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    1 Known Problems with GNU Emacs
    2 
    3 Copyright (C) 1987-1989, 1993-1999, 2001-2021 Free Software Foundation,
    4 Inc.
    5 See the end of the file for license conditions.
    6 
    7 
    8 This file describes various problems that have been encountered
    9 in compiling, installing and running GNU Emacs.  Try doing C-c C-t
   10 and browsing through the outline headers.  (See C-h m for help on
   11 Outline mode.)  Information about systems that are no longer supported,
   12 and old Emacs releases, has been removed.  Consult older versions of
   13 this file if you are interested in that information.
   14 
   15 * Mule-UCS doesn't work in Emacs 23 onwards
   16 
   17 It's completely redundant now, as far as we know.
   18 
   19 * Emacs startup failures
   20 
   21 ** Emacs fails to start, complaining about missing fonts.
   22 
   23 A typical error message might be something like
   24 
   25   No fonts match ‘-*-fixed-medium-r-*--6-*-*-*-*-*-iso8859-1’
   26 
   27 This happens because some X resource specifies a bad font family for
   28 Emacs to use.  The possible places where this specification might be are:
   29 
   30   - in the X server resources database, often initialized from
   31     ~/.Xresources (use $ xrdb -query to find out the current state)
   32 
   33   - in your ~/.Xdefaults file
   34 
   35   - client-side X resource file, such as  ~/Emacs or
   36     /usr/share/X11/app-defaults/Emacs
   37 
   38 One of these files might have bad or malformed specification of a
   39 fontset that Emacs should use.  To fix the problem, you need to find
   40 the problematic line(s) and correct them.
   41 
   42 After correcting ~/.Xresources, the new data has to be merged into the
   43 X server resources database.  Depending on the circumstances, the
   44 following command may do the trick.  See xrdb(1) for more information.
   45 
   46   $ xrdb -merge ~/.Xresources
   47 
   48 ** Emacs compiled with Cairo crashes when restoring session from desktop file.
   49 
   50 This can happen if the '.emacs.desktop' file contains setting for
   51 'font-backend' frame parameter.  A workaround is to delete the
   52 offending '.emacs.desktop' file, or edit it to remove the setting of
   53 'font-backend'.
   54 
   55 ** Emacs aborts while starting up, only when run without X.
   56 
   57 This problem often results from compiling Emacs with GCC when GCC was
   58 installed incorrectly.  The usual error in installing GCC is to
   59 specify --includedir=/usr/include.  Installation of GCC makes
   60 corrected copies of the system header files.  GCC is supposed to use
   61 the corrected copies in preference to the original system headers.
   62 Specifying --includedir=/usr/include causes the original system header
   63 files to be used.  On some systems, the definition of ioctl in the
   64 original system header files is invalid for ANSI C and causes Emacs
   65 not to work.
   66 
   67 The fix is to reinstall GCC, and this time do not specify --includedir
   68 when you configure it.  Then recompile Emacs.  Specifying --includedir
   69 is appropriate only in very special cases and it should *never* be the
   70 same directory where system header files are kept.
   71 
   72 ** Emacs does not start, complaining that it cannot open termcap database file.
   73 
   74 If your system uses Terminfo rather than termcap (most modern
   75 systems do), this could happen if the proper version of
   76 ncurses is not visible to the Emacs configure script (i.e. it
   77 cannot be found along the usual path the linker looks for
   78 libraries).  It can happen because your version of ncurses is
   79 obsolete, or is available only in form of binaries.
   80 
   81 The solution is to install an up-to-date version of ncurses in
   82 the developer's form (header files, static libraries and
   83 symbolic links); in some GNU/Linux distributions (e.g. Debian)
   84 it constitutes a separate package.
   85 
   86 ** Emacs 20 and later fails to load Lisp files at startup.
   87 
   88 The typical error message might be like this:
   89 
   90   "Cannot open load file: fontset"
   91 
   92 This could happen if you compress the file lisp/subdirs.el.  That file
   93 tells Emacs what are the directories where it should look for Lisp
   94 files.  Emacs cannot work with subdirs.el compressed, since the
   95 Auto-compress mode it needs for this will not be loaded until later,
   96 when your .emacs file is processed.  (The package 'fontset.el' is
   97 required to set up fonts used to display text on window systems, and
   98 it's loaded very early in the startup procedure.)
   99 
  100 Similarly, any other .el file for which there's no corresponding .elc
  101 file could fail to load if it is compressed.
  102 
  103 The solution is to uncompress all .el files that don't have a .elc file.
  104 
  105 Another possible reason for such failures is stale *.elc files
  106 lurking somewhere on your load-path -- see the next section.
  107 
  108 ** Emacs prints an error at startup after upgrading from an earlier version.
  109 
  110 An example of such an error is:
  111 
  112   x-complement-fontset-spec: "Wrong type argument: stringp, nil"
  113 
  114 This can be another symptom of stale *.elc files in your load-path.
  115 The following command will print any duplicate Lisp files that are
  116 present in load-path:
  117 
  118     emacs -batch -f list-load-path-shadows
  119 
  120 If this command prints any file names, some of these files are stale,
  121 and should be deleted or their directories removed from your
  122 load-path.
  123 
  124 * Crash bugs
  125 
  126 ** Emacs crashes when running in a terminal, if compiled with GCC 4.5.0
  127 
  128 This version of GCC is buggy: see
  129 
  130   https://debbugs.gnu.org/6031
  131   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43904
  132 
  133 You can work around this error in gcc-4.5 by omitting sibling call
  134 optimization.  To do this, configure Emacs with
  135 
  136  ./configure CFLAGS="-g -O2 -fno-optimize-sibling-calls"
  137 
  138 ** Emacs compiled with GCC 4.6.1 crashes on MS-Windows when C-g is pressed
  139 
  140 This is known to happen when Emacs is compiled with MinGW GCC 4.6.1
  141 with the -O2 option (which is the default in the Windows build).  The
  142 reason is a bug in MinGW GCC 4.6.1; to work around, either add the
  143 '-fno-omit-frame-pointer' switch to GCC or compile without
  144 optimizations ('--no-opt' switch to the configure.bat script).
  145 
  146 ** Emacs crashes in x-popup-dialog.
  147 
  148 This can happen if the dialog widget cannot find the font it wants to
  149 use.  You can work around the problem by specifying another font with
  150 an X resource--for example, 'Emacs.dialog*.font: 9x15' (or any font that
  151 happens to exist on your X server).
  152 
  153 ** Emacs crashes when you use Bibtex mode.
  154 
  155 This happens if your system puts a small limit on stack size.  You can
  156 prevent the problem by using a suitable shell command (often 'ulimit')
  157 to raise the stack size limit before you run Emacs.
  158 
  159 Patches to raise the stack size limit automatically in 'main'
  160 (src/emacs.c) on various systems would be greatly appreciated.
  161 
  162 ** Error message 'Symbol’s value as variable is void: x', followed by
  163 a segmentation fault and core dump.
  164 
  165 This has been tracked to a bug in tar!  People report that tar erroneously
  166 added a line like this at the beginning of files of Lisp code:
  167 
  168    x FILENAME, N bytes, B tape blocks
  169 
  170 If your tar has this problem, install GNU tar--if you can manage to
  171 untar it :-).
  172 
  173 ** Emacs can crash when displaying PNG images with transparency.
  174 
  175 This is due to a bug introduced in ImageMagick 6.8.2-3.  The bug should
  176 be fixed in ImageMagick 6.8.3-10.  See <URL:https://debbugs.gnu.org/13867>.
  177 
  178 ** Crashes when displaying GIF images in Emacs built with version
  179 libungif-4.1.0 are resolved by using version libungif-4.1.0b1.
  180 Configure checks for the correct version, but this problem could occur
  181 if a binary built against a shared libungif is run on a system with an
  182 older version.
  183 
  184 ** Emacs aborts inside the function 'tparam1'.
  185 
  186 This can happen if Emacs was built without terminfo support, but the
  187 terminal's capabilities use format that is only supported by terminfo.
  188 If your system has ncurses installed, this might happen if your
  189 version of ncurses is broken; upgrading to a newer version of ncurses
  190 and reconfiguring and rebuilding Emacs should solve this.
  191 
  192 All modern systems support terminfo, so even if ncurses is not the
  193 problem, you should look for a way to configure Emacs so that it uses
  194 terminfo when built.
  195 
  196 ** Emacs crashes when using some version of the Exceed X server.
  197 
  198 Upgrading to a newer version of Exceed has been reported to prevent
  199 these crashes.  You should consider switching to a free X server, such
  200 as Xming or Cygwin/X.
  201 
  202 ** Emacs crashes with SIGSEGV in XtInitializeWidgetClass.
  203 
  204 It crashes on X, but runs fine when called with option "-nw".
  205 
  206 This has been observed when Emacs is linked with GNU ld but without passing
  207 the -z nocombreloc flag.  Emacs normally knows to pass the -z nocombreloc
  208 flag when needed, so if you come across a situation where the flag is
  209 necessary but missing, please report it via M-x report-emacs-bug.
  210 
  211 On platforms such as Solaris, you can also work around this problem by
  212 configuring your compiler to use the native linker instead of GNU ld.
  213 
  214 ** When Emacs is compiled with Gtk+, closing a display kills Emacs.
  215 
  216 There is a long-standing bug in GTK that prevents it from recovering
  217 from disconnects: https://gitlab.gnome.org/GNOME/gtk/issues/221
  218 
  219 Thus, for instance, when Emacs is run as a server on a text terminal,
  220 and an X frame is created, and the X server for that frame crashes or
  221 exits unexpectedly, Emacs must exit to prevent a GTK error that would
  222 result in an endless loop.
  223 
  224 If you need Emacs to be able to recover from closing displays, compile
  225 it with the Lucid toolkit instead of GTK.
  226 
  227 ** Emacs compiled with GTK+ 3 crashes when run under some X servers.
  228 This happens when the X server does not provide certain display
  229 features that the underlying GTK+ 3 toolkit assumes.  For example, this
  230 issue has been seen with remote X servers like X2Go.  The symptoms
  231 are an Emacs crash, possibly triggered by the mouse entering the Emacs
  232 window, or an attempt to resize the Emacs window.  The crash backtrace
  233 contains a call to XQueryPointer.
  234 
  235 This issue was fixed in the GTK+ 3 toolkit in commit 4b1c0256 in February 2018.
  236 
  237 If your GTK+ 3 is still affected, you can avoid the issue by recompiling
  238 Emacs with a different X toolkit, eg --with-toolkit=gtk2.
  239 
  240 References:
  241 https://gitlab.gnome.org/GNOME/gtk/commit/4b1c02560f0d8097bf5a11932e52fb72f3e9e94b
  242 https://debbugs.gnu.org/24280
  243 https://bugs.debian.org/901038
  244 https://bugzilla.redhat.com/1483942
  245 https://access.redhat.com/solutions/3410101
  246 
  247 ** Emacs compiled with GTK crashes at startup due to X protocol error.
  248 
  249 This is known to happen on elementary OS GNU/Linux systems.
  250 
  251 The error message is:
  252 
  253   X protocol error: BadMatch (invalid parameter attributes) on protocol request 140
  254   When compiled with GTK, Emacs cannot recover from X disconnects.
  255   This is a GTK bug: https://gitlab.gnome.org/GNOME/gtk/issues/221
  256   For details, see etc/PROBLEMS.
  257   Fatal error 6: Aborted
  258 
  259 followed by a C backtrace.  (Sometimes the offending protocol request
  260 number is 139.)
  261 
  262 The relevant bug report is here:
  263 
  264   https://bugs.launchpad.net/elementaryos/+bug/1355274
  265 
  266 A workaround is to set XLIB_SKIP_ARGB_VISUALS=1 in the environment
  267 before starting Emacs, or run Emacs as root.
  268 
  269 ** Emacs crashes when you try to view a file with complex characters.
  270 
  271 One possible reason for this could be a bug in the libotf or the
  272 libm17n-flt/m17n-db libraries Emacs uses for displaying complex
  273 scripts.  Make sure you have the latest versions of these libraries
  274 installed.  If the problem still persists with the latest released
  275 versions of these libraries, you can try building these libraries from
  276 their CVS repository:
  277 
  278   cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/m17n co libotf
  279   cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/m17n co m17n-db
  280   cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/m17n co m17n-lib
  281 
  282 One known problem that causes such crashes is with using Noto Serif
  283 Kannada fonts.  To work around that, force Emacs not to select these
  284 fonts, by adding the following to your ~/.emacs init file:
  285 
  286   (push "Noto Serif Kannada" face-ignored-fonts)
  287 
  288 You can try this interactively in a running Emacs session like this:
  289 
  290   M-: (push "Noto Serif Kannada" face-ignored-fonts) RET
  291 
  292 Another set of problems is caused by an incompatible libotf library.
  293 In this case, displaying the etc/HELLO file (as shown by C-h h)
  294 triggers the following message to be shown in the terminal from which
  295 you launched Emacs:
  296 
  297   symbol lookup error: /usr/bin/emacs: undefined symbol: OTF_open
  298 
  299 This problem occurs because unfortunately there are two libraries
  300 called "libotf".  One is the library for handling OpenType fonts,
  301 https://www.nongnu.org/m17n/, which is the one that Emacs expects.
  302 The other is a library for Open Trace Format, and is used by some
  303 versions of the MPI message passing interface for parallel
  304 programming.
  305 
  306 For example, on RHEL6 GNU/Linux, the OpenMPI rpm provides a version
  307 of "libotf.so" in /usr/lib/openmpi/lib.  This directory is not
  308 normally in the ld search path, but if you want to use OpenMPI,
  309 you must issue the command "module load openmpi".  This adds
  310 /usr/lib/openmpi/lib to LD_LIBRARY_PATH.  If you then start Emacs from
  311 the same shell, you will encounter this crash.
  312 Ref: <URL:https://bugzilla.redhat.com/show_bug.cgi?id=844776>
  313 
  314 There is no good solution to this problem if you need to use both
  315 OpenMPI and Emacs with libotf support.  The best you can do is use a
  316 wrapper shell script (or function) "emacs" that removes the offending
  317 element from LD_LIBRARY_PATH before starting emacs proper.
  318 Or you could recompile Emacs with an -Wl,-rpath option that
  319 gives the location of the correct libotf.
  320 
  321 * General runtime problems
  322 
  323 ** Lisp problems
  324 
  325 *** Changes made to .el files do not take effect.
  326 
  327 You may have forgotten to recompile them into .elc files.
  328 Then the old .elc files will be loaded, and your changes
  329 will not be seen.  To fix this, do M-x byte-recompile-directory
  330 and specify the directory that contains the Lisp files.
  331 
  332 Emacs prints a warning when loading a .elc file which is older
  333 than the corresponding .el file.
  334 
  335 Alternatively, if you set the option 'load-prefer-newer' non-nil,
  336 Emacs will load whichever version of a file is the newest.
  337 
  338 *** Watch out for the EMACSLOADPATH environment variable
  339 
  340 EMACSLOADPATH overrides which directories the function "load" will search.
  341 
  342 If you observe strange problems, check for this variable in your
  343 environment.
  344 
  345 *** Using epop3.el package causes Emacs to signal an error.
  346 
  347 The error message might be something like this:
  348 
  349   "Lisp nesting exceeds max-lisp-eval-depth"
  350 
  351 This happens because epop3 redefines the function gethash, which is a
  352 built-in primitive beginning with Emacs 21.1.  We don't have a patch
  353 for epop3 to fix it, but perhaps a newer version of epop3 corrects that.
  354 
  355 *** Buffers from 'with-output-to-temp-buffer' get set up in Help mode.
  356 
  357 Changes in Emacs 20.4 to the hooks used by that function cause
  358 problems for some packages, specifically BBDB.  See the function's
  359 documentation for the hooks involved.  BBDB 2.00.06 fixes the problem.
  360 
  361 *** The Hyperbole package causes *Help* buffers not to be displayed in
  362 Help mode due to setting 'temp-buffer-show-hook' rather than using
  363 'add-hook'.  Using '(add-hook 'temp-buffer-show-hook 'help-mode-finish)'
  364 after loading Hyperbole should fix this.
  365 
  366 ** Keyboard problems
  367 
  368 *** Unable to enter the M-| key on some German keyboards.
  369 Some users have reported that M-| suffers from "keyboard ghosting".
  370 This can't be fixed by Emacs, as the keypress never gets passed to it
  371 at all (as can be verified using "xev").  You can work around this by
  372 typing 'ESC |' instead.
  373 
  374 *** "Compose Character" key does strange things when used as a Meta key.
  375 
  376 If you define one key to serve as both Meta and Compose Character, you
  377 will get strange results.  In previous Emacs versions, this "worked"
  378 in that the key acted as Meta--that's because the older Emacs versions
  379 did not try to support Compose Character.  Now Emacs tries to do
  380 character composition in the standard X way.  This means that you
  381 must pick one meaning or the other for any given key.
  382 
  383 You can use both functions (Meta, and Compose Character) if you assign
  384 them to two different keys.
  385 
  386 *** C-z just refreshes the screen instead of suspending Emacs.
  387 
  388 You are probably using a shell that doesn't support job control, even
  389 though the system itself is capable of it.  Either use a different shell,
  390 or set the variable 'cannot-suspend' to a non-nil value.
  391 
  392 ** Mailers and other helper programs
  393 
  394 *** movemail compiled with POP support can't connect to the POP server.
  395 
  396 This problem can occur if you do not configure --with-mailutils,
  397 and don't have GNU Mailutils installed.  Then Emacs uses its own
  398 version of movemail, which doesn't support secure POP connections.
  399 To solve this, install GNU Mailutils.
  400 
  401 Also, make sure that the 'pop' entry in /etc/services, or in the
  402 services NIS map if your machine uses NIS, has the same port number as
  403 the entry on the POP server.  A common error is for the POP server to
  404 be listening on port 110, the assigned port for the POP3 protocol,
  405 while the client is trying to connect on port 109, the assigned port
  406 for the old POP protocol.
  407 
  408 *** RMAIL gets error getting new mail.
  409 
  410 RMAIL gets new mail from /usr/spool/mail/$USER using a program
  411 called 'movemail'.  This program interlocks with /bin/mail using
  412 the protocol defined by /bin/mail.
  413 
  414 There are two different protocols in general use.  One of them uses
  415 the 'flock' system call.  The other involves creating a lock file;
  416 'movemail' must be able to write in /usr/spool/mail in order to do
  417 this.  You control which one is used by defining, or not defining,
  418 the macro MAIL_USE_FLOCK in config.h.
  419 IF YOU DON'T USE THE FORM OF INTERLOCKING THAT IS NORMAL ON YOUR
  420 SYSTEM, YOU CAN LOSE MAIL!
  421 
  422 If your system uses the lock file protocol, and fascist restrictions
  423 prevent ordinary users from writing the lock files in /usr/spool/mail,
  424 you may need to make 'movemail' setgid to a suitable group such as
  425 'mail'.  To do this,  use the following commands (as root) after doing the
  426 make install.
  427 
  428         chgrp mail movemail
  429         chmod 2755 movemail
  430 
  431 Installation normally copies movemail from the build directory to an
  432 installation directory which is usually under /usr/local/lib.  The
  433 installed copy of movemail is usually in the directory
  434 /usr/local/lib/emacs/VERSION/TARGET.  You must change the group and
  435 mode of the installed copy; changing the group and mode of the build
  436 directory copy is ineffective.
  437 
  438 *** rcs2log gives you the awk error message "too many fields".
  439 
  440 This is due to an arbitrary limit in certain versions of awk.
  441 The solution is to use gawk (GNU awk).
  442 
  443 ** Problems with hostname resolution
  444 
  445 *** Emacs does not know your host's fully-qualified domain name.
  446 
  447 For example, (system-name) returns some variation on
  448 "localhost.localdomain", rather the name you were expecting.
  449 
  450 You need to configure your machine with a fully qualified domain name,
  451 (i.e., a name with at least one "."), either in /etc/hostname
  452 or wherever your system calls for specifying this.
