1 This is ../info/lispref.info, produced by makeinfo version 4.0 from
4 INFO-DIR-SECTION XEmacs Editor
6 * Lispref: (lispref). XEmacs Lisp Reference Manual.
11 GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU
12 Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid
13 Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994
14 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995
15 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp
16 Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp
17 Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp
18 Reference Manual (for 19.15 and 20.1, 20.2, 20.3) v3.2, April, May,
19 November 1997 XEmacs Lisp Reference Manual (for 21.0) v3.3, April 1998
21 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software
22 Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc.
23 Copyright (C) 1995, 1996 Ben Wing.
25 Permission is granted to make and distribute verbatim copies of this
26 manual provided the copyright notice and this permission notice are
27 preserved on all copies.
29 Permission is granted to copy and distribute modified versions of
30 this manual under the conditions for verbatim copying, provided that the
31 entire resulting derived work is distributed under the terms of a
32 permission notice identical to this one.
34 Permission is granted to copy and distribute translations of this
35 manual into another language, under the above conditions for modified
36 versions, except that this permission notice may be stated in a
37 translation approved by the Foundation.
39 Permission is granted to copy and distribute modified versions of
40 this manual under the conditions for verbatim copying, provided also
41 that the section entitled "GNU General Public License" is included
42 exactly as in the original, and provided that the entire resulting
43 derived work is distributed under the terms of a permission notice
44 identical to this one.
46 Permission is granted to copy and distribute translations of this
47 manual into another language, under the above conditions for modified
48 versions, except that the section entitled "GNU General Public License"
49 may be included in a translation approved by the Free Software
50 Foundation instead of in the original English.
53 File: lispref.info, Node: Style Tips, Next: Compilation Tips, Up: Tips
55 Writing Clean Lisp Programs
56 ===========================
58 Here are some tips for avoiding common errors in writing Lisp code
59 intended for widespread use:
61 * Since all global variables share the same name space, and all
62 functions share another name space, you should choose a short word
63 to distinguish your program from other Lisp programs. Then take
64 care to begin the names of all global variables, constants, and
65 functions with the chosen prefix. This helps avoid name conflicts.
67 This recommendation applies even to names for traditional Lisp
68 primitives that are not primitives in XEmacs Lisp--even to `cadr'.
69 Believe it or not, there is more than one plausible way to define
70 `cadr'. Play it safe; append your name prefix to produce a name
71 like `foo-cadr' or `mylib-cadr' instead.
73 If you write a function that you think ought to be added to Emacs
74 under a certain name, such as `twiddle-files', don't call it by
75 that name in your program. Call it `mylib-twiddle-files' in your
76 program, and send mail to `bug-gnu-emacs@prep.ai.mit.edu'
77 suggesting we add it to Emacs. If and when we do, we can change
78 the name easily enough.
80 If one prefix is insufficient, your package may use two or three
81 alternative common prefixes, so long as they make sense.
83 Separate the prefix from the rest of the symbol name with a hyphen,
84 `-'. This will be consistent with XEmacs itself and with most
87 * It is often useful to put a call to `provide' in each separate
88 library program, at least if there is more than one entry point to
91 * If a file requires certain other library programs to be loaded
92 beforehand, then the comments at the beginning of the file should
93 say so. Also, use `require' to make sure they are loaded.
95 * If one file FOO uses a macro defined in another file BAR, FOO
96 should contain this expression before the first use of the macro:
98 (eval-when-compile (require 'BAR))
100 (And BAR should contain `(provide 'BAR)', to make the `require'
101 work.) This will cause BAR to be loaded when you byte-compile
102 FOO. Otherwise, you risk compiling FOO without the necessary
103 macro loaded, and that would produce compiled code that won't work
104 right. *Note Compiling Macros::.
106 Using `eval-when-compile' avoids loading BAR when the compiled
107 version of FOO is _used_.
109 * If you define a major mode, make sure to run a hook variable using
110 `run-hooks', just as the existing major modes do. *Note Hooks::.
112 * If the purpose of a function is to tell you whether a certain
113 condition is true or false, give the function a name that ends in
114 `p'. If the name is one word, add just `p'; if the name is
115 multiple words, add `-p'. Examples are `framep' and
118 * If a user option variable records a true-or-false condition, give
119 it a name that ends in `-flag'.
121 * Please do not define `C-c LETTER' as a key in your major modes.
122 These sequences are reserved for users; they are the *only*
123 sequences reserved for users, so we cannot do without them.
125 Instead, define sequences consisting of `C-c' followed by a
126 non-letter. These sequences are reserved for major modes.
128 Changing all the major modes in Emacs 18 so they would follow this
129 convention was a lot of work. Abandoning this convention would
130 make that work go to waste, and inconvenience users.
132 * Sequences consisting of `C-c' followed by `{', `}', `<', `>', `:'
133 or `;' are also reserved for major modes.
135 * Sequences consisting of `C-c' followed by any other punctuation
136 character are allocated for minor modes. Using them in a major
137 mode is not absolutely prohibited, but if you do that, the major
138 mode binding may be shadowed from time to time by minor modes.
140 * You should not bind `C-h' following any prefix character (including
141 `C-c'). If you don't bind `C-h', it is automatically available as
142 a help character for listing the subcommands of the prefix
145 * You should not bind a key sequence ending in <ESC> except following
146 another <ESC>. (That is, it is ok to bind a sequence ending in
149 The reason for this rule is that a non-prefix binding for <ESC> in
150 any context prevents recognition of escape sequences as function
151 keys in that context.
