Known Problems with GNU Emacs Copyright (C) 1987-1989, 1993-1999, 2001-2024 Free Software Foundation, Inc. See the end of the file for license conditions. This file describes various problems that have been encountered in compiling, installing and running GNU Emacs. Try doing C-c C-t and browsing through the outline headers. (See C-h m for help on Outline mode.) Information about systems that are no longer supported, and old Emacs releases, has been removed. Consult older versions of this file if you are interested in that information. * Mule-UCS doesn't work in Emacs 23 onwards It's completely redundant now, as far as we know. * Emacs startup failures ** Emacs fails to start, complaining about missing fonts. A typical error message might be something like No fonts match ‘-*-fixed-medium-r-*--6-*-*-*-*-*-iso8859-1’ This happens because some X resource specifies a bad font family for Emacs to use. The possible places where this specification might be are: - in the X server resources database, often initialized from ~/.Xresources (use $ xrdb -query to find out the current state) - in your ~/.Xdefaults file - client-side X resource file, such as ~/Emacs or /usr/share/X11/app-defaults/Emacs One of these files might have bad or malformed specification of a fontset that Emacs should use. To fix the problem, you need to find the problematic line(s) and correct them. After correcting ~/.Xresources, the new data has to be merged into the X server resources database. Depending on the circumstances, the following command may do the trick. See xrdb(1) for more information. $ xrdb -merge ~/.Xresources ** Emacs compiled with Cairo crashes when restoring session from desktop file. This can happen if the '.emacs.desktop' file contains setting for 'font-backend' frame parameter. A workaround is to delete the offending '.emacs.desktop' file, or edit it to remove the setting of 'font-backend'. ** Emacs aborts while starting up, only when run without X. This problem often results from compiling Emacs with GCC when GCC was installed incorrectly. The usual error in installing GCC is to specify --includedir=/usr/include. Installation of GCC makes corrected copies of the system header files. GCC is supposed to use the corrected copies in preference to the original system headers. Specifying --includedir=/usr/include causes the original system header files to be used. On some systems, the definition of ioctl in the original system header files is invalid for ANSI C and causes Emacs not to work. The fix is to reinstall GCC, and this time do not specify --includedir when you configure it. Then recompile Emacs. Specifying --includedir is appropriate only in very special cases and it should *never* be the same directory where system header files are kept. ** Emacs does not start, complaining that it cannot open termcap database file. If your system uses Terminfo rather than termcap (most modern systems do), this could happen if the proper version of ncurses is not visible to the Emacs configure script (i.e. it cannot be found along the usual path the linker looks for libraries). It can happen because your version of ncurses is obsolete, or is available only in form of binaries. The solution is to install an up-to-date version of ncurses in the developer's form (header files, static libraries and symbolic links); in some GNU/Linux distributions (e.g. Debian) it constitutes a separate package. ** Emacs 20 and later fails to load Lisp files at startup. The typical error message might be like this: "Cannot open load file: fontset" This could happen if you compress the file lisp/subdirs.el. That file tells Emacs what are the directories where it should look for Lisp files. Emacs cannot work with subdirs.el compressed, since the Auto-compress mode it needs for this will not be loaded until later, when your .emacs file is processed. (The package 'fontset.el' is required to set up fonts used to display text on window systems, and it's loaded very early in the startup procedure.) Similarly, any other .el file for which there's no corresponding .elc file could fail to load if it is compressed. The solution is to uncompress all .el files that don't have a .elc file. Another possible reason for such failures is stale *.elc files lurking somewhere on your load-path -- see the next section. ** Emacs prints an error at startup after upgrading from an earlier version. An example of such an error is: x-complement-fontset-spec: "Wrong type argument: stringp, nil" This can be another symptom of stale *.elc files in your load-path. The following command will print any duplicate Lisp files that are present in load-path: emacs -batch -f list-load-path-shadows If this command prints any file names, some of these files are stale, and should be deleted or their directories removed from your load-path. * Crash bugs ** When Emacs is compiled with Gtk+, closing a display kills Emacs. There is a long-standing bug in GTK that prevents it from recovering from disconnects: https://gitlab.gnome.org/GNOME/gtk/issues/221 Thus, for instance, when Emacs is run as a server on a text terminal, and an X frame is created, and the X server for that frame crashes or exits unexpectedly, Emacs must exit to prevent a GTK error that would result in an endless loop. If you need Emacs to be able to recover from closing displays, compile it with the Lucid toolkit instead of GTK. ** Emacs compiled with GTK+ 3 crashes when run under some X servers. This happens when the X server does not provide certain display features that the underlying GTK+ 3 toolkit assumes. For example, this issue has been seen with remote X servers like X2Go. The symptoms are an Emacs crash, possibly triggered by the mouse entering the Emacs window, or an attempt to resize the Emacs window. The crash backtrace contains a call to XQueryPointer. This issue was fixed in the GTK+ 3 toolkit in commit 4b1c0256 in February 2018. If your GTK+ 3 is still affected, you can avoid the issue by recompiling Emacs with a different X toolkit, eg --with-toolkit=gtk2. References: https://gitlab.gnome.org/GNOME/gtk/commit/4b1c02560f0d8097bf5a11932e52fb72f3e9e94b https://debbugs.gnu.org/24280 https://bugs.debian.org/901038 https://bugzilla.redhat.com/1483942 https://access.redhat.com/solutions/3410101 ** Emacs compiled with GTK crashes at startup due to X protocol error. This is known to happen on elementary OS GNU/Linux systems. The error message is: X protocol error: BadMatch (invalid parameter attributes) on protocol request 140 When compiled with GTK, Emacs cannot recover from X disconnects. This is a GTK bug: https://gitlab.gnome.org/GNOME/gtk/issues/221 For details, see etc/PROBLEMS. Fatal error 6: Aborted followed by a C backtrace. (Sometimes the offending protocol request number is 139.) The relevant bug report is here: https://bugs.launchpad.net/elementaryos/+bug/1355274 A workaround is to set XLIB_SKIP_ARGB_VISUALS=1 in the environment before starting Emacs, or run Emacs as root. ** Emacs built with xwidgets aborts when displaying WebKit xwidgets This happens, for example, when 'M-x xwidget-webkit-browse-url' prompts for a URL and you type the URL at the prompt. The error message might look like this: X protocol error: GLXBadWindow on protocol request 151 Serial no: 4286 Failing resource ID (if any): 0x3c001c5 Minor code: 32 This happens because starting from version 2.42.1, the WebKitGTK developers discontinued support for off-screen windows, by presuming that every window holding a WebView widget is an X server window eligible for an OpenGL context. Emacs requires placing these widgets within offscreen windows managed by GTK, for each xwidget might be displayed in multiple distinct windows, and its contents must be captured and reproduced within all of them if that be the case. To put this another way, WebKitGTK doesn't support displaying a single widget more than once anymore. A possible workaround is to make sure xwidgets are not shown in more than one window. ** Emacs crashes with SIGTRAP when trying to start a WebKit xwidget. This could happen if the version of WebKitGTK installed on your system is buggy, and errors out trying to start a subprocess through Bubblewrap sandboxing. You can avoid the crash by setting the environment variables SNAP, SNAP_NAME and SNAP_REVISION, which will make WebKit use GLib to launch subprocesses instead. For example, invoke Emacs like this (where "..." stands for the other command-line arguments you intend to pass to Emacs): $ SNAP=1 SNAP_NAME=1 SNAP_REVISION=1 emacs ... ** Emacs built with tree-sitter crashes when some *-ts-mode is turned on. The crash is in many cases an abort due to run-time detection of stack smashing, and it happens when one of the *-ts-mode modes is turned on in a buffer. The reason is that the tree-sitter library changed its Application Binary Interface (ABI) between version 0.22.2 and 0.22.4, but did not increment the ABI version number. Therefore, Emacs compiled with tree-sitter versions before the change will try to use the shared library after the change, and crash due to incompatibilities in the ABI. Until and unless the tree-sitter developers release a library with an updated ABI version, the solution is to rebuild Emacs with the actual library with which it will be used. If you cannot rebuild Emacs, downgrade your tree-sitter library to version 0.22.2 or older. The relevant tree-sitter issue is here: https://github.com/tree-sitter/tree-sitter/issues/3296 ** Emacs crashes when you try to view a file with complex characters. One possible reason for this could be a bug in the libotf or the libm17n-flt/m17n-db libraries Emacs uses for displaying complex scripts. The easiest and the recommended way of solving these crashes is to build Emacs with HarfBuzz as the shaping engine library instead of libm17n-flt. Building with HarfBuzz is the default since Emacs 27.1. If you must use libm17n-flt, read on. Make sure you have the latest versions of these libraries installed. If the problem still persists with the latest released versions of these libraries, you can try building these libraries from their CVS repository: cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/m17n co libotf cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/m17n co m17n-db cvs -z3 -d:pserver:anonymous@cvs.savannah.nongnu.org:/sources/m17n co m17n-lib One known problem that causes such crashes is with using Noto Serif Kannada fonts. To work around that, force Emacs not to select these fonts, by adding the following to your ~/.emacs init file: (push "Noto Serif Kannada" face-ignored-fonts) You can try this interactively in a running Emacs session like this: M-: (push "Noto Serif Kannada" face-ignored-fonts) RET Another set of problems is caused by an incompatible libotf library. In this case, displaying the etc/HELLO file (as shown by C-h h) triggers the following message to be shown in the terminal from which you launched Emacs: symbol lookup error: /usr/bin/emacs: undefined symbol: OTF_open This problem occurs because unfortunately there are two libraries called "libotf". One is the library for handling OpenType fonts, https://www.nongnu.org/m17n/, which is the one that Emacs expects. The other is a library for Open Trace Format, and is used by some versions of the MPI message passing interface for parallel programming. For example, on RHEL6 GNU/Linux, the OpenMPI rpm provides a version of "libotf.so" in /usr/lib/openmpi/lib. This directory is not normally in the ld search path, but if you want to use OpenMPI, you must issue the command "module load openmpi". This adds /usr/lib/openmpi/lib to LD_LIBRARY_PATH. If you then start Emacs from the same shell, you will encounter this crash. Ref: There is no good solution to this problem if you need to use both OpenMPI and Emacs with libotf support. The best you can do is use a wrapper shell script (or function) "emacs" that removes the offending element from LD_LIBRARY_PATH before starting emacs proper. Or you could recompile Emacs with an -Wl,-rpath option that gives the location of the correct libotf. ** Emacs crashes in x-popup-dialog. This can happen if the dialog widget cannot find the font it wants to use. You can work around the problem by specifying another font with an X resource--for example, 'Emacs.dialog*.font: 9x15' (or any font that happens to exist on your X server). ** Emacs crashes when you use Bibtex mode. This happens if your system puts a small limit on stack size. You can prevent the problem by using a suitable shell command (often 'ulimit') to raise the stack size limit before you run Emacs. Patches to raise the stack size limit automatically in 'main' (src/emacs.c) on various systems would be greatly appreciated. ** Error message 'Symbol’s value as variable is void: x', followed by a segmentation fault and core dump. This has been tracked to a bug in tar! People report that tar erroneously added a line like this at the beginning of files of Lisp code: x FILENAME, N bytes, B tape blocks If your tar has this problem, install GNU tar--if you can manage to untar it :-). ** Emacs crashes when running in a terminal, if compiled with GCC 4.5.0 This version of GCC is buggy: see https://debbugs.gnu.org/6031 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43904 You can work around this error in gcc-4.5 by omitting sibling call optimization. To do this, configure Emacs with ./configure CFLAGS="-g -O2 -fno-optimize-sibling-calls" ** Emacs compiled with GCC 4.6.1 crashes on MS-Windows when C-g is pressed This is known to happen when Emacs is compiled with MinGW GCC 4.6.1 with the -O2 option (which is the default in the Windows build). The reason is a bug in MinGW GCC 4.6.1; to work around, either add the '-fno-omit-frame-pointer' switch to GCC or compile without optimizations ('--no-opt' switch to the configure.bat script). ** Emacs can crash when displaying PNG images with transparency. This is due to a bug introduced in ImageMagick 6.8.2-3. The bug should be fixed in ImageMagick 6.8.3-10. See . ** Crashes when displaying GIF images in Emacs built with version libungif-4.1.0 are resolved by using version libungif-4.1.0b1. Configure checks for the correct version, but this problem could occur if a binary built against a shared libungif is run on a system with an older version. ** Emacs aborts inside the function 'tparam1'. This can happen if Emacs was built without terminfo support, but the terminal's capabilities use format that is only supported by terminfo. If your system has ncurses installed, this might happen if your version of ncurses is broken; upgrading to a newer version of ncurses and reconfiguring and rebuilding Emacs should solve this. All modern systems support terminfo, so even if ncurses is not the problem, you should look for a way to configure Emacs so that it uses terminfo when built. ** Emacs crashes when using some version of the Exceed X server. Upgrading to a newer version of Exceed has been reported to prevent these crashes. You should consider switching to a free X server, such as Xming or Cygwin/X. ** Emacs crashes with SIGSEGV in XtInitializeWidgetClass. It crashes on X, but runs fine when called with option "-nw". This has been observed when Emacs is linked with GNU ld but without passing the -z nocombreloc flag. Emacs normally knows to pass the -z nocombreloc flag when needed, so if you come across a situation where the flag is necessary but missing, please report it via M-x report-emacs-bug. On platforms such as Solaris, you can also work around this problem by configuring your compiler to use the native linker instead of GNU ld. * Problems when reading or debugging Emacs C code Because Emacs does not install a copy of its C source code, users normally cannot easily read that code via commands like 'M-x describe-function' (C-h f) that display the definition of a function. However, some GNU/Linux systems provide separate packages containing this source code which can get C-h f to work if you are willing to do some tinkering, and some systems also provide packages containing debug info, which when combined with the source can be used to debug Emacs at the C level. ** Debian-based source and debuginfo On recent Debian-based systems, you can obtain and use a source package of Emacs as follows. *** Add the appropriate URI to /etc/apt/sources.list. To do this, become superuser and uncomment or add the appropriate 'deb-src' line. Details depend on the distribution. *** Execute a command like 'apt-get source emacs'. On older systems, append the top-level version number, e.g., 'apt-get source emacs25'. The target directory for unpacking the source tree is the current directory. *** Set find-function-C-source-directory accordingly. Once you have installed the source package, for example at /home/myself/deb-src/emacs-27.1, add the following line to your startup file: (setq find-function-C-source-directory "/home/myself/deb-src/emacs-27.1/src/") The installation directory of the Emacs source package will contain the exact package name and version number of Emacs that is installed on your system. If a new Emacs package is installed, the source package must be reinstalled as well, and the setting in your startup file must be updated. *** Debian-based debuginfo You can also install a debug package of Emacs with a command like 'apt-get install emacs-dbg' (on older systems, 'apt-get install emacs25-dbg'). You need to arrange for GDB to find where you installed the source code, e.g., by using GDB's 'directory' command. ** Red Hat-based source and debuginfo On recent Red Hat-based systems, you can install source and debug info via superuser commands like the following: # Add the *-debuginfo repositories (exact command depends on system). dnf config-manager --set-enabled fedora-debuginfo updates-debuginfo' # Install Emacs source and debug info. dnf install emacs-debugsource To get describe-function and similar commands to work, you can then add something like the following to your startup file: (setq find-function-C-source-directory "/usr/src/debug/emacs-27.1-1.fc31.x86_64/src/") However, the exact directory name will depend on the system, and you will need to both upgrade source and debug info when your system upgrades or patches Emacs, and change your startup file accordingly. ** Source and debuginfo for other systems If your system follows neither the Debian nor the Red Hat patterns, you can obtain the source and debuginfo by obtaining the source code of Emacs, building Emacs with the appropriate debug flags enabled, and running the just-built Emacs. * General runtime problems ** Lisp problems *** Changes made to .el files do not take effect. You may have forgotten to recompile them into .elc files. Then the old .elc files will be loaded, and your changes will not be seen. To fix this, do M-x byte-recompile-directory and specify the directory that contains the Lisp files. Emacs prints a warning when loading a .elc file which is older than the corresponding .el file. Alternatively, if you set the option 'load-prefer-newer' non-nil, Emacs will load whichever version of a file is the newest. *** Watch out for the EMACSLOADPATH environment variable. EMACSLOADPATH overrides which directories the function "load" will search. If you observe strange problems, check for this variable in your environment. ** Keyboard problems *** PGTK build of Emacs running on Wayland doesn't recognize Hyper modifier. If you arrange for the Wayland compositor to send the Hyper key modifier (e.g., via XKB customizations), the Hyper modifier will still not be reported to Emacs. The reason is that GDK 3.x doesn't recognize the Hyper key modifier. Since GDK 3.x is no longer developed, this bug in GDK will probably never be solved. And the Emacs PGTK build cannot yet support GTK4, where this problem is reportedly solved. *** Emacs built with GTK lags in its response to keyboard input. This can happen when input methods are used. It happens because Emacs behaves in an unconventional way with respect to GTK input methods: it registers to receive keyboard input as unprocessed key events with metadata (as opposed to receiving them as text strings). Most GTK programs use the latter approach, so some modern input methods have bugs and misbehave when faced with the way Emacs does it. A workaround is to set GTK_IM_MODULE=none in the environment, or maybe find a different input method without these problems. *** Unable to enter the M-| key on some German keyboards. Some users have reported that M-| suffers from "keyboard ghosting". This can't be fixed by Emacs, as the keypress never gets passed to it at all (as can be verified using "xev"). You can work around this by typing 'ESC |' instead. *** "Compose Character" key does strange things when used as a Meta key. If you define one key to serve as both Meta and Compose Character, you will get strange results. In previous Emacs versions, this "worked" in that the key acted as Meta--that's because the older Emacs versions did not try to support Compose Character. Now Emacs tries to do character composition in the standard X way. This means that you must pick one meaning or the other for any given key. You can use both functions (Meta, and Compose Character) if you assign them to two different keys. *** C-z just refreshes the screen instead of suspending Emacs. You are probably using a shell that doesn't support job control, even though the system itself is capable of it. Either use a different shell, or set the variable 'cannot-suspend' to a non-nil value. *** Emacs running on WSL receives stray characters as input. For example, you could see Emacs inserting 'z' characters even though nothing is typed on the keyboard, and even if you unplug the keyboard. The reason is a bug in the WSL X server's handling of key-press and key-repeat events. A workaround is to use the Cygwin or native MS-Windows build of Emacs instead. *** On MS-Windows, the Windows key gets "stuck". When this problem happens, Windows behaves as if the Windows key were permanently pressed down. This could be a side effect of Emacs on MS-Windows hooking keyboard input on a low level, in order to support registering the Windows keys as hot keys. If that hook takes too much time for some reason, Windows can decide to remove the hook, which then has this effect. This is arguably a bug in Emacs, for which we don't yet have a solution. To work around, set the 'LowLevelHooksTimeout' value in the registry key "HKEY_CURRENT_USER\Control Panel\Desktop" to a number higher than 200 msec; the maximum allowed value is 1000 msec (create the value if it doesn't exist under that key). ** Mailers and other helper programs *** movemail compiled with POP support can't connect to the POP server. This problem can occur if you do not configure --with-mailutils, and don't have GNU Mailutils installed. Then Emacs uses its own version of movemail, which doesn't support secure POP connections. To solve this, install GNU Mailutils. Also, make sure that the 'pop' entry in /etc/services, or in the services NIS map if your machine uses NIS, has the same port number as the entry on the POP server. A common error is for the POP server to be listening on port 110, the assigned port for the POP3 protocol, while the client is trying to connect on port 109, the assigned port for the old POP protocol. *** RMAIL gets error getting new mail. RMAIL