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1 | @c This is part of the Emacs manual. |
2 | @c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc. | |
3 | @c See file emacs.texi for copying conditions. | |
4 | @iftex | |
5 | @chapter Dealing with Common Problems | |
6 | ||
7 | If you type an Emacs command you did not intend, the results are often | |
8 | mysterious. This chapter tells what you can do to cancel your mistake or | |
9 | recover from a mysterious situation. Emacs bugs and system crashes are | |
10 | also considered. | |
11 | @end iftex | |
12 | ||
13 | @node Quitting, Lossage, Customization, Top | |
14 | @section Quitting and Aborting | |
15 | @cindex quitting | |
16 | ||
17 | @table @kbd | |
18 | @item C-g | |
19 | @itemx C-@key{BREAK} (MS-DOS) | |
20 | Quit. Cancel running or partially typed command. | |
21 | @item C-] | |
22 | Abort innermost recursive editing level and cancel the command which | |
23 | invoked it (@code{abort-recursive-edit}). | |
24 | @item @key{ESC} @key{ESC} @key{ESC} | |
25 | Either quit or abort, whichever makes sense (@code{keyboard-escape-quit}). | |
26 | @item M-x top-level | |
27 | Abort all recursive editing levels that are currently executing. | |
28 | @item C-x u | |
29 | Cancel a previously made change in the buffer contents (@code{undo}). | |
30 | @end table | |
31 | ||
32 | There are two ways of canceling commands which are not finished | |
33 | executing: @dfn{quitting} with @kbd{C-g}, and @dfn{aborting} with | |
34 | @kbd{C-]} or @kbd{M-x top-level}. Quitting cancels a partially typed | |
35 | command or one which is already running. Aborting exits a recursive | |
36 | editing level and cancels the command that invoked the recursive edit. | |
37 | (@xref{Recursive Edit}.) | |
38 | ||
39 | @cindex quitting | |
40 | @kindex C-g | |
41 | Quitting with @kbd{C-g} is used for getting rid of a partially typed | |
42 | command, or a numeric argument that you don't want. It also stops a | |
43 | running command in the middle in a relatively safe way, so you can use | |
44 | it if you accidentally give a command which takes a long time. In | |
45 | particular, it is safe to quit out of killing; either your text will | |
46 | @emph{all} still be in the buffer, or it will @emph{all} be in the kill | |
47 | ring (or maybe both). Quitting an incremental search does special | |
48 | things documented under searching; in general, it may take two | |
49 | successive @kbd{C-g} characters to get out of a search | |
50 | (@pxref{Incremental Search}). | |
51 | ||
52 | On MS-DOS, the character @kbd{C-@key{BREAK}} serves as a quit character | |
53 | like @kbd{C-g}. The reason is that it is not feasible, on MS-DOS, to | |
54 | recognize @kbd{C-g} while a command is running, between interactions | |
55 | with the user. By contrast, it @emph{is} feasible to recognize | |
56 | @kbd{C-@key{BREAK}} at all times. @xref{MS-DOS Input}. | |
57 | ||
58 | @kbd{C-g} works by setting the variable @code{quit-flag} to @code{t} | |
59 | the instant @kbd{C-g} is typed; Emacs Lisp checks this variable | |
60 | frequently and quits if it is non-@code{nil}. @kbd{C-g} is only | |
61 | actually executed as a command if you type it while Emacs is waiting for | |
62 | input. | |
63 | ||
64 | If you quit with @kbd{C-g} a second time before the first @kbd{C-g} is | |
65 | recognized, you activate the ``emergency escape'' feature and return to | |
66 | the shell. @xref{Emergency Escape}. | |
67 | ||
68 | @cindex NFS and quitting | |
69 | There may be times when you cannot quit. When Emacs is waiting for | |
70 | the operating system to do something, quitting is impossible unless | |
71 | special pains are taken for the particular system call within Emacs | |
72 | where the waiting occurs. We have done this for the system calls that | |
73 | users are likely to want to quit from, but it's possible you will find | |
74 | another. In one very common case---waiting for file input or output | |
75 | using NFS---Emacs itself knows how to quit, but most NFS implementations | |
76 | simply do not allow user programs to stop waiting for NFS when the NFS | |
77 | server is hung. | |
78 | ||
79 | @cindex aborting recursive edit | |
80 | @findex abort-recursive-edit | |
81 | @kindex C-] | |
82 | Aborting with @kbd{C-]} (@code{abort-recursive-edit}) is used to get | |
83 | out of a recursive editing level and cancel the command which invoked | |
84 | it. Quitting with @kbd{C-g} does not do this, and could not do this, | |
85 | because it is used to cancel a partially typed command @emph{within} the | |
86 | recursive editing level. Both operations are useful. For example, if | |
87 | you are in a recursive edit and type @kbd{C-u 8} to enter a numeric | |
88 | argument, you can cancel that argument with @kbd{C-g} and remain in the | |
89 | recursive edit. | |
90 | ||
91 | @findex keyboard-escape-quit | |
92 | @kindex ESC ESC ESC | |
93 | The command @kbd{@key{ESC} @key{ESC} @key{ESC}} | |
94 | (@code{keyboard-escape-quit}) can either quit or abort. This key was | |
95 | defined because @key{ESC} is used to ``get out'' in many PC programs. | |
96 | It can cancel a prefix argument, clear a selected region, or get out of | |
97 | a Query Replace, like @kbd{C-g}. It can get out of the minibuffer or a | |
98 | recursive edit, like @kbd{C-]}. It can also get out of splitting the | |
99 | frame into multiple windows, like @kbd{C-x 1}. One thing it cannot do, | |
100 | however, is stop a command that is running. That's because it executes | |
101 | as an ordinary command, and Emacs doesn't notice it until it is ready | |
102 | for a command. | |
103 | ||
104 | @findex top-level | |
105 | The command @kbd{M-x top-level} is equivalent to ``enough'' @kbd{C-]} | |
106 | commands to get you out of all the levels of recursive edits that you | |
107 | are in. @kbd{C-]} gets you out one level at a time, but @kbd{M-x | |
108 | top-level} goes out all levels at once. Both @kbd{C-]} and @kbd{M-x | |
109 | top-level} are like all other commands, and unlike @kbd{C-g}, in that | |
110 | they take effect only when Emacs is ready for a command. @kbd{C-]} is | |
111 | an ordinary key and has its meaning only because of its binding in the | |
112 | keymap. @xref{Recursive Edit}. | |
113 | ||
114 | @kbd{C-x u} (@code{undo}) is not strictly speaking a way of canceling | |
115 | a command, but you can think of it as canceling a command that already | |
116 | finished executing. @xref{Undo}. | |
117 | ||
118 | @node Lossage, Bugs, Quitting, Top | |
119 | @section Dealing with Emacs Trouble | |
120 | ||
121 | This section describes various conditions in which Emacs fails to work | |
122 | normally, and how to recognize them and correct them. | |
123 | ||
124 | @menu | |
125 | * DEL Gets Help:: What to do if @key{DEL} doesn't delete. | |
126 | * Stuck Recursive:: `[...]' in mode line around the parentheses. | |
127 | * Screen Garbled:: Garbage on the screen. | |
128 | * Text Garbled:: Garbage in the text. | |
129 | * Unasked-for Search:: Spontaneous entry to incremental search. | |
130 | * Memory Full:: How to cope when you run out of memory. | |
131 | * After a Crash:: Recovering editing in an Emacs session that crashed. | |
132 | * Emergency Escape:: Emergency escape--- | |
133 | What to do if Emacs stops responding. | |
134 | * Total Frustration:: When you are at your wits' end. | |
135 | @end menu | |
136 | ||
137 | @node DEL Gets Help | |
138 | @subsection If @key{DEL} Fails to Delete | |
139 | ||
140 | If you find that @key{DEL} enters Help like @kbd{Control-h} instead of | |
141 | deleting a character, your terminal is sending the wrong code for | |
142 | @key{DEL}. You can work around this problem by changing the keyboard | |
143 | translation table (@pxref{Keyboard Translations}). | |
144 | ||
145 | @node Stuck Recursive | |
146 | @subsection Recursive Editing Levels | |
147 | ||
148 | Recursive editing levels are important and useful features of Emacs, but | |
149 | they can seem like malfunctions to the user who does not understand them. | |
150 | ||
151 | If the mode line has square brackets @samp{[@dots{}]} around the parentheses | |
152 | that contain the names of the major and minor modes, you have entered a | |
153 | recursive editing level. If you did not do this on purpose, or if you | |
154 | don't understand what that means, you should just get out of the recursive | |
155 | editing level. To do so, type @kbd{M-x top-level}. This is called getting | |
156 | back to top level. @xref{Recursive Edit}. | |
157 | ||
158 | @node Screen Garbled | |
159 | @subsection Garbage on the Screen | |
160 | ||
161 | If the data on the screen looks wrong, the first thing to do is see | |
162 | whether the text is really wrong. Type @kbd{C-l}, to redisplay the | |
163 | entire screen. If the screen appears correct after this, the problem | |
164 | was entirely in the previous screen update. (Otherwise, see @ref{Text | |
165 | Garbled}.) | |
166 | ||
167 | Display updating problems often result from an incorrect termcap entry | |
168 | for the terminal you are using. The file @file{etc/TERMS} in the Emacs | |
169 | distribution gives the fixes for known problems of this sort. | |
170 | @file{INSTALL} contains general advice for these problems in one of its | |
171 | sections. Very likely there is simply insufficient padding for certain | |
172 | display operations. To investigate the possibility that you have this sort | |
173 | of problem, try Emacs on another terminal made by a different manufacturer. | |
174 | If problems happen frequently on one kind of terminal but not another kind, | |
175 | it is likely to be a bad termcap entry, though it could also be due to a | |
176 | bug in Emacs that appears for terminals that have or that lack specific | |
177 | features. | |
178 | ||
179 | @node Text Garbled | |
180 | @subsection Garbage in the Text | |
181 | ||
182 | If @kbd{C-l} shows that the text is wrong, try undoing the changes to it | |
183 | using @kbd{C-x u} until it gets back to a state you consider correct. Also | |
184 | try @kbd{C-h l} to find out what command you typed to produce the observed | |
185 | results. | |
186 | ||
187 | If a large portion of text appears to be missing at the beginning or | |
188 | end of the buffer, check for the word @samp{Narrow} in the mode line. | |
189 | If it appears, the text you don't see is probably still present, but | |
190 | temporarily off-limits. To make it accessible again, type @kbd{C-x n | |
191 | w}. @xref{Narrowing}. | |
192 | ||
193 | @node Unasked-for Search | |
194 | @subsection Spontaneous Entry to Incremental Search | |
195 | ||
196 | If Emacs spontaneously displays @samp{I-search:} at the bottom of the | |
197 | screen, it means that the terminal is sending @kbd{C-s} and @kbd{C-q} | |
198 | according to the poorly designed xon/xoff ``flow control'' protocol. | |
199 | ||
200 | If this happens to you, your best recourse is to put the terminal in a | |
201 | mode where it will not use flow control, or give it so much padding that | |
202 | it will never send a @kbd{C-s}. (One way to increase the amount of | |
203 | padding is to set the variable @code{baud-rate} to a larger value. Its | |
204 | value is the terminal output speed, measured in the conventional units | |
205 | of baud.) | |
206 | ||
207 | @cindex flow control | |
208 | @cindex xon-xoff | |
209 | @findex enable-flow-control | |
210 | If you don't succeed in turning off flow control, the next best thing | |
211 | is to tell Emacs to cope with it. To do this, call the function | |
212 | @code{enable-flow-control}. | |
213 | ||
214 | @findex enable-flow-control-on | |
215 | Typically there are particular terminal types with which you must use | |
216 | flow control. You can conveniently ask for flow control on those | |
217 | terminal types only, using @code{enable-flow-control-on}. For example, | |
218 | if you find you must use flow control on VT-100 and H19 terminals, put | |
219 | the following in your @file{.emacs} file: | |
220 | ||
221 | @example | |
222 | (enable-flow-control-on "vt100" "h19") | |
223 | @end example | |
224 | ||
225 | When flow control is enabled, you must type @kbd{C-\} to get the | |
226 | effect of a @kbd{C-s}, and type @kbd{C-^} to get the effect of a | |
227 | @kbd{C-q}. (These aliases work by means of keyboard translations; see | |
228 | @ref{Keyboard Translations}.) | |
229 | ||
230 | @node Memory Full | |
231 | @subsection Running out of Memory | |
232 | @cindex memory full | |
233 | @cindex out of memory | |
234 | ||
235 | If you get the error message @samp{Virtual memory exceeded}, save your | |
236 | modified buffers with @kbd{C-x s}. This method of saving them has the | |
237 | smallest need for additional memory. Emacs keeps a reserve of memory | |
238 | which it makes available when this error happens; that should be enough | |
239 | to enable @kbd{C-x s} to complete its work. | |
240 | ||
241 | Once you have saved your modified buffers, you can exit this Emacs job | |
242 | and start another, or you can use @kbd{M-x kill-some-buffers} to free | |
243 | space in the current Emacs job. If you kill buffers containing a | |
244 | substantial amount of text, you can safely go on editing. Emacs refills | |
245 | its memory reserve automatically when it sees sufficient free space | |
246 | available, in case you run out of memory another time. | |
247 | ||
248 | Do not use @kbd{M-x buffer-menu} to save or kill buffers when you run | |
249 | out of memory, because the buffer menu needs a fair amount memory | |
250 | itself, and the reserve supply may not be enough. | |
251 | ||
252 | @node After a Crash | |
253 | @subsection Recovery After a Crash | |
254 | ||
255 | If Emacs or the computer crashes, you can recover the files you were | |
256 | editing at the time of the crash from their auto-save files. To do | |
257 | this, start Emacs again and type the command @kbd{M-x recover-session}. | |
258 | ||
259 | This command initially displays a buffer which lists interrupted | |
260 | session files, each with its date. You must choose which session to | |
261 | recover from. Typically the one you want is the most recent one. Move | |
262 | point to the one you choose, and type @kbd{C-c C-c}. | |
263 | ||
264 | Then @code{recover-session} asks about each of the files that you were | |
265 | editing during that session; it asks whether to recover that file. If | |
266 | you answer @kbd{y} for a file, it shows the dates of that file and its | |
267 | auto-save file, then asks once again whether to recover that file. For | |
268 | the second question, you must confirm with @kbd{yes}. If you do, Emacs | |
269 | visits the file but gets the text from the auto-save file. | |
270 | ||
271 | When @code{recover-session} is done, the files you've chosen to | |
272 | recover are present in Emacs buffers. You should then save them. Only | |
273 | this---saving them---updates the files themselves. | |
274 | ||
275 | @node Emergency Escape | |
276 | @subsection Emergency Escape | |
277 | ||
278 | Because at times there have been bugs causing Emacs to loop without | |
279 | checking @code{quit-flag}, a special feature causes Emacs to be suspended | |
280 | immediately if you type a second @kbd{C-g} while the flag is already set, | |
281 | so you can always get out of GNU Emacs. Normally Emacs recognizes and | |
282 | clears @code{quit-flag} (and quits!) quickly enough to prevent this from | |
283 | happening. (On MS-DOS and compatible systems, type @kbd{C-@key{BREAK}} | |
284 | twice.) | |
285 | ||
286 | When you resume Emacs after a suspension caused by multiple @kbd{C-g}, it | |
287 | asks two questions before going back to what it had been doing: | |
288 | ||
289 | @example | |
290 | Auto-save? (y or n) | |
291 | Abort (and dump core)? (y or n) | |
292 | @end example | |
293 | ||
294 | @noindent | |
295 | Answer each one with @kbd{y} or @kbd{n} followed by @key{RET}. | |
296 | ||
297 | Saying @kbd{y} to @samp{Auto-save?} causes immediate auto-saving of all | |
298 | modified buffers in which auto-saving is enabled. | |
299 | ||
300 | Saying @kbd{y} to @samp{Abort (and dump core)?} causes an illegal instruction to be | |
301 | executed, dumping core. This is to enable a wizard to figure out why Emacs | |
302 | was failing to quit in the first place. Execution does not continue | |
303 | after a core dump. If you answer @kbd{n}, execution does continue. With | |
304 | luck, GNU Emacs will ultimately check @code{quit-flag} and quit normally. | |
305 | If not, and you type another @kbd{C-g}, it is suspended again. | |
306 | ||
307 | If Emacs is not really hung, just slow, you may invoke the double | |
308 | @kbd{C-g} feature without really meaning to. Then just resume and answer | |
309 | @kbd{n} to both questions, and you will arrive at your former state. | |
310 | Presumably the quit you requested will happen soon. | |
311 | ||
312 | The double-@kbd{C-g} feature is turned off when Emacs is running under | |
313 | the X Window System, since you can use the window manager to kill Emacs | |
314 | or to create another window and run another program. | |
315 | ||
316 | On MS-DOS and compatible systems, the emergency escape feature is | |
317 | sometimes unavailable, even if you press @kbd{C-@key{BREAK}} twice, when | |
318 | some system call (MS-DOS or BIOS) hangs, or when Emacs is stuck in a | |
319 | very tight endless loop (in C code, @strong{not} in Lisp code). | |
320 | ||
321 | @node Total Frustration | |
322 | @subsection Help for Total Frustration | |
323 | @cindex Eliza | |
324 | @cindex doctor | |
325 | ||
326 | If using Emacs (or something else) becomes terribly frustrating and none | |
327 | of the techniques described above solve the problem, Emacs can still help | |
328 | you. | |
329 | ||
330 | First, if the Emacs you are using is not responding to commands, type | |
331 | @kbd{C-g C-g} to get out of it and then start a new one. | |
332 | ||
333 | @findex doctor | |
334 | Second, type @kbd{M-x doctor @key{RET}}. | |
335 | ||
336 | The doctor will help you feel better. Each time you say something to | |
337 | the doctor, you must end it by typing @key{RET} @key{RET}. This lets | |
338 | the doctor know you are finished. | |
339 | ||
340 | @node Bugs, Contributing, Lossage, Top | |
341 | @section Reporting Bugs | |
342 | ||
343 | @cindex bugs | |
344 | Sometimes you will encounter a bug in Emacs. Although we cannot | |
345 | promise we can or will fix the bug, and we might not even agree that it | |
346 | is a bug, we want to hear about problems you encounter. Often we agree | |
347 | they are bugs and want to fix them. | |
348 | ||
349 | To make it possible for us to fix a bug, you must report it. In order | |
350 | to do so effectively, you must know when and how to do it. | |
351 | ||
352 | @menu | |
353 | * Criteria: Bug Criteria. Have you really found a bug? | |
354 | * Understanding Bug Reporting:: How to report a bug effectively. | |
355 | * Checklist:: Steps to follow for a good bug report. | |
356 | * Sending Patches:: How to send a patch for GNU Emacs. | |
357 | @end menu | |
358 | ||
359 | @node Bug Criteria | |
360 | @subsection When Is There a Bug | |
361 | ||
362 | If Emacs executes an illegal instruction, or dies with an operating | |
363 | system error message that indicates a problem in the program (as opposed to | |
364 | something like ``disk full''), then it is certainly a bug. | |
365 | ||
366 | If Emacs updates the display in a way that does not correspond to what is | |
367 | in the buffer, then it is certainly a bug. If a command seems to do the | |
368 | wrong thing but the problem corrects itself if you type @kbd{C-l}, it is a | |
369 | case of incorrect display updating. | |
370 | ||
371 | Taking forever to complete a command can be a bug, but you must make | |
372 | certain that it was really Emacs's fault. Some commands simply take a | |
373 | long time. Type @kbd{C-g} (@kbd{C-@key{BREAK}} on MS-DOS) and then @kbd{C-h l} | |
374 | to see whether the input Emacs received was what you intended to type; | |
375 | if the input was such that you @emph{know} it should have been processed | |
376 | quickly, report a bug. If you don't know whether the command should | |
377 | take a long time, find out by looking in the manual or by asking for | |
378 | assistance. | |
379 | ||
380 | If a command you are familiar with causes an Emacs error message in a | |
381 | case where its usual definition ought to be reasonable, it is probably a | |
382 | bug. | |
383 | ||
384 | If a command does the wrong thing, that is a bug. But be sure you know | |
385 | for certain what it ought to have done. If you aren't familiar with the | |
386 | command, or don't know for certain how the command is supposed to work, | |
387 | then it might actually be working right. Rather than jumping to | |
388 | conclusions, show the problem to someone who knows for certain. | |
389 | ||
390 | Finally, a command's intended definition may not be best for editing | |
391 | with. This is a very important sort of problem, but it is also a matter of | |
392 | judgment. Also, it is easy to come to such a conclusion out of ignorance | |
393 | of some of the existing features. It is probably best not to complain | |
394 | about such a problem until you have checked the documentation in the usual | |
395 | ways, feel confident that you understand it, and know for certain that what | |
396 | you want is not available. If you are not sure what the command is | |
397 | supposed to do after a careful reading of the manual, check the index and | |
398 | glossary for any terms that may be unclear. | |
399 | ||
400 | If after careful rereading of the manual you still do not understand | |
401 | what the command should do, that indicates a bug in the manual, which | |
402 | you should report. The manual's job is to make everything clear to | |
403 | people who are not Emacs experts---including you. It is just as | |
404 | important to report documentation bugs as program bugs. | |
405 | ||
406 | If the on-line documentation string of a function or variable disagrees | |
407 | with the manual, one of them must be wrong; that is a bug. | |
408 | ||
409 | @node Understanding Bug Reporting | |
410 | @subsection Understanding Bug Reporting | |
411 | ||
412 | @findex emacs-version | |
413 | When you decide that there is a bug, it is important to report it and to | |
414 | report it in a way which is useful. What is most useful is an exact | |
415 | description of what commands you type, starting with the shell command to | |
416 | run Emacs, until the problem happens. | |
417 | ||
418 | The most important principle in reporting a bug is to report | |
419 | @emph{facts}. Hypotheses and verbal descriptions are no substitute for | |
420 | the detailed raw data. Reporting the facts is straightforward, but many | |
421 | people strain to posit explanations and report them instead of the | |
422 | facts. If the explanations are based on guesses about how Emacs is | |
423 | implemented, they will be useless; meanwhile, lacking the facts, we will | |
424 | have no real information about the bug. | |
425 | ||
426 | For example, suppose that you type @kbd{C-x C-f /glorp/baz.ugh | |
427 | @key{RET}}, visiting a file which (you know) happens to be rather large, | |
428 | and Emacs displayed @samp{I feel pretty today}. The best way to report | |
429 | the bug is with a sentence like the preceding one, because it gives all | |
430 | the facts. | |
431 | ||
432 | A bad way would be to assume that the problem is due to the size of | |
433 | the file and say, ``I visited a large file, and Emacs displayed @samp{I | |
434 | feel pretty today}.'' This is what we mean by ``guessing | |
435 | explanations.'' The problem is just as likely to be due to the fact | |
436 | that there is a @samp{z} in the file name. If this is so, then when we | |
437 | got your report, we would try out the problem with some ``large file,'' | |
438 | probably with no @samp{z} in its name, and not see any problem. There | |
439 | is no way in the world that we could guess that we should try visiting a | |
440 | file with a @samp{z} in its name. | |
441 | ||
442 | Alternatively, the problem might be due to the fact that the file starts | |
443 | with exactly 25 spaces. For this reason, you should make sure that you | |
444 | inform us of the exact contents of any file that is needed to reproduce the | |
445 | bug. What if the problem only occurs when you have typed the @kbd{C-x C-a} | |
446 | command previously? This is why we ask you to give the exact sequence of | |
447 | characters you typed since starting the Emacs session. | |
448 | ||
449 | You should not even say ``visit a file'' instead of @kbd{C-x C-f} unless | |
450 | you @emph{know} that it makes no difference which visiting command is used. | |
451 | Similarly, rather than saying ``if I have three characters on the line,'' | |
452 | say ``after I type @kbd{@key{RET} A B C @key{RET} C-p},'' if that is | |
453 | the way you entered the text.@refill | |
454 | ||
455 | So please don't guess any explanations when you report a bug. If you | |
456 | want to actually @emph{debug} the problem, and report explanations that | |
457 | are more than guesses, that is useful---but please include the facts as | |
458 | well. | |
459 | ||
460 | @node Checklist | |
461 | @subsection Checklist for Bug Reports | |
462 | ||
463 | @cindex reporting bugs | |
464 | The best way to send a bug report is to mail it electronically to the | |
f8b3de7e GM |
465 | Emacs maintainers at @samp{bug-gnu-emacs@@gnu.org}, or to |
466 | @samp{emacs-pretest-bug@@gnu.org} if you are pretesting an Emacs beta | |
467 | release. (If you want to suggest a change as an improvement, use the | |
468 | same address.) | |
6bf7aab6 DL |
469 | |
470 | If you'd like to read the bug reports, you can find them on the | |
471 | newsgroup @samp{gnu.emacs.bug}; keep in mind, however, that as a | |
472 | spectator you should not criticize anything about what you see there. | |
473 | The purpose of bug reports is to give information to the Emacs | |
474 | maintainers. Spectators are welcome only as long as they do not | |
475 | interfere with this. In particular, some bug reports contain large | |
476 | amounts of data; spectators should not complain about this. | |
477 | ||
478 | Please do not post bug reports using netnews; mail is more reliable | |
479 | than netnews about reporting your correct address, which we may need in | |
480 | order to ask you for more information. | |
481 | ||
482 | If you can't send electronic mail, then mail the bug report on paper | |
483 | or machine-readable media to this address: | |
484 | ||
485 | @format | |
486 | GNU Emacs Bugs | |
487 | Free Software Foundation | |
488 | 59 Temple Place, Suite 330 | |
489 | Boston, MA 02111-1307 USA | |
490 | @end format | |
491 | ||
492 | We do not promise to fix the bug; but if the bug is serious, | |
493 | or ugly, or easy to fix, chances are we will want to. | |
494 | ||
495 | @findex report-emacs-bug | |
496 | A convenient way to send a bug report for Emacs is to use the command | |
497 | @kbd{M-x report-emacs-bug}. This sets up a mail buffer (@pxref{Sending | |
498 | Mail}) and automatically inserts @emph{some} of the essential | |
499 | information. However, it cannot supply all the necessary information; | |
500 | you should still read and follow the guidelines below, so you can enter | |
501 | the other crucial information by hand before you send the message. | |
502 | ||
503 | To enable maintainers to investigate a bug, your report | |
504 | should include all these things: | |
505 | ||
506 | @itemize @bullet | |
507 | @item | |
508 | The version number of Emacs. Without this, we won't know whether there | |
509 | is any point in looking for the bug in the current version of GNU | |
510 | Emacs. | |
511 | ||
512 | You can get the version number by typing @kbd{M-x emacs-version | |
513 | @key{RET}}. If that command does not work, you probably have something | |
514 | other than GNU Emacs, so you will have to report the bug somewhere | |
515 | else. | |
516 | ||
517 | @item | |
518 | The type of machine you are using, and the operating system name and | |
519 | version number. @kbd{M-x emacs-version @key{RET}} provides this | |
520 | information too. Copy its output from the @samp{*Messages*} buffer, so | |
521 | that you get it all and get it accurately. | |
522 | ||
523 | @item | |
524 | The operands given to the @code{configure} command when Emacs was | |
525 | installed. | |
526 | ||
527 | @item | |
528 | A complete list of any modifications you have made to the Emacs source. | |
529 | (We may not have time to investigate the bug unless it happens in an | |
530 | unmodified Emacs. But if you've made modifications and you don't tell | |
531 | us, you are sending us on a wild goose chase.) | |
532 | ||
533 | Be precise about these changes. A description in English is not | |
534 | enough---send a context diff for them. | |
535 | ||
536 | Adding files of your own, or porting to another machine, is a | |
537 | modification of the source. | |
538 | ||
539 | @item | |
540 | Details of any other deviations from the standard procedure for installing | |
541 | GNU Emacs. | |
542 | ||
543 | @item | |
544 | The complete text of any files needed to reproduce the bug. | |
545 | ||
546 | If you can tell us a way to cause the problem without visiting any files, | |
547 | please do so. This makes it much easier to debug. If you do need files, | |
548 | make sure you arrange for us to see their exact contents. For example, it | |
549 | can often matter whether there are spaces at the ends of lines, or a | |
550 | newline after the last line in the buffer (nothing ought to care whether | |
551 | the last line is terminated, but try telling the bugs that). | |
552 | ||
553 | @item | |
554 | The precise commands we need to type to reproduce the bug. | |
555 | ||
556 | @findex open-dribble-file | |
557 | @cindex dribble file | |
558 | The easy way to record the input to Emacs precisely is to write a | |
559 | dribble file. To start the file, execute the Lisp expression | |
560 | ||
561 | @example | |
562 | (open-dribble-file "~/dribble") | |
563 | @end example | |
564 | ||
565 | @noindent | |
566 | using @kbd{M-:} or from the @samp{*scratch*} buffer just after | |
567 | starting Emacs. From then on, Emacs copies all your input to the | |
568 | specified dribble file until the Emacs process is killed. | |
569 | ||
570 | @item | |
571 | @findex open-termscript | |
572 | @cindex termscript file | |
60a96371 | 573 | @cindex @env{TERM} environment variable |
6bf7aab6 | 574 | For possible display bugs, the terminal type (the value of environment |
60a96371 | 575 | variable @env{TERM}), the complete termcap entry for the terminal from |
6bf7aab6 DL |
576 | @file{/etc/termcap} (since that file is not identical on all machines), |
577 | and the output that Emacs actually sent to the terminal. | |
578 | ||
579 | The way to collect the terminal output is to execute the Lisp expression | |
580 | ||
581 | @example | |
582 | (open-termscript "~/termscript") | |
583 | @end example | |
584 | ||
585 | @noindent | |
586 | using @kbd{M-:} or from the @samp{*scratch*} buffer just after | |
587 | starting Emacs. From then on, Emacs copies all terminal output to the | |
588 | specified termscript file as well, until the Emacs process is killed. | |
589 | If the problem happens when Emacs starts up, put this expression into | |
590 | your @file{.emacs} file so that the termscript file will be open when | |
591 | Emacs displays the screen for the first time. | |
592 | ||
593 | Be warned: it is often difficult, and sometimes impossible, to fix a | |
594 | terminal-dependent bug without access to a terminal of the type that | |
595 | stimulates the bug.@refill | |
596 | ||
597 | @item | |
598 | A description of what behavior you observe that you believe is | |
599 | incorrect. For example, ``The Emacs process gets a fatal signal,'' or, | |
600 | ``The resulting text is as follows, which I think is wrong.'' | |
601 | ||
602 | Of course, if the bug is that Emacs gets a fatal signal, then one can't | |
603 | miss it. But if the bug is incorrect text, the maintainer might fail to | |
604 | notice what is wrong. Why leave it to chance? | |
605 | ||
606 | Even if the problem you experience is a fatal signal, you should still | |
607 | say so explicitly. Suppose something strange is going on, such as, your | |
608 | copy of the source is out of sync, or you have encountered a bug in the | |
609 | C library on your system. (This has happened!) Your copy might crash | |
610 | and the copy here might not. If you @emph{said} to expect a crash, then | |
611 | when Emacs here fails to crash, we would know that the bug was not | |
612 | happening. If you don't say to expect a crash, then we would not know | |
613 | whether the bug was happening---we would not be able to draw any | |
614 | conclusion from our observations. | |
615 | ||
616 | @item | |
617 | If the manifestation of the bug is an Emacs error message, it is | |
618 | important to report the precise text of the error message, and a | |
619 | backtrace showing how the Lisp program in Emacs arrived at the error. | |
620 | ||
621 | To get the error message text accurately, copy it from the | |
622 | @samp{*Messages*} buffer into the bug report. Copy all of it, not just | |
623 | part. | |
624 | ||
625 | To make a backtrace for the error, evaluate the Lisp expression | |
626 | @code{(setq @w{debug-on-error t})} before the error happens (that is to | |
627 | say, you must execute that expression and then make the bug happen). | |
628 | This causes the error to run the Lisp debugger, which shows you a | |
629 | backtrace. Copy the text of the debugger's backtrace into the bug | |
630 | report. | |
631 | ||
632 | This use of the debugger is possible only if you know how to make the | |
633 | bug happen again. If you can't make it happen again, at least copy | |
634 | the whole error message. | |
635 | ||
636 | @item | |
637 | Check whether any programs you have loaded into the Lisp world, | |
638 | including your @file{.emacs} file, set any variables that may affect the | |
639 | functioning of Emacs. Also, see whether the problem happens in a | |
640 | freshly started Emacs without loading your @file{.emacs} file (start | |
641 | Emacs with the @code{-q} switch to prevent loading the init file). If | |
642 | the problem does @emph{not} occur then, you must report the precise | |
643 | contents of any programs that you must load into the Lisp world in order | |
644 | to cause the problem to occur. | |
645 | ||
646 | @item | |
647 | If the problem does depend on an init file or other Lisp programs that | |
648 | are not part of the standard Emacs system, then you should make sure it | |
649 | is not a bug in those programs by complaining to their maintainers | |
650 | first. After they verify that they are using Emacs in a way that is | |
651 | supposed to work, they should report the bug. | |
652 | ||
653 | @item | |
654 | If you wish to mention something in the GNU Emacs source, show the line | |
655 | of code with a few lines of context. Don't just give a line number. | |
656 | ||
657 | The line numbers in the development sources don't match those in your | |
658 | sources. It would take extra work for the maintainers to determine what | |
659 | code is in your version at a given line number, and we could not be | |
660 | certain. | |
661 | ||
662 | @item | |
663 | Additional information from a C debugger such as GDB might enable | |
664 | someone to find a problem on a machine which he does not have available. | |
665 | If you don't know how to use GDB, please read the GDB manual---it is not | |
666 | very long, and using GDB is easy. You can find the GDB distribution, | |
667 | including the GDB manual in online form, in most of the same places you | |
668 | can find the Emacs distribution. To run Emacs under GDB, you should | |
669 | switch to the @file{src} subdirectory in which Emacs was compiled, then | |
670 | do @samp{gdb emacs}. It is important for the directory @file{src} to be | |
671 | current so that GDB will read the @file{.gdbinit} file in this | |
672 | directory. | |
673 | ||
674 | However, you need to think when you collect the additional information | |
675 | if you want it to show what causes the bug. | |
676 | ||
677 | @cindex backtrace for bug reports | |
678 | For example, many people send just a backtrace, but that is not very | |
679 | useful by itself. A simple backtrace with arguments often conveys | |
680 | little about what is happening inside GNU Emacs, because most of the | |
681 | arguments listed in the backtrace are pointers to Lisp objects. The | |
682 | numeric values of these pointers have no significance whatever; all that | |
683 | matters is the contents of the objects they point to (and most of the | |
684 | contents are themselves pointers). | |
685 | ||
686 | @findex debug_print | |
687 | To provide useful information, you need to show the values of Lisp | |
688 | objects in Lisp notation. Do this for each variable which is a Lisp | |
689 | object, in several stack frames near the bottom of the stack. Look at | |
690 | the source to see which variables are Lisp objects, because the debugger | |
691 | thinks of them as integers. | |
692 | ||
693 | To show a variable's value in Lisp syntax, first print its value, then | |
694 | use the user-defined GDB command @code{pr} to print the Lisp object in | |
695 | Lisp syntax. (If you must use another debugger, call the function | |
696 | @code{debug_print} with the object as an argument.) The @code{pr} | |
697 | command is defined by the file @file{.gdbinit}, and it works only if you | |
698 | are debugging a running process (not with a core dump). | |
699 | ||
700 | To make Lisp errors stop Emacs and return to GDB, put a breakpoint at | |
701 | @code{Fsignal}. | |
702 | ||
8389e1e2 GM |
703 | For a short listing of Lisp functions running, type the GDB |
704 | command @code{xbacktrace}. | |
705 | ||
706 | If you want to examine Lisp function arguments, move up the stack, and | |
707 | each time you get to a frame for the function @code{Ffuncall}, type | |
708 | these GDB commands: | |
6bf7aab6 DL |
709 | |
710 | @example | |
711 | p *args | |
712 | pr | |
713 | @end example | |
714 | ||
715 | @noindent | |
716 | To print the first argument that the function received, use these | |
717 | commands: | |
718 | ||
719 | @example | |
720 | p args[1] | |
721 | pr | |
722 | @end example | |
723 | ||
724 | @noindent | |
725 | You can print the other arguments likewise. The argument @code{nargs} | |
726 | of @code{Ffuncall} says how many arguments @code{Ffuncall} received; | |
727 | these include the Lisp function itself and the arguments for that | |
728 | function. | |
729 | ||
730 | The file @file{.gdbinit} defines several other commands that are useful | |
731 | for examining the data types and contents of Lisp objects. Their names | |
732 | begin with @samp{x}. These commands work at a lower level than | |
733 | @code{pr}, and are less convenient, but they may work even when | |
734 | @code{pr} does not, such as when debugging a core dump or when Emacs has | |
735 | had a fatal signal. | |
736 | ||
737 | @item | |
738 | If the symptom of the bug is that Emacs fails to respond, don't assume | |
739 | Emacs is ``hung''---it may instead be in an infinite loop. To find out | |
740 | which, make the problem happen under GDB and stop Emacs once it is not | |
741 | responding. (If Emacs is using X Windows directly, you can stop Emacs | |
742 | by typing @kbd{C-z} at the GDB job.) Then try stepping with | |
743 | @samp{step}. If Emacs is hung, the @samp{step} command won't return. | |
744 | If it is looping, @samp{step} will return. | |
745 | ||
746 | If this shows Emacs is hung in a system call, stop it again and examine | |
747 | the arguments of the call. In your bug report, state exactly where in | |
748 | the source the system call is, and what the arguments are. | |
749 | ||
750 | If Emacs is in an infinite loop, please determine where the loop starts | |
751 | and ends. The easiest way to do this is to use the GDB command | |
752 | @samp{finish}. Each time you use it, Emacs resumes execution until it | |
753 | exits one stack frame. Keep typing @samp{finish} until it doesn't | |
754 | return---that means the infinite loop is in the stack frame which you | |
755 | just tried to finish. | |
756 | ||
757 | Stop Emacs again, and use @samp{finish} repeatedly again until you get | |
758 | @emph{back to} that frame. Then use @samp{next} to step through that | |
759 | frame. By stepping, you will see where the loop starts and ends. Also | |
760 | please examine the data being used in the loop and try to determine why | |
761 | the loop does not exit when it should. Include all of this information | |
762 | in your bug report. | |
763 | @end itemize | |
764 | ||
765 | Here are some things that are not necessary in a bug report: | |
766 | ||
767 | @itemize @bullet | |
768 | @item | |
769 | A description of the envelope of the bug---this is not necessary for a | |
770 | reproducible bug. | |
771 | ||
772 | Often people who encounter a bug spend a lot of time investigating | |
773 | which changes to the input file will make the bug go away and which | |
774 | changes will not affect it. | |
775 | ||
776 | This is often time-consuming and not very useful, because the way we | |
777 | will find the bug is by running a single example under the debugger with | |
778 | breakpoints, not by pure deduction from a series of examples. You might | |
779 | as well save time by not searching for additional examples. | |
780 | ||
781 | Of course, if you can find a simpler example to report @emph{instead} of | |
782 | the original one, that is a convenience. Errors in the output will be | |
783 | easier to spot, running under the debugger will take less time, etc. | |
784 | ||
785 | However, simplification is not vital; if you can't do this or don't have | |
786 | time to try, please report the bug with your original test case. | |
787 | ||
788 | @item | |
789 | A system-call trace of Emacs execution. | |
790 | ||
791 | System-call traces are very useful for certain special kinds of | |
792 | debugging, but in most cases they give little useful information. It is | |
793 | therefore strange that many people seem to think that @emph{the} way to | |
794 | report information about a crash is to send a system-call trace. Perhaps | |
795 | this is a habit formed from experience debugging programs that don't | |
796 | have source code or debugging symbols. | |
797 | ||
798 | In most programs, a backtrace is normally far, far more informative than | |
799 | a system-call trace. Even in Emacs, a simple backtrace is generally | |
800 | more informative, though to give full information you should supplement | |
801 | the backtrace by displaying variable values and printing them as Lisp | |
802 | objects with @code{pr} (see above). | |
803 | ||
804 | @item | |
805 | A patch for the bug. | |
806 | ||
807 | A patch for the bug is useful if it is a good one. But don't omit the | |
808 | other information that a bug report needs, such as the test case, on the | |
809 | assumption that a patch is sufficient. We might see problems with your | |
810 | patch and decide to fix the problem another way, or we might not | |
811 | understand it at all. And if we can't understand what bug you are | |
812 | trying to fix, or why your patch should be an improvement, we mustn't | |
813 | install it. | |
814 | ||
815 | @ifinfo | |
816 | @xref{Sending Patches}, for guidelines on how to make it easy for us to | |
817 | understand and install your patches. | |
818 | @end ifinfo | |
819 | ||
820 | @item | |
821 | A guess about what the bug is or what it depends on. | |
822 | ||
823 | Such guesses are usually wrong. Even experts can't guess right about | |
824 | such things without first using the debugger to find the facts. | |
825 | @end itemize | |
826 | ||
827 | @node Sending Patches | |
828 | @subsection Sending Patches for GNU Emacs | |
829 | ||
830 | @cindex sending patches for GNU Emacs | |
831 | @cindex patches, sending | |
832 | If you would like to write bug fixes or improvements for GNU Emacs, | |
833 | that is very helpful. When you send your changes, please follow these | |
834 | guidelines to make it easy for the maintainers to use them. If you | |
835 | don't follow these guidelines, your information might still be useful, | |
836 | but using it will take extra work. Maintaining GNU Emacs is a lot of | |
837 | work in the best of circumstances, and we can't keep up unless you do | |
838 | your best to help. | |
839 | ||
840 | @itemize @bullet | |
841 | @item | |
842 | Send an explanation with your changes of what problem they fix or what | |
843 | improvement they bring about. For a bug fix, just include a copy of the | |
844 | bug report, and explain why the change fixes the bug. | |
845 | ||
846 | (Referring to a bug report is not as good as including it, because then | |
847 | we will have to look it up, and we have probably already deleted it if | |
848 | we've already fixed the bug.) | |
849 | ||
850 | @item | |
851 | Always include a proper bug report for the problem you think you have | |
852 | fixed. We need to convince ourselves that the change is right before | |
853 | installing it. Even if it is correct, we might have trouble | |
854 | understanding it if we don't have a way to reproduce the problem. | |
855 | ||
856 | @item | |
857 | Include all the comments that are appropriate to help people reading the | |
858 | source in the future understand why this change was needed. | |
859 | ||
860 | @item | |
861 | Don't mix together changes made for different reasons. | |
862 | Send them @emph{individually}. | |
863 | ||
864 | If you make two changes for separate reasons, then we might not want to | |
865 | install them both. We might want to install just one. If you send them | |
866 | all jumbled together in a single set of diffs, we have to do extra work | |
867 | to disentangle them---to figure out which parts of the change serve | |
868 | which purpose. If we don't have time for this, we might have to ignore | |
869 | your changes entirely. | |
870 | ||
871 | If you send each change as soon as you have written it, with its own | |
872 | explanation, then two changes never get tangled up, and we can consider | |
873 | each one properly without any extra work to disentangle them. | |
874 | ||
875 | @item | |
876 | Send each change as soon as that change is finished. Sometimes people | |
877 | think they are helping us by accumulating many changes to send them all | |
878 | together. As explained above, this is absolutely the worst thing you | |
879 | could do. | |
880 | ||
881 | Since you should send each change separately, you might as well send it | |
882 | right away. That gives us the option of installing it immediately if it | |
883 | is important. | |
884 | ||
885 | @item | |
886 | Use @samp{diff -c} to make your diffs. Diffs without context are hard | |
887 | to install reliably. More than that, they are hard to study; we must | |
888 | always study a patch to decide whether we want to install it. Unidiff | |
889 | format is better than contextless diffs, but not as easy to read as | |
890 | @samp{-c} format. | |
891 | ||
892 | If you have GNU diff, use @samp{diff -c -F'^[_a-zA-Z0-9$]+ *('} when | |
893 | making diffs of C code. This shows the name of the function that each | |
894 | change occurs in. | |
895 | ||
896 | @item | |
897 | Avoid any ambiguity as to which is the old version and which is the new. | |
898 | Please make the old version the first argument to diff, and the new | |
899 | version the second argument. And please give one version or the other a | |
900 | name that indicates whether it is the old version or your new changed | |
901 | one. | |
902 | ||
903 | @item | |
904 | Write the change log entries for your changes. This is both to save us | |
905 | the extra work of writing them, and to help explain your changes so we | |
906 | can understand them. | |
907 | ||
908 | The purpose of the change log is to show people where to find what was | |
909 | changed. So you need to be specific about what functions you changed; | |
910 | in large functions, it's often helpful to indicate where within the | |
911 | function the change was. | |
912 | ||
913 | On the other hand, once you have shown people where to find the change, | |
914 | you need not explain its purpose in the change log. Thus, if you add a | |
915 | new function, all you need to say about it is that it is new. If you | |
916 | feel that the purpose needs explaining, it probably does---but put the | |
917 | explanation in comments in the code. It will be more useful there. | |
918 | ||
919 | Please read the @file{ChangeLog} files in the @file{src} and @file{lisp} | |
920 | directories to see what sorts of information to put in, and to learn the | |
921 | style that we use. If you would like your name to appear in the header | |
922 | line, showing who made the change, send us the header line. | |
923 | @xref{Change Log}. | |
924 | ||
925 | @item | |
926 | When you write the fix, keep in mind that we can't install a change that | |
927 | would break other systems. Please think about what effect your change | |
928 | will have if compiled on another type of system. | |
929 | ||
930 | Sometimes people send fixes that @emph{might} be an improvement in | |
931 | general---but it is hard to be sure of this. It's hard to install | |
932 | such changes because we have to study them very carefully. Of course, | |
933 | a good explanation of the reasoning by which you concluded the change | |
934 | was correct can help convince us. | |
935 | ||
936 | The safest changes are changes to the configuration files for a | |
937 | particular machine. These are safe because they can't create new bugs | |
938 | on other machines. | |
939 | ||
940 | Please help us keep up with the workload by designing the patch in a | |
941 | form that is clearly safe to install. | |
942 | @end itemize | |
943 | ||
944 | @node Contributing, Service, Bugs, Top | |
945 | @section Contributing to Emacs Development | |
946 | ||
947 | If you would like to help pretest Emacs releases to assure they work | |
948 | well, or if you would like to work on improving Emacs, please contact | |
60a96371 | 949 | the maintainers at @email{bug-gnu-emacs@@gnu.org}. A pretester |
6bf7aab6 DL |
950 | should be prepared to investigate bugs as well as report them. If you'd |
951 | like to work on improving Emacs, please ask for suggested projects or | |
952 | suggest your own ideas. | |
953 | ||
954 | If you have already written an improvement, please tell us about it. If | |
955 | you have not yet started work, it is useful to contact | |
60a96371 | 956 | @email{bug-gnu-emacs@@gnu.org} before you start; it might be |
6bf7aab6 DL |
957 | possible to suggest ways to make your extension fit in better with the |
958 | rest of Emacs. | |
959 | ||
960 | @node Service, Command Arguments, Contributing, Top | |
961 | @section How To Get Help with GNU Emacs | |
962 | ||
963 | If you need help installing, using or changing GNU Emacs, there are two | |
964 | ways to find it: | |
965 | ||
966 | @itemize @bullet | |
967 | @item | |
968 | Send a message to the mailing list | |
60a96371 | 969 | @email{help-gnu-emacs@@gnu.org}, or post your request on |
6bf7aab6 DL |
970 | newsgroup @code{gnu.emacs.help}. (This mailing list and newsgroup |
971 | interconnect, so it does not matter which one you use.) | |
972 | ||
973 | @item | |
974 | Look in the service directory for someone who might help you for a fee. | |
975 | The service directory is found in the file named @file{etc/SERVICE} in the | |
976 | Emacs distribution. | |
977 | @end itemize |