  453 
  454 If you cannot fix the configuration, you can set the Lisp variable
  455 mail-host-address to the value you want.
  456 
  457 ** NFS
  458 
  459 *** Emacs says it has saved a file, but the file does not actually
  460 appear on disk.
  461 
  462 This can happen on certain systems when you are using NFS, if the
  463 remote disk is full.  It is due to a bug in NFS (or certain NFS
  464 implementations), and there is apparently nothing Emacs can do to
  465 detect the problem.  Emacs checks the failure codes of all the system
  466 calls involved in writing a file, including 'close'; but in the case
  467 where the problem occurs, none of those system calls fails.
  468 
  469 ** PSGML conflicts with sgml-mode.
  470 
  471 PSGML package uses the same names of some variables (like keymap)
  472 as built-in sgml-mode.el because it was created as a replacement
  473 of that package.  The conflict will be shown if you load
  474 sgml-mode.el before psgml.el.  E.g. this could happen if you edit
  475 HTML page and then start to work with SGML or XML file.  html-mode
  476 (from sgml-mode.el) is used for HTML file and loading of psgml.el
  477 (for sgml-mode or xml-mode) will cause an error.
  478 
  479 ** PCL-CVS
  480 
  481 *** Lines are not updated or new lines are added in the buffer upon commit.
  482 
  483 When committing files located higher in the hierarchy than the examined
  484 directory, some versions of the CVS program return an ambiguous message
  485 from which PCL-CVS cannot extract the full location of the committed
  486 files.  As a result, the corresponding lines in the PCL-CVS buffer are
  487 not updated with the new revision of these files, and new lines are
  488 added to the top-level directory.
  489 
  490 This can happen with CVS versions 1.12.8 and 1.12.9.  Upgrade to CVS
  491 1.12.10 or newer to fix this problem.
  492 
  493 ** Miscellaneous problems
  494 
  495 *** Editing files with very long lines is slow.
  496 
  497 For example, simply moving through a file that contains hundreds of
  498 thousands of characters per line is slow, and consumes a lot of CPU.
  499 This is a known limitation of Emacs with no solution at this time.
  500 
  501 *** Emacs uses 100% of CPU time
  502 
  503 This was a known problem with some old versions of the Semantic package.
  504 The solution was to upgrade Semantic to version 2.0pre4 (distributed
  505 with CEDET 1.0pre4) or later.  Note that Emacs includes Semantic since
  506 23.2, and this issue does not apply to the included version.
  507 
  508 *** Display artifacts on GUI frames on X-based systems.
  509 
  510 This is known to be caused by using double-buffering (which is enabled
  511 by default in Emacs 26 and later).  The artifacts typically appear
  512 after commands that cause Emacs to scroll the display.
  513 
  514 You can disable double-buffering by evaluating the following form:
  515 
  516   (modify-all-frames-parameters '((inhibit-double-buffering . t)))
  517 
  518 To make this permanent, add it to your ~/.emacs init file.
  519 
  520 Note that disabling double-buffering will cause flickering of the
  521 display in some situations.
  522 
  523 *** Self-documentation messages are garbled.
  524 
  525 This means that the file 'etc/DOC' doesn't properly correspond
  526 with the Emacs executable.  Redumping Emacs and then installing the
  527 corresponding pair of files should fix the problem.
  528 
  529 *** Programs running under terminal emulator do not recognize 'emacs'
  530 terminal type.
  531 
  532 The cause of this is a shell startup file that sets the TERMCAP
  533 environment variable.  The terminal emulator uses that variable to
  534 provide the information on the special terminal type that Emacs emulates.
  535 
  536 Rewrite your shell startup file so that it does not change TERMCAP
  537 in such a case.  You could use the following conditional which sets
  538 it only if it is undefined.
  539 
  540     if ( ! ${?TERMCAP} ) setenv TERMCAP ~/my-termcap-file
  541 
  542 Or you could set TERMCAP only when you set TERM--which should not
  543 happen in a non-login shell.
  544 
  545 *** In Shell mode, you get a ^M at the end of every line.
  546 
  547 This happens to people who use tcsh, because it is trying to be too
  548 smart.  It sees that the Shell uses terminal type 'unknown' and turns
  549 on the flag to output ^M at the end of each line.  You can fix the
  550 problem by adding this to your .cshrc file:
  551 
  552     if ($?INSIDE_EMACS && $?tcsh)
  553         unset edit
  554         stty -icrnl -onlcr -echo susp ^Z
  555     endif
  556 
  557 *** In Shell buffers using ksh, resizing a window inserts random characters.
  558 
  559 The characters come from the PS2 prompt, but they are not followed by
  560 a newline, which messes up the next command you type.  This strange
  561 effect is caused by Emacs 25 and later telling the shell that its
  562 screen size changed.
  563 
  564 To work around the problem, customize the option
  565 'window-adjust-process-window-size-function' to "Do not adjust process
  566 window sizes" (Lisp value 'ignore').
  567 
  568 *** In Inferior Python mode, input is echoed and native completion doesn't work.
  569 <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25753>
  570 
  571 This happens when python uses a libedit based readline module, which
  572 is the default on macOS.  This can be worked around by installing a
  573 GNU readline based module instead, for example, using setuptools
  574 
  575     sudo easy_install gnureadline
  576 
  577 And then rename the system's readline so that it won't be loaded:
  578 
  579     cd /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload
  580     mv readline.so readline.so.bak
  581 
  582 See <https://pypi.python.org/pypi/gnureadline> for more details on
  583 installation.
  584 
  585 *** Visiting files in some auto-mounted directories causes Emacs to print
  586 'Error reading dir-locals: (file-error "Read error" "is a directory" ...'
  587 
  588 This can happen if the auto-mounter mistakenly reports that
  589 .dir-locals.el exists and is a directory.  There is nothing Emacs can
  590 do about this, but you can avoid the issue by adding a suitable entry
  591 to the variable 'locate-dominating-stop-dir-regexp'.  For example, if
  592 the problem relates to "/smb/.dir-locals.el", set that variable
  593 to a new value where you replace "net\\|afs" with "net\\|afs\\|smb".
  594 (The default value already matches common auto-mount prefixes.)
  595 See https://lists.gnu.org/r/help-gnu-emacs/2015-02/msg00461.html .
  596 
  597 *** Attempting to visit remote files via ange-ftp fails.
  598 
  599 If the error message is "ange-ftp-file-modtime: Specified time is not
  600 representable", then this could happen when 'lukemftp' is used as the
  601 ftp client.  This was reported to happen on Debian GNU/Linux, kernel
  602 version 2.4.3, with 'lukemftp' 1.5-5, but might happen on other
  603 systems as well.  To avoid this problem, switch to using the standard
  604 ftp client.  On a Debian system, type
  605 
  606   update-alternatives --config ftp
  607 
  608 and then choose /usr/bin/netkit-ftp.
  609 
  610 *** Dired is very slow.
  611 
  612 This could happen if getting a file system's status takes a long
  613 time.  Possible reasons for this include:
  614 
  615   - ClearCase mounted filesystems (VOBs) that sometimes make 'df'
  616     response time extremely slow (dozens of seconds);
  617 
  618   - slow automounters on some old versions of Unix;
  619 
  620 To work around the problem, you could use Git or some other
  621 free-software program, instead of ClearCase.
  622 
  623 *** ps-print commands fail to find prologue files ps-prin*.ps.
  624 
  625 This can happen if you use an old version of X-Symbol package: it
  626 defines compatibility functions which trick ps-print into thinking it
  627 runs in XEmacs, and look for the prologue files in a wrong directory.
  628 
  629 The solution is to upgrade X-Symbol to a later version.
  630 
  631 *** On systems with shared libraries you might encounter run-time errors
  632 from the dynamic linker telling you that it is unable to find some
  633 shared libraries, for instance those for Xaw3d or image support.
  634 These errors mean Emacs has been linked with a library whose shared
  635 library is not in the default search path of the dynamic linker.
  636 
  637 Similar problems could prevent Emacs from building, since the build
  638 process invokes Emacs several times.
  639 
  640 On many systems, it is possible to set LD_LIBRARY_PATH in your
  641 environment to specify additional directories where shared libraries
  642 can be found.
  643 
  644 Other systems allow to set LD_RUN_PATH in a similar way, but before
  645 Emacs is linked.  With LD_RUN_PATH set, the linker will include a
  646 specified run-time search path in the executable.
  647 
  648 Please refer to the documentation of your dynamic linker for details.
  649 
  650 *** When you run Ispell from Emacs, it reports a "misalignment" error.
  651 
  652 This can happen if you compiled the Ispell program to use ASCII
  653 characters only and then try to use it from Emacs with non-ASCII
  654 characters, like Latin-1.  The solution is to recompile Ispell with
  655 support for 8-bit characters.
  656 
  657 To see whether your Ispell program supports 8-bit characters, type
  658 this at your shell's prompt:
  659 
  660      ispell -vv
  661 
  662 and look in the output for the string "NO8BIT".  If Ispell says
  663 "!NO8BIT (8BIT)", your speller supports 8-bit characters; otherwise it
  664 does not.
  665 
  666 To rebuild Ispell with 8-bit character support, edit the local.h file
  667 in the Ispell distribution and make sure it does _not_ define NO8BIT.
  668 Then rebuild the speller.
  669 
  670 Another possible cause for "misalignment" error messages is that the
  671 version of Ispell installed on your machine is old.  Upgrade.
  672 
  673 Yet another possibility is that you are trying to spell-check a word
  674 in a language that doesn't fit the dictionary you choose for use by
  675 Ispell.  (Ispell can only spell-check one language at a time, because
  676 it uses a single dictionary.)  Make sure that the text you are
  677 spelling and the dictionary used by Ispell conform to each other.
  678 
  679 If your spell-checking program is Aspell, it has been reported that if
  680 you have a personal configuration file (normally ~/.aspell.conf), it
  681 can cause this error.  Remove that file, execute 'ispell-kill-ispell'
  682 in Emacs, and then try spell-checking again.
  683 
  684 *** TLS problems, e.g., Gnus hangs when fetching via imaps
  685 https://debbugs.gnu.org/24247
  686 
  687 gnutls-cli 3.5.3 (2016-08-09) does not generate a "- Handshake was
  688 completed" message that tls.el relies upon, causing affected Emacs
  689 functions to hang.  To work around the problem, use older or newer
  690 versions of gnutls-cli, or use Emacs's built-in gnutls support.
  691 
  692 * Runtime problems related to font handling
  693 
  694 ** Characters are displayed as empty boxes or with wrong font under X.
  695 
  696 *** This may be due to your local fontconfig customization.
  697 Try removing or moving aside "$XDG_CONFIG_HOME/fontconfig/conf.d" and
  698 "$XDG_CONFIG_HOME/fontconfig/fonts.conf"
  699 ($XDG_CONFIG_HOME is treated as "~/.config" if not set)
  700 
  701 *** This can occur when two different versions of FontConfig are used.
  702 For example, XFree86 4.3.0 has one version and Gnome usually comes
  703 with a newer version.  Emacs compiled with Gtk+ will then use the
  704 newer version.  In most cases the problem can be temporarily fixed by
  705 stopping the application that has the error (it can be Emacs or any
  706 other application), removing ~/.fonts.cache-1, and then starting the
  707 application again.  If removing ~/.fonts.cache-1 and restarting
  708 doesn't help, the application with problem must be recompiled with the
  709 same version of FontConfig as the rest of the system uses.  For KDE,
  710 it is sufficient to recompile Qt.
  711 
  712 *** Some fonts have a missing glyph and no default character.  This is
  713 known to occur for character number 160 (no-break space) in some
  714 fonts, such as Lucida but Emacs sets the display table for the unibyte
  715 and Latin-1 version of this character to display a space.
  716 
  717 *** Some of the fonts called for in your fontset may not exist on your
  718 X server.
  719 
  720 Each X font covers just a fraction of the characters that Emacs
  721 supports.  To display the whole range of Emacs characters requires
  722 many different fonts, collected into a fontset.  You can remedy the
  723 problem by installing additional fonts.
  724 
  725 The intlfonts distribution includes a full spectrum of fonts that can
  726 display all the characters Emacs supports.  The etl-unicode collection
  727 of fonts (available from
  728 <https://ftp.nluug.nl/windowing/X/contrib/fonts/>) includes fonts that
  729 can display many Unicode characters; they can also be used by ps-print
  730 and ps-mule to print Unicode characters.
  731 
  732 ** Under X, some characters appear improperly aligned in their lines.
  733 
  734 You may have bad fonts.
  735 
  736 ** Under X, some characters are unexpectedly wide.
  737 
  738 e.g. recent versions of Inconsolata show this issue for almost all of
  739 its characters.  Due to what is probably an Xft bug, the determination
  740 of the width of some characters is incorrect.  One workaround is to
  741 build emacs with Cairo enabled ("configure --with-cairo" and have the
  742 appropriate Cairo development packages installed) as this
  743 configuration does not suffer from this problem.  See
  744 <https://github.com/googlefonts/Inconsolata/issues/42> and
  745 <https://lists.gnu.org/archive/html/bug-gnu-emacs/2020-01/msg00456.html>
  746 for more discussion.
  747 
  748 ** Under X, an unexpected monospace font is used as the default font.
  749 
  750 When compiled with XFT, Emacs tries to use a default font named
  751 "monospace".  This is a "virtual font", which the operating system
  752 (Fontconfig) redirects to a suitable font such as DejaVu Sans Mono.
  753 On some systems, there exists a font that is actually named Monospace,
  754 which takes over the virtual font.  This is considered an operating
  755 system bug; see
  756 
  757 https://lists.gnu.org/r/emacs-devel/2008-10/msg00696.html
  758 
  759 If you encounter this problem, set the default font to a specific font
  760 in your .Xresources or initialization file.  For instance, you can put
  761 the following in your .Xresources:
  762 
  763 Emacs.font: DejaVu Sans Mono 12
  764 
  765 ** Certain fonts make each line take one pixel more than it should.
  766 
  767 This is because these fonts contain characters a little taller than
  768 the font's nominal height.  Emacs needs to make sure that lines do not
  769 overlap.
  770 
  771 ** Font Lock displays portions of the buffer in incorrect faces.
  772 
  773 By far the most frequent cause of this is a parenthesis '(' or a brace
  774 '{' in column zero.  Font Lock assumes that such a paren is outside of
  775 any comment or string.  This is of course not true in general, but the
  776 vast majority of well-formatted program source files don't have such
  777 parens, and therefore this assumption is used to allow optimizations
  778 in Font Lock's syntactical analysis.  These optimizations avoid some
  779 pathological cases where jit-lock, the Just-in-Time fontification
  780 introduced with Emacs 21.1, could significantly slow down scrolling
  781 through the buffer, especially scrolling backwards, and also jumping
  782 to the end of a very large buffer.
  783 
  784 Beginning with version 22.1, a parenthesis or a brace in column zero
  785 is highlighted in bold-red face if it is inside a string or a comment,
  786 to indicate that it could interfere with Font Lock (and also with
  787 indentation) and should be moved or escaped with a backslash.
  788 
  789 If you don't use large buffers, or have a very fast machine which
  790 makes the delays insignificant, you can avoid the incorrect
  791 fontification by setting the variable
  792 'font-lock-beginning-of-syntax-function' to a nil value.  (This must
  793 be done _after_ turning on Font Lock.)
  794 
  795 Another alternative is to avoid a paren in column zero.  For example,
  796 in a Lisp string you could precede the paren with a backslash.
  797 
  798 ** Emacs pauses for several seconds when changing the default font.
  799 
  800 This has been reported for fvwm 2.2.5 and the window manager of KDE
  801 2.1.  The reason for the pause is Xt waiting for a ConfigureNotify
  802 event from the window manager, which the window manager doesn't send.
  803 Xt stops waiting after a default timeout of usually 5 seconds.
  804 
  805 A workaround for this is to add something like
  806 
  807 emacs.waitForWM: false
  808 
  809 to your X resources.  Alternatively, add '(wait-for-wm . nil)' to a
  810 frame's parameter list, like this:
  811 
  812    (modify-frame-parameters nil '((wait-for-wm . nil)))
  813 
  814 (this should go into your '.emacs' file).
  815 
  816 ** Underlines appear at the wrong position.
  817 
  818 This is caused by fonts having a wrong UNDERLINE_POSITION property.
  819 To avoid this problem (seen in some very old X releases and font packages),
  820 set x-use-underline-position-properties to nil.
  821 
  822 To see what is the value of UNDERLINE_POSITION defined by the font,
  823 type 'xlsfonts -lll FONT' and look at the font's UNDERLINE_POSITION property.
  824 
  825 ** When using Exceed, fonts sometimes appear too tall.
  826 
  827 When the display is set to an Exceed X-server and fonts are specified
  828 (either explicitly with the -fn option or implicitly with X resources)
  829 then the fonts may appear "too tall".  The actual character sizes are
  830 correct but there is too much vertical spacing between rows,  which
  831 gives the appearance of "double spacing".
  832 
  833 To prevent this, turn off the Exceed's "automatic font substitution"
  834 feature (in the font part of the configuration window).
  835 
  836 ** Subscript/superscript text in TeX is hard to read.
  837 
  838 If 'tex-fontify-script' is non-nil, tex-mode displays
  839 subscript/superscript text in the faces subscript/superscript, which
  840 are smaller than the normal font and lowered/raised.  With some fonts,
  841 nested superscripts (say) can be hard to read.  Switching to a
  842 different font, or changing your antialiasing setting (on an LCD
  843 screen), can both make the problem disappear.  Alternatively, customize
  844 the following variables: tex-font-script-display (how much to
  845 lower/raise); tex-suscript-height-ratio (how much smaller than
  846 normal); tex-suscript-height-minimum (minimum height).
  847 
  848 ** Screen refresh is slow when there are special characters for which no suitable font is available
  849 
  850 If the display is too slow in refreshing when you scroll to a new
  851 region, or when you edit the buffer, it might be due to the fact that
  852 some characters cannot be displayed in the default font, and Emacs is
  853 spending too much time in looking for a suitable font to display them.
  854 
  855 You can suspect this if you have several characters that are displayed
  856 as small rectangles containing a hexadecimal code inside.
  857 
  858 The solution is to install the appropriate fonts on your machine. For
  859 instance if you are editing a text with a lot of math symbols, then
  860 installing a font like 'Symbola' should solve this problem.
  861 
  862 Another reason for slow display is reportedly the nerd-fonts
  863 installation, even when Symbola is installed as well.  Uninstalling
  864 nerd-fonts was reported to solve the problem in that case.
  865 
  866 ** Emacs running on GNU/Linux system with the m17n library Ver.1.7.1 or the
  867 earlier version has a problem with rendering Bengali script.
  868 
  869 The problem can be fixed by installing the newer version of the m17n
  870 library (if any), or by following this procedure:
  871 
  872 1. Locate the file BENG-OTF.flt installed on your system as part of the
  873 m17n library.  Usually it is under the directory /usr/share/m17n.
  874 
  875 2. Apply the following patch to BENG-OTF.flt
  876 
  877 ------------------------------------------------------------
  878 diff --git a/FLT/BENG-OTF.flt b/FLT/BENG-OTF.flt
  879 index 45cc554..0cc5e76 100644
  880 --- a/FLT/BENG-OTF.flt
  881 +++ b/FLT/BENG-OTF.flt
  882 @@ -232,7 +232,7 @@
  883   (lang-forms
  884    (cond
  885     ("(.H)J" (1 :otf=beng=half+))
  886 -   (".H" :otf=beng=blwf,half,vatu+)
  887 +   (".+H" :otf=beng=blwf,half,vatu+)
  888     ("." =)))
  889 
  890   (post
  891 ------------------------------------------------------------
  892 
  893 If you can't modify that file directly, copy it to the directory
  894 ~/.m17n.d/ (create it if it doesn't exist), and apply the patch.