gets new mail from /usr/spool/mail/$USER using a program called 'movemail'. This program interlocks with /bin/mail using the protocol defined by /bin/mail. There are two different protocols in general use. One of them uses the 'flock' system call. The other involves creating a lock file; 'movemail' must be able to write in /usr/spool/mail in order to do this. You control which one is used by defining, or not defining, the macro MAIL_USE_FLOCK in config.h. IF YOU DON'T USE THE FORM OF INTERLOCKING THAT IS NORMAL ON YOUR SYSTEM, YOU CAN LOSE MAIL! If your system uses the lock file protocol, and fascist restrictions prevent ordinary users from writing the lock files in /usr/spool/mail, you may need to make 'movemail' setgid to a suitable group such as 'mail'. To do this, use the following commands (as root) after doing the make install. chgrp mail movemail chmod 2755 movemail Installation normally copies movemail from the build directory to an installation directory which is usually under /usr/local/lib. The installed copy of movemail is usually in the directory /usr/local/lib/emacs/VERSION/TARGET. You must change the group and mode of the installed copy; changing the group and mode of the build directory copy is ineffective. *** rcs2log gives you the awk error message "too many fields". This is due to an arbitrary limit in certain versions of awk. The solution is to use gawk (GNU awk). *** Saving a file encrypted with GnuPG via EasyPG hangs. This is known to happen with GnuPG v2.4.1. The only known workaround is to downgrade to a version of GnuPG older than 2.4.1, or upgrade to version 2.4.4 and newer, which reportedly solves the problem. Note that GnuPG v2.2.42 and later also has this problem, so you should also avoid those later 2.2.4x versions; v2.2.41 is reported to work fine. *** EasyPG loopback pinentry does not work with gpgsm. This happens with the 'gpgsm' command from all versions of GnuPG. EasyPG relies on the machine-parseable interface that is provided by 'gpg2' with option '--status-fd', but gpgsm does not support this. As a workaround, input the passphrase with a GUI-capable pinentry program like 'pinentry-gnome' or 'pinentry-qt5'. Alternatively, you can use the 'pinentry' package from Emacs 25. ** Problems with hostname resolution *** Emacs does not know your host's fully-qualified domain name. For example, (system-name) returns some variation on "localhost.localdomain", rather the name you were expecting. You need to configure your machine with a fully qualified domain name, (i.e., a name with at least one "."), either in /etc/hostname or wherever your system calls for specifying this. If you cannot fix the configuration, you can set the Lisp variable mail-host-address to the value you want. ** NFS *** Emacs says it has saved a file, but the file does not actually appear on disk. This can happen on certain systems when you are using NFS, if the remote disk is full. It is due to a bug in NFS (or certain NFS implementations), and there is apparently nothing Emacs can do to detect the problem. Emacs checks the failure codes of all the system calls involved in writing a file, including 'close'; but in the case where the problem occurs, none of those system calls fails. ** PSGML conflicts with sgml-mode. PSGML package uses the same names of some variables (like keymap) as built-in sgml-mode.el because it was created as a replacement of that package. The conflict will be shown if you load sgml-mode.el before psgml.el. E.g. this could happen if you edit HTML page and then start to work with SGML or XML file. html-mode (from sgml-mode.el) is used for HTML file and loading of psgml.el (for sgml-mode or xml-mode) will cause an error. ** PCL-CVS *** Lines are not updated or new lines are added in the buffer upon commit. When committing files located higher in the hierarchy than the examined directory, some versions of the CVS program return an ambiguous message from which PCL-CVS cannot extract the full location of the committed files. As a result, the corresponding lines in the PCL-CVS buffer are not updated with the new revision of these files, and new lines are added to the top-level directory. This can happen with CVS versions 1.12.8 and 1.12.9. Upgrade to CVS 1.12.10 or newer to fix this problem. ** Miscellaneous problems *** 'set-mouse-color' and the '-ms' command line argument do not work. Systems where the default cursors are not simple 1 bit-per-pixel bitmaps usually forbid recoloring the cursor, since it is unclear which colors should replace those already present within each cursor image. For example, 'set-mouse-color' and '-ms' have no function on X systems with GNOME, KDE, and other recent desktop environments employing cursor images containing colors and partial transparency. Changing the cursor color is also impossible on MS-Windows and PGTK systems. In the former case, it is because the prerequisite code has yet to be written. In the latter, it is because GTK does not provide for changing the color of cursor images. *** Display artifacts on GUI frames on X-based systems. This is known to be caused by using double-buffering (which is enabled by default in Emacs 26 and later). The artifacts typically appear after commands that cause Emacs to scroll the display. You can disable double-buffering by evaluating the following form: (modify-all-frames-parameters '((inhibit-double-buffering . t))) To make this permanent, add it to your ~/.emacs init file. Note that disabling double-buffering will cause flickering of the display in some situations. *** Self-documentation messages are garbled. This means that the file 'etc/DOC' doesn't properly correspond with the Emacs executable. Redumping Emacs and then installing the corresponding pair of files should fix the problem. *** Programs running under terminal emulator do not recognize 'emacs' terminal type. The cause of this is a shell startup file that sets the TERMCAP environment variable. The terminal emulator uses that variable to provide the information on the special terminal type that Emacs emulates. Rewrite your shell startup file so that it does not change TERMCAP in such a case. You could use the following conditional which sets it only if it is undefined. if ( ! ${?TERMCAP} ) setenv TERMCAP ~/my-termcap-file Or you could set TERMCAP only when you set TERM--which should not happen in a non-login shell. *** In Shell mode, you get a ^M at the end of every line. This happens to people who use tcsh, because it is trying to be too smart. It sees that the Shell uses terminal type 'unknown' and turns on the flag to output ^M at the end of each line. You can fix the problem by adding this to your .cshrc file: if ($?INSIDE_EMACS && $?tcsh) unset edit stty -icrnl -onlcr -echo susp ^Z endif *** In Shell buffers using ksh, resizing a window inserts random characters. The characters come from the PS2 prompt, but they are not followed by a newline, which messes up the next command you type. This strange effect is caused by Emacs 25 and later telling the shell that its screen size changed. To work around the problem, customize the option 'window-adjust-process-window-size-function' to "Do not adjust process window sizes" (Lisp value 'ignore'). *** Displaying PDF files in DocView produces an empty buffer. This can happen if your Emacs is configured to convert PDF to SVG for display, and the version of the MuPDF package you have installed has a known bug, whereby it sometimes produces invalid SVG images. Version 1.21 of MuPDF is known to be affected. The solution is either to upgrade or downgrade to a version of MuPDF that doesn't have this bug, or to disable conversion of PDF files to SVG images by customizing the user option 'doc-view-mupdf-use-svg'. Emacs will then convert PDF to PNG images instead. *** In Inferior Python mode, input is echoed and native completion doesn't work. This happens when python uses a libedit based readline module, which is the default on macOS. This can be worked around by installing a GNU readline based module instead, for example, using setuptools sudo easy_install gnureadline And then rename the system's readline so that it won't be loaded: cd /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload mv readline.so readline.so.bak See for more details on installation. *** On MS-Windows, invoking "M-x run-python" signals an error. If the error says something like this: Python was not found; run with arguments to install from the Microsoft Store, or disable this shortcut from Settings > Manage App Execution Aliases. Process Python exited abnormally with code 49 then this is due to the MS-Windows "feature" that is intended to encourage you to install the latest available Python version. It works by placing "fake" python.exe and python3.exe executables in a special directory, and having that directory on your Path _before_ the directory where the real Python executable is installed. That "fake" Python then decides whether to redirect you to the Microsoft Store or invoke the actual Python. The directory where Windows keeps those "fake" executables is under your Windows user's 'AppData' directory, typically 'C:\Users\\AppData\Local\Microsoft\WindowsApps', where "" is the user name of your Windows user. To solve this, you have several alternatives: . Go to "Settings > Manage App Execution Aliases" and turn OFF the aliases for python.exe and/or python3.exe. This will affect only Python, and may require you to manage upgrades to your Python installation manually, instead of being automatically prompted by MS-Windows. . Move the directory with the "fake" executables to the end of Path, or at least after the directory where the real Python is installed. Depending on the position in Path where you move it, it will affect Python and/or other programs which Windows monitors via the "App Execution Aliases" feature. . Manually remove python.exe and/or python3.exe from the above directory. Again, this affects only your Python installation. Whatever you do, you will need to restart Emacs to refresh its notion of the directory where python.exe/python3.exe lives, because that is recorded when Python mode is started. *** Visiting files in some auto-mounted directories causes Emacs to print 'Error reading dir-locals: (file-error "Read error" "is a directory" ...' This can happen if the auto-mounter mistakenly reports that .dir-locals.el exists and is a directory. There is nothing Emacs can do about this, but you can avoid the issue by adding a suitable entry to the variable 'locate-dominating-stop-dir-regexp'. For example, if the problem relates to "/smb/.dir-locals.el", set that variable to a new value where you replace "net\\|afs" with "net\\|afs\\|smb". (The default value already matches common auto-mount prefixes.) See https://lists.gnu.org/r/help-gnu-emacs/2015-02/msg00461.html . *** Attempting to visit remote files via ange-ftp fails. If the error message is "ange-ftp-file-modtime: Specified time is not representable", then this could happen when 'lukemftp' is used as the ftp client. This was reported to happen on Debian GNU/Linux, kernel version 2.4.3, with 'lukemftp' 1.5-5, but might happen on other systems as well. To avoid this problem, switch to using the standard ftp client. On a Debian system, type update-alternatives --config ftp and then choose /usr/bin/netkit-ftp. *** Dired is very slow. This could happen if getting a file system's status takes a long time. Possible reasons for this include: - ClearCase mounted filesystems (VOBs) that sometimes make 'df' response time extremely slow (dozens of seconds); - slow automounters on some old versions of Unix; To work around the problem, you could use Git or some other free-software program, instead of ClearCase. *** Various commands that visit files on networked filesystems fail. This could happen if the filesystem of those files is mounted in a way that causes the files to be accessed via a symlink. One such example is the 'amd' automounter, which unmounts the filesystem after some period of lack of use. Another example is Emacs running on MS-Windows that accesses files on remote server via symlinks whose target is a UNC of the form '\\server\share'. The reason for these problems is that some Emacs commands visit files via their truename, resolving the symlink, which causes these files' default-directory to also have the symlink resolved. If the resolved directory has access problems, subsequent commands from that file's buffer could fail. For example, the stock MS-Windows shell 'cmd.exe' is unable to use a UNC-form directory as the current directory, so 'shell-command' and its callers will typically fail. Similarly with using targets of symlinks which no longer mount the remote filesystem will fail. You can solve these problems in several ways: - Write a 'find-file'hook' function which will change the value of 'default-directory' to reference the symlink instead of its target. - Set up 'directory-abbrev-alist' to automatically convert the 'default-directory' of such files in the same manner. - On MS-Windows, map a drive letter to the '\\server\share' directory and point your symlinks to a directory name that uses the drive letter. *** On MS-Windows, visiting files in OneDrive fails. This is known to happen when OneDrive is accessed via the so-called "metered connections", whose use is charged by the volume of transferred data. Those are typically wireless links using a modem or a mobile phone. In these cases, files that are left in the cloud and not downloaded to the local computer can produce various failures in system calls that access the files or their meta-data. The solution is to disable the "metered connection" status from the WiFi properties (reachable from the Windows Settings menu). This will cause files to be downloaded to the local computer when they are accessed (which could take some time, and Emacs functions accessing the file will wait for that), avoiding the errors. *** On systems with shared libraries you might encounter run-time errors from the dynamic linker telling you that it is unable to find some shared libraries, for instance those for Xaw3d or image support. These errors mean Emacs has been linked with a library whose shared library is not in the default search path of the dynamic linker. Similar problems could prevent Emacs from building, since the build process invokes Emacs several times. On many systems, it is possible to set LD_LIBRARY_PATH in your environment to specify additional directories where shared libraries can be found. Other systems allow setting LD_RUN_PATH in a similar way, but before Emacs is linked. With LD_RUN_PATH set, the linker will include a specified run-time search path in the executable. Please refer to the documentation of your dynamic linker for details. *** When you run Ispell from Emacs, it reports a "misalignment" error. This can happen if you compiled the Ispell program to use ASCII characters only and then try to use it from Emacs with non-ASCII characters, like Latin-1. The solution is to recompile Ispell with support for 8-bit characters. To see whether your Ispell program supports 8-bit characters, type this at your shell's prompt: ispell -vv and look in the output for the string "NO8BIT". If Ispell says "!NO8BIT (8BIT)", your speller supports 8-bit characters; otherwise it does not. To rebuild Ispell with 8-bit character support, edit the local.h file in the Ispell distribution and make sure it does _not_ define NO8BIT. Then rebuild the speller. Another possible cause for "misalignment" error messages is that the version of Ispell installed on your machine is old. Upgrade. Yet another possibility is that you are trying to spell-check a word in a language that doesn't fit the dictionary you choose for use by Ispell. (Ispell can only spell-check one language at a time, because it uses a single dictionary.) Make sure that the text you are spelling and the dictionary used by Ispell conform to each other. If your spell-checking program is Aspell, it has been reported that if you have a personal configuration file (normally ~/.aspell.conf), it can cause this error. Remove that file, execute 'ispell-kill-ispell' in Emacs, and then try spell-checking again. *** TLS problems, e.g., Gnus hangs when fetching via imaps https://debbugs.gnu.org/24247 gnutls-cli 3.5.3 (2016-08-09) does not generate a "- Handshake was completed" message that tls.el relies upon, causing affected Emacs functions to hang. To work around the problem, use older or newer versions of gnutls-cli, or use Emacs's built-in gnutls support. *** SVG images may be cropped incorrectly with librsvg 2.45 or older. Librsvg 2.46 and above have improved geometry code which Emacs is able to take advantage of. * Runtime problems related to font handling ** Some fonts are detected but not usable under Xft. We understand that these issues were resolved in Xft release 2.3.6. Some fonts might not be usable under Emacs even though they show up in the font family list when Emacs is built with Xft. This is because Emacs prevents fonts that have color glyphs (such as color Emoji) from being used, since they typically cause Xft crashes. On some GNU/Linux systems, fonts (such as Source Code Pro) that do not have color glyphs are reported as color fonts, causing them to be unavailable when using Xft. This is known to happen under Fedora GNU/Linux 36 or later, and possibly other distributions as well. If you encounter a such a font, you can enable it while ignoring other fonts that actually have color glyphs by adding its family name to the list `xft-color-font-whitelist'. ** Characters are displayed as empty boxes or with wrong font under X. *** This may be due to your local fontconfig customization. Try removing or moving aside "$XDG_CONFIG_HOME/fontconfig/conf.d" and "$XDG_CONFIG_HOME/fontconfig/fonts.conf" ($XDG_CONFIG_HOME is treated as "~/.config" if not set) Running Emacs as FC_DEBUG=1024 emacs will cause fontconfig to output information about which configuration files it is reading. Running Emacs as FC_DEBUG=1 emacs will result in information about the results of fontconfig's font matching (including the filename(s) of the resulting fonts). *** This can occur when two different versions of FontConfig are used. For example, XFree86 4.3.0 has one version and Gnome usually comes with a newer version. Emacs compiled with Gtk+ will then use the newer version. In most cases the problem can be temporarily fixed by stopping the application that has the error (it can be Emacs or any other application), removing ~/.fonts.cache-1, and then starting the application again. If removing ~/.fonts.cache-1 and restarting doesn't help, the application with problem must be recompiled with the same version of FontConfig as the rest of the system uses. For KDE, it is sufficient to recompile Qt. *** Some fonts have a missing glyph and no default character. This is known to occur for character number 160 (no-break space, U+A0) in some fonts, such as Lucida but Emacs sets the display table for the unibyte and Latin-1 version of this character to display a space. *** Some of the fonts called for in your fontset may not exist on your X server. Each X font covers just a fraction of the characters that Emacs supports. To display the whole range of Emacs characters requires many different fonts, collected into a fontset. You can remedy the problem by installing additional fonts. The intlfonts distribution includes a full spectrum of fonts that can display all the characters Emacs supports. The etl-unicode collection of fonts (available from ) includes fonts that can display many Unicode characters; they can also be used by ps-print and ps-mule to print Unicode characters. ** Under X, some characters appear improperly aligned in their lines. You may have bad fonts. ** Under X, some characters are unexpectedly wide. e.g. recent versions of Inconsolata show this issue for almost all of its characters. Due to what is probably an Xft bug, the determination of the width of some characters is incorrect. One workaround is to build emacs with Cairo enabled ("configure --with-cairo" and have the appropriate Cairo development packages installed) as this configuration does not suffer from this problem. See and for more discussion. ** Under X, an unexpected monospace font is used as the default font. When compiled with XFT, Emacs tries to use a default font named "monospace". This is a "virtual font", which the operating system (Fontconfig) redirects to a suitable font such as DejaVu Sans Mono. On some systems, there exists a font that is actually named Monospace, which takes over the virtual font. This is considered an operating system bug; see https://lists.gnu.org/r/emacs-devel/2008-10/msg00696.html If you encounter this problem, set the default font to a specific font in your .Xresources or initialization file. For instance, you can put the following in your .Xresources: Emacs.font: DejaVu Sans Mono 12 ** Certain fonts make each line take one pixel more than it should. This is because these fonts contain characters a little taller than the font's nominal height. Emacs needs to make sure that lines do not overlap. ** Font Lock displays portions of the buffer in incorrect faces. By far the most frequent cause of this is a parenthesis '(' or a brace '{' in column zero. Font Lock assumes that such a paren is outside of any comment or string. This is of course not true in general, but the vast majority of well-formatted program source files don't have such parens, and therefore this assumption is used to allow optimizations in Font Lock's syntactical analysis. These optimizations avoid some pathological cases where jit-lock, the Just-in-Time fontification introduced with Emacs 21.1, could significantly slow down scrolling through the buffer, especially scrolling backwards, and also jumping to the end of a very large buffer. Beginning with version 22.1, a parenthesis or a brace in column zero is highlighted in bold-red face if it is inside a string or a comment, to indicate that it could interfere with Font Lock (and also with indentation) and should be moved or escaped with a backslash. If you don't use large buffers, or have a very fast machine which makes the delays insignificant, you can avoid the incorrect fontification by setting the variable 'font-lock-beginning-of-syntax-function' to a nil value. (This must be done _after_ turning on Font Lock.) Another alternative is to avoid a paren in column zero. For example, in a Lisp string you could precede the paren with a backslash. ** Emacs pauses for several seconds when changing the default font. This has been reported for fvwm 2.2.5 and the window manager of KDE 2.1. The reason for the pause is Xt waiting for a ConfigureNotify event from the window manager, which the window manager doesn't send. Xt stops waiting after a default timeout of usually 5 seconds. A workaround for this is to add something like emacs.waitForWM: false to your X resources. Alternatively, add '(wait-for-wm . nil)' to a frame's parameter list, like this: (modify-frame-parameters nil '((wait-for-wm . nil))) (this should go into your '.emacs' file). ** Underlines appear at the wrong position. This is caused by fonts having a wrong UNDERLINE_POSITION property. To avoid this problem (seen in some very old X releases and font packages), set x-use-underline-position-properties to nil. To see what is the value of UNDERLINE_POSITION defined by the font, type 'xlsfonts -lll FONT' and look at the font's UNDERLINE_POSITION property. ** When using Exceed, fonts sometimes appear too tall. When the display is set to an Exceed X-server and fonts are specified (either explicitly with the -fn option or implicitly with X resources) then the fonts may appear "too tall". The actual character sizes are correct but there is too much vertical spacing between rows, which gives the appearance of "double spacing". To prevent this, turn off the Exceed's "automatic font substitution" feature (in the font part of the configuration window). ** Subscript/superscript text in TeX is hard to read. If 'tex-fontify-script' is non-nil, tex-mode displays subscript/superscript text in the faces subscript/superscript, which are smaller than the normal font and lowered/raised. With some fonts, nested superscripts (say) can be hard to read. Switching to a different font, or changing your antialiasing setting (on an LCD screen), can both make the problem disappear. Alternatively, customize the following variables: tex-font-script-display (how much to lower/raise); tex-suscript-height-ratio (how much smaller than normal); tex-suscript-height-minimum (minimum height). ** Screen refresh is slow when there are special characters for which no suitable font is available If the display is too slow in refreshing when you scroll to a new region, or when you edit the buffer, it might be due to the fact that some characters cannot be displayed in the default font, and Emacs is spending too much time in looking for a suitable font to display them. You can suspect this if you have several characters that are displayed as small rectangles containing a hexadecimal code inside. The solution is to install the appropriate fonts on your machine. For instance if you are editing a text with a lot of math symbols, then installing a font like 'Symbola' should solve this problem. Another reason for slow display is reportedly the nerd-fonts installation, even when Symbola is installed as well. Uninstalling nerd-fonts was reported to solve the problem in that case. ** Emacs running on GNU/Linux system with the m17n library Ver.1.7.1 or the earlier version has a problem with rendering Bengali script. The problem can be fixed by installing the newer version of the m17n library (if any), or by following this procedure: 1. Locate the file BENG-OTF.flt installed on your system as part of the m17n library. Usually it is under the directory /usr/share/m17n. 2. Apply the following patch to BENG-OTF.flt ------------------------------------------------------------ diff --git a/FLT/BENG-OTF.flt b/FLT/BENG-OTF.flt index 45cc554..0cc5e76 100644 --- a/FLT/BENG-OTF.flt +++ b/FLT/BENG-OTF.flt @@ -232,7 +232,7 @@ (lang-forms (cond ("(.H)J" (1 :otf=beng=half+)) - (".H" :otf=beng=blwf,half,vatu+) + (".