153 * Applications should not bind mouse events based on button 1 with
154 the shift key held down. These events include `S-mouse-1',
155 `M-S-mouse-1', `C-S-mouse-1', and so on. They are reserved for
158 * Modes should redefine `mouse-2' as a command to follow some sort of
159 reference in the text of a buffer, if users usually would not want
160 to alter the text in that buffer by hand. Modes such as Dired,
161 Info, Compilation, and Occur redefine it in this way.
163 * When a package provides a modification of ordinary Emacs behavior,
164 it is good to include a command to enable and disable the feature,
165 Provide a command named `WHATEVER-mode' which turns the feature on
166 or off, and make it autoload (*note Autoload::). Design the
167 package so that simply loading it has no visible effect--that
168 should not enable the feature. Users will request the feature by
169 invoking the command.
171 * It is a bad idea to define aliases for the Emacs primitives. Use
172 the standard names instead.
174 * Redefining an Emacs primitive is an even worse idea. It may do
175 the right thing for a particular program, but there is no telling
176 what other programs might break as a result.
178 * If a file does replace any of the functions or library programs of
179 standard XEmacs, prominent comments at the beginning of the file
180 should say which functions are replaced, and how the behavior of
181 the replacements differs from that of the originals.
183 * Please keep the names of your XEmacs Lisp source files to 13
184 characters or less. This way, if the files are compiled, the
185 compiled files' names will be 14 characters or less, which is
186 short enough to fit on all kinds of Unix systems.
188 * Don't use `next-line' or `previous-line' in programs; nearly
189 always, `forward-line' is more convenient as well as more
190 predictable and robust. *Note Text Lines::.
192 * Don't call functions that set the mark, unless setting the mark is
193 one of the intended features of your program. The mark is a
194 user-level feature, so it is incorrect to change the mark except
195 to supply a value for the user's benefit. *Note The Mark::.
197 In particular, don't use these functions:
199 * `beginning-of-buffer', `end-of-buffer'
201 * `replace-string', `replace-regexp'
203 If you just want to move point, or replace a certain string,
204 without any of the other features intended for interactive users,
205 you can replace these functions with one or two lines of simple
208 * Use lists rather than vectors, except when there is a particular
209 reason to use a vector. Lisp has more facilities for manipulating
210 lists than for vectors, and working with lists is usually more
213 Vectors are advantageous for tables that are substantial in size
214 and are accessed in random order (not searched front to back),
215 provided there is no need to insert or delete elements (only lists
218 * The recommended way to print a message in the echo area is with
219 the `message' function, not `princ'. *Note The Echo Area::.
221 * When you encounter an error condition, call the function `error'
222 (or `signal'). The function `error' does not return. *Note
225 Do not use `message', `throw', `sleep-for', or `beep' to report
228 * An error message should start with a capital letter but should not
231 * Try to avoid using recursive edits. Instead, do what the Rmail `e'
232 command does: use a new local keymap that contains one command
233 defined to switch back to the old local keymap. Or do what the
234 `edit-options' command does: switch to another buffer and let the
235 user switch back at will. *Note Recursive Editing::.
237 * In some other systems there is a convention of choosing variable
238 names that begin and end with `*'. We don't use that convention
239 in Emacs Lisp, so please don't use it in your programs. (Emacs
240 uses such names only for program-generated buffers.) The users
241 will find Emacs more coherent if all libraries use the same
244 * Indent each function with `C-M-q' (`indent-sexp') using the
245 default indentation parameters.
247 * Don't make a habit of putting close-parentheses on lines by
248 themselves; Lisp programmers find this disconcerting. Once in a
249 while, when there is a sequence of many consecutive
250 close-parentheses, it may make sense to split them in one or two
253 * Please put a copyright notice on the file if you give copies to
254 anyone. Use the same lines that appear at the top of the Lisp
255 files in XEmacs itself. If you have not signed papers to assign
256 the copyright to the Foundation, then place your name in the
257 copyright notice in place of the Foundation's name.
260 File: lispref.info, Node: Compilation Tips, Next: Documentation Tips, Prev: Style Tips, Up: Tips
262 Tips for Making Compiled Code Fast
263 ==================================
265 Here are ways of improving the execution speed of byte-compiled Lisp
268 * Use the `profile' library to profile your program. See the file
269 `profile.el' for instructions.
271 * Use iteration rather than recursion whenever possible. Function
272 calls are slow in XEmacs Lisp even when a compiled function is
273 calling another compiled function.
275 * Using the primitive list-searching functions `memq', `member',
276 `assq', or `assoc' is even faster than explicit iteration. It may
277 be worth rearranging a data structure so that one of these
278 primitive search functions can be used.
280 * Certain built-in functions are handled specially in byte-compiled
281 code, avoiding the need for an ordinary function call. It is a
282 good idea to use these functions rather than alternatives. To see
283 whether a function is handled specially by the compiler, examine
284 its `byte-compile' property. If the property is non-`nil', then
285 the function is handled specially.
287 For example, the following input will show you that `aref' is
288 compiled specially (*note Array Functions::) while `elt' is not
289 (*note Sequence Functions::):
291 (get 'aref 'byte-compile)
292 => byte-compile-two-args
294 (get 'elt 'byte-compile)
297 * If calling a small function accounts for a substantial part of
298 your program's running time, make the function inline. This
299 eliminates the function call overhead. Since making a function
300 inline reduces the flexibility of changing the program, don't do
301 it unless it gives a noticeable speedup in something slow enough
302 that users care about the speed. *Note Inline Functions::.