  895 
  896 ** Emacs running on GNU/Linux system with the m17n library Ver.1.7.1 or the
  897 earlier version has a problem with rendering Lao script with OpenType font.
  898 
  899 The problem can be fixed by installing the newer version of the m17n
  900 library (if any), or by following this procedure:
  901 
  902 1. Locate the file LAOO-OTF.flt installed on your system as part of the
  903 m17n library.  Usually it is under the directory /usr/share/m17n.
  904 
  905 2. Apply the following patch to LAOO-OTF.flt
  906 
  907 ------------------------------------------------------------
  908 diff --git a/FLT/LAOO-OTF.flt b/FLT/LAOO-OTF.flt
  909 index 5504171..431adf8 100644
  910 --- a/FLT/LAOO-OTF.flt
  911 +++ b/FLT/LAOO-OTF.flt
  912 @@ -3,7 +3,7 @@
  913  ;; See the end for copying conditions.
  914 
  915  (font layouter laoo-otf nil
  916 -      (font (nil phetsarath\ ot unicode-bmp)))
  917 +      (font (nil nil unicode-bmp :otf=lao\ )))
  918 
  919  ;;; <li> LAOO-OTF.flt
  920 
  921 ------------------------------------------------------------
  922 
  923 If you can't modify that file directly, copy it to the directory
  924 ~/.m17n.d/ (create it if it doesn't exist), and apply the patch.
  925 
  926 ** On MS-Windows, some characters display as boxes with hex code.
  927 
  928 Also, some characters could display with wrong fonts.
  929 
  930 This can happen if Emacs was compiled without HarfBuzz support, and/or
  931 if the HarfBuzz DLLs are not available at run time.  Emacs will then
  932 fall back to the Uniscribe as its shaping engine; Uniscribe was
  933 deprecated by Microsoft, and sometimes fails to display correctly when
  934 modern fonts are used, such as Noto Emoji or Ebrima.
  935 
  936 The solution is to switch to a configuration that uses HarfBuzz as its
  937 shaping engine, where these problems don't exist.
  938 
  939 * Internationalization problems
  940 
  941 ** M-{ does not work on a Spanish PC keyboard.
  942 
  943 Many Spanish keyboards seem to ignore that combination.  Emacs can't
  944 do anything about it.
  945 
  946 ** International characters aren't displayed under X.
  947 
  948 *** Missing X fonts
  949 
  950 XFree86 4 contains many fonts in iso10646-1 encoding which have
  951 minimal character repertoires (whereas the encoding part of the font
  952 name is meant to be a reasonable indication of the repertoire
  953 according to the XLFD spec).  Emacs may choose one of these to display
  954 characters from the mule-unicode charsets and then typically won't be
  955 able to find the glyphs to display many characters.  (Check with C-u
  956 C-x = .)  To avoid this, you may need to use a fontset which sets the
  957 font for the mule-unicode sets explicitly.  E.g. to use GNU unifont,
  958 include in the fontset spec:
  959 
  960 mule-unicode-2500-33ff:-gnu-unifont-*-iso10646-1,\
  961 mule-unicode-e000-ffff:-gnu-unifont-*-iso10646-1,\
  962 mule-unicode-0100-24ff:-gnu-unifont-*-iso10646-1
  963 
  964 ** The UTF-8/16/7 coding systems don't encode CJK (Far Eastern) characters.
  965 
  966 Emacs directly supports the Unicode BMP whose code points are in the
  967 ranges 0000-33ff and e000-ffff, and indirectly supports the parts of
  968 CJK characters belonging to these legacy charsets:
  969 
  970     GB2312, Big5, JISX0208, JISX0212, JISX0213-1, JISX0213-2, KSC5601
  971 
  972 The latter support is done in Utf-Translate-Cjk mode (turned on by
  973 default).   Which Unicode CJK characters are decoded into which Emacs
  974 charset is decided by the current language environment.  For instance,
  975 in Chinese-GB, most of them are decoded into chinese-gb2312.
  976 
  977 If you read UTF-8 data with code points outside these ranges, the
  978 characters appear in the buffer as raw bytes of the original UTF-8
  979 (composed into a single quasi-character) and they will be written back
  980 correctly as UTF-8, assuming you don't break the composed sequences.
  981 If you read such characters from UTF-16 or UTF-7 data, they are
  982 substituted with the Unicode 'replacement character', and you lose
  983 information.
  984 
  985 ** Accented ISO-8859-1 characters are displayed as | or _.
  986 
  987 Try other font set sizes (S-mouse-1).  If the problem persists with
  988 other sizes as well, your text is corrupted, probably through software
  989 that is not 8-bit clean.  If the problem goes away with another font
  990 size, it's probably because some fonts pretend to be ISO-8859-1 fonts
  991 when they are really ASCII fonts.  In particular the schumacher-clean
  992 fonts have this bug in some versions of X.
  993 
  994 To see what glyphs are included in a font, use 'xfd', like this:
  995 
  996   xfd -fn -schumacher-clean-medium-r-normal--12-120-75-75-c-60-iso8859-1
  997 
  998 If this shows only ASCII glyphs, the font is indeed the source of the problem.
  999 
 1000 The solution is to remove the corresponding lines from the appropriate
 1001 'fonts.alias' file, then run 'mkfontdir' in that directory, and then run
 1002 'xset fp rehash'.
 1003 
 1004 ** The 'oc-unicode' package doesn't work with Emacs 21.
 1005 
 1006 This package tries to define more private charsets than there are free
 1007 slots now.  The current built-in Unicode support is actually more
 1008 flexible.  (Use option 'utf-translate-cjk-mode' if you need CJK
 1009 support.)  Files encoded as emacs-mule using oc-unicode aren't
 1010 generally read correctly by Emacs 21.
 1011 
 1012 * X runtime problems
 1013 
 1014 ** X keyboard problems
 1015 
 1016 *** You "lose characters" after typing Compose Character key.
 1017 
 1018 This is because the Compose Character key is defined as the keysym
 1019 Multi_key, and Emacs (seeing that) does the proper X
 1020 character-composition processing.  If you don't want your Compose key
 1021 to do that, you can redefine it with xmodmap.
 1022 
 1023 For example, here's one way to turn it into a Meta key:
 1024 
 1025     xmodmap -e "keysym Multi_key = Meta_L"
 1026 
 1027 If all users at your site of a particular keyboard prefer Meta to
 1028 Compose, you can make the remapping happen automatically by adding the
 1029 xmodmap command to the xdm setup script for that display.
 1030 
 1031 *** Using X Window System, control-shift-leftbutton makes Emacs hang.
 1032 
 1033 Use the shell command 'xset bc' to make the old X Menu package work.
 1034 
 1035 *** C-SPC fails to work on Fedora GNU/Linux (or with fcitx input method).
 1036 
 1037 Fedora Core 4 steals the C-SPC key by default for the 'iiimx' program
 1038 which is the input method for some languages.  It blocks Emacs users
 1039 from using the C-SPC key for 'set-mark-command'.
 1040 
 1041 One solutions is to remove the '<Ctrl>space' from the 'Iiimx' file
 1042 which can be found in the '/usr/lib/X11/app-defaults' directory.
 1043 However, that requires root access.
 1044 
 1045 Another is to specify 'Emacs*useXIM: false' in your X resources.
 1046 
 1047 Another is to build Emacs with the '--without-xim' configure option.
 1048 
 1049 The same problem happens on any other system if you are using fcitx
 1050 (Chinese input method) which by default use C-SPC for toggling.  If
 1051 you want to use fcitx with Emacs, you have two choices.  Toggle fcitx
 1052 by another key (e.g. C-\) by modifying ~/.fcitx/config, or be
 1053 accustomed to use C-@ for 'set-mark-command'.
 1054 
 1055 *** Link-time optimization with clang doesn't work on Fedora 20.
 1056 
 1057 As of May 2014, Fedora 20 has broken LLVMgold.so plugin support in clang
 1058 (tested with clang-3.4-6.fc20) - 'clang --print-file-name=LLVMgold.so'
 1059 prints 'LLVMgold.so' instead of full path to plugin shared library, and
 1060 'clang -flto' is unable to find the plugin with the following error:
 1061 
 1062 /bin/ld: error: /usr/bin/../lib/LLVMgold.so: could not load plugin library:
 1063 /usr/bin/../lib/LLVMgold.so: cannot open shared object file: No such file
 1064 or directory
 1065 
 1066 The only way to avoid this is to build your own clang from source code
 1067 repositories, as described at http://clang.llvm.org/get_started.html.
 1068 
 1069 *** M-SPC seems to be ignored as input.
 1070 
 1071 See if your X server is set up to use this as a command
 1072 for character composition.
 1073 
 1074 *** The S-C-t key combination doesn't get passed to Emacs on X.
 1075 
 1076 This happens because some X configurations assign the Ctrl-Shift-t
 1077 combination the same meaning as the Multi_key.  The offending
 1078 definition is in the file '...lib/X11/locale/iso8859-1/Compose'; there
 1079 might be other similar combinations which are grabbed by X for similar
 1080 purposes.
 1081 
 1082 We think that this can be countermanded with the 'xmodmap' utility, if
 1083 you want to be able to bind one of these key sequences within Emacs.
 1084 
 1085 *** Under X, C-v and/or other keys don't work.
 1086 
 1087 These may have been intercepted by your window manager.
 1088 See the WM's documentation for how to change this.
 1089 
 1090 *** Clicking C-mouse-2 in the scroll bar doesn't split the window.
 1091 
 1092 This currently doesn't work with scroll-bar widgets (and we don't know
 1093 a good way of implementing it with widgets).  If Emacs is configured
 1094 --without-toolkit-scroll-bars, C-mouse-2 on the scroll bar does work.
 1095 
 1096 *** Inability to send an Alt-modified key, when Emacs is communicating
 1097 directly with an X server.
 1098 
 1099 If you have tried to bind an Alt-modified key as a command, and it
 1100 does not work to type the command, the first thing you should check is
 1101 whether the key is getting through to Emacs.  To do this, type C-h c
 1102 followed by the Alt-modified key.  C-h c should say what kind of event
 1103 it read.  If it says it read an Alt-modified key, then make sure you
 1104 have made the key binding correctly.
 1105 
 1106 If C-h c reports an event that doesn't have the Alt modifier, it may
 1107 be because your X server has no key for the Alt modifier.  The X
 1108 server that comes from MIT does not set up the Alt modifier by default.
 1109 
 1110 If your keyboard has keys named Alt, you can enable them as follows:
 1111 
 1112     xmodmap -e 'add mod2 = Alt_L'
 1113     xmodmap -e 'add mod2 = Alt_R'
 1114 
 1115 If the keyboard has just one key named Alt, then only one of those
 1116 commands is needed.  The modifier 'mod2' is a reasonable choice if you
 1117 are using an unmodified MIT version of X.  Otherwise, choose any
 1118 modifier bit not otherwise used.
 1119 
 1120 If your keyboard does not have keys named Alt, you can use some other
 1121 keys.  Use the keysym command in xmodmap to turn a function key (or
 1122 some other 'spare' key) into Alt_L or into Alt_R, and then use the
 1123 commands show above to make them modifier keys.
 1124 
 1125 Note that if you have Alt keys but no Meta keys, Emacs translates Alt
 1126 into Meta.  This is because of the great importance of Meta in Emacs.
 1127 
 1128 *** Emacs hangs or crashes when a large portion of text is selected or killed.
 1129 
 1130 This is caused by a bug in the clipboard management applets (it has
 1131 been observed in 'klipper' and 'clipit'), which periodically request
 1132 the X clipboard contents from applications.  After a while, Emacs may
 1133 print a message:
 1134 
 1135   Timed out waiting for property-notify event
 1136 
 1137 A workaround is to not use 'klipper'/'clipit'.  Upgrading 'klipper' to
 1138 the one coming with KDE 3.3 or later might solve the problem; if it
 1139 doesn't, set 'select-active-regions' to 'only' or nil.
 1140 
 1141 ** Window-manager and toolkit-related problems
 1142 
 1143 *** Emacs built with GTK+ toolkit produces corrupted display on HiDPI screen
 1144 
 1145 This can happen if you set GDK_SCALE=2 in the environment or in your
 1146 '.xinitrc' file.  (This setting is usually accompanied by
 1147 GDK_DPI_SCALE=0.5.)  Emacs can not support these settings correctly,
 1148 as it doesn't use GTK+ exclusively.  The result is that sometimes
 1149 widgets like the scroll bar are displayed incorrectly, and frames
 1150 could be displayed "cropped" to only part of the stuff that should be
 1151 displayed.
 1152 
 1153 The workaround is to explicitly disable these settings when invoking
 1154 Emacs, for example (from a Posix shell prompt):
 1155 
 1156   $ GDK_SCALE=1 GDK_DPI_SCALE=1 emacs
 1157 
 1158 *** Emacs built with GTK+ toolkit can unexpectedly widen frames
 1159 
 1160 This resizing takes place when a frame is not wide enough to accommodate
 1161 its entire menu bar.  Typically, it occurs when switching buffers or
 1162 changing a buffer's major mode and the new mode adds entries to the menu
 1163 bar.  The frame is then widened by the window manager so that the menu
 1164 bar is fully shown.  Subsequently switching to another buffer or
 1165 changing the buffer's mode will not shrink the frame back to its
 1166 previous width.  The height of the frame remains unaltered.  Apparently,
 1167 the failure is also dependent on the chosen font.
 1168 
 1169 The resizing is usually accompanied by console output like
 1170 
 1171 Gtk-CRITICAL **: gtk_distribute_natural_allocation: assertion 'extra_space >= 0' failed
 1172 
 1173 It's not clear whether the GTK version used has any impact on the
 1174 occurrence of the failure.  So far, the failure has been observed with
 1175 GTK+ versions 3.4.2, 3.14.5 and 3.18.7.  However, another 3.4.2 build
 1176 does not exhibit the bug.
 1177 
 1178 Some window managers (Xfce) apparently work around this failure by
 1179 cropping the menu bar.  With other windows managers, it's possible to
 1180 shrink the frame manually after the problem occurs, e.g. by dragging the
 1181 frame's border with the mouse.  However, some window managers have been
 1182 reported to refuse such attempts and snap back to the width needed to
 1183 show the full menu bar (wmii) or at least cause the screen to flicker
 1184 during such resizing attempts (i3, IceWM).
 1185 
 1186 See also https://debbugs.gnu.org/cgi/bugreport.cgi?bug=15700,
 1187 https://debbugs.gnu.org/cgi/bugreport.cgi?bug=22000,
 1188 https://debbugs.gnu.org/cgi/bugreport.cgi?bug=22898 and
 1189 https://lists.gnu.org/r/emacs-devel/2016-07/msg00154.html.
 1190 
 1191 *** Metacity: Resizing Emacs or ALT-Tab causes X to be unresponsive.
 1192 
 1193 This happens sometimes when using Metacity.  Resizing Emacs or ALT-Tab:bing
 1194 makes the system unresponsive to the mouse or the keyboard.  Killing Emacs
 1195 or shifting out from X and back again usually cures it (i.e. Ctrl-Alt-F1
 1196 and then Alt-F7).  A bug for it is here:
 1197 https://bugs.launchpad.net/ubuntu/+source/metacity/+bug/231034.
 1198 Note that a permanent fix seems to be to disable "assistive technologies".
 1199 
 1200 *** Gnome: Emacs receives input directly from the keyboard, bypassing XIM.
 1201 
 1202 This seems to happen when gnome-settings-daemon version 2.12 or later
 1203 is running.  If gnome-settings-daemon is not running, Emacs receives
 1204 input through XIM without any problem.  Furthermore, this seems only
 1205 to happen in *.UTF-8 locales; zh_CN.GB2312 and zh_CN.GBK locales, for
 1206 example, work fine.  A bug report has been filed in the Gnome
 1207 bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=357032
 1208 
 1209 *** Gnome: GPaste clipboard manager causes erratic behavior of 'yank'
 1210 
 1211 The symptom is that 'kill-line' followed by 'yank' often (but not
 1212 always) doesn't insert the whitespace of the killed and yanked line.
 1213 
 1214 The solution is to set the GPaste "trim items" option to OFF.
 1215 
 1216 *** Gnome: Navigation from Nautilus to remote files.
 1217 
 1218 If you navigate to a file, which belongs to a remote server, in
 1219 Nautilus via "Open With Emacs" you might not be able to save this file
 1220 once you have modified it in Emacs.  The reasons for the failure can
 1221 vary, and for some connection methods saving the file might even succeed.
 1222 
 1223 If the remote connection in Nautilus uses ssh or sftp, you could
 1224 mitigate the problem by the following lines in your .emacs file:
 1225 
 1226 (dir-locals-set-class-variables 'gvfs '((nil . ((create-lockfiles . nil)))))
 1227 (dir-locals-set-directory-class (format "/run/user/%d/gvfs" (user-uid)) 'gvfs)
 1228 
 1229 A better approach might be to avoid navigation from Nautilus to Emacs
 1230 for such files, and instead to open the file in Emacs using Tramp
 1231 remote file name syntax.
 1232 
 1233 *** KDE: When running on KDE, colors or fonts are not as specified for Emacs,
 1234 or messed up.
 1235 
 1236 For example, you could see background you set for Emacs only in the
 1237 empty portions of the Emacs display, while characters have some other
 1238 background.
 1239 
 1240 This happens because KDE's defaults apply its color and font
 1241 definitions even to applications that weren't compiled for KDE.  The
 1242 solution is to uncheck the "Apply fonts and colors to non-KDE apps"
 1243 option in Preferences->Look&Feel->Style (KDE 2).  In KDE 3, this option
 1244 is in the "Colors" section, rather than "Style".
 1245 
 1246 Alternatively, if you do want the KDE defaults to apply to other
 1247 applications, but not to Emacs, you could modify the file 'Emacs.ad'
 1248 (should be in the '/usr/share/apps/kdisplay/app-defaults/' directory)
 1249 so that it doesn't set the default background and foreground only for
 1250 Emacs.  For example, make sure the following resources are either not
 1251 present or commented out:
 1252 
 1253    Emacs.default.attributeForeground
 1254    Emacs.default.attributeBackground
 1255    Emacs*Foreground
 1256    Emacs*Background
 1257 
 1258 It is also reported that a bug in the gtk-engines-qt engine can cause this if
 1259 Emacs is compiled with Gtk+.
 1260 The bug is fixed in version 0.7 or newer of gtk-engines-qt.
 1261 
 1262 *** KDE / Plasma 5: Emacs exhausts memory and needs to be killed
 1263 
 1264 This problem occurs when large selections contain mixed line endings
 1265 (i.e. the buffer has LF line endings, but in some parts CRLF is used).
 1266 The source of the problem is currently under investigation, older
 1267 versions of Emacs up to 24.5 just hang for a few seconds and then
 1268 return with the message "Timed out waiting for property-notify event"
 1269 as described in the previous note.  As a workaround, go to the
 1270 settings dialog for the Clipboard widget and select the option "Ignore
 1271 Selection".
 1272 
 1273 Note: Plasma 5 has replaced the separate klipper process from earlier
 1274 KDE versions with functionality directly integrated into plasmashell,
 1275 so even if you've previously did not use klipper this will affect you.
 1276 Also, all configuration you might have done to klipper is not used by
 1277 the new Clipboard widget / plasmoid since it uses its own settings.
 1278 You can hide the Clipboard widget by removing its entry from the
 1279 system tray settings "Extra Items", but it's not clear if the
 1280 underlying functionality in plasmashell gets fully disabled as well.
 1281 At least a restart of plasmashell is required for the clipboard
 1282 history to be cleared.
 1283 
 1284 *** CDE: Frames may cover dialogs they created when using CDE.
 1285 
 1286 This can happen if you have "Allow Primary Windows On Top" enabled which
 1287 seems to be the default in the Common Desktop Environment.
 1288 To change, go in to "Desktop Controls" -> "Window Style Manager"
 1289 and uncheck "Allow Primary Windows On Top".