+H" :otf=beng=blwf,half,vatu+) ("." =))) (post ------------------------------------------------------------ If you can't modify that file directly, copy it to the directory ~/.m17n.d/ (create it if it doesn't exist), and apply the patch. ** Emacs running on GNU/Linux system with the m17n library Ver.1.7.1 or the earlier version has a problem with rendering Lao script with OpenType font. The problem can be fixed by installing the newer version of the m17n library (if any), or by following this procedure: 1. Locate the file LAOO-OTF.flt installed on your system as part of the m17n library. Usually it is under the directory /usr/share/m17n. 2. Apply the following patch to LAOO-OTF.flt ------------------------------------------------------------ diff --git a/FLT/LAOO-OTF.flt b/FLT/LAOO-OTF.flt index 5504171..431adf8 100644 --- a/FLT/LAOO-OTF.flt +++ b/FLT/LAOO-OTF.flt @@ -3,7 +3,7 @@ ;; See the end for copying conditions. (font layouter laoo-otf nil - (font (nil phetsarath\ ot unicode-bmp))) + (font (nil nil unicode-bmp :otf=lao\ ))) ;;;
  • LAOO-OTF.flt ------------------------------------------------------------ If you can't modify that file directly, copy it to the directory ~/.m17n.d/ (create it if it doesn't exist), and apply the patch. ** On Haiku, some proportionally-spaced fonts display with artifacting. This is a Haiku bug: https://dev.haiku-os.org/ticket/17229, which can be remedied by using a different font that does not exhibit this problem, or by configuring Emacs '--with-be-cairo'. So far, Bitstream Charter and Noto Sans have been known to exhibit this problem, while Noto Sans Display is known to not do so. ** On MS-Windows, some characters display as boxes with hex code. Also, some characters could display with wrong fonts. This can happen if Emacs was compiled without HarfBuzz support, and/or if the HarfBuzz DLLs are not available at run time. Emacs will then fall back to the Uniscribe as its shaping engine; Uniscribe was deprecated by Microsoft, and sometimes fails to display correctly when modern fonts are used, such as Noto Emoji or Ebrima. The solution is to switch to a configuration that uses HarfBuzz as its shaping engine, where these problems don't exist. ** On MS-Windows, selecting some fonts as the default font doesn't work. This can happen if you select font variants such as "Light" or "Thin" or "Semibold" or "Heavy", and some others. The APIs used by Emacs on Windows to enumerate fonts in a font family consider only 4 font variants to belong to the same family: Regular, Italic, Bold, and Bold-Italic. All the other variants aren't returned by those APIs when we request to list all the fonts in a family, and thus aren't considered by Emacs to belong to the family. So any font variant that is not one of those 4 will likely not work as expected; in most cases Emacs will select some other font instead. The only workaround is not to choose such font variants as the default font when running Emacs on MS-Windows. * Internationalization problems ** M-{ does not work on a Spanish PC keyboard. Many Spanish keyboards seem to ignore that combination. Emacs can't do anything about it. ** International characters aren't displayed under X. ** Accented ISO-8859-1 characters are displayed as | or _. Try other font set sizes (S-mouse-1). If the problem persists with other sizes as well, your text is corrupted, probably through software that is not 8-bit clean. If the problem goes away with another font size, it's probably because some fonts pretend to be ISO-8859-1 fonts when they are really ASCII fonts. In particular the schumacher-clean fonts have this bug in some versions of X. To see what glyphs are included in a font, use 'xfd', like this: xfd -fn -schumacher-clean-medium-r-normal--12-120-75-75-c-60-iso8859-1 If this shows only ASCII glyphs, the font is indeed the source of the problem. The solution is to remove the corresponding lines from the appropriate 'fonts.alias' file, then run 'mkfontdir' in that directory, and then run 'xset fp rehash'. ** fcitx input methods don't work with xwidgets. fcitx-based input methods might not work when xwidgets are displayed, such as inside an xwidget-webkit buffer. This manifests as the pre-edit window of the input method disappearing, and the Emacs frame losing input focus as soon as you try to type anything. You can work around this problem by switching to IBus, or by using a native Emacs input method and disabling XIM altogether. For example, you can add the following line: Emacs.useXIM: false In your ~/.Xresources file, then run $ xrdb ~/.Xresources And restart Emacs. ** Emacs hangs when using XIM This is due to an old bug in the implementation of the X protocol's XIM transport: when an input method crashes for some reason, Xlib cannot recover. Emacs cannot do anything about this except wait for input method developers to fix their crashes. You can work around these problems by disabling XIM in your X resources: Emacs.useXIM: false ** On Haiku, BeCJK doesn't work properly with Emacs Some popular Haiku input methods such BeCJK are known to behave badly when interacting with Emacs, in ways such as stealing input focus and displaying popup windows that don't disappear. If you are affected, you should use an Emacs input method instead. * X runtime problems ** X security problems *** Emacs faces trouble when running as an untrusted client. When Emacs is running as an untrusted client under X servers with the Security extension, it is unable to use some window manager features but reports them to the window manager anyway. This can lead to constant prompting by the window manager about Emacs being unresponsive. To resolve the problem, place: (setq x-detect-server-trust t) in your early-init.el. ** X keyboard problems *** `x-focus-frame' fails to activate the frame. Some window managers prevent `x-focus-frame' from activating the given frame when Emacs is in the background. Emacs tries to work around this problem by default, but the workaround does not work on all window managers. You can try different workarounds by changing the value of `x-allow-focus-stealing' (see its doc string for more details). The value `imitate-pager' may be required on some versions of KWin. *** You "lose characters" after typing Compose Character key. This is because the Compose Character key is defined as the keysym Multi_key, and Emacs (seeing that) does the proper X character-composition processing. If you don't want your Compose key to do that, you can redefine it with xmodmap. For example, here's one way to turn it into a Meta key: xmodmap -e "keysym Multi_key = Meta_L" If all users at your site of a particular keyboard prefer Meta to Compose, you can make the remapping happen automatically by adding the xmodmap command to the xdm setup script for that display. *** Using X Window System, control-shift-leftbutton makes Emacs hang. Use the shell command 'xset bc' to make the old X Menu package work. *** C-SPC fails to work on Fedora GNU/Linux (or with fcitx input method). Fedora Core 4 steals the C-SPC key by default for the 'iiimx' program which is the input method for some languages. It blocks Emacs users from using the C-SPC key for 'set-mark-command'. One solutions is to remove the 'space' from the 'Iiimx' file which can be found in the '/usr/lib/X11/app-defaults' directory. However, that requires root access. Another is to specify 'Emacs*useXIM: false' in your X resources. Another is to build Emacs with the '--without-xim' configure option. The same problem happens on any other system if you are using fcitx (Chinese input method) which by default use C-SPC for toggling. If you want to use fcitx with Emacs, you have two choices. Toggle fcitx by another key (e.g. C-\) by modifying ~/.fcitx/config, or be accustomed to use C-@ for 'set-mark-command'. *** M-SPC seems to be ignored as input. See if your X server is set up to use this as a command for character composition. *** The S-C-t key combination doesn't get passed to Emacs on X. This happens because some X configurations assign the Ctrl-Shift-t combination the same meaning as the Multi_key. The offending definition is in the file '...lib/X11/locale/iso8859-1/Compose'; there might be other similar combinations which are grabbed by X for similar purposes. We think that this can be countermanded with the 'xmodmap' utility, if you want to be able to bind one of these key sequences within Emacs. *** Under X, C-v and/or other keys don't work. These may have been intercepted by your window manager. See the WM's documentation for how to change this. *** Clicking C-mouse-2 in the scroll bar doesn't split the window. This currently doesn't work with scroll-bar widgets (and we don't know a good way of implementing it with widgets). If Emacs is configured --without-toolkit-scroll-bars, C-mouse-2 on the scroll bar does work. *** Inability to send an Alt-modified key, when Emacs is communicating directly with an X server. If you have tried to bind an Alt-modified key as a command, and it does not work to type the command, the first thing you should check is whether the key is getting through to Emacs. To do this, type C-h c followed by the Alt-modified key. C-h c should say what kind of event it read. If it says it read an Alt-modified key, then make sure you have made the key binding correctly. If C-h c reports an event that doesn't have the Alt modifier, it may be because your X server has no key for the Alt modifier. The X server that comes from MIT does not set up the Alt modifier by default. If your keyboard has keys named Alt, you can enable them as follows: xmodmap -e 'add mod2 = Alt_L' xmodmap -e 'add mod2 = Alt_R' If the keyboard has just one key named Alt, then only one of those commands is needed. The modifier 'mod2' is a reasonable choice if you are using an unmodified MIT version of X. Otherwise, choose any modifier bit not otherwise used. If your keyboard does not have keys named Alt, you can use some other keys. Use the keysym command in xmodmap to turn a function key (or some other 'spare' key) into Alt_L or into Alt_R, and then use the commands show above to make them modifier keys. Note that if you have Alt keys but no Meta keys, Emacs translates Alt into Meta. This is because of the great importance of Meta in Emacs. *** Emacs hangs or crashes when a large portion of text is selected or killed. This is caused by a bug in the clipboard management applets (it has been observed in 'klipper' and 'clipit'), which periodically request the X clipboard contents from applications. After a while, Emacs may print a message: Timed out waiting for property-notify event A workaround is to not use 'klipper'/'clipit'. Upgrading 'klipper' to the one coming with KDE 3.3 or later might solve the problem; if it doesn't, set 'select-active-regions' to 'only' or nil. *** Emacs doesn't receive the key "C-.", displaying an input field instead. This is caused by the IBus Emoji input panel, which is usually bound to "C-.". You can disable that panel by running the following command: $ gsettings set org.freedesktop.ibus.panel.emoji hotkey "[]" ** Window-manager and toolkit-related problems *** Emacs built with GTK+ displays giant tool bar icons in some cases This is because some icon themes (such as the KDE Breeze icon theme) have several incorrectly sized icons, which also causes the toolbar to expand uncontrollably. The fix is to switch to a different icon theme, or to use Emacs's own toolbar icons by placing: (setq x-gtk-stock-map nil) in your early-init.el. *** Emacs built with GTK+ toolkit produces corrupted display on HiDPI screen This can happen if you set GDK_SCALE=2 in the environment or in your '.xinitrc' file. (This setting is usually accompanied by GDK_DPI_SCALE=0.5.) Emacs can not support these settings correctly, as it doesn't use GTK+ exclusively. The result is that sometimes widgets like the scroll bar are displayed incorrectly, and frames could be displayed "cropped" to only part of the stuff that should be displayed. The workaround is to explicitly disable these settings when invoking Emacs, for example (from a Posix shell prompt): $ GDK_SCALE=1 GDK_DPI_SCALE=1 emacs *** Emacs built with GTK+ toolkit can unexpectedly widen frames This resizing takes place when a frame is not wide enough to accommodate its entire menu bar. Typically, it occurs when switching buffers or changing a buffer's major mode and the new mode adds entries to the menu bar. The frame is then widened by the window manager so that the menu bar is fully shown. Subsequently switching to another buffer or changing the buffer's mode will not shrink the frame back to its previous width. The height of the frame remains unaltered. Apparently, the failure is also dependent on the chosen font. The resizing is usually accompanied by console output like Gtk-CRITICAL **: gtk_distribute_natural_allocation: assertion 'extra_space >= 0' failed It's not clear whether the GTK version used has any impact on the occurrence of the failure. So far, the failure has been observed with GTK+ versions 3.4.2, 3.14.5 and 3.18.7. However, another 3.4.2 build does not exhibit the bug. Some window managers (Xfce) apparently work around this failure by cropping the menu bar. With other windows managers, it's possible to shrink the frame manually after the problem occurs, e.g. by dragging the frame's border with the mouse. However, some window managers have been reported to refuse such attempts and snap back to the width needed to show the full menu bar (wmii) or at least cause the screen to flicker during such resizing attempts (i3, IceWM). See also https://debbugs.gnu.org/cgi/bugreport.cgi?bug=15700, https://debbugs.gnu.org/cgi/bugreport.cgi?bug=22000, https://debbugs.gnu.org/cgi/bugreport.cgi?bug=22898 and https://lists.gnu.org/r/emacs-devel/2016-07/msg00154.html. *** Metacity: Resizing Emacs or ALT-Tab causes X to be unresponsive. This happens sometimes when using Metacity. Resizing Emacs or ALT-Tab:bing makes the system unresponsive to the mouse or the keyboard. Killing Emacs or shifting out from X and back again usually cures it (i.e. Ctrl-Alt-F1 and then Alt-F7). A bug for it is here: https://bugs.launchpad.net/ubuntu/+source/metacity/+bug/231034. Note that a permanent fix seems to be to disable "assistive technologies". *** Enlightenment: Frames not redrawn after switching virtual desktops With Enlightenment version 0.25, Emacs frames may no be redrawn orderly after switching back from another virtual desktop. Setting the variable 'x-set-frame-visibility-more-laxly' to one of 'focus-in', 'expose' or 't' should fix this. *** Gnome: Emacs receives input directly from the keyboard, bypassing XIM. This seems to happen when gnome-settings-daemon version 2.12 or later is running. If gnome-settings-daemon is not running, Emacs receives input through XIM without any problem. Furthermore, this seems only to happen in *.UTF-8 locales; zh_CN.GB2312 and zh_CN.GBK locales, for example, work fine. A bug report has been filed in the Gnome bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=357032 *** Gnome: GPaste clipboard manager causes erratic behavior of 'yank' The symptom is that 'kill-line' followed by 'yank' often (but not always) doesn't insert the whitespace of the killed and yanked line. The solution is to set the GPaste "trim items" option to OFF. *** Gnome: Navigation from Nautilus to remote files. If you navigate to a file, which belongs to a remote server, in Nautilus via "Open With Emacs" you might not be able to save this file once you have modified it in Emacs. The reasons for the failure can vary, and for some connection methods saving the file might even succeed. If the remote connection in Nautilus uses ssh or sftp, you could mitigate the problem by the following lines in your .emacs file: (dir-locals-set-class-variables 'gvfs '((nil . ((create-lockfiles . nil))))) (dir-locals-set-directory-class (format "/run/user/%d/gvfs" (user-uid)) 'gvfs) A better approach might be to avoid navigation from Nautilus to Emacs for such files, and instead to open the file in Emacs using Tramp remote file name syntax. *** Gnome: GTK builds with XInput2 freeze when making a frame fullscreen. This problem exists with GTK 3.24.30 in GNOME 41.1 and possibly other versions. The solution is to upgrade GNOME Shell to the version that comes with GNOME 41.2. *** KDE: When running on KDE, colors or fonts are not as specified for Emacs, or messed up. For example, you could see background you set for Emacs only in the empty portions of the Emacs display, while characters have some other background. This happens because KDE's defaults apply its color and font definitions even to applications that weren't compiled for KDE. The solution is to uncheck the "Apply fonts and colors to non-KDE apps" option in Preferences->Look&Feel->Style (KDE 2). In KDE 3, this option is in the "Colors" section, rather than "Style". Alternatively, if you do want the KDE defaults to apply to other applications, but not to Emacs, you could modify the file 'Emacs.ad' (should be in the '/usr/share/apps/kdisplay/app-defaults/' directory) so that it doesn't set the default background and foreground only for Emacs. For example, make sure the following resources are either not present or commented out: Emacs.default.attributeForeground Emacs.default.attributeBackground Emacs*Foreground Emacs*Background It is also reported that a bug in the gtk-engines-qt engine can cause this if Emacs is compiled with Gtk+. The bug is fixed in version 0.7 or newer of gtk-engines-qt. *** KDE / Plasma 5: Emacs exhausts memory and needs to be killed This problem occurs when large selections contain mixed line endings (i.e. the buffer has LF line endings, but in some parts CRLF is used). The source of the problem is currently under investigation, older versions of Emacs up to 24.5 just hang for a few seconds and then return with the message "Timed out waiting for property-notify event" as described in the previous note. As a workaround, go to the settings dialog for the Clipboard widget and select the option "Ignore Selection". Note: Plasma 5 has replaced the separate klipper process from earlier KDE versions with functionality directly integrated into plasmashell, so even if you've previously did not use klipper this will affect you. Also, all configuration you might have done to klipper is not used by the new Clipboard widget / plasmoid since it uses its own settings. You can hide the Clipboard widget by removing its entry from the system tray settings "Extra Items", but it's not clear if the underlying functionality in plasmashell gets fully disabled as well. At least a restart of plasmashell is required for the clipboard history to be cleared. *** XFCE: Selected frame loses focus This can happen, e.g., in Ediff: when you move between the differences by typing 'n' or 'p' into the control frame, input focus unexpectedly switches to the buffers where Emacs shows the differences, instead of being left in the Ediff control frame. The reason is a bug in the window manager: it shifts input focus when raising a frame. A workaround is to activate the "focus stealing prevention" option of the window manager (in XFCE settings, under "window manager tweaks", in the "focus" tab). *** CDE: Frames may cover dialogs they created when using CDE. This can happen if you have "Allow Primary Windows On Top" enabled which seems to be the default in the Common Desktop Environment. To change, go in to "Desktop Controls" -> "Window Style Manager" and uncheck "Allow Primary Windows On Top". *** Xaw3d : When using Xaw3d scroll bars without arrows, the very first mouse click in a scroll bar might be ignored by the scroll bar widget. This is probably a bug in Xaw3d; when Xaw3d is compiled with arrows, the problem disappears. *** Xaw: There are known binary incompatibilities between Xaw, Xaw3d, neXtaw, XawM and the few other derivatives of Xaw. So when you compile with one of these, it may not work to dynamically link with another one. For example, strange problems, such as Emacs exiting when you type "C-x 1", were reported when Emacs compiled with Xaw3d and libXaw was used with neXtaw at run time. The solution is to rebuild Emacs with the toolkit version you actually want to use, or set LD_PRELOAD to preload the same toolkit version you built Emacs with. *** Open Motif: Problems with file dialogs in Emacs built with Open Motif. When Emacs 21 is built with Open Motif 2.1, it can happen that the graphical file