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Known Problems with GNU Emacs

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Copyright (C) 1987-1989, 1993-1999, 2001-2012
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  Free Software Foundation, Inc.
See the end of the file for license conditions.


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This file describes various problems that have been encountered
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in compiling, installing and running GNU Emacs.  Try doing C-c C-t
and browsing through the outline headers.  (See C-h m for help on
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Outline mode.)  Information about systems that are no longer supported,
and old Emacs releases, has been removed.  Consult older versions of
this file if you are interested in that information.
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* Mule-UCS doesn't work in Emacs 23.
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It's completely redundant now, as far as we know.

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* Emacs startup failures
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** Emacs fails to start, complaining about missing fonts.
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A typical error message might be something like
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  No fonts match `-*-fixed-medium-r-*--6-*-*-*-*-*-iso8859-1'
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This happens because some X resource specifies a bad font family for
Emacs to use.  The possible places where this specification might be
are:
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  - in your ~/.Xdefaults file
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  - client-side X resource file, such as  ~/Emacs or
    /usr/X11R6/lib/app-defaults/Emacs or
    /usr/X11R6/lib/X11/app-defaults/Emacs
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One of these files might have bad or malformed specification of a
fontset that Emacs should use.  To fix the problem, you need to find
the problematic line(s) and correct them.
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** Emacs aborts while starting up, only when run without X.
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This problem often results from compiling Emacs with GCC when GCC was
installed incorrectly.  The usual error in installing GCC is to
specify --includedir=/usr/include.  Installation of GCC makes
corrected copies of the system header files.  GCC is supposed to use
the corrected copies in preference to the original system headers.
Specifying --includedir=/usr/include causes the original system header
files to be used.  On some systems, the definition of ioctl in the
original system header files is invalid for ANSI C and causes Emacs
not to work.
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The fix is to reinstall GCC, and this time do not specify --includedir
when you configure it.  Then recompile Emacs.  Specifying --includedir
is appropriate only in very special cases and it should *never* be the
same directory where system header files are kept.
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** Emacs does not start, complaining that it cannot open termcap database file.
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If your system uses Terminfo rather than termcap (most modern
systems do), this could happen if the proper version of
ncurses is not visible to the Emacs configure script (i.e. it
cannot be found along the usual path the linker looks for
libraries). It can happen because your version of ncurses is
obsolete, or is available only in form of binaries.
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The solution is to install an up-to-date version of ncurses in
the developer's form (header files, static libraries and
symbolic links); in some GNU/Linux distributions (e.g. Debian)
it constitutes a separate package.
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** Emacs 20 and later fails to load Lisp files at startup.
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The typical error message might be like this:
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  "Cannot open load file: fontset"
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This could happen if you compress the file lisp/subdirs.el.  That file
tells Emacs what are the directories where it should look for Lisp
files.  Emacs cannot work with subdirs.el compressed, since the
Auto-compress mode it needs for this will not be loaded until later,
when your .emacs file is processed.  (The package `fontset.el' is
required to set up fonts used to display text on window systems, and
it's loaded very early in the startup procedure.)
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Similarly, any other .el file for which there's no corresponding .elc
file could fail to load if it is compressed.
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The solution is to uncompress all .el files that don't have a .elc file.
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Another possible reason for such failures is stale *.elc files
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lurking somewhere on your load-path -- see the next section.
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** Emacs prints an error at startup after upgrading from an earlier version.
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An example of such an error is:
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  x-complement-fontset-spec: "Wrong type argument: stringp, nil"
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This can be another symptom of stale *.elc files in your load-path.
The following command will print any duplicate Lisp files that are
present in load-path:
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    emacs -batch -f list-load-path-shadows
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If this command prints any file names, some of these files are stale,
and should be deleted or their directories removed from your
load-path.
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** With X11R6.4, public-patch-3, Emacs crashes at startup.
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Reportedly this patch in X fixes the problem.
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    --- xc/lib/X11/imInt.c~	Wed Jun 30 13:31:56 1999
    +++ xc/lib/X11/imInt.c	Thu Jul  1 15:10:27 1999
    @@ -1,4 +1,4 @@
    -/* $TOG: imInt.c /main/5 1998/05/30 21:11:16 kaleb $ */
    +/* $TOG: imInt.c /main/5 1998/05/30 21:11:16 kaleb $  */
     /******************************************************************
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                Copyright 1992, 1993, 1994 by FUJITSU LIMITED
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    @@ -166,8 +166,8 @@
     _XimMakeImName(lcd)
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         XLCd      lcd;
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     {
    -    char* begin;
    -    char* end;
    +    char* begin = NULL;
    +    char* end = NULL;
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         char* ret;
         int	i = 0;
         char* ximmodifier = XIMMODIFIER;
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    @@ -182,7 +182,11 @@
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         }
         ret = Xmalloc(end - begin + 2);
         if (ret != NULL) {
    -           (void)strncpy(ret, begin, end - begin + 1);
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    +	if (begin != NULL) {
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    +             (void)strncpy(ret, begin, end - begin + 1);
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    +        } else {
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    +     ret[0] = '\0';
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    +	}
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            ret[end - begin + 1] = '\0';
         }
         return ret;
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** Emacs crashes on startup after a glibc upgrade.

This is caused by a binary incompatible change to the malloc
implementation in glibc 2.5.90-22.  As a result, Emacs binaries built
using prior versions of glibc crash when run under 2.5.90-22.

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This problem was first seen in pre-release versions of Fedora 7, and
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may be fixed in the final Fedora 7 release.  To stop the crash from
happening, first try upgrading to the newest version of glibc; if this
does not work, rebuild Emacs with the same version of glibc that you
will run it under.  For details, see

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=239344

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* Crash bugs
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** Emacs crashes when running in a terminal, if compiled with GCC 4.5.0
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This version of GCC is buggy: see

  http://debbugs.gnu.org/cgi/bugreport.cgi?bug=6031
  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43904

You can work around this error in gcc-4.5 by omitting sibling call
optimization.  To do this, configure Emacs with

 CFLAGS="-g -O2 -fno-optimize-sibling-calls" ./configure

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** Emacs compiled with GCC 4.6.1 crashes on MS-Windows when C-g is pressed

This is known to happen when Emacs is compiled with MinGW GCC 4.6.1
with the -O2 option (which is the default in the Windows build).  The
reason is a bug in MinGW GCC 4.6.1; to work around, either add the
`-fno-omit-frame-pointer' switch to GCC or compile without
optimizations (`--no-opt' switch to the configure.bat script).

