This is Info file ../info/emacs, produced by Makeinfo-1.63 from the
input file emacs.texi.


File: emacs,  Node: Quitting,  Next: Lossage,  Prev: Customization,  Up: Top

Quitting and Aborting
=====================

`C-g'
     Quit.  Cancel running or partially typed command.

`C-]'
     Abort innermost recursive editing level and cancel the command
     which invoked it (`abort-recursive-edit').

`ESC ESC ESC'
     Either quit or abort, whichever makes sense
     (`keyboard-escape-quit').

`M-x top-level'
     Abort all recursive editing levels that are currently executing.

`C-x u'
     Cancel a previously made change in the buffer contents (`undo').

   There are two ways of canceling commands which are not finished
executing: "quitting" with `C-g', and "aborting" with `C-]' or `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.  (*Note Recursive Edit::.)

   Quitting with `C-g' is used for getting 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
*all* still be in the buffer, or it will *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
`C-g' characters to get out of a search (*note Incremental Search::.).

   `C-g' works by setting the variable `quit-flag' to `t' the instant
`C-g' is typed; Emacs Lisp checks this variable frequently and quits if
it is non-`nil'.  `C-g' is only actually executed as a command if you
type it while Emacs is waiting for input.

   If you quit with `C-g' a second time before the first `C-g' is
recognized, you activate the "emergency escape" feature and return to
the shell.  *Note Emergency Escape::.

   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.

   Aborting with `C-]' (`abort-recursive-edit') is used to get out of a
recursive editing level and cancel the command which invoked it.
Quitting with `C-g' does not do this, and could not do this, because it
is used to cancel a partially typed command *within* the recursive
editing level.  Both operations are useful.  For example, if you are in
a recursive edit and type `C-u 8' to enter a numeric argument, you can
cancel that argument with `C-g' and remain in the recursive edit.

   The command `ESC ESC ESC' (`keyboard-escape-quit') can either quit
or abort.  This key was defined because 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 `C-g'.  It can get out of
the minibuffer or a recursive edit, like `C-]'.  It can also get out of
splitting the frame into multiple windows, like `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 command `M-x top-level' is equivalent to "enough" `C-]' commands
to get you out of all the levels of recursive edits that you are in.
`C-]' gets you out one level at a time, but `M-x top-level' goes out
all levels at once.  Both `C-]' and `M-x top-level' are like all other
commands, and unlike `C-g', in that they take effect only when Emacs is
ready for a command.  `C-]' is an ordinary key and has its meaning only
because of its binding in the keymap.  *Note Recursive Edit::.

   `C-x u' (`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.  *Note Undo::.


File: emacs,  Node: Lossage,  Next: Bugs,  Prev: Quitting,  Up: Top

Dealing with Emacs Trouble
==========================

   This section describes various conditions in which Emacs fails to
work normally, and how to recognize them and correct them.

* Menu:

* DEL Gets Help::       What to do if 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.


File: emacs,  Node: DEL Gets Help,  Next: Stuck Recursive,  Up: Lossage

If DEL Fails to Delete
----------------------

   If you find that DEL enters Help like `Control-h' instead of
deleting a character, your terminal is sending the wrong code for DEL.
You can work around this problem by changing the keyboard translation
table (*note Keyboard Translations::.).


File: emacs,  Node: Stuck Recursive,  Next: Screen Garbled,  Prev: DEL Gets Help,  Up: Lossage

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.

   If the mode line has square brackets `[...]' around the parentheses
that contain the names of the major and minor modes, you have entered a
recursive editing level.  If you did not do this on purpose, or if you
don't understand what that means, you should just get out of the
recursive editing level.  To do so, type `M-x top-level'.  This is
called getting back to top level.  *Note Recursive Edit::.


File: emacs,  Node: Screen Garbled,  Next: Text Garbled,  Prev: Stuck Recursive,  Up: Lossage

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 `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 *Note Text
Garbled::.)

   Display updating problems often result from an incorrect termcap
entry for the terminal you are using.  The file `etc/TERMS' in the Emacs
distribution gives the fixes for known problems of this sort.
`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.


