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6bf7aab6 | 1 | @c This is part of the Emacs manual. |
b65d8176 | 2 | @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2001, 2002, |
3f548a7c | 3 | @c 2003, 2004, 2005, 2006, 2007, 2008 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 | ||
6bf7aab6 DL |
18 | @node Quitting, Lossage, Customization, Top |
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. | |
33 | @item C-x u | |
34 | Cancel a previously made change in the buffer contents (@code{undo}). | |
35 | @end table | |
36 | ||
21c80203 RS |
37 | There are two ways of canceling a command before it has finished: |
38 | @dfn{quitting} with @kbd{C-g}, and @dfn{aborting} with @kbd{C-]} or | |
39 | @kbd{M-x top-level}. Quitting cancels a partially typed command, or | |
40 | one which is still running. Aborting exits a recursive editing level | |
41 | and cancels the command that invoked the recursive edit. | |
6bf7aab6 DL |
42 | (@xref{Recursive Edit}.) |
43 | ||
44 | @cindex quitting | |
45 | @kindex C-g | |
21c80203 | 46 | Quitting with @kbd{C-g} is the way to get rid of a partially typed |
3afc838f CY |
47 | command, or a numeric argument that you don't want. Furthermore, if |
48 | you are in the middle of a command that is running, @kbd{C-g} stops | |
49 | the command in a relatively safe way. For example, if you quit out of | |
50 | a kill command that is taking a long time, either your text will | |
51 | @emph{all} still be in the buffer, or it will @emph{all} be in the | |
52 | kill ring, or maybe both. If the region is active, @kbd{C-g} | |
53 | deactivates the mark, unless Transient Mark mode is off | |
54 | (@pxref{Persistent Mark}). If you are in the middle of an incremental | |
55 | search, @kbd{C-g} does special things; it may take two successive | |
56 | @kbd{C-g} characters to get out of a search. @xref{Incremental | |
57 | Search}, for details. | |
6bf7aab6 DL |
58 | |
59 | On MS-DOS, the character @kbd{C-@key{BREAK}} serves as a quit character | |
60 | like @kbd{C-g}. The reason is that it is not feasible, on MS-DOS, to | |
61 | recognize @kbd{C-g} while a command is running, between interactions | |
62 | with the user. By contrast, it @emph{is} feasible to recognize | |
92d05762 EZ |
63 | @kbd{C-@key{BREAK}} at all times. |
64 | @iftex | |
65 | @xref{MS-DOS Keyboard,,,emacs-xtra, Specialized Emacs Features}. | |
66 | @end iftex | |
67 | @ifnottex | |
68 | @xref{MS-DOS Keyboard}. | |
69 | @end ifnottex | |
70 | ||
ab26d9a1 | 71 | @findex keyboard-quit |
6bf7aab6 DL |
72 | @kbd{C-g} works by setting the variable @code{quit-flag} to @code{t} |
73 | the instant @kbd{C-g} is typed; Emacs Lisp checks this variable | |
21c80203 | 74 | frequently, and quits if it is non-@code{nil}. @kbd{C-g} is only |
6bf7aab6 | 75 | actually executed as a command if you type it while Emacs is waiting for |
ab26d9a1 | 76 | input. In that case, the command it runs is @code{keyboard-quit}. |
6bf7aab6 | 77 | |
3b6f40c5 RS |
78 | On a text terminal, if you quit with @kbd{C-g} a second time before |
79 | the first @kbd{C-g} is recognized, you activate the ``emergency | |
80 | escape'' feature and return to the shell. @xref{Emergency Escape}. | |
6bf7aab6 DL |
81 | |
82 | @cindex NFS and quitting | |
21c80203 RS |
83 | There are some situations where you cannot quit. When Emacs is |
84 | waiting for the operating system to do something, quitting is | |
85 | impossible unless special pains are taken for the particular system | |
86 | call within Emacs where the waiting occurs. We have done this for the | |
87 | system calls that users are likely to want to quit from, but it's | |
a80859d4 | 88 | possible you will encounter a case not handled. In one very common |
21c80203 RS |
89 | case---waiting for file input or output using NFS---Emacs itself knows |
90 | how to quit, but many NFS implementations simply do not allow user | |
91 | programs to stop waiting for NFS when the NFS server is hung. | |
6bf7aab6 DL |
92 | |
93 | @cindex aborting recursive edit | |
94 | @findex abort-recursive-edit | |
95 | @kindex C-] | |
96 | Aborting with @kbd{C-]} (@code{abort-recursive-edit}) is used to get | |
97 | out of a recursive editing level and cancel the command which invoked | |
98 | it. Quitting with @kbd{C-g} does not do this, and could not do this, | |
99 | because it is used to cancel a partially typed command @emph{within} the | |
100 | recursive editing level. Both operations are useful. For example, if | |
101 | you are in a recursive edit and type @kbd{C-u 8} to enter a numeric | |
102 | argument, you can cancel that argument with @kbd{C-g} and remain in the | |
103 | recursive edit. | |
104 | ||
105 | @findex keyboard-escape-quit | |
106 | @kindex ESC ESC ESC | |
21c80203 RS |
107 | The sequence @kbd{@key{ESC} @key{ESC} @key{ESC}} |
108 | (@code{keyboard-escape-quit}) can either quit or abort. (We defined | |
109 | it this way because @key{ESC} means ``get out'' in many PC programs.) | |
110 | It can cancel a prefix argument, clear a selected region, or get out | |
111 | of a Query Replace, like @kbd{C-g}. It can get out of the minibuffer | |
112 | or a recursive edit, like @kbd{C-]}. It can also get out of splitting | |
113 | the frame into multiple windows, as with @kbd{C-x 1}. One thing it | |
114 | cannot do, however, is stop a command that is running. That's because | |
115 | it executes as an ordinary command, and Emacs doesn't notice it until | |
116 | it is ready for the next command. | |
6bf7aab6 DL |
117 | |
118 | @findex top-level | |
2e606829 CY |
119 | The command @kbd{M-x top-level} is equivalent to ``enough'' |
120 | @kbd{C-]} commands to get you out of all the levels of recursive edits | |
121 | that you are in; it also exits the minibuffer if it is active. | |
122 | @kbd{C-]} gets you out one level at a time, but @kbd{M-x top-level} | |
123 | goes out all levels at once. Both @kbd{C-]} and @kbd{M-x top-level} | |
124 | are like all other commands, and unlike @kbd{C-g}, in that they take | |
125 | effect only when Emacs is ready for a command. @kbd{C-]} is an | |
126 | ordinary key and has its meaning only because of its binding in the | |
6bf7aab6 DL |
127 | keymap. @xref{Recursive Edit}. |
128 | ||
129 | @kbd{C-x u} (@code{undo}) is not strictly speaking a way of canceling | |
130 | a command, but you can think of it as canceling a command that already | |
b3f74d21 RS |
131 | finished executing. @xref{Undo}, for more information |
132 | about the undo facility. | |
6bf7aab6 DL |
133 | |
134 | @node Lossage, Bugs, Quitting, Top | |
135 | @section Dealing with Emacs Trouble | |
136 | ||
137 | This section describes various conditions in which Emacs fails to work | |
9e25ea70 EZ |
138 | normally, and how to recognize them and correct them. For a list of |
139 | additional problems you might encounter, see @ref{Bugs and problems, , | |
140 | Bugs and problems, efaq, GNU Emacs FAQ}, and the file @file{etc/PROBLEMS} | |
4d715abe JL |
141 | in the Emacs distribution. Type @kbd{C-h C-f} to read the FAQ; type |
142 | @kbd{C-h C-e} to read the @file{PROBLEMS} file. | |
6bf7aab6 DL |
143 | |
144 | @menu | |
84c1f5fe | 145 | * DEL Does Not Delete:: What to do if @key{DEL} doesn't delete. |
82f6ab38 EZ |
146 | * Stuck Recursive:: `[...]' in mode line around the parentheses. |
147 | * Screen Garbled:: Garbage on the screen. | |
148 | * Text Garbled:: Garbage in the text. | |
82f6ab38 EZ |
149 | * Memory Full:: How to cope when you run out of memory. |
150 | * After a Crash:: Recovering editing in an Emacs session that crashed. | |
151 | * Emergency Escape:: Emergency escape--- | |
152 | What to do if Emacs stops responding. | |
153 | * Total Frustration:: When you are at your wits' end. | |
6bf7aab6 DL |
154 | @end menu |
155 | ||
82f6ab38 | 156 | @node DEL Does Not Delete |
6bf7aab6 | 157 | @subsection If @key{DEL} Fails to Delete |
7be352a8 RS |
158 | @cindex @key{DEL} vs @key{BACKSPACE} |
159 | @cindex @key{BACKSPACE} vs @key{DEL} | |
cdf648ca | 160 | @cindex usual erasure key |
7be352a8 | 161 | |
cdf648ca RS |
162 | Every keyboard has a large key, a little ways above the @key{RET} or |
163 | @key{ENTER} key, which you normally use outside Emacs to erase the | |
164 | last character that you typed. We call this key @dfn{the usual | |
50556a88 RS |
165 | erasure key}. In Emacs, it is supposed to be equivalent to @key{DEL}, |
166 | and when Emacs is properly configured for your terminal, it translates | |
167 | that key into the character @key{DEL}. | |
7be352a8 | 168 | |
aa929821 | 169 | When Emacs starts up on a graphical display, it determines |
7be352a8 | 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 | |
173 | what happened---Emacs ought to be treating the @key{DELETE} key as | |
7be352a8 RS |
174 | @key{DEL}, but it isn't. |
175 | ||
aa929821 | 176 | On a graphical display, if the usual erasure key is labeled |
cdf648ca RS |
177 | @key{BACKSPACE} and there is a @key{DELETE} key elsewhere, but the |
178 | @key{DELETE} key deletes backward instead of forward, that too | |
179 | suggests Emacs got the wrong information---but in the opposite sense. | |
79ea1938 RS |
180 | It ought to be treating the @key{BACKSPACE} key as @key{DEL}, and |
181 | treating @key{DELETE} differently, but it isn't. | |
cdf648ca RS |
182 | |
183 | On a text-only terminal, if you find the usual erasure key prompts | |
184 | for a Help command, like @kbd{Control-h}, instead of deleting a | |
185 | character, it means that key is actually sending the @key{BS} | |
186 | character. Emacs ought to be treating @key{BS} as @key{DEL}, but it | |
187 | isn't. | |
7be352a8 RS |
188 | |
189 | In all of those cases, the immediate remedy is the same: use the | |
405d5e63 RS |
190 | command @kbd{M-x normal-erase-is-backspace-mode}. This toggles |
191 | between the two modes that Emacs supports for handling @key{DEL}, so | |
21c80203 RS |
192 | if Emacs starts in the wrong mode, this should switch to the right |
193 | mode. On a text-only terminal, if you want to ask for help when | |
194 | @key{BS} is treated as @key{DEL}, use @key{F1}; @kbd{C-?} may also | |
195 | work, if it sends character code 127. | |
7be352a8 RS |
196 | |
197 | @findex normal-erase-is-backspace-mode | |
198 | To fix the problem automatically for every Emacs session, you can | |
199 | put one of the following lines into your @file{.emacs} file | |
79ea1938 RS |
200 | (@pxref{Init File}). For the first case above, where @key{DELETE} |
201 | deletes forwards instead of backwards, use this line to make | |
405d5e63 RS |
202 | @key{DELETE} act as @key{DEL} (resulting in behavior compatible |
203 | with Emacs 20 and previous versions): | |
7be352a8 RS |
204 | |
205 | @lisp | |
206 | (normal-erase-is-backspace-mode 0) | |
207 | @end lisp | |
208 | ||
209 | @noindent | |
79ea1938 RS |
210 | For the other two cases, where @key{BACKSPACE} ought to act as |
211 | @key{DEL}, use this line: | |
7be352a8 RS |
212 | |
213 | @lisp | |
214 | (normal-erase-is-backspace-mode 1) | |
215 | @end lisp | |
216 | ||
217 | @vindex normal-erase-is-backspace | |
218 | Another way to fix the problem for every Emacs session is to | |
219 | customize the variable @code{normal-erase-is-backspace}: the value | |
220 | @code{t} specifies the mode where @key{BS} or @key{BACKSPACE} is | |
221 | @key{DEL}, and @code{nil} specifies the other mode. @xref{Easy | |
222 | Customization}. | |
6bf7aab6 | 223 | |
aa929821 | 224 | On a graphical display, it can also happen that the usual erasure key |
405d5e63 RS |
225 | is labeled @key{BACKSPACE}, there is a @key{DELETE} key elsewhere, and |
226 | both keys delete forward. This probably means that someone has | |
227 | redefined your @key{BACKSPACE} key as a @key{DELETE} key. With X, | |
228 | this is typically done with a command to the @code{xmodmap} program | |
229 | when you start the server or log in. The most likely motive for this | |
230 | customization was to support old versions of Emacs, so we recommend | |
231 | you simply remove it now. | |
232 | ||
6bf7aab6 DL |
233 | @node Stuck Recursive |
234 | @subsection Recursive Editing Levels | |
235 | ||
236 | Recursive editing levels are important and useful features of Emacs, but | |
aa929821 | 237 | they can seem like malfunctions if you do not understand them. |
6bf7aab6 DL |
238 | |
239 | If the mode line has square brackets @samp{[@dots{}]} around the parentheses | |
240 | that contain the names of the major and minor modes, you have entered a | |
241 | recursive editing level. If you did not do this on purpose, or if you | |
242 | don't understand what that means, you should just get out of the recursive | |
243 | editing level. To do so, type @kbd{M-x top-level}. This is called getting | |
244 | back to top level. @xref{Recursive Edit}. | |
245 | ||
246 | @node Screen Garbled | |
247 | @subsection Garbage on the Screen | |
248 | ||
3b6f40c5 RS |
249 | If the text on a text terminal looks wrong, the first thing to do is |
250 | see whether it is wrong in the buffer. Type @kbd{C-l} to redisplay | |
251 | the entire screen. If the screen appears correct after this, the | |
252 | problem was entirely in the previous screen update. (Otherwise, see | |
253 | the following section.) | |
6bf7aab6 | 254 | |
21c80203 RS |
255 | Display updating problems often result from an incorrect terminfo |
256 | entry for the terminal you are using. The file @file{etc/TERMS} in | |
257 | the Emacs distribution gives the fixes for known problems of this | |
258 | sort. @file{INSTALL} contains general advice for these problems in | |
259 | one of its sections. To investigate the possibility that you have | |
260 | this sort of problem, try Emacs on another terminal made by a | |
261 | different manufacturer. If problems happen frequently on one kind of | |
262 | terminal but not another kind, it is likely to be a bad terminfo entry, | |
263 | though it could also be due to a bug in Emacs that appears for | |
264 | terminals that have or that lack specific features. | |
6bf7aab6 DL |
265 | |
266 | @node Text Garbled | |
267 | @subsection Garbage in the Text | |
268 | ||
21c80203 RS |
269 | If @kbd{C-l} shows that the text is wrong, first type @kbd{C-h l} to |
270 | see what commands you typed to produce the observed results. Then try | |
271 | undoing the changes step by step using @kbd{C-x u}, until it gets back | |
272 | to a state you consider correct. | |
6bf7aab6 DL |
273 | |
274 | If a large portion of text appears to be missing at the beginning or | |
275 | end of the buffer, check for the word @samp{Narrow} in the mode line. | |
276 | If it appears, the text you don't see is probably still present, but | |
277 | temporarily off-limits. To make it accessible again, type @kbd{C-x n | |
278 | w}. @xref{Narrowing}. | |
279 | ||
6bf7aab6 DL |
280 | @node Memory Full |
281 | @subsection Running out of Memory | |
282 | @cindex memory full | |
283 | @cindex out of memory | |
284 | ||
180ff2e5 RS |
285 | If you get the error message @samp{Virtual memory exceeded}, save |
286 | your modified buffers with @kbd{C-x s}. This method of saving them | |
287 | has the smallest need for additional memory. Emacs keeps a reserve of | |
288 | memory which it makes available when this error happens; that should | |
289 | be enough to enable @kbd{C-x s} to complete its work. When the | |
290 | reserve has been used, @samp{!MEM FULL!} appears at the beginning of | |
291 | the mode line, indicating there is no more reserve. | |
292 | ||
293 | Once you have saved your modified buffers, you can exit this Emacs | |
294 | session and start another, or you can use @kbd{M-x kill-some-buffers} | |
295 | to free space in the current Emacs job. If this frees up sufficient | |
296 | space, Emacs will refill its memory reserve, and @samp{!MEM FULL!} | |
297 | will disappear from the mode line. That means you can safely go on | |
298 | editing in the same Emacs session. | |
6bf7aab6 DL |
299 | |
300 | Do not use @kbd{M-x buffer-menu} to save or kill buffers when you run | |
acead980 | 301 | out of memory, because the buffer menu needs a fair amount of memory |
6bf7aab6 DL |
302 | itself, and the reserve supply may not be enough. |
303 | ||
304 | @node After a Crash | |
305 | @subsection Recovery After a Crash | |
306 | ||
307 | If Emacs or the computer crashes, you can recover the files you were | |
308 | editing at the time of the crash from their auto-save files. To do | |
309 | this, start Emacs again and type the command @kbd{M-x recover-session}. | |
310 | ||
311 | This command initially displays a buffer which lists interrupted | |
312 | session files, each with its date. You must choose which session to | |
313 | recover from. Typically the one you want is the most recent one. Move | |
314 | point to the one you choose, and type @kbd{C-c C-c}. | |
315 | ||
21c80203 RS |
316 | Then @code{recover-session} considers each of the files that you |
317 | were editing during that session; for each such file, it asks whether | |
318 | to recover that file. If you answer @kbd{y} for a file, it shows the | |
319 | dates of that file and its auto-save file, then asks once again | |
320 | whether to recover that file. For the second question, you must | |
321 | confirm with @kbd{yes}. If you do, Emacs visits the file but gets the | |
322 | text from the auto-save file. | |
6bf7aab6 DL |
323 | |
324 | When @code{recover-session} is done, the files you've chosen to | |
325 | recover are present in Emacs buffers. You should then save them. Only | |
326 | this---saving them---updates the files themselves. | |
327 | ||
615cdecf NF |
328 | As a last resort, if you had buffers with content which were not |
329 | associated with any files, or if the autosave was not recent enough to | |
330 | have recorded important changes, you can use the | |
16540869 NF |
331 | @file{etc/emacs-buffer.gdb} script with GDB (the GNU Debugger) to |
332 | retrieve them from a core dump--provided that a core dump was saved, | |
333 | and that the Emacs executable was not stripped of its debugging | |
334 | symbols. | |
335 | ||
21c80203 RS |
336 | As soon as you get the core dump, rename it to another name such as |
337 | @file{core.emacs}, so that another crash won't overwrite it. | |
338 | ||
5cf98ab4 RS |
339 | To use this script, run @code{gdb} with the file name of your Emacs |
340 | executable and the file name of the core dump, e.g. @samp{gdb | |
16540869 NF |
341 | /usr/bin/emacs core.emacs}. At the @code{(gdb)} prompt, load the |
342 | recovery script: @samp{source /usr/src/emacs/etc/emacs-buffer.gdb}. | |
5cf98ab4 RS |
343 | Then type the command @code{ybuffer-list} to see which buffers are |
344 | available. For each buffer, it lists a buffer number. To save a | |
345 | buffer, use @code{ysave-buffer}; you specify the buffer number, and | |
346 | the file name to write that buffer into. You should use a file name | |
347 | which does not already exist; if the file does exist, the script does | |
a5cecf92 | 348 | not make a backup of its old contents. |
615cdecf | 349 | |
6bf7aab6 DL |
350 | @node Emergency Escape |
351 | @subsection Emergency Escape | |
352 | ||
21c80203 RS |
353 | On text-only terminals, the @dfn{emergency escape} feature suspends |
354 | Emacs immediately if you type @kbd{C-g} a second time before Emacs can | |
355 | actually respond to the first one by quitting. This is so you can | |
356 | always get out of GNU Emacs no matter how badly it might be hung. | |
357 | When things are working properly, Emacs recognizes and handles the | |
358 | first @kbd{C-g} so fast that the second one won't trigger emergency | |
359 | escape. However, if some problem prevents Emacs from handling the | |
360 | first @kbd{C-g} properly, then the second one will get you back to the | |
361 | shell. | |
6bf7aab6 | 362 | |
21c80203 RS |
363 | When you resume Emacs after a suspension caused by emergency escape, |
364 | it asks two questions before going back to what it had been doing: | |
6bf7aab6 DL |
365 | |
366 | @example | |
367 | Auto-save? (y or n) | |
368 | Abort (and dump core)? (y or n) | |
369 | @end example | |
370 | ||
371 | @noindent | |
372 | Answer each one with @kbd{y} or @kbd{n} followed by @key{RET}. | |
373 | ||
21c80203 RS |
374 | Saying @kbd{y} to @samp{Auto-save?} causes immediate auto-saving of |
375 | all modified buffers in which auto-saving is enabled. Saying @kbd{n} | |
376 | skips this. | |
377 | ||
378 | Saying @kbd{y} to @samp{Abort (and dump core)?} causes Emacs to | |
379 | crash, dumping core. This is to enable a wizard to figure out why | |
380 | Emacs was failing to quit in the first place. Execution does not | |
381 | continue after a core dump. | |
6bf7aab6 | 382 | |
21c80203 RS |
383 | If you answer this question @kbd{n}, Emacs execution resumes. With |
384 | luck, Emacs will ultimately do the requested quit. If not, each | |
385 | subsequent @kbd{C-g} invokes emergency escape again. | |
6bf7aab6 DL |
386 | |
387 | If Emacs is not really hung, just slow, you may invoke the double | |
21c80203 RS |
388 | @kbd{C-g} feature without really meaning to. Then just resume and |
389 | answer @kbd{n} to both questions, and you will get back to the former | |
390 | state. The quit you requested will happen by and by. | |
6bf7aab6 | 391 | |
58af1784 RS |
392 | Emergency escape is active only for text terminals. On graphical |
393 | displays, you can use the mouse to kill Emacs or switch to another | |
394 | program. | |
6bf7aab6 | 395 | |
21c80203 RS |
396 | On MS-DOS, you must type @kbd{C-@key{BREAK}} (twice) to cause |
397 | emergency escape---but there are cases where it won't work, when | |
398 | system call hangs or when Emacs is stuck in a tight loop in C code. | |
6bf7aab6 DL |
399 | |
400 | @node Total Frustration | |
401 | @subsection Help for Total Frustration | |
402 | @cindex Eliza | |
403 | @cindex doctor | |
404 | ||
405 | If using Emacs (or something else) becomes terribly frustrating and none | |
406 | of the techniques described above solve the problem, Emacs can still help | |
407 | you. | |
408 | ||
409 | First, if the Emacs you are using is not responding to commands, type | |
410 | @kbd{C-g C-g} to get out of it and then start a new one. | |
411 | ||
412 | @findex doctor | |
413 | Second, type @kbd{M-x doctor @key{RET}}. | |
414 | ||
21c80203 RS |
415 | The Emacs psychotherapist will help you feel better. Each time you |
416 | say something to the psychotherapist, you must end it by typing | |
417 | @key{RET} @key{RET}. This indicates you are finished typing. | |
6bf7aab6 DL |
418 | |
419 | @node Bugs, Contributing, Lossage, Top | |
420 | @section Reporting Bugs | |
421 | ||
422 | @cindex bugs | |
423 | Sometimes you will encounter a bug in Emacs. Although we cannot | |
424 | promise we can or will fix the bug, and we might not even agree that it | |
425 | is a bug, we want to hear about problems you encounter. Often we agree | |
426 | they are bugs and want to fix them. | |
427 | ||
428 | To make it possible for us to fix a bug, you must report it. In order | |
429 | to do so effectively, you must know when and how to do it. | |
430 | ||
9e25ea70 EZ |
431 | Before reporting a bug, it is a good idea to see if it is already |
432 | known. You can find the list of known problems in the file | |
4d715abe | 433 | @file{etc/PROBLEMS} in the Emacs distribution; type @kbd{C-h C-e} to read |
072dc5f5 EZ |
434 | it. Some additional user-level problems can be found in @ref{Bugs and |
435 | problems, , Bugs and problems, efaq, GNU Emacs FAQ}. Looking up your | |
436 | problem in these two documents might provide you with a solution or a | |
437 | work-around, or give you additional information about related issues. | |
9e25ea70 | 438 | |
6bf7aab6 DL |
439 | @menu |
440 | * Criteria: Bug Criteria. Have you really found a bug? | |
441 | * Understanding Bug Reporting:: How to report a bug effectively. | |
442 | * Checklist:: Steps to follow for a good bug report. | |
443 | * Sending Patches:: How to send a patch for GNU Emacs. | |
444 | @end menu | |
445 | ||
446 | @node Bug Criteria | |
447 | @subsection When Is There a Bug | |
448 | ||
21c80203 RS |
449 | If Emacs accesses an invalid memory location (``segmentation |
450 | fault''), or exits with an operating system error message that | |
451 | indicates a problem in the program (as opposed to something like | |
452 | ``disk full''), then it is certainly a bug. | |
6bf7aab6 DL |
453 | |
454 | If Emacs updates the display in a way that does not correspond to what is | |
455 | in the buffer, then it is certainly a bug. If a command seems to do the | |
456 | wrong thing but the problem corrects itself if you type @kbd{C-l}, it is a | |
457 | case of incorrect display updating. | |
458 | ||
459 | Taking forever to complete a command can be a bug, but you must make | |
460 | certain that it was really Emacs's fault. Some commands simply take a | |
461 | long time. Type @kbd{C-g} (@kbd{C-@key{BREAK}} on MS-DOS) and then @kbd{C-h l} | |
462 | to see whether the input Emacs received was what you intended to type; | |
463 | if the input was such that you @emph{know} it should have been processed | |
464 | quickly, report a bug. If you don't know whether the command should | |
465 | take a long time, find out by looking in the manual or by asking for | |
466 | assistance. | |
467 | ||
468 | If a command you are familiar with causes an Emacs error message in a | |
469 | case where its usual definition ought to be reasonable, it is probably a | |
470 | bug. | |
471 | ||
472 | If a command does the wrong thing, that is a bug. But be sure you know | |
473 | for certain what it ought to have done. If you aren't familiar with the | |
474 | command, or don't know for certain how the command is supposed to work, | |
475 | then it might actually be working right. Rather than jumping to | |
476 | conclusions, show the problem to someone who knows for certain. | |
477 | ||
ba3ce288 GM |
478 | Finally, a command's intended definition may not be the best |
479 | possible definition for editing with. This is a very important sort | |
480 | of problem, but it is also a matter of judgment. Also, it is easy to | |
481 | come to such a conclusion out of ignorance of some of the existing | |
482 | features. It is probably best not to complain about such a problem | |
483 | until you have checked the documentation in the usual ways, feel | |
484 | confident that you understand it, and know for certain that what you | |
21c80203 RS |
485 | want is not available. Ask other Emacs users, too. If you are not |
486 | sure what the command is supposed to do after a careful reading of the | |
487 | manual, check the index and glossary for any terms that may be | |
488 | unclear. | |
6bf7aab6 DL |
489 | |
490 | If after careful rereading of the manual you still do not understand | |
491 | what the command should do, that indicates a bug in the manual, which | |
492 | you should report. The manual's job is to make everything clear to | |
493 | people who are not Emacs experts---including you. It is just as | |
494 | important to report documentation bugs as program bugs. | |
495 | ||
496 | If the on-line documentation string of a function or variable disagrees | |
497 | with the manual, one of them must be wrong; that is a bug. | |
498 | ||
499 | @node Understanding Bug Reporting | |
500 | @subsection Understanding Bug Reporting | |
501 | ||
502 | @findex emacs-version | |
503 | When you decide that there is a bug, it is important to report it and to | |
504 | report it in a way which is useful. What is most useful is an exact | |
505 | description of what commands you type, starting with the shell command to | |
506 | run Emacs, until the problem happens. | |
507 | ||
508 | The most important principle in reporting a bug is to report | |
509 | @emph{facts}. Hypotheses and verbal descriptions are no substitute for | |
510 | the detailed raw data. Reporting the facts is straightforward, but many | |
511 | people strain to posit explanations and report them instead of the | |
512 | facts. If the explanations are based on guesses about how Emacs is | |
513 | implemented, they will be useless; meanwhile, lacking the facts, we will | |
514 | have no real information about the bug. | |
515 | ||
516 | For example, suppose that you type @kbd{C-x C-f /glorp/baz.ugh | |
21c80203 RS |
517 | @key{RET}}, visiting a file which (you know) happens to be rather |
518 | large, and Emacs displays @samp{I feel pretty today}. The best way to | |
519 | report the bug is with a sentence like the preceding one, because it | |
520 | gives all the facts. | |
6bf7aab6 DL |
521 | |
522 | A bad way would be to assume that the problem is due to the size of | |
523 | the file and say, ``I visited a large file, and Emacs displayed @samp{I | |
524 | feel pretty today}.'' This is what we mean by ``guessing | |
525 | explanations.'' The problem is just as likely to be due to the fact | |
526 | that there is a @samp{z} in the file name. If this is so, then when we | |
527 | got your report, we would try out the problem with some ``large file,'' | |
528 | probably with no @samp{z} in its name, and not see any problem. There | |
529 | is no way in the world that we could guess that we should try visiting a | |
530 | file with a @samp{z} in its name. | |
531 | ||
532 | Alternatively, the problem might be due to the fact that the file starts | |
533 | with exactly 25 spaces. For this reason, you should make sure that you | |
534 | inform us of the exact contents of any file that is needed to reproduce the | |
535 | bug. What if the problem only occurs when you have typed the @kbd{C-x C-a} | |
536 | command previously? This is why we ask you to give the exact sequence of | |
537 | characters you typed since starting the Emacs session. | |
538 | ||
539 | You should not even say ``visit a file'' instead of @kbd{C-x C-f} unless | |
540 | you @emph{know} that it makes no difference which visiting command is used. | |
541 | Similarly, rather than saying ``if I have three characters on the line,'' | |
542 | say ``after I type @kbd{@key{RET} A B C @key{RET} C-p},'' if that is | |
21c80203 | 543 | the way you entered the text. |
6bf7aab6 DL |
544 | |
545 | So please don't guess any explanations when you report a bug. If you | |
546 | want to actually @emph{debug} the problem, and report explanations that | |
547 | are more than guesses, that is useful---but please include the facts as | |
548 | well. | |
549 | ||
550 | @node Checklist | |
551 | @subsection Checklist for Bug Reports | |
552 | ||
553 | @cindex reporting bugs | |
554 | The best way to send a bug report is to mail it electronically to the | |
ab26d9a1 RS |
555 | Emacs maintainers at @email{bug-gnu-emacs@@gnu.org}, or to |
556 | @email{emacs-pretest-bug@@gnu.org} if you are pretesting an Emacs beta | |
f8b3de7e GM |
557 | release. (If you want to suggest a change as an improvement, use the |
558 | same address.) | |
6bf7aab6 DL |
559 | |
560 | If you'd like to read the bug reports, you can find them on the | |
561 | newsgroup @samp{gnu.emacs.bug}; keep in mind, however, that as a | |
562 | spectator you should not criticize anything about what you see there. | |
563 | The purpose of bug reports is to give information to the Emacs | |
564 | maintainers. Spectators are welcome only as long as they do not | |
5f5e1272 RS |
565 | interfere with this. In particular, some bug reports contain fairly |
566 | large amounts of data; spectators should not complain about this. | |
6bf7aab6 DL |
567 | |
568 | Please do not post bug reports using netnews; mail is more reliable | |
5f5e1272 RS |
569 | than netnews about reporting your correct address, which we may need |
570 | in order to ask you for more information. If your data is more than | |
571 | 500,000 bytes, please don't include it directly in the bug report; | |
572 | instead, offer to send it on request, or make it available by ftp and | |
573 | say where. | |
6bf7aab6 | 574 | |
6bf7aab6 DL |
575 | @findex report-emacs-bug |
576 | A convenient way to send a bug report for Emacs is to use the command | |
577 | @kbd{M-x report-emacs-bug}. This sets up a mail buffer (@pxref{Sending | |
578 | Mail}) and automatically inserts @emph{some} of the essential | |
579 | information. However, it cannot supply all the necessary information; | |
580 | you should still read and follow the guidelines below, so you can enter | |
581 | the other crucial information by hand before you send the message. | |
582 | ||
583 | To enable maintainers to investigate a bug, your report | |
584 | should include all these things: | |
585 | ||
586 | @itemize @bullet | |
587 | @item | |
588 | The version number of Emacs. Without this, we won't know whether there | |
589 | is any point in looking for the bug in the current version of GNU | |
590 | Emacs. | |
591 | ||
592 | You can get the version number by typing @kbd{M-x emacs-version | |
593 | @key{RET}}. If that command does not work, you probably have something | |
594 | other than GNU Emacs, so you will have to report the bug somewhere | |
595 | else. | |
596 | ||
597 | @item | |
598 | The type of machine you are using, and the operating system name and | |
599 | version number. @kbd{M-x emacs-version @key{RET}} provides this | |
600 | information too. Copy its output from the @samp{*Messages*} buffer, so | |
601 | that you get it all and get it accurately. | |
602 | ||
603 | @item | |
604 | The operands given to the @code{configure} command when Emacs was | |
605 | installed. | |
606 | ||
607 | @item | |
608 | A complete list of any modifications you have made to the Emacs source. | |
609 | (We may not have time to investigate the bug unless it happens in an | |
610 | unmodified Emacs. But if you've made modifications and you don't tell | |
611 | us, you are sending us on a wild goose chase.) | |
612 | ||
613 | Be precise about these changes. A description in English is not | |
614 | enough---send a context diff for them. | |
615 | ||
616 | Adding files of your own, or porting to another machine, is a | |
617 | modification of the source. | |
618 | ||
619 | @item | |
620 | Details of any other deviations from the standard procedure for installing | |
621 | GNU Emacs. | |
622 | ||
623 | @item | |
624 | The complete text of any files needed to reproduce the bug. | |
625 | ||
626 | If you can tell us a way to cause the problem without visiting any files, | |
627 | please do so. This makes it much easier to debug. If you do need files, | |
628 | make sure you arrange for us to see their exact contents. For example, it | |
21c80203 | 629 | can matter whether there are spaces at the ends of lines, or a |
6bf7aab6 DL |
630 | newline after the last line in the buffer (nothing ought to care whether |
631 | the last line is terminated, but try telling the bugs that). | |
632 | ||
633 | @item | |
634 | The precise commands we need to type to reproduce the bug. | |
635 | ||
636 | @findex open-dribble-file | |
637 | @cindex dribble file | |
34a41968 | 638 | @cindex logging keystrokes |
21c80203 | 639 | The easy way to record the input to Emacs precisely is to write a |
6bf7aab6 DL |
640 | dribble file. To start the file, execute the Lisp expression |
641 | ||
642 | @example | |
643 | (open-dribble-file "~/dribble") | |
644 | @end example | |
645 | ||
646 | @noindent | |
647 | using @kbd{M-:} or from the @samp{*scratch*} buffer just after | |
648 | starting Emacs. From then on, Emacs copies all your input to the | |
649 | specified dribble file until the Emacs process is killed. | |
650 | ||
651 | @item | |
652 | @findex open-termscript | |
653 | @cindex termscript file | |
60a96371 | 654 | @cindex @env{TERM} environment variable |
6bf7aab6 | 655 | For possible display bugs, the terminal type (the value of environment |
60a96371 | 656 | variable @env{TERM}), the complete termcap entry for the terminal from |
6bf7aab6 DL |
657 | @file{/etc/termcap} (since that file is not identical on all machines), |
658 | and the output that Emacs actually sent to the terminal. | |
659 | ||
660 | The way to collect the terminal output is to execute the Lisp expression | |
661 | ||
662 | @example | |
663 | (open-termscript "~/termscript") | |
664 | @end example | |
665 | ||
666 | @noindent | |
667 | using @kbd{M-:} or from the @samp{*scratch*} buffer just after | |
668 | starting Emacs. From then on, Emacs copies all terminal output to the | |
669 | specified termscript file as well, until the Emacs process is killed. | |
670 | If the problem happens when Emacs starts up, put this expression into | |
671 | your @file{.emacs} file so that the termscript file will be open when | |
672 | Emacs displays the screen for the first time. | |
673 | ||
674 | Be warned: it is often difficult, and sometimes impossible, to fix a | |
675 | terminal-dependent bug without access to a terminal of the type that | |
21c80203 | 676 | stimulates the bug. |
6bf7aab6 | 677 | |
d527b615 | 678 | @item |
76dd3692 | 679 | If non-@acronym{ASCII} text or internationalization is relevant, the locale that |
e6830948 | 680 | was current when you started Emacs. On GNU/Linux and Unix systems, or |
892c6176 | 681 | if you use a Posix-style shell such as Bash, you can use this shell |
e6830948 | 682 | command to view the relevant values: |
d527b615 | 683 | |
520e10f5 | 684 | @smallexample |
d881eade | 685 | echo LC_ALL=$LC_ALL LC_COLLATE=$LC_COLLATE LC_CTYPE=$LC_CTYPE \ |
b72d30a7 | 686 | LC_MESSAGES=$LC_MESSAGES LC_TIME=$LC_TIME LANG=$LANG |
520e10f5 | 687 | @end smallexample |
d527b615 | 688 | |
2cd8b7f6 EZ |
689 | Alternatively, use the @command{locale} command, if your system has it, |
690 | to display your locale settings. | |
691 | ||
692 | You can use the @kbd{M-!} command to execute these commands from | |
d527b615 | 693 | Emacs, and then copy the output from the @samp{*Messages*} buffer into |
c1cb46c7 | 694 | the bug report. Alternatively, @kbd{M-x getenv @key{RET} LC_ALL |
1ba2ce68 | 695 | @key{RET}} will display the value of @code{LC_ALL} in the echo area, and |
c1cb46c7 | 696 | you can copy its output from the @samp{*Messages*} buffer. |
d527b615 | 697 | |
6bf7aab6 DL |
698 | @item |
699 | A description of what behavior you observe that you believe is | |
700 | incorrect. For example, ``The Emacs process gets a fatal signal,'' or, | |
701 | ``The resulting text is as follows, which I think is wrong.'' | |
702 | ||
703 | Of course, if the bug is that Emacs gets a fatal signal, then one can't | |
704 | miss it. But if the bug is incorrect text, the maintainer might fail to | |
705 | notice what is wrong. Why leave it to chance? | |
706 | ||
707 | Even if the problem you experience is a fatal signal, you should still | |
708 | say so explicitly. Suppose something strange is going on, such as, your | |
709 | copy of the source is out of sync, or you have encountered a bug in the | |
710 | C library on your system. (This has happened!) Your copy might crash | |
711 | and the copy here might not. If you @emph{said} to expect a crash, then | |
712 | when Emacs here fails to crash, we would know that the bug was not | |
713 | happening. If you don't say to expect a crash, then we would not know | |
714 | whether the bug was happening---we would not be able to draw any | |
715 | conclusion from our observations. | |
716 | ||
ab26d9a1 RS |
717 | @item |
718 | If the bug is that the Emacs Manual or the Emacs Lisp Reference Manual | |
719 | fails to describe the actual behavior of Emacs, or that the text is | |
720 | confusing, copy in the text from the online manual which you think is | |
721 | at fault. If the section is small, just the section name is enough. | |
722 | ||
6bf7aab6 DL |
723 | @item |
724 | If the manifestation of the bug is an Emacs error message, it is | |
725 | important to report the precise text of the error message, and a | |
726 | backtrace showing how the Lisp program in Emacs arrived at the error. | |
727 | ||
728 | To get the error message text accurately, copy it from the | |
729 | @samp{*Messages*} buffer into the bug report. Copy all of it, not just | |
730 | part. | |
731 | ||
50556a88 | 732 | @findex toggle-debug-on-error |
68b34f99 | 733 | @pindex Edebug |
50556a88 RS |
734 | To make a backtrace for the error, use @kbd{M-x toggle-debug-on-error} |
735 | before the error happens (that is to say, you must give that command | |
21c80203 | 736 | and then make the bug happen). This causes the error to start the Lisp |
50556a88 RS |
737 | debugger, which shows you a backtrace. Copy the text of the |
738 | debugger's backtrace into the bug report. @xref{Debugger,, The Lisp | |
739 | Debugger, elisp, the Emacs Lisp Reference Manual}, for information on | |
68b34f99 | 740 | debugging Emacs Lisp programs with the Edebug package. |
6bf7aab6 DL |
741 | |
742 | This use of the debugger is possible only if you know how to make the | |
743 | bug happen again. If you can't make it happen again, at least copy | |
744 | the whole error message. | |
745 | ||
746 | @item | |
747 | Check whether any programs you have loaded into the Lisp world, | |
748 | including your @file{.emacs} file, set any variables that may affect the | |
749 | functioning of Emacs. Also, see whether the problem happens in a | |
750 | freshly started Emacs without loading your @file{.emacs} file (start | |
751 | Emacs with the @code{-q} switch to prevent loading the init file). If | |
752 | the problem does @emph{not} occur then, you must report the precise | |
753 | contents of any programs that you must load into the Lisp world in order | |
754 | to cause the problem to occur. | |
755 | ||
756 | @item | |
757 | If the problem does depend on an init file or other Lisp programs that | |
758 | are not part of the standard Emacs system, then you should make sure it | |
759 | is not a bug in those programs by complaining to their maintainers | |
760 | first. After they verify that they are using Emacs in a way that is | |
761 | supposed to work, they should report the bug. | |
762 | ||
763 | @item | |
764 | If you wish to mention something in the GNU Emacs source, show the line | |
765 | of code with a few lines of context. Don't just give a line number. | |
766 | ||
767 | The line numbers in the development sources don't match those in your | |
768 | sources. It would take extra work for the maintainers to determine what | |
769 | code is in your version at a given line number, and we could not be | |
770 | certain. | |
771 | ||
772 | @item | |
773 | Additional information from a C debugger such as GDB might enable | |
774 | someone to find a problem on a machine which he does not have available. | |
775 | If you don't know how to use GDB, please read the GDB manual---it is not | |
776 | very long, and using GDB is easy. You can find the GDB distribution, | |
777 | including the GDB manual in online form, in most of the same places you | |
778 | can find the Emacs distribution. To run Emacs under GDB, you should | |
779 | switch to the @file{src} subdirectory in which Emacs was compiled, then | |
780 | do @samp{gdb emacs}. It is important for the directory @file{src} to be | |
781 | current so that GDB will read the @file{.gdbinit} file in this | |
782 | directory. | |
783 | ||
784 | However, you need to think when you collect the additional information | |
785 | if you want it to show what causes the bug. | |
786 | ||
787 | @cindex backtrace for bug reports | |
788 | For example, many people send just a backtrace, but that is not very | |
789 | useful by itself. A simple backtrace with arguments often conveys | |
790 | little about what is happening inside GNU Emacs, because most of the | |
791 | arguments listed in the backtrace are pointers to Lisp objects. The | |
792 | numeric values of these pointers have no significance whatever; all that | |
793 | matters is the contents of the objects they point to (and most of the | |
794 | contents are themselves pointers). | |
795 | ||
796 | @findex debug_print | |
797 | To provide useful information, you need to show the values of Lisp | |
798 | objects in Lisp notation. Do this for each variable which is a Lisp | |
799 | object, in several stack frames near the bottom of the stack. Look at | |
800 | the source to see which variables are Lisp objects, because the debugger | |
801 | thinks of them as integers. | |
802 | ||
803 | To show a variable's value in Lisp syntax, first print its value, then | |
804 | use the user-defined GDB command @code{pr} to print the Lisp object in | |
805 | Lisp syntax. (If you must use another debugger, call the function | |
806 | @code{debug_print} with the object as an argument.) The @code{pr} | |
807 | command is defined by the file @file{.gdbinit}, and it works only if you | |
808 | are debugging a running process (not with a core dump). | |
809 | ||
810 | To make Lisp errors stop Emacs and return to GDB, put a breakpoint at | |
811 | @code{Fsignal}. | |
812 | ||
8389e1e2 | 813 | For a short listing of Lisp functions running, type the GDB |
177c0ea7 | 814 | command @code{xbacktrace}. |
8389e1e2 | 815 | |
6bf7aab6 DL |
816 | The file @file{.gdbinit} defines several other commands that are useful |
817 | for examining the data types and contents of Lisp objects. Their names | |
818 | begin with @samp{x}. These commands work at a lower level than | |
819 | @code{pr}, and are less convenient, but they may work even when | |
820 | @code{pr} does not, such as when debugging a core dump or when Emacs has | |
821 | had a fatal signal. | |
822 | ||
878c3c90 EZ |
823 | @cindex debugging Emacs, tricks and techniques |
824 | More detailed advice and other useful techniques for debugging Emacs | |
825 | are available in the file @file{etc/DEBUG} in the Emacs distribution. | |
826 | That file also includes instructions for investigating problems | |
827 | whereby Emacs stops responding (many people assume that Emacs is | |
ab26d9a1 | 828 | ``hung,'' whereas in fact it might be in an infinite loop). |
878c3c90 | 829 | |
ac41be63 RS |
830 | To find the file @file{etc/DEBUG} in your Emacs installation, use the |
831 | directory name stored in the variable @code{data-directory}. | |
6bf7aab6 DL |
832 | @end itemize |
833 | ||
834 | Here are some things that are not necessary in a bug report: | |
835 | ||
836 | @itemize @bullet | |
837 | @item | |
838 | A description of the envelope of the bug---this is not necessary for a | |
839 | reproducible bug. | |
840 | ||
841 | Often people who encounter a bug spend a lot of time investigating | |
842 | which changes to the input file will make the bug go away and which | |
843 | changes will not affect it. | |
844 | ||
845 | This is often time-consuming and not very useful, because the way we | |
ac41be63 RS |
846 | will find the bug is by running a single example under the debugger |
847 | with breakpoints, not by pure deduction from a series of examples. | |
848 | You might as well save time by not searching for additional examples. | |
849 | It is better to send the bug report right away, go back to editing, | |
850 | and find another bug to report. | |
6bf7aab6 DL |
851 | |
852 | Of course, if you can find a simpler example to report @emph{instead} of | |
853 | the original one, that is a convenience. Errors in the output will be | |
854 | easier to spot, running under the debugger will take less time, etc. | |
855 | ||
856 | However, simplification is not vital; if you can't do this or don't have | |
857 | time to try, please report the bug with your original test case. | |
858 | ||
c6fcb73d RS |
859 | @item |
860 | A core dump file. | |
861 | ||
862 | Debugging the core dump might be useful, but it can only be done on | |
863 | your machine, with your Emacs executable. Therefore, sending the core | |
864 | dump file to the Emacs maintainers won't be useful. Above all, don't | |
865 | include the core file in an email bug report! Such a large message | |
866 | can be extremely inconvenient. | |
867 | ||
6bf7aab6 DL |
868 | @item |
869 | A system-call trace of Emacs execution. | |
870 | ||
871 | System-call traces are very useful for certain special kinds of | |
872 | debugging, but in most cases they give little useful information. It is | |
873 | therefore strange that many people seem to think that @emph{the} way to | |
874 | report information about a crash is to send a system-call trace. Perhaps | |
875 | this is a habit formed from experience debugging programs that don't | |
876 | have source code or debugging symbols. | |
877 | ||
878 | In most programs, a backtrace is normally far, far more informative than | |
879 | a system-call trace. Even in Emacs, a simple backtrace is generally | |
880 | more informative, though to give full information you should supplement | |
881 | the backtrace by displaying variable values and printing them as Lisp | |
882 | objects with @code{pr} (see above). | |
883 | ||
884 | @item | |
885 | A patch for the bug. | |
886 | ||
887 | A patch for the bug is useful if it is a good one. But don't omit the | |
888 | other information that a bug report needs, such as the test case, on the | |
889 | assumption that a patch is sufficient. We might see problems with your | |
890 | patch and decide to fix the problem another way, or we might not | |
891 | understand it at all. And if we can't understand what bug you are | |
892 | trying to fix, or why your patch should be an improvement, we mustn't | |
893 | install it. | |
894 | ||
62fe831c | 895 | @ifnottex |
6bf7aab6 DL |
896 | @xref{Sending Patches}, for guidelines on how to make it easy for us to |
897 | understand and install your patches. | |
62fe831c | 898 | @end ifnottex |
6bf7aab6 DL |
899 | |
900 | @item | |
901 | A guess about what the bug is or what it depends on. | |
902 | ||
903 | Such guesses are usually wrong. Even experts can't guess right about | |
904 | such things without first using the debugger to find the facts. | |
905 | @end itemize | |
906 | ||
907 | @node Sending Patches | |
908 | @subsection Sending Patches for GNU Emacs | |
909 | ||
910 | @cindex sending patches for GNU Emacs | |
911 | @cindex patches, sending | |
912 | If you would like to write bug fixes or improvements for GNU Emacs, | |
913 | that is very helpful. When you send your changes, please follow these | |
914 | guidelines to make it easy for the maintainers to use them. If you | |
915 | don't follow these guidelines, your information might still be useful, | |
916 | but using it will take extra work. Maintaining GNU Emacs is a lot of | |
917 | work in the best of circumstances, and we can't keep up unless you do | |
918 | your best to help. | |
919 | ||
920 | @itemize @bullet | |
921 | @item | |
922 | Send an explanation with your changes of what problem they fix or what | |
923 | improvement they bring about. For a bug fix, just include a copy of the | |
924 | bug report, and explain why the change fixes the bug. | |
925 | ||
926 | (Referring to a bug report is not as good as including it, because then | |
927 | we will have to look it up, and we have probably already deleted it if | |
928 | we've already fixed the bug.) | |
929 | ||
930 | @item | |
931 | Always include a proper bug report for the problem you think you have | |
932 | fixed. We need to convince ourselves that the change is right before | |
933 | installing it. Even if it is correct, we might have trouble | |
934 | understanding it if we don't have a way to reproduce the problem. | |
935 | ||
936 | @item | |
937 | Include all the comments that are appropriate to help people reading the | |
938 | source in the future understand why this change was needed. | |
939 | ||
940 | @item | |
941 | Don't mix together changes made for different reasons. | |
942 | Send them @emph{individually}. | |
943 | ||
944 | If you make two changes for separate reasons, then we might not want to | |
945 | install them both. We might want to install just one. If you send them | |
946 | all jumbled together in a single set of diffs, we have to do extra work | |
947 | to disentangle them---to figure out which parts of the change serve | |
948 | which purpose. If we don't have time for this, we might have to ignore | |
949 | your changes entirely. | |
950 | ||
951 | If you send each change as soon as you have written it, with its own | |
952 | explanation, then two changes never get tangled up, and we can consider | |
953 | each one properly without any extra work to disentangle them. | |
954 | ||
955 | @item | |
956 | Send each change as soon as that change is finished. Sometimes people | |
957 | think they are helping us by accumulating many changes to send them all | |
958 | together. As explained above, this is absolutely the worst thing you | |
959 | could do. | |
960 | ||
961 | Since you should send each change separately, you might as well send it | |
962 | right away. That gives us the option of installing it immediately if it | |
963 | is important. | |
964 | ||
965 | @item | |
966 | Use @samp{diff -c} to make your diffs. Diffs without context are hard | |
967 | to install reliably. More than that, they are hard to study; we must | |
968 | always study a patch to decide whether we want to install it. Unidiff | |
969 | format is better than contextless diffs, but not as easy to read as | |
970 | @samp{-c} format. | |
971 | ||
972 | If you have GNU diff, use @samp{diff -c -F'^[_a-zA-Z0-9$]+ *('} when | |
973 | making diffs of C code. This shows the name of the function that each | |
974 | change occurs in. | |
975 | ||
976 | @item | |
977 | Avoid any ambiguity as to which is the old version and which is the new. | |
978 | Please make the old version the first argument to diff, and the new | |
979 | version the second argument. And please give one version or the other a | |
980 | name that indicates whether it is the old version or your new changed | |
981 | one. | |
982 | ||
983 | @item | |
984 | Write the change log entries for your changes. This is both to save us | |
985 | the extra work of writing them, and to help explain your changes so we | |
986 | can understand them. | |
987 | ||
988 | The purpose of the change log is to show people where to find what was | |
989 | changed. So you need to be specific about what functions you changed; | |
990 | in large functions, it's often helpful to indicate where within the | |
991 | function the change was. | |
992 | ||
993 | On the other hand, once you have shown people where to find the change, | |
994 | you need not explain its purpose in the change log. Thus, if you add a | |
995 | new function, all you need to say about it is that it is new. If you | |
996 | feel that the purpose needs explaining, it probably does---but put the | |
997 | explanation in comments in the code. It will be more useful there. | |
998 | ||
21c80203 RS |
999 | Please read the @file{ChangeLog} files in the @file{src} and |
1000 | @file{lisp} directories to see what sorts of information to put in, | |
1001 | and to learn the style that we use. @xref{Change Log}. | |
6bf7aab6 DL |
1002 | |
1003 | @item | |
1004 | When you write the fix, keep in mind that we can't install a change that | |
1005 | would break other systems. Please think about what effect your change | |
1006 | will have if compiled on another type of system. | |
1007 | ||
1008 | Sometimes people send fixes that @emph{might} be an improvement in | |
1009 | general---but it is hard to be sure of this. It's hard to install | |
1010 | such changes because we have to study them very carefully. Of course, | |
1011 | a good explanation of the reasoning by which you concluded the change | |
1012 | was correct can help convince us. | |
1013 | ||
1014 | The safest changes are changes to the configuration files for a | |
1015 | particular machine. These are safe because they can't create new bugs | |
1016 | on other machines. | |
1017 | ||
1018 | Please help us keep up with the workload by designing the patch in a | |
1019 | form that is clearly safe to install. | |
1020 | @end itemize | |
1021 | ||
1022 | @node Contributing, Service, Bugs, Top | |
1023 | @section Contributing to Emacs Development | |
1024 | ||
1025 | If you would like to help pretest Emacs releases to assure they work | |
1026 | well, or if you would like to work on improving Emacs, please contact | |
b656e0f4 | 1027 | the maintainers at @email{emacs-devel@@gnu.org}. A pretester |
6bf7aab6 DL |
1028 | should be prepared to investigate bugs as well as report them. If you'd |
1029 | like to work on improving Emacs, please ask for suggested projects or | |
1030 | suggest your own ideas. | |
1031 | ||
1032 | If you have already written an improvement, please tell us about it. If | |
1033 | you have not yet started work, it is useful to contact | |
b656e0f4 | 1034 | @email{emacs-devel@@gnu.org} before you start; it might be |
6bf7aab6 DL |
1035 | possible to suggest ways to make your extension fit in better with the |
1036 | rest of Emacs. | |
1037 | ||
b656e0f4 NR |
1038 | The development version of Emacs can be downloaded from the CVS |
1039 | repository where it is actively maintained by a group of developers. | |
21c80203 RS |
1040 | See the Emacs project page |
1041 | @url{http://savannah.gnu.org/projects/emacs/} for details. | |
b656e0f4 | 1042 | |
0d6e9754 | 1043 | @node Service, Copying, Contributing, Top |
6bf7aab6 DL |
1044 | @section How To Get Help with GNU Emacs |
1045 | ||
1046 | If you need help installing, using or changing GNU Emacs, there are two | |
1047 | ways to find it: | |
1048 | ||
1049 | @itemize @bullet | |
1050 | @item | |
1051 | Send a message to the mailing list | |
60a96371 | 1052 | @email{help-gnu-emacs@@gnu.org}, or post your request on |
6bf7aab6 DL |
1053 | newsgroup @code{gnu.emacs.help}. (This mailing list and newsgroup |
1054 | interconnect, so it does not matter which one you use.) | |
1055 | ||
1056 | @item | |
1057 | Look in the service directory for someone who might help you for a fee. | |
1058 | The service directory is found in the file named @file{etc/SERVICE} in the | |
1059 | Emacs distribution. | |
1060 | @end itemize | |
ab5796a9 | 1061 | |
0d6e9754 LT |
1062 | @ifnottex |
1063 | @lowersections | |
1064 | @end ifnottex | |
1065 | ||
ab5796a9 MB |
1066 | @ignore |
1067 | arch-tag: c9cba76d-b2cb-4e0c-ae3f-19d5ef35817c | |
1068 | @end ignore |