dialog boxes do not work properly. The "OK", "Filter" and "Cancel" buttons do not respond to mouse clicks. Dragging the file dialog window usually causes the buttons to work again. As a workaround, you can try building Emacs using Motif or LessTif instead. Another workaround is not to use the mouse to trigger file prompts, but to use the keyboard. This way, you will be prompted for a file in the minibuffer instead of a graphical file dialog. *** LessTif: Problems in Emacs built with LessTif. The problems seem to depend on the version of LessTif and the Motif emulation for which it is set up. Only the Motif 1.2 emulation seems to be stable enough in LessTif. LessTif 0.92-17's Motif 1.2 emulation seems to work okay on FreeBSD. On GNU/Linux systems, lesstif-0.92.6 configured with "./configure --enable-build-12 --enable-default-12" is reported to be the most successful. The binary GNU/Linux package lesstif-devel-0.92.0-1.i386.rpm was reported to have problems with menu placement. On some systems, Emacs occasionally locks up, grabbing all mouse and keyboard events. We don't know what causes these problems; they are not reproducible by Emacs developers. *** Motif: The Motif version of Emacs paints the screen a solid color. This has been observed to result from the following X resource: Emacs*default.attributeFont: -*-courier-medium-r-*-*-*-140-*-*-*-*-iso8859-* That the resource has this effect indicates a bug in something, but we do not know what. If it is an Emacs bug, we hope someone can explain what the bug is so we can fix it. In the mean time, removing the resource prevents the problem. *** FVWM: Some versions of FVWM incorrectly set the 'sticky' frame parameter. Version 2.6.4 of the FVWM can make a frame sticky (appear on all user desktops) when setting the 'sticky' frame parameter to nil. This may happen without any special user interaction, for example, when Emacs restores a saved desktop. A fix is to install version 2.6.8 of FVWM, see https://debbugs.gnu.org/cgi/bugreport.cgi?bug=31650. ** General X problems *** Redisplay using X is much slower than previous Emacs versions. We've noticed that certain X servers draw the text much slower when scroll bars are on the left. We don't know why this happens. If this happens to you, you can work around it by putting the scroll bars on the right (as they were in Emacs 19). Here's how to do this: (set-scroll-bar-mode 'right) If you're not sure whether (or how much) this problem affects you, try that and see how much difference it makes. To set things back to normal, do (set-scroll-bar-mode 'left) *** Redisplay with scaled images is slow in Emacs built with Cairo. Cairo expends a noticeable amount of CPU time displaying large images with applied transforms. These images most frequently appear within EWW buffers or in Image Mode buffers after executing the image scaling commands `i +' or `i -', and their presence incurs a performance penalty of hundereds of milliseconds to seconds upon redisplay. The remedy is to build Emacs without Cairo after verifying the XRender extension is present on your X server and its headers are present on your system, in which case Emacs will use XRender to efficiently perform image transforms within the X server. *** Error messages about undefined colors on X. The messages might say something like this: Unable to load color "grey95" (typically, in the '*Messages*' buffer), or something like this: Error while displaying tooltip: (error Undefined color lightyellow) These problems could happen if some other X program has used up too many colors of the X palette, leaving Emacs with insufficient system resources to load all the colors it needs. A solution is to exit the offending X programs before starting Emacs. "undefined color" messages can also occur if the RgbPath entry in the X configuration file is incorrect, or the rgb.txt file is not where X expects to find it. *** Improving performance with slow X connections. There are several ways to improve this performance, any subset of which can be carried out at the same time: 1) Use the "--with-x-toolkit=no" build of Emacs. By not relying on any toolkit (exhibiting potentially slow behavior), it has been made very fast over networks exhibiting high latency, but suitable bandwidth. 2) If you don't need X Input Methods (XIM) for entering text in some language you use, you can improve performance on WAN links by using the X resource useXIM to turn off use of XIM. This does not affect the use of Emacs's own input methods, which are part of the Leim package. 3) If the connection is very slow, you might also want to consider switching off scroll bars, menu bar, and tool bar. Adding the following forms to your .emacs file will accomplish that, but only after the initial frame is displayed: (scroll-bar-mode -1) (menu-bar-mode -1) (tool-bar-mode -1) For still quicker startup, put these X resources in your .Xresources or .Xdefaults file: Emacs.verticalScrollBars: off Emacs.menuBar: off Emacs.toolBar: off 4) Use ssh to forward the X connection, and enable compression on this forwarded X connection (ssh -XC remotehostname emacs ...). Keep in mind that this does not help with latency problems, only bandwidth ones. 5) Use lbxproxy on the remote end of the connection. This is an interface to the low bandwidth X extension in some outdated X servers, which improves performance dramatically, at the slight expense of correctness of the X protocol. lbxproxy achieves the performance gain by grouping several X requests in one TCP packet and sending them off together, instead of requiring a round-trip for each X request in a separate packet. The switches that seem to work best for emacs are: -noatomsfile -nowinattr -cheaterrors -cheatevents Note that the -nograbcmap option is known to cause problems. For more about lbxproxy, see: http://www.x.org/archive/X11R6.8.0/doc/lbxproxy.1.html Keep in mind that lbxproxy and the LBX extension are now obsolete. 6) If copying and killing is slow, try to disable the interaction with the native system's clipboard by adding these lines to your .emacs file: (setq interprogram-cut-function nil) (setq interprogram-paste-function nil) 7) If selecting text with the mouse is slow, the main culprit is likely `select-active-regions', coupled with a program monitoring the clipboard or primary selection on the X server you are connected to. Try turning that off. However, over networks with moderate to high latency, with no clipboard monitor running, the bottleneck is likely to be `mouse-position' instead. Set the variable `x-use-fast-mouse-position' to either any non-nil value, or to the symbol `really-fast' if that is still too slow. Doing so will also cause Emacs features that relies on accurate mouse position reporting to stop working reliably. 8) If creating or resizing frames is slow, turn off `frame-resize-pixelwise' (this will not take effect until you create a new frame); then, enable `x-lax-frame-positioning'. This means frame placement will be less accurate, but makes frame creation, movement, and resize visibly faster. *** Emacs gives the error, Couldn't find per display information. This can result if the X server runs out of memory because Emacs uses a large number of fonts. On systems where this happens, C-h h is likely to cause it. We do not know of a way to prevent the problem. *** Emacs does not notice when you release the mouse. There are reports that this happened with (some) Microsoft mice and that replacing the mouse made it stop. *** You can't select from submenus (in the X toolkit version). On certain systems, mouse-tracking and selection in top-level menus works properly with the X toolkit, but neither of them works when you bring up a submenu (such as Bookmarks or Compare or Apply Patch, in the Files menu). This works on most systems. There is speculation that the failure is due to bugs in old versions of X toolkit libraries, but no one really knows. If someone debugs this and finds the precise cause, perhaps a workaround can be found. *** An error message such as 'X protocol error: BadMatch (invalid parameter attributes) on protocol request 93'. This comes from having an invalid X resource, such as emacs*Cursor: black (which is invalid because it specifies a color name for something that isn't a color.) The fix is to correct your X resources. *** Slow startup on X11R6 with X windows. If Emacs takes two minutes to start up on X11R6, see if your X resources specify any Adobe fonts. That causes the type-1 font renderer to start up, even if the font you asked for is not a type-1 font. One way to avoid this problem is to eliminate the type-1 fonts from your font path, like this: xset -fp /usr/X11R6/lib/X11/fonts/Type1/ *** Pull-down menus appear in the wrong place, in the toolkit version of Emacs. An X resource of this form can cause the problem: Emacs*geometry: 80x55+0+0 This resource is supposed to apply, and does apply, to the menus individually as well as to Emacs frames. If that is not what you want, rewrite the resource. To check thoroughly for such resource specifications, use 'xrdb -query' to see what resources the X server records, and also look at the user's ~/.Xdefaults and ~/.Xdefaults-* files. *** Emacs running under X Window System does not handle mouse clicks. *** 'emacs -geometry 80x20' finds a file named '80x20'. One cause of such problems is having (setq term-file-prefix nil) in your .emacs file. Another cause is a bad value of EMACSLOADPATH in the environment. *** X doesn't work if DISPLAY uses a hostname. People have reported kernel bugs in certain systems that cause Emacs not to work with X if DISPLAY is set using a host name. But the problem does not occur if DISPLAY is set to 'unix:0.0'. I think the bug has to do with SIGIO or FIONREAD. You may be able to compensate for the bug by doing (set-input-mode nil nil). However, that has the disadvantage of turning off interrupts, so that you are unable to quit out of a Lisp program by typing C-g. *** Prevent double pastes in X The problem: a region, such as a command, is pasted twice when you copy it with your mouse from GNU Emacs to an xterm or an RXVT shell in X. The solution: try the following in your X configuration file, /etc/X11/xorg.conf This should enable both PS/2 and USB mice for single copies. You do not need any other drivers or options. Section "InputDevice" Identifier "Generic Mouse" Driver "mousedev" Option "Device" "/dev/input/mice" EndSection *** Emacs is slow to exit in X After you use e.g. C-x C-c to exit, it takes many seconds before the Emacs window disappears. If Emacs was started from a terminal, you see the message: Error saving to X clipboard manager. If the problem persists, set 'x-select-enable-clipboard-manager' to nil. As the message suggests, this problem occurs when Emacs thinks you have a clipboard manager program running, but has trouble contacting it. If you don't want to use a clipboard manager, you can set the suggested variable. Or you can make Emacs not wait so long by reducing the value of 'x-selection-timeout', either in .emacs or with X resources. Sometimes this problem is due to a bug in your clipboard manager. Updating to the latest version of the manager can help. For example, in the Xfce 4.8 desktop environment, the clipboard manager in versions of xfce4-settings-helper before 4.8.2 is buggy; https://bugzilla.xfce.org/show_bug.cgi?id=7588 . *** Warning messages when running in Ubuntu When you start Emacs you may see something like this: (emacs:2286): LIBDBUSMENU-GTK-CRITICAL **: watch_submenu: assertion 'GTK_IS_MENU_SHELL(menu)' failed This happens if the Emacs binary has been renamed. The cause is the Ubuntu appmenu concept. It tries to track Emacs menus and show them in the top panel, instead of in each Emacs window. This is not properly implemented, so it fails for Emacs. The order of menus is wrong, and things like copy/paste that depend on what state Emacs is in are usually wrong (i.e. paste disabled even if you should be able to paste, and similar). You can get back menus on each frame by starting emacs like this: % env UBUNTU_MENUPROXY= emacs *** Mouse click coordinates not recognized correctly on multiple monitors. This happens on the proprietary X server ASTEC-X when the number of monitors is changed after the server has started. A workaround is to restart the X server after the monitor configuration has been changed. *** Touchpad gestures don't work and/or emit warning messages. Support for touch gestures in Emacs requires a sufficiently new X server. We currently know of only one: version 21.1.0 or later of the X.Org server, coupled with the xf86-input-libinput input driver. Type 'M-: (x-server-input-extension-version) RET'; if that doesn't return '(2 4)' (version 2.4) or later, your version of the X server and libraries are too old and need to be upgraded. When pinching or swiping on your touchpad, you might see a warning message that looks like: XInputWireToCookie: Unknown generic event. type 28 This happens when your XInput headers support XInput 2.4, but the actual version of libXi installed does not. The solution is to upgrade your libXi binaries to libXi 1.8.0 or later, to correspond with your XInput headers. *** Requesting a private colormap makes Emacs hang. The part of Xlib that provides this feature is broken in modern incarnations of Xlib, so it cannot possibly work. The solution is to remove anything that looks like this: Emacs.privateColormap: on From your X defaults file. Your X server might also provide a different visual class that will do what you want. You can experiment with `TrueColor-8', by placing this: Emacs.visualClass: TrueColor-8 in your ~/.Xresources, and loading that file. *** Colors messed up on Cairo or GTK builds. If your display defaults to a visual where pixel values cannot be directly converted to their corresponding real colors, a build with Cairo drawing or GTK will display colors incorrectly. This is because Cairo and GTK foolishly assume that all RGB values can be converted directly from their individual components, without asking the X server to allocate the color. Your X server might have a different visual which is decomposed and not colormapped. Try the following in your ~/.Xresources: Emacs.visualClass: TrueColor-N where "N" is the bit depth of the visual your X server defaults to. If that does not work, you lose. Configure Emacs '--without-cairo' and '--with-x-toolkit=lucid' instead. *** GUI widgets don't display on GTK builds, except for scrollbars. This can happen if your visual does not have a decomposed colormap, and your X server has the X rendering extension. To solve the problem, disable the X rendering extension on your X server, or rebuild Emacs without GTK+. *** On Accelerated X, the GTK 3 menu bar does not select items. The solution is to run Emacs with the environment variable 'GDK_DEBUG' set to "nograbs", like this (where "..." stands for the other command-line arguments you intend to pass to Emacs): GDK_DEBUG=nograbs emacs ... Accelerated X is a proprietary X server. Aside from being proprietary, it has many other disadvantages, such as not supporting most recent hardware and most modern extensions to the X protocol. Consider switching to a free X server, such as X.Org. If setting GDK_DEBUG causes GTK to complain about not being built with support for debugging options, then there is nothing you can do, except switch to a free X server. *** 'set-mouse-position' does not move the pointer on Xwayland. This is because Wayland does not allow programs to warp the pointer. There is nothing that can be done about this problem, except to switch to an X session. Some versions of the Xwayland server will pretend to warp the pointer, so mouse-motion events might be sent to the position the mouse was supposed to have moved to, even though the cursor displays at the same on-screen position. *** With X forwarding, mouse highlighting can make Emacs slow. If you see slow updates when moving the mouse in an Emacs running on a remote X server, try this: (setq mouse-highlight nil) *** Dropping text on xterm doesn't work. Emacs sends synthetic button events to legacy clients such as xterm that do not support either the XDND or Motif drag-and-drop protocols in order to "paste" the text that was dropped. Unfortunately, xterm is configured to ignore these events by default. Add the following to your X defaults file to avoid the problem: XTerm.*.allowSendEvents: True Note that this can in theory pose a security risk, but in practice modern X servers have so many other ways to send input to clients without signifying that the event is synthesized that it does not matter. *** Programs which use XSendEvent cannot send input events to Emacs. Emacs built to use the X Input Extension cannot receive core input events sent through the SendEvent server request, since these events intercepted by the X server when sent to input extension clients. For such programs to function again, Emacs must be run on an X server where the input extension is disabled, or alternatively be configured with the "--without-xinput2" option. *** Scrolling with mouse-wheel lags in GTK3 builds. We don't know why this happens, but one workaround is to build Emacs with a different toolkit. For example: ./configure --without-toolkit-scroll-bars --with-x-toolkit=athena This produces a build which uses Athena toolkit, and disables toolkit scroll bars which could sometimes be slow. * Runtime problems on character terminals ** The meta key does not work on xterm. Typing M-x rings the terminal bell, and inserts a string like ";120~". For recent xterm versions (>= 216), Emacs uses xterm's modifyOtherKeys feature to generate strings for key combinations that are not otherwise usable. One circumstance in which this can cause problems is if you have specified the X resource xterm*VT100.Translations to contain translations that use the meta key. Then xterm will not use meta in modified function-keys, which confuses Emacs. To fix this, you can remove the X resource or put this in your init file: (xterm-remove-modify-other-keys) ** The shift TAB key combination works as meta TAB on a Linux console. This happens because on your keyboard layout, S-TAB produces the same keycodes as typing ESC TAB individually. The best way to solve this is to modify your keyboard layout to produce different codes, and tell Emacs what these new codes mean. The current keyboard layout will probably be a .map.gz file somewhere under /usr/share/keymaps. Identify this file, possibly from a system initialization file such as /etc/conf.d/keymaps. Run gunzip on it to decompress it, and amend the entries for keycode 15 to look something like this: keycode 15 = Tab alt keycode 15 = Meta_Tab shift keycode 15 = F219 string F219 = "\033[4}\011" # Shift+ After possibly saving this file under a different name, compress it again using gzip. Amend /etc/conf.d/keyamps, etc., if needed. Further details can be found in the man page for loadkeys. Then add the following line near the start of your site-start.el or .emacs or init.el file: (define-key input-decode-map "\e[4}\t" 'backtab) ** Emacs spontaneously displays "I-search: " at the bottom of the screen. This means that Control-S/Control-Q (XON/XOFF) "flow control" is being used. C-s/C-q flow control is bad for Emacs editors because it takes away C-s and C-q as user commands. Since editors do not output long streams of text without user commands, there is no need for a user-issuable "stop output" command in an editor; therefore, a properly designed flow control mechanism would transmit all possible input characters without interference. Designing such a mechanism is easy, for a person with at least half a brain. There are three possible reasons why flow control could be taking place: 1) Terminal has not been told to disable flow control 2) Insufficient padding for the terminal in use 3) Some sort of terminal concentrator or line switch is responsible First of all, many terminals have a set-up mode which controls whether they generate XON/XOFF flow control characters. This must be set to "no XON/XOFF" in order for Emacs to work. (For example, on a VT220 you may select "No XOFF" in the setup menu.) Sometimes there is an escape sequence that the computer can send to turn flow control off and on. If so, perhaps the termcap 'ti' string should turn flow control off, and the 'te' string should turn it on. Once the terminal has been told "no flow control", you may find it needs more padding. The amount of padding Emacs sends is controlled by the termcap entry for the terminal in use, and by the output baud rate as known by the kernel. The shell command 'stty' will print your output baud rate; 'stty' with suitable arguments will set it if it is wrong. Setting to a higher speed causes increased padding. If the results are wrong for the correct speed, there is probably a problem in the termcap entry. You must speak to a local Unix wizard to fix this. Perhaps you are just using the wrong terminal type. For terminals that lack a "no flow control" mode, sometimes just giving lots of padding will prevent actual generation of flow control codes. You might as well try it. If you are really unlucky, your terminal is connected to the computer through a concentrator which sends XON/XOFF flow control to the computer, or it insists on sending flow control itself no matter how much padding you give it. Unless you can figure out how to turn flow control off on this concentrator (again, refer to your local wizard), you are screwed! You should have the terminal or concentrator replaced with a properly designed one. In the mean time, some drastic measures can make Emacs semi-work. You can make Emacs ignore C-s and C-q and let the operating system handle them. To do this on a per-session basis, just type M-x enable-flow-control RET. You will see a message that C-\ and C-^ are now translated to C-s and C-q. (Use the same command M-x enable-flow-control to turn *off* this special mode. It toggles flow control handling.) If C-\ and C-^ are inconvenient for you (for example, if one of them is the escape character of your terminal concentrator), you can choose other characters by setting the variables flow-control-c-s-replacement and flow-control-c-q-replacement. But choose carefully, since all other control characters are already used by emacs. IMPORTANT: if you type C-s by accident while flow control is enabled, Emacs output will freeze, and you will have to remember to type C-q in order to continue. If you work in an environment where a majority of terminals of a certain type are flow control hobbled, you can use the function 'enable-flow-control-on' to turn on this flow control avoidance scheme automatically. Here is an example: (enable-flow-control-on "vt200" "vt300" "vt101" "vt131") If this isn't quite correct (e.g. you have a mixture of flow-control hobbled and good vt200 terminals), you can still run enable-flow-control manually. I have no intention of ever redesigning the Emacs command set for the assumption that terminals use C-s/C-q flow control. XON/XOFF flow control technique is a bad design, and terminals that need it are bad merchandise and should not be purchased. Now that X is becoming widespread, XON/XOFF seems to be on the way out. If you can get some use out of GNU Emacs on inferior terminals, more power to you, but I will not make Emacs worse for properly designed systems for the sake of inferior systems. ** Control-S and Control-Q commands are ignored completely. For some reason, your system is using brain-damaged C-s/C-q flow control despite Emacs's attempts to turn it off. Perhaps your terminal is connected to the computer through a concentrator that wants to use flow control. You should first try to tell the concentrator not to use flow control. If you succeed in this, try making the terminal work without flow control, as described in the preceding section. If that line of approach is not successful, map some other characters into C-s and C-q using keyboard-translate-table. The example above shows how to do this with C-^ and C-\. ** Screen is updated wrong, but only on one kind of terminal. This could mean that the termcap entry you are using for that terminal is wrong, or it could mean that Emacs has a bug handling the combination of features specified for that terminal. The first step in tracking this down is to record what characters Emacs is sending to the terminal. Execute the Lisp expression (open-termscript "./emacs-script") to make Emacs write all terminal output into the file ~/emacs-script as well; then do what makes the screen update wrong, and look at the file and decode the characters using the manual for the terminal. There are several possibilities: 1) The characters sent are correct, according to the terminal manual. In this case, there is no obvious bug in Emacs, and most likely you need more padding, or possibly the terminal manual is wrong. 2) The characters sent are incorrect, due to an obscure aspect of the terminal behavior not described in an obvious way by termcap. This case is hard. It will be necessary to think of a way for Emacs to distinguish between terminals with this kind of behavior and other terminals that behave subtly differently but are classified the same by termcap; or else find an algorithm for Emacs to use that avoids the difference. Such changes must be tested on many kinds of terminals. 3) The termcap entry is wrong. See the file etc/TERMS for information on changes that are known to be needed in commonly used termcap entries for certain terminals. 4) The characters sent are incorrect, and clearly cannot be right for any terminal with the termcap entry you were using. This is unambiguously an Emacs bug, and can probably be fixed in termcap.c, tparam.c, term.c, scroll.c, cm.c or dispnew.c. ** Control-S and Control-Q commands are ignored completely on a net connection. Some versions of rlogin (and possibly telnet) do not pass flow control characters to the remote system to which they connect. On such systems, emacs on the remote system cannot disable flow control on the local system. Sometimes 'rlogin -8' will avoid this problem. One way to cure this is to disable flow control on the local host (the one running rlogin, not the one running rlogind) using the stty command, before starting the rlogin process. On many systems, "stty start u stop u" will do this. On some systems, use "stty -ixon" instead. Some versions of tcsh will prevent even this from working. One way around this is to start another shell before starting rlogin, and issue the stty command to disable flow control from that shell. If none of these methods work, the best solution is to type M-x enable-flow-control at the beginning of your emacs session, or if you expect the problem to continue, add a line such as the following to your .emacs (on the host running rlogind): (enable-flow-control-on "vt200" "vt300" "vt101" "vt131") See the entry about spontaneous display of I-search (above) for more info. ** Output from Control-V is slow. On many bit-map terminals, scrolling operations are fairly slow. Often the termcap entry for the type of terminal in use fails to inform Emacs of this. The two lines at the bottom of the screen before a Control-V command are supposed to appear at the top after the Control-V command. If Emacs thinks scrolling the lines is fast, it will scroll them to the top of the screen. If scrolling is slow but Emacs thinks it is fast, the usual reason is that the termcap entry for the terminal you are using does not specify any padding time for the 'al' and 'dl' strings. Emacs concludes that these operations take only as much time as it takes to send the commands at whatever line speed you are using. You must fix the termcap entry to specify, for the 'al' and 'dl', as much time as the operations really take. Currently Emacs thinks in terms of serial lines which send characters at a fixed rate, so that any operation which takes time for the terminal to execute must also be padded. With bit-map terminals operated across networks, often the network provides some sort of flow control so that padding is never needed no matter how slow an operation is. You must still specify a padding time if you want Emacs to realize that the operation takes a long time. This will cause padding characters to be sent unnecessarily, but they do not really cost much. They will be transmitted while the scrolling is happening and then discarded quickly by the terminal. Most bit-map terminals provide commands for inserting or deleting multiple lines at once. Define the 'AL' and 'DL' strings in the termcap entry to say how to do these things, and you will have fast output without wasted padding characters. These strings should each contain a single %-spec saying how to send the number of lines to be scrolled. These %-specs are like those in the termcap 'cm' string. You should also define the 'IC' and 'DC' strings if your terminal has a command to insert or delete multiple characters. These take the number of positions to insert or delete as an argument. A 'cs' string to set the scrolling region will reduce the amount of motion you see on the screen when part of the screen is scrolled. ** You type Control-H (Backspace) expecting to delete characters. Put 'stty dec' in your .login file and your problems will disappear after a day or two. The choice of Backspace for erasure was based on confusion, caused by the fact that backspacing causes erasure (later, when you type another character) on most display terminals. But it is a mistake. Deletion of text is not the same thing as backspacing followed by failure to overprint. I do not wish to propagate this confusion by conforming to it. For this reason, I believe 'stty dec' is the right mode to use, and I have designed Emacs to go with that. If there were a thousand other control characters, I would define Control-h to delete as well; but there are not very many other control characters, and I think that providing the most mnemonic possible Help character is more important than adapting to people who don't use 'stty dec'. If you are obstinate about confusing buggy overprinting with deletion, you can redefine Backspace in your .emacs file: (global-set-key "\b" 'delete-backward-char) You can probably access help-command via f1. ** Colors are not available on a tty or in xterm. Emacs 21 supports colors on character terminals and terminal emulators, but this support relies on the terminfo or termcap database entry to specify that the display supports color. Emacs looks at the "Co" capability for the terminal to find out how many colors are supported; it should be non-zero to activate the color support within Emacs. (Most color terminals support 8 or 16 colors.) If your system uses terminfo, the name of the capability equivalent to "Co" is "colors". In addition to the "Co" capability, Emacs needs the "op" (for "original pair") capability, which tells how to switch the terminal back to the default foreground and background colors. Emacs will not use colors if this capability is not defined. If your terminal entry doesn't provide such a capability, try using the ANSI standard escape sequence \E[00m (that is, define a new termcap/terminfo entry and make it use your current terminal's entry plus \E[00m for the "op" capability). Finally, the "NC" capability (terminfo name: "ncv") tells Emacs which attributes cannot be used with colors. Setting this capability incorrectly might have the effect of disabling colors; try setting this capability to '0' (zero) and see if that helps. Emacs uses the database entry for the terminal whose name is the value of the environment variable TERM. With 'xterm', a common terminal entry that supports color is 'xterm-color', so setting TERM's value to 'xterm-color' might activate the color support on an xterm-compatible emulator. Beginning with version 22.1, Emacs supports the --color command-line option which may be used to force Emacs to use one of a few popular modes for getting colors on a tty. For example, --color=ansi8 sets up for using the ANSI-standard escape sequences that support 8 colors. Some modes do not use colors unless you turn on the Font-lock mode. Some people have long ago set their '~/.emacs' files to turn on Font-lock on X only, so they won't see colors on a tty. The recommended way of turning on Font-lock is by typing "M-x global-font-lock-mode RET" or by customizing the variable 'global-font-lock-mode'. ** Colors are not available or messed up on TTY frames inside 'screen'. This can happen if you have COLORTERM=truecolor defined in the environment when Emacs starts, but your version of 'screen' doesn't actually support 24-bit true colors. The COLORTERM environment variable is supposed to be set to the value "truecolor" only if the terminal used by Emacs actually supports true color. Emacs does not have any means of verifying that this support is available, it takes the fact that the variable is defined to this value as an indication that true color support is, in fact, available, and uses color setting commands that COLORTERM=truecolor presumes, bypassing the usual Terminfo capabilities related to colors. Some text-mode terminals, such as GNOME Terminal, are known to set this environment variable, supposedly to announce their own support for true color; however the setting is then inherited by any other terminal emulators started from such a terminal, even though those other terminal emulators might not themselves support true color using the same commands as Emacs uses when it sees COLORTERM=truecolor. The solution is to either upgrade to a newer version of 'screen' (version 5.x or later reportedly supports true color), or to unset the COLORTERM variable before starting 'screen', and let Emacs use the color support provided by the terminal emulator as defined in the Terminfo database. ** Unexpected characters inserted into the buffer when you start Emacs. See e.g. This can happen when you start Emacs in -nw mode in an Xterm. For example, in the *scratch* buffer, you might see something like: 0;276;0c This is more likely to happen if you are using Emacs over a slow connection, and begin typing before Emacs is ready to respond. This occurs when Emacs tries to query the terminal to see what capabilities it supports, and gets confused by the answer. To avoid it, set xterm-extra-capabilities to a value other than 'check' (the default). See that variable's documentation (in term/xterm.el) for more details. ** Incorrect or corrupted display of some Unicode characters *** Linux console problems with double-width characters If possible, we recommend running Emacs inside fbterm, when in a Linux console (see the node "Emacs in a Linux console" in the Emacs FAQ). Most Unicode characters should then be displayed correctly. If that is not possible, the following may be useful to alleviate the problem of displaying Unicode characters in a raw console. The Linux console declares UTF-8 encoding, but supports only a limited number of Unicode characters, and can cause Emacs produce corrupted or garbled display with some unusual characters and sequences. Emacs 28 and later by default disables 'auto-composition-mode' on this console, for that reason, but this might not be enough. One known problem with this console is that zero-width and double-width characters are displayed incorrectly (as a single-column characters), and that causes the cursor to be out of sync with the actual display. One way of working around this is to use the display-table feature to display the problematic characters as some other, less problematic ones. Here's an example of setting up the standard display table to show the U+01F64F PERSON WITH FOLDED HANDS character as a diamond with a special face: (or standard-display-table (setq standard-display-table (make-display-table))) (aset standard-display-table #x1f64f (vector (make-glyph-code #xFFFD 'escape-glyph))) Similar setup can be done with any other problematic character. If the console cannot even display the U+FFFD REPLACEMENT CHARACTER, you can use some ASCII character instead, like '?'; it will stand out due to the 'escape-glyph' face. The disadvantage of this method is that all such characters will look the same on display, and the only way of knowing what is the real codepoint in the buffer is to go to the character and type "C-u C-x =". *** Messed-up display on the Kitty text terminal This terminal has its own peculiar ideas about display of unusual characters. For example, it hides the U+00AD SOFT HYPHEN characters on display, which messes up Emacs cursor addressing, since Emacs doesn't know these characters are effectively treated as zero-width characters. One way of working around such "hidden" characters is to tell Emacs to display them as zero-width: (aset glyphless-char-display #xAD 'zero-width) Another possibility is to use display-table to display SOFT HYPHEN as a regular ASCII dash character '-': (or standard-display-table (setq standard-display-table (make-display-table))) (aset standard-display-table #xAD (vector (make-glyph-code ?- 'escape-glyph))) Another workaround is to set 'nobreak-char-ascii-display' to a non-nil value, which will cause any non-ASCII space and hyphen characters to be displayed as their ASCII counterparts, with a special face. Kitty also differs from many other character terminals in how it handles character compositions. As one example, Emoji sequences that begin with a non-Emoji character and end in U+FE0F VARIATION SELECTOR 16 should be composed into an Emoji glyph; Kitty assumes that all such Emoji glyphs have 2-column width, whereas Emacs and many other text terminals display them as 1-column glyphs. Again, this causes cursor addressing to get out of sync and eventually messes up the display. One possible workaround for problems caused by character composition is to turn off 'auto-composition-mode' on Kitty terminals, e.g. by customizing the 'auto-composition-mode' variable to have as value a string that the 'tty-type' function returns on those terminals. *** Display artifacts on the Alacritty text terminal This terminal is known to cause problems with Emoji sequences: when displaying them, the Emacs text-mode frame could show gaps and other visual artifacts. The solution is to disable 'auto-composition-mode' on these terminals, for example, like this: (setq auto-composition-mode "alacritty") This disables 'auto-composition-mode' on frames that display on terminals of this type. * Runtime problems specific to individual Unix variants ** GNU/Linux *** GNU/Linux: profiler-report outputs nothing. A few versions of the Linux kernel have timer bugs that break CPU profiling; see Bug#34235. To fix the problem, upgrade to one of the kernel versions 4.14.97, 4.19.19, or 4.20.6, or later. *** GNU/Linux: Remote access to CVS with SSH causes file corruption. If you access a remote CVS repository via SSH, files may be corrupted due to bad interaction between CVS, SSH, and libc. To fix the problem, save the following script into a file, make it executable, and set CVS_RSH environment variable to the file name of the script: #!/bin/bash exec 2> >(exec cat >&2 2>/dev/null) exec ssh "$@" *** GNU/Linux: Truncated svn annotate output with SSH. https://debbugs.gnu.org/7791 The symptoms are: you are accessing a svn repository over SSH. You use vc-annotate on a large (several thousand line) file, and the result is truncated around the 1000 line mark. It works fine with other access methods (e.g. http), or from outside Emacs. This may be a similar libc/SSH issue to the one mentioned above for CVS. A similar workaround seems to be effective: create a script with the same contents as the one used above for CVS_RSH, and set the SVN_SSH environment variable to point to it. *** GNU/Linux: After upgrading to a newer version of Emacs, the Meta key stops working. This was reported to happen on a GNU/Linux system distributed by Mandrake. The reason is that the previous version of Emacs was modified by Mandrake to make the Alt key act as the Meta key, on a keyboard where the Windows key is the one which produces the Meta modifier. A user who started using a newer version of Emacs, which was not hacked by Mandrake, expected the Alt key to continue to act as Meta, and was astonished when that didn't happen. The solution is to find out what key on your keyboard produces the Meta modifier, and use that key instead. Try all of the keys to the left and to the right of the space bar, together with the 'x' key, and see which combination produces "M-x" in the echo area. You can also use the 'xmodmap' utility to show all the keys which produce a Meta modifier: xmodmap -pk | grep -Ei "meta|alt" A more convenient way of finding out which keys produce a Meta modifier is to use the 'xkbprint' utility, if it's available on your system: xkbprint 0:0 /tmp/k.ps This produces a PostScript file '/tmp/k.ps' with a picture of your keyboard; printing that file on a PostScript printer will show what keys can serve as Meta. The 'xkeycaps' also shows a visual representation of the current keyboard settings. It also allows modifying them. *** GNU/Linux: slow startup on Linux-based GNU systems. People using systems based on the Linux kernel sometimes report that startup takes 10 to 15 seconds longer than 'usual'. This is because Emacs looks up the host name when it starts. Normally, this takes negligible time; the extra delay is due to improper system configuration. This problem can occur for both networked and non-networked machines. Here is how to fix the configuration. It requires being root. **** Networked Case. First, make sure the files '/etc/hosts' and '/etc/host.conf' both exist. The first line in the '/etc/hosts' file should look like this (replace HOSTNAME with your host name): 127.0.0.1 HOSTNAME Also make sure that the '/etc/host.conf' files contains the following lines: order hosts, bind multi on Any changes, permanent and temporary, to the host name should be indicated in the '/etc/hosts' file, since it acts a limited local database of addresses and names (e.g., some SLIP connections dynamically allocate ip addresses). **** Non-Networked Case. The solution described in the networked case applies here as well. However, if you never intend to network your machine, you can use a simpler solution: create an empty '/etc/host.conf' file. The command 'touch /etc/host.conf' suffices to create the file. The '/etc/hosts' file is not necessary with this approach. *** GNU/Linux: Emacs on a tty switches the cursor to large blinking block. This was reported to happen on some GNU/Linux systems which use ncurses version 5.0, but could be relevant for other versions as well. These versions of ncurses come with a 'linux' terminfo entry, where the "cvvis" capability (termcap "vs") is defined as "\E[?25h\E[?8c" (show cursor, change size). This escape sequence switches on a blinking hardware text-mode cursor whose size is a full character cell. This blinking cannot be stopped, since a hardware cursor always blinks. A work-around is to redefine the "cvvis" capability so that it enables a *software* cursor. The software cursor works by inverting the colors of the character at point, so what you see is a block cursor that doesn't blink. For this to work, you need to redefine the "cnorm" capability as well, so that it operates on the software cursor instead of the hardware cursor. To this end, run "infocmp linux > linux-term", edit the file 'linux-term' to make both the "cnorm" and "cvvis" capabilities send the sequence "\E[?25h\E[?17;0;64c", and then run "tic linux-term" to produce a modified terminfo entry. Alternatively, if you want a blinking underscore as your Emacs cursor, set the 'visible-cursor' variable to nil in your ~/.emacs: (setq visible-cursor nil) Still other way is to change the "cvvis" capability to send the "\E[?25h\E[?0c" command. ** FreeBSD *** FreeBSD: Getting a Meta key on the console. By default, neither Alt nor any other key acts as a Meta key on FreeBSD, but this can be changed using kbdcontrol(1). Dump the current keymap to a file with the command $ kbdcontrol -d >emacs.kbd Edit emacs.kbd, and give the key you want to be the Meta key the definition 'meta'. For instance, if your keyboard has a "Windows" key with scan code 105, change the line for scan code 105 in emacs.kbd to look like this 105 meta meta meta meta meta meta meta meta O to make the Windows key the Meta key. Load the new keymap with $ kbdcontrol -l emacs.kbd ** HP-UX *** HP/UX : Shell mode gives the message, "`tty`: Ambiguous". christos@theory.tn.cornell.edu says: The problem is that in your .cshrc you have something that tries to execute 'tty'. If you are not running the shell on a real tty then tty will print "not a tty". Csh expects one word in some places, but tty is giving it back 3. The solution is to add a pair of quotes around `tty` to make it a single word: if (`tty` == "/dev/console") should be changed to: if ("`tty`" == "/dev/console") Even better, move things that set up terminal sections out of .cshrc and into .login. *** HP/UX: 'Pid xxx killed due to text modification or page I/O error'. On HP/UX, you can get that error when the Emacs executable is on an NFS file system. HP/UX responds this way if it tries to swap in a page and does not get a response from the server within a timeout whose default value is just ten seconds. If this happens to you, extend the timeout period. *** HP/UX: The right Alt key works wrong on German HP keyboards (and perhaps other non-English HP keyboards too). This is because HP-UX defines the modifiers wrong in X. Here is a shell script to fix the problem; be sure that it is run after VUE configures the X server. xmodmap 2> /dev/null - << EOF keysym Alt_L = Meta_L keysym Alt_R = Meta_R EOF xmodmap - << EOF clear mod1 keysym Mode_switch = NoSymbol add mod1 = Meta_L keysym Meta_R = Mode_switch add mod2 = Mode_switch EOF *** HP/UX: Emacs does not recognize the AltGr key. To fix this, set up a file ~/.dt/sessions/sessionetc with executable rights, containing this text: -------------------------------- xmodmap 2> /dev/null - << EOF keysym Alt_L = Meta_L keysym Alt_R = Meta_R EOF xmodmap - << EOF clear mod1 keysym Mode_switch = NoSymbol add mod1 = Meta_L keysym Meta_R = Mode_switch add mod2 = Mode_switch EOF -------------------------------- *** HP/UX 11.0: Emacs makes HP/UX 11.0 crash. This is a bug in HPUX; HPUX patch PHKL_16260 is said to fix it. ** AIX *** AIX: Trouble using ptys. People often install the pty devices on AIX incorrectly. Use 'smit pty' to reinstall them properly. *** AIXterm: Your Delete key sends a Backspace to the terminal. The solution is to include in your .Xdefaults the lines: *aixterm.Translations: #override BackSpace: string(0x7f) aixterm*ttyModes: erase ^? This makes your Backspace key send DEL (ASCII 127). *** AIX: If linking fails because libXbsd isn't found, check if you are compiling with the system's 'cc' and CFLAGS containing '-O5'. If so, you have hit a compiler bug. Please make sure to re-configure Emacs so that it isn't compiled with '-O5'. ** Solaris We list bugs in current versions here. See also the section on legacy systems. *** On Solaris 10, running 'configure' with "/bin/sh" produces errors. The "/bin/sh" shell on Solaris is an ancient and non-POSIX shell, so we recommend not to use it. The Emacs 'configure' script should find an appropriate shell and re-exec itself with that shell, unless you force it to use "/bin/sh" by using "CONFIG_SHELL=/bin/sh" on the 'configure' command line. So either don't use CONFIG_SHELL, or, if you'd rather pick the shell yourself, choose "/bin/bash" or "/bin/ksh" or "/usr/xpg4/bin/sh" instead. *** On Solaris 10 sparc, Emacs crashes during the build while saving state. This was observed for Emacs 28.1 on Solaris 10 32-bit sparc, with Oracle Developer Studio 12.6 (Sun C 5.15). The failure was intermittent, and running GNU Make a second time would typically finish the build. *** On Solaris 10, Emacs crashes during the build process. (This applies only with './configure --with-unexec=yes', which is rare.) This was reported for Emacs 25.2 on i386-pc-solaris2.10 with Sun Studio 12 (Sun C 5.9) and with Oracle Developer Studio 12.6 (Sun C 5.15), and intermittently for sparc-sun-solaris2.10 with Oracle Developer Studio 12.5 (Sun C 5.14). Disabling compiler optimization seems to fix the bug, as does upgrading the Solaris 10 operating system to Update 11. The cause of the bug is unknown: it may be that Emacs's archaic memory-allocation scheme is not compatible with slightly-older versions of Solaris and/or Oracle Studio, or it may be something else. Since the cause is not known, possibly the bug is still present in newer versions of Emacs, Oracle Studio, and/or Solaris. See Bug#26638. *** On Solaris, C-x doesn't get through to Emacs when you use the console. This is a Solaris feature (at least on Intel x86 cpus). Type C-r C-r C-t, to toggle whether C-x gets through to Emacs. * Runtime problems specific to MS-Windows ** Emacs with native compilation crashes/signals errors accessing *.eln files This is known to be caused by some flavors of Windows anti-virus software. The problem could manifest itself in several ways: . Emacs crashes when it tries to load certain *.eln files . Emacs signals an error when it tries to load some *.eln files, claiming they are "not GPL compatible" . Emacs crashes during GC when it calls unload_comp_unit This was specifically reported to happen with *.eln files in directories under the C:\Users directory, which is where Emacs on Windows places the emulated HOME directory, and thus also the ~/.emacs.d/eln-cache directory holding the *.eln files compiled during Emacs sessions (as opposed to those that came precompiled and were installed with the rest of Emacs distribution). If you cannot disable such anti-virus software or switch to another one, you could use the following workarounds: . Define the HOME environment variable to point to a directory outside of the C:\Users tree, then copy/move your ~/.emacs.d directory to that new home directory. . Move all the *.eln files from ~/.emacs.d/eln-cache to a directory out of the C:\Users tree, and customize Emacs to use that directory for *.eln files. This requires calling the function startup-redirect-eln-cache in your init file, to force Emacs to write *.eln files compiled at run time to that directory. . Delete all *.eln files in your ~/.emacs.d/eln-cache directory, and then disable run-time native compilation. To disable native compilation, set the variables native-comp-jit-compilation and native-comp-enable-subr-trampolines to nil. . Install Emacs built without native compilation. With any of the above methods, you'd need to restart Emacs (and preferably also your Windows system) after making the changes, to have them take effect. *** MinGW64 Emacs built with -D_FORTIFY_SOURCE=2 misbehaves Using this preprocessor option when building Emacs with MinGW64 produces an Emacs binary that behaves incorrectly. In particular, running asynchronous shell command, e.g., with 'M-&', causes Emacs to use 100% of CPU and start allocating a lot of memory. For the same reason, asynchronous native-compilation will hang Emacs (which could wedge Emacs during startup, if your Emacs is configured to download and install packages via package.el every startup). 'M-x run-python', 'M-x shell', and similar commands also hang. Other commands might also cause high CPU and/or memory usage. The workaround is to rebuild Emacs without the -D_FORTIFY_SOURCE=2 option. ** Emacs on Windows 9X requires UNICOWS.DLL If that DLL is not available, Emacs will display an error dialog stating its absence, and refuse to run. This is because Emacs 24.4 and later uses functions whose non-stub implementation is only available in UNICOWS.DLL, which implements the Microsoft Layer for Unicode on Windows 9X, or "MSLU". This article on MSDN: https://web.archive.org/web/20151224032644/https://msdn.microsoft.com/en-us/goglobal/bb688166.aspx includes a short description of MSLU and a link where it can be downloaded. ** Emacs refuses to start on Windows 9X because ctime64 function is missing This is a sign that Emacs was compiled with MinGW runtime version 4.0.x or later. These versions of runtime call in their startup code the ctime64 function, which does not exist in MSVCRT.DLL, the C runtime shared library, distributed with Windows 9X. A workaround is to build Emacs with MinGW runtime 3.x (the latest version is 3.20). ** A few seconds delay is seen at startup and for many file operations This happens when the Net Logon service is enabled. During Emacs startup, this service issues many DNS requests looking up for the Windows Domain Controller. When Emacs accesses files on networked drives, it automatically logs on the user into those drives, which again causes delays when Net Logon is running. The solution seems to be to disable Net Logon with this command typed at the Windows shell prompt: net stop netlogon To start the service again, type "net start netlogon". (You can also stop and start the service from the Computer Management application, accessible by right-clicking "My Computer" or "Computer", selecting "Manage", then clicking on "Services".) ** Emacs crashes when exiting the Emacs session This was reported to happen when some optional DLLs, such as those used for displaying images or the GnuTLS library or zlib compression library, which are loaded on-demand, have a runtime dependency on the libgcc DLL, libgcc_s_dw2-1.dll. The reason seems to be a bug in libgcc which rears its ugly head whenever the libgcc DLL is loaded after Emacs has started. One solution for this problem is to find an alternative build of the same optional library that does not depend on the libgcc DLL. Another possibility is to rebuild Emacs with the -shared-libgcc switch, which will force Emacs to load libgcc_s_dw2-1.dll on startup, ahead of any optional DLLs loaded on-demand later in the session. ** File selection dialog opens in incorrect directories Invoking the file selection dialog on Windows 7 or later shows a directory that is different from what was passed to 'read-file-name' or 'x-file-dialog' via their arguments. This is due to a deliberate change in behavior of the file selection dialogs introduced in Windows 7. It is explicitly described in the MSDN documentation of the GetOpenFileName API used by Emacs to pop up the file selection dialog. For the details, see https://msdn.microsoft.com/en-us/library/windows/desktop/ms646839%28v=vs.85%29.aspx The dialog shows the last directory in which the user selected a file in a previous invocation of the dialog with the same initial directory. You can reset this "memory" of that directory by invoking the file selection dialog with a different initial directory. ** PATH can contain unexpanded environment variables Old releases of TCC (version 9) and 4NT (up to version 8) do not correctly expand App Paths entries of type REG_EXPAND_SZ. When Emacs is run from TCC and such an entry exists for emacs.exe, exec-path will contain the unexpanded entry. This has been fixed in TCC 10. For more information, see bug#2062. ** Setting w32-pass-rwindow-to-system and w32-pass-lwindow-to-system to nil does not prevent the Start menu from popping up when the left or right "Windows" key is pressed. This was reported to happen when XKeymacs is installed. At least with XKeymacs Version 3.47, deactivating XKeymacs when Emacs is active is not enough to avoid its messing with the keyboard input. Exiting XKeymacs completely is reported to solve the problem. ** Pasting from Windows clipboard into Emacs doesn't work. This was reported to be the result of an anti-virus software blocking the clipboard-related operations when a Web browser is open, for security reasons. The solution is to close the Web browser while working in Emacs, or to add emacs.exe to the list of applications that are allowed to use the clipboard when the Web browser is open. ** "Pinning" Emacs to the taskbar doesn't work on Windows 10 "Doesn't work" here means that if you invoke Emacs by clicking on the pinned icon, a separate button appears on the taskbar, instead of the expected effect of the icon you clicked on being converted to that button. This is due to a bug in early versions of Windows 10, reportedly fixed in build 1511 of Windows 10 (a.k.a. "Windows 10 SP1"). If you cannot upgrade, read the work-around described below. First, be sure to edit the Properties of the pinned icon to invoke runemacs.exe, not emacs.exe. (The latter will cause an extra cmd window to appear when you invoke Emacs from the pinned icon.) But the real cause of the problem is the fact that the pinned icon (which is really a shortcut in a special directory) lacks a unique application-defined Application User Model ID (AppUserModelID) that identifies the current process to the taskbar. This identifier allows an application to group its associated processes and windows under a single taskbar button. Emacs on Windows specifies a unique AppUserModelID when it starts, but Windows 10, unlike previous versions of MS-Windows, does not propagate that ID to the pinned icon. To work around this, use some utility, such as 'win7appid', to set the AppUserModelID of the pinned icon to the string "Gnu.Emacs". The shortcut files corresponding to icons you pinned are stored by Windows in the following subdirectory of your user's directory (by default C:\Users\\): AppData\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar Look for the file 'emacs.lnk' there. ** Emacs exits with "X protocol error" when run with an X server for MS-Windows. A certain X server for Windows had a bug which caused this. Supposedly the newer 32-bit version of this server doesn't have the problem. ** Emacs crashes when opening a file with a UNC path and rails-mode is loaded. Loading rails-mode seems to interfere with UNC path handling. This has been reported as a bug against both Emacs and rails-mode, so look for an updated rails-mode that avoids this crash, or avoid using UNC paths if using rails-mode. ** M-x term does not work on MS-Windows. TTY emulation on Windows is undocumented, and programs such as stty which are used on POSIX platforms to control tty emulation do not exist for native windows terminals. ** Using create-fontset-from-ascii-font or the --font startup parameter with a Chinese, Japanese or Korean font leads to display problems. Use a Latin-only font as your default font. If you want control over which font is used to display Chinese, Japanese or Korean character, use create-fontset-from-fontset-spec to define a fontset. ** Frames are not refreshed while dialogs or menus are displayed This means no redisplay while the File or Font dialog or a pop-up menu is displayed. This also means tooltips with help text for pop-up menus are not displayed at all (except in a TTY session, where the help text is shown in the echo area). This is because message handling under Windows is synchronous, so we cannot handle repaint (or any other) messages while waiting for a system function, which popped up the menu/dialog, to return the result of the dialog or pop-up menu interaction. ** Display problems with ClearType method of smoothing When "ClearType" method is selected as the "method to smooth edges of screen fonts" (in Display Properties, Appearance tab, under "Effects"), there are various problems related to display of characters: Bold fonts can be hard to read, small portions of some characters could appear chopped, etc. This happens because, under ClearType, characters are drawn outside their advertised bounding box. Emacs 21 disabled the use of ClearType, whereas Emacs 22 allows it and has some code to enlarge the width of the bounding box. Apparently, this display feature needs more changes to get it 100% right. A workaround is to disable ClearType. ** Cursor is displayed as a thin vertical bar and cannot be changed This is known to happen if the Windows Magnifier is turned on before the Emacs session starts. The Magnifier affects the cursor shape and prevents any changes to it by setting the 'cursor-type' variable or frame parameter. The solution is to log off and on again, and then start the Emacs session only after turning the Magnifier off. To turn the Windows Magnifier off, click "Start->All Programs", or "All Apps", depending on your Windows version, then select "Accessibility" and click "Magnifier". In the Magnifier Settings dialog that opens, click "Exit". ** Problems with mouse-tracking and focus management There are problems with display if mouse-tracking is enabled and the mouse is moved off a frame, over another frame then back over the first frame. A workaround is to click the left mouse button inside the frame after moving back into it. Some minor flickering still persists during mouse-tracking, although not as severely as in 21.1. An inactive cursor remains in an active window after the Windows Manager driven switch of the focus, until a key is pressed. ** Problems with Windows input methods Some of the Windows input methods cause the keyboard to send characters encoded in the appropriate coding system (e.g., ISO 8859-1 for Latin-1 characters, ISO 8859-8 for Hebrew characters, etc.). To make these input methods work with Emacs on Windows 9X, you might need to set the keyboard coding system to the appropriate value after you activate the Windows input method. For example, if you activate the Hebrew input method, type this: C-x RET k hebrew-iso-8bit RET In addition, to use these Windows input methods, you might need to set your "Language for non-Unicode programs" (on Windows XP, this is on the Advanced tab of Regional Settings) to the language of the input method. To bind keys that produce non-ASCII characters with modifiers, you must specify raw byte codes. For instance, if you want to bind META-a-grave to a command, you need to specify this in your '~/.emacs': (global-set-key [?\M-\340] ...) The above example is for the Latin-1 environment where the byte code of the encoded a-grave is 340 octal. For other environments, use the encoding appropriate to that environment. ** Problems with the %b format specifier for format-time-string The %b specifier for format-time-string does not produce abbreviated month names with consistent widths for some locales on some versions of Windows. This is caused by a deficiency in the underlying system library function. ** Non-US time zones. Many non-US time zones are implemented incorrectly. This is due to over-simplistic handling of daylight savings switchovers by the Windows libraries. ** Files larger than 4GB report wrong size in a 32-bit Windows build Files larger than 4GB cause overflow in the size (represented as a 32-bit integer) reported by 'file-attributes'. This affects Dired as well, since the Windows port uses a Lisp emulation of 'ls', which relies on 'file-attributes'. ** Playing sound doesn't support the :data method Sound playing is not supported with the ':data DATA' key-value pair. You _must_ use the ':file FILE' method. ** Typing Alt-Shift has strange effects on MS-Windows. This combination of keys is a command to change keyboard layout. If you proceed to type another non-modifier key before you let go of Alt and Shift, the Alt and Shift act as modifiers in the usual way. A more permanent work around is to change it to another key combination, or disable it in the "Regional and Language Options" applet of the Control Panel. (The exact sequence of mouse clicks in the "Regional and Language Options" applet needed to find the key combination that changes the keyboard layout depends on your Windows version; for XP, in the Languages tab, click "Details" and then "Key Settings".) ** Interrupting Cygwin port of Bash from Emacs doesn't work. Cygwin 1.x builds of the ported Bash cannot be interrupted from the MS-Windows version of Emacs. This is due to some change in the Bash port or in the Cygwin library which apparently make Bash ignore the keyboard interrupt event sent by Emacs to Bash. (Older Cygwin ports of Bash, up to b20.1, did receive SIGINT from Emacs.) ** Accessing remote files with ange-ftp hangs the MS-Windows version of Emacs. If the FTP client is the Cygwin port of GNU 'ftp', this appears to be due to some bug in the Cygwin DLL or some incompatibility between it and the implementation of asynchronous subprocesses in the Windows port of Emacs. Specifically, some parts of the FTP server responses are not flushed out, apparently due to buffering issues, which confuses ange-ftp. The solution is to downgrade to an older version of the Cygwin DLL (version 1.3.2 was reported to solve the problem), or use the stock Windows FTP client, usually found in the 'C:\WINDOWS' or 'C:\WINNT' directory. To force ange-ftp use the stock Windows client, set the variable 'ange-ftp-ftp-program-name' to the absolute file name of the client's executable. For example: (setq ange-ftp-ftp-program-name "c:/windows/ftp.exe") If you want to stick with the Cygwin FTP client, you can work around this problem by putting this in your '.emacs' file: (setq ange-ftp-ftp-program-args '("-i" "-n" "-g" "-v" "--prompt" "") ** lpr commands don't work on MS-Windows with some cheap printers. This problem may also strike other platforms, but the solution is likely to be a global one, and not Emacs specific. Many cheap inkjet, and even some cheap laser printers, do not print plain text anymore, they will only print through graphical printer drivers. A workaround on MS-Windows is to use Windows's basic built in editor to print (this is possibly the only useful purpose it has): (setq printer-name "") ; notepad takes the default (setq lpr-command "notepad") ; notepad (setq lpr-switches nil) ; not needed (setq lpr-printer-switch "/P") ; run notepad as batch printer ** Antivirus software interacts badly with the MS-Windows version of Emacs. The usual manifestation of these problems is that subprocesses don't work or even wedge the entire system. In particular, "M-x shell RET" was reported to fail to work. But other commands also sometimes don't work when an antivirus package is installed. The solution is to switch the antivirus software to a less aggressive mode (e.g., disable the "auto-protect" feature), or even uninstall or disable it entirely. ** Pressing the mouse button on MS-Windows does not give a mouse-2 event. This is usually a problem with the mouse driver. Because most Windows programs do not do anything useful with the middle mouse button, many mouse drivers allow you to define the wheel press to do something different. Some drivers do not even have the option to generate a middle button press. In such cases, setting the wheel press to "scroll" sometimes works if you press the button twice. Trying a generic mouse driver might help. One particular situation where this happens is when you have "Microsoft Intellipoint" installed, which runs the program ipoint.exe. The fix is reportedly to uninstall this software. ** Scrolling the mouse wheel on MS-Windows always scrolls the top window. This is another common problem with mouse drivers. Instead of generating scroll events, some mouse drivers try to fake scroll bar movement. But they are not intelligent enough to handle multiple scroll bars within a frame. Trying a generic mouse driver might help. ** Mail sent through Microsoft Exchange in some encodings appears to be mangled and is not seen correctly in Rmail or Gnus. We don't know exactly what happens, but it isn't an Emacs problem in cases we've seen. ** On MS-Windows, you cannot use the right-hand ALT key and the left-hand CTRL key together to type a Control-Meta character. This is a consequence of a misfeature beyond Emacs's control. Under Windows, the AltGr key on international keyboards generates key events with the modifiers Right-Alt and Left-Ctrl. Since Emacs cannot distinguish AltGr from an explicit Right-Alt and Left-Ctrl combination, whenever it sees Right-Alt and Left-Ctrl it assumes that AltGr has been pressed. The variable 'w32-recognize-altgr' can be set to nil to tell Emacs that AltGr is really Ctrl and Alt. ** Under some X-servers running on MS-Windows, Emacs's display is incorrect. The symptoms are that Emacs does not completely erase blank areas of the screen during scrolling or some other screen operations (e.g., selective display or when killing a region). M-x recenter will cause the screen to be completely redisplayed and the "extra" characters will disappear. This is known to occur under Exceed 6, and possibly earlier versions as well; it is reportedly solved in version 6.2.0.16 and later. The problem lies in the X-server settings. There are reports that you can solve the problem with Exceed by running 'Xconfig' from within NT, choosing "X selection", then un-checking the boxes "auto-copy X selection" and "auto-paste to X selection". If this does not work, please inform bug-gnu-emacs@gnu.org. Then please call support for your X-server and see if you can get a fix. If you do, please send it to bug-gnu-emacs@gnu.org so we can list it here. * Runtime problems specific to Cygwin ** Fork failures in a build with native compilation To prevent fork failures, shared libraries on Cygwin need to be rebased occasionally, for the reasons explained here: https://cygwin.com/cygwin-ug-net/highlights.html#ov-hi-process-problems This includes the .eln files produced by an Emacs built with native compilation. Rebasing is handled by Cygwin's autorebase postinstall script every time you run the Cygwin setup program (which you should do with no Cygwin processes running). This script knows about the .eln files installed in the standard places (e.g., /usr/lib/emacs/28.1/native-lisp), but it does not know about those in your user cache (e.g., /home//.emacs.d/eln-cache). In order for these to be automatically rebased, you must create a file /var/lib/rebase/userpath.d/ with one line for each directory containing .eln files. If you are running an installed Emacs, it should suffice to list your cache directory. For example, if there is an Emacs user "kbrown", then there should