File: emacs,  Node: Text Garbled,  Next: Unasked-for Search,  Prev: Screen Garbled,  Up: Lossage

Garbage in the Text
-------------------

   If `C-l' shows that the text is wrong, try undoing the changes to it
using `C-x u' until it gets back to a state you consider correct.  Also
try `C-h l' to find out what command you typed to produce the observed
results.

   If a large portion of text appears to be missing at the beginning or
end of the buffer, check for the word `Narrow' in the mode line.  If it
appears, the text you don't see is probably still present, but
temporarily off-limits.  To make it accessible again, type `C-x n w'.
*Note Narrowing::.


File: emacs,  Node: Unasked-for Search,  Next: Memory Full,  Prev: Text Garbled,  Up: Lossage

Spontaneous Entry to Incremental Search
---------------------------------------

   If Emacs spontaneously displays `I-search:' at the bottom of the
screen, it means that the terminal is sending `C-s' and `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 `C-s'.  (One way to increase the amount of
padding is to set the variable `baud-rate' to a larger value.  Its
value is the terminal output speed, measured in the conventional units
of baud.)

   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
`enable-flow-control'.

   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 `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 `.emacs' file:

     (enable-flow-control-on "vt100" "h19")

   When flow control is enabled, you must type `C-\' to get the effect
of a `C-s', and type `C-^' to get the effect of a `C-q'.  (These
aliases work by means of keyboard translations; see *Note Keyboard
Translations::.)


File: emacs,  Node: Memory Full,  Next: After a Crash,  Prev: Unasked-for Search,  Up: Lossage

Running out of Memory
---------------------

   If you get the error message `Virtual memory exceeded', save your
modified buffers with `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 `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 `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.

   Do not use `M-x buffer-menu' to save or kill buffers when you run
out of memory, because the buffer menu needs a fair amount memory
itself, and the reserve supply may not be enough.


File: emacs,  Node: After a Crash,  Next: Emergency Escape,  Prev: Memory Full,  Up: Lossage

Recovery After a Crash
----------------------

   If Emacs or the computer crashes, you can recover the files you were
editing at the time of the crash from their auto-save files.  To do
this, start Emacs again and type the command `M-x recover-session'.

   This command initially displays a buffer which lists interrupted
session files, each with its date.  You must choose which session to
recover from.  Typically the one you want is the most recent one.  Move
point to the one you choose, and type `C-c C-c'.

   Then `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 `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 `yes'.  If you do, Emacs
visits the file but gets the text from the auto-save file.

   When `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.


File: emacs,  Node: Emergency Escape,  Next: Total Frustration,  Prev: After a Crash,  Up: Lossage

Emergency Escape
----------------

   Because at times there have been bugs causing Emacs to loop without
checking `quit-flag', a special feature causes Emacs to be suspended
immediately if you type a second `C-g' while the flag is already set,
so you can always get out of GNU Emacs.  Normally Emacs recognizes and
clears `quit-flag' (and quits!) quickly enough to prevent this from
happening.

   When you resume Emacs after a suspension caused by multiple `C-g', it
asks two questions before going back to what it had been doing:

     Auto-save? (y or n)
     Abort (and dump core)? (y or n)

Answer each one with `y' or `n' followed by RET.

   Saying `y' to `Auto-save?' causes immediate auto-saving of all
modified buffers in which auto-saving is enabled.

   Saying `y' to `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 `n', execution does
continue.  With luck, GNU Emacs will ultimately check `quit-flag' and
quit normally.  If not, and you type another `C-g', it is suspended
again.

   If Emacs is not really hung, just slow, you may invoke the double
`C-g' feature without really meaning to.  Then just resume and answer
`n' to both questions, and you will arrive at your former state.
Presumably the quit you requested will happen soon.

   The double-`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.


File: emacs,  Node: Total Frustration,  Prev: Emergency Escape,  Up: Lossage

Help for Total Frustration
--------------------------

   If using Emacs (or something else) becomes terribly frustrating and
none of the techniques described above solve the problem, Emacs can
still help you.

   First, if the Emacs you are using is not responding to commands, type
`C-g C-g' to get out of it and then start a new one.

   Second, type `M-x doctor RET'.

   The doctor will help you feel better.  Each time you say something to
the doctor, you must end it by typing RET RET.  This lets the doctor
know you are finished.


File: emacs,  Node: Bugs,  Next: Contributing,  Prev: Lossage,  Up: Top

Reporting Bugs
==============

   Sometimes you will encounter a bug in Emacs.  Although we cannot
promise we can or will fix the bug, and we might not even agree that it
is a bug, we want to hear about problems you encounter.  Often we agree
they are bugs and want to fix them.

   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.

* Menu:

* Criteria:  Bug Criteria.	 Have you really found a bug?
* Understanding Bug Reporting::	 How to report a bug effectively.
* Checklist::			 Steps to follow for a good bug report.
* Sending Patches::		 How to send a patch for GNU Emacs.


File: emacs,  Node: Bug Criteria,  Next: Understanding Bug Reporting,  Up: Bugs

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 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 wrong thing but the problem corrects itself if you type
`C-l', it is a case of incorrect display updating.

   Taking forever to complete a command can be a bug, but you must make
certain that it was really Emacs's fault.  Some commands simply take a
long time.  Type `C-g' and then `C-h l' to see whether the input Emacs
received was what you intended to type; if the input was such that you
*know* it should have been processed quickly, report a bug.  If you
don't know whether the command should take a long time, find out by
looking in the manual or by asking for assistance.

   If a command you are familiar with causes an Emacs error message in a
case where its usual definition ought to be reasonable, it is probably a
bug.

   If a command does the wrong thing, that is a bug.  But be sure you
know for certain what it ought to have done.  If you aren't familiar
with the command, or don't know for certain how the command is supposed
to work, 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.

   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
you should report.  The manual's job is to make everything clear to
people who are not Emacs experts--including you.  It is just as
important to report documentation bugs as program bugs.

   If the on-line documentation string of a function or variable
disagrees with the manual, one of them must be wrong; that is a bug.


File: emacs,  Node: Understanding Bug Reporting,  Next: Checklist,  Prev: Bug Criteria,  Up: Bugs

Understanding Bug Reporting
---------------------------

   When you decide that there is a bug, it is important to report it
and to report it in a way which is useful.  What is most useful is an
exact description of what commands you type, starting with the shell
command to run Emacs, until the problem happens.

   The most important principle in reporting a bug is to report *facts*,
not hypotheses or categorizations.  It is always easier to report the
facts, but people seem to prefer to strain to posit explanations and
report them instead.  If the explanations are based on guesses about
how Emacs is implemented, they will be useless; we will have to try to
figure out what the facts must have been to lead to such speculations.
Sometimes this is impossible.  But in any case, it is unnecessary work
for us.

   For example, suppose that you type `C-x C-f /glorp/baz.ugh RET',
visiting a file which (you know) happens to be rather large, and Emacs
prints out `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
and nothing but the facts.

   Do not assume that the problem is due to the size of the file and
say, "When I visit a large file, Emacs prints out `I feel pretty
today'." This is what we mean by "guessing explanations".  The problem
is just as likely to be due to the fact that there is a `z' in the file
name.  If this is so, then when we got your report, we would try out
the problem with some "large file", probably with no `z' in its name,
and not find anything wrong.  There is no way in the world that we
could guess that we should try visiting a file with a `z' in its name.

   Alternatively, the problem might be due to the fact that the file
starts with exactly 25 spaces.  For this reason, you should make sure
that you inform us of the exact contents of any file that is needed to
reproduce the bug.  What if the problem only occurs when you have typed
the `C-x C-a' command previously?  This is why we ask you to give the
exact sequence of characters you typed since starting the Emacs session.

   You should not even say "visit a file" instead of `C-x C-f' unless
you *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 `RET A B C RET C-p'," if that is the way you entered
the text.


