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Checklist for Bug Reports
The best way to send a bug report is to mail it electronically to the
Emacs maintainers at `email@example.com'.
If you'd like to read the bug reports, you can find them on the
repeater newsgroup `gnu.emacs.bugs'; 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.
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
to this address:
GNU Emacs Bugs
Free Software Foundation
675 Mass Ave
Cambridge, MA 02139
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.
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.
* The operands you gave to the `configure' command when you 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 don't tell us, then 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 (such as a machine description for a
machine we don't support) 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 to write
a dribble file. To start the file, execute the Lisp expression
using `M-ESC' 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
The way to collect the terminal output is to execute the Lisp
using `M-ESC' 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 would 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
If the manifestation of the bug is an Emacs error message, it is
important to report not just the text of the error message but a
backtrace showing how the Lisp program in Emacs arrived at the
error. To make the backtrace, execute 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 Lisp debugger to run, showing 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. Do note the error message the first time
the bug happens, so if you can't make it happen again, you can
report at least the 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
* If you wish to mention something in the GNU Emacs source, show the
portion in its 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 debugger might enable someone to
find a problem on a machine which he does not have available.
However, you need to think when you collect this information if
you want it to be useful.
For example, many people send just a backtrace, but that is never
useful by itself. A simple backtrace with arguments 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
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 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 `src/.gdbinit' in the Emacs distribution,
and it works only if you are debugging a running process (not with
a core dump).
Here are some things that are not necessary:
* 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 doing this.
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
However, simplification is not vital; if you don't want to do this,
please report the bug with your original test case.
* A patch for the bug.
A patch for the bug is useful if it is a good one. But don't omit
the necessary information, such as the test case, on the
assumption that a patch is all we need. 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. A
test case will help us to understand.
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
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