305 File: lispref.info, Node: Documentation Tips, Next: Comment Tips, Prev: Compilation Tips, Up: Tips
307 Tips for Documentation Strings
308 ==============================
310 Here are some tips for the writing of documentation strings.
312 * Every command, function, or variable intended for users to know
313 about should have a documentation string.
315 * An internal variable or subroutine of a Lisp program might as well
316 have a documentation string. In earlier Emacs versions, you could
317 save space by using a comment instead of a documentation string,
318 but that is no longer the case.
320 * The first line of the documentation string should consist of one
321 or two complete sentences that stand on their own as a summary.
322 `M-x apropos' displays just the first line, and if it doesn't
323 stand on its own, the result looks bad. In particular, start the
324 first line with a capital letter and end with a period.
326 The documentation string can have additional lines that expand on
327 the details of how to use the function or variable. The
328 additional lines should be made up of complete sentences also, but
329 they may be filled if that looks good.
331 * For consistency, phrase the verb in the first sentence of a
332 documentation string as an infinitive with "to" omitted. For
333 instance, use "Return the cons of A and B." in preference to
334 "Returns the cons of A and B." Usually it looks good to do
335 likewise for the rest of the first paragraph. Subsequent
336 paragraphs usually look better if they have proper subjects.
338 * Write documentation strings in the active voice, not the passive,
339 and in the present tense, not the future. For instance, use
340 "Return a list containing A and B." instead of "A list containing
341 A and B will be returned."
343 * Avoid using the word "cause" (or its equivalents) unnecessarily.
344 Instead of, "Cause Emacs to display text in boldface," write just
345 "Display text in boldface."
347 * Do not start or end a documentation string with whitespace.
349 * Format the documentation string so that it fits in an Emacs window
350 on an 80-column screen. It is a good idea for most lines to be no
351 wider than 60 characters. The first line can be wider if
352 necessary to fit the information that ought to be there.
354 However, rather than simply filling the entire documentation
355 string, you can make it much more readable by choosing line breaks
356 with care. Use blank lines between topics if the documentation
359 * *Do not* indent subsequent lines of a documentation string so that
360 the text is lined up in the source code with the text of the first
361 line. This looks nice in the source code, but looks bizarre when
362 users view the documentation. Remember that the indentation
363 before the starting double-quote is not part of the string!
365 * A variable's documentation string should start with `*' if the
366 variable is one that users would often want to set interactively.
367 If the value is a long list, or a function, or if the variable
368 would be set only in init files, then don't start the
369 documentation string with `*'. *Note Defining Variables::.
371 * The documentation string for a variable that is a yes-or-no flag
372 should start with words such as "Non-nil means...", to make it
373 clear that all non-`nil' values are equivalent and indicate
374 explicitly what `nil' and non-`nil' mean.
376 * When a function's documentation string mentions the value of an
377 argument of the function, use the argument name in capital letters
378 as if it were a name for that value. Thus, the documentation
379 string of the function `/' refers to its second argument as
380 `DIVISOR', because the actual argument name is `divisor'.
382 Also use all caps for meta-syntactic variables, such as when you
383 show the decomposition of a list or vector into subunits, some of
386 * When a documentation string refers to a Lisp symbol, write it as it
387 would be printed (which usually means in lower case), with
388 single-quotes around it. For example: `lambda'. There are two
389 exceptions: write t and nil without single-quotes. (In this
390 manual, we normally do use single-quotes for those symbols.)
392 * Don't write key sequences directly in documentation strings.
393 Instead, use the `\\[...]' construct to stand for them. For
394 example, instead of writing `C-f', write `\\[forward-char]'. When
395 Emacs displays the documentation string, it substitutes whatever
396 key is currently bound to `forward-char'. (This is normally `C-f',
397 but it may be some other character if the user has moved key
398 bindings.) *Note Keys in Documentation::.
400 * In documentation strings for a major mode, you will want to refer
401 to the key bindings of that mode's local map, rather than global
402 ones. Therefore, use the construct `\\<...>' once in the
403 documentation string to specify which key map to use. Do this
404 before the first use of `\\[...]'. The text inside the `\\<...>'
405 should be the name of the variable containing the local keymap for
408 It is not practical to use `\\[...]' very many times, because
409 display of the documentation string will become slow. So use this
410 to describe the most important commands in your major mode, and
411 then use `\\{...}' to display the rest of the mode's keymap.
414 File: lispref.info, Node: Comment Tips, Next: Library Headers, Prev: Documentation Tips, Up: Tips
416 Tips on Writing Comments
417 ========================
419 We recommend these conventions for where to put comments and how to
423 Comments that start with a single semicolon, `;', should all be
424 aligned to the same column on the right of the source code. Such
425 comments usually explain how the code on the same line does its
426 job. In Lisp mode and related modes, the `M-;'
427 (`indent-for-comment') command automatically inserts such a `;' in
428 the right place, or aligns such a comment if it is already present.