 1290 
 1291 *** Xaw3d : When using Xaw3d scroll bars without arrows, the very first mouse
 1292 click in a scroll bar might be ignored by the scroll bar widget.  This
 1293 is probably a bug in Xaw3d; when Xaw3d is compiled with arrows, the
 1294 problem disappears.
 1295 
 1296 *** Xaw: There are known binary incompatibilities between Xaw, Xaw3d, neXtaw,
 1297 XawM and the few other derivatives of Xaw.  So when you compile with
 1298 one of these, it may not work to dynamically link with another one.
 1299 For example, strange problems, such as Emacs exiting when you type
 1300 "C-x 1", were reported when Emacs compiled with Xaw3d and libXaw was
 1301 used with neXtaw at run time.
 1302 
 1303 The solution is to rebuild Emacs with the toolkit version you actually
 1304 want to use, or set LD_PRELOAD to preload the same toolkit version you
 1305 built Emacs with.
 1306 
 1307 *** Open Motif: Problems with file dialogs in Emacs built with Open Motif.
 1308 
 1309 When Emacs 21 is built with Open Motif 2.1, it can happen that the
 1310 graphical file dialog boxes do not work properly.  The "OK", "Filter"
 1311 and "Cancel" buttons do not respond to mouse clicks.  Dragging the
 1312 file dialog window usually causes the buttons to work again.
 1313 
 1314 As a workaround, you can try building Emacs using Motif or LessTif instead.
 1315 
 1316 Another workaround is not to use the mouse to trigger file prompts,
 1317 but to use the keyboard.  This way, you will be prompted for a file in
 1318 the minibuffer instead of a graphical file dialog.
 1319 
 1320 *** LessTif: Problems in Emacs built with LessTif.
 1321 
 1322 The problems seem to depend on the version of LessTif and the Motif
 1323 emulation for which it is set up.
 1324 
 1325 Only the Motif 1.2 emulation seems to be stable enough in LessTif.
 1326 LessTif 0.92-17's Motif 1.2 emulation seems to work okay on FreeBSD.
 1327 On GNU/Linux systems, lesstif-0.92.6 configured with "./configure
 1328 --enable-build-12 --enable-default-12" is reported to be the most
 1329 successful.  The binary GNU/Linux package
 1330 lesstif-devel-0.92.0-1.i386.rpm was reported to have problems with
 1331 menu placement.
 1332 
 1333 On some systems, Emacs occasionally locks up, grabbing all mouse and
 1334 keyboard events.  We don't know what causes these problems; they are
 1335 not reproducible by Emacs developers.
 1336 
 1337 *** Motif: The Motif version of Emacs paints the screen a solid color.
 1338 
 1339 This has been observed to result from the following X resource:
 1340 
 1341    Emacs*default.attributeFont:	-*-courier-medium-r-*-*-*-140-*-*-*-*-iso8859-*
 1342 
 1343 That the resource has this effect indicates a bug in something, but we
 1344 do not know what.  If it is an Emacs bug, we hope someone can
 1345 explain what the bug is so we can fix it.  In the mean time, removing
 1346 the resource prevents the problem.
 1347 
 1348 *** FVWM: Some versions of FVWM incorrectly set the 'sticky' frame parameter.
 1349 
 1350 Version 2.6.4 of the FVWM can make a frame sticky (appear on all user
 1351 desktops) when setting the 'sticky' frame parameter to nil.  This may
 1352 happen without any special user interaction, for example, when Emacs
 1353 restores a saved desktop.  A fix is to install version 2.6.8 of FVWM,
 1354 see https://debbugs.gnu.org/cgi/bugreport.cgi?bug=31650.
 1355 
 1356 ** General X problems
 1357 
 1358 *** Redisplay using X is much slower than previous Emacs versions.
 1359 
 1360 We've noticed that certain X servers draw the text much slower when
 1361 scroll bars are on the left.  We don't know why this happens.  If this
 1362 happens to you, you can work around it by putting the scroll bars
 1363 on the right (as they were in Emacs 19).
 1364 
 1365 Here's how to do this:
 1366 
 1367   (set-scroll-bar-mode 'right)
 1368 
 1369 If you're not sure whether (or how much) this problem affects you,
 1370 try that and see how much difference it makes.  To set things back
 1371 to normal, do
 1372 
 1373   (set-scroll-bar-mode 'left)
 1374 
 1375 *** Error messages about undefined colors on X.
 1376 
 1377 The messages might say something like this:
 1378 
 1379    Unable to load color "grey95"
 1380 
 1381 (typically, in the '*Messages*' buffer), or something like this:
 1382 
 1383   Error while displaying tooltip: (error Undefined color lightyellow)
 1384 
 1385 These problems could happen if some other X program has used up too
 1386 many colors of the X palette, leaving Emacs with insufficient system
 1387 resources to load all the colors it needs.
 1388 
 1389 A solution is to exit the offending X programs before starting Emacs.
 1390 
 1391 "undefined color" messages can also occur if the RgbPath entry in the
 1392 X configuration file is incorrect, or the rgb.txt file is not where
 1393 X expects to find it.
 1394 
 1395 *** Improving performance with slow X connections.
 1396 
 1397 There are several ways to improve this performance, any subset of which can
 1398 be carried out at the same time:
 1399 
 1400 1) If you don't need X Input Methods (XIM) for entering text in some
 1401    language you use, you can improve performance on WAN links by using
 1402    the X resource useXIM to turn off use of XIM.  This does not affect
 1403    the use of Emacs's own input methods, which are part of the Leim
 1404    package.
 1405 
 1406 2) If the connection is very slow, you might also want to consider
 1407    switching off scroll bars, menu bar, and tool bar.  Adding the
 1408    following forms to your .emacs file will accomplish that, but only
 1409    after the initial frame is displayed:
 1410 
 1411     (scroll-bar-mode -1)
 1412     (menu-bar-mode -1)
 1413     (tool-bar-mode -1)
 1414 
 1415    For still quicker startup, put these X resources in your
 1416    .Xresources or .Xdefaults file:
 1417 
 1418     Emacs.verticalScrollBars: off
 1419     Emacs.menuBar: off
 1420     Emacs.toolBar: off
 1421 
 1422 3) Use ssh to forward the X connection, and enable compression on this
 1423    forwarded X connection (ssh -XC remotehostname emacs ...).
 1424 
 1425 4) Use lbxproxy on the remote end of the connection.  This is an interface
 1426    to the low bandwidth X extension in most modern X servers, which
 1427    improves performance dramatically, at the slight expense of correctness
 1428    of the X protocol.  lbxproxy achieves the performance gain by grouping
 1429    several X requests in one TCP packet and sending them off together,
 1430    instead of requiring a round-trip for each X request in a separate
 1431    packet.  The switches that seem to work best for emacs are:
 1432     -noatomsfile  -nowinattr  -cheaterrors -cheatevents
 1433    Note that the -nograbcmap option is known to cause problems.
 1434    For more about lbxproxy, see:
 1435    http://www.x.org/archive/X11R6.8.0/doc/lbxproxy.1.html
 1436 
 1437 5) If copying and killing is slow, try to disable the interaction with the
 1438    native system's clipboard by adding these lines to your .emacs file:
 1439      (setq interprogram-cut-function nil)
 1440      (setq interprogram-paste-function nil)
 1441 
 1442 *** Emacs gives the error, Couldn't find per display information.
 1443 
 1444 This can result if the X server runs out of memory because Emacs uses
 1445 a large number of fonts.  On systems where this happens, C-h h is
 1446 likely to cause it.
 1447 
 1448 We do not know of a way to prevent the problem.
 1449 
 1450 *** Emacs does not notice when you release the mouse.
 1451 
 1452 There are reports that this happened with (some) Microsoft mice and
 1453 that replacing the mouse made it stop.
 1454 
 1455 *** You can't select from submenus (in the X toolkit version).
 1456 
 1457 On certain systems, mouse-tracking and selection in top-level menus
 1458 works properly with the X toolkit, but neither of them works when you
 1459 bring up a submenu (such as Bookmarks or Compare or Apply Patch, in
 1460 the Files menu).
 1461 
 1462 This works on most systems.  There is speculation that the failure is
 1463 due to bugs in old versions of X toolkit libraries, but no one really
 1464 knows.  If someone debugs this and finds the precise cause, perhaps a
 1465 workaround can be found.
 1466 
 1467 *** An error message such as 'X protocol error: BadMatch (invalid
 1468 parameter attributes) on protocol request 93'.
 1469 
 1470 This comes from having an invalid X resource, such as
 1471    emacs*Cursor:   black
 1472 (which is invalid because it specifies a color name for something
 1473 that isn't a color.)
 1474 
 1475 The fix is to correct your X resources.
 1476 
 1477 *** Slow startup on X11R6 with X windows.
 1478 
 1479 If Emacs takes two minutes to start up on X11R6, see if your X
 1480 resources specify any Adobe fonts.  That causes the type-1 font
 1481 renderer to start up, even if the font you asked for is not a type-1
 1482 font.
 1483 
 1484 One way to avoid this problem is to eliminate the type-1 fonts from
 1485 your font path, like this:
 1486 
 1487         xset -fp /usr/X11R6/lib/X11/fonts/Type1/
 1488 
 1489 *** Pull-down menus appear in the wrong place, in the toolkit version of Emacs.
 1490 
 1491 An X resource of this form can cause the problem:
 1492 
 1493    Emacs*geometry:	80x55+0+0
 1494 
 1495 This resource is supposed to apply, and does apply, to the menus
 1496 individually as well as to Emacs frames.  If that is not what you
 1497 want, rewrite the resource.
 1498 
 1499 To check thoroughly for such resource specifications, use 'xrdb
 1500 -query' to see what resources the X server records, and also look at
 1501 the user's ~/.Xdefaults and ~/.Xdefaults-* files.
 1502 
 1503 *** Emacs running under X Window System does not handle mouse clicks.
 1504 *** 'emacs -geometry 80x20' finds a file named '80x20'.
 1505 
 1506 One cause of such problems is having (setq term-file-prefix nil) in
 1507 your .emacs file.  Another cause is a bad value of EMACSLOADPATH in
 1508 the environment.
 1509 
 1510 *** X doesn't work if DISPLAY uses a hostname.
 1511 
 1512 People have reported kernel bugs in certain systems that cause Emacs
 1513 not to work with X if DISPLAY is set using a host name.  But
 1514 the problem does not occur if DISPLAY is set to 'unix:0.0'.  I think
 1515 the bug has to do with SIGIO or FIONREAD.
 1516 
 1517 You may be able to compensate for the bug by doing (set-input-mode nil nil).
 1518 However, that has the disadvantage of turning off interrupts, so that
 1519 you are unable to quit out of a Lisp program by typing C-g.
 1520 
 1521 *** Prevent double pastes in X
 1522 
 1523 The problem:  a region, such as a command, is pasted twice when you copy
 1524 it with your mouse from GNU Emacs to an xterm or an RXVT shell in X.
 1525 The solution:  try the following in your X configuration file,
 1526 /etc/X11/xorg.conf  This should enable both PS/2 and USB mice for
 1527 single copies.  You do not need any other drivers or options.
 1528 
 1529     Section "InputDevice"
 1530             Identifier	"Generic Mouse"
 1531             Driver	"mousedev"
 1532             Option	"Device"           "/dev/input/mice"
 1533     EndSection
 1534 
 1535 *** Emacs is slow to exit in X
 1536 
 1537 After you use e.g. C-x C-c to exit, it takes many seconds before the
 1538 Emacs window disappears.  If Emacs was started from a terminal, you
 1539 see the message:
 1540 
 1541   Error saving to X clipboard manager.
 1542   If the problem persists, set 'x-select-enable-clipboard-manager' to nil.
 1543 
 1544 As the message suggests, this problem occurs when Emacs thinks you
 1545 have a clipboard manager program running, but has trouble contacting it.
 1546 If you don't want to use a clipboard manager, you can set the
 1547 suggested variable.  Or you can make Emacs not wait so long by
 1548 reducing the value of 'x-selection-timeout', either in .emacs or with
 1549 X resources.
 1550 
 1551 Sometimes this problem is due to a bug in your clipboard manager.
 1552 Updating to the latest version of the manager can help.
 1553 For example, in the Xfce 4.8 desktop environment, the clipboard
 1554 manager in versions of xfce4-settings-helper before 4.8.2 is buggy;
 1555 https://bugzilla.xfce.org/show_bug.cgi?id=7588 .
 1556 
 1557 *** Warning messages when running in Ubuntu
 1558 
 1559 When you start Emacs you may see something like this:
 1560 
 1561 (emacs:2286): LIBDBUSMENU-GTK-CRITICAL **: watch_submenu: assertion
 1562 'GTK_IS_MENU_SHELL(menu)' failed
 1563 
 1564 This happens if the Emacs binary has been renamed.  The cause is the Ubuntu
 1565 appmenu concept.  It tries to track Emacs menus and show them in the top
 1566 panel, instead of in each Emacs window.  This is not properly implemented,
 1567 so it fails for Emacs.  The order of menus is wrong, and things like copy/paste
 1568 that depend on what state Emacs is in are usually wrong (i.e. paste disabled
 1569 even if you should be able to paste, and similar).
 1570 
 1571 You can get back menus on each frame by starting emacs like this:
 1572 % env UBUNTU_MENUPROXY= emacs
 1573 
 1574 * Runtime problems on character terminals
 1575 
 1576 ** The meta key does not work on xterm.
 1577 
 1578 Typing M-x rings the terminal bell, and inserts a string like ";120~".
 1579 For recent xterm versions (>= 216), Emacs uses xterm's modifyOtherKeys
 1580 feature to generate strings for key combinations that are not
 1581 otherwise usable.  One circumstance in which this can cause problems
 1582 is if you have specified the X resource
 1583 
 1584   xterm*VT100.Translations
 1585 
 1586 to contain translations that use the meta key.  Then xterm will not
 1587 use meta in modified function-keys, which confuses Emacs.  To fix
 1588 this, you can remove the X resource or put this in your init file:
 1589 
 1590   (xterm-remove-modify-other-keys)
 1591 
 1592 ** Emacs spontaneously displays "I-search: " at the bottom of the screen.
 1593 
 1594 This means that Control-S/Control-Q (XON/XOFF) "flow control" is being
 1595 used.  C-s/C-q flow control is bad for Emacs editors because it takes
 1596 away C-s and C-q as user commands.  Since editors do not output long
 1597 streams of text without user commands, there is no need for a
 1598 user-issuable "stop output" command in an editor; therefore, a
 1599 properly designed flow control mechanism would transmit all possible
 1600 input characters without interference.  Designing such a mechanism is
 1601 easy, for a person with at least half a brain.
 1602 
 1603 There are three possible reasons why flow control could be taking place:
 1604 
 1605   1) Terminal has not been told to disable flow control
 1606   2) Insufficient padding for the terminal in use
 1607   3) Some sort of terminal concentrator or line switch is responsible
 1608 
 1609 First of all, many terminals have a set-up mode which controls whether
 1610 they generate XON/XOFF flow control characters.  This must be set to
 1611 "no XON/XOFF" in order for Emacs to work.  (For example, on a VT220
 1612 you may select "No XOFF" in the setup menu.)  Sometimes there is an
 1613 escape sequence that the computer can send to turn flow control off
 1614 and on.  If so, perhaps the termcap 'ti' string should turn flow
 1615 control off, and the 'te' string should turn it on.
 1616 
 1617 Once the terminal has been told "no flow control", you may find it
 1618 needs more padding.  The amount of padding Emacs sends is controlled
 1619 by the termcap entry for the terminal in use, and by the output baud
 1620 rate as known by the kernel.  The shell command 'stty' will print
 1621 your output baud rate; 'stty' with suitable arguments will set it if
 1622 it is wrong.  Setting to a higher speed causes increased padding.  If
 1623 the results are wrong for the correct speed, there is probably a
 1624 problem in the termcap entry.  You must speak to a local Unix wizard
 1625 to fix this.  Perhaps you are just using the wrong terminal type.
 1626 
 1627 For terminals that lack a "no flow control" mode, sometimes just
 1628 giving lots of padding will prevent actual generation of flow control
 1629 codes.  You might as well try it.
 1630 
 1631 If you are really unlucky, your terminal is connected to the computer
 1632 through a concentrator which sends XON/XOFF flow control to the
 1633 computer, or it insists on sending flow control itself no matter how
 1634 much padding you give it.  Unless you can figure out how to turn flow
 1635 control off on this concentrator (again, refer to your local wizard),
 1636 you are screwed!  You should have the terminal or concentrator
 1637 replaced with a properly designed one.  In the mean time, some drastic
 1638 measures can make Emacs semi-work.
 1639 
 1640 You can make Emacs ignore C-s and C-q and let the operating system
 1641 handle them.  To do this on a per-session basis, just type M-x
 1642 enable-flow-control RET.  You will see a message that C-\ and C-^ are
 1643 now translated to C-s and C-q.  (Use the same command M-x
 1644 enable-flow-control to turn *off* this special mode.  It toggles flow
 1645 control handling.)
 1646 
 1647 If C-\ and C-^ are inconvenient for you (for example, if one of them
 1648 is the escape character of your terminal concentrator), you can choose
 1649 other characters by setting the variables flow-control-c-s-replacement
 1650 and flow-control-c-q-replacement.  But choose carefully, since all
 1651 other control characters are already used by emacs.
 1652 
 1653 IMPORTANT: if you type C-s by accident while flow control is enabled,
 1654 Emacs output will freeze, and you will have to remember to type C-q in
 1655 order to continue.
 1656 
 1657 If you work in an environment where a majority of terminals of a
 1658 certain type are flow control hobbled, you can use the function
 1659 'enable-flow-control-on' to turn on this flow control avoidance scheme
 1660 automatically.  Here is an example:
 1661 
 1662 (enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
 1663 
 1664 If this isn't quite correct (e.g. you have a mixture of flow-control hobbled
 1665 and good vt200 terminals), you can still run enable-flow-control
 1666 manually.
 1667 
 1668 I have no intention of ever redesigning the Emacs command set for the
 1669 assumption that terminals use C-s/C-q flow control.  XON/XOFF flow
 1670 control technique is a bad design, and terminals that need it are bad
 1671 merchandise and should not be purchased.  Now that X is becoming
 1672 widespread, XON/XOFF seems to be on the way out.  If you can get some
 1673 use out of GNU Emacs on inferior terminals, more power to you, but I
 1674 will not make Emacs worse for properly designed systems for the sake
 1675 of inferior systems.
 1676 
 1677 ** Control-S and Control-Q commands are ignored completely.
 1678 
 1679 For some reason, your system is using brain-damaged C-s/C-q flow
 1680 control despite Emacs's attempts to turn it off.  Perhaps your
 1681 terminal is connected to the computer through a concentrator
 1682 that wants to use flow control.
 1683 
 1684 You should first try to tell the concentrator not to use flow control.
 1685 If you succeed in this, try making the terminal work without
 1686 flow control, as described in the preceding section.
 1687 
 1688 If that line of approach is not successful, map some other characters
 1689 into C-s and C-q using keyboard-translate-table.  The example above
 1690 shows how to do this with C-^ and C-\.
 1691 
 1692 ** Screen is updated wrong, but only on one kind of terminal.
 1693 
 1694 This could mean that the termcap entry you are using for that
 1695 terminal is wrong, or it could mean that Emacs has a bug handling
 1696 the combination of features specified for that terminal.
 1697 
 1698 The first step in tracking this down is to record what characters
 1699 Emacs is sending to the terminal.  Execute the Lisp expression
 1700 (open-termscript "./emacs-script") to make Emacs write all
 1701 terminal output into the file ~/emacs-script as well; then do
 1702 what makes the screen update wrong, and look at the file
 1703 and decode the characters using the manual for the terminal.
 1704 There are several possibilities:
 1705 
 1706 1) The characters sent are correct, according to the terminal manual.
 1707 
 1708 In this case, there is no obvious bug in Emacs, and most likely you
 1709 need more padding, or possibly the terminal manual is wrong.
 1710 
 1711 2) The characters sent are incorrect, due to an obscure aspect
 1712  of the terminal behavior not described in an obvious way by termcap.
 1713 
 1714 This case is hard.  It will be necessary to think of a way for
 1715 Emacs to distinguish between terminals with this kind of behavior
 1716 and other terminals that behave subtly differently but are
 1717 classified the same by termcap; or else find an algorithm for
 1718 Emacs to use that avoids the difference.  Such changes must be
 1719 tested on many kinds of terminals.
 1720 
 1721 3) The termcap entry is wrong.
 1722 
 1723 See the file etc/TERMS for information on changes
 1724 that are known to be needed in commonly used termcap entries
 1725 for certain terminals.
 1726 
 1727 4) The characters sent are incorrect, and clearly cannot be
 1728  right for any terminal with the termcap entry you were using.
 1729 
 1730 This is unambiguously an Emacs bug, and can probably be fixed
 1731 in termcap.c, tparam.c, term.c, scroll.c, cm.c or dispnew.c.
 1732 
 1733 ** Control-S and Control-Q commands are ignored completely on a net connection.
 1734 
 1735 Some versions of rlogin (and possibly telnet) do not pass flow
 1736 control characters to the remote system to which they connect.
 1737 On such systems, emacs on the remote system cannot disable flow
 1738 control on the local system.  Sometimes 'rlogin -8' will avoid this problem.
 1739 
 1740 One way to cure this is to disable flow control on the local host
 1741 (the one running rlogin, not the one running rlogind) using the
 1742 stty command, before starting the rlogin process.  On many systems,
 1743 "stty start u stop u" will do this.  On some systems, use
 1744 "stty -ixon" instead.
 1745 
 1746 Some versions of tcsh will prevent even this from working.  One way
 1747 around this is to start another shell before starting rlogin, and
 1748 issue the stty command to disable flow control from that shell.
 1749 
 1750 If none of these methods work, the best solution is to type
 1751 M-x enable-flow-control at the beginning of your emacs session, or
 1752 if you expect the problem to continue, add a line such as the
 1753 following to your .emacs (on the host running rlogind):
 1754 
 1755 (enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
 1756 
 1757 See the entry about spontaneous display of I-search (above) for more info.
 1758 
 1759 ** Output from Control-V is slow.
 1760 
 1761 On many bit-map terminals, scrolling operations are fairly slow.
 1762 Often the termcap entry for the type of terminal in use fails
 1763 to inform Emacs of this.  The two lines at the bottom of the screen
 1764 before a Control-V command are supposed to appear at the top after
 1765 the Control-V command.  If Emacs thinks scrolling the lines is fast,
 1766 it will scroll them to the top of the screen.
 1767 
 1768 If scrolling is slow but Emacs thinks it is fast, the usual reason is
 1769 that the termcap entry for the terminal you are using does not
 1770 specify any padding time for the 'al' and 'dl' strings.  Emacs
 1771 concludes that these operations take only as much time as it takes to
 1772 send the commands at whatever line speed you are using.  You must
 1773 fix the termcap entry to specify, for the 'al' and 'dl', as much
 1774 time as the operations really take.
 1775 
 1776 Currently Emacs thinks in terms of serial lines which send characters
 1777 at a fixed rate, so that any operation which takes time for the
 1778 terminal to execute must also be padded.  With bit-map terminals
 1779 operated across networks, often the network provides some sort of
 1780 flow control so that padding is never needed no matter how slow
 1781 an operation is.  You must still specify a padding time if you want
 1782 Emacs to realize that the operation takes a long time.  This will
 1783 cause padding characters to be sent unnecessarily, but they do
 1784 not really cost much.  They will be transmitted while the scrolling
 1785 is happening and then discarded quickly by the terminal.
 1786 
 1787 Most bit-map terminals provide commands for inserting or deleting
 1788 multiple lines at once.  Define the 'AL' and 'DL' strings in the
 1789 termcap entry to say how to do these things, and you will have
 1790 fast output without wasted padding characters.  These strings should
 1791 each contain a single %-spec saying how to send the number of lines
 1792 to be scrolled.  These %-specs are like those in the termcap
 1793 'cm' string.
 1794 
 1795 You should also define the 'IC' and 'DC' strings if your terminal
 1796 has a command to insert or delete multiple characters.  These
 1797 take the number of positions to insert or delete as an argument.
 1798 
 1799 A 'cs' string to set the scrolling region will reduce the amount
 1800 of motion you see on the screen when part of the screen is scrolled.
 1801 
 1802 ** You type Control-H (Backspace) expecting to delete characters.
 1803 
 1804 Put 'stty dec' in your .login file and your problems will disappear
 1805 after a day or two.
 1806 
 1807 The choice of Backspace for erasure was based on confusion, caused by
 1808 the fact that backspacing causes erasure (later, when you type another
 1809 character) on most display terminals.  But it is a mistake.  Deletion
 1810 of text is not the same thing as backspacing followed by failure to
 1811 overprint.  I do not wish to propagate this confusion by conforming
 1812 to it.
 1813 
 1814 For this reason, I believe 'stty dec' is the right mode to use,
 1815 and I have designed Emacs to go with that.  If there were a thousand
 1816 other control characters, I would define Control-h to delete as well;
 1817 but there are not very many other control characters, and I think
 1818 that providing the most mnemonic possible Help character is more
 1819 important than adapting to people who don't use 'stty dec'.
 1820 
 1821 If you are obstinate about confusing buggy overprinting with deletion,
 1822 you can redefine Backspace in your .emacs file:
 1823   (global-set-key "\b" 'delete-backward-char)
 1824 You can probably access  help-command  via f1.
 1825 
 1826 ** Colors are not available on a tty or in xterm.
 1827 
 1828 Emacs 21 supports colors on character terminals and terminal
 1829 emulators, but this support relies on the terminfo or termcap database
 1830 entry to specify that the display supports color.  Emacs looks at the
 1831 "Co" capability for the terminal to find out how many colors are
 1832 supported; it should be non-zero to activate the color support within
 1833 Emacs.  (Most color terminals support 8 or 16 colors.)  If your system
 1834 uses terminfo, the name of the capability equivalent to "Co" is
 1835 "colors".
 1836 
 1837 In addition to the "Co" capability, Emacs needs the "op" (for
 1838 "original pair") capability, which tells how to switch the terminal
 1839 back to the default foreground and background colors.  Emacs will not
 1840 use colors if this capability is not defined.  If your terminal entry
 1841 doesn't provide such a capability, try using the ANSI standard escape
 1842 sequence \E[00m (that is, define a new termcap/terminfo entry and make
 1843 it use your current terminal's entry plus \E[00m for the "op"
 1844 capability).
 1845 
 1846 Finally, the "NC" capability (terminfo name: "ncv") tells Emacs which
 1847 attributes cannot be used with colors.  Setting this capability
 1848 incorrectly might have the effect of disabling colors; try setting
 1849 this capability to '0' (zero) and see if that helps.
 1850 
 1851 Emacs uses the database entry for the terminal whose name is the value
 1852 of the environment variable TERM.  With 'xterm', a common terminal
 1853 entry that supports color is 'xterm-color', so setting TERM's value to
 1854 'xterm-color' might activate the color support on an xterm-compatible
 1855 emulator.
 1856 
 1857 Beginning with version 22.1, Emacs supports the --color command-line
 1858 option which may be used to force Emacs to use one of a few popular
 1859 modes for getting colors on a tty.  For example, --color=ansi8 sets up
 1860 for using the ANSI-standard escape sequences that support 8 colors.
 1861 
 1862 Some modes do not use colors unless you turn on the Font-lock mode.
 1863 Some people have long ago set their '~/.emacs' files to turn on
 1864 Font-lock on X only, so they won't see colors on a tty.  The
 1865 recommended way of turning on Font-lock is by typing "M-x
 1866 global-font-lock-mode RET" or by customizing the variable
 1867 'global-font-lock-mode'.
 1868 
 1869 ** Unexpected characters inserted into the buffer when you start Emacs.
 1870 See e.g. <URL:https://debbugs.gnu.org/11129>
 1871 
 1872 This can happen when you start Emacs in -nw mode in an Xterm.
 1873 For example, in the *scratch* buffer, you might see something like:
 1874 
 1875   0;276;0c
 1876 
 1877 This is more likely to happen if you are using Emacs over a slow
 1878 connection, and begin typing before Emacs is ready to respond.
 1879 
 1880 This occurs when Emacs tries to query the terminal to see what
 1881 capabilities it supports, and gets confused by the answer.
 1882 To avoid it, set xterm-extra-capabilities to a value other than
 1883 'check' (the default).  See that variable's documentation (in
 1884 term/xterm.el) for more details.
 1885 
 1886 * Runtime problems specific to individual Unix variants
 1887 
 1888 ** GNU/Linux
 1889 
 1890 *** GNU/Linux: profiler-report outputs nothing.
 1891 
 1892 A few versions of the Linux kernel have timer bugs that break CPU
 1893 profiling; see Bug#34235.  To fix the problem, upgrade to one of the
 1894 kernel versions 4.14.97, 4.19.19, or 4.20.6, or later.
 1895 
 1896 *** GNU/Linux: Process output is corrupted.
 1897 
 1898 There is a bug in Linux kernel 2.6.10 PTYs that can cause emacs to
 1899 read corrupted process output.
 1900 
 1901 *** GNU/Linux: Remote access to CVS with SSH causes file corruption.
 1902 
 1903 If you access a remote CVS repository via SSH, files may be corrupted
 1904 due to bad interaction between CVS, SSH, and libc.
 1905 
 1906 To fix the problem, save the following script into a file, make it
 1907 executable, and set CVS_RSH environment variable to the file name of
 1908 the script:
 1909 
 1910 #!/bin/bash
 1911 exec 2> >(exec cat >&2 2>/dev/null)
 1912 exec ssh "$@"
 1913 
 1914 *** GNU/Linux: Truncated svn annotate output with SSH.
 1915 https://debbugs.gnu.org/7791
 1916 
 1917 The symptoms are: you are accessing a svn repository over SSH.
 1918 You use vc-annotate on a large (several thousand line) file, and the
 1919 result is truncated around the 1000 line mark.  It works fine with
 1920 other access methods (e.g. http), or from outside Emacs.
 1921 
 1922 This may be a similar libc/SSH issue to the one mentioned above for CVS.
 1923 A similar workaround seems to be effective: create a script with the
 1924 same contents as the one used above for CVS_RSH, and set the SVN_SSH
 1925 environment variable to point to it.
 1926 
 1927 *** GNU/Linux: After upgrading to a newer version of Emacs,
 1928 the Meta key stops working.
 1929 
 1930 This was reported to happen on a GNU/Linux system distributed by
 1931 Mandrake.  The reason is that the previous version of Emacs was
 1932 modified by Mandrake to make the Alt key act as the Meta key, on a
 1933 keyboard where the Windows key is the one which produces the Meta
 1934 modifier.  A user who started using a newer version of Emacs, which
 1935 was not hacked by Mandrake, expected the Alt key to continue to act as
 1936 Meta, and was astonished when that didn't happen.
 1937 
 1938 The solution is to find out what key on your keyboard produces the Meta
 1939 modifier, and use that key instead.  Try all of the keys to the left
 1940 and to the right of the space bar, together with the 'x' key, and see
 1941 which combination produces "M-x" in the echo area.  You can also use
 1942 the 'xmodmap' utility to show all the keys which produce a Meta
 1943 modifier:
 1944 
 1945          xmodmap -pk | grep -Ei "meta|alt"
 1946 
 1947 A more convenient way of finding out which keys produce a Meta modifier
 1948 is to use the 'xkbprint' utility, if it's available on your system:
 1949 
 1950          xkbprint 0:0 /tmp/k.ps
 1951 
 1952 This produces a PostScript file '/tmp/k.ps' with a picture of your
 1953 keyboard; printing that file on a PostScript printer will show what
 1954 keys can serve as Meta.
 1955 
 1956 The 'xkeycaps' also shows a visual representation of the current
 1957 keyboard settings.  It also allows to modify them.
 1958 
 1959 *** GNU/Linux: slow startup on Linux-based GNU systems.
 1960 
 1961 People using systems based on the Linux kernel sometimes report that
 1962 startup takes 10 to 15 seconds longer than 'usual'.
 1963 
 1964 This is because Emacs looks up the host name when it starts.
 1965 Normally, this takes negligible time; the extra delay is due to
 1966 improper system configuration.  This problem can occur for both
 1967 networked and non-networked machines.
 1968 
 1969 Here is how to fix the configuration.  It requires being root.
 1970 
 1971 **** Networked Case.
 1972 
 1973 First, make sure the files '/etc/hosts' and '/etc/host.conf' both
 1974 exist.  The first line in the '/etc/hosts' file should look like this
 1975 (replace HOSTNAME with your host name):
 1976 
 1977     127.0.0.1      HOSTNAME
 1978 
 1979 Also make sure that the '/etc/host.conf' files contains the following
 1980 lines:
 1981 
 1982     order hosts, bind
 1983     multi on
 1984 
 1985 Any changes, permanent and temporary, to the host name should be
 1986 indicated in the '/etc/hosts' file, since it acts a limited local
 1987 database of addresses and names (e.g., some SLIP connections
 1988 dynamically allocate ip addresses).
 1989 
 1990 **** Non-Networked Case.
 1991 
 1992 The solution described in the networked case applies here as well.
 1993 However, if you never intend to network your machine, you can use a
 1994 simpler solution: create an empty '/etc/host.conf' file.  The command
 1995 'touch /etc/host.conf' suffices to create the file.  The '/etc/hosts'
 1996 file is not necessary with this approach.
 1997 
 1998 *** GNU/Linux: Emacs on a tty switches the cursor to large blinking block.
 1999 
 2000 This was reported to happen on some GNU/Linux systems which use
 2001 ncurses version 5.0, but could be relevant for other versions as well.
 2002 These versions of ncurses come with a 'linux' terminfo entry, where
 2003 the "cvvis" capability (termcap "vs") is defined as "\E[?25h\E[?8c"
 2004 (show cursor, change size).  This escape sequence switches on a
 2005 blinking hardware text-mode cursor whose size is a full character
 2006 cell.  This blinking cannot be stopped, since a hardware cursor
 2007 always blinks.
 2008 
 2009 A work-around is to redefine the "cvvis" capability so that it
 2010 enables a *software* cursor.  The software cursor works by inverting
 2011 the colors of the character at point, so what you see is a block
 2012 cursor that doesn't blink.  For this to work, you need to redefine
 2013 the "cnorm" capability as well, so that it operates on the software
 2014 cursor instead of the hardware cursor.
 2015 
 2016 To this end, run "infocmp linux > linux-term", edit the file
 2017 'linux-term' to make both the "cnorm" and "cvvis" capabilities send
 2018 the sequence "\E[?25h\E[?17;0;64c", and then run "tic linux-term" to
 2019 produce a modified terminfo entry.
 2020 
 2021 Alternatively, if you want a blinking underscore as your Emacs cursor,
 2022 set the 'visible-cursor' variable to nil in your ~/.emacs:
 2023   (setq visible-cursor nil)
 2024 
 2025 Still other way is to change the "cvvis" capability to send the
 2026 "\E[?25h\E[?0c" command.
 2027 
 2028 ** FreeBSD
 2029 
 2030 *** FreeBSD: Getting a Meta key on the console.
 2031 
 2032 By default, neither Alt nor any other key acts as a Meta key on
 2033 FreeBSD, but this can be changed using kbdcontrol(1).  Dump the
 2034 current keymap to a file with the command
 2035 
 2036   $ kbdcontrol -d >emacs.kbd
 2037 
 2038 Edit emacs.kbd, and give the key you want to be the Meta key the
 2039 definition 'meta'.  For instance, if your keyboard has a "Windows"
 2040 key with scan code 105, change the line for scan code 105 in emacs.kbd
 2041 to look like this
 2042 
 2043   105   meta   meta   meta   meta   meta   meta   meta   meta    O
 2044 
 2045 to make the Windows key the Meta key.  Load the new keymap with
 2046 
 2047   $ kbdcontrol -l emacs.kbd
 2048 
 2049 ** HP-UX
 2050 
 2051 *** HP/UX : Shell mode gives the message, "`tty`: Ambiguous".
 2052 
 2053 christos@theory.tn.cornell.edu says:
 2054 
 2055 The problem is that in your .cshrc you have something that tries to
 2056 execute 'tty'.  If you are not running the shell on a real tty then
 2057 tty will print "not a tty".  Csh expects one word in some places,
 2058 but tty is giving it back 3.
 2059 
 2060 The solution is to add a pair of quotes around `tty` to make it a single
 2061 word:
 2062 
 2063 if (`tty` == "/dev/console")
 2064 
 2065 should be changed to:
 2066 
 2067 if ("`tty`" == "/dev/console")
 2068 
 2069 Even better, move things that set up terminal sections out of .cshrc
 2070 and into .login.
 2071 
 2072 *** HP/UX: 'Pid xxx killed due to text modification or page I/O error'.
 2073 
 2074 On HP/UX, you can get that error when the Emacs executable is on an NFS
 2075 file system.  HP/UX responds this way if it tries to swap in a page and
 2076 does not get a response from the server within a timeout whose default
 2077 value is just ten seconds.
 2078 
 2079 If this happens to you, extend the timeout period.
 2080 
 2081 *** HP/UX: The right Alt key works wrong on German HP keyboards (and perhaps
 2082 other non-English HP keyboards too).
 2083 
 2084 This is because HP-UX defines the modifiers wrong in X.  Here is a
 2085 shell script to fix the problem; be sure that it is run after VUE
 2086 configures the X server.
 2087 
 2088     xmodmap 2> /dev/null - << EOF
 2089     keysym Alt_L = Meta_L
 2090     keysym Alt_R = Meta_R
 2091     EOF
 2092 
 2093     xmodmap - << EOF
 2094     clear mod1
 2095     keysym Mode_switch = NoSymbol
 2096     add mod1 = Meta_L
 2097     keysym Meta_R = Mode_switch
 2098     add mod2 = Mode_switch
 2099     EOF
 2100 
 2101 *** HP/UX: Emacs does not recognize the AltGr key.
 2102 
 2103 To fix this, set up a file ~/.dt/sessions/sessionetc with executable
 2104 rights, containing this text:
 2105 
 2106 --------------------------------
 2107 xmodmap 2> /dev/null - << EOF
 2108 keysym Alt_L = Meta_L
 2109 keysym Alt_R = Meta_R
 2110 EOF
 2111 
 2112 xmodmap - << EOF
 2113 clear mod1
 2114 keysym Mode_switch = NoSymbol
 2115 add mod1 = Meta_L
 2116 keysym Meta_R = Mode_switch
 2117 add mod2 = Mode_switch
 2118 EOF
 2119 --------------------------------
 2120 
 2121 *** HP/UX 11.0: Emacs makes HP/UX 11.0 crash.
 2122 
 2123 This is a bug in HPUX; HPUX patch PHKL_16260 is said to fix it.
 2124 
 2125 ** AIX
 2126 
 2127 *** AIX: Trouble using ptys.
 2128 
 2129 People often install the pty devices on AIX incorrectly.
 2130 Use 'smit pty' to reinstall them properly.
 2131 
 2132 *** AIXterm: Your Delete key sends a Backspace to the terminal.
 2133 
 2134 The solution is to include in your .Xdefaults the lines:
 2135 
 2136    *aixterm.Translations: #override <Key>BackSpace: string(0x7f)
 2137    aixterm*ttyModes: erase ^?
 2138 
 2139 This makes your Backspace key send DEL (ASCII 127).
 2140 
 2141 *** AIX: If linking fails because libXbsd isn't found, check if you
 2142 are compiling with the system's 'cc' and CFLAGS containing '-O5'.  If
 2143 so, you have hit a compiler bug.  Please make sure to re-configure
 2144 Emacs so that it isn't compiled with '-O5'.
 2145 
 2146 *** AIX 4.3.x or 4.4: Compiling fails.
 2147 
 2148 This could happen if you use /bin/c89 as your compiler, instead of
 2149 the default 'cc'.  /bin/c89 treats certain warnings, such as benign
 2150 redefinitions of macros, as errors, and fails the build.  A solution
 2151 is to use the default compiler 'cc'.
 2152 
 2153 *** AIX 4: Some programs fail when run in a Shell buffer
 2154 with an error message like   No terminfo entry for "unknown".
 2155 
 2156 On AIX, many terminal type definitions are not installed by default.
 2157 'unknown' is one of them.  Install the "Special Generic Terminal
 2158 Definitions" to make them defined.
 2159 
 2160 ** Solaris
 2161 
 2162 We list bugs in current versions here.  See also the section on legacy
 2163 systems.
 2164 
 2165 *** On Solaris 10, Emacs crashes during the build process.
 2166 This was reported for Emacs 25.2 on i386-pc-solaris2.10 with Sun
 2167 Studio 12 (Sun C 5.9) and with Oracle Developer Studio 12.6 (Sun C
 2168 5.15), and intermittently for sparc-sun-solaris2.10 with Oracle
 2169 Developer Studio 12.5 (Sun C 5.14).  Disabling compiler optimization
 2170 seems to fix the bug, as does upgrading the Solaris 10 operating
 2171 system to Update 11.  The cause of the bug is unknown: it may be that
 2172 Emacs's archaic memory-allocation scheme is not compatible with
 2173 slightly-older versions of Solaris and/or Oracle Studio, or it may be
 2174 something else.  Since the cause is not known, possibly the bug is
 2175 still present in newer versions of Emacs, Oracle Studio, and/or
 2176 Solaris.  See Bug#26638.
 2177 
 2178 *** On Solaris, C-x doesn't get through to Emacs when you use the console.
 2179 
 2180 This is a Solaris feature (at least on Intel x86 cpus).  Type C-r
 2181 C-r C-t, to toggle whether C-x gets through to Emacs.
 2182 
 2183 *** Problem with remote X server on Suns.
 2184 
 2185 On a Sun, running Emacs on one machine with the X server on another
 2186 may not work if you have used the unshared system libraries.  This
 2187 is because the unshared libraries fail to use YP for host name lookup.
 2188 As a result, the host name you specify may not be recognized.
 2189 
 2190 *** Solaris 2.6: Emacs crashes with SIGBUS or SIGSEGV on Solaris after you delete a frame.
 2191 
 2192 We suspect that this is a bug in the X libraries provided by
 2193 Sun.  There is a report that one of these patches fixes the bug and
 2194 makes the problem stop:
 2195 
 2196 105216-01 105393-01 105518-01 105621-01 105665-01 105615-02 105216-02
 2197 105667-01 105401-08 105615-03 105621-02 105686-02 105736-01 105755-03
 2198 106033-01 105379-01 105786-01 105181-04 105379-03 105786-04 105845-01
 2199 105284-05 105669-02 105837-01 105837-02 105558-01 106125-02 105407-01
 2200 
 2201 Another person using a newer system (kernel patch level Generic_105181-06)
 2202 suspects that the bug was fixed by one of these more recent patches:
 2203 
 2204 106040-07  SunOS 5.6: X Input & Output Method patch
 2205 106222-01  OpenWindows 3.6: filemgr (ff.core) fixes
 2206 105284-12  Motif 1.2.7: sparc Runtime library patch
 2207 
 2208 *** Solaris 7 or 8: Emacs reports a BadAtom error (from X)
 2209 
 2210 This happens when Emacs was built on some other version of Solaris.
 2211 Rebuild it on Solaris 8.
 2212 
 2213 *** When using M-x dbx with the SparcWorks debugger, the 'up' and 'down'
 2214 commands do not move the arrow in Emacs.
 2215 
 2216 You can fix this by adding the following line to '~/.dbxinit':
 2217 
 2218  dbxenv output_short_file_name off
 2219 
 2220 *** On Solaris, CTRL-t is ignored by Emacs when you use
 2221 the fr.ISO-8859-15 locale (and maybe other related locales).
 2222 
 2223 You can fix this by editing the file:
 2224 
 2225         /usr/openwin/lib/locale/iso8859-15/Compose
 2226 
 2227 Near the bottom there is a line that reads:
 2228 
 2229         Ctrl<t> <quotedbl> <Y>                  : "\276"        threequarters
 2230 
 2231 while it should read:
 2232 
 2233         Ctrl<T> <quotedbl> <Y>                  : "\276"        threequarters
 2234 
 2235 Note the lower case <t>.  Changing this line should make C-t work.
 2236 
 2237 *** On Solaris, Emacs fails to set menu-bar-update-hook on startup, with error
 2238 "Error in menu-bar-update-hook: (error Point before start of properties)".
 2239 This seems to be a GCC optimization bug that occurs for GCC 4.1.2 (-g
 2240 and -g -O2) and GCC 4.2.3 (-g -O and -g -O2).  You can fix this by
 2241 compiling with GCC 4.2.3 or CC 5.7, with no optimizations.
 2242 
 2243 * Runtime problems specific to MS-Windows
 2244 
 2245 ** Emacs on Windows 9X requires UNICOWS.DLL
 2246 
 2247 If that DLL is not available, Emacs will display an error dialog
 2248 stating its absence, and refuse to run.
 2249 
 2250 This is because Emacs 24.4 and later uses functions whose non-stub
 2251 implementation is only available in UNICOWS.DLL, which implements the
 2252 Microsoft Layer for Unicode on Windows 9X, or "MSLU".  This article on
 2253 MSDN:
 2254 
 2255   http://msdn.microsoft.com/en-us/goglobal/bb688166.aspx
 2256 
 2257 includes a short description of MSLU and a link where it can be
 2258 downloaded.
 2259 
 2260 ** Emacs refuses to start on Windows 9X because ctime64 function is missing
 2261 
 2262 This is a sign that Emacs was compiled with MinGW runtime version
 2263 4.0.x or later.  These versions of runtime call in their startup code
 2264 the ctime64 function, which does not exist in MSVCRT.DLL, the C
 2265 runtime shared library, distributed with Windows 9X.
 2266 
 2267 A workaround is to build Emacs with MinGW runtime 3.x (the latest
 2268 version is 3.20).
 2269 
 2270 ** addpm fails to run on Windows NT4, complaining about Shell32.dll
 2271 
 2272 This is likely to happen because Shell32.dll shipped with NT4 lacks
 2273 the updates required by Emacs.  Installing Internet Explorer 4 solves
 2274 the problem.  Note that it is NOT enough to install IE6, because doing
 2275 so will not install the Shell32.dll update.
 2276 
 2277 ** A few seconds delay is seen at startup and for many file operations
 2278 
 2279 This happens when the Net Logon service is enabled.  During Emacs
 2280 startup, this service issues many DNS requests looking up for the
 2281 Windows Domain Controller.  When Emacs accesses files on networked
 2282 drives, it automatically logs on the user into those drives, which
 2283 again causes delays when Net Logon is running.
 2284 
 2285 The solution seems to be to disable Net Logon with this command typed
 2286 at the Windows shell prompt:
 2287 
 2288   net stop netlogon
 2289 
 2290 To start the service again, type "net start netlogon".  (You can also
 2291 stop and start the service from the Computer Management application,
 2292 accessible by right-clicking "My Computer" or "Computer", selecting
 2293 "Manage", then clicking on "Services".)
 2294 
 2295 ** Emacs crashes when exiting the Emacs session
 2296 
 2297 This was reported to happen when some optional DLLs, such as those
 2298 used for displaying images or the GnuTLS library or zlib compression
 2299 library, which are loaded on-demand, have a runtime dependency on the
 2300 libgcc DLL, libgcc_s_dw2-1.dll.  The reason seems to be a bug in
 2301 libgcc which rears its ugly head whenever the libgcc DLL is loaded
 2302 after Emacs has started.
 2303 
 2304 One solution for this problem is to find an alternative build of the
 2305 same optional library that does not depend on the libgcc DLL.
 2306 
 2307 Another possibility is to rebuild Emacs with the -shared-libgcc
 2308 switch, which will force Emacs to load libgcc_s_dw2-1.dll on startup,
 2309 ahead of any optional DLLs loaded on-demand later in the session.
 2310 
 2311 ** File selection dialog opens in incorrect directories
 2312 
 2313 Invoking the file selection dialog on Windows 7 or later shows a
 2314 directory that is different from what was passed to 'read-file-name'
 2315 or 'x-file-dialog' via their arguments.
 2316 
 2317 This is due to a deliberate change in behavior of the file selection
 2318 dialogs introduced in Windows 7.  It is explicitly described in the
 2319 MSDN documentation of the GetOpenFileName API used by Emacs to pop up
 2320 the file selection dialog.  For the details, see
 2321 
 2322   http://msdn.microsoft.com/en-us/library/windows/desktop/ms646839%28v=vs.85%29.aspx
 2323 
 2324 The dialog shows the last directory in which the user selected a file
 2325 in a previous invocation of the dialog with the same initial
 2326 directory.
 2327 
 2328 You can reset this "memory" of that directory by invoking the file
 2329 selection dialog with a different initial directory.
 2330 
 2331 ** PATH can contain unexpanded environment variables
 2332 
 2333 Old releases of TCC (version 9) and 4NT (up to version 8) do not correctly
 2334 expand App Paths entries of type REG_EXPAND_SZ.  When Emacs is run from TCC
 2335 and such an entry exists for emacs.exe, exec-path will contain the
 2336 unexpanded entry.  This has been fixed in TCC 10.  For more information,
 2337 see bug#2062.
 2338 
 2339 ** Setting w32-pass-rwindow-to-system and w32-pass-lwindow-to-system to nil
 2340 does not prevent the Start menu from popping up when the left or right
 2341 "Windows" key is pressed.
 2342 
 2343 This was reported to happen when XKeymacs is installed.  At least with
 2344 XKeymacs Version 3.47, deactivating XKeymacs when Emacs is active is
 2345 not enough to avoid its messing with the keyboard input.  Exiting
 2346 XKeymacs completely is reported to solve the problem.
 2347 
 2348 ** Pasting from Windows clipboard into Emacs doesn't work.
 2349 
 2350 This was reported to be the result of an anti-virus software blocking
 2351 the clipboard-related operations when a Web browser is open, for
 2352 security reasons.  The solution is to close the Web browser while
 2353 working in Emacs, or to add emacs.exe to the list of applications that
 2354 are allowed to use the clipboard when the Web browser is open.
 2355 
 2356 ** "Pinning" Emacs to the taskbar doesn't work on Windows 10
 2357 
 2358 "Doesn't work" here means that if you invoke Emacs by clicking on the
 2359 pinned icon, a separate button appears on the taskbar, instead of the
 2360 expected effect of the icon you clicked on being converted to that
 2361 button.
 2362 
 2363 This is due to a bug in early versions of Windows 10, reportedly fixed
 2364 in build 1511 of Windows 10 (a.k.a. "Windows 10 SP1").  If you cannot
 2365 upgrade, read the work-around described below.
 2366 
 2367 First, be sure to edit the Properties of the pinned icon to invoke
 2368 runemacs.exe, not emacs.exe.  (The latter will cause an extra cmd
 2369 window to appear when you invoke Emacs from the pinned icon.)
 2370 
 2371 But the real cause of the problem is the fact that the pinned icon
 2372 (which is really a shortcut in a special directory) lacks a unique
 2373 application-defined Application User Model ID (AppUserModelID) that
 2374 identifies the current process to the taskbar.  This identifier allows
 2375 an application to group its associated processes and windows under a
 2376 single taskbar button.  Emacs on Windows specifies a unique
 2377 AppUserModelID when it starts, but Windows 10, unlike previous
 2378 versions of MS-Windows, does not propagate that ID to the pinned icon.
 2379 
 2380 To work around this, use some utility, such as 'win7appid', to set the
 2381 AppUserModelID of the pinned icon to the string "Gnu.Emacs".  The
 2382 shortcut files corresponding to icons you pinned are stored by Windows
 2383 in the following subdirectory of your user's directory (by default
 2384 C:\Users\<UserName>\):
 2385 
 2386  AppData\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar
 2387 
 2388 Look for the file 'emacs.lnk' there.
 2389 
 2390 ** Windows 95 and networking.
 2391 
 2392 To support server sockets, Emacs loads ws2_32.dll.  If this file is
 2393 missing, all Emacs networking features are disabled.
 2394 
 2395 Old versions of Windows 95 may not have the required DLL.  To use
 2396 Emacs's networking features on Windows 95, you must install the
 2397 "Windows Socket 2" update available from MicroSoft's support Web.
 2398 
 2399 ** Emacs exits with "X protocol error" when run with an X server for MS-Windows.
 2400 
 2401 A certain X server for Windows had a bug which caused this.
 2402 Supposedly the newer 32-bit version of this server doesn't have the
 2403 problem.
 2404 
 2405 ** Emacs crashes when opening a file with a UNC path and rails-mode is loaded.
 2406 
 2407 Loading rails-mode seems to interfere with UNC path handling.  This has been
 2408 reported as a bug against both Emacs and rails-mode, so look for an updated
 2409 rails-mode that avoids this crash, or avoid using UNC paths if using
 2410 rails-mode.
 2411 
 2412 ** M-x term does not work on MS-Windows.
 2413 
 2414 TTY emulation on Windows is undocumented, and programs such as stty
 2415 which are used on POSIX platforms to control tty emulation do not
 2416 exist for native windows terminals.
 2417 
 2418 ** Using create-fontset-from-ascii-font or the --font startup parameter
 2419 with a Chinese, Japanese or Korean font leads to display problems.
 2420 Use a Latin-only font as your default font.  If you want control over
 2421 which font is used to display Chinese, Japanese or Korean character,
 2422 use create-fontset-from-fontset-spec to define a fontset.
 2423 
 2424 ** Frames are not refreshed while dialogs or menus are displayed
 2425 
 2426 This means no redisplay while the File or Font dialog or a pop-up menu
 2427 is displayed.  This also means tooltips with help text for pop-up
 2428 menus are not displayed at all (except in a TTY session, where the help
 2429 text is shown in the echo area).  This is because message handling
 2430 under Windows is synchronous, so we cannot handle repaint (or any
 2431 other) messages while waiting for a system function, which popped up
 2432 the menu/dialog, to return the result of the dialog or pop-up menu
 2433 interaction.
 2434 
 2435 ** Help text in tooltips does not work on old Windows versions
 2436 
 2437 Windows 95 and Windows NT up to version 4.0 do not support help text
 2438 for menus.  Help text is only available in later versions of Windows.
 2439 
 2440 ** Display problems with ClearType method of smoothing
 2441 
 2442 When "ClearType" method is selected as the "method to smooth edges of
 2443 screen fonts" (in Display Properties, Appearance tab, under
 2444 "Effects"), there are various problems related to display of
 2445 characters:  Bold fonts can be hard to read, small portions of some
 2446 characters could appear chopped, etc.  This happens because, under
 2447 ClearType, characters are drawn outside their advertised bounding box.
 2448 Emacs 21 disabled the use of ClearType, whereas Emacs 22 allows it and
 2449 has some code to enlarge the width of the bounding box.  Apparently,
 2450 this display feature needs more changes to get it 100% right.  A
 2451 workaround is to disable ClearType.
 2452 
 2453 ** Cursor is displayed as a thin vertical bar and cannot be changed
 2454 
 2455 This is known to happen if the Windows Magnifier is turned on before
 2456 the Emacs session starts.  The Magnifier affects the cursor shape and
 2457 prevents any changes to it by setting the 'cursor-type' variable or
 2458 frame parameter.
 2459 
 2460 The solution is to log off and on again, and then start the Emacs
 2461 session only after turning the Magnifier off.
 2462 
 2463 To turn the Windows Magnifier off, click "Start->All Programs", or
 2464 "All Apps", depending on your Windows version, then select
 2465 "Accessibility" and click "Magnifier".  In the Magnifier Settings
 2466 dialog that opens, click "Exit".
 2467 
 2468 ** Problems with mouse-tracking and focus management
 2469 
 2470 There are problems with display if mouse-tracking is enabled and the
 2471 mouse is moved off a frame, over another frame then back over the first
 2472 frame.  A workaround is to click the left mouse button inside the frame
 2473 after moving back into it.
 2474 
 2475 Some minor flickering still persists during mouse-tracking, although
 2476 not as severely as in 21.1.
 2477 
 2478 An inactive cursor remains in an active window after the Windows
 2479 Manager driven switch of the focus, until a key is pressed.
 2480 
 2481 ** Problems with Windows input methods
 2482 
 2483 Some of the Windows input methods cause the keyboard to send
 2484 characters encoded in the appropriate coding system (e.g., ISO 8859-1
 2485 for Latin-1 characters, ISO 8859-8 for Hebrew characters, etc.).  To
 2486 make these input methods work with Emacs on Windows 9X, you might need
 2487 to set the keyboard coding system to the appropriate value after you
 2488 activate the Windows input method.  For example, if you activate the
 2489 Hebrew input method, type this:
 2490 
 2491    C-x RET k hebrew-iso-8bit RET
 2492 
 2493 In addition, to use these Windows input methods, you might need to set
 2494 your "Language for non-Unicode programs" (on Windows XP, this is on
 2495 the Advanced tab of Regional Settings) to the language of the input
 2496 method.
 2497 
 2498 To bind keys that produce non-ASCII characters with modifiers, you
 2499 must specify raw byte codes.  For instance, if you want to bind
 2500 META-a-grave to a command, you need to specify this in your '~/.emacs':
 2501 
 2502   (global-set-key [?\M-\340] ...)
 2503 
 2504 The above example is for the Latin-1 environment where the byte code
 2505 of the encoded a-grave is 340 octal.  For other environments, use the
 2506 encoding appropriate to that environment.
 2507 
 2508 ** Problems with the %b format specifier for format-time-string
 2509 
 2510 The %b specifier for format-time-string does not produce abbreviated
 2511 month names with consistent widths for some locales on some versions
 2512 of Windows.  This is caused by a deficiency in the underlying system
 2513 library function.
 2514 
 2515 ** Non-US time zones.
 2516 
 2517 Many non-US time zones are implemented incorrectly.  This is due to
 2518 over-simplistic handling of daylight savings switchovers by the
 2519 Windows libraries.
 2520 
 2521 ** Files larger than 4GB report wrong size in a 32-bit Windows build
 2522 
 2523 Files larger than 4GB cause overflow in the size (represented as a
 2524 32-bit integer) reported by 'file-attributes'.  This affects Dired as
 2525 well, since the Windows port uses a Lisp emulation of 'ls', which relies
 2526 on 'file-attributes'.
 2527 
 2528 ** Playing sound doesn't support the :data method
 2529 
 2530 Sound playing is not supported with the ':data DATA' key-value pair.
 2531 You _must_ use the ':file FILE' method.
 2532 
 2533 ** Typing Alt-Shift has strange effects on MS-Windows.
 2534 
 2535 This combination of keys is a command to change keyboard layout.  If
 2536 you proceed to type another non-modifier key before you let go of Alt
 2537 and Shift, the Alt and Shift act as modifiers in the usual way.  A
 2538 more permanent work around is to change it to another key combination,
 2539 or disable it in the "Regional and Language Options" applet of the
 2540 Control Panel.  (The exact sequence of mouse clicks in the "Regional
 2541 and Language Options" applet needed to find the key combination that
 2542 changes the keyboard layout depends on your Windows version; for XP,
 2543 in the Languages tab, click "Details" and then "Key Settings".)
 2544 
 2545 ** Interrupting Cygwin port of Bash from Emacs doesn't work.
 2546 
 2547 Cygwin 1.x builds of the ported Bash cannot be interrupted from the
 2548 MS-Windows version of Emacs.  This is due to some change in the Bash
 2549 port or in the Cygwin library which apparently make Bash ignore the
 2550 keyboard interrupt event sent by Emacs to Bash.  (Older Cygwin ports
 2551 of Bash, up to b20.1, did receive SIGINT from Emacs.)
 2552 
 2553 ** Accessing remote files with ange-ftp hangs the MS-Windows version of Emacs.
 2554 
 2555 If the FTP client is the Cygwin port of GNU 'ftp', this appears to be
 2556 due to some bug in the Cygwin DLL or some incompatibility between it
 2557 and the implementation of asynchronous subprocesses in the Windows
 2558 port of Emacs.  Specifically, some parts of the FTP server responses
 2559 are not flushed out, apparently due to buffering issues, which
 2560 confuses ange-ftp.
 2561 
 2562 The solution is to downgrade to an older version of the Cygwin DLL
 2563 (version 1.3.2 was reported to solve the problem), or use the stock
 2564 Windows FTP client, usually found in the 'C:\WINDOWS' or 'C:\WINNT'
 2565 directory.  To force ange-ftp use the stock Windows client, set the
 2566 variable 'ange-ftp-ftp-program-name' to the absolute file name of the
 2567 client's executable.  For example:
 2568 
 2569  (setq ange-ftp-ftp-program-name "c:/windows/ftp.exe")
 2570 
 2571 If you want to stick with the Cygwin FTP client, you can work around
 2572 this problem by putting this in your '.emacs' file:
 2573 
 2574  (setq ange-ftp-ftp-program-args '("-i" "-n" "-g" "-v" "--prompt" "")
 2575 
 2576 ** lpr commands don't work on MS-Windows with some cheap printers.
 2577 
 2578 This problem may also strike other platforms, but the solution is
 2579 likely to be a global one, and not Emacs specific.
 2580 
 2581 Many cheap inkjet, and even some cheap laser printers, do not
 2582 print plain text anymore, they will only print through graphical
 2583 printer drivers.  A workaround on MS-Windows is to use Windows's basic
 2584 built in editor to print (this is possibly the only useful purpose it
 2585 has):
 2586 
 2587 (setq printer-name "")         ; notepad takes the default
 2588 (setq lpr-command "notepad")   ; notepad
 2589 (setq lpr-switches nil)        ; not needed
 2590 (setq lpr-printer-switch "/P") ; run notepad as batch printer
 2591 
 2592 ** Antivirus software interacts badly with the MS-Windows version of Emacs.
 2593 
 2594 The usual manifestation of these problems is that subprocesses don't
 2595 work or even wedge the entire system.  In particular, "M-x shell RET"
 2596 was reported to fail to work.  But other commands also sometimes don't
 2597 work when an antivirus package is installed.
 2598 
 2599 The solution is to switch the antivirus software to a less aggressive
 2600 mode (e.g., disable the "auto-protect" feature), or even uninstall
 2601 or disable it entirely.
 2602 
 2603 ** Pressing the mouse button on MS-Windows does not give a mouse-2 event.
 2604 
 2605 This is usually a problem with the mouse driver.  Because most Windows
 2606 programs do not do anything useful with the middle mouse button, many
 2607 mouse drivers allow you to define the wheel press to do something
 2608 different.  Some drivers do not even have the option to generate a
 2609 middle button press.  In such cases, setting the wheel press to
 2610 "scroll" sometimes works if you press the button twice.  Trying a
 2611 generic mouse driver might help.
 2612 
 2613 One particular situation where this happens is when you have
 2614 "Microsoft Intellipoint" installed, which runs the program
 2615 ipoint.exe.  The fix is reportedly to uninstall this software.
 2616 
 2617 ** Scrolling the mouse wheel on MS-Windows always scrolls the top window.
 2618 
 2619 This is another common problem with mouse drivers.  Instead of
 2620 generating scroll events, some mouse drivers try to fake scroll bar
 2621 movement.  But they are not intelligent enough to handle multiple
 2622 scroll bars within a frame.  Trying a generic mouse driver might help.
 2623 
 2624 ** Mail sent through Microsoft Exchange in some encodings appears to be
 2625 mangled and is not seen correctly in Rmail or Gnus.  We don't know
 2626 exactly what happens, but it isn't an Emacs problem in cases we've
 2627 seen.
 2628 
 2629 ** On MS-Windows, you cannot use the right-hand ALT key and the left-hand
 2630 CTRL key together to type a Control-Meta character.
 2631 
 2632 This is a consequence of a misfeature beyond Emacs's control.
 2633 
 2634 Under Windows, the AltGr key on international keyboards generates key
 2635 events with the modifiers Right-Alt and Left-Ctrl.  Since Emacs cannot
 2636 distinguish AltGr from an explicit Right-Alt and Left-Ctrl
 2637 combination, whenever it sees Right-Alt and Left-Ctrl it assumes that
 2638 AltGr has been pressed.  The variable 'w32-recognize-altgr' can be set
 2639 to nil to tell Emacs that AltGr is really Ctrl and Alt.
 2640 
 2641 ** Under some X-servers running on MS-Windows, Emacs's display is incorrect.
 2642 
 2643 The symptoms are that Emacs does not completely erase blank areas of the
 2644 screen during scrolling or some other screen operations (e.g., selective
 2645 display or when killing a region).  M-x recenter will cause the screen
 2646 to be completely redisplayed and the "extra" characters will disappear.
 2647 
 2648 This is known to occur under Exceed 6, and possibly earlier versions
 2649 as well; it is reportedly solved in version 6.2.0.16 and later.  The
 2650 problem lies in the X-server settings.
 2651 
 2652 There are reports that you can solve the problem with Exceed by
 2653 running 'Xconfig' from within NT, choosing "X selection", then
 2654 un-checking the boxes "auto-copy X selection" and "auto-paste to X
 2655 selection".
 2656 
 2657 If this does not work, please inform bug-gnu-emacs@gnu.org.  Then
 2658 please call support for your X-server and see if you can get a fix.
 2659 If you do, please send it to bug-gnu-emacs@gnu.org so we can list it here.
 2660 
 2661 
 2662 * Runtime problems specific to macOS
 2663 
 2664 ** macOS doesn't come with libxpm, so only XPM3 is supported.
 2665 
 2666 Libxpm is available for macOS as part of the XQuartz project.
 2667 
 2668 ** The color list can become corrupt.
 2669 
 2670 This can be seen when Emacs is run from the command line and produces
 2671 output containing the text:
 2672 
 2673     non-keyed archive cannot be decoded by NSKeyedUnarchiver
 2674 
 2675 The solution is to delete '$HOME/Library/Colors/Emacs.clr'.
 2676 
 2677 
 2678 * Build-time problems
 2679 
 2680 ** Configuration
 2681 
 2682 *** 'configure' warns "accepted by the compiler, rejected by the preprocessor".
 2683 
 2684 This indicates a mismatch between the C compiler and preprocessor that
 2685 configure is using.  For example, on Solaris 10 trying to use
 2686 CC=/opt/SUNWspro/bin/cc (the Sun Studio compiler) together with
 2687 CPP=/usr/ccs/lib/cpp can result in errors of this form (you may also
 2688 see the error '"/usr/include/sys/isa_defs.h", line 500: undefined control').
 2689 
 2690 The solution is to tell configure to use the correct C preprocessor
 2691 for your C compiler (CPP="/opt/SUNWspro/bin/cc -E" in the above
 2692 example).
 2693 
 2694 ** Compilation
 2695 
 2696 *** Building Emacs over NFS fails with "Text file busy".
 2697 
 2698 This was reported to happen when building Emacs on a GNU/Linux system
 2699 (Red Hat Linux 6.2) using a build directory automounted from Solaris
 2700 (SunOS 5.6) file server, but it might not be limited to that
 2701 configuration alone.  Presumably, the NFS server doesn't commit the
 2702 files' data to disk quickly enough, and the Emacs executable file is
 2703 left "busy" for several seconds after Emacs has finished dumping
 2704 itself.  This causes the subsequent commands which invoke the dumped
 2705 Emacs executable to fail with the above message.
 2706 
 2707 In some of these cases, a time skew between the NFS server and the
 2708 machine where Emacs is built is detected and reported by GNU Make
 2709 (it says that some of the files have modification time in the future).
 2710 This might be a symptom of NFS-related problems.
 2711 
 2712 If the NFS server runs on Solaris, apply the Solaris patch 105379-05
 2713 (Sunos 5.6: /kernel/misc/nfssrv patch).  If that doesn't work, or if
 2714 you have a different version of the OS or the NFS server, you can
 2715 force the NFS server to use 1KB blocks, which was reported to fix the
 2716 problem albeit at a price of slowing down file I/O.  You can force 1KB
 2717 blocks by specifying the "-o  rsize=1024,wsize=1024" options to the
 2718 'mount' command, or by adding ",rsize=1024,wsize=1024" to the mount
 2719 options in the appropriate system configuration file, such as
 2720 '/etc/auto.home'.
 2721 
 2722 Alternatively, when Make fails due to this problem, you could wait for
 2723 a few seconds and then invoke Make again.  In one particular case,
 2724 waiting for 10 or more seconds between the two Make invocations seemed
 2725 to work around the problem.
 2726 
 2727 Similar problems can happen if your machine NFS-mounts a directory
 2728 onto itself.  Suppose the Emacs sources live in '/usr/local/src' and
 2729 you are working on the host called 'marvin'.  Then an entry in the
 2730 '/etc/fstab' file like the following is asking for trouble:
 2731 
 2732     marvin:/usr/local/src /usr/local/src ...options.omitted...
 2733 
 2734 The solution is to remove this line from '/etc/fstab'.
 2735 
 2736 *** Building a 32-bit executable on a 64-bit GNU/Linux architecture.
 2737 
 2738 First ensure that the necessary 32-bit system libraries and include
 2739 files are installed.  Then use:
 2740 
 2741   env CC="gcc -m32" ./configure --build=i386-linux-gnu --x-libraries=/usr/lib
 2742 
 2743 (using the location of the 32-bit X libraries on your system).
 2744 
 2745 *** Building on FreeBSD 11 fails at link time due to unresolved symbol
 2746 
 2747 The symbol is sendmmsg@FBSD_1.4.  This is due to a faulty libgio
 2748 library on these systems.  The solution is to reconfigure Emacs while
 2749 disabling all the features that require libgio: rsvg, dbus, gconf, and
 2750 imagemagick.
 2751 
 2752 *** Building Emacs for Cygwin can fail with GCC 3
 2753 
 2754 As of Emacs 22.1, there have been stability problems with Cygwin
 2755 builds of Emacs using GCC 3.  Cygwin users are advised to use GCC 4.
 2756 
 2757 *** Building Emacs 23.3 and later will fail under Cygwin 1.5.19
 2758 
 2759 This is a consequence of a change to src/dired.c on 2010-07-27.  The
 2760 issue is that Cygwin 1.5.19 did not have d_ino in 'struct dirent'.
 2761 See
 2762 
 2763   https://lists.gnu.org/r/emacs-devel/2010-07/msg01266.html
 2764 
 2765 *** Building the native MS-Windows port fails due to unresolved externals
 2766 
 2767 The linker error messages look like this:
 2768 
 2769  oo-spd/i386/ctags.o:ctags.c:(.text+0x156e): undefined reference to `_imp__re_set_syntax'
 2770  collect2: ld returned 1 exit status
 2771 
 2772 This happens because GCC finds an incompatible regex.h header
 2773 somewhere on the include path, before the version of regex.h supplied
 2774 with Emacs.  One such incompatible version of regex.h is part of the
 2775 GnuWin32 Regex package.
 2776 
 2777 The solution is to remove the incompatible regex.h from the include
 2778 path, when compiling Emacs.  Alternatively, re-run the configure.bat
 2779 script with the "-isystem C:/GnuWin32/include" switch (adapt for your
 2780 system's place where you keep the GnuWin32 include files) -- this will
 2781 cause the compiler to search headers in the directories specified by
 2782 the Emacs Makefile _before_ it looks in the GnuWin32 include
 2783 directories.
 2784 
 2785 *** Building the native MS-Windows port with Cygwin GCC can fail.
 2786 
 2787 Emacs may not build using some Cygwin builds of GCC, such as Cygwin
 2788 version 1.1.8, using the default configure settings.  It appears to be
 2789 necessary to specify the -mwin32 flag when compiling, and define
 2790 __MSVCRT__, like so:
 2791 
 2792   configure --with-gcc --cflags -mwin32 --cflags -D__MSVCRT__
 2793 
 2794 *** Building the MS-Windows port fails with a CreateProcess failure.
 2795 
 2796 Some versions of mingw32 make on some versions of Windows do not seem
 2797 to detect the shell correctly.  Try "make SHELL=cmd.exe", or if that
 2798 fails, try running make from Cygwin bash instead.
 2799 
 2800 *** Building 'ctags' for MS-Windows with the MinGW port of GCC fails.
 2801 
 2802 This might happen due to a bug in the MinGW header assert.h, which
 2803 defines the 'assert' macro with a trailing semi-colon.  The following
 2804 patch to assert.h should solve this:
 2805 
 2806  *** include/assert.h.orig	Sun Nov  7 02:41:36 1999
 2807  --- include/assert.h	Mon Jan 29 11:49:10 2001
 2808  ***************
 2809  *** 41,47 ****
 2810    /*
 2811     * If not debugging, assert does nothing.
 2812     */
 2813  ! #define assert(x)	((void)0);
 2814 
 2815    #else /* debugging enabled */
 2816 
 2817  --- 41,47 ----
 2818    /*
 2819     * If not debugging, assert does nothing.
 2820     */
 2821  ! #define assert(x)	((void)0)
 2822 
 2823    #else /* debugging enabled */
 2824 
 2825 
 2826 *** Building the MS-Windows port with Visual Studio 2005 fails.
 2827 
 2828 Microsoft no longer ships the single threaded version of the C library
 2829 with their compiler, and the multithreaded static library is missing
 2830 some functions that Microsoft have deemed non-threadsafe.  The
 2831 dynamically linked C library has all the functions, but there is a
 2832 conflict between the versions of malloc in the DLL and in Emacs, which
 2833 is not resolvable due to the way Windows does dynamic linking.
 2834 
 2835 We recommend the use of the MinGW port of GCC for compiling Emacs, as
 2836 not only does it not suffer these problems, but it is also Free
 2837 software like Emacs.
 2838 
 2839 *** Building the MS-Windows port with Visual Studio fails compiling emacs.rc
 2840 
 2841 If the build fails with the following message then the problem
 2842 described here most likely applies:
 2843 
 2844 ../nt/emacs.rc(1) : error RC2176 : old DIB in icons\emacs.ico; pass it
 2845 through SDKPAINT
 2846 
 2847 The Emacs icon contains a high resolution PNG icon for Vista, which is
 2848 not recognized by older versions of the resource compiler.  There are
 2849 several workarounds for this problem:
 2850 	1. Use Free MinGW tools to compile, which do not have this problem.
 2851 	2. Install the latest Windows SDK.
 2852 	3. Replace emacs.ico with an older or edited icon.
 2853 
 2854 *** Building the MS-Windows port complains about unknown escape sequences.
 2855 
 2856 Errors and warnings can look like this:
 2857 
 2858  w32.c:1959:27: error: \x used with no following hex digits
 2859  w32.c:1959:27: warning: unknown escape sequence '\i'
 2860 
 2861 This happens when paths using backslashes are passed to the compiler or
 2862 linker (via -I and possibly other compiler flags); when these paths are
 2863 included in source code, the backslashes are interpreted as escape sequences.
 2864 See https://lists.gnu.org/r/emacs-devel/2010-07/msg00995.html
 2865 
 2866 The fix is to use forward slashes in all paths passed to the compiler.
 2867 
 2868 ** Linking
 2869 
 2870 *** Building Emacs with a system compiler fails to link because of an
 2871 undefined symbol such as __eprintf which does not appear in Emacs.
 2872 
 2873 This can happen if some of the libraries linked into Emacs were built
 2874 with GCC, but Emacs itself is being linked with a compiler other than
 2875 GCC.  Object files compiled with GCC might need some helper functions
 2876 from libgcc.a, the library which comes with GCC, but the system
 2877 compiler does not instruct the linker to search libgcc.a during the
 2878 link stage.
 2879 
 2880 A solution is to link with GCC, like this:
 2881 
 2882         make CC=gcc
 2883 
 2884 Since the .o object files already exist, this will not recompile Emacs
 2885 with GCC, but just restart by trying again to link temacs.
 2886 
 2887 *** Building Emacs with -lcurses fails with undefined symbols like BC.
 2888 
 2889 The 'configure' script attempts to use several terminal libraries,
 2890 including tinfo, ncurses, and terminfo, and curses (in that order).
 2891 If it happens to choose the long-obsolete curses library, Emacs will
 2892 not link correctly.  Emacs 28 is expected to work around this problem;
 2893 in the meantime you can work around it by installing tinfo, ncurses or
 2894 terminfo instead.
 2895 
 2896 This problem can happen on AIX 7.2 if you build with IBM's compiler XLC,
 2897 as AIX's ncurses library suffers from the libgcc problem mentioned above.
 2898 To work around this, configure and build with GCC.
 2899 
 2900 *** Sun with acc: Link failure when using acc on a Sun.
 2901 
 2902 To use acc, you need additional options just before the libraries, such as
 2903 
 2904    /usr/lang/SC2.0.1/values-Xt.o -L/usr/lang/SC2.0.1/cg87 -L/usr/lang/SC2.0.1
 2905 
 2906 and you need to add -lansi just before -lc.
 2907 
 2908 The precise file names depend on the compiler version, so we
 2909 cannot easily arrange to supply them.
 2910 
 2911 *** 'tparam' reported as a multiply-defined symbol when linking with ncurses.
 2912 
 2913 This problem results from an incompatible change in ncurses, in
 2914 version 1.9.9e approximately.  This version is unable to provide a
 2915 definition of tparm without also defining tparam.  This is also
 2916 incompatible with Terminfo; as a result, the Emacs Terminfo support
 2917 does not work with this version of ncurses.
 2918 
 2919 The fix is to install a newer version of ncurses, such as version 4.2.
 2920 
 2921 ** Bootstrapping
 2922 
 2923 Bootstrapping (compiling the .el files) is normally only necessary
 2924 with development builds, since the .elc files are pre-compiled in releases.
 2925 
 2926 *** "No rule to make target" with Ubuntu 8.04 make 3.81-3build1
 2927 
 2928 Compiling the lisp files fails at random places, complaining:
 2929 "No rule to make target '/path/to/some/lisp.elc'".
 2930 The causes of this problem are not understood.  Using GNU make 3.81 compiled
 2931 from source, rather than the Ubuntu version, worked.
 2932 See <URL:https://debbugs.gnu.org/327>, <URL:https://debbugs.gnu.org/821>.
 2933 
 2934 ** Dumping
 2935 
 2936 *** Segfault during 'make'
 2937 
 2938 If Emacs segfaults when 'make' executes one of these commands:
 2939 
 2940   LC_ALL=C ./temacs -batch -l loadup bootstrap
 2941   LC_ALL=C ./temacs -batch -l loadup dump
 2942 
 2943 the problem may be due to inadequate workarounds for address space
 2944 layout randomization (ASLR), an operating system feature that
 2945 randomizes the virtual address space of a process.  ASLR is commonly
 2946 enabled in Linux and NetBSD kernels, and is intended to deter exploits
 2947 of pointer-related bugs in applications.  If ASLR is enabled, the
 2948 command:
 2949 
 2950    cat /proc/sys/kernel/randomize_va_space  # GNU/Linux
 2951    sysctl security.pax.aslr.global          # NetBSD
 2952 
 2953 outputs a nonzero value.
 2954 
 2955 These segfaults should not occur on most modern systems, because the
 2956 Emacs build procedure uses the command 'setfattr' or 'paxctl' to mark
 2957 the Emacs executable as requiring non-randomized address space, and
 2958 Emacs uses the 'personality' system call to disable address space
 2959 randomization when dumping.  However, older kernels may not support
 2960 'setfattr', 'paxctl', or 'personality', and newer Linux kernels have a
 2961 secure computing mode (seccomp) that can be configured to disable the
 2962 'personality' call.
 2963 
 2964 It may be possible to work around the 'personality' problem in a newer
 2965 Linux kernel by configuring seccomp to allow the 'personality' call.
 2966 For example, if you are building Emacs under Docker, you can run the
 2967 Docker container with a security profile that allows 'personality' by
 2968 using Docker's --security-opt option with an appropriate profile; see
 2969 <https://docs.docker.com/engine/security/seccomp/>.
 2970 
 2971 To work around the ASLR problem in either an older or a newer kernel,
 2972 you can temporarily disable the feature while building Emacs.  On
 2973 GNU/Linux you can do so using the following command (as root).
 2974 
 2975     echo 0 > /proc/sys/kernel/randomize_va_space
 2976 
 2977 You can re-enable the feature when you are done, by echoing the
 2978 original value back to the file.  NetBSD uses a different command,
 2979 e.g., 'sysctl -w security.pax.aslr.global=0'.
 2980 
 2981 Alternatively, you can try using the 'setarch' command when building
 2982 temacs like this, where -R disables address space randomization:
 2983 
 2984     setarch $(uname -m) -R make
 2985 
 2986 ASLR is not the only problem that can break Emacs dumping.  Another
 2987 issue is that in Red Hat Linux kernels, Exec-shield is enabled by
 2988 default, and this creates a different memory layout.  Emacs should
 2989 handle this at build time, but if this fails the following
 2990 instructions may be useful.  Exec-shield is enabled on your system if
 2991 
 2992     cat /proc/sys/kernel/exec-shield
 2993 
 2994 prints a nonzero value.  You can temporarily disable it as follows:
 2995 
 2996     echo 0 > /proc/sys/kernel/exec-shield
 2997 
 2998 As with randomize_va_space, you can re-enable Exec-shield when you are
 2999 done, by echoing the original value back to the file.
 3000 
 3001 *** temacs prints "Pure Lisp storage exhausted".
 3002 
 3003 This means that the Lisp code loaded from the .elc and .el files during
 3004 'temacs --batch --load loadup dump' took up more space than was allocated.
 3005 
 3006 This could be caused by
 3007  1) adding code to the preloaded Lisp files
 3008  2) adding more preloaded files in loadup.el
 3009  3) having a site-init.el or site-load.el which loads files.
 3010    Note that ANY site-init.el or site-load.el is nonstandard;
 3011    if you have received Emacs from some other site and it contains a
 3012    site-init.el or site-load.el file, consider deleting that file.
 3013  4) getting the wrong .el or .elc files
 3014    (not from the directory you expected).
 3015  5) deleting some .elc files that are supposed to exist.
 3016    This would cause the source files (.el files) to be
 3017    loaded instead.  They take up more room, so you lose.
 3018  6) a bug in the Emacs distribution which underestimates the space required.
 3019 
 3020 If the need for more space is legitimate, change the definition
 3021 of PURESIZE in puresize.h.
 3022 
 3023 But in some of the cases listed above, this problem is a consequence
 3024 of something else that is wrong.  Be sure to check and fix the real problem.
 3025 
 3026 *** OpenBSD 4.0 macppc: Segfault during dumping.
 3027 
 3028 The build aborts with signal 11 when the command './temacs --batch
 3029 --load loadup bootstrap' tries to load files.el.  A workaround seems
 3030 to be to reduce the level of compiler optimization used during the
 3031 build (from -O2 to -O1).  It is possible this is an OpenBSD
 3032 GCC problem specific to the macppc architecture, possibly only
 3033 occurring with older versions of GCC (e.g. 3.3.5).
 3034 
 3035 *** openSUSE 10.3: Segfault in bcopy during dumping.
 3036 
 3037 This is due to a bug in the bcopy implementation in openSUSE 10.3.
 3038 It is/will be fixed in an openSUSE update.
 3039 
 3040 ** First execution
 3041 
 3042 *** Emacs binary is not in executable format, and cannot be run.
 3043 
 3044 This was reported to happen when Emacs is built in a directory mounted
 3045 via NFS, for some combinations of NFS client and NFS server.
 3046 Usually, the file 'emacs' produced in these cases is full of
 3047 binary null characters, and the 'file' utility says:
 3048 
 3049     emacs: ASCII text, with no line terminators
 3050 
 3051 We don't know what exactly causes this failure.  A work-around is to
 3052 build Emacs in a directory on a local disk.
 3053 
 3054 *** The dumped Emacs crashes when run, trying to write pure data.
 3055 
 3056 On a system where getpagesize is not a system call, it is defined
 3057 as a macro.  If the definition (in both unex*.c and malloc.c) is wrong,
 3058 it can cause problems like this.  You might be able to find the correct
 3059 value in the man page for a.out(5).
 3060 
 3061 * 'make check' failures
 3062 
 3063 ** emacs-module-tests fail on Ubuntu 16.04
 3064 
 3065 This is due to a bug in GCC that was fixed in 2015; see
 3066 <https://lists.gnu.org/r/emacs-devel/2018-09/msg00548.html>.
 3067 You can work around the problem by using a later version of GCC or of
 3068 Ubuntu, or by configuring without modules.
 3069 
 3070 * Problems on legacy systems
 3071 
 3072 This section covers bugs reported on very old hardware or software.
 3073 If you are using hardware and an operating system shipped after 2000,
 3074 it is unlikely you will see any of these.
 3075 
 3076 *** Solaris 2.x
 3077 
 3078 **** Strange results from format %d in a few cases, on a Sun.
 3079 
 3080 Sun compiler version SC3.0 has been found to miscompile part of editfns.c.
 3081 The workaround is to compile with some other compiler such as GCC.
 3082 
 3083 **** On Solaris, Emacs dumps core if lisp-complete-symbol is called.
 3084 
 3085 If you compile Emacs with the -fast or -xO4 option with version 3.0.2
 3086 of the Sun C compiler, Emacs dumps core when lisp-complete-symbol is
 3087 called.  The problem does not happen if you compile with GCC.
 3088 
 3089 **** On Solaris, Emacs crashes if you use (display-time).
 3090 
 3091 This can happen if you configure Emacs without specifying the precise
 3092 version of Solaris that you are using.
 3093 
 3094 **** Solaris 2.x: GCC complains "64 bit integer types not supported".
 3095 
 3096 This suggests that GCC is not installed correctly.  Most likely you
 3097 are using GCC 2.7.2.3 (or earlier) on Solaris 2.6 (or later); this
 3098 does not work without patching.  To run GCC 2.7.2.3 on Solaris 2.6 or
 3099 later, you must patch fixinc.svr4 and reinstall GCC from scratch as
 3100 described in the Solaris FAQ
 3101 <http://www.wins.uva.nl/pub/solaris/solaris2.html>.  A better fix is
 3102 to upgrade to GCC 2.8.1 or later.
 3103 
 3104 **** Solaris 2.7: Building Emacs with WorkShop Compilers 5.0 98/12/15
 3105 C 5.0 failed, apparently with non-default CFLAGS, most probably due to
 3106 compiler bugs.  Using Sun Solaris 2.7 Sun WorkShop 6 update 1 C
 3107 release was reported to work without problems.  It worked OK on
 3108 another system with Solaris 8 using apparently the same 5.0 compiler
 3109 and the default CFLAGS.
 3110 
 3111 **** Solaris 2.6 and 7: the Compose key does not work.
 3112 
 3113 This is a bug in Motif in Solaris.  Supposedly it has been fixed for
 3114 the next major release of Solaris.  However, if someone with Sun
 3115 support complains to Sun about the bug, they may release a patch.
 3116 If you do this, mention Sun bug #4188711.
 3117 
 3118 One workaround is to use a locale that allows non-ASCII characters.
 3119 For example, before invoking emacs, set the LC_ALL environment
 3120 variable to "en_US" (American English).  The directory /usr/lib/locale
 3121 lists the supported locales; any locale other than "C" or "POSIX"
 3122 should do.
 3123 
 3124 pen@lysator.liu.se says (Feb 1998) that the Compose key does work
 3125 if you link with the MIT X11 libraries instead of the Solaris X11 libraries.
 3126 
 3127 ** MS-Windows 95, 98, ME, and NT
 3128 
 3129 *** MS-Windows NT/95: Problems running Perl under Emacs
 3130 
 3131 'perl -de 0' just hangs when executed in an Emacs subshell.
 3132 The fault lies with Perl (indirectly with Windows NT/95).
 3133 
 3134 The problem is that the Perl debugger explicitly opens a connection to
 3135 "CON", which is the DOS/NT equivalent of "/dev/tty", for interacting
 3136 with the user.
 3137 
 3138 On Unix, this is okay, because Emacs (or the shell?) creates a
 3139 pseudo-tty so that /dev/tty is really the pipe Emacs is using to
 3140 communicate with the subprocess.
 3141 
 3142 On NT, this fails because CON always refers to the handle for the
 3143 relevant console (approximately equivalent to a tty), and cannot be
 3144 redirected to refer to the pipe Emacs assigned to the subprocess as
 3145 stdin.
 3146 
 3147 A workaround is to modify perldb.pl to use STDIN/STDOUT instead of CON.
 3148 
 3149 For Perl 4:
 3150 
 3151     *** PERL/LIB/PERLDB.PL.orig	Wed May 26 08:24:18 1993
 3152     --- PERL/LIB/PERLDB.PL	Mon Jul 01 15:28:16 1996
 3153     ***************
 3154     *** 68,74 ****
 3155           $rcfile=".perldb";
 3156       }
 3157       else {
 3158     !     $console = "con";
 3159           $rcfile="perldb.ini";
 3160       }
 3161 
 3162     --- 68,74 ----
 3163           $rcfile=".perldb";
 3164       }
 3165       else {
 3166     !     $console = "";
 3167           $rcfile="perldb.ini";
 3168       }
 3169 
 3170 
 3171     For Perl 5:
 3172     *** perl/5.001/lib/perl5db.pl.orig	Sun Jun 04 21:13:40 1995
 3173     --- perl/5.001/lib/perl5db.pl	Mon Jul 01 17:00:08 1996
 3174     ***************
 3175     *** 22,28 ****
 3176           $rcfile=".perldb";
 3177       }
 3178       elsif (-e "con") {
 3179     !     $console = "con";
 3180           $rcfile="perldb.ini";
 3181       }
 3182       else {
 3183     --- 22,28 ----
 3184           $rcfile=".perldb";
 3185       }
 3186       elsif (-e "con") {
 3187     !     $console = "";
 3188           $rcfile="perldb.ini";
 3189       }
 3190       else {
 3191 
 3192 *** MS-Windows 95: Alt-f6 does not get through to Emacs.
 3193 
 3194 This character seems to be trapped by the kernel in Windows 95.
 3195 You can enter M-f6 by typing ESC f6.
 3196 
 3197 *** MS-Windows 95/98/ME: subprocesses do not terminate properly.
 3198 
 3199 This is a limitation of the Operating System, and can cause problems
 3200 when shutting down Windows.  Ensure that all subprocesses are exited
 3201 cleanly before exiting Emacs.  For more details, see the Emacs on MS
 3202 Windows FAQ (info manual "efaq-w32").
 3203 
 3204 *** MS-Windows 95/98/ME: crashes when Emacs invokes non-existent programs.
 3205 
 3206 When a program you are trying to run is not found on the PATH,
 3207 Windows might respond by crashing or locking up your system.  In
 3208 particular, this has been reported when trying to compile a Java
 3209 program in JDEE when javac.exe is installed, but not on the system PATH.
 3210 
 3211 ** MS-DOS
 3212 
 3213 *** When compiling with DJGPP on MS-Windows NT or later, "config msdos" fails.
 3214 
 3215 If the error message is "VDM has been already loaded", this is because
 3216 Windows has a program called 'redir.exe' that is incompatible with a
 3217 program by the same name supplied with DJGPP, which is used by
 3218 config.bat.  To resolve this, move the DJGPP's 'bin' subdirectory to
 3219 the front of your PATH environment variable.
 3220 
 3221 *** When Emacs compiled with DJGPP runs on Windows 2000 and later, it cannot
 3222 find your HOME directory.
 3223 
 3224 This was reported to happen when you click on "Save for future
 3225 sessions" button in a Customize buffer.  You might see an error
 3226 message like this one:
 3227 
 3228   basic-save-buffer-2: c:/FOO/BAR/~dosuser/: no such directory
 3229 
 3230 (The telltale sign is the "~USER" part at the end of the directory
 3231 Emacs complains about, where USER is your username or the literal
 3232 string "dosuser", which is the default username set up by the DJGPP
 3233 startup file DJGPP.ENV.)
 3234 
 3235 This happens when the functions 'user-login-name' and
 3236 'user-real-login-name' return different strings for your username as
 3237 Emacs sees it.  To correct this, make sure both USER and USERNAME
 3238 environment variables are set to the same value.  Windows 2000 and
 3239 later sets USERNAME, so if you want to keep that, make sure USER is
 3240 set to the same value.  If you don't want to set USER globally, you
 3241 can do it in the [emacs] section of your DJGPP.ENV file.
 3242 
 3243 *** When Emacs compiled with DJGPP runs on Vista, it runs out of memory.
 3244 
 3245 If Emacs running on Vista displays "!MEM FULL!" in the mode line, you
 3246 are hitting the memory allocation bugs in the Vista DPMI server.  See
 3247 msdos/INSTALL for how to work around these bugs (search for "Vista").
 3248 
 3249 *** When compiling with DJGPP on MS-Windows 95, Make fails for some targets
 3250 like make-docfile.
 3251 
 3252 This can happen if long file name support (the setting of environment
 3253 variable LFN) when Emacs distribution was unpacked and during
 3254 compilation are not the same.  See msdos/INSTALL for the explanation
 3255 of how to avoid this problem.
 3256 
 3257 *** Emacs compiled with DJGPP complains at startup:
 3258 
 3259   "Wrong type of argument: internal-facep, msdos-menu-active-face"
 3260 
 3261 This can happen if you define an environment variable 'TERM'.  Emacs
 3262 on MSDOS uses an internal terminal emulator which is disabled if the
 3263 value of 'TERM' is anything but the string "internal".  Emacs then
 3264 works as if its terminal were a dumb glass teletype that doesn't
 3265 support faces.  To work around this, arrange for 'TERM' to be
 3266 undefined when Emacs runs.  The best way to do that is to add an
 3267 [emacs] section to the DJGPP.ENV file which defines an empty value for
 3268 'TERM'; this way, only Emacs gets the empty value, while the rest of
 3269 your system works as before.
 3270 
 3271 *** MS-DOS: Emacs crashes at startup.
 3272 
 3273 Some users report that Emacs 19.29 requires dpmi memory management,
 3274 and crashes on startup if the system does not have it.  We don't
 3275 know why this happens--perhaps these machines don't have enough real
 3276 memory, or perhaps something is wrong in Emacs or the compiler.
 3277 However, arranging to use dpmi support is a workaround.
 3278 
 3279 You can find out if you have a dpmi host by running go32 without
 3280 arguments; it will tell you if it uses dpmi memory.  For more
 3281 information about dpmi memory, consult the djgpp FAQ.  (djgpp
 3282 is the GNU C compiler as packaged for MSDOS.)
 3283 
 3284 Compiling Emacs under MSDOS is extremely sensitive for proper memory
 3285 configuration.  If you experience problems during compilation, consider
 3286 removing some or all memory resident programs (notably disk caches)
 3287 and make sure that your memory managers are properly configured.  See
 3288 the djgpp faq for configuration hints.
 3289 
 3290 *** Emacs compiled with DJGPP for MS-DOS/MS-Windows cannot access files
 3291 in the directory with the special name 'dev' under the root of any
 3292 drive, e.g. 'c:/dev'.
 3293 
 3294 This is an unfortunate side-effect of the support for Unix-style
 3295 device names such as /dev/null in the DJGPP runtime library.  A
 3296 work-around is to rename the problem directory to another name.
 3297 
 3298 *** MS-DOS: Emacs compiled for MSDOS cannot find some Lisp files, or other
 3299 run-time support files, when long filename support is enabled.
 3300 
 3301 Usually, this problem will manifest itself when Emacs exits
 3302 immediately after flashing the startup screen, because it cannot find
 3303 the Lisp files it needs to load at startup.  Redirect Emacs stdout
 3304 and stderr to a file to see the error message printed by Emacs.
 3305 
 3306 Another manifestation of this problem is that Emacs is unable to load
 3307 the support for editing program sources in languages such as C and Lisp.
 3308 
 3309 This can happen if the Emacs distribution was unzipped without LFN
 3310 support, thus causing long filenames to be truncated to the first 6
 3311 characters and a numeric tail that Windows 95 normally attaches to it.
 3312 You should unzip the files again with a utility that supports long
 3313 filenames (such as djtar from DJGPP or InfoZip's UnZip program
 3314 compiled with DJGPP v2).  The file msdos/INSTALL explains this issue
 3315 in more detail.
 3316 
 3317 Another possible reason for such failures is that Emacs compiled for
 3318 MSDOS is used on Windows NT, where long file names are not supported
 3319 by this version of Emacs, but the distribution was unpacked by an
 3320 unzip program that preserved the long file names instead of truncating
 3321 them to DOS 8+3 limits.  To be useful on NT, the MSDOS port of Emacs
 3322 must be unzipped by a DOS utility, so that long file names are
 3323 properly truncated.
 3324 
 3325 ** Apple Macintosh operating systems
 3326 
 3327 *** OS X 10.9 and earlier: symlinks autocomplete as directories
 3328 
 3329 Autocompleting the name of a symbolic link incorrectly appends "/".
 3330 Building and running Emacs on OS X 10.10 (or later) fixes the problem.
 3331 Older operating systems are no longer supported by Apple.
 3332 https://bugs.gnu.org/31305
 3333 
 3334 ** Archaic window managers and toolkits
 3335 
 3336 *** Open Look: Under Open Look, the Emacs window disappears when you type M-q.
 3337 
 3338 Some versions of the Open Look window manager interpret M-q as a quit
 3339 command for whatever window you are typing at.  If you want to use
 3340 Emacs with that window manager, you should try to configure the window
 3341 manager to use some other command.   You can disable the
 3342 shortcut keys entirely by adding this line to ~/.OWdefaults:
 3343 
 3344     OpenWindows.WindowMenuAccelerators: False
 3345 
 3346 *** twm: A position you specified in .Xdefaults is ignored, using twm.
 3347 
 3348 twm normally ignores "program-specified" positions.
 3349 You can tell it to obey them with this command in your '.twmrc' file:
 3350 
 3351   UsePPosition	"on"		#allow clients to request a position
 3352 
 3353 ** Bugs related to old DEC hardware
 3354 
 3355 *** The Compose key on a DEC keyboard does not work as Meta key.
 3356 
 3357 This shell command should fix it:
 3358 
 3359   xmodmap -e 'keycode 0xb1 = Meta_L'
 3360 
 3361 *** Keyboard input gets confused after a beep when using a DECserver
 3362 as a concentrator.
 3363 
 3364 This problem seems to be a matter of configuring the DECserver to use
 3365 7 bit characters rather than 8 bit characters.
 3366 
 3367 This file is part of GNU Emacs.
 3368 
 3369 GNU Emacs is free software: you can redistribute it and/or modify
 3370 it under the terms of the GNU General Public License as published by
 3371 the Free Software Foundation, either version 3 of the License, or
 3372 (at your option) any later version.
 3373 
 3374 GNU Emacs is distributed in the hope that it will be useful,
 3375 but WITHOUT ANY WARRANTY; without even the implied warranty of
 3376 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 3377 GNU General Public License for more details.
 3378 
 3379 You should have received a copy of the GNU General Public License
 3380 along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
 3381 
 3382 
 3383 Local variables:
 3384 mode: outline
 3385 paragraph-separate: "[  ]*$"
 3386 end: