@c This is part of the Emacs manual.
-@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
+@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2001, 2002,
+@c 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@iftex
@chapter Dealing with Common Problems
also considered.
@end iftex
+@ifnottex
+@raisesections
+@end ifnottex
+
@node Quitting, Lossage, Customization, Top
@section Quitting and Aborting
@cindex quitting
@table @kbd
@item C-g
-@itemx C-@key{BREAK} (MS-DOS)
-Quit. Cancel running or partially typed command.
+@itemx C-@key{BREAK} @r{(MS-DOS only)}
+Quit: cancel running or partially typed command.
@item C-]
Abort innermost recursive editing level and cancel the command which
invoked it (@code{abort-recursive-edit}).
Cancel a previously made change in the buffer contents (@code{undo}).
@end table
- There are two ways of canceling commands which are not finished
-executing: @dfn{quitting} with @kbd{C-g}, and @dfn{aborting} with
-@kbd{C-]} or @kbd{M-x top-level}. Quitting cancels a partially typed
-command or one which is already running. Aborting exits a recursive
-editing level and cancels the command that invoked the recursive edit.
+ There are two ways of canceling a command before it has finished:
+@dfn{quitting} with @kbd{C-g}, and @dfn{aborting} with @kbd{C-]} or
+@kbd{M-x top-level}. Quitting cancels a partially typed command, or
+one which is still running. Aborting exits a recursive editing level
+and cancels the command that invoked the recursive edit.
(@xref{Recursive Edit}.)
@cindex quitting
@kindex C-g
- Quitting with @kbd{C-g} is used for getting rid of a partially typed
+ Quitting with @kbd{C-g} is the way to get rid of a partially typed
command, or a numeric argument that you don't want. It also stops a
running command in the middle in a relatively safe way, so you can use
it if you accidentally give a command which takes a long time. In
-particular, it is safe to quit out of killing; either your text will
-@emph{all} still be in the buffer, or it will @emph{all} be in the kill
-ring (or maybe both). Quitting an incremental search does special
-things documented under searching; in general, it may take two
-successive @kbd{C-g} characters to get out of a search
-(@pxref{Incremental Search}).
+particular, it is safe to quit out of a kill command; either your text
+will @emph{all} still be in the buffer, or it will @emph{all} be in
+the kill ring, or maybe both. Quitting an incremental search does
+special things, documented under searching; it may take two successive
+@kbd{C-g} characters to get out of a search (@pxref{Incremental
+Search}).
On MS-DOS, the character @kbd{C-@key{BREAK}} serves as a quit character
like @kbd{C-g}. The reason is that it is not feasible, on MS-DOS, to
recognize @kbd{C-g} while a command is running, between interactions
with the user. By contrast, it @emph{is} feasible to recognize
-@kbd{C-@key{BREAK}} at all times. @xref{MS-DOS Input}.
+@kbd{C-@key{BREAK}} at all times.
+@iftex
+@xref{MS-DOS Keyboard,,,emacs-xtra, Specialized Emacs Features}.
+@end iftex
+@ifnottex
+@xref{MS-DOS Keyboard}.
+@end ifnottex
+
+@findex keyboard-quit
@kbd{C-g} works by setting the variable @code{quit-flag} to @code{t}
the instant @kbd{C-g} is typed; Emacs Lisp checks this variable
-frequently and quits if it is non-@code{nil}. @kbd{C-g} is only
+frequently, and quits if it is non-@code{nil}. @kbd{C-g} is only
actually executed as a command if you type it while Emacs is waiting for
-input.
+input. In that case, the command it runs is @code{keyboard-quit}.
- If you quit with @kbd{C-g} a second time before the first @kbd{C-g} is
-recognized, you activate the ``emergency escape'' feature and return to
-the shell. @xref{Emergency Escape}.
+ On a text terminal, if you quit with @kbd{C-g} a second time before
+the first @kbd{C-g} is recognized, you activate the ``emergency
+escape'' feature and return to the shell. @xref{Emergency Escape}.
@cindex NFS and quitting
- There may be times when you cannot quit. When Emacs is waiting for
-the operating system to do something, quitting is impossible unless
-special pains are taken for the particular system call within Emacs
-where the waiting occurs. We have done this for the system calls that
-users are likely to want to quit from, but it's possible you will find
-another. In one very common case---waiting for file input or output
-using NFS---Emacs itself knows how to quit, but most NFS implementations
-simply do not allow user programs to stop waiting for NFS when the NFS
-server is hung.
+ There are some situations where you cannot quit. When Emacs is
+waiting for the operating system to do something, quitting is
+impossible unless special pains are taken for the particular system
+call within Emacs where the waiting occurs. We have done this for the
+system calls that users are likely to want to quit from, but it's
+possible you will a case not handled. In one very common
+case---waiting for file input or output using NFS---Emacs itself knows
+how to quit, but many NFS implementations simply do not allow user
+programs to stop waiting for NFS when the NFS server is hung.
@cindex aborting recursive edit
@findex abort-recursive-edit
@findex keyboard-escape-quit
@kindex ESC ESC ESC
- The command @kbd{@key{ESC} @key{ESC} @key{ESC}}
-(@code{keyboard-escape-quit}) can either quit or abort. This key was
-defined because @key{ESC} is used to ``get out'' in many PC programs.
-It can cancel a prefix argument, clear a selected region, or get out of
-a Query Replace, like @kbd{C-g}. It can get out of the minibuffer or a
-recursive edit, like @kbd{C-]}. It can also get out of splitting the
-frame into multiple windows, like @kbd{C-x 1}. One thing it cannot do,
-however, is stop a command that is running. That's because it executes
-as an ordinary command, and Emacs doesn't notice it until it is ready
-for a command.
+ The sequence @kbd{@key{ESC} @key{ESC} @key{ESC}}
+(@code{keyboard-escape-quit}) can either quit or abort. (We defined
+it this way because @key{ESC} means ``get out'' in many PC programs.)
+It can cancel a prefix argument, clear a selected region, or get out
+of a Query Replace, like @kbd{C-g}. It can get out of the minibuffer
+or a recursive edit, like @kbd{C-]}. It can also get out of splitting
+the frame into multiple windows, as with @kbd{C-x 1}. One thing it
+cannot do, however, is stop a command that is running. That's because
+it executes as an ordinary command, and Emacs doesn't notice it until
+it is ready for the next command.
@findex top-level
The command @kbd{M-x top-level} is equivalent to ``enough'' @kbd{C-]}
@kbd{C-x u} (@code{undo}) is not strictly speaking a way of canceling
a command, but you can think of it as canceling a command that already
-finished executing. @xref{Undo}.
+finished executing. @xref{Undo}, for more information
+about the undo facility.
@node Lossage, Bugs, Quitting, Top
@section Dealing with Emacs Trouble
This section describes various conditions in which Emacs fails to work
-normally, and how to recognize them and correct them.
+normally, and how to recognize them and correct them. For a list of
+additional problems you might encounter, see @ref{Bugs and problems, ,
+Bugs and problems, efaq, GNU Emacs FAQ}, and the file @file{etc/PROBLEMS}
+in the Emacs distribution. Type @kbd{C-h C-f} to read the FAQ; type
+@kbd{C-h C-e} to read the @file{PROBLEMS} file.
@menu
-* DEL Gets Help:: What to do if @key{DEL} doesn't delete.
-* Stuck Recursive:: `[...]' in mode line around the parentheses.
-* Screen Garbled:: Garbage on the screen.
-* Text Garbled:: Garbage in the text.
-* Unasked-for Search:: Spontaneous entry to incremental search.
-* Memory Full:: How to cope when you run out of memory.
-* After a Crash:: Recovering editing in an Emacs session that crashed.
-* Emergency Escape:: Emergency escape---
- What to do if Emacs stops responding.
-* Total Frustration:: When you are at your wits' end.
+* DEL Does Not Delete:: What to do if @key{DEL} doesn't delete.
+* Stuck Recursive:: `[...]' in mode line around the parentheses.
+* Screen Garbled:: Garbage on the screen.
+* Text Garbled:: Garbage in the text.
+* Memory Full:: How to cope when you run out of memory.
+* After a Crash:: Recovering editing in an Emacs session that crashed.
+* Emergency Escape:: Emergency escape---
+ What to do if Emacs stops responding.
+* Total Frustration:: When you are at your wits' end.
@end menu
-@node DEL Gets Help
+@node DEL Does Not Delete
@subsection If @key{DEL} Fails to Delete
+@cindex @key{DEL} vs @key{BACKSPACE}
+@cindex @key{BACKSPACE} vs @key{DEL}
+@cindex usual erasure key
+
+ Every keyboard has a large key, a little ways above the @key{RET} or
+@key{ENTER} key, which you normally use outside Emacs to erase the
+last character that you typed. We call this key @dfn{the usual
+erasure key}. In Emacs, it is supposed to be equivalent to @key{DEL},
+and when Emacs is properly configured for your terminal, it translates
+that key into the character @key{DEL}.
+
+ When Emacs starts up on a graphical display, it determines
+automatically which key should be @key{DEL}. In some unusual cases
+Emacs gets the wrong information from the system. If the usual
+erasure key deletes forwards instead of backwards, that is probably
+what happened---Emacs ought to be treating the @key{DELETE} key as
+@key{DEL}, but it isn't.
+
+ On a graphical display, if the usual erasure key is labeled
+@key{BACKSPACE} and there is a @key{DELETE} key elsewhere, but the
+@key{DELETE} key deletes backward instead of forward, that too
+suggests Emacs got the wrong information---but in the opposite sense.
+It ought to be treating the @key{BACKSPACE} key as @key{DEL}, and
+treating @key{DELETE} differently, but it isn't.
+
+ On a text-only terminal, if you find the usual erasure key prompts
+for a Help command, like @kbd{Control-h}, instead of deleting a
+character, it means that key is actually sending the @key{BS}
+character. Emacs ought to be treating @key{BS} as @key{DEL}, but it
+isn't.
+
+ In all of those cases, the immediate remedy is the same: use the
+command @kbd{M-x normal-erase-is-backspace-mode}. This toggles
+between the two modes that Emacs supports for handling @key{DEL}, so
+if Emacs starts in the wrong mode, this should switch to the right
+mode. On a text-only terminal, if you want to ask for help when
+@key{BS} is treated as @key{DEL}, use @key{F1}; @kbd{C-?} may also
+work, if it sends character code 127.
+
+@findex normal-erase-is-backspace-mode
+ To fix the problem automatically for every Emacs session, you can
+put one of the following lines into your @file{.emacs} file
+(@pxref{Init File}). For the first case above, where @key{DELETE}
+deletes forwards instead of backwards, use this line to make
+@key{DELETE} act as @key{DEL} (resulting in behavior compatible
+with Emacs 20 and previous versions):
+
+@lisp
+(normal-erase-is-backspace-mode 0)
+@end lisp
- If you find that @key{DEL} enters Help like @kbd{Control-h} instead of
-deleting a character, your terminal is sending the wrong code for
-@key{DEL}. You can work around this problem by changing the keyboard
-translation table (@pxref{Keyboard Translations}).
+@noindent
+For the other two cases, where @key{BACKSPACE} ought to act as
+@key{DEL}, use this line:
+
+@lisp
+(normal-erase-is-backspace-mode 1)
+@end lisp
+
+@vindex normal-erase-is-backspace
+ Another way to fix the problem for every Emacs session is to
+customize the variable @code{normal-erase-is-backspace}: the value
+@code{t} specifies the mode where @key{BS} or @key{BACKSPACE} is
+@key{DEL}, and @code{nil} specifies the other mode. @xref{Easy
+Customization}.
+
+ On a graphical display, it can also happen that the usual erasure key
+is labeled @key{BACKSPACE}, there is a @key{DELETE} key elsewhere, and
+both keys delete forward. This probably means that someone has
+redefined your @key{BACKSPACE} key as a @key{DELETE} key. With X,
+this is typically done with a command to the @code{xmodmap} program
+when you start the server or log in. The most likely motive for this
+customization was to support old versions of Emacs, so we recommend
+you simply remove it now.
@node Stuck Recursive
@subsection Recursive Editing Levels
Recursive editing levels are important and useful features of Emacs, but
-they can seem like malfunctions to the user who does not understand them.
+they can seem like malfunctions if you do not understand them.
If the mode line has square brackets @samp{[@dots{}]} around the parentheses
that contain the names of the major and minor modes, you have entered a
@node Screen Garbled
@subsection Garbage on the Screen
- If the data on the screen looks wrong, the first thing to do is see
-whether the text is really wrong. Type @kbd{C-l}, to redisplay the
-entire screen. If the screen appears correct after this, the problem
-was entirely in the previous screen update. (Otherwise, see @ref{Text
-Garbled}.)
-
- Display updating problems often result from an incorrect termcap entry
-for the terminal you are using. The file @file{etc/TERMS} in the Emacs
-distribution gives the fixes for known problems of this sort.
-@file{INSTALL} contains general advice for these problems in one of its
-sections. Very likely there is simply insufficient padding for certain
-display operations. To investigate the possibility that you have this sort
-of problem, try Emacs on another terminal made by a different manufacturer.
-If problems happen frequently on one kind of terminal but not another kind,
-it is likely to be a bad termcap entry, though it could also be due to a
-bug in Emacs that appears for terminals that have or that lack specific
-features.
+ If the text on a text terminal looks wrong, the first thing to do is
+see whether it is wrong in the buffer. Type @kbd{C-l} to redisplay
+the entire screen. If the screen appears correct after this, the
+problem was entirely in the previous screen update. (Otherwise, see
+the following section.)
+
+ Display updating problems often result from an incorrect terminfo
+entry for the terminal you are using. The file @file{etc/TERMS} in
+the Emacs distribution gives the fixes for known problems of this
+sort. @file{INSTALL} contains general advice for these problems in
+one of its sections. To investigate the possibility that you have
+this sort of problem, try Emacs on another terminal made by a
+different manufacturer. If problems happen frequently on one kind of
+terminal but not another kind, it is likely to be a bad terminfo entry,
+though it could also be due to a bug in Emacs that appears for
+terminals that have or that lack specific features.
@node Text Garbled
@subsection Garbage in the Text
- If @kbd{C-l} shows that the text is wrong, try undoing the changes to it
-using @kbd{C-x u} until it gets back to a state you consider correct. Also
-try @kbd{C-h l} to find out what command you typed to produce the observed
-results.
+ If @kbd{C-l} shows that the text is wrong, first type @kbd{C-h l} to
+see what commands you typed to produce the observed results. Then try
+undoing the changes step by step using @kbd{C-x u}, until it gets back
+to a state you consider correct.
If a large portion of text appears to be missing at the beginning or
end of the buffer, check for the word @samp{Narrow} in the mode line.
temporarily off-limits. To make it accessible again, type @kbd{C-x n
w}. @xref{Narrowing}.
-@node Unasked-for Search
-@subsection Spontaneous Entry to Incremental Search
-
- If Emacs spontaneously displays @samp{I-search:} at the bottom of the
-screen, it means that the terminal is sending @kbd{C-s} and @kbd{C-q}
-according to the poorly designed xon/xoff ``flow control'' protocol.
-
- If this happens to you, your best recourse is to put the terminal in a
-mode where it will not use flow control, or give it so much padding that
-it will never send a @kbd{C-s}. (One way to increase the amount of
-padding is to set the variable @code{baud-rate} to a larger value. Its
-value is the terminal output speed, measured in the conventional units
-of baud.)
-
-@cindex flow control
-@cindex xon-xoff
-@findex enable-flow-control
- If you don't succeed in turning off flow control, the next best thing
-is to tell Emacs to cope with it. To do this, call the function
-@code{enable-flow-control}.
-
-@findex enable-flow-control-on
- Typically there are particular terminal types with which you must use
-flow control. You can conveniently ask for flow control on those
-terminal types only, using @code{enable-flow-control-on}. For example,
-if you find you must use flow control on VT-100 and H19 terminals, put
-the following in your @file{.emacs} file:
-
-@example
-(enable-flow-control-on "vt100" "h19")
-@end example
-
- When flow control is enabled, you must type @kbd{C-\} to get the
-effect of a @kbd{C-s}, and type @kbd{C-^} to get the effect of a
-@kbd{C-q}. (These aliases work by means of keyboard translations; see
-@ref{Keyboard Translations}.)
-
@node Memory Full
@subsection Running out of Memory
@cindex memory full
@cindex out of memory
- If you get the error message @samp{Virtual memory exceeded}, save your
-modified buffers with @kbd{C-x s}. This method of saving them has the
-smallest need for additional memory. Emacs keeps a reserve of memory
-which it makes available when this error happens; that should be enough
-to enable @kbd{C-x s} to complete its work.
-
- Once you have saved your modified buffers, you can exit this Emacs job
-and start another, or you can use @kbd{M-x kill-some-buffers} to free
-space in the current Emacs job. If you kill buffers containing a
-substantial amount of text, you can safely go on editing. Emacs refills
-its memory reserve automatically when it sees sufficient free space
-available, in case you run out of memory another time.
+ If you get the error message @samp{Virtual memory exceeded}, save
+your modified buffers with @kbd{C-x s}. This method of saving them
+has the smallest need for additional memory. Emacs keeps a reserve of
+memory which it makes available when this error happens; that should
+be enough to enable @kbd{C-x s} to complete its work. When the
+reserve has been used, @samp{!MEM FULL!} appears at the beginning of
+the mode line, indicating there is no more reserve.
+
+ Once you have saved your modified buffers, you can exit this Emacs
+session and start another, or you can use @kbd{M-x kill-some-buffers}
+to free space in the current Emacs job. If this frees up sufficient
+space, Emacs will refill its memory reserve, and @samp{!MEM FULL!}
+will disappear from the mode line. That means you can safely go on
+editing in the same Emacs session.
Do not use @kbd{M-x buffer-menu} to save or kill buffers when you run
-out of memory, because the buffer menu needs a fair amount memory
+out of memory, because the buffer menu needs a fair amount of memory
itself, and the reserve supply may not be enough.
@node After a Crash
recover from. Typically the one you want is the most recent one. Move
point to the one you choose, and type @kbd{C-c C-c}.
- Then @code{recover-session} asks about each of the files that you were
-editing during that session; it asks whether to recover that file. If
-you answer @kbd{y} for a file, it shows the dates of that file and its
-auto-save file, then asks once again whether to recover that file. For
-the second question, you must confirm with @kbd{yes}. If you do, Emacs
-visits the file but gets the text from the auto-save file.
+ Then @code{recover-session} considers each of the files that you
+were editing during that session; for each such file, it asks whether
+to recover that file. If you answer @kbd{y} for a file, it shows the
+dates of that file and its auto-save file, then asks once again
+whether to recover that file. For the second question, you must
+confirm with @kbd{yes}. If you do, Emacs visits the file but gets the
+text from the auto-save file.
When @code{recover-session} is done, the files you've chosen to
recover are present in Emacs buffers. You should then save them. Only
this---saving them---updates the files themselves.
+ As a last resort, if you had buffers with content which were not
+associated with any files, or if the autosave was not recent enough to
+have recorded important changes, you can use the
+@file{etc/emacs-buffer.gdb} script with GDB (the GNU Debugger) to
+retrieve them from a core dump--provided that a core dump was saved,
+and that the Emacs executable was not stripped of its debugging
+symbols.
+
+ As soon as you get the core dump, rename it to another name such as
+@file{core.emacs}, so that another crash won't overwrite it.
+
+ To use this script, run @code{gdb} with the file name of your Emacs
+executable and the file name of the core dump, e.g. @samp{gdb
+/usr/bin/emacs core.emacs}. At the @code{(gdb)} prompt, load the
+recovery script: @samp{source /usr/src/emacs/etc/emacs-buffer.gdb}.
+Then type the command @code{ybuffer-list} to see which buffers are
+available. For each buffer, it lists a buffer number. To save a
+buffer, use @code{ysave-buffer}; you specify the buffer number, and
+the file name to write that buffer into. You should use a file name
+which does not already exist; if the file does exist, the script does
+not make a backup of its old contents.
+
@node Emergency Escape
@subsection Emergency Escape
- Because at times there have been bugs causing Emacs to loop without
-checking @code{quit-flag}, a special feature causes Emacs to be suspended
-immediately if you type a second @kbd{C-g} while the flag is already set,
-so you can always get out of GNU Emacs. Normally Emacs recognizes and
-clears @code{quit-flag} (and quits!) quickly enough to prevent this from
-happening. (On MS-DOS and compatible systems, type @kbd{C-@key{BREAK}}
-twice.)
+ On text-only terminals, the @dfn{emergency escape} feature suspends
+Emacs immediately if you type @kbd{C-g} a second time before Emacs can
+actually respond to the first one by quitting. This is so you can
+always get out of GNU Emacs no matter how badly it might be hung.
+When things are working properly, Emacs recognizes and handles the
+first @kbd{C-g} so fast that the second one won't trigger emergency
+escape. However, if some problem prevents Emacs from handling the
+first @kbd{C-g} properly, then the second one will get you back to the
+shell.
- When you resume Emacs after a suspension caused by multiple @kbd{C-g}, it
-asks two questions before going back to what it had been doing:
+ When you resume Emacs after a suspension caused by emergency escape,
+it asks two questions before going back to what it had been doing:
@example
Auto-save? (y or n)
@noindent
Answer each one with @kbd{y} or @kbd{n} followed by @key{RET}.
- Saying @kbd{y} to @samp{Auto-save?} causes immediate auto-saving of all
-modified buffers in which auto-saving is enabled.
+ Saying @kbd{y} to @samp{Auto-save?} causes immediate auto-saving of
+all modified buffers in which auto-saving is enabled. Saying @kbd{n}
+skips this.
+
+ Saying @kbd{y} to @samp{Abort (and dump core)?} causes Emacs to
+crash, dumping core. This is to enable a wizard to figure out why
+Emacs was failing to quit in the first place. Execution does not
+continue after a core dump.
- Saying @kbd{y} to @samp{Abort (and dump core)?} causes an illegal instruction to be
-executed, dumping core. This is to enable a wizard to figure out why Emacs
-was failing to quit in the first place. Execution does not continue
-after a core dump. If you answer @kbd{n}, execution does continue. With
-luck, GNU Emacs will ultimately check @code{quit-flag} and quit normally.
-If not, and you type another @kbd{C-g}, it is suspended again.
+ If you answer this question @kbd{n}, Emacs execution resumes. With
+luck, Emacs will ultimately do the requested quit. If not, each
+subsequent @kbd{C-g} invokes emergency escape again.
If Emacs is not really hung, just slow, you may invoke the double
-@kbd{C-g} feature without really meaning to. Then just resume and answer
-@kbd{n} to both questions, and you will arrive at your former state.
-Presumably the quit you requested will happen soon.
+@kbd{C-g} feature without really meaning to. Then just resume and
+answer @kbd{n} to both questions, and you will get back to the former
+state. The quit you requested will happen by and by.
- The double-@kbd{C-g} feature is turned off when Emacs is running under
-the X Window System, since you can use the window manager to kill Emacs
-or to create another window and run another program.
+ Emergency escape is active only for text terminals. On graphical
+displays, you can use the mouse to kill Emacs or switch to another
+program.
- On MS-DOS and compatible systems, the emergency escape feature is
-sometimes unavailable, even if you press @kbd{C-@key{BREAK}} twice, when
-some system call (MS-DOS or BIOS) hangs, or when Emacs is stuck in a
-very tight endless loop (in C code, @strong{not} in Lisp code).
+ On MS-DOS, you must type @kbd{C-@key{BREAK}} (twice) to cause
+emergency escape---but there are cases where it won't work, when
+system call hangs or when Emacs is stuck in a tight loop in C code.
@node Total Frustration
@subsection Help for Total Frustration
@findex doctor
Second, type @kbd{M-x doctor @key{RET}}.
- The doctor will help you feel better. Each time you say something to
-the doctor, you must end it by typing @key{RET} @key{RET}. This lets
-the doctor know you are finished.
+ The Emacs psychotherapist will help you feel better. Each time you
+say something to the psychotherapist, you must end it by typing
+@key{RET} @key{RET}. This indicates you are finished typing.
@node Bugs, Contributing, Lossage, Top
@section Reporting Bugs
To make it possible for us to fix a bug, you must report it. In order
to do so effectively, you must know when and how to do it.
+ Before reporting a bug, it is a good idea to see if it is already
+known. You can find the list of known problems in the file
+@file{etc/PROBLEMS} in the Emacs distribution; type @kbd{C-h C-e} to read
+it. Some additional user-level problems can be found in @ref{Bugs and
+problems, , Bugs and problems, efaq, GNU Emacs FAQ}. Looking up your
+problem in these two documents might provide you with a solution or a
+work-around, or give you additional information about related issues.
+
@menu
* Criteria: Bug Criteria. Have you really found a bug?
* Understanding Bug Reporting:: How to report a bug effectively.
@node Bug Criteria
@subsection When Is There a Bug
- If Emacs executes an illegal instruction, or dies with an operating
-system error message that indicates a problem in the program (as opposed to
-something like ``disk full''), then it is certainly a bug.
+ If Emacs accesses an invalid memory location (``segmentation
+fault''), or exits with an operating system error message that
+indicates a problem in the program (as opposed to something like
+``disk full''), then it is certainly a bug.
If Emacs updates the display in a way that does not correspond to what is
in the buffer, then it is certainly a bug. If a command seems to do the
then it might actually be working right. Rather than jumping to
conclusions, show the problem to someone who knows for certain.
- Finally, a command's intended definition may not be best for editing
-with. This is a very important sort of problem, but it is also a matter of
-judgment. Also, it is easy to come to such a conclusion out of ignorance
-of some of the existing features. It is probably best not to complain
-about such a problem until you have checked the documentation in the usual
-ways, feel confident that you understand it, and know for certain that what
-you want is not available. If you are not sure what the command is
-supposed to do after a careful reading of the manual, check the index and
-glossary for any terms that may be unclear.
+ Finally, a command's intended definition may not be the best
+possible definition for editing with. This is a very important sort
+of problem, but it is also a matter of judgment. Also, it is easy to
+come to such a conclusion out of ignorance of some of the existing
+features. It is probably best not to complain about such a problem
+until you have checked the documentation in the usual ways, feel
+confident that you understand it, and know for certain that what you
+want is not available. Ask other Emacs users, too. If you are not
+sure what the command is supposed to do after a careful reading of the
+manual, check the index and glossary for any terms that may be
+unclear.
If after careful rereading of the manual you still do not understand
what the command should do, that indicates a bug in the manual, which
have no real information about the bug.
For example, suppose that you type @kbd{C-x C-f /glorp/baz.ugh
-@key{RET}}, visiting a file which (you know) happens to be rather large,
-and Emacs displayed @samp{I feel pretty today}. The best way to report
-the bug is with a sentence like the preceding one, because it gives all
-the facts.
+@key{RET}}, visiting a file which (you know) happens to be rather
+large, and Emacs displays @samp{I feel pretty today}. The best way to
+report the bug is with a sentence like the preceding one, because it
+gives all the facts.
A bad way would be to assume that the problem is due to the size of
the file and say, ``I visited a large file, and Emacs displayed @samp{I
you @emph{know} that it makes no difference which visiting command is used.
Similarly, rather than saying ``if I have three characters on the line,''
say ``after I type @kbd{@key{RET} A B C @key{RET} C-p},'' if that is
-the way you entered the text.@refill
+the way you entered the text.
So please don't guess any explanations when you report a bug. If you
want to actually @emph{debug} the problem, and report explanations that
@cindex reporting bugs
The best way to send a bug report is to mail it electronically to the
-Emacs maintainers at @samp{bug-gnu-emacs@@gnu.org}, or to
-@samp{emacs-pretest-bug@@gnu.org} if you are pretesting an Emacs beta
+Emacs maintainers at @email{bug-gnu-emacs@@gnu.org}, or to
+@email{emacs-pretest-bug@@gnu.org} if you are pretesting an Emacs beta
release. (If you want to suggest a change as an improvement, use the
same address.)
spectator you should not criticize anything about what you see there.
The purpose of bug reports is to give information to the Emacs
maintainers. Spectators are welcome only as long as they do not
-interfere with this. In particular, some bug reports contain large
-amounts of data; spectators should not complain about this.
+interfere with this. In particular, some bug reports contain fairly
+large amounts of data; spectators should not complain about this.
Please do not post bug reports using netnews; mail is more reliable
-than netnews about reporting your correct address, which we may need in
-order to ask you for more information.
-
- If you can't send electronic mail, then mail the bug report on paper
-or machine-readable media to this address:
-
-@format
-GNU Emacs Bugs
-Free Software Foundation
-59 Temple Place, Suite 330
-Boston, MA 02111-1307 USA
-@end format
-
- We do not promise to fix the bug; but if the bug is serious,
-or ugly, or easy to fix, chances are we will want to.
+than netnews about reporting your correct address, which we may need
+in order to ask you for more information. If your data is more than
+500,000 bytes, please don't include it directly in the bug report;
+instead, offer to send it on request, or make it available by ftp and
+say where.
@findex report-emacs-bug
A convenient way to send a bug report for Emacs is to use the command
If you can tell us a way to cause the problem without visiting any files,
please do so. This makes it much easier to debug. If you do need files,
make sure you arrange for us to see their exact contents. For example, it
-can often matter whether there are spaces at the ends of lines, or a
+can matter whether there are spaces at the ends of lines, or a
newline after the last line in the buffer (nothing ought to care whether
the last line is terminated, but try telling the bugs that).
@findex open-dribble-file
@cindex dribble file
- The easy way to record the input to Emacs precisely is to write a
+@cindex logging keystrokes
+The easy way to record the input to Emacs precisely is to write a
dribble file. To start the file, execute the Lisp expression
@example
@item
@findex open-termscript
@cindex termscript file
-@cindex @code{TERM} environment variable
+@cindex @env{TERM} environment variable
For possible display bugs, the terminal type (the value of environment
-variable @code{TERM}), the complete termcap entry for the terminal from
+variable @env{TERM}), the complete termcap entry for the terminal from
@file{/etc/termcap} (since that file is not identical on all machines),
and the output that Emacs actually sent to the terminal.
Be warned: it is often difficult, and sometimes impossible, to fix a
terminal-dependent bug without access to a terminal of the type that
-stimulates the bug.@refill
+stimulates the bug.
+
+@item
+If non-@acronym{ASCII} text or internationalization is relevant, the locale that
+was current when you started Emacs. On GNU/Linux and Unix systems, or
+if you use a Posix-style shell such as Bash, you can use this shell
+command to view the relevant values:
+
+@smallexample
+echo LC_ALL=$LC_ALL LC_COLLATE=$LC_COLLATE LC_CTYPE=$LC_CTYPE \
+ LC_MESSAGES=$LC_MESSAGES LC_TIME=$LC_TIME LANG=$LANG
+@end smallexample
+
+Alternatively, use the @command{locale} command, if your system has it,
+to display your locale settings.
+
+You can use the @kbd{M-!} command to execute these commands from
+Emacs, and then copy the output from the @samp{*Messages*} buffer into
+the bug report. Alternatively, @kbd{M-x getenv @key{RET} LC_ALL
+@key{RET}} will display the value of @code{LC_ALL} in the echo area, and
+you can copy its output from the @samp{*Messages*} buffer.
@item
A description of what behavior you observe that you believe is
whether the bug was happening---we would not be able to draw any
conclusion from our observations.
+@item
+If the bug is that the Emacs Manual or the Emacs Lisp Reference Manual
+fails to describe the actual behavior of Emacs, or that the text is
+confusing, copy in the text from the online manual which you think is
+at fault. If the section is small, just the section name is enough.
+
@item
If the manifestation of the bug is an Emacs error message, it is
important to report the precise text of the error message, and a
@samp{*Messages*} buffer into the bug report. Copy all of it, not just
part.
-To make a backtrace for the error, evaluate the Lisp expression
-@code{(setq @w{debug-on-error t})} before the error happens (that is to
-say, you must execute that expression and then make the bug happen).
-This causes the error to run the Lisp debugger, which shows you a
-backtrace. Copy the text of the debugger's backtrace into the bug
-report.
+@findex toggle-debug-on-error
+@pindex Edebug
+To make a backtrace for the error, use @kbd{M-x toggle-debug-on-error}
+before the error happens (that is to say, you must give that command
+and then make the bug happen). This causes the error to start the Lisp
+debugger, which shows you a backtrace. Copy the text of the
+debugger's backtrace into the bug report. @xref{Debugger,, The Lisp
+Debugger, elisp, the Emacs Lisp Reference Manual}, for information on
+debugging Emacs Lisp programs with the Edebug package.
This use of the debugger is possible only if you know how to make the
bug happen again. If you can't make it happen again, at least copy
@code{Fsignal}.
For a short listing of Lisp functions running, type the GDB
-command @code{xbacktrace}.
-
-If you want to examine Lisp function arguments, move up the stack, and
-each time you get to a frame for the function @code{Ffuncall}, type
-these GDB commands:
-
-@example
-p *args
-pr
-@end example
-
-@noindent
-To print the first argument that the function received, use these
-commands:
-
-@example
-p args[1]
-pr
-@end example
-
-@noindent
-You can print the other arguments likewise. The argument @code{nargs}
-of @code{Ffuncall} says how many arguments @code{Ffuncall} received;
-these include the Lisp function itself and the arguments for that
-function.
+command @code{xbacktrace}.
The file @file{.gdbinit} defines several other commands that are useful
for examining the data types and contents of Lisp objects. Their names
@code{pr} does not, such as when debugging a core dump or when Emacs has
had a fatal signal.
-@item
-If the symptom of the bug is that Emacs fails to respond, don't assume
-Emacs is ``hung''---it may instead be in an infinite loop. To find out
-which, make the problem happen under GDB and stop Emacs once it is not
-responding. (If Emacs is using X Windows directly, you can stop Emacs
-by typing @kbd{C-z} at the GDB job.) Then try stepping with
-@samp{step}. If Emacs is hung, the @samp{step} command won't return.
-If it is looping, @samp{step} will return.
-
-If this shows Emacs is hung in a system call, stop it again and examine
-the arguments of the call. In your bug report, state exactly where in
-the source the system call is, and what the arguments are.
-
-If Emacs is in an infinite loop, please determine where the loop starts
-and ends. The easiest way to do this is to use the GDB command
-@samp{finish}. Each time you use it, Emacs resumes execution until it
-exits one stack frame. Keep typing @samp{finish} until it doesn't
-return---that means the infinite loop is in the stack frame which you
-just tried to finish.
-
-Stop Emacs again, and use @samp{finish} repeatedly again until you get
-@emph{back to} that frame. Then use @samp{next} to step through that
-frame. By stepping, you will see where the loop starts and ends. Also
-please examine the data being used in the loop and try to determine why
-the loop does not exit when it should. Include all of this information
-in your bug report.
+@cindex debugging Emacs, tricks and techniques
+More detailed advice and other useful techniques for debugging Emacs
+are available in the file @file{etc/DEBUG} in the Emacs distribution.
+That file also includes instructions for investigating problems
+whereby Emacs stops responding (many people assume that Emacs is
+``hung,'' whereas in fact it might be in an infinite loop).
+
+To find the file @file{etc/DEBUG} in your Emacs installation, use the
+directory name stored in the variable @code{data-directory}.
@end itemize
Here are some things that are not necessary in a bug report:
changes will not affect it.
This is often time-consuming and not very useful, because the way we
-will find the bug is by running a single example under the debugger with
-breakpoints, not by pure deduction from a series of examples. You might
-as well save time by not searching for additional examples.
+will find the bug is by running a single example under the debugger
+with breakpoints, not by pure deduction from a series of examples.
+You might as well save time by not searching for additional examples.
+It is better to send the bug report right away, go back to editing,
+and find another bug to report.
Of course, if you can find a simpler example to report @emph{instead} of
the original one, that is a convenience. Errors in the output will be
However, simplification is not vital; if you can't do this or don't have
time to try, please report the bug with your original test case.
+@item
+A core dump file.
+
+Debugging the core dump might be useful, but it can only be done on
+your machine, with your Emacs executable. Therefore, sending the core
+dump file to the Emacs maintainers won't be useful. Above all, don't
+include the core file in an email bug report! Such a large message
+can be extremely inconvenient.
+
@item
A system-call trace of Emacs execution.
feel that the purpose needs explaining, it probably does---but put the
explanation in comments in the code. It will be more useful there.
-Please read the @file{ChangeLog} files in the @file{src} and @file{lisp}
-directories to see what sorts of information to put in, and to learn the
-style that we use. If you would like your name to appear in the header
-line, showing who made the change, send us the header line.
-@xref{Change Log}.
+Please read the @file{ChangeLog} files in the @file{src} and
+@file{lisp} directories to see what sorts of information to put in,
+and to learn the style that we use. @xref{Change Log}.
@item
When you write the fix, keep in mind that we can't install a change that
If you would like to help pretest Emacs releases to assure they work
well, or if you would like to work on improving Emacs, please contact
-the maintainers at @code{bug-gnu-emacs@@gnu.org}. A pretester
+the maintainers at @email{emacs-devel@@gnu.org}. A pretester
should be prepared to investigate bugs as well as report them. If you'd
like to work on improving Emacs, please ask for suggested projects or
suggest your own ideas.
If you have already written an improvement, please tell us about it. If
you have not yet started work, it is useful to contact
-@code{bug-gnu-emacs@@gnu.org} before you start; it might be
+@email{emacs-devel@@gnu.org} before you start; it might be
possible to suggest ways to make your extension fit in better with the
rest of Emacs.
-@node Service, Command Arguments, Contributing, Top
+The development version of Emacs can be downloaded from the CVS
+repository where it is actively maintained by a group of developers.
+See the Emacs project page
+@url{http://savannah.gnu.org/projects/emacs/} for details.
+
+@node Service, Copying, Contributing, Top
@section How To Get Help with GNU Emacs
If you need help installing, using or changing GNU Emacs, there are two
@itemize @bullet
@item
Send a message to the mailing list
-@code{help-gnu-emacs@@gnu.org}, or post your request on
+@email{help-gnu-emacs@@gnu.org}, or post your request on
newsgroup @code{gnu.emacs.help}. (This mailing list and newsgroup
interconnect, so it does not matter which one you use.)
The service directory is found in the file named @file{etc/SERVICE} in the
Emacs distribution.
@end itemize
+
+@ifnottex
+@lowersections
+@end ifnottex
+
+@ignore
+ arch-tag: c9cba76d-b2cb-4e0c-ae3f-19d5ef35817c
+@end ignore