430 This and following examples are taken from the Emacs sources.
432 (setq base-version-list ; there was a base
433 (assoc (substring fn 0 start-vn) ; version to which
434 file-version-assoc-list)) ; this looks like
438 Comments that start with two semicolons, `;;', should be aligned to
439 the same level of indentation as the code. Such comments usually
440 describe the purpose of the following lines or the state of the
441 program at that point. For example:
443 (prog1 (setq auto-fill-function
449 Every function that has no documentation string (because it is use
450 only internally within the package it belongs to), should have
451 instead a two-semicolon comment right before the function,
452 explaining what the function does and how to call it properly.
453 Explain precisely what each argument means and how the function
454 interprets its possible values.
457 Comments that start with three semicolons, `;;;', should start at
458 the left margin. Such comments are used outside function
459 definitions to make general statements explaining the design
460 principles of the program. For example:
462 ;;; This Lisp code is run in XEmacs
463 ;;; when it is to operate as a server
464 ;;; for other processes.
466 Another use for triple-semicolon comments is for commenting out
467 lines within a function. We use triple-semicolons for this
468 precisely so that they remain at the left margin.
471 ;;; This is no longer necessary.
472 ;;; (force-mode-line-update)
473 (message "Finished with %s" a))
476 Comments that start with four semicolons, `;;;;', should be aligned
477 to the left margin and are used for headings of major sections of a
478 program. For example:
482 The indentation commands of the Lisp modes in XEmacs, such as `M-;'
483 (`indent-for-comment') and <TAB> (`lisp-indent-line') automatically
484 indent comments according to these conventions, depending on the number
485 of semicolons. *Note Manipulating Comments: (emacs)Comments.
488 File: lispref.info, Node: Library Headers, Prev: Comment Tips, Up: Tips
490 Conventional Headers for XEmacs Libraries
491 =========================================
493 XEmacs has conventions for using special comments in Lisp libraries
494 to divide them into sections and give information such as who wrote
495 them. This section explains these conventions. First, an example:
497 ;;; lisp-mnt.el --- minor mode for Emacs Lisp maintainers
499 ;; Copyright (C) 1992 Free Software Foundation, Inc.
501 ;; Author: Eric S. Raymond <esr@snark.thyrsus.com>
502 ;; Maintainer: Eric S. Raymond <esr@snark.thyrsus.com>
503 ;; Created: 14 Jul 1992
507 ;; This file is part of XEmacs.
508 COPYING PERMISSIONS...
510 The very first line should have this format:
512 ;;; FILENAME --- DESCRIPTION
514 The description should be complete in one line.
516 After the copyright notice come several "header comment" lines, each
517 beginning with `;; HEADER-NAME:'. Here is a table of the conventional
518 possibilities for HEADER-NAME:
521 This line states the name and net address of at least the principal
522 author of the library.
524 If there are multiple authors, you can list them on continuation
525 lines led by `;;' and a tab character, like this:
527 ;; Author: Ashwin Ram <Ram-Ashwin@cs.yale.edu>
528 ;; Dave Sill <de5@ornl.gov>
529 ;; Dave Brennan <brennan@hal.com>
530 ;; Eric Raymond <esr@snark.thyrsus.com>
533 This line should contain a single name/address as in the Author
534 line, or an address only, or the string `FSF'. If there is no
535 maintainer line, the person(s) in the Author field are presumed to
536 be the maintainers. The example above is mildly bogus because the
537 maintainer line is redundant.
539 The idea behind the `Author' and `Maintainer' lines is to make
540 possible a Lisp function to "send mail to the maintainer" without
541 having to mine the name out by hand.
543 Be sure to surround the network address with `<...>' if you
544 include the person's full name as well as the network address.
547 This optional line gives the original creation date of the file.
548 For historical interest only.
551 If you wish to record version numbers for the individual Lisp
552 program, put them in this line.
555 In this header line, place the name of the person who adapted the
556 library for installation (to make it fit the style conventions, for
560 This line lists keywords for the `finder-by-keyword' help command.
561 This field is important; it's how people will find your package
562 when they're looking for things by topic area. To separate the
563 keywords, you can use spaces, commas, or both.
565 Just about every Lisp library ought to have the `Author' and
566 `Keywords' header comment lines. Use the others if they are
567 appropriate. You can also put in header lines with other header
568 names--they have no standard meanings, so they can't do any harm.
570 We use additional stylized comments to subdivide the contents of the
571 library file. Here is a table of them:
574 This begins introductory comments that explain how the library
575 works. It should come right after the copying permissions.
578 This begins change log information stored in the library file (if
579 you store the change history there). For most of the Lisp files
580 distributed with XEmacs, the change history is kept in the file
581 `ChangeLog' and not in the source file at all; these files do not
582 have a `;;; Change log:' line.
585 This begins the actual code of the program.
587 `;;; FILENAME ends here'
588 This is the "footer line"; it appears at the very end of the file.
589 Its purpose is to enable people to detect truncated versions of
590 the file from the lack of a footer line.
593 File: lispref.info, Node: Building XEmacs and Object Allocation, Next: Standard Errors, Prev: Tips, Up: Top
595 Building XEmacs; Allocation of Objects
596 **************************************
598 This chapter describes how the runnable XEmacs executable is dumped
599 with the preloaded Lisp libraries in it and how storage is allocated.
601 There is an entire separate document, the `XEmacs Internals Manual',
602 devoted to the internals of XEmacs from the perspective of the C
603 programmer. It contains much more detailed information about the build
604 process, the allocation and garbage-collection process, and other
605 aspects related to the internals of XEmacs.
609 * Building XEmacs:: How to preload Lisp libraries into XEmacs.