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** Emacs crashes in x-popup-dialog.
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This can happen if the dialog widget cannot find the font it wants to
use.  You can work around the problem by specifying another font with
an X resource--for example, `Emacs.dialog*.font: 9x15' (or any font that
happens to exist on your X server).
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** Emacs crashes when you use Bibtex mode.
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This happens if your system puts a small limit on stack size.  You can
prevent the problem by using a suitable shell command (often `ulimit')
to raise the stack size limit before you run Emacs.
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Patches to raise the stack size limit automatically in `main'
(src/emacs.c) on various systems would be greatly appreciated.
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** Error message `Symbol's value as variable is void: x', followed by
a segmentation fault and core dump.
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This has been tracked to a bug in tar!  People report that tar erroneously
added a line like this at the beginning of files of Lisp code:
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   x FILENAME, N bytes, B tape blocks
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If your tar has this problem, install GNU tar--if you can manage to
untar it :-).
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** Crashes when displaying GIF images in Emacs built with version
libungif-4.1.0 are resolved by using version libungif-4.1.0b1.
Configure checks for the correct version, but this problem could occur
if a binary built against a shared libungif is run on a system with an
older version.
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** Emacs aborts inside the function `tparam1'.
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This can happen if Emacs was built without terminfo support, but the
terminal's capabilities use format that is only supported by terminfo.
If your system has ncurses installed, this might happen if your
version of ncurses is broken; upgrading to a newer version of ncurses
and reconfiguring and rebuilding Emacs should solve this.
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All modern systems support terminfo, so even if ncurses is not the
problem, you should look for a way to configure Emacs so that it uses
terminfo when built.
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** Emacs crashes when using some version of the Exceed X server.
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Upgrading to a newer version of Exceed has been reported to prevent
these crashes.  You should consider switching to a free X server, such
as Xming or Cygwin/X.
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** Emacs crashes with SIGSEGV in XtInitializeWidgetClass.
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It crashes on X, but runs fine when called with option "-nw".
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This has been observed when Emacs is linked with GNU ld but without passing
the -z nocombreloc flag.  Emacs normally knows to pass the -z nocombreloc
flag when needed, so if you come across a situation where the flag is
necessary but missing, please report it via M-x report-emacs-bug.
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On platforms such as Solaris, you can also work around this problem by
configuring your compiler to use the native linker instead of GNU ld.
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** When Emacs is compiled with Gtk+, closing a display kills Emacs.
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There is a long-standing bug in GTK that prevents it from recovering
from disconnects: http://bugzilla.gnome.org/show_bug.cgi?id=85715.
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Thus, for instance, when Emacs is run as a server on a text terminal,
and an X frame is created, and the X server for that frame crashes or
exits unexpectedly, Emacs must exit to prevent a GTK error that would
result in an endless loop.
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If you need Emacs to be able to recover from closing displays, compile
it with the Lucid toolkit instead of GTK.
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* General runtime problems
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** Lisp problems
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*** Changes made to .el files do not take effect.
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You may have forgotten to recompile them into .elc files.
Then the old .elc files will be loaded, and your changes
will not be seen.  To fix this, do M-x byte-recompile-directory
and specify the directory that contains the Lisp files.
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Emacs should print a warning when loading a .elc file which is older
than the corresponding .el file.
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*** Watch out for .emacs files and EMACSLOADPATH environment vars.
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These control the actions of Emacs.
~/.emacs is your Emacs init file.
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EMACSLOADPATH overrides which directories the function "load" will search.
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If you observe strange problems, check for these and get rid
of them, then try again.
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*** Using epop3.el package causes Emacs to signal an error.
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The error message might be something like this:
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  "Lisp nesting exceeds max-lisp-eval-depth"
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This happens because epop3 redefines the function gethash, which is a
built-in primitive beginning with Emacs 21.1.  We don't have a patch
for epop3 that fixes this, but perhaps a newer version of epop3
corrects that.
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*** Buffers from `with-output-to-temp-buffer' get set up in Help mode.
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Changes in Emacs 20.4 to the hooks used by that function cause
problems for some packages, specifically BBDB.  See the function's
documentation for the hooks involved.  BBDB 2.00.06 fixes the problem.
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*** The Hyperbole package causes *Help* buffers not to be displayed in
Help mode due to setting `temp-buffer-show-hook' rather than using
`add-hook'.  Using `(add-hook 'temp-buffer-show-hook
'help-mode-maybe)' after loading Hyperbole should fix this.
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** Keyboard problems
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*** Unable to enter the M-| key on some German keyboards.
Some users have reported that M-| suffers from "keyboard ghosting".
This can't be fixed by Emacs, as the keypress never gets passed to it
at all (as can be verified using "xev").  You can work around this by
typing `ESC |' instead.

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*** "Compose Character" key does strange things when used as a Meta key.
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If you define one key to serve as both Meta and Compose Character, you
will get strange results.  In previous Emacs versions, this "worked"
in that the key acted as Meta--that's because the older Emacs versions
did not try to support Compose Character.  Now Emacs tries to do
character composition in the standard X way.  This means that you
must pick one meaning or the other for any given key.
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You can use both functions (Meta, and Compose Character) if you assign
them to two different keys.
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*** C-z just refreshes the screen instead of suspending Emacs.
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You are probably using a shell that doesn't support job control, even
though the system itself is capable of it.  Either use a different shell,
or set the variable `cannot-suspend' to a non-nil value.
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*** With M-x enable-flow-control, you need to type C-\ twice
to do incremental search--a single C-\ gets no response.
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This has been traced to communicating with your machine via kermit,
with C-\ as the kermit escape character.  One solution is to use
another escape character in kermit.  One user did
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   set escape-character 17
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in his .kermrc file, to make C-q the kermit escape character.
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** Mailers and other helper programs
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*** movemail compiled with POP support can't connect to the POP server.
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Make sure that the `pop' entry in /etc/services, or in the services
NIS map if your machine uses NIS, has the same port number as the
entry on the POP server.  A common error is for the POP server to be
listening on port 110, the assigned port for the POP3 protocol, while
the client is trying to connect on port 109, the assigned port for the
old POP protocol.
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*** RMAIL gets error getting new mail.
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RMAIL gets new mail from /usr/spool/mail/$USER using a program
called `movemail'.  This program interlocks with /bin/mail using
the protocol defined by /bin/mail.
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There are two different protocols in general use.  One of them uses
the `flock' system call.  The other involves creating a lock file;
`movemail' must be able to write in /usr/spool/mail in order to do
this.  You control which one is used by defining, or not defining,
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the macro MAIL_USE_FLOCK in config.h or the m/ or s/ file it includes.
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IF YOU DON'T USE THE FORM OF INTERLOCKING THAT IS NORMAL ON YOUR
SYSTEM, YOU CAN LOSE MAIL!
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If your system uses the lock file protocol, and fascist restrictions
prevent ordinary users from writing the lock files in /usr/spool/mail,
you may need to make `movemail' setgid to a suitable group such as
`mail'.  To do this,  use the following commands (as root) after doing the
make install.
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        chgrp mail movemail
        chmod 2755 movemail
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Installation normally copies movemail from the build directory to an
installation directory which is usually under /usr/local/lib.  The
installed copy of movemail is usually in the directory
/usr/local/lib/emacs/VERSION/TARGET.  You must change the group and
mode of the installed copy; changing the group and mode of the build
directory copy is ineffective.
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*** rcs2log gives you the awk error message "too many fields".
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This is due to an arbitrary limit in certain versions of awk.
The solution is to use gawk (GNU awk).
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** Problems with hostname resolution
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*** Emacs fails to understand most Internet host names, even though
the names work properly with other programs on the same system.
*** Emacs won't work with X-windows if the value of DISPLAY is HOSTNAME:0.
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*** Gnus can't make contact with the specified host for nntp.
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This typically happens on Suns and other systems that use shared
libraries.  The cause is that the site has installed a version of the
shared library which uses a name server--but has not installed a
similar version of the unshared library which Emacs uses.
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The result is that most programs, using the shared library, work with
the nameserver, but Emacs does not.
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The fix is to install an unshared library that corresponds to what you
installed in the shared library, and then relink Emacs.
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If you have already installed the name resolver in the file libresolv.a,
then you need to compile Emacs to use that library.  The easiest way to
do this is to add to config.h a definition of LIBS_SYSTEM, LIBS_MACHINE
or LIB_STANDARD which uses -lresolv.  Watch out!  If you redefine a macro
that is already in use in your configuration to supply some other libraries,
be careful not to lose the others.
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Thus, you could start by adding this to config.h:
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#define LIBS_SYSTEM -lresolv
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Then if this gives you an error for redefining a macro, and you see that
the s- file defines LIBS_SYSTEM as -lfoo -lbar, you could change config.h
again to say this:
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#define LIBS_SYSTEM -lresolv -lfoo -lbar
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*** Emacs does not know your host's fully-qualified domain name.
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For example, (system-name) returns some variation on
"localhost.localdomain", rather the name you were expecting.

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You need to configure your machine with a fully qualified domain name,
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(i.e. a name with at least one ".") either in /etc/hosts,
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/etc/hostname, the NIS, or wherever your system calls for specifying this.
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If you cannot fix the configuration, you can set the Lisp variable
mail-host-address to the value you want.
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** NFS and RFS
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*** Emacs says it has saved a file, but the file does not actually
appear on disk.
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This can happen on certain systems when you are using NFS, if the
remote disk is full.  It is due to a bug in NFS (or certain NFS
implementations), and there is apparently nothing Emacs can do to
detect the problem.  Emacs checks the failure codes of all the system
calls involved in writing a file, including `close'; but in the case
where the problem occurs, none of those system calls fails.
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*** Editing files through RFS gives spurious "file has changed" warnings.
It is possible that a change in Emacs 18.37 gets around this problem,
but in case not, here is a description of how to fix the RFS bug that
causes it.
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    There was a serious pair of bugs in the handling of the fsync() system
    call in the RFS server.
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    The first is that the fsync() call is handled as another name for the
    close() system call (!!).  It appears that fsync() is not used by very
    many programs; Emacs version 18 does an fsync() before closing files
    to make sure that the bits are on the disk.
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    This is fixed by the enclosed patch to the RFS server.
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    The second, more serious problem, is that fsync() is treated as a
    non-blocking system call (i.e., it's implemented as a message that
    gets sent to the remote system without waiting for a reply).  Fsync is
    a useful tool for building atomic file transactions.  Implementing it
    as a non-blocking RPC call (when the local call blocks until the sync
    is done) is a bad idea; unfortunately, changing it will break the RFS
    protocol.  No fix was supplied for this problem.
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    (as always, your line numbers may vary)
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    % rcsdiff -c -r1.2 serversyscall.c
    RCS file: RCS/serversyscall.c,v
    retrieving revision 1.2
    diff -c -r1.2 serversyscall.c
    *** /tmp/,RCSt1003677   Wed Jan 28 15:15:02 1987
    --- serversyscall.c     Wed Jan 28 15:14:48 1987
    ***************
    *** 163,169 ****
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            /*
             * No return sent for close or fsync!
             */
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    !       if (syscall == RSYS_close || syscall == RSYS_fsync)
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                    proc->p_returnval = deallocate_fd(proc, msg->m_args[0]);
            else
            {
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    --- 166,172 ----
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            /*
             * No return sent for close or fsync!
             */
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    !       if (syscall == RSYS_close)
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                    proc->p_returnval = deallocate_fd(proc, msg->m_args[0]);
            else
            {
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** PSGML conflicts with sgml-mode.
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PSGML package uses the same names of some variables (like keymap)
as built-in sgml-mode.el because it was created as a replacement
of that package.  The conflict will be shown if you load
sgml-mode.el before psgml.el.  E.g. this could happen if you edit
HTML page and then start to work with SGML or XML file.  html-mode
(from sgml-mode.el) is used for HTML file and loading of psgml.el
(for sgml-mode or xml-mode) will cause an error.
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** PCL-CVS

*** Lines are not updated or new lines are added in the buffer upon commit.

When committing files located higher in the hierarchy than the examined
directory, some versions of the CVS program return an ambiguous message
from which PCL-CVS cannot extract the full location of the committed
files.  As a result, the corresponding lines in the PCL-CVS buffer are
not updated with the new revision of these files, and new lines are
added to the top-level directory.

This can happen with CVS versions 1.12.8 and 1.12.9.  Upgrade to CVS
1.12.10 or newer to fix this problem.

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** Miscellaneous problems
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*** Editing files with very long lines is slow.

For example, simply moving through a file that contains hundreds of
thousands of characters per line is slow, and consumes a lot of CPU.
This is a known limitation of Emacs with no solution at this time.

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*** Emacs uses 100% of CPU time

This is a known problem with some versions of the Semantic package.
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The solution is to upgrade Semantic to version 2.0pre4 (distributed
with CEDET 1.0pre4) or later.
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*** Self-documentation messages are garbled.
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This means that the file `etc/DOC-...' doesn't properly correspond
with the Emacs executable.  Redumping Emacs and then installing the
corresponding pair of files should fix the problem.
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*** Programs running under terminal emulator do not recognize `emacs'
terminal type.
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The cause of this is a shell startup file that sets the TERMCAP
environment variable.  The terminal emulator uses that variable to
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provide the information on the special terminal type that Emacs emulates.
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Rewrite your shell startup file so that it does not change TERMCAP
in such a case.  You could use the following conditional which sets
it only if it is undefined.
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    if ( ! ${?TERMCAP} ) setenv TERMCAP ~/my-termcap-file
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Or you could set TERMCAP only when you set TERM--which should not
happen in a non-login shell.
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*** In Shell mode, you get a ^M at the end of every line.
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This happens to people who use tcsh, because it is trying to be too
smart.  It sees that the Shell uses terminal type `unknown' and turns
on the flag to output ^M at the end of each line.  You can fix the
problem by adding this to your .cshrc file:
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    if ($?EMACS) then
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        if ("$EMACS" =~ /*) then
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            unset edit
            stty  -icrnl -onlcr -echo susp ^Z
        endif
    endif
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*** Emacs startup on GNU/Linux systems (and possibly other systems) is slow.
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This can happen if the system is misconfigured and Emacs can't get the
full qualified domain name, FQDN.  You should have your FQDN in the
/etc/hosts file, something like this:
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127.0.0.1	localhost
129.187.137.82	nuc04.t30.physik.tu-muenchen.de	nuc04
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The way to set this up may vary on non-GNU systems.
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*** Attempting to visit remote files via ange-ftp fails.
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If the error message is "ange-ftp-file-modtime: Specified time is not
representable", then this could happen when `lukemftp' is used as the
ftp client.  This was reported to happen on Debian GNU/Linux, kernel
version 2.4.3, with `lukemftp' 1.5-5, but might happen on other
systems as well.  To avoid this problem, switch to using the standard
ftp client.  On a Debian system, type
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  update-alternatives --config ftp
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and then choose /usr/bin/netkit-ftp.
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*** JPEG images aren't displayed.
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This has been reported when Emacs is built with jpeg-6a library.
Upgrading to jpeg-6b solves the problem.  Configure checks for the
correct version, but this problem could occur if a binary built
against a shared libjpeg is run on a system with an older version.
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*** Dired is very slow.
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This could happen if invocation of the `df' program takes a long
time.  Possible reasons for this include:

  - ClearCase mounted filesystems (VOBs) that sometimes make `df'
    response time extremely slow (dozens of seconds);

  - slow automounters on some old versions of Unix;

  - slow operation of some versions of `df'.

To work around the problem, you could either (a) set the variable
`directory-free-space-program' to nil, and thus prevent Emacs from
invoking `df'; (b) use `df' from the GNU Fileutils package; or
(c) use CVS, which is Free Software, instead of ClearCase.

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*** ps-print commands fail to find prologue files ps-prin*.ps.
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This can happen if you use an old version of X-Symbol package: it
defines compatibility functions which trick ps-print into thinking it
runs in XEmacs, and look for the prologue files in a wrong directory.

The solution is to upgrade X-Symbol to a later version.

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*** On systems with shared libraries you might encounter run-time errors
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from the dynamic linker telling you that it is unable to find some
shared libraries, for instance those for Xaw3d or image support.
These errors mean Emacs has been linked with a library whose shared
library is not in the default search path of the dynamic linker.

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Similar problems could prevent Emacs from building, since the build
process invokes Emacs several times.

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On many systems, it is possible to set LD_LIBRARY_PATH in your
environment to specify additional directories where shared libraries
can be found.

Other systems allow to set LD_RUN_PATH in a similar way, but before
Emacs is linked.  With LD_RUN_PATH set, the linker will include a
specified run-time search path in the executable.

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On some systems, Emacs can crash due to problems with dynamic
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linking.  Specifically, on SGI Irix 6.5, crashes were reported with
backtraces like this:

  (dbx) where
   0 strcmp(0xf49239d, 0x4031184, 0x40302b4, 0x12, 0xf0000000, 0xf4923aa, 0x0, 0x492ddb2) ["/xlv22/ficus-jan23/work/irix/lib/libc/libc_n32_M3_ns/strings/strcmp.s":35, 0xfb7e480]
   1 general_find_symbol(0xf49239d, 0x0, 0x0, 0x0, 0xf0000000, 0xf4923aa, 0x0, 0x492ddb2)
 ["/comp2/mtibuild/v73/workarea/v7.3/rld/rld.c":2140, 0xfb65a98]
   2 resolve_symbol(0xf49239d, 0x4031184, 0x0, 0xfbdd438, 0x0, 0xf4923aa, 0x0, 0x492ddb2)
 ["/comp2/mtibuild/v73/workarea/v7.3/rld/rld.c":1947, 0xfb657e4]
   3 lazy_text_resolve(0xd18, 0x1a3, 0x40302b4, 0x12, 0xf0000000, 0xf4923aa, 0x0, 0x492ddb2)
 ["/comp2/mtibuild/v73/workarea/v7.3/rld/rld.c":997, 0xfb64d44]
   4 _rld_text_resolve(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0)
 ["/comp2/mtibuild/v73/workarea/v7.3/rld/rld_bridge.s":175, 0xfb6032c]

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(`rld' is the dynamic linker.)  We don't know yet why this
happens, but setting the environment variable LD_BIND_NOW to 1 (which
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forces the dynamic linker to bind all shared objects early on) seems
to work around the problem.

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Please refer to the documentation of your dynamic linker for details.

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*** You request inverse video, and the first Emacs frame is in inverse
video, but later frames are not in inverse video.
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This can happen if you have an old version of the custom library in
your search path for Lisp packages.  Use M-x list-load-path-shadows to
check whether this is true.  If it is, delete the old custom library.
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*** When you run Ispell from Emacs, it reports a "misalignment" error.
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This can happen if you compiled the Ispell program to use ASCII
characters only and then try to use it from Emacs with non-ASCII
characters, like Latin-1.  The solution is to recompile Ispell with
support for 8-bit characters.
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To see whether your Ispell program supports 8-bit characters, type
this at your shell's prompt:
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     ispell -vv
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and look in the output for the string "NO8BIT".  If Ispell says
"!NO8BIT (8BIT)", your speller supports 8-bit characters; otherwise it
does not.
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To rebuild Ispell with 8-bit character support, edit the local.h file
in the Ispell distribution and make sure it does _not_ define NO8BIT.
Then rebuild the speller.
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Another possible cause for "misalignment" error messages is that the
version of Ispell installed on your machine is old.  Upgrade.
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Yet another possibility is that you are trying to spell-check a word
in a language that doesn't fit the dictionary you choose for use by
Ispell.  (Ispell can only spell-check one language at a time, because
it uses a single dictionary.)  Make sure that the text you are
spelling and the dictionary used by Ispell conform to each other.
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If your spell-checking program is Aspell, it has been reported that if
you have a personal configuration file (normally ~/.aspell.conf), it
can cause this error.  Remove that file, execute `ispell-kill-ispell'
in Emacs, and then try spell-checking again.
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* Runtime problems related to font handling
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** Characters are displayed as empty boxes or with wrong font under X.

*** This can occur when two different versions of FontConfig are used.
For example, XFree86 4.3.0 has one version and Gnome usually comes
with a newer version.  Emacs compiled with Gtk+ will then use the
newer version.  In most cases the problem can be temporarily fixed by
stopping the application that has the error (it can be Emacs or any
other application), removing ~/.fonts.cache-1, and then start the
application again.  If removing ~/.fonts.cache-1 and restarting
doesn't help, the application with problem must be recompiled with the
same version of FontConfig as the rest of the system uses.  For KDE,
it is sufficient to recompile Qt.

*** Some fonts have a missing glyph and no default character.  This is
known to occur for character number 160 (no-break space) in some
fonts, such as Lucida but Emacs sets the display table for the unibyte
and Latin-1 version of this character to display a space.

*** Some of the fonts called for in your fontset may not exist on your
X server.
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Each X11 font covers just a fraction of the characters that Emacs
supports.  To display the whole range of Emacs characters requires
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many different fonts, collected into a fontset.  You can remedy the
problem by installing additional fonts.
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The intlfonts distribution includes a full spectrum of fonts that can
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display all the characters Emacs supports.  The etl-unicode collection
of fonts (available from <URL:ftp://ftp.x.org/contrib/fonts/> and
<URL:ftp://ftp.xfree86.org/pub/mirror/X.Org/contrib/fonts/>) includes
fonts that can display many Unicode characters; they can also be used
by ps-print and ps-mule to print Unicode characters.
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** Under X11, some characters appear improperly aligned in their lines.
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You may have bad X11 fonts; try installing the intlfonts distribution
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or the etl-unicode collection (see above).

** Under X, an unexpected monospace font is used as the default font.

When compiled with XFT, Emacs tries to use a default font named
"monospace".  This is a "virtual font", which the operating system
(Fontconfig) redirects to a suitable font such as DejaVu Sans Mono.
On some systems, there exists a font that is actually named Monospace,
which takes over the virtual font.  This is considered an operating
system bug; see
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http://lists.gnu.org/archive/html/emacs-devel/2008-10/msg00696.html
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If you encounter this problem, set the default font to a specific font
in your .Xresources or initialization file.  For instance, you can put
the following in your .Xresources:

Emacs.font: DejaVu Sans Mono 12

** Certain fonts make each line take one pixel more than it should.

This is because these fonts contain characters a little taller than
the font's nominal height.  Emacs needs to make sure that lines do not
overlap.
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** Loading fonts is very slow.
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You might be getting scalable fonts instead of precomputed bitmaps.
Known scalable font directories are "Type1" and "Speedo".  A font
directory contains scalable fonts if it contains the file
"fonts.scale".
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If this is so, re-order your X windows font path to put the scalable
font directories last.  See the documentation of `xset' for details.
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With some X servers, it may be necessary to take the scalable font
directories out of your path entirely, at least for Emacs 19.26.
Changes in the future may make this unnecessary.
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** Font Lock displays portions of the buffer in incorrect faces.
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By far the most frequent cause of this is a parenthesis `(' or a brace
`{' in column zero.  Font Lock assumes that such a paren is outside of
any comment or string.  This is of course not true in general, but the
vast majority of well-formatted program source files don't have such
parens, and therefore this assumption is used to allow optimizations
in Font Lock's syntactical analysis.  These optimizations avoid some
pathological cases where jit-lock, the Just-in-Time fontification
introduced with Emacs 21.1, could significantly slow down scrolling
through the buffer, especially scrolling backwards, and also jumping
to the end of a very large buffer.
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Beginning with version 22.1, a parenthesis or a brace in column zero
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is highlighted in bold-red face if it is inside a string or a comment,
to indicate that it could interfere with Font Lock (and also with
indentation) and should be moved or escaped with a backslash.
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If you don't use large buffers, or have a very fast machine which
makes the delays insignificant, you can avoid the incorrect
fontification by setting the variable
`font-lock-beginning-of-syntax-function' to a nil value.  (This must
be done _after_ turning on Font Lock.)
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Another alternative is to avoid a paren in column zero.  For example,
in a Lisp string you could precede the paren with a backslash.
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** With certain fonts, when the cursor appears on a character, the
character doesn't appear--you get a solid box instead.
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One user on a Linux-based GNU system reported that this problem went
away with installation of a new X server.  The failing server was
XFree86 3.1.1.  XFree86 3.1.2 works.
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** Emacs pauses for several seconds when changing the default font.
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This has been reported for fvwm 2.2.5 and the window manager of KDE
2.1.  The reason for the pause is Xt waiting for a ConfigureNotify
event from the window manager, which the window manager doesn't send.
Xt stops waiting after a default timeout of usually 5 seconds.
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A workaround for this is to add something like
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emacs.waitForWM: false
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to your X resources.  Alternatively, add `(wait-for-wm . nil)' to a
frame's parameter list, like this:
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   (modify-frame-parameters nil '((wait-for-wm . nil)))
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(this should go into your `.emacs' file).
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** Underlines appear at the wrong position.
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This is caused by fonts having a wrong UNDERLINE_POSITION property.
Examples are the font 7x13 on XFree prior to version 4.1, or the jmk
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neep font from the Debian xfonts-jmk package prior to version 3.0.17.
To circumvent this problem, set x-use-underline-position-properties
to nil in your `.emacs'.
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To see what is the value of UNDERLINE_POSITION defined by the font,
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type `xlsfonts -lll FONT' and look at the font's UNDERLINE_POSITION property.
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** When using Exceed, fonts sometimes appear too tall.
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When the display is set to an Exceed X-server and fonts are specified
(either explicitly with the -fn option or implicitly with X resources)
then the fonts may appear "too tall".  The actual character sizes are
correct but there is too much vertical spacing between rows,  which
gives the appearance of "double spacing".
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To prevent this, turn off the Exceed's "automatic font substitution"
feature (in the font part of the configuration window).
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** Subscript/superscript text in TeX is hard to read.

If `tex-fontify-script' is non-nil, tex-mode displays
subscript/superscript text in the faces subscript/superscript, which
are smaller than the normal font and lowered/raised.  With some fonts,
nested superscripts (say) can be hard to read.  Switching to a
different font, or changing your antialiasing setting (on an LCD
screen), can both make the problem disappear.  Alternatively, customize
the following variables: tex-font-script-display (how much to
lower/raise); tex-suscript-height-ratio (how much smaller than
normal); tex-suscript-height-minimum (minimum height).

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* Internationalization problems
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** M-{ does not work on a Spanish PC keyboard.

Many Spanish keyboards seem to ignore that combination.  Emacs can't
do anything about it.

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** International characters aren't displayed under X.

*** Missing X fonts
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