File: emacs,  Node: Checklist,  Next: Sending Patches,  Prev: Understanding Bug Reporting,  Up: Bugs

Checklist for Bug Reports
-------------------------

   The best way to send a bug report is to mail it electronically to the
Emacs maintainers at `bug-gnu-emacs@prep.ai.mit.edu'.  (If you want to
suggest a change as an improvement, use the same address.)

   If you'd like to read the bug reports, you can find them on the
newsgroup `gnu.emacs.bug'; keep in mind, however, that as a 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.

   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:

GNU Emacs Bugs
Free Software Foundation
59 Temple Place, Suite 330
Boston, MA 02111-1307 USA

   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.

   A convenient way to send a bug report for Emacs is to use the command
`M-x report-emacs-bug'.  This sets up a mail buffer (*note Sending
Mail::.) and automatically inserts *some* of the essential information.
However, it cannot supply all the necessary information; you should
still read and follow the guidelines below, so you can enter the other
crucial information by hand before you send the message.

   To enable maintainers to investigate a bug, your report should
include all these things:

   * The version number of Emacs.  Without this, we won't know whether
     there is any point in looking for the bug in the current version
     of GNU Emacs.

     You can get the version number by typing `M-x emacs-version RET'.
     If that command does not work, you probably have something other
     than GNU Emacs, so you will have to report the bug somewhere else.

   * The type of machine you are using, and the operating system name
     and version number.  `M-x emacs-version RET' provides this
     information too.  Copy its output from the `*Messages*' buffer, so
     that you get it all and get it accurately.

   * The operands given to the `configure' command when Emacs was
     installed.

   * A complete list of any modifications you have made to the Emacs
     source.  (We may not have time to investigate the bug unless it
     happens in an unmodified Emacs.  But if you've made modifications
     and you don't tell us, you are sending us on a wild goose chase.)

     Be precise about these changes.  A description in English is not
     enough--send a context diff for them.

     Adding files of your own, or porting to another machine, is a
     modification of the source.

   * Details of any other deviations from the standard procedure for
     installing GNU Emacs.

   * The complete text of any files needed to reproduce the bug.

     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 newline after the last line in
     the buffer (nothing ought to care whether the last line is
     terminated, but try telling the bugs that).

   * The precise commands we need to type to reproduce the bug.

     The easy way to record the input to Emacs precisely is to write a
     dribble file.  To start the file, execute the Lisp expression

          (open-dribble-file "~/dribble")

     using `M-:' or from the `*scratch*' buffer just after starting
     Emacs.  From then on, Emacs copies all your input to the specified
     dribble file until the Emacs process is killed.

   * For possible display bugs, the terminal type (the value of
     environment variable `TERM'), the complete termcap entry for the
     terminal from `/etc/termcap' (since that file is not identical on
     all machines), and the output that Emacs actually sent to the
     terminal.

     The way to collect the terminal output is to execute the Lisp
     expression

          (open-termscript "~/termscript")

     using `M-:' or from the `*scratch*' buffer just after starting
     Emacs.  From then on, Emacs copies all terminal output to the
     specified termscript file as well, until the Emacs process is
     killed.  If the problem happens when Emacs starts up, put this
     expression into your `.emacs' file so that the termscript file
     will be open when Emacs displays the screen for the first time.

     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.

   * A description of what behavior you observe that you believe is
     incorrect.  For example, "The Emacs process gets a fatal signal,"
     or, "The resulting text is as follows, which I think is wrong."

     Of course, if the bug is that Emacs gets a fatal signal, then one
     can't miss it.  But if the bug is incorrect text, the maintainer
     might fail to notice what is wrong.  Why leave it to chance?

     Even if the problem you experience is a fatal signal, you should
     still say so explicitly.  Suppose something strange is going on,
     such as, your copy of the source is out of sync, or you have
     encountered a bug in the C library on your system.  (This has
     happened!)  Your copy might crash and the copy here might not.  If
     you *said* to expect a crash, then when Emacs here fails to crash,
     we would know that the bug was not happening.  If you don't say to
     expect a crash, then we would not know whether the bug was
     happening--we would not be able to draw any conclusion from our
     observations.

   * 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
     backtrace showing how the Lisp program in Emacs arrived at the
     error.

     To get the error message text accurately, copy it from the
     `*Messages*' buffer into the bug report.  Copy all of it, not just
     part.

     To make a backtrace for the error, evaluate the Lisp expression
     `(setq 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.

     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 the whole error message.

   * Check whether any programs you have loaded into the Lisp world,
     including your `.emacs' file, set any variables that may affect the
     functioning of Emacs.  Also, see whether the problem happens in a
     freshly started Emacs without loading your `.emacs' file (start
     Emacs with the `-q' switch to prevent loading the init file.)  If
     the problem does *not* occur then, you must report the precise
     contents of any programs that you must load into the Lisp world in
     order to cause the problem to occur.

   * If the problem does depend on an init file or other Lisp programs
     that are not part of the standard Emacs system, then you should
     make sure it is not a bug in those programs by complaining to
     their maintainers first.  After they verify that they are using
     Emacs in a way that is supposed to work, they should report the
     bug.

   * If you wish to mention something in the GNU Emacs source, show the
     line of code with a few lines of context.  Don't just give a line
     number.

     The line numbers in the development sources don't match those in
     your sources.  It would take extra work for the maintainers to
     determine what code is in your version at a given line number, and
     we could not be certain.

   * Additional information from a C debugger such as GDB might enable
     someone to find a problem on a machine which he does not have
     available.  If you don't know how to use GDB, please read the GDB
     manual--it is not very long, and using GDB is easy.  You can find
     the GDB distribution, including the GDB manual in online form, in
     most of the same places you can find the Emacs distribution.

     However, you need to think when you collect the additional
     information if you want it to show what causes the bug.

     For example, many people send just a backtrace, but that is not
     very useful by itself.  A simple backtrace with arguments often
     conveys little about what is happening inside GNU Emacs, because
     most of the arguments listed in the backtrace are pointers to Lisp
     objects.  The numeric values of these pointers have no
     significance whatever; all that matters is the contents of the
     objects they point to (and most of the contents are themselves
     pointers).

     To provide useful information, you need to show the values of Lisp
     objects in Lisp notation.  Do this for each variable which is a
     Lisp object, in several stack frames near the bottom of the stack.
     Look at the source to see which variables are Lisp objects,
     because the debugger thinks of them as integers.

     To show a variable's value in Lisp syntax, first print its value,
     then use the user-defined GDB command `pr' to print the Lisp
     object in Lisp syntax.  (If you must use another debugger, call
     the function `debug_print' with the object as an argument.)  The
     `pr' command is defined by the file `.gdbinit' in the `src'
     subdirectory, and it works only if you are debugging a running
     process (not with a core dump).

     To make Lisp errors stop Emacs and return to GDB, put a breakpoint
     at `Fsignal'.

     To find out which Lisp functions are running, using GDB, move up
     the stack, and each time you get to a frame for the function
     `Ffuncall', type these GDB commands:

          p *args
          pr

     To print the first argument that the function received, use these
     commands:

          p args[1]
          pr

     You can print the other arguments likewise.  The argument `nargs'
     of `Ffuncall' says how many arguments `Ffuncall' received; these
     include the Lisp function itself and the arguments for that
     function.

   * 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 `C-c' at the GDB job.)  Then try
     stepping with `step'.  If Emacs is hung, the `step' command won't
     return.  If it is looping, `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 `finish'.  Each time you use it, Emacs resumes execution
     until it exits one stack frame.  Keep typing `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 `finish' repeatedly again until you get
     *back to* that frame.  Then use `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.

   Here are some things that are not necessary in a bug report:

   * A description of the envelope of the bug--this is not necessary
     for a reproducible bug.

     Often people who encounter a bug spend a lot of time investigating
     which changes to the input file will make the bug go away and which
     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.

     Of course, if you can find a simpler example to report *instead* of
     the original one, that is a convenience.  Errors in the output
     will be easier to spot, running under the debugger will take less
     time, etc.

     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.

   * A system call trace of Emacs execution.

     System call traces are very useful for certain special kinds of
     debugging, but in most cases they give little useful information.
     It is therefore strange that many people seem to think that *the*
     way to report information about a crash is to send a system call
     trace.

     In most programs, a backtrace is normally far, far more
     informative than a system call trace.  Even in Emacs, a simple
     backtrace is generally more informative, though to give full
     information you should supplement the backtrace by displaying
     variable values and printing them as Lisp objects with `pr' (see
     above).

   * A patch for the bug.

     A patch for the bug is useful if it is a good one.  But don't omit
     the other information that a bug report needs, such as the test
     case, on the assumption that a patch is sufficient.  We might see
     problems with your patch and decide to fix the problem another
     way, or we might not understand it at all.  And if we can't
     understand what bug you are trying to fix, or why your patch
     should be an improvement, we mustn't install it.

     *Note Sending Patches::, for guidelines on how to make it easy for
     us to understand and install your patches.

   * A guess about what the bug is or what it depends on.

     Such guesses are usually wrong.  Even experts can't guess right
     about such things without first using the debugger to find the
     facts.


File: emacs,  Node: Sending Patches,  Prev: Checklist,  Up: Bugs

Sending Patches for GNU Emacs
-----------------------------

   If you would like to write bug fixes or improvements for GNU Emacs,
that is very helpful.  When you send your changes, please follow these
guidelines to make it easy for the maintainers to use them.  If you
don't follow these guidelines, your information might still be useful,
but using it will take extra work.  Maintaining GNU Emacs is a lot of
work in the best of circumstances, and we can't keep up unless you do
your best to help.

   * Send an explanation with your changes of what problem they fix or
     what improvement they bring about.  For a bug fix, just include a
     copy of the bug report, and explain why the change fixes the bug.

     (Referring to a bug report is not as good as including it, because
     then we will have to look it up, and we have probably already
     deleted it if we've already fixed the bug.)

   * Always include a proper bug report for the problem you think you
     have fixed.  We need to convince ourselves that the change is
     right before installing it.  Even if it is correct, we might have
     trouble understanding it if we don't have a way to reproduce the
     problem.

   * Include all the comments that are appropriate to help people
     reading the source in the future understand why this change was
     needed.

   * Don't mix together changes made for different reasons.  Send them
     *individually*.

     If you make two changes for separate reasons, then we might not
     want to install them both.  We might want to install just one.  If
     you send them all jumbled together in a single set of diffs, we
     have to do extra work to disentangle them--to figure out which
     parts of the change serve which purpose.  If we don't have time
     for this, we might have to ignore your changes entirely.

     If you send each change as soon as you have written it, with its
     own explanation, then two changes never get tangled up, and we can
     consider each one properly without any extra work to disentangle
     them.

   * Send each change as soon as that change is finished.  Sometimes
     people think they are helping us by accumulating many changes to
     send them all together.  As explained above, this is absolutely
     the worst thing you could do.

     Since you should send each change separately, you might as well
     send it right away.  That gives us the option of installing it
     immediately if it is important.

   * Use `diff -c' to make your diffs.  Diffs without context are hard
     to install reliably.  More than that, they are hard to study; we
     must always study a patch to decide whether we want to install it.
     Unidiff format is better than contextless diffs, but not as easy
     to read as `-c' format.

     If you have GNU diff, use `diff -c -F'^[_a-zA-Z0-9$]+ *('' when
     making diffs of C code.  This shows the name of the function that
     each change occurs in.

   * Write the change log entries for your changes.  This is both to
     save us the extra work of writing them, and to help explain your
     changes so we can understand them.

     The purpose of the change log is to show people where to find what
     was changed.  So you need to be specific about what functions you
     changed; in large functions, it's often helpful to indicate where
     within the function the change was.

     On the other hand, once you have shown people where to find the
     change, you need not explain its purpose in the change log.  Thus,
     if you add a new function, all you need to say about it is that it
     is new.  If you 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 `ChangeLog' files in the `src' and `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.  *Note Change Log::.

   * When you write the fix, keep in mind that we can't install a
     change that would break other systems.  Please think about what
     effect your change will have if compiled on another type of system.

     Sometimes people send fixes that *might* be an improvement in
     general--but it is hard to be sure of this.  It's hard to install
     such changes because we have to study them very carefully.  Of
     course, a good explanation of the reasoning by which you concluded
     the change was correct can help convince us.

     The safest changes are changes to the configuration files for a
     particular machine.  These are safe because they can't create new
     bugs on other machines.

     Please help us keep up with the workload by designing the patch in
     a form that is clearly safe to install.


File: emacs,  Node: Contributing,  Next: Service,  Prev: Bugs,  Up: Top

Contributing to Emacs Development
=================================

   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 `bug-gnu-emacs@prep.ai.mit.edu'.  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
`bug-gnu-emacs@prep.ai.mit.edu' before you start; it might be possible
to suggest ways to make your extension fit in better with the rest of
Emacs.


File: emacs,  Node: Service,  Next: Command Arguments,  Prev: Contributing,  Up: Top

How To Get Help with GNU Emacs
==============================

   If you need help installing, using or changing GNU Emacs, there are
two ways to find it:

   * Send a message to the mailing list
     `help-gnu-emacs@prep.ai.mit.edu', or post your request on
     newsgroup `gnu.emacs.help'.  (This mailing list and newsgroup
     interconnect, so it does not matter which one you use.)

   * Look in the service directory for someone who might help you for a
     fee.  The service directory is found in the file named
     `etc/SERVICE' in the Emacs distribution.


File: emacs,  Node: Command Arguments,  Next: Antinews,  Prev: Service,  Up: Top

Command Line Arguments
**********************

   GNU Emacs supports command line arguments to request various actions
when invoking Emacs.  These are for compatibility with other editors and
for sophisticated activities.  We don't recommend using them for
ordinary editing.

   Arguments starting with `-' are "options".  Other arguments specify
files to visit.  Emacs visits the specified files while it starts up.
The last file name on your command line becomes the current buffer; the
other files are also present in other buffers.

   You can use options to specify various other things, such as the size
and position of the X window Emacs uses, its colors, and so on.  A few
options support advanced usage, such as running Lisp functions on files
in batch mode.  The sections of this chapter describe the available
options, arranged according to their purpose.

   There are two ways of writing options: the short forms that start
with a single `-', and the long forms that start with `--'.  For
example, `-d' is a short form and `--display' is the corresponding long
form.

   The long forms with `--' are easier to remember, but longer to type.
However, you don't have to spell out the whole option name; any
unambiguous abbreviation is enough.  When a long option takes an
argument, you can use either a space or an equal sign to separate the
option name and the argument.  Thus, you can write either `--display
sugar-bombs:0.0' or `--display=sugar-bombs:0.0'.  We recommend an equal
sign because it makes the relationship clearer, and the tables below
always show an equal sign.

   Most options specify how to initialize Emacs, or set parameters for
the Emacs session.  We call them "initial options".  A few options
specify things to do: for example, load libraries, call functions, or
exit Emacs.  These are called "action options".  These and file names
together are called "action arguments".  Emacs processes all the action
arguments in the order they are written.

* Menu:

* Action Arguments::	Arguments to visit files, load libraries,
			  and call functions.
* Initial Options::     Arguments that take effect while starting Emacs.
* Command Example::     Examples of using command line arguments.
* Resume Arguments::	Specifying arguments when you resume a running Emacs.
* Environment::         Environment variables that Emacs uses.

* Display X::           Changing the default display and using remote login.
* Font X::	        Choosing a font for text, under X.
* Colors X::	        Choosing colors, under X.
* Window Size X::       Start-up window size, under X.
* Borders X::	        Internal and external borders, under X.
* Title X::             Specifying the initial frame's title.
* Icons X::             Choosing what sort of icon to use, under X.
* Resources X::         Advanced use of classes and resources, under X.
* Lucid Resources::     X resources for Lucid menus.
* Motif Resources::     X resources for Motif menus.


File: emacs,  Node: Action Arguments,  Next: Initial Options,  Up: Command Arguments

Action Arguments
================

   Here is a table of the action arguments and options:

`FILE'
     Visit FILE using `find-file'.  *Note Visiting::.

`+LINENUM FILE'
     Visit FILE using `find-file', then go to line number LINENUM in it.

`-l FILE'
`--load=FILE'
     Load a file FILE of Lisp code with the function `load'.  *Note
     Lisp Libraries::.

`-f FUNCTION'
`--funcall=FUNCTION'
     Call Lisp function FUNCTION with no arguments.

`--eval EXPRESSION'
     Evaluate Lisp expression EXPRESSION.

`--insert=FILE'
     Insert the contents of FILE into the current buffer.  This is like
     what `M-x insert-file' does.  *Note Misc File Ops::.

`--kill'
     Exit from Emacs without asking for confirmation.

   The init file can access the values of the action arguments as the
elements of a list in the variable `command-line-args'.  The init file
can override the normal processing of the action arguments, or define
new ones, by reading and setting this variable.


File: emacs,  Node: Initial Options,  Next: Command Example,  Prev: Action Arguments,  Up: Command Arguments

Initial Options
===============

   The initial options specify parameter for the Emacs session.  This
section describes the more general initial options; some other options
specifically related to X Windows appear in the following sections.

   Some initial options affect the loading of init files.  The normal
actions of Emacs are to first load `site-start.el' if it exists, then
your own init file `~/.emacs' if it exists, and finally `default.el' if
it exists; certain options prevent loading of some of these files or
substitute other files for them.

`-t DEVICE'
`--terminal=DEVICE'
     Use DEVICE as the device for terminal input and output.

`-d DISPLAY'
`--display=DISPLAY'
     Use the X Window System and use the display named DISPLAY to open
     the initial Emacs frame.

`-nw'
`--no-windows'
     Don't communicate directly with X, disregarding the `DISPLAY'
     environment variable even if it is set.

`-batch'
`--batch'
     Run Emacs in "batch mode", which means that the text being edited
     is not displayed and the standard terminal interrupt characters
     such as `C-z' and `C-c' continue to have their normal effect.
     Emacs in batch mode outputs to `stderr' only what would normally
     be printed in the echo area under program control.

     Batch mode is used for running programs written in Emacs Lisp from
     shell scripts, makefiles, and so on.  Normally the `-l' option or
     `-f' option will be used as well, to invoke a Lisp program to do
     the batch processing.

     `-batch' implies `-q' (do not load an init file).  It also causes
     Emacs to kill itself after all command options have been
     processed.  In addition, auto-saving is not done except in buffers
     for which it has been explicitly requested.

`-q'
`--no-init-file'
     Do not load your Emacs init file `~/.emacs', or `default.el'
     either.

`--no-site-file'
     Do not load `site-start.el'.  The options `-q', `-u' and `-batch'
     have no effect on the loading of this file--this is the only
     option that blocks it.

`-u USER'
`--user=USER'
     Load USER's Emacs init file `~USER/.emacs' instead of your own.

`--debug-init'
     Enable the Emacs Lisp debugger for errors in the init file.


File: emacs,  Node: Command Example,  Next: Resume Arguments,  Prev: Initial Options,  Up: Command Arguments

Command Argument Example
========================

   Here is an example of using Emacs with arguments and options.  It
assumes you have a Lisp program file called `hack-c.el' which, when
loaded, performs some useful operation on current buffer, expected to be
a C program.

     emacs -batch foo.c -l hack-c -f save-buffer >& log

This says to visit `foo.c', load `hack-c.el' (which makes changes in
the visited file), save `foo.c' (note that `save-buffer' is the
function that `C-x C-s' is bound to), and then exit back to the shell
(because of `-batch').  `-batch' also guarantees there will be no
problem redirecting output to `log', because Emacs will not assume that
it has a display terminal to work with.