610 * Pure Storage:: A kludge to make preloaded Lisp functions sharable.
611 * Garbage Collection:: Reclaiming space for Lisp objects no longer used.
614 File: lispref.info, Node: Building XEmacs, Next: Pure Storage, Up: Building XEmacs and Object Allocation
619 This section explains the steps involved in building the XEmacs
620 executable. You don't have to know this material to build and install
621 XEmacs, since the makefiles do all these things automatically. This
622 information is pertinent to XEmacs maintenance.
624 The `XEmacs Internals Manual' contains more information about this.
626 Compilation of the C source files in the `src' directory produces an
627 executable file called `temacs', also called a "bare impure XEmacs".
628 It contains the XEmacs Lisp interpreter and I/O routines, but not the
631 Before XEmacs is actually usable, a number of Lisp files need to be
632 loaded. These define all the editing commands, plus most of the startup
633 code and many very basic Lisp primitives. This is accomplished by
634 loading the file `loadup.el', which in turn loads all of the other
635 standardly-loaded Lisp files.
637 It takes a substantial time to load the standard Lisp files.
638 Luckily, you don't have to do this each time you run XEmacs; `temacs'
639 can dump out an executable program called `xemacs' that has these files
640 preloaded. `xemacs' starts more quickly because it does not need to
641 load the files. This is the XEmacs executable that is normally
644 To create `xemacs', use the command `temacs -batch -l loadup dump'.
645 The purpose of `-batch' here is to tell `temacs' to run in
646 non-interactive, command-line mode. (`temacs' can _only_ run in this
647 fashion. Part of the code required to initialize frames and faces is
648 in Lisp, and must be loaded before XEmacs is able to create any frames.)
649 The argument `dump' tells `loadup.el' to dump a new executable named
652 The dumping process is highly system-specific, and some operating
653 systems don't support dumping. On those systems, you must start XEmacs
654 with the `temacs -batch -l loadup run-temacs' command each time you use
655 it. This takes a substantial time, but since you need to start Emacs
656 once a day at most--or once a week if you never log out--the extra time
657 is not too severe a problem. (In older versions of Emacs, you started
658 Emacs from `temacs' using `temacs -l loadup'.)
660 You are free to start XEmacs directly from `temacs' if you want,
661 even if there is already a dumped `xemacs'. Normally you wouldn't want
662 to do that; but the Makefiles do this when you rebuild XEmacs using
663 `make all-elc', which builds XEmacs and simultaneously compiles any
664 out-of-date Lisp files. (You need `xemacs' in order to compile Lisp
665 files. However, you also need the compiled Lisp files in order to dump
666 out `xemacs'. If both of these are missing or corrupted, you are out
667 of luck unless you're able to bootstrap `xemacs' from `temacs'. Note
668 that `make all-elc' actually loads the alternative loadup file
669 `loadup-el.el', which works like `loadup.el' but disables the
670 pure-copying process and forces XEmacs to ignore any compiled Lisp
671 files even if they exist.)
673 You can specify additional files to preload by writing a library
674 named `site-load.el' that loads them. You may need to increase the
675 value of `PURESIZE', in `src/puresize.h', to make room for the
676 additional files. You should _not_ modify this file directly, however;
677 instead, use the `--puresize' configuration option. (If you run out of
678 pure space while dumping `xemacs', you will be told how much pure space
679 you actually will need.) However, the advantage of preloading
680 additional files decreases as machines get faster. On modern machines,
681 it is often not advisable, especially if the Lisp code is on a file
682 system local to the machine running XEmacs.
684 You can specify other Lisp expressions to execute just before dumping
685 by putting them in a library named `site-init.el'. However, if they
686 might alter the behavior that users expect from an ordinary unmodified
687 XEmacs, it is better to put them in `default.el', so that users can
688 override them if they wish. *Note Start-up Summary::.
690 Before `loadup.el' dumps the new executable, it finds the
691 documentation strings for primitive and preloaded functions (and
692 variables) in the file where they are stored, by calling
693 `Snarf-documentation' (*note Accessing Documentation::). These strings
694 were moved out of the `xemacs' executable to make it smaller. *Note
695 Documentation Basics::.
697 - Function: dump-emacs to-file from-file
698 This function dumps the current state of XEmacs into an executable
699 file TO-FILE. It takes symbols from FROM-FILE (this is normally
700 the executable file `temacs').
702 If you use this function in an XEmacs that was already dumped, you
703 must set `command-line-processed' to `nil' first for good results.
704 *Note Command Line Arguments::.
706 - Function: run-emacs-from-temacs &rest args
707 This is the function that implements the `run-temacs' command-line
708 argument. It is called from `loadup.el' as appropriate. You
709 should most emphatically _not_ call this yourself; it will
710 reinitialize your XEmacs process and you'll be sorry.
712 - Command: emacs-version
713 This function returns a string describing the version of XEmacs
714 that is running. It is useful to include this string in bug
718 => "XEmacs 20.1 [Lucid] (i586-unknown-linux2.0.29)
719 of Mon Apr 7 1997 on altair.xemacs.org"
721 Called interactively, the function prints the same information in
724 - Variable: emacs-build-time
725 The value of this variable is the time at which XEmacs was built
728 emacs-build-time "Mon Apr 7 20:28:52 1997"
731 - Variable: emacs-version
732 The value of this variable is the version of Emacs being run. It
733 is a string, e.g. `"20.1 XEmacs Lucid"'.
735 The following two variables did not exist before FSF GNU Emacs
736 version 19.23 and XEmacs version 19.10, which reduces their usefulness
737 at present, but we hope they will be convenient in the future.
739 - Variable: emacs-major-version
740 The major version number of Emacs, as an integer. For XEmacs
741 version 20.1, the value is 20.
743 - Variable: emacs-minor-version
744 The minor version number of Emacs, as an integer. For XEmacs
745 version 20.1, the value is 1.
748 File: lispref.info, Node: Pure Storage, Next: Garbage Collection, Prev: Building XEmacs, Up: Building XEmacs and Object Allocation
753 XEmacs Lisp uses two kinds of storage for user-created Lisp objects:
754 "normal storage" and "pure storage". Normal storage is where all the
755 new data created during an XEmacs session is kept; see the following
756 section for information on normal storage. Pure storage is used for
757 certain data in the preloaded standard Lisp files--data that should
758 never change during actual use of XEmacs.
760 Pure storage is allocated only while `temacs' is loading the
761 standard preloaded Lisp libraries. In the file `xemacs', it is marked
762 as read-only (on operating systems that permit this), so that the
763 memory space can be shared by all the XEmacs jobs running on the machine
764 at once. Pure storage is not expandable; a fixed amount is allocated
765 when XEmacs is compiled, and if that is not sufficient for the preloaded
766 libraries, `temacs' aborts with an error message. If that happens, you
767 must increase the compilation parameter `PURESIZE' using the
768 `--puresize' option to `configure'. This normally won't happen unless
769 you try to preload additional libraries or add features to the standard
772 - Function: purecopy object
773 This function makes a copy of OBJECT in pure storage and returns
774 it. It copies strings by simply making a new string with the same
775 characters in pure storage. It recursively copies the contents of
776 vectors and cons cells. It does not make copies of other objects
777 such as symbols, but just returns them unchanged. It signals an
778 error if asked to copy markers.
780 This function is a no-op except while XEmacs is being built and
781 dumped; it is usually called only in the file
782 `xemacs/lisp/prim/loaddefs.el', but a few packages call it just in
783 case you decide to preload them.
785 - Variable: pure-bytes-used
786 The value of this variable is the number of bytes of pure storage
787 allocated so far. Typically, in a dumped XEmacs, this number is
788 very close to the total amount of pure storage available--if it
789 were not, we would preallocate less.
791 - Variable: purify-flag
792 This variable determines whether `defun' should make a copy of the
793 function definition in pure storage. If it is non-`nil', then the
794 function definition is copied into pure storage.
796 This flag is `t' while loading all of the basic functions for
797 building XEmacs initially (allowing those functions to be sharable
798 and non-collectible). Dumping XEmacs as an executable always
799 writes `nil' in this variable, regardless of the value it actually
800 has before and after dumping.
802 You should not change this flag in a running XEmacs.
805 File: lispref.info, Node: Garbage Collection, Prev: Pure Storage, Up: Building XEmacs and Object Allocation
810 When a program creates a list or the user defines a new function
811 (such as by loading a library), that data is placed in normal storage.
812 If normal storage runs low, then XEmacs asks the operating system to
813 allocate more memory in blocks of 2k bytes. Each block is used for one
814 type of Lisp object, so symbols, cons cells, markers, etc., are
815 segregated in distinct blocks in memory. (Vectors, long strings,
816 buffers and certain other editing types, which are fairly large, are
817 allocated in individual blocks, one per object, while small strings are
818 packed into blocks of 8k bytes. [More correctly, a string is allocated
819 in two sections: a fixed size chunk containing the length, list of
820 extents, etc.; and a chunk containing the actual characters in the
821 string. It is this latter chunk that is either allocated individually
822 or packed into 8k blocks. The fixed size chunk is packed into 2k
823 blocks, as for conses, markers, etc.])
825 It is quite common to use some storage for a while, then release it
826 by (for example) killing a buffer or deleting the last pointer to an
827 object. XEmacs provides a "garbage collector" to reclaim this
828 abandoned storage. (This name is traditional, but "garbage recycler"
829 might be a more intuitive metaphor for this facility.)
831 The garbage collector operates by finding and marking all Lisp
832 objects that are still accessible to Lisp programs. To begin with, it
833 assumes all the symbols, their values and associated function
834 definitions, and any data presently on the stack, are accessible. Any
835 objects that can be reached indirectly through other accessible objects
838 When marking is finished, all objects still unmarked are garbage. No
839 matter what the Lisp program or the user does, it is impossible to refer
840 to them, since there is no longer a way to reach them. Their space
841 might as well be reused, since no one will miss them. The second
842 ("sweep") phase of the garbage collector arranges to reuse them.
844 The sweep phase puts unused cons cells onto a "free list" for future
845 allocation; likewise for symbols, markers, extents, events, floats,
846 compiled-function objects, and the fixed-size portion of strings. It
847 compacts the accessible small string-chars chunks so they occupy fewer
848 8k blocks; then it frees the other 8k blocks. Vectors, buffers,
849 windows, and other large objects are individually allocated and freed
850 using `malloc' and `free'.