be a file /var/lib/rebase/userpath.d/kbrown containing the single line /home/kbrown/.emacs.d/eln-cache If you are running an Emacs that you have built but not installed, then you will need an additional line giving the path to the native-lisp subdirectory of your build directory. If more than one user will be using Emacs on your system, there should be a file like this for each user. Rebasing is not currently done when new .eln files are created, so fork failures are still possible between runs of Cygwin's setup program. If you ever see a fork failure whose error message refers to a .eln file, you should be able to fix it temporarily by exiting emacs and issuing the command find ~/.emacs.d/eln-cache -name '*.eln' | rebase -O -T - This is called an "ephemeral" rebase. Again, if you are running an Emacs that has not been installed, you need to add the native-lisp subdirectory of your build directory to this command. Alternatively, stop all Cygwin processes and run Cygwin's setup program to let the autorebase postinstall script run. It is hoped that the measures above will make native compilation usable on 64-bit Cygwin, with only an occasional minor annoyance. In the 32-bit case, however, the limited address space makes frequent fork failures extremely likely. It is therefore strongly recommended that you not build Emacs with native compilation on 32-bit Cygwin. Indeed, the configure script will not allow this unless you use the --with-cygwin32-native-compilation option. See bug#50666 (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=50666) for further discussion. * Runtime problems specific to macOS ** Error message about malicious software when opening Emacs on macOS When opening Emacs, you may see an error message saying something like this: "Emacs" can't be opened because Apple cannot check it for malicious software. This software needs to be updated. Contact the developer for more information. The reason is that Apple incorrectly catalogs Emacs as potentially malicious software and thus shows this error message. To avoid this alert, open Finder, go to Applications, control-click the Emacs app icon, and then choose Open. This adds a security exception for Emacs and from now on you should be able to open it by double-clicking on its icon, like any other app. ** Error message about color list unarchiver when starting Emacs on macOS The error message looks like this: Failed to initialize color list unarchiver: Error Domain=NSCocoaErrorDomain Code=4864 "*** -[NSKeyedUnarchiver _initForReadingFromData:error:throwLegacyExceptions:]: non-keyed archive cannot be decoded by NSKeyedUnarchiver" UserInfo={NSDebugDescription=*** -[NSKeyedUnarchiver _initForReadingFromData:error:throwLegacyExceptions:]: non-keyed archive cannot be decoded by NSKeyedUnarchiver} After showing this message, Emacs usually works normally. The usual reason for this is that the color file, ~/Library/Colors/Emacs.clr, is stale or corrupted. The solution is to delete that file and restart Emacs. ** macOS doesn't come with libxpm, so only XPM3 is supported. Libxpm is available for macOS as part of the XQuartz project. ** Synthetic fonts on macOS Synthetic bold looks thinner if the background is darker than the foreground and font smoothing is turned on. In such cases, you can turn off synthetic bold for particular fonts and use overstriking instead by customizing the variable 'face-ignored-fonts'. For instance, if the problem is with the Monaco font, you could put something like the following in your init file: (push "\\`-[^-]*-monaco-bold-" face-ignored-fonts) ** Native Compilation on macOS Native compilation requires the libgccjit library to be installed and its path available to Emacs. Errors such as: libgccjit.so: error: error invoking gcc driver Error: Internal native compiler error failed to compile indicate Emacs can't find the library in running time. One can set the "LIBRARY_PATH" environment variable in the early initialization file; for example: (setenv "LIBRARY_PATH" (string-join '("/usr/local/opt/gcc/lib/gcc/11" "/usr/local/opt/libgccjit/lib/gcc/11" "/usr/local/opt/gcc/lib/gcc/11/gcc/x86_64-apple-darwin20/11.2.0") ":")) * Runtime problems specific to PGTK build ** Whether a display server is available cannot be automatically detected. When started with no arguments from a text terminal and in an environment where no display server is specified, Emacs will print: $ emacs (emacs:3988): Gtk-WARNING **: 19:19:10.887: cannot open display: and exit. This is a byproduct of GTK's not providing any means of probing for a display connection before committing to opening one, and cannot be addressed by Emacs. Rather, users must expressly request a text mode session: $ emacs -nw [...] ** SECONDARY selections don't work on Wayland. This is because the SECONDARY selection is not implemented by the Wayland compositor being used. A workaround is to use other kinds of selections. ** Giant tool bar icons are displayed in some cases This is because some icon themes (such as the KDE Breeze icon theme) have several incorrectly sized icons, which also causes the toolbar to expand uncontrollably. The fix is to switch to a different icon theme, or to use Emacs's own toolbar icons by placing: (setq x-gtk-stock-map nil) in your early-init.el. ** Some modifier keys doesn't work if Emacs is started in a systemd unit file. Environment variables may be different if there is a difference in the behavior of keys between when started in the systemd unit file and when started from the command line. Especially, PGTK Emacs needs environment variables LANG and GTK_IM_MODULE. ** 'set-mouse-position' does nothing. GTK does not allow programs to warp the pointer anymore. There is nothing that can be done about this problem. ** Certain keys such as 'C-S-u' are not reported correctly. Some keys with modifiers such as Shift and Control might not be reported correctly due to incorrectly written GTK input method modules. This is known to happen to 'C-S-u' and 'C->', which are misreported as 'C-u' and '>'. To disable the use of GTK input methods, evaluate: (pgtk-use-im-context nil) This will also cause system input methods and features such as the Compose key to stop working. On X Windows, users should not use Emacs configured with PGTK, since this and many other problems do not exist on the regular X builds. ** On occasion, menus cannot be activated by touch screen events. Menus might not be displayed after a mode-line item, or another command that produces a menu, is activated by touch screen events. This is the product of several bugs or misdesigns in the GDK Wayland backend which cannot be circumvented by Emacs. Specifically, Wayland denies clients that cannot provide a sufficiently recent event serial number the ability to display pop-up windows, but GDK only considers the serial numbers of touch screen events when their touch sequences remain active, and, as touch screen activity is not registered by Emacs until after the toolkit's delivery of touch sequences completes, by the time `x-popup-menu' is called, the only eligible event serials are those of the last keyboard event and the last mouse event, which will not suffice if Wayland has received pop-up or drag-and-drop requests from other clients since their generation. * Runtime problems specific to Android ** Text displayed in the default monospace font looks horrible. TrueType fonts incorporate instruction code executed by the font scaler (the component responsible for transforming outlines into bitmap images capable of being displayed onscreen) to align features of each glyph to pixel boundaries while maintaining their shape, in order to alleviate visual imperfections produced by scaling. The substandard instruction code provided by the Android "Droid Sans Mono" font misplaces features of glyphs containing, as components, "E" and "F", between PPEM sizes of 16 and 24, resulting in noticeable whitespace inconsistencies with other glyphs. Furthermore, the vertical stem in the glyph "T" is positioned too far to the left at PPEM sizes of 12. The remedy for this is to replace the instruction code with automatically generated code from the FreeType project's "ttfautohint" program. First, extract '/system/fonts/DroidSansMono.ttf' from your device: $ adb pull /system/fonts/DroidSansMono.ttf /system/fonts/DroidSansMono.ttf: 1 file pulled, 0 skipped. 23.1 MB/s (90208 bytes in 0.004s) install the "ttfautohint" program: http://freetype.org/ttfautohint/ generate a font file with new hinting instructions: $ ttfautohint DroidSansMono.ttf > DroidSansMono.ttf.rpl and upload them to your device, either back to /system/fonts (which is allowed by free versions of Android, such as Replicant): $ adb root $ adb remount $ adb push DroidSansMono.ttf.rpl /system/fonts/DroidSansMono.ttf or to the user fonts directory described in the "Android Fonts" node of the Emacs manual. You may want to perform this procedure even if you are not experiencing problems with character display, as the automatically generated instructions result in more legible text. ** Glyphs are missing within the "Arial" font or it does not load. Old versions of this font included instruction code that assumed a degree of latitude from the Microsoft font scaler, which grants fonts leave to address nonexistent points without aborting the scaling process, among other invalid TrueType operations. This issue may extend beyond Arial to encompass a larger selection of old fonts designed by Microsoft or Monotype; most of the time, installing newer versions of such fonts will suffice. ** Some TrueType test fonts don't work. It is unlikely that any of these fonts will really prove useful for text editing tasks, since they are designed for the express purpose of testing a TrueType font scaler. The following explanation is present only to satisfy a cat-like curiosity. Most TrueType test fonts "hide" points by moving them to a preposterous location outside the confines of the glyph bounding box. The Microsoft scaler and FreeType promptly disregard such points. Nothing in the TrueType specifications implies that points "hidden" in this fashion should be afforded any special treatment, and thus Emacs eschews doing so. Consequently, black streaks are displayed as Emacs interpolates glyph edges between points within the glyph and points the test font attempts to hide. Since this behavior does not influence the display of real fonts, no action will be taken to address this problem. ** Some other font's instruction code produces undesirable results. Executing instruction code is not a strict requirement for producing correct display results from most current fonts. If a font's instruction code produces results that are merely unpleasing, but not incorrect, then the font was presumably not designed for Emacs's scaler. If its uninstructed glyphs are satisfactory (such as when your screen resolution is high enough to ameliorate scaling artifacts), disable instruction code execution by appending its family name to the variable 'sfnt-uninstructable-font-regexp', then restarting Emacs. ** CJK text does not display in Emacs, but does in other programs. When inserting CJK text into a buffer or visiting a file containing CJK text, Emacs often fails to locate a suitable font. This problem manifests itself as hollow squares with numbers and letters within being displayed in lieu of the text itself. The reason for this is Emacs's absence of support for OpenType fonts utilizing CFF (Compact Font Format) outlines, which the CJK fonts bundled with Android have been distributed as since Android 7.0. The solution is to install a TrueType CJK font to the user fonts directory detailed in the "Android Fonts" node of the Emacs manual. Introducing support for the byzantine CFF font format into the Android port is a large undertaking that we are looking for volunteers to perform. If you are interested in taking responsibility for this task, please contact . ** Emacs can only execute spasmodically in the background. Recent Android releases impose "battery optimization" on programs for which it is not expressly disabled; such optimization inhibits the execution of background services outside brief windows of time distributed at intervals of several dozens of minutes. Such programs as ERC which must send "keep-alive" packets at a rate beyond that at which these windows arrive consequently lose, yielding connection timeouts after Emacs has been in the background long enough that battery optimization enters into effect. This optimization can be disabled through the Settings app: navigate to "Apps & notifications", "Emacs", "Battery", "Battery Optimization", before clicking the drop-down menu labeled "Not Optimized", selecting the option "All Apps", scrolling to "Emacs", clicking on its entry and selecting "Don't Optimize" in the dialog box thus displayed. The organization of the Settings app might disagree with that illustrated above, which if true you should consult the documentation or any search mechanism for it. ** Emacs is not compatible with the "Microsoft SwiftKey" input method. When enabled, windows are repeatedly recentered around earlier buffer positions as they are scrolled. The underlying cause is that Microsoft SwiftKey aggressively forces point towards word boundaries, which motion is sometimes received and duly processed by Emacs after the window in question has already been scrolled past its target position, with the result that the next redisplay recenters the window around this outdated position. There is no solution but installing a more cooperative--and preferably free--input method. ** The default input method performs edits elsewhere than point in large buffers. When first reactivated in a window after having been dismissed, certain heuristics applied by the "Android Keyboard (AOSP)" input method to detect unresponsive text editors, which are ill-adapted to buffers greater than a few thousand characters in length, conclude that Emacs is misbehaving, so that the input method ignores updates to the position of point reported around the time of its activation, and edits suggested by the input method are inserted in a previously reported location that might be wildly removed from the current insertion point. This is a bug in the input method that can be easily reproduced by inserting lengthy documents into any text editor, with no real solution except avoiding edit suggestions from recently-reactivated input methods. ** The F3 key appears to be spontaneously activated. It is possible that this is a product of your inadvertently contacting the back-facing fingerprint sensor, which generates F3 key events on devices manufactured by OnePlus and possibly others. Sadly, to the best of our knowledge such events cannot be distinguished from legitimate keypresses. * Build-time problems ** Configuration *** 'configure' warns "accepted by the compiler, rejected by the preprocessor". This indicates a mismatch between the C compiler and preprocessor that configure is using. For example, on Solaris 10 trying to use CC=/opt/developerstudio12.6/bin/cc (the Oracle Developer Studio compiler) together with CPP=/usr/lib/cpp can result in errors of this form. The solution is to tell configure to use the correct C preprocessor for your C compiler (CPP="/opt/developerstudio12.6/bin/cc -E" in the above example). ** Compilation *** Link-time optimization with clang doesn't work on Fedora 20. As of May 2014, Fedora 20 has broken LLVMgold.so plugin support in clang (tested with clang-3.4-6.fc20) - 'clang --print-file-name=LLVMgold.so' prints 'LLVMgold.so' instead of full path to plugin shared library, and 'clang -flto' is unable to find the plugin with the following error: /bin/ld: error: /usr/bin/../lib/LLVMgold.so: could not load plugin library: /usr/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory The only way to avoid this is to build your own clang from source code repositories, as described at http://clang.llvm.org/get_started.html. *** Building Emacs over NFS fails with "Text file busy". This was reported to happen when building Emacs on a GNU/Linux system (Red Hat Linux 6.2) using a build directory automounted from Solaris (SunOS 5.6) file server, but it might not be limited to that configuration alone. Presumably, the NFS server doesn't commit the files' data to disk quickly enough, and the Emacs executable file is left "busy" for several seconds after Emacs has finished dumping itself. This causes the subsequent commands which invoke the dumped Emacs executable to fail with the above message. In some of these cases, a time skew between the NFS server and the machine where Emacs is built is detected and reported by GNU Make (it says that some of the files have modification time in the future). This might be a symptom of NFS-related problems. If the NFS server runs on Solaris, apply the Solaris patch 105379-05 (Sunos 5.6: /kernel/misc/nfssrv patch). If that doesn't work, or if you have a different version of the OS or the NFS server, you can force the NFS server to use 1KB blocks, which was reported to fix the problem albeit at a price of slowing down file I/O. You can force 1KB blocks by specifying the "-o rsize=1024,wsize=1024" options to the 'mount' command, or by adding ",rsize=1024,wsize=1024" to the mount options in the appropriate system configuration file, such as '/etc/auto.home'. Alternatively, when Make fails due to this problem, you could wait for a few seconds and then invoke Make again. In one particular case, waiting for 10 or more seconds between the two Make invocations seemed to work around the problem. Similar problems can happen if your machine NFS-mounts a directory onto itself. Suppose the Emacs sources live in '/usr/local/src' and you are working on the host called 'marvin'. Then an entry in the '/etc/fstab' file like the following is asking for trouble: marvin:/usr/local/src /usr/local/src ...options.omitted... The solution is to remove this line from '/etc/fstab'. *** Building a 32-bit executable on a 64-bit GNU/Linux architecture. First ensure that the necessary 32-bit system libraries and include files are installed. Then use: env CC="gcc -m32" ./configure --build=i386-linux-gnu --x-libraries=/usr/lib (using the location of the 32-bit X libraries on your system). *** Building on FreeBSD 11 fails at link time due to unresolved symbol The symbol is sendmmsg@FBSD_1.4. This is due to a faulty libgio library on these systems. The solution is to reconfigure Emacs while disabling all the features that require libgio: rsvg, dbus, gconf, and imagemagick. *** Building Emacs 23.3 and later will fail under Cygwin 1.5.19 This is a consequence of a change to src/dired.c on 2010-07-27. The issue is that Cygwin 1.5.19 did not have d_ino in 'struct dirent'. See https://lists.gnu.org/r/emacs-devel/2010-07/msg01266.html *** Building the MS-Windows port with native compilation fails This is known to happen when using MinGW64 GCC 13.1, and seems to affect byte-compilation: the built Emacs crashes while byte-compiling some Lisp files. (This doesn't happen when building a release tarball, because all the Lisp files are already byte-compiled there, but then Emacs could crash later when you use it to byte-compile your or third-party Lisp packages.) The reason seems to be specific to MS-Windows or the MinGW64 port of GCC 13.1, and is somehow related to optimizations in this GCC version. There are several known workarounds: . Use non-default optimization flags. For example, configuring the build like this will avoid the problem: CFLAGS='-O1 -gdwarf-4 -g3' ./configure ... (replace the ellipsis "..." with the rest of 'configure' options and arguments). . Prevent GCC from performing a specific optimization: CFLAGS='-O2 -gdwarf-4 -g3 -fno-optimize-sibling-calls' ./configure ... This is actually a variant of the previous workaround, except that it allows you to have almost the full set of optimizations used by -O2. . Downgrade to GCC 12.x. . Build Emacs without native compilation. *** Building the native MS-Windows port fails due to unresolved externals The linker error messages look like this: oo-spd/i386/ctags.o:ctags.c:(.text+0x156e): undefined reference to `_imp__re_set_syntax' collect2: ld returned 1 exit status This happens because GCC finds an incompatible regex.h header somewhere on the include path, before the version of regex.h supplied with Emacs. One such incompatible version of regex.h is part of the GnuWin32 Regex package. The solution is to remove the incompatible regex.h from the include path, when compiling Emacs. Alternatively, re-run the configure.bat script with the "-isystem C:/GnuWin32/include" switch (adapt for your system's place where you keep the GnuWin32 include files) -- this will cause the compiler to search headers in the directories specified by the Emacs Makefile _before_ it looks in the GnuWin32 include directories. *** Building the native MS-Windows port with Cygwin GCC can fail. Emacs may not build using some Cygwin builds of GCC, such as Cygwin version 1.1.8, using the default configure settings. It appears to be necessary to specify the -mwin32 flag when compiling, and define __MSVCRT__, like so: configure --with-gcc --cflags -mwin32 --cflags -D__MSVCRT__ *** Building the MS-Windows port fails with a CreateProcess failure. Some versions of mingw32 make on some versions of Windows do not seem to detect the shell correctly. Try "make SHELL=cmd.exe", or if that fails, try running make from Cygwin bash instead. *** Building 'ctags' for MS-Windows with the MinGW port of GCC fails. This might happen due to a bug in the MinGW header assert.h, which defines the 'assert' macro with a trailing semi-colon. The following patch to assert.h should solve this: *** include/assert.h.orig Sun Nov 7 02:41:36 1999 --- include/assert.h Mon Jan 29 11:49:10 2001 *************** *** 41,47 **** /* * If not debugging, assert does nothing. */ ! #define assert(x) ((void)0); #else /* debugging enabled */ --- 41,47 ---- /* * If not debugging, assert does nothing. */ ! #define assert(x) ((void)0) #else /* debugging enabled */ *** Building the MS-Windows port with Visual Studio 2005 fails. Microsoft no longer ships the single threaded version of the C library with their compiler, and the multithreaded static library is missing some functions that Microsoft have deemed non-threadsafe. The dynamically linked C library has all the functions, but there is a conflict between the versions of malloc in the DLL and in Emacs, which is not resolvable due to the way Windows does dynamic linking. We recommend the use of the MinGW port of GCC for compiling Emacs, as not only does it not suffer these problems, but it is also Free software like Emacs. *** Building the MS-Windows port with Visual Studio fails compiling emacs.rc If the build fails with the following message then the problem described here most likely applies: ../nt/emacs.rc(1) : error RC2176 : old DIB in icons\emacs.ico; pass it through SDKPAINT The Emacs icon contains a high resolution PNG icon for Vista, which is not recognized by older versions of the resource compiler. There are several workarounds for this problem: 1. Use Free MinGW tools to compile, which do not have this problem. 