, or you have encountered a bug in the | |
764 | C library on your system. (This has happened!) Your copy might crash | |
765 | and the copy here might not. If you @emph{said} to expect a crash, then | |
766 | when Emacs here fails to crash, we would know that the bug was not | |
767 | happening. If you don't say to expect a crash, then we would not know | |
768 | whether the bug was happening---we would not be able to draw any | |
769 | conclusion from our observations. | |
770 | ||
ab26d9a1 RS |
771 | @item |
772 | If the bug is that the Emacs Manual or the Emacs Lisp Reference Manual | |
773 | fails to describe the actual behavior of Emacs, or that the text is | |
774 | confusing, copy in the text from the online manual which you think is | |
775 | at fault. If the section is small, just the section name is enough. | |
776 | ||
6bf7aab6 DL |
777 | @item |
778 | If the manifestation of the bug is an Emacs error message, it is | |
779 | important to report the precise text of the error message, and a | |
780 | backtrace showing how the Lisp program in Emacs arrived at the error. | |
781 | ||
782 | To get the error message text accurately, copy it from the | |
783 | @samp{*Messages*} buffer into the bug report. Copy all of it, not just | |
784 | part. | |
785 | ||
50556a88 | 786 | @findex toggle-debug-on-error |
68b34f99 | 787 | @pindex Edebug |
50556a88 RS |
788 | To make a backtrace for the error, use @kbd{M-x toggle-debug-on-error} |
789 | before the error happens (that is to say, you must give that command | |
21c80203 | 790 | and then make the bug happen). This causes the error to start the Lisp |
50556a88 RS |
791 | debugger, which shows you a backtrace. Copy the text of the |
792 | debugger's backtrace into the bug report. @xref{Debugger,, The Lisp | |
793 | Debugger, elisp, the Emacs Lisp Reference Manual}, for information on | |
68b34f99 | 794 | debugging Emacs Lisp programs with the Edebug package. |
6bf7aab6 DL |
795 | |
796 | This use of the debugger is possible only if you know how to make the | |
797 | bug happen again. If you can't make it happen again, at least copy | |
798 | the whole error message. | |
799 | ||
88ab4340 EZ |
800 | @vindex debug-on-quit |
801 | If Emacs appears to be stuck in an infinite loop or in a very long | |
802 | operation, typing @kbd{C-g} with the variable @code{debug-on-quit} | |
803 | non-@code{nil} will start the Lisp debugger and show a backtrace. | |
804 | This backtrace is useful for debugging such long loops, so if you can | |
805 | produce it, copy it into the bug report. | |
806 | ||
6bf7aab6 DL |
807 | @item |
808 | Check whether any programs you have loaded into the Lisp world, | |
809 | including your @file{.emacs} file, set any variables that may affect the | |
810 | functioning of Emacs. Also, see whether the problem happens in a | |
811 | freshly started Emacs without loading your @file{.emacs} file (start | |
63e1eaa1 | 812 | Emacs with the @code{-Q} switch to prevent loading the init files). If |
6bf7aab6 DL |
813 | the problem does @emph{not} occur then, you must report the precise |
814 | contents of any programs that you must load into the Lisp world in order | |
815 | to cause the problem to occur. | |
816 | ||
817 | @item | |
818 | If the problem does depend on an init file or other Lisp programs that | |
819 | are not part of the standard Emacs system, then you should make sure it | |
820 | is not a bug in those programs by complaining to their maintainers | |
821 | first. After they verify that they are using Emacs in a way that is | |
822 | supposed to work, they should report the bug. | |
823 | ||
824 | @item | |
825 | If you wish to mention something in the GNU Emacs source, show the line | |
826 | of code with a few lines of context. Don't just give a line number. | |
827 | ||
828 | The line numbers in the development sources don't match those in your | |
829 | sources. It would take extra work for the maintainers to determine what | |
830 | code is in your version at a given line number, and we could not be | |
831 | certain. | |
832 | ||
833 | @item | |
834 | Additional information from a C debugger such as GDB might enable | |
835 | someone to find a problem on a machine which he does not have available. | |
836 | If you don't know how to use GDB, please read the GDB manual---it is not | |
837 | very long, and using GDB is easy. You can find the GDB distribution, | |
838 | including the GDB manual in online form, in most of the same places you | |
839 | can find the Emacs distribution. To run Emacs under GDB, you should | |
840 | switch to the @file{src} subdirectory in which Emacs was compiled, then | |
841 | do @samp{gdb emacs}. It is important for the directory @file{src} to be | |
842 | current so that GDB will read the @file{.gdbinit} file in this | |
843 | directory. | |
844 | ||
845 | However, you need to think when you collect the additional information | |
846 | if you want it to show what causes the bug. | |
847 | ||
848 | @cindex backtrace for bug reports | |
849 | For example, many people send just a backtrace, but that is not very | |
850 | useful by itself. A simple backtrace with arguments often conveys | |
851 | little about what is happening inside GNU Emacs, because most of the | |
852 | arguments listed in the backtrace are pointers to Lisp objects. The | |
853 | numeric values of these pointers have no significance whatever; all that | |
854 | matters is the contents of the objects they point to (and most of the | |
855 | contents are themselves pointers). | |
856 | ||
857 | @findex debug_print | |
858 | To provide useful information, you need to show the values of Lisp | |
859 | objects in Lisp notation. Do this for each variable which is a Lisp | |
860 | object, in several stack frames near the bottom of the stack. Look at | |
861 | the source to see which variables are Lisp objects, because the debugger | |
862 | thinks of them as integers. | |
863 | ||
864 | To show a variable's value in Lisp syntax, first print its value, then | |
865 | use the user-defined GDB command @code{pr} to print the Lisp object in | |
866 | Lisp syntax. (If you must use another debugger, call the function | |
867 | @code{debug_print} with the object as an argument.) The @code{pr} | |
868 | command is defined by the file @file{.gdbinit}, and it works only if you | |
869 | are debugging a running process (not with a core dump). | |
870 | ||
871 | To make Lisp errors stop Emacs and return to GDB, put a breakpoint at | |
872 | @code{Fsignal}. | |
873 | ||
8389e1e2 | 874 | For a short listing of Lisp functions running, type the GDB |
177c0ea7 | 875 | command @code{xbacktrace}. |
8389e1e2 | 876 | |
6bf7aab6 DL |
877 | The file @file{.gdbinit} defines several other commands that are useful |
878 | for examining the data types and contents of Lisp objects. Their names | |
879 | begin with @samp{x}. These commands work at a lower level than | |
880 | @code{pr}, and are less convenient, but they may work even when | |
881 | @code{pr} does not, such as when debugging a core dump or when Emacs has | |
882 | had a fatal signal. | |
883 | ||
878c3c90 EZ |
884 | @cindex debugging Emacs, tricks and techniques |
885 | More detailed advice and other useful techniques for debugging Emacs | |
886 | are available in the file @file{etc/DEBUG} in the Emacs distribution. | |
887 | That file also includes instructions for investigating problems | |
888 | whereby Emacs stops responding (many people assume that Emacs is | |
ab26d9a1 | 889 | ``hung,'' whereas in fact it might be in an infinite loop). |
878c3c90 | 890 | |
ac41be63 RS |
891 | To find the file @file{etc/DEBUG} in your Emacs installation, use the |
892 | directory name stored in the variable @code{data-directory}. | |
6bf7aab6 DL |
893 | @end itemize |
894 | ||
895 | Here are some things that are not necessary in a bug report: | |
896 | ||
897 | @itemize @bullet | |
898 | @item | |
899 | A description of the envelope of the bug---this is not necessary for a | |
900 | reproducible bug. | |
901 | ||
902 | Often people who encounter a bug spend a lot of time investigating | |
903 | which changes to the input file will make the bug go away and which | |
904 | changes will not affect it. | |
905 | ||
906 | This is often time-consuming and not very useful, because the way we | |
ac41be63 RS |
907 | will find the bug is by running a single example under the debugger |
908 | with breakpoints, not by pure deduction from a series of examples. | |
909 | You might as well save time by not searching for additional examples. | |
910 | It is better to send the bug report right away, go back to editing, | |
911 | and find another bug to report. | |
6bf7aab6 DL |
912 | |
913 | Of course, if you can find a simpler example to report @emph{instead} of | |
914 | the original one, that is a convenience. Errors in the output will be | |
915 | easier to spot, running under the debugger will take less time, etc. | |
916 | ||
917 | However, simplification is not vital; if you can't do this or don't have | |
918 | time to try, please report the bug with your original test case. | |
919 | ||
c6fcb73d RS |
920 | @item |
921 | A core dump file. | |
922 | ||
923 | Debugging the core dump might be useful, but it can only be done on | |
924 | your machine, with your Emacs executable. Therefore, sending the core | |
925 | dump file to the Emacs maintainers won't be useful. Above all, don't | |
926 | include the core file in an email bug report! Such a large message | |
927 | can be extremely inconvenient. | |
928 | ||
6bf7aab6 DL |
929 | @item |
930 | A system-call trace of Emacs execution. | |
931 | ||
932 | System-call traces are very useful for certain special kinds of | |
933 | debugging, but in most cases they give little useful information. It is | |
934 | therefore strange that many people seem to think that @emph{the} way to | |
935 | report information about a crash is to send a system-call trace. Perhaps | |
936 | this is a habit formed from experience debugging programs that don't | |
937 | have source code or debugging symbols. | |
938 | ||
939 | In most programs, a backtrace is normally far, far more informative than | |
940 | a system-call trace. Even in Emacs, a simple backtrace is generally | |
941 | more informative, though to give full information you should supplement | |
942 | the backtrace by displaying variable values and printing them as Lisp | |
943 | objects with @code{pr} (see above). | |
944 | ||
945 | @item | |
946 | A patch for the bug. | |
947 | ||
948 | A patch for the bug is useful if it is a good one. But don't omit the | |
949 | other information that a bug report needs, such as the test case, on the | |
950 | assumption that a patch is sufficient. We might see problems with your | |
951 | patch and decide to fix the problem another way, or we might not | |
952 | understand it at all. And if we can't understand what bug you are | |
953 | trying to fix, or why your patch should be an improvement, we mustn't | |
954 | install it. | |
955 | ||
62fe831c | 956 | @ifnottex |
6bf7aab6 DL |
957 | @xref{Sending Patches}, for guidelines on how to make it easy for us to |
958 | understand and install your patches. | |
62fe831c | 959 | @end ifnottex |
6bf7aab6 DL |
960 | |
961 | @item | |
962 | A guess about what the bug is or what it depends on. | |
963 | ||
964 | Such guesses are usually wrong. Even experts can't guess right about | |
965 | such things without first using the debugger to find the facts. | |
966 | @end itemize | |
967 | ||
968 | @node Sending Patches | |
969 | @subsection Sending Patches for GNU Emacs | |
970 | ||
971 | @cindex sending patches for GNU Emacs | |
972 | @cindex patches, sending | |
973 | If you would like to write bug fixes or improvements for GNU Emacs, | |
974 | that is very helpful. When you send your changes, please follow these | |
975 | guidelines to make it easy for the maintainers to use them. If you | |
976 | don't follow these guidelines, your information might still be useful, | |
977 | but using it will take extra work. Maintaining GNU Emacs is a lot of | |
978 | work in the best of circumstances, and we can't keep up unless you do | |
979 | your best to help. | |
980 | ||
981 | @itemize @bullet | |
982 | @item | |
983 | Send an explanation with your changes of what problem they fix or what | |
63e1eaa1 GM |
984 | improvement they bring about. For a fix for an existing bug, it is |
985 | best to reply to the relevant discussion on the @samp{bug-gnu-emacs} | |
986 | list, or item in the @url{http://debbugs.gnu.org} tracker. Explain | |
987 | why your change fixes the bug. | |
6bf7aab6 DL |
988 | |
989 | @item | |
990 | Always include a proper bug report for the problem you think you have | |
991 | fixed. We need to convince ourselves that the change is right before | |
992 | installing it. Even if it is correct, we might have trouble | |
993 | understanding it if we don't have a way to reproduce the problem. | |
994 | ||
995 | @item | |
996 | Include all the comments that are appropriate to help people reading the | |
997 | source in the future understand why this change was needed. | |
998 | ||
999 | @item | |
1000 | Don't mix together changes made for different reasons. | |
1001 | Send them @emph{individually}. | |
1002 | ||
1003 | If you make two changes for separate reasons, then we might not want to | |
1004 | install them both. We might want to install just one. If you send them | |
1005 | all jumbled together in a single set of diffs, we have to do extra work | |
1006 | to disentangle them---to figure out which parts of the change serve | |
1007 | which purpose. If we don't have time for this, we might have to ignore | |
1008 | your changes entirely. | |
1009 | ||
1010 | If you send each change as soon as you have written it, with its own | |
1011 | explanation, then two changes never get tangled up, and we can consider | |
1012 | each one properly without any extra work to disentangle them. | |
1013 | ||
1014 | @item | |
1015 | Send each change as soon as that change is finished. Sometimes people | |
1016 | think they are helping us by accumulating many changes to send them all | |
1017 | together. As explained above, this is absolutely the worst thing you | |
1018 | could do. | |
1019 | ||
1020 | Since you should send each change separately, you might as well send it | |
1021 | right away. That gives us the option of installing it immediately if it | |
1022 | is important. | |
1023 | ||
1024 | @item | |
1025 | Use @samp{diff -c} to make your diffs. Diffs without context are hard | |
1026 | to install reliably. More than that, they are hard to study; we must | |
1027 | always study a patch to decide whether we want to install it. Unidiff | |
1028 | format is better than contextless diffs, but not as easy to read as | |
1029 | @samp{-c} format. | |
1030 | ||
1031 | If you have GNU diff, use @samp{diff -c -F'^[_a-zA-Z0-9$]+ *('} when | |
1032 | making diffs of C code. This shows the name of the function that each | |
1033 | change occurs in. | |
1034 | ||
1035 | @item | |
1036 | Avoid any ambiguity as to which is the old version and which is the new. | |
1037 | Please make the old version the first argument to diff, and the new | |
1038 | version the second argument. And please give one version or the other a | |
1039 | name that indicates whether it is the old version or your new changed | |
1040 | one. | |
1041 | ||
1042 | @item | |
1043 | Write the change log entries for your changes. This is both to save us | |
1044 | the extra work of writing them, and to help explain your changes so we | |
1045 | can understand them. | |
1046 | ||
1047 | The purpose of the change log is to show people where to find what was | |
1048 | changed. So you need to be specific about what functions you changed; | |
1049 | in large functions, it's often helpful to indicate where within the | |
1050 | function the change was. | |
1051 | ||
1052 | On the other hand, once you have shown people where to find the change, | |
1053 | you need not explain its purpose in the change log. Thus, if you add a | |
1054 | new function, all you need to say about it is that it is new. If you | |
1055 | feel that the purpose needs explaining, it probably does---but put the | |
1056 | explanation in comments in the code. It will be more useful there. | |
1057 | ||
21c80203 RS |
1058 | Please read the @file{ChangeLog} files in the @file{src} and |
1059 | @file{lisp} directories to see what sorts of information to put in, | |
1060 | and to learn the style that we use. @xref{Change Log}. | |
6bf7aab6 DL |
1061 | |
1062 | @item | |
1063 | When you write the fix, keep in mind that we can't install a change that | |
1064 | would break other systems. Please think about what effect your change | |
1065 | will have if compiled on another type of system. | |
1066 | ||
1067 | Sometimes people send fixes that @emph{might} be an improvement in | |
1068 | general---but it is hard to be sure of this. It's hard to install | |
1069 | such changes because we have to study them very carefully. Of course, | |
1070 | a good explanation of the reasoning by which you concluded the change | |
1071 | was correct can help convince us. | |
1072 | ||
1073 | The safest changes are changes to the configuration files for a | |
1074 | particular machine. These are safe because they can't create new bugs | |
1075 | on other machines. | |
1076 | ||
1077 | Please help us keep up with the workload by designing the patch in a | |
1078 | form that is clearly safe to install. | |
1079 | @end itemize | |
1080 | ||
1081 | @node Contributing, Service, Bugs, Top | |
1082 | @section Contributing to Emacs Development | |
16207c0a | 1083 | @cindex contributing to Emacs |
6bf7aab6 DL |
1084 | |
1085 | If you would like to help pretest Emacs releases to assure they work | |
1086 | well, or if you would like to work on improving Emacs, please contact | |
b656e0f4 | 1087 | the maintainers at @email{emacs-devel@@gnu.org}. A pretester |
6bf7aab6 DL |
1088 | should be prepared to investigate bugs as well as report them. If you'd |
1089 | like to work on improving Emacs, please ask for suggested projects or | |
1090 | suggest your own ideas. | |
1091 | ||
1092 | If you have already written an improvement, please tell us about it. If | |
1093 | you have not yet started work, it is useful to contact | |
b656e0f4 | 1094 | @email{emacs-devel@@gnu.org} before you start; it might be |
6bf7aab6 DL |
1095 | possible to suggest ways to make your extension fit in better with the |
1096 | rest of Emacs. | |
1097 | ||
4f3bc373 | 1098 | The development version of Emacs can be downloaded from the |
7e17c3a2 | 1099 | repository where it is actively maintained by a group of developers. |
21c80203 RS |
1100 | See the Emacs project page |
1101 | @url{http://savannah.gnu.org/projects/emacs/} for details. | |
b656e0f4 | 1102 | |
16207c0a GM |
1103 | For more information on how to contribute, see the @file{etc/CONTRIBUTE} |
1104 | file in the Emacs distribution. | |
1105 | ||
0d6e9754 | 1106 | @node Service, Copying, Contributing, Top |
6bf7aab6 DL |
1107 | @section How To Get Help with GNU Emacs |
1108 | ||
1109 | If you need help installing, using or changing GNU Emacs, there are two | |
1110 | ways to find it: | |
1111 | ||
1112 | @itemize @bullet | |
1113 | @item | |
1114 | Send a message to the mailing list | |
60a96371 | 1115 | @email{help-gnu-emacs@@gnu.org}, or post your request on |
6bf7aab6 DL |
1116 | newsgroup @code{gnu.emacs.help}. (This mailing list and newsgroup |
1117 | interconnect, so it does not matter which one you use.) | |
1118 | ||
1119 | @item | |
1120 | Look in the service directory for someone who might help you for a fee. | |
1121 | The service directory is found in the file named @file{etc/SERVICE} in the | |
1122 | Emacs distribution. | |
1123 | @end itemize | |
ab5796a9 | 1124 | |
0d6e9754 LT |
1125 | @ifnottex |
1126 | @lowersections | |
1127 | @end ifnottex |