852 Common Lisp note: unlike other Lisps, XEmacs Lisp does not call
853 the garbage collector when the free list is empty. Instead, it
854 simply requests the operating system to allocate more storage, and
855 processing continues until `gc-cons-threshold' bytes have been
858 This means that you can make sure that the garbage collector will
859 not run during a certain portion of a Lisp program by calling the
860 garbage collector explicitly just before it (provided that portion
861 of the program does not use so much space as to force a second
864 - Command: garbage-collect
865 This command runs a garbage collection, and returns information on
866 the amount of space in use. (Garbage collection can also occur
867 spontaneously if you use more than `gc-cons-threshold' bytes of
868 Lisp data since the previous garbage collection.)
870 `garbage-collect' returns a list containing the following
873 ((USED-CONSES . FREE-CONSES)
874 (USED-SYMS . FREE-SYMS)
875 (USED-MARKERS . FREE-MARKERS)
880 => ((73362 . 8325) (13718 . 164)
881 (5089 . 5098) 949121 118677
882 (conses-used 73362 conses-free 8329 cons-storage 658168
883 symbols-used 13718 symbols-free 164 symbol-storage 335216
884 bit-vectors-used 0 bit-vectors-total-length 0
885 bit-vector-storage 0 vectors-used 7882
886 vectors-total-length 118677 vector-storage 537764
887 compiled-functions-used 1336 compiled-functions-free 37
888 compiled-function-storage 44440 short-strings-used 28829
889 long-strings-used 2 strings-free 7722
890 short-strings-total-length 916657 short-string-storage 1179648
891 long-strings-total-length 32464 string-header-storage 441504
892 floats-used 3 floats-free 43 float-storage 2044 markers-used 5089
893 markers-free 5098 marker-storage 245280 events-used 103
894 events-free 835 event-storage 110656 extents-used 10519
895 extents-free 2718 extent-storage 372736
896 extent-auxiliarys-used 111 extent-auxiliarys-freed 3
897 extent-auxiliary-storage 4440 window-configurations-used 39
898 window-configurations-on-free-list 5
899 window-configurations-freed 10 window-configuration-storage 9492
900 popup-datas-used 3 popup-data-storage 72 toolbar-buttons-used 62
901 toolbar-button-storage 4960 toolbar-datas-used 12
902 toolbar-data-storage 240 symbol-value-buffer-locals-used 182
903 symbol-value-buffer-local-storage 5824
904 symbol-value-lisp-magics-used 22
905 symbol-value-lisp-magic-storage 1496
906 symbol-value-varaliases-used 43
907 symbol-value-varalias-storage 1032 opaque-lists-used 2
908 opaque-list-storage 48 color-instances-used 12
909 color-instance-storage 288 font-instances-used 5
910 font-instance-storage 180 opaques-used 11 opaque-storage 312
911 range-tables-used 1 range-table-storage 16 faces-used 34
912 face-storage 2584 glyphs-used 124 glyph-storage 4464
913 specifiers-used 775 specifier-storage 43869 weak-lists-used 786
914 weak-list-storage 18864 char-tables-used 40
915 char-table-storage 41920 buffers-used 25 buffer-storage 7000
916 extent-infos-used 457 extent-infos-freed 73
917 extent-info-storage 9140 keymaps-used 275 keymap-storage 12100
918 consoles-used 4 console-storage 384 command-builders-used 2
919 command-builder-storage 120 devices-used 2 device-storage 344
920 frames-used 3 frame-storage 624 image-instances-used 47
921 image-instance-storage 3008 windows-used 27 windows-freed 2
922 window-storage 9180 lcrecord-lists-used 15
923 lcrecord-list-storage 360 hash-tables-used 631
924 hash-table-storage 25240 streams-used 1 streams-on-free-list 3
925 streams-freed 12 stream-storage 91))
927 Here is a table explaining each element:
930 The number of cons cells in use.
933 The number of cons cells for which space has been obtained
934 from the operating system, but that are not currently being
938 The number of symbols in use.
941 The number of symbols for which space has been obtained from
942 the operating system, but that are not currently being used.
945 The number of markers in use.
948 The number of markers for which space has been obtained from
949 the operating system, but that are not currently being used.
952 The total size of all strings, in characters.
955 The total number of elements of existing vectors.
958 A list of alternating keyword/value pairs providing more
959 detailed information. (As you can see above, quite a lot of
960 information is provided.)
962 - User Option: gc-cons-threshold
963 The value of this variable is the number of bytes of storage that
964 must be allocated for Lisp objects after one garbage collection in
965 order to trigger another garbage collection. A cons cell counts
966 as eight bytes, a string as one byte per character plus a few
967 bytes of overhead, and so on; space allocated to the contents of
968 buffers does not count. Note that the subsequent garbage
969 collection does not happen immediately when the threshold is
970 exhausted, but only the next time the Lisp evaluator is called.
972 The initial threshold value is 500,000. If you specify a larger
973 value, garbage collection will happen less often. This reduces the
974 amount of time spent garbage collecting, but increases total
975 memory use. You may want to do this when running a program that
976 creates lots of Lisp data.
978 You can make collections more frequent by specifying a smaller
979 value, down to 10,000. A value less than 10,000 will remain in
980 effect only until the subsequent garbage collection, at which time
981 `garbage-collect' will set the threshold back to 10,000. (This does
982 not apply if XEmacs was configured with `--debug'. Therefore, be
983 careful when setting `gc-cons-threshold' in that case!)
985 - Function: memory-limit
986 This function returns the address of the last byte XEmacs has
987 allocated, divided by 1024. We divide the value by 1024 to make
988 sure it fits in a Lisp integer.
990 You can use this to get a general idea of how your actions affect
993 - Variable: pre-gc-hook
994 This is a normal hook to be run just before each garbage
995 collection. Interrupts, garbage collection, and errors are
996 inhibited while this hook runs, so be extremely careful in what
997 you add here. In particular, avoid consing, and do not interact
1000 - Variable: post-gc-hook
1001 This is a normal hook to be run just after each garbage collection.
1002 Interrupts, garbage collection, and errors are inhibited while
1003 this hook runs, so be extremely careful in what you add here. In
1004 particular, avoid consing, and do not interact with the user.
1006 - Variable: gc-message
1007 This is a string to print to indicate that a garbage collection is
1008 in progress. This is printed in the echo area. If the selected
1009 frame is on a window system and `gc-pointer-glyph' specifies a
1010 value (i.e. a pointer image instance) in the domain of the
1011 selected frame, the mouse cursor will change instead of this
1012 message being printed.
1014 - Glyph: gc-pointer-glyph
1015 This holds the pointer glyph used to indicate that a garbage
1016 collection is in progress. If the selected window is on a window
1017 system and this glyph specifies a value (i.e. a pointer image
1018 instance) in the domain of the selected window, the cursor will be
1019 changed as specified during garbage collection. Otherwise, a
1020 message will be printed in the echo area, as controlled by
1021 `gc-message'. *Note Glyphs::.
1023 If XEmacs was configured with `--debug', you can set the following
1024 two variables to get direct information about all the allocation that
1025 is happening in a segment of Lisp code.
1027 - Variable: debug-allocation
1028 If non-zero, print out information to stderr about all objects
1031 - Variable: debug-allocation-backtrace
1032 Length (in stack frames) of short backtrace printed out by
1036 File: lispref.info, Node: Standard Errors, Next: Standard Buffer-Local Variables, Prev: Building XEmacs and Object Allocation, Up: Top
1041 Here is the complete list of the error symbols in standard Emacs,
1042 grouped by concept. The list includes each symbol's message (on the
1043 `error-message' property of the symbol) and a cross reference to a
1044 description of how the error can occur.
1046 Each error symbol has an `error-conditions' property that is a list
1047 of symbols. Normally this list includes the error symbol itself and
1048 the symbol `error'. Occasionally it includes additional symbols, which
1049 are intermediate classifications, narrower than `error' but broader
1050 than a single error symbol. For example, all the errors in accessing
1051 files have the condition `file-error'.
1053 As a special exception, the error symbol `quit' does not have the
1054 condition `error', because quitting is not considered an error.
1056 *Note Errors::, for an explanation of how errors are generated and
1071 `"Args out of range"'
1072 *Note Sequences Arrays Vectors::.
1075 `"Arithmetic error"'
1076 See `/' and `%' in *Note Numbers::.
1078 `beginning-of-buffer'
1079 `"Beginning of buffer"'
1083 `"Buffer is read-only"'
1084 *Note Read Only Buffers::.
1086 `cyclic-function-indirection'
1087 `"Symbol's chain of function indirections contains a loop"'
1088 *Note Function Indirection::.
1091 `"Arithmetic domain error"'
1097 `"End of file during parsing"'
1098 This is not a `file-error'.
1099 *Note Input Functions::.
1102 This error and its subcategories do not have error-strings,
1103 because the error message is constructed from the data items alone
1104 when the error condition `file-error' is present.
1108 This is a `file-error'.
1111 `file-already-exists'
1112 This is a `file-error'.
1113 *Note Writing to Files::.
1116 This is a `file-error'.
1117 *Note Modification Time::.
1120 `"Invalid byte code"'
1121 *Note Byte Compilation::.
1124 `"Invalid function"'
1125 *Note Classifying Lists::.
1127 `invalid-read-syntax'
1128 `"Invalid read syntax"'
1129 *Note Input Functions::.
1133 *Note Regular Expressions::.
1136 `"The mark is not active now"'
1138 `"No catch for tag"'
1139 *Note Catch and Throw::.
1142 `"Arithmetic overflow error"'
1144 `"Attempt to modify a protected field"'
1146 `"Arithmetic range error"'
1149 *Note Searching and Matching::.
1152 `"Attempt to set a constant symbol"'
1153 *Note Variables that Never Change: Constant Variables.
1156 `"Arithmetic singularity error"'
1159 *Note ToolTalk Support::.
1161 `undefined-keystroke-sequence'
1162 `"Undefined keystroke sequence"'
1164 `"Symbol's function definition is void"'
1165 *Note Function Cells::.
1168 `"Symbol's value as variable is void"'
1169 *Note Accessing Variables::.
1171 `wrong-number-of-arguments'
1172 `"Wrong number of arguments"'
1173 *Note Classifying Lists::.
1175 `wrong-type-argument'
1176 `"Wrong type argument"'
1177 *Note Type Predicates::.
1179 These error types, which are all classified as special cases of
1180 `arith-error', can occur on certain systems for invalid use of
1181 mathematical functions.
1184 `"Arithmetic domain error"'
1185 *Note Math Functions::.
1188 `"Arithmetic overflow error"'
1189 *Note Math Functions::.
1192 `"Arithmetic range error"'
1193 *Note Math Functions::.
1196 `"Arithmetic singularity error"'
1197 *Note Math Functions::.
1200 `"Arithmetic underflow error"'
1201 *Note Math Functions::.
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