2. Install the latest Windows SDK. 3. Replace emacs.ico with an older or edited icon. *** Building the MS-Windows port complains about unknown escape sequences. Errors and warnings can look like this: w32.c:1959:27: error: \x used with no following hex digits w32.c:1959:27: warning: unknown escape sequence '\i' This happens when paths using backslashes are passed to the compiler or linker (via -I and possibly other compiler flags); when these paths are included in source code, the backslashes are interpreted as escape sequences. See https://lists.gnu.org/r/emacs-devel/2010-07/msg00995.html The fix is to use forward slashes in all paths passed to the compiler. ** Linking *** Building Emacs with a system compiler fails to link because of an undefined symbol such as __eprintf which does not appear in Emacs. This can happen if some of the libraries linked into Emacs were built with GCC, but Emacs itself is being linked with a compiler other than GCC. Object files compiled with GCC might need some helper functions from libgcc.a, the library which comes with GCC, but the system compiler does not instruct the linker to search libgcc.a during the link stage. A solution is to link with GCC, like this: make CC=gcc Since the .o object files already exist, this will not recompile Emacs with GCC, but just restart by trying again to link temacs. *** Sun with acc: Link failure when using acc on a Sun. To use acc, you need additional options just before the libraries, such as /usr/lang/SC2.0.1/values-Xt.o -L/usr/lang/SC2.0.1/cg87 -L/usr/lang/SC2.0.1 and you need to add -lansi just before -lc. The precise file names depend on the compiler version, so we cannot easily arrange to supply them. *** 'tparam' reported as a multiply-defined symbol when linking with ncurses. This problem results from an incompatible change in ncurses, in version 1.9.9e approximately. This version is unable to provide a definition of tparm without also defining tparam. This is also incompatible with Terminfo; as a result, the Emacs Terminfo support does not work with this version of ncurses. The fix is to install a newer version of ncurses, such as version 4.2. ** Bootstrapping Bootstrapping (compiling the .el files) is normally only necessary with development builds, since the .elc files are pre-compiled in releases. ** Dumping *** temacs.exe fails to run when invoked by the build for dumping The error message might be something like make[2]: *** [Makefile:915: bootstrap-emacs.pdmp] Error 127 This happens if you try to build Emacs on versions of MS-Windows older than the minimum version supported by MinGW-w64. As of Dec 2022, the minimum supported Windows version is 8.1, and the computer hardware (CPU, memory, disk) should also match the minimum Windows 8.1 requirements. *** Segfault during 'make' If Emacs segfaults when 'make' executes one of these commands: LC_ALL=C ./temacs -batch -l loadup bootstrap LC_ALL=C ./temacs -batch -l loadup dump the problem may be due to inadequate workarounds for address space layout randomization (ASLR), an operating system feature that randomizes the virtual address space of a process. ASLR is commonly enabled in Linux and NetBSD kernels, and is intended to deter exploits of pointer-related bugs in applications. If ASLR is enabled, the command: cat /proc/sys/kernel/randomize_va_space # GNU/Linux sysctl security.pax.aslr.global # NetBSD outputs a nonzero value. These segfaults should not occur on most modern systems, because the Emacs build procedure uses the command 'setfattr' or 'paxctl' to mark the Emacs executable as requiring non-randomized address space, and Emacs uses the 'personality' system call to disable address space randomization when dumping. However, older kernels may not support 'setfattr', 'paxctl', or 'personality', and newer Linux kernels have a secure computing mode (seccomp) that can be configured to disable the 'personality' call. It may be possible to work around the 'personality' problem in a newer Linux kernel by configuring seccomp to allow the 'personality' call. For example, if you are building Emacs under Docker, you can run the Docker container with a security profile that allows 'personality' by using Docker's --security-opt option with an appropriate profile; see . To work around the ASLR problem in either an older or a newer kernel, you can temporarily disable the feature while building Emacs. On GNU/Linux you can do so using the following command (as root). echo 0 > /proc/sys/kernel/randomize_va_space You can re-enable the feature when you are done, by echoing the original value back to the file. NetBSD uses a different command, e.g., 'sysctl -w security.pax.aslr.global=0'. Alternatively, you can try using the 'setarch' command when building temacs like this, where -R disables address space randomization: setarch $(uname -m) -R make ASLR is not the only problem that can break Emacs dumping. Another issue is that in Red Hat Linux kernels, Exec-shield is enabled by default, and this creates a different memory layout. Emacs should handle this at build time, but if this fails the following instructions may be useful. Exec-shield is enabled on your system if cat /proc/sys/kernel/exec-shield prints a nonzero value. You can temporarily disable it as follows: echo 0 > /proc/sys/kernel/exec-shield As with randomize_va_space, you can re-enable Exec-shield when you are done, by echoing the original value back to the file. *** temacs prints "Pure Lisp storage exhausted". This means that the Lisp code loaded from the .elc and .el files during 'temacs --batch --load loadup dump' took up more space than was allocated. This could be caused by 1) adding code to the preloaded Lisp files 2) adding more preloaded files in loadup.el 3) having a site-init.el or site-load.el which loads files. Note that ANY site-init.el or site-load.el is nonstandard; if you have received Emacs from some other site and it contains a site-init.el or site-load.el file, consider deleting that file. 4) getting the wrong .el or .elc files (not from the directory you expected). 5) deleting some .elc files that are supposed to exist. This would cause the source files (.el files) to be loaded instead. They take up more room, so you lose. 6) a bug in the Emacs distribution which underestimates the space required. If the need for more space is legitimate, change the definition of PURESIZE in puresize.h. But in some of the cases listed above, this problem is a consequence of something else that is wrong. Be sure to check and fix the real problem. *** openSUSE 10.3: Segfault in bcopy during dumping. This is due to a bug in the bcopy implementation in openSUSE 10.3. It is/will be fixed in an openSUSE update. ** First execution *** Emacs binary is not in executable format, and cannot be run. This was reported to happen when Emacs is built in a directory mounted via NFS, for some combinations of NFS client and NFS server. Usually, the file 'emacs' produced in these cases is full of binary null characters, and the 'file' utility says: emacs: ASCII text, with no line terminators We don't know what exactly causes this failure. A work-around is to build Emacs in a directory on a local disk. *** The dumped Emacs crashes when run, trying to write pure data. On a system where getpagesize is not a system call, it is defined as a macro. If the definition (in both unex*.c and malloc.c) is wrong, it can cause problems like this. You might be able to find the correct value in the man page for a.out(5). * Problems on legacy systems This section covers bugs reported on very old hardware or software. If you are using hardware and an operating system shipped after 2000, it is unlikely you will see any of these. ** GNU/Linux *** Ubuntu 8.04 make 3.81-3build1: "No rule to make target" Compiling the lisp files fails at random places, complaining: "No rule to make target '/path/to/some/lisp.elc'". The causes of this problem are not understood. Using GNU make 3.81 compiled from source, rather than the Ubuntu version, worked. See , . ** Solaris *** Problem with remote X server on Suns. On a Sun, running Emacs on one machine with the X server on another may not work if you have used the unshared system libraries. This is because the unshared libraries fail to use YP for host name lookup. As a result, the host name you specify may not be recognized. *** Solaris 2.6: Emacs crashes with SIGBUS or SIGSEGV on Solaris after you delete a frame. We suspect that this is a bug in the X libraries provided by Sun. There is a report that one of these patches fixes the bug and makes the problem stop: 105216-01 105393-01 105518-01 105621-01 105665-01 105615-02 105216-02 105667-01 105401-08 105615-03 105621-02 105686-02 105736-01 105755-03 106033-01 105379-01 105786-01 105181-04 105379-03 105786-04 105845-01 105284-05 105669-02 105837-01 105837-02 105558-01 106125-02 105407-01 Another person using a newer system (kernel patch level Generic_105181-06) suspects that the bug was fixed by one of these more recent patches: 106040-07 SunOS 5.6: X Input & Output Method patch 106222-01 OpenWindows 3.6: filemgr (ff.core) fixes 105284-12 Motif 1.2.7: sparc Runtime library patch *** Solaris 7 or 8: Emacs reports a BadAtom error (from X) This happens when Emacs was built on some other version of Solaris. Rebuild it on Solaris 8. *** When using M-x dbx with the SparcWorks debugger, the 'up' and 'down' commands do not move the arrow in Emacs. You can fix this by adding the following line to '~/.dbxinit': dbxenv output_short_file_name off *** On Solaris, CTRL-t is ignored by Emacs when you use the fr.ISO-8859-15 locale (and maybe other related locales). You can fix this by editing the file: /usr/openwin/lib/locale/iso8859-15/Compose Near the bottom there is a line that reads: Ctrl : "\276" threequarters while it should read: Ctrl : "\276" threequarters Note the lower case . Changing this line should make C-t work. *** On Solaris, Emacs fails to set menu-bar-update-hook on startup, with error "Error in menu-bar-update-hook: (error Point before start of properties)". This seems to be a GCC optimization bug that occurs for GCC 4.1.2 (-g and -g -O2) and GCC 4.2.3 (-g -O and -g -O2). You can fix this by compiling with GCC 4.2.3 or CC 5.7, with no optimizations. *** Other legacy Solaris problems **** Strange results from format %d in a few cases, on a Sun. Sun compiler version SC3.0 has been found to miscompile part of editfns.c. The workaround is to compile with some other compiler such as GCC. **** On Solaris, Emacs dumps core if lisp-complete-symbol is called. If you compile Emacs with the -fast or -xO4 option with version 3.0.2 of the Sun C compiler, Emacs dumps core when lisp-complete-symbol is called. The problem does not happen if you compile with GCC. **** On Solaris, Emacs crashes if you use (display-time). This can happen if you configure Emacs without specifying the precise version of Solaris that you are using. **** Solaris 2.x: GCC complains "64 bit integer types not supported". This suggests that GCC is not installed correctly. Most likely you are using GCC 2.7.2.3 (or earlier) on Solaris 2.6 (or later); this does not work without patching. To run GCC 2.7.2.3 on Solaris 2.6 or later, you must patch fixinc.svr4 and reinstall GCC from scratch as described in the Solaris FAQ . A better fix is to upgrade to GCC 2.8.1 or later. **** Solaris 2.7: Building Emacs with WorkShop Compilers 5.0 98/12/15 C 5.0 failed, apparently with non-default CFLAGS, most probably due to compiler bugs. Using Sun Solaris 2.7 Sun WorkShop 6 update 1 C release was reported to work without problems. It worked OK on another system with Solaris 8 using apparently the same 5.0 compiler and the default CFLAGS. **** Solaris 2.6 and 7: the Compose key does not work. This is a bug in Motif in Solaris. Supposedly it has been fixed for the next major release of Solaris. However, if someone with Sun support complains to Sun about the bug, they may release a patch. If you do this, mention Sun bug #4188711. One workaround is to use a locale that allows non-ASCII characters. For example, before invoking emacs, set the LC_ALL environment variable to "en_US" (American English). The directory /usr/lib/locale lists the supported locales; any locale other than "C" or "POSIX" should do. pen@lysator.liu.se says (Feb 1998) that the Compose key does work if you link with the MIT X11 libraries instead of the Solaris X11 libraries. ** OpenBSD *** OpenBSD 4.0 macppc: Segfault during dumping. The build aborts with signal 11 when the command './temacs --batch --load loadup bootstrap' tries to load files.el. A workaround seems to be to reduce the level of compiler optimization used during the build (from -O2 to -O1). It is possible this is an OpenBSD GCC problem specific to the macppc architecture, possibly only occurring with older versions of GCC (e.g. 3.3.5). ** AIX *** AIX 4.3.x or 4.4: Compiling fails. This could happen if you use /bin/c89 as your compiler, instead of the default 'cc'. /bin/c89 treats certain warnings, such as benign redefinitions of macros, as errors, and fails the build. A solution is to use the default compiler 'cc'. *** AIX 4: Some programs fail when run in a Shell buffer with an error message like No terminfo entry for "unknown". On AIX, many terminal type definitions are not installed by default. 'unknown' is one of them. Install the "Special Generic Terminal Definitions" to make them defined. ** MS-Windows 95, 98, ME, and NT *** MS-Windows 95: Networking. To support server sockets, Emacs loads ws2_32.dll. If this file is missing, all Emacs networking features are disabled. Old versions of Windows 95 may not have the required DLL. To use Emacs's networking features on Windows 95, you must install the "Windows Socket 2" update available from MicroSoft's support Web. *** MS-Windows NT4: addpm fails to run, complaining about Shell32.dll This is likely to happen because Shell32.dll shipped with NT4 lacks the updates required by Emacs. Installing Internet Explorer 4 solves the problem. Note that it is NOT enough to install IE6, because doing so will not install the Shell32.dll update. *** MS-Windows NT/95: Problems running Perl under Emacs 'perl -de 0' just hangs when executed in an Emacs subshell. The fault lies with Perl (indirectly with Windows NT/95). The problem is that the Perl debugger explicitly opens a connection to "CON", which is the DOS/NT equivalent of "/dev/tty", for interacting with the user. On Unix, this is okay, because Emacs (or the shell?) creates a pseudo-tty so that /dev/tty is really the pipe Emacs is using to communicate with the subprocess. On NT, this fails because CON always refers to the handle for the relevant console (approximately equivalent to a tty), and cannot be redirected to refer to the pipe Emacs assigned to the subprocess as stdin. A workaround is to modify perldb.pl to use STDIN/STDOUT instead of CON. For Perl 4: *** PERL/LIB/PERLDB.PL.orig Wed May 26 08:24:18 1993 --- PERL/LIB/PERLDB.PL Mon Jul 01 15:28:16 1996 *************** *** 68,74 **** $rcfile=".perldb"; } else { ! $console = "con"; $rcfile="perldb.ini"; } --- 68,74 ---- $rcfile=".perldb"; } else { ! $console = ""; $rcfile="perldb.ini"; } For Perl 5: *** perl/5.001/lib/perl5db.pl.orig Sun Jun 04 21:13:40 1995 --- perl/5.001/lib/perl5db.pl Mon Jul 01 17:00:08 1996 *************** *** 22,28 **** $rcfile=".perldb"; } elsif (-e "con") { ! $console = "con"; $rcfile="perldb.ini"; } else { --- 22,28 ---- $rcfile=".perldb"; } elsif (-e "con") { ! $console = ""; $rcfile="perldb.ini"; } else { *** MS-Windows NT/95: Help text in tooltips does not work Windows 95 and Windows NT up to version 4.0 do not support help text for menus. Help text is only available in later versions of Windows. *** MS-Windows 95: Alt-f6 does not get through to Emacs. This character seems to be trapped by the kernel in Windows 95. You can enter M-f6 by typing ESC f6. *** MS-Windows 98/ME: subprocesses do not terminate properly. This is a limitation of the Operating System, and can cause problems when shutting down Windows. Ensure that all subprocesses are exited cleanly before exiting Emacs. For more details, see the Emacs on MS Windows FAQ (info manual "efaq-w32"). *** MS-Windows 98/ME: crashes when Emacs invokes non-existent programs. When a program you are trying to run is not found on the PATH, Windows might respond by crashing or locking up your system. In particular, this has been reported when trying to compile a Java program in JDEE when javac.exe is installed, but not on the system PATH. ** MS-DOS *** When compiling with DJGPP on MS-Windows NT or later, "config msdos" fails. If the error message is "VDM has been already loaded", this is because Windows has a program called 'redir.exe' that is incompatible with a program by the same name supplied with DJGPP, which is used by config.bat. To resolve this, move the DJGPP's 'bin' subdirectory to the front of your PATH environment variable. *** When Emacs compiled with DJGPP runs on Windows 2000 and later, it cannot find your HOME directory. This was reported to happen when you click on "Save for future sessions" button in a Customize buffer. You might see an error message like this one: basic-save-buffer-2: c:/FOO/BAR/~dosuser/: no such directory (The telltale sign is the "~USER" part at the end of the directory Emacs complains about, where USER is your username or the literal string "dosuser", which is the default username set up by the DJGPP startup file DJGPP.ENV.) This happens when the functions 'user-login-name' and 'user-real-login-name' return different strings for your username as Emacs sees it. To correct this, make sure both USER and USERNAME environment variables are set to the same value. Windows 2000 and later sets USERNAME, so if you want to keep that, make sure USER is set to the same value. If you don't want to set USER globally, you can do it in the [emacs] section of your DJGPP.ENV file. *** When Emacs compiled with DJGPP runs on Vista, it runs out of memory. If Emacs running on Vista displays "!MEM FULL!" in the mode line, you are hitting the memory allocation bugs in the Vista DPMI server. See msdos/INSTALL for how to work around these bugs (search for "Vista"). *** When compiling with DJGPP on MS-Windows 95, Make fails for some targets like make-docfile. This can happen if long file name support (the setting of environment variable LFN) when Emacs distribution was unpacked and during compilation are not the same. See msdos/INSTALL for the explanation of how to avoid this problem. *** Emacs compiled with DJGPP complains at startup: "Wrong type of argument: internal-facep, msdos-menu-active-face" This can happen if you define an environment variable 'TERM'. Emacs on MSDOS uses an internal terminal emulator which is disabled if the value of 'TERM' is anything but the string "internal". Emacs then works as if its terminal were a dumb glass teletype that doesn't support faces. To work around this, arrange for 'TERM' to be undefined when Emacs runs. The best way to do that is to add an [emacs] section to the DJGPP.ENV file which defines an empty value for 'TERM'; this way, only Emacs gets the empty value, while the rest of your system works as before. *** MS-DOS: Emacs crashes at startup. Some users report that Emacs 19.29 requires dpmi memory management, and crashes on startup if the system does not have it. We don't know why this happens--perhaps these machines don't have enough real memory, or perhaps something is wrong in Emacs or the compiler. However, arranging to use dpmi support is a workaround. You can find out if you have a dpmi host by running go32 without arguments; it will tell you if it uses dpmi memory. For more information about dpmi memory, consult the djgpp FAQ. (djgpp is the GNU C compiler as packaged for MSDOS.) Compiling Emacs under MSDOS is extremely sensitive for proper memory configuration. If you experience problems during compilation, consider removing some or all memory resident programs (notably disk caches) and make sure that your memory managers are properly configured. See the djgpp faq for configuration hints. *** Emacs compiled with DJGPP for MS-DOS/MS-Windows cannot access files in the directory with the special name 'dev' under the root of any drive, e.g. 'c:/dev'. This is an unfortunate side-effect of the support for Unix-style device names such as /dev/null in the DJGPP runtime library. A work-around is to rename the problem directory to another name. *** MS-DOS: Emacs compiled for MSDOS cannot find some Lisp files, or other run-time support files, when long filename support is enabled. Usually, this problem will manifest itself when Emacs exits immediately after flashing the startup screen, because it cannot find the Lisp files it needs to load at startup. Redirect Emacs stdout and stderr to a file to see the error message printed by Emacs. Another manifestation of this problem is that Emacs is unable to load the support for editing program sources in languages such as C and Lisp. This can happen if the Emacs distribution was unzipped without LFN support, thus causing long filenames to be truncated to the first 6 characters and a numeric tail that Windows 95 normally attaches to it. You should unzip the files again with a utility that supports long filenames (such as djtar from DJGPP or InfoZip's UnZip program compiled with DJGPP v2). The file msdos/INSTALL explains this issue in more detail. Another possible reason for such failures is that Emacs compiled for MSDOS is used on Windows NT, where long file names are not supported by this version of Emacs, but the distribution was unpacked by an unzip program that preserved the long file names instead of truncating them to DOS 8+3 limits. To be useful on NT, the MSDOS port of Emacs must be unzipped by a DOS utility, so that long file names are properly truncated. ** Apple Macintosh operating systems *** OS X 10.9 and earlier: symlinks autocomplete as directories Autocompleting the name of a symbolic link incorrectly appends "/". Building and running Emacs on OS X 10.10 (or later) fixes the problem. Older operating systems are no longer supported by Apple. https://bugs.gnu.org/31305 ** Archaic window managers and toolkits *** Open Look: Under Open Look, the Emacs window disappears when you type M-q. Some versions of the Open Look window manager interpret M-q as a quit command for whatever window you are typing at. If you want to use Emacs with that window manager, you should try to configure the window manager to use some other command. You can disable the shortcut keys entirely by adding this line to ~/.OWdefaults: OpenWindows.WindowMenuAccelerators: False *** twm: A position you specified in .Xdefaults is ignored, using twm. twm normally ignores "program-specified" positions. You can tell it to obey them with this command in your '.twmrc' file: UsePPosition "on" #allow clients to request a position ** Bugs related to old DEC hardware *** The Compose key on a DEC keyboard does not work as Meta key. This shell command should fix it: xmodmap -e 'keycode 0xb1 = Meta_L' *** Keyboard input gets confused after a beep when using a DECserver as a concentrator. This problem seems to be a matter of configuring the DECserver to use 7 bit characters rather than 8 bit characters. This file is part of GNU Emacs. GNU Emacs is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. GNU Emacs is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Emacs. If not, see . Local variables: mode: outline paragraph-separate: "[ ]*$" end: