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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
29157371 | 3 | @c Copyright (C) 1990-1993, 1998-1999, 2001-2012 Free Software Foundation, Inc. |
b8d4c8d0 | 4 | @c See the file elisp.texi for copying conditions. |
6336d8c3 | 5 | @setfilename ../../info/internals |
b8d4c8d0 GM |
6 | @node GNU Emacs Internals, Standard Errors, Tips, Top |
7 | @comment node-name, next, previous, up | |
8 | @appendix GNU Emacs Internals | |
9 | ||
10 | This chapter describes how the runnable Emacs executable is dumped with | |
11 | the preloaded Lisp libraries in it, how storage is allocated, and some | |
12 | internal aspects of GNU Emacs that may be of interest to C programmers. | |
13 | ||
14 | @menu | |
15 | * Building Emacs:: How the dumped Emacs is made. | |
333f9019 | 16 | * Pure Storage:: Kludge to make preloaded Lisp functions shareable. |
b8d4c8d0 GM |
17 | * Garbage Collection:: Reclaiming space for Lisp objects no longer used. |
18 | * Memory Usage:: Info about total size of Lisp objects made so far. | |
19 | * Writing Emacs Primitives:: Writing C code for Emacs. | |
20 | * Object Internals:: Data formats of buffers, windows, processes. | |
21 | @end menu | |
22 | ||
23 | @node Building Emacs | |
520f2425 | 24 | @section Building Emacs |
b8d4c8d0 GM |
25 | @cindex building Emacs |
26 | @pindex temacs | |
27 | ||
28 | This section explains the steps involved in building the Emacs | |
29 | executable. You don't have to know this material to build and install | |
30 | Emacs, since the makefiles do all these things automatically. This | |
31 | information is pertinent to Emacs maintenance. | |
32 | ||
33 | Compilation of the C source files in the @file{src} directory | |
34 | produces an executable file called @file{temacs}, also called a | |
35 | @dfn{bare impure Emacs}. It contains the Emacs Lisp interpreter and I/O | |
36 | routines, but not the editing commands. | |
37 | ||
38 | @cindex @file{loadup.el} | |
39 | The command @w{@samp{temacs -l loadup}} uses @file{temacs} to create | |
40 | the real runnable Emacs executable. These arguments direct | |
41 | @file{temacs} to evaluate the Lisp files specified in the file | |
42 | @file{loadup.el}. These files set up the normal Emacs editing | |
43 | environment, resulting in an Emacs that is still impure but no longer | |
44 | bare. | |
45 | ||
46 | @cindex dumping Emacs | |
520f2425 | 47 | It takes some time to load the standard Lisp files. Luckily, |
b8d4c8d0 GM |
48 | you don't have to do this each time you run Emacs; @file{temacs} can |
49 | dump out an executable program called @file{emacs} that has these files | |
50 | preloaded. @file{emacs} starts more quickly because it does not need to | |
51 | load the files. This is the Emacs executable that is normally | |
52 | installed. | |
53 | ||
b578c9cc GM |
54 | @vindex preloaded-file-list |
55 | @cindex dumped Lisp files | |
b8d4c8d0 GM |
56 | To create @file{emacs}, use the command @samp{temacs -batch -l loadup |
57 | dump}. The purpose of @samp{-batch} here is to prevent @file{temacs} | |
58 | from trying to initialize any of its data on the terminal; this ensures | |
59 | that the tables of terminal information are empty in the dumped Emacs. | |
60 | The argument @samp{dump} tells @file{loadup.el} to dump a new executable | |
b578c9cc GM |
61 | named @file{emacs}. The variable @code{preloaded-file-list} stores a |
62 | list of the Lisp files that were dumped with the @file{emacs} executable. | |
b8d4c8d0 | 63 | |
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64 | If you port Emacs to a new operating system, and are not able to |
65 | implement dumping, then Emacs must load @file{loadup.el} each time it | |
66 | starts. | |
b8d4c8d0 GM |
67 | |
68 | @cindex @file{site-load.el} | |
b8d4c8d0 | 69 | You can specify additional files to preload by writing a library named |
520f2425 GM |
70 | @file{site-load.el} that loads them. You may need to rebuild Emacs |
71 | with an added definition | |
b8d4c8d0 GM |
72 | |
73 | @example | |
74 | #define SITELOAD_PURESIZE_EXTRA @var{n} | |
75 | @end example | |
76 | ||
77 | @noindent | |
520f2425 GM |
78 | to make @var{n} added bytes of pure space to hold the additional files; |
79 | see @file{src/puresize.h}. | |
b8d4c8d0 GM |
80 | (Try adding increments of 20000 until it is big enough.) However, the |
81 | advantage of preloading additional files decreases as machines get | |
82 | faster. On modern machines, it is usually not advisable. | |
83 | ||
84 | After @file{loadup.el} reads @file{site-load.el}, it finds the | |
85 | documentation strings for primitive and preloaded functions (and | |
86 | variables) in the file @file{etc/DOC} where they are stored, by | |
87 | calling @code{Snarf-documentation} (@pxref{Definition of | |
88 | Snarf-documentation,, Accessing Documentation}). | |
89 | ||
90 | @cindex @file{site-init.el} | |
91 | @cindex preloading additional functions and variables | |
92 | You can specify other Lisp expressions to execute just before dumping | |
93 | by putting them in a library named @file{site-init.el}. This file is | |
94 | executed after the documentation strings are found. | |
95 | ||
96 | If you want to preload function or variable definitions, there are | |
97 | three ways you can do this and make their documentation strings | |
98 | accessible when you subsequently run Emacs: | |
99 | ||
100 | @itemize @bullet | |
101 | @item | |
102 | Arrange to scan these files when producing the @file{etc/DOC} file, | |
103 | and load them with @file{site-load.el}. | |
104 | ||
105 | @item | |
106 | Load the files with @file{site-init.el}, then copy the files into the | |
107 | installation directory for Lisp files when you install Emacs. | |
108 | ||
109 | @item | |
5906db45 GM |
110 | Specify a @code{nil} value for @code{byte-compile-dynamic-docstrings} |
111 | as a local variable in each of these files, and load them with either | |
112 | @file{site-load.el} or @file{site-init.el}. (This method has the | |
113 | drawback that the documentation strings take up space in Emacs all the | |
114 | time.) | |
b8d4c8d0 GM |
115 | @end itemize |
116 | ||
117 | It is not advisable to put anything in @file{site-load.el} or | |
118 | @file{site-init.el} that would alter any of the features that users | |
119 | expect in an ordinary unmodified Emacs. If you feel you must override | |
120 | normal features for your site, do it with @file{default.el}, so that | |
121 | users can override your changes if they wish. @xref{Startup Summary}. | |
122 | ||
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123 | In a package that can be preloaded, it is sometimes necessary (or |
124 | useful) to delay certain evaluations until Emacs subsequently starts | |
125 | up. The vast majority of such cases relate to the values of | |
126 | customizable variables. For example, @code{tutorial-directory} is a | |
127 | variable defined in @file{startup.el}, which is preloaded. The default | |
128 | value is set based on @code{data-directory}. The variable needs to | |
129 | access the value of @code{data-directory} when Emacs starts, not when | |
130 | it is dumped, because the Emacs executable has probably been installed | |
131 | in a different location since it was dumped. | |
132 | ||
133 | @defun custom-initialize-delay symbol value | |
134 | This function delays the initialization of @var{symbol} to the next | |
135 | Emacs start. You normally use this function by specifying it as the | |
136 | @code{:initialize} property of a customizable variable. (The argument | |
137 | @var{value} is unused, and is provided only for compatiblity with the | |
138 | form Custom expects.) | |
139 | @end defun | |
b8d4c8d0 | 140 | |
520f2425 GM |
141 | In the unlikely event that you need a more general functionality than |
142 | @code{custom-initialize-delay} provides, you can use | |
143 | @code{before-init-hook} (@pxref{Startup Summary}). | |
b8d4c8d0 GM |
144 | |
145 | @defun dump-emacs to-file from-file | |
146 | @cindex unexec | |
147 | This function dumps the current state of Emacs into an executable file | |
148 | @var{to-file}. It takes symbols from @var{from-file} (this is normally | |
149 | the executable file @file{temacs}). | |
150 | ||
151 | If you want to use this function in an Emacs that was already dumped, | |
152 | you must run Emacs with @samp{-batch}. | |
153 | @end defun | |
154 | ||
155 | @node Pure Storage | |
520f2425 | 156 | @section Pure Storage |
b8d4c8d0 GM |
157 | @cindex pure storage |
158 | ||
159 | Emacs Lisp uses two kinds of storage for user-created Lisp objects: | |
160 | @dfn{normal storage} and @dfn{pure storage}. Normal storage is where | |
999dd333 GM |
161 | all the new data created during an Emacs session are kept |
162 | (@pxref{Garbage Collection}). Pure storage is used for certain data | |
163 | in the preloaded standard Lisp files---data that should never change | |
164 | during actual use of Emacs. | |
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165 | |
166 | Pure storage is allocated only while @file{temacs} is loading the | |
167 | standard preloaded Lisp libraries. In the file @file{emacs}, it is | |
168 | marked as read-only (on operating systems that permit this), so that | |
169 | the memory space can be shared by all the Emacs jobs running on the | |
170 | machine at once. Pure storage is not expandable; a fixed amount is | |
171 | allocated when Emacs is compiled, and if that is not sufficient for | |
172 | the preloaded libraries, @file{temacs} allocates dynamic memory for | |
999dd333 GM |
173 | the part that didn't fit. The resulting image will work, but garbage |
174 | collection (@pxref{Garbage Collection}) is disabled in this situation, | |
175 | causing a memory leak. Such an overflow normally won't happen unless | |
176 | you try to preload additional libraries or add features to the | |
177 | standard ones. Emacs will display a warning about the overflow when | |
178 | it starts. If this happens, you should increase the compilation | |
179 | parameter @code{SYSTEM_PURESIZE_EXTRA} in the file | |
180 | @file{src/puresize.h} and rebuild Emacs. | |
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181 | |
182 | @defun purecopy object | |
183 | This function makes a copy in pure storage of @var{object}, and returns | |
184 | it. It copies a string by simply making a new string with the same | |
185 | characters, but without text properties, in pure storage. It | |
186 | recursively copies the contents of vectors and cons cells. It does | |
187 | not make copies of other objects such as symbols, but just returns | |
188 | them unchanged. It signals an error if asked to copy markers. | |
189 | ||
190 | This function is a no-op except while Emacs is being built and dumped; | |
999dd333 | 191 | it is usually called only in preloaded Lisp files. |
b8d4c8d0 GM |
192 | @end defun |
193 | ||
194 | @defvar pure-bytes-used | |
195 | The value of this variable is the number of bytes of pure storage | |
196 | allocated so far. Typically, in a dumped Emacs, this number is very | |
197 | close to the total amount of pure storage available---if it were not, | |
198 | we would preallocate less. | |
199 | @end defvar | |
200 | ||
201 | @defvar purify-flag | |
202 | This variable determines whether @code{defun} should make a copy of the | |
203 | function definition in pure storage. If it is non-@code{nil}, then the | |
204 | function definition is copied into pure storage. | |
205 | ||
206 | This flag is @code{t} while loading all of the basic functions for | |
333f9019 | 207 | building Emacs initially (allowing those functions to be shareable and |
b8d4c8d0 GM |
208 | non-collectible). Dumping Emacs as an executable always writes |
209 | @code{nil} in this variable, regardless of the value it actually has | |
210 | before and after dumping. | |
211 | ||
212 | You should not change this flag in a running Emacs. | |
213 | @end defvar | |
214 | ||
215 | @node Garbage Collection | |
520f2425 | 216 | @section Garbage Collection |
b8d4c8d0 GM |
217 | @cindex garbage collection |
218 | ||
219 | @cindex memory allocation | |
220 | When a program creates a list or the user defines a new function (such | |
221 | as by loading a library), that data is placed in normal storage. If | |
222 | normal storage runs low, then Emacs asks the operating system to | |
223 | allocate more memory in blocks of 1k bytes. Each block is used for one | |
224 | type of Lisp object, so symbols, cons cells, markers, etc., are | |
225 | segregated in distinct blocks in memory. (Vectors, long strings, | |
226 | buffers and certain other editing types, which are fairly large, are | |
227 | allocated in individual blocks, one per object, while small strings are | |
228 | packed into blocks of 8k bytes.) | |
229 | ||
230 | It is quite common to use some storage for a while, then release it by | |
231 | (for example) killing a buffer or deleting the last pointer to an | |
232 | object. Emacs provides a @dfn{garbage collector} to reclaim this | |
233 | abandoned storage. (This name is traditional, but ``garbage recycler'' | |
234 | might be a more intuitive metaphor for this facility.) | |
235 | ||
236 | The garbage collector operates by finding and marking all Lisp objects | |
237 | that are still accessible to Lisp programs. To begin with, it assumes | |
238 | all the symbols, their values and associated function definitions, and | |
239 | any data presently on the stack, are accessible. Any objects that can | |
240 | be reached indirectly through other accessible objects are also | |
241 | accessible. | |
242 | ||
243 | When marking is finished, all objects still unmarked are garbage. No | |
244 | matter what the Lisp program or the user does, it is impossible to refer | |
245 | to them, since there is no longer a way to reach them. Their space | |
246 | might as well be reused, since no one will miss them. The second | |
247 | (``sweep'') phase of the garbage collector arranges to reuse them. | |
248 | ||
249 | @c ??? Maybe add something describing weak hash tables here? | |
250 | ||
251 | @cindex free list | |
252 | The sweep phase puts unused cons cells onto a @dfn{free list} | |
253 | for future allocation; likewise for symbols and markers. It compacts | |
254 | the accessible strings so they occupy fewer 8k blocks; then it frees the | |
255 | other 8k blocks. Vectors, buffers, windows, and other large objects are | |
256 | individually allocated and freed using @code{malloc} and @code{free}. | |
257 | ||
258 | @cindex CL note---allocate more storage | |
259 | @quotation | |
260 | @b{Common Lisp note:} Unlike other Lisps, GNU Emacs Lisp does not | |
261 | call the garbage collector when the free list is empty. Instead, it | |
262 | simply requests the operating system to allocate more storage, and | |
263 | processing continues until @code{gc-cons-threshold} bytes have been | |
264 | used. | |
265 | ||
266 | This means that you can make sure that the garbage collector will not | |
267 | run during a certain portion of a Lisp program by calling the garbage | |
268 | collector explicitly just before it (provided that portion of the | |
269 | program does not use so much space as to force a second garbage | |
270 | collection). | |
271 | @end quotation | |
272 | ||
273 | @deffn Command garbage-collect | |
274 | This command runs a garbage collection, and returns information on | |
275 | the amount of space in use. (Garbage collection can also occur | |
276 | spontaneously if you use more than @code{gc-cons-threshold} bytes of | |
277 | Lisp data since the previous garbage collection.) | |
278 | ||
279 | @code{garbage-collect} returns a list containing the following | |
280 | information: | |
281 | ||
282 | @example | |
283 | @group | |
284 | ((@var{used-conses} . @var{free-conses}) | |
285 | (@var{used-syms} . @var{free-syms}) | |
286 | @end group | |
287 | (@var{used-miscs} . @var{free-miscs}) | |
288 | @var{used-string-chars} | |
289 | @var{used-vector-slots} | |
290 | (@var{used-floats} . @var{free-floats}) | |
291 | (@var{used-intervals} . @var{free-intervals}) | |
292 | (@var{used-strings} . @var{free-strings})) | |
293 | @end example | |
294 | ||
295 | Here is an example: | |
296 | ||
297 | @example | |
298 | @group | |
299 | (garbage-collect) | |
300 | @result{} ((106886 . 13184) (9769 . 0) | |
301 | (7731 . 4651) 347543 121628 | |
302 | (31 . 94) (1273 . 168) | |
303 | (25474 . 3569)) | |
304 | @end group | |
305 | @end example | |
306 | ||
307 | Here is a table explaining each element: | |
308 | ||
309 | @table @var | |
310 | @item used-conses | |
311 | The number of cons cells in use. | |
312 | ||
313 | @item free-conses | |
314 | The number of cons cells for which space has been obtained from the | |
315 | operating system, but that are not currently being used. | |
316 | ||
317 | @item used-syms | |
318 | The number of symbols in use. | |
319 | ||
320 | @item free-syms | |
321 | The number of symbols for which space has been obtained from the | |
322 | operating system, but that are not currently being used. | |
323 | ||
324 | @item used-miscs | |
325 | The number of miscellaneous objects in use. These include markers and | |
326 | overlays, plus certain objects not visible to users. | |
327 | ||
328 | @item free-miscs | |
329 | The number of miscellaneous objects for which space has been obtained | |
330 | from the operating system, but that are not currently being used. | |
331 | ||
332 | @item used-string-chars | |
333 | The total size of all strings, in characters. | |
334 | ||
335 | @item used-vector-slots | |
336 | The total number of elements of existing vectors. | |
337 | ||
338 | @item used-floats | |
339 | @c Emacs 19 feature | |
340 | The number of floats in use. | |
341 | ||
342 | @item free-floats | |
343 | @c Emacs 19 feature | |
344 | The number of floats for which space has been obtained from the | |
345 | operating system, but that are not currently being used. | |
346 | ||
347 | @item used-intervals | |
348 | The number of intervals in use. Intervals are an internal | |
349 | data structure used for representing text properties. | |
350 | ||
351 | @item free-intervals | |
352 | The number of intervals for which space has been obtained | |
353 | from the operating system, but that are not currently being used. | |
354 | ||
355 | @item used-strings | |
356 | The number of strings in use. | |
357 | ||
358 | @item free-strings | |
359 | The number of string headers for which the space was obtained from the | |
360 | operating system, but which are currently not in use. (A string | |
361 | object consists of a header and the storage for the string text | |
362 | itself; the latter is only allocated when the string is created.) | |
363 | @end table | |
364 | ||
999dd333 | 365 | If there was overflow in pure space (@pxref{Pure Storage}), |
b8d4c8d0 GM |
366 | @code{garbage-collect} returns @code{nil}, because a real garbage |
367 | collection can not be done in this situation. | |
368 | @end deffn | |
369 | ||
370 | @defopt garbage-collection-messages | |
371 | If this variable is non-@code{nil}, Emacs displays a message at the | |
372 | beginning and end of garbage collection. The default value is | |
999dd333 | 373 | @code{nil}. |
b8d4c8d0 GM |
374 | @end defopt |
375 | ||
376 | @defvar post-gc-hook | |
377 | This is a normal hook that is run at the end of garbage collection. | |
378 | Garbage collection is inhibited while the hook functions run, so be | |
379 | careful writing them. | |
380 | @end defvar | |
381 | ||
382 | @defopt gc-cons-threshold | |
383 | The value of this variable is the number of bytes of storage that must | |
384 | be allocated for Lisp objects after one garbage collection in order to | |
385 | trigger another garbage collection. A cons cell counts as eight bytes, | |
386 | a string as one byte per character plus a few bytes of overhead, and so | |
387 | on; space allocated to the contents of buffers does not count. Note | |
388 | that the subsequent garbage collection does not happen immediately when | |
389 | the threshold is exhausted, but only the next time the Lisp evaluator is | |
390 | called. | |
391 | ||
999dd333 | 392 | The initial threshold value is 800,000. If you specify a larger |
b8d4c8d0 GM |
393 | value, garbage collection will happen less often. This reduces the |
394 | amount of time spent garbage collecting, but increases total memory use. | |
395 | You may want to do this when running a program that creates lots of | |
396 | Lisp data. | |
397 | ||
398 | You can make collections more frequent by specifying a smaller value, | |
399 | down to 10,000. A value less than 10,000 will remain in effect only | |
400 | until the subsequent garbage collection, at which time | |
401 | @code{garbage-collect} will set the threshold back to 10,000. | |
402 | @end defopt | |
403 | ||
404 | @defopt gc-cons-percentage | |
405 | The value of this variable specifies the amount of consing before a | |
406 | garbage collection occurs, as a fraction of the current heap size. | |
407 | This criterion and @code{gc-cons-threshold} apply in parallel, and | |
408 | garbage collection occurs only when both criteria are satisfied. | |
409 | ||
410 | As the heap size increases, the time to perform a garbage collection | |
411 | increases. Thus, it can be desirable to do them less frequently in | |
412 | proportion. | |
413 | @end defopt | |
414 | ||
415 | The value returned by @code{garbage-collect} describes the amount of | |
416 | memory used by Lisp data, broken down by data type. By contrast, the | |
417 | function @code{memory-limit} provides information on the total amount of | |
418 | memory Emacs is currently using. | |
419 | ||
420 | @c Emacs 19 feature | |
421 | @defun memory-limit | |
422 | This function returns the address of the last byte Emacs has allocated, | |
423 | divided by 1024. We divide the value by 1024 to make sure it fits in a | |
424 | Lisp integer. | |
425 | ||
426 | You can use this to get a general idea of how your actions affect the | |
427 | memory usage. | |
428 | @end defun | |
429 | ||
430 | @defvar memory-full | |
431 | This variable is @code{t} if Emacs is close to out of memory for Lisp | |
432 | objects, and @code{nil} otherwise. | |
433 | @end defvar | |
434 | ||
435 | @defun memory-use-counts | |
436 | This returns a list of numbers that count the number of objects | |
437 | created in this Emacs session. Each of these counters increments for | |
438 | a certain kind of object. See the documentation string for details. | |
439 | @end defun | |
440 | ||
441 | @defvar gcs-done | |
442 | This variable contains the total number of garbage collections | |
443 | done so far in this Emacs session. | |
444 | @end defvar | |
445 | ||
446 | @defvar gc-elapsed | |
447 | This variable contains the total number of seconds of elapsed time | |
448 | during garbage collection so far in this Emacs session, as a floating | |
449 | point number. | |
450 | @end defvar | |
451 | ||
452 | @node Memory Usage | |
453 | @section Memory Usage | |
454 | @cindex memory usage | |
455 | ||
456 | These functions and variables give information about the total amount | |
457 | of memory allocation that Emacs has done, broken down by data type. | |
458 | Note the difference between these and the values returned by | |
01a6dcc8 | 459 | @code{garbage-collect}; those count objects that currently exist, but |
b8d4c8d0 GM |
460 | these count the number or size of all allocations, including those for |
461 | objects that have since been freed. | |
462 | ||
463 | @defvar cons-cells-consed | |
464 | The total number of cons cells that have been allocated so far | |
465 | in this Emacs session. | |
466 | @end defvar | |
467 | ||
468 | @defvar floats-consed | |
469 | The total number of floats that have been allocated so far | |
470 | in this Emacs session. | |
471 | @end defvar | |
472 | ||
473 | @defvar vector-cells-consed | |
474 | The total number of vector cells that have been allocated so far | |
475 | in this Emacs session. | |
476 | @end defvar | |
477 | ||
478 | @defvar symbols-consed | |
479 | The total number of symbols that have been allocated so far | |
480 | in this Emacs session. | |
481 | @end defvar | |
482 | ||
483 | @defvar string-chars-consed | |
484 | The total number of string characters that have been allocated so far | |
485 | in this Emacs session. | |
486 | @end defvar | |
487 | ||
488 | @defvar misc-objects-consed | |
489 | The total number of miscellaneous objects that have been allocated so | |
490 | far in this Emacs session. These include markers and overlays, plus | |
491 | certain objects not visible to users. | |
492 | @end defvar | |
493 | ||
494 | @defvar intervals-consed | |
495 | The total number of intervals that have been allocated so far | |
496 | in this Emacs session. | |
497 | @end defvar | |
498 | ||
499 | @defvar strings-consed | |
500 | The total number of strings that have been allocated so far in this | |
501 | Emacs session. | |
502 | @end defvar | |
503 | ||
504 | @node Writing Emacs Primitives | |
520f2425 | 505 | @section Writing Emacs Primitives |
b8d4c8d0 GM |
506 | @cindex primitive function internals |
507 | @cindex writing Emacs primitives | |
508 | ||
509 | Lisp primitives are Lisp functions implemented in C. The details of | |
510 | interfacing the C function so that Lisp can call it are handled by a few | |
511 | C macros. The only way to really understand how to write new C code is | |
512 | to read the source, but we can explain some things here. | |
513 | ||
514 | An example of a special form is the definition of @code{or}, from | |
515 | @file{eval.c}. (An ordinary function would have the same general | |
516 | appearance.) | |
517 | ||
518 | @cindex garbage collection protection | |
519 | @smallexample | |
520 | @group | |
521 | DEFUN ("or", For, Sor, 0, UNEVALLED, 0, | |
522 | doc: /* Eval args until one of them yields non-nil, then return that | |
520f2425 | 523 | value. The remaining args are not evalled at all. |
b8d4c8d0 GM |
524 | If all args return nil, return nil. |
525 | @end group | |
526 | @group | |
527 | usage: (or CONDITIONS ...) */) | |
b88746ba | 528 | (Lisp_Object args) |
b8d4c8d0 GM |
529 | @{ |
530 | register Lisp_Object val = Qnil; | |
531 | struct gcpro gcpro1; | |
532 | @end group | |
533 | ||
534 | @group | |
535 | GCPRO1 (args); | |
536 | @end group | |
537 | ||
538 | @group | |
539 | while (CONSP (args)) | |
540 | @{ | |
7d2d7cc0 | 541 | val = eval_sub (XCAR (args)); |
b8d4c8d0 GM |
542 | if (!NILP (val)) |
543 | break; | |
544 | args = XCDR (args); | |
545 | @} | |
546 | @end group | |
547 | ||
548 | @group | |
549 | UNGCPRO; | |
550 | return val; | |
551 | @} | |
552 | @end group | |
553 | @end smallexample | |
554 | ||
555 | @cindex @code{DEFUN}, C macro to define Lisp primitives | |
556 | Let's start with a precise explanation of the arguments to the | |
557 | @code{DEFUN} macro. Here is a template for them: | |
558 | ||
559 | @example | |
560 | DEFUN (@var{lname}, @var{fname}, @var{sname}, @var{min}, @var{max}, @var{interactive}, @var{doc}) | |
561 | @end example | |
562 | ||
563 | @table @var | |
564 | @item lname | |
565 | This is the name of the Lisp symbol to define as the function name; in | |
566 | the example above, it is @code{or}. | |
567 | ||
568 | @item fname | |
569 | This is the C function name for this function. This is | |
570 | the name that is used in C code for calling the function. The name is, | |
571 | by convention, @samp{F} prepended to the Lisp name, with all dashes | |
572 | (@samp{-}) in the Lisp name changed to underscores. Thus, to call this | |
573 | function from C code, call @code{For}. Remember that the arguments must | |
574 | be of type @code{Lisp_Object}; various macros and functions for creating | |
575 | values of type @code{Lisp_Object} are declared in the file | |
576 | @file{lisp.h}. | |
577 | ||
578 | @item sname | |
579 | This is a C variable name to use for a structure that holds the data for | |
580 | the subr object that represents the function in Lisp. This structure | |
581 | conveys the Lisp symbol name to the initialization routine that will | |
582 | create the symbol and store the subr object as its definition. By | |
583 | convention, this name is always @var{fname} with @samp{F} replaced with | |
584 | @samp{S}. | |
585 | ||
586 | @item min | |
587 | This is the minimum number of arguments that the function requires. The | |
588 | function @code{or} allows a minimum of zero arguments. | |
589 | ||
590 | @item max | |
591 | This is the maximum number of arguments that the function accepts, if | |
592 | there is a fixed maximum. Alternatively, it can be @code{UNEVALLED}, | |
593 | indicating a special form that receives unevaluated arguments, or | |
594 | @code{MANY}, indicating an unlimited number of evaluated arguments (the | |
595 | equivalent of @code{&rest}). Both @code{UNEVALLED} and @code{MANY} are | |
596 | macros. If @var{max} is a number, it may not be less than @var{min} and | |
597 | it may not be greater than eight. | |
598 | ||
599 | @item interactive | |
600 | This is an interactive specification, a string such as might be used as | |
601 | the argument of @code{interactive} in a Lisp function. In the case of | |
602 | @code{or}, it is 0 (a null pointer), indicating that @code{or} cannot be | |
603 | called interactively. A value of @code{""} indicates a function that | |
2c30e468 EZ |
604 | should receive no arguments when called interactively. If the value |
605 | begins with a @samp{(}, the string is evaluated as a Lisp form. | |
7d2d7cc0 GM |
606 | For examples of the last two forms, see @code{widen} and |
607 | @code{narrow-to-region} in @file{editfns.c}. | |
b8d4c8d0 GM |
608 | |
609 | @item doc | |
610 | This is the documentation string. It uses C comment syntax rather | |
611 | than C string syntax because comment syntax requires nothing special | |
612 | to include multiple lines. The @samp{doc:} identifies the comment | |
613 | that follows as the documentation string. The @samp{/*} and @samp{*/} | |
614 | delimiters that begin and end the comment are not part of the | |
615 | documentation string. | |
616 | ||
617 | If the last line of the documentation string begins with the keyword | |
618 | @samp{usage:}, the rest of the line is treated as the argument list | |
619 | for documentation purposes. This way, you can use different argument | |
620 | names in the documentation string from the ones used in the C code. | |
621 | @samp{usage:} is required if the function has an unlimited number of | |
622 | arguments. | |
623 | ||
624 | All the usual rules for documentation strings in Lisp code | |
625 | (@pxref{Documentation Tips}) apply to C code documentation strings | |
626 | too. | |
627 | @end table | |
628 | ||
b88746ba EZ |
629 | After the call to the @code{DEFUN} macro, you must write the |
630 | argument list that every C function must have, including the types for | |
631 | the arguments. For a function with a fixed maximum number of | |
632 | arguments, declare a C argument for each Lisp argument, and give them | |
633 | all type @code{Lisp_Object}. When a Lisp function has no upper limit | |
634 | on the number of arguments, its implementation in C actually receives | |
635 | exactly two arguments: the first is the number of Lisp arguments, and | |
636 | the second is the address of a block containing their values. They | |
637 | have types @code{int} and @w{@code{Lisp_Object *}}. | |
b8d4c8d0 GM |
638 | |
639 | @cindex @code{GCPRO} and @code{UNGCPRO} | |
640 | @cindex protect C variables from garbage collection | |
641 | Within the function @code{For} itself, note the use of the macros | |
642 | @code{GCPRO1} and @code{UNGCPRO}. @code{GCPRO1} is used to | |
643 | ``protect'' a variable from garbage collection---to inform the garbage | |
644 | collector that it must look in that variable and regard its contents | |
645 | as an accessible object. GC protection is necessary whenever you call | |
7d2d7cc0 GM |
646 | @code{eval_sub} (or @code{Feval}) either directly or indirectly. |
647 | At such a time, any Lisp object that this function may refer to again | |
648 | must be protected somehow. | |
b8d4c8d0 GM |
649 | |
650 | It suffices to ensure that at least one pointer to each object is | |
651 | GC-protected; that way, the object cannot be recycled, so all pointers | |
652 | to it remain valid. Thus, a particular local variable can do without | |
653 | protection if it is certain that the object it points to will be | |
7d2d7cc0 GM |
654 | preserved by some other pointer (such as another local variable that |
655 | has a @code{GCPRO}). | |
656 | @ignore | |
657 | @footnote{Formerly, strings were a special exception; in older Emacs | |
658 | versions, every local variable that might point to a string needed a | |
659 | @code{GCPRO}.}. | |
660 | @end ignore | |
661 | Otherwise, the local variable needs a @code{GCPRO}. | |
b8d4c8d0 GM |
662 | |
663 | The macro @code{GCPRO1} protects just one local variable. If you | |
664 | want to protect two variables, use @code{GCPRO2} instead; repeating | |
665 | @code{GCPRO1} will not work. Macros @code{GCPRO3}, @code{GCPRO4}, | |
666 | @code{GCPRO5}, and @code{GCPRO6} also exist. All these macros | |
667 | implicitly use local variables such as @code{gcpro1}; you must declare | |
668 | these explicitly, with type @code{struct gcpro}. Thus, if you use | |
669 | @code{GCPRO2}, you must declare @code{gcpro1} and @code{gcpro2}. | |
670 | Alas, we can't explain all the tricky details here. | |
671 | ||
672 | @code{UNGCPRO} cancels the protection of the variables that are | |
673 | protected in the current function. It is necessary to do this | |
674 | explicitly. | |
675 | ||
676 | Built-in functions that take a variable number of arguments actually | |
677 | accept two arguments at the C level: the number of Lisp arguments, and | |
678 | a @code{Lisp_Object *} pointer to a C vector containing those Lisp | |
679 | arguments. This C vector may be part of a Lisp vector, but it need | |
680 | not be. The responsibility for using @code{GCPRO} to protect the Lisp | |
681 | arguments from GC if necessary rests with the caller in this case, | |
682 | since the caller allocated or found the storage for them. | |
683 | ||
684 | You must not use C initializers for static or global variables unless | |
685 | the variables are never written once Emacs is dumped. These variables | |
686 | with initializers are allocated in an area of memory that becomes | |
687 | read-only (on certain operating systems) as a result of dumping Emacs. | |
688 | @xref{Pure Storage}. | |
689 | ||
7d2d7cc0 | 690 | @c FIXME is this still true? I don't think so... |
b8d4c8d0 GM |
691 | Do not use static variables within functions---place all static |
692 | variables at top level in the file. This is necessary because Emacs on | |
693 | some operating systems defines the keyword @code{static} as a null | |
694 | macro. (This definition is used because those systems put all variables | |
695 | declared static in a place that becomes read-only after dumping, whether | |
696 | they have initializers or not.) | |
697 | ||
698 | @cindex @code{defsubr}, Lisp symbol for a primitive | |
699 | Defining the C function is not enough to make a Lisp primitive | |
700 | available; you must also create the Lisp symbol for the primitive and | |
701 | store a suitable subr object in its function cell. The code looks like | |
702 | this: | |
703 | ||
704 | @example | |
7d2d7cc0 | 705 | defsubr (&@var{sname}); |
b8d4c8d0 GM |
706 | @end example |
707 | ||
708 | @noindent | |
7d2d7cc0 | 709 | Here @var{sname} is the name you used as the third argument to @code{DEFUN}. |
b8d4c8d0 GM |
710 | |
711 | If you add a new primitive to a file that already has Lisp primitives | |
712 | defined in it, find the function (near the end of the file) named | |
713 | @code{syms_of_@var{something}}, and add the call to @code{defsubr} | |
714 | there. If the file doesn't have this function, or if you create a new | |
715 | file, add to it a @code{syms_of_@var{filename}} (e.g., | |
716 | @code{syms_of_myfile}). Then find the spot in @file{emacs.c} where all | |
717 | of these functions are called, and add a call to | |
718 | @code{syms_of_@var{filename}} there. | |
719 | ||
720 | @anchor{Defining Lisp variables in C} | |
721 | @vindex byte-boolean-vars | |
722 | @cindex defining Lisp variables in C | |
723 | @cindex @code{DEFVAR_INT}, @code{DEFVAR_LISP}, @code{DEFVAR_BOOL} | |
724 | The function @code{syms_of_@var{filename}} is also the place to define | |
725 | any C variables that are to be visible as Lisp variables. | |
726 | @code{DEFVAR_LISP} makes a C variable of type @code{Lisp_Object} visible | |
727 | in Lisp. @code{DEFVAR_INT} makes a C variable of type @code{int} | |
728 | visible in Lisp with a value that is always an integer. | |
729 | @code{DEFVAR_BOOL} makes a C variable of type @code{int} visible in Lisp | |
730 | with a value that is either @code{t} or @code{nil}. Note that variables | |
731 | defined with @code{DEFVAR_BOOL} are automatically added to the list | |
732 | @code{byte-boolean-vars} used by the byte compiler. | |
733 | ||
7d2d7cc0 GM |
734 | @cindex defining customization variables in C |
735 | If you want to make a Lisp variables that is defined in C behave | |
736 | like one declared with @code{defcustom}, add an appropriate entry to | |
737 | @file{cus-start.el}. | |
738 | ||
b8d4c8d0 GM |
739 | @cindex @code{staticpro}, protection from GC |
740 | If you define a file-scope C variable of type @code{Lisp_Object}, | |
741 | you must protect it from garbage-collection by calling @code{staticpro} | |
742 | in @code{syms_of_@var{filename}}, like this: | |
743 | ||
744 | @example | |
745 | staticpro (&@var{variable}); | |
746 | @end example | |
747 | ||
748 | Here is another example function, with more complicated arguments. | |
749 | This comes from the code in @file{window.c}, and it demonstrates the use | |
750 | of macros and functions to manipulate Lisp objects. | |
751 | ||
752 | @smallexample | |
753 | @group | |
754 | DEFUN ("coordinates-in-window-p", Fcoordinates_in_window_p, | |
7d2d7cc0 GM |
755 | Scoordinates_in_window_p, 2, 2, 0, |
756 | doc: /* Return non-nil if COORDINATES are in WINDOW. | |
757 | ... | |
b8d4c8d0 GM |
758 | @end group |
759 | @group | |
7d2d7cc0 GM |
760 | or `right-margin' is returned. */) |
761 | (register Lisp_Object coordinates, Lisp_Object window) | |
b8d4c8d0 | 762 | @{ |
7d2d7cc0 GM |
763 | struct window *w; |
764 | struct frame *f; | |
b8d4c8d0 | 765 | int x, y; |
7d2d7cc0 | 766 | Lisp_Object lx, ly; |
b8d4c8d0 GM |
767 | @end group |
768 | ||
769 | @group | |
7d2d7cc0 GM |
770 | CHECK_LIVE_WINDOW (window); |
771 | w = XWINDOW (window); | |
772 | f = XFRAME (w->frame); | |
773 | CHECK_CONS (coordinates); | |
774 | lx = Fcar (coordinates); | |
775 | ly = Fcdr (coordinates); | |
776 | CHECK_NUMBER_OR_FLOAT (lx); | |
777 | CHECK_NUMBER_OR_FLOAT (ly); | |
778 | x = FRAME_PIXEL_X_FROM_CANON_X (f, lx) + FRAME_INTERNAL_BORDER_WIDTH(f); | |
779 | y = FRAME_PIXEL_Y_FROM_CANON_Y (f, ly) + FRAME_INTERNAL_BORDER_WIDTH(f); | |
b8d4c8d0 GM |
780 | @end group |
781 | ||
782 | @group | |
7d2d7cc0 | 783 | switch (coordinates_in_window (w, x, y)) |
b8d4c8d0 | 784 | @{ |
7d2d7cc0 | 785 | case ON_NOTHING: /* NOT in window at all. */ |
b8d4c8d0 GM |
786 | return Qnil; |
787 | @end group | |
788 | ||
7d2d7cc0 | 789 | ... |
b8d4c8d0 GM |
790 | |
791 | @group | |
7d2d7cc0 | 792 | case ON_MODE_LINE: /* In mode line of window. */ |
b8d4c8d0 GM |
793 | return Qmode_line; |
794 | @end group | |
795 | ||
7d2d7cc0 GM |
796 | ... |
797 | ||
b8d4c8d0 | 798 | @group |
7d2d7cc0 GM |
799 | case ON_SCROLL_BAR: /* On scroll-bar of window. */ |
800 | /* Historically we are supposed to return nil in this case. */ | |
801 | return Qnil; | |
b8d4c8d0 GM |
802 | @end group |
803 | ||
804 | @group | |
805 | default: | |
806 | abort (); | |
807 | @} | |
808 | @} | |
809 | @end group | |
810 | @end smallexample | |
811 | ||
812 | Note that C code cannot call functions by name unless they are defined | |
813 | in C. The way to call a function written in Lisp is to use | |
814 | @code{Ffuncall}, which embodies the Lisp function @code{funcall}. Since | |
815 | the Lisp function @code{funcall} accepts an unlimited number of | |
816 | arguments, in C it takes two: the number of Lisp-level arguments, and a | |
817 | one-dimensional array containing their values. The first Lisp-level | |
818 | argument is the Lisp function to call, and the rest are the arguments to | |
819 | pass to it. Since @code{Ffuncall} can call the evaluator, you must | |
820 | protect pointers from garbage collection around the call to | |
821 | @code{Ffuncall}. | |
822 | ||
823 | The C functions @code{call0}, @code{call1}, @code{call2}, and so on, | |
824 | provide handy ways to call a Lisp function conveniently with a fixed | |
825 | number of arguments. They work by calling @code{Ffuncall}. | |
826 | ||
827 | @file{eval.c} is a very good file to look through for examples; | |
828 | @file{lisp.h} contains the definitions for some important macros and | |
829 | functions. | |
830 | ||
831 | If you define a function which is side-effect free, update the code | |
7d2d7cc0 | 832 | in @file{byte-opt.el} that binds @code{side-effect-free-fns} and |
b8d4c8d0 GM |
833 | @code{side-effect-and-error-free-fns} so that the compiler optimizer |
834 | knows about it. | |
835 | ||
836 | @node Object Internals | |
520f2425 | 837 | @section Object Internals |
b8d4c8d0 GM |
838 | @cindex object internals |
839 | ||
7d2d7cc0 | 840 | @c FIXME Is this still true? Does --with-wide-int affect anything? |
b8d4c8d0 GM |
841 | GNU Emacs Lisp manipulates many different types of data. The actual |
842 | data are stored in a heap and the only access that programs have to it | |
c773345a CY |
843 | is through pointers. Each pointer is 32 bits wide on 32-bit machines, |
844 | and 64 bits wide on 64-bit machines; three of these bits are used for | |
845 | the tag that identifies the object's type, and the remainder are used | |
846 | to address the object. | |
b8d4c8d0 GM |
847 | |
848 | Because Lisp objects are represented as tagged pointers, it is always | |
849 | possible to determine the Lisp data type of any object. The C data type | |
850 | @code{Lisp_Object} can hold any Lisp object of any data type. Ordinary | |
851 | variables have type @code{Lisp_Object}, which means they can hold any | |
852 | type of Lisp value; you can determine the actual data type only at run | |
853 | time. The same is true for function arguments; if you want a function | |
854 | to accept only a certain type of argument, you must check the type | |
855 | explicitly using a suitable predicate (@pxref{Type Predicates}). | |
856 | @cindex type checking internals | |
857 | ||
858 | @menu | |
859 | * Buffer Internals:: Components of a buffer structure. | |
860 | * Window Internals:: Components of a window structure. | |
861 | * Process Internals:: Components of a process structure. | |
862 | @end menu | |
863 | ||
864 | @node Buffer Internals | |
520f2425 | 865 | @subsection Buffer Internals |
b8d4c8d0 GM |
866 | @cindex internals, of buffer |
867 | @cindex buffer internals | |
868 | ||
7d2d7cc0 GM |
869 | Two structures (see @file{buffer.h}) are used to represent buffers |
870 | in C. The @code{buffer_text} structure contains fields describing the | |
871 | text of a buffer; the @code{buffer} structure holds other fields. In | |
872 | the case of indirect buffers, two or more @code{buffer} structures | |
873 | reference the same @code{buffer_text} structure. | |
b8d4c8d0 | 874 | |
c773345a | 875 | Here are some of the fields in @code{struct buffer_text}: |
b8d4c8d0 GM |
876 | |
877 | @table @code | |
878 | @item beg | |
c773345a | 879 | The address of the buffer contents. |
b8d4c8d0 GM |
880 | |
881 | @item gpt | |
c773345a CY |
882 | @itemx gpt_byte |
883 | The character and byte positions of the buffer gap. @xref{Buffer | |
884 | Gap}. | |
b8d4c8d0 GM |
885 | |
886 | @item z | |
c773345a CY |
887 | @itemx z_byte |
888 | The character and byte positions of the end of the buffer text. | |
b8d4c8d0 GM |
889 | |
890 | @item gap_size | |
c773345a | 891 | The size of buffer's gap. @xref{Buffer Gap}. |
b8d4c8d0 GM |
892 | |
893 | @item modiff | |
c773345a CY |
894 | @itemx save_modiff |
895 | @itemx chars_modiff | |
896 | @itemx overlay_modiff | |
897 | These fields count the number of buffer-modification events performed | |
898 | in this buffer. @code{modiff} is incremented after each | |
899 | buffer-modification event, and is never otherwise changed; | |
900 | @code{save_modiff} contains the value of @code{modiff} the last time | |
901 | the buffer was visited or saved; @code{chars_modiff} counts only | |
902 | modifications to the characters in the buffer, ignoring all other | |
903 | kinds of changes; and @code{overlay_modiff} counts only modifications | |
904 | to the overlays. | |
b8d4c8d0 GM |
905 | |
906 | @item beg_unchanged | |
c773345a CY |
907 | @itemx end_unchanged |
908 | The number of characters at the start and end of the text that are | |
909 | known to be unchanged since the last complete redisplay. | |
b8d4c8d0 GM |
910 | |
911 | @item unchanged_modified | |
c773345a CY |
912 | @itemx overlay_unchanged_modified |
913 | The values of @code{modiff} and @code{overlay_modiff}, respectively, | |
da6062e6 | 914 | after the last complete redisplay. If their current values match |
c773345a | 915 | @code{modiff} or @code{overlay_modiff}, that means |
b8d4c8d0 GM |
916 | @code{beg_unchanged} and @code{end_unchanged} contain no useful |
917 | information. | |
918 | ||
919 | @item markers | |
920 | The markers that refer to this buffer. This is actually a single | |
921 | marker, and successive elements in its marker @code{chain} are the other | |
922 | markers referring to this buffer text. | |
923 | ||
924 | @item intervals | |
c773345a | 925 | The interval tree which records the text properties of this buffer. |
b8d4c8d0 GM |
926 | @end table |
927 | ||
c773345a | 928 | Some of the fields of @code{struct buffer} are: |
b8d4c8d0 GM |
929 | |
930 | @table @code | |
7d2d7cc0 GM |
931 | @item header |
932 | A @code{struct vectorlike_header} structure where @code{header.next} | |
933 | points to the next buffer, in the chain of all buffers (including | |
c773345a CY |
934 | killed buffers). This chain is used only for garbage collection, in |
935 | order to collect killed buffers properly. Note that vectors, and most | |
936 | kinds of objects allocated as vectors, are all on one chain, but | |
937 | buffers are on a separate chain of their own. | |
b8d4c8d0 GM |
938 | |
939 | @item own_text | |
c773345a CY |
940 | A @code{struct buffer_text} structure that ordinarily holds the buffer |
941 | contents. In indirect buffers, this field is not used. | |
b8d4c8d0 GM |
942 | |
943 | @item text | |
c773345a CY |
944 | A pointer to the @code{buffer_text} structure for this buffer. In an |
945 | ordinary buffer, this is the @code{own_text} field above. In an | |
946 | indirect buffer, this is the @code{own_text} field of the base buffer. | |
b8d4c8d0 GM |
947 | |
948 | @item pt | |
c773345a CY |
949 | @itemx pt_byte |
950 | The character and byte positions of point in a buffer. | |
b8d4c8d0 GM |
951 | |
952 | @item begv | |
c773345a CY |
953 | @itemx begv_byte |
954 | The character and byte positions of the beginning of the accessible | |
955 | range of text in the buffer. | |
b8d4c8d0 GM |
956 | |
957 | @item zv | |
c773345a CY |
958 | @itemx zv_byte |
959 | The character and byte positions of the end of the accessible range of | |
960 | text in the buffer. | |
b8d4c8d0 GM |
961 | |
962 | @item base_buffer | |
963 | In an indirect buffer, this points to the base buffer. In an ordinary | |
964 | buffer, it is null. | |
965 | ||
c773345a CY |
966 | @item local_flags |
967 | This field contains flags indicating that certain variables are local | |
968 | in this buffer. Such variables are declared in the C code using | |
969 | @code{DEFVAR_PER_BUFFER}, and their buffer-local bindings are stored | |
970 | in fields in the buffer structure itself. (Some of these fields are | |
b8d4c8d0 GM |
971 | described in this table.) |
972 | ||
973 | @item modtime | |
c773345a CY |
974 | The modification time of the visited file. It is set when the file is |
975 | written or read. Before writing the buffer into a file, this field is | |
976 | compared to the modification time of the file to see if the file has | |
977 | changed on disk. @xref{Buffer Modification}. | |
b8d4c8d0 GM |
978 | |
979 | @item auto_save_modified | |
c773345a | 980 | The time when the buffer was last auto-saved. |
b8d4c8d0 GM |
981 | |
982 | @item last_window_start | |
c773345a CY |
983 | The @code{window-start} position in the buffer as of the last time the |
984 | buffer was displayed in a window. | |
b8d4c8d0 GM |
985 | |
986 | @item clip_changed | |
c773345a CY |
987 | This flag indicates that narrowing has changed in the buffer. |
988 | @xref{Narrowing}. | |
b8d4c8d0 GM |
989 | |
990 | @item prevent_redisplay_optimizations_p | |
c773345a CY |
991 | This flag indicates that redisplay optimizations should not be used to |
992 | display this buffer. | |
b8d4c8d0 | 993 | |
c773345a CY |
994 | @item overlay_center |
995 | This field holds the current overlay center position. @xref{Managing | |
996 | Overlays}. | |
997 | ||
998 | @item overlays_before | |
999 | @itemx overlays_after | |
1000 | These fields hold, respectively, a list of overlays that end at or | |
1001 | before the current overlay center, and a list of overlays that end | |
1002 | after the current overlay center. @xref{Managing Overlays}. | |
1003 | @code{overlays_before} is sorted in order of decreasing end position, | |
1004 | and @code{overlays_after} is sorted in order of increasing beginning | |
1005 | position. | |
b8d4c8d0 | 1006 | |
7d2d7cc0 GM |
1007 | @c FIXME? the following are now all Lisp_Object BUFFER_INTERNAL_FIELD (foo). |
1008 | ||
b8d4c8d0 | 1009 | @item name |
c773345a CY |
1010 | A Lisp string that names the buffer. It is guaranteed to be unique. |
1011 | @xref{Buffer Names}. | |
b8d4c8d0 | 1012 | |
c773345a CY |
1013 | @item save_length |
1014 | The length of the file this buffer is visiting, when last read or | |
1015 | saved. This and other fields concerned with saving are not kept in | |
1016 | the @code{buffer_text} structure because indirect buffers are never | |
1017 | saved. | |
b8d4c8d0 GM |
1018 | |
1019 | @item directory | |
c773345a CY |
1020 | The directory for expanding relative file names. This is the value of |
1021 | the buffer-local variable @code{default-directory} (@pxref{File Name Expansion}). | |
b8d4c8d0 | 1022 | |
c773345a CY |
1023 | @item filename |
1024 | The name of the file visited in this buffer, or @code{nil}. This is | |
1025 | the value of the buffer-local variable @code{buffer-file-name} | |
1026 | (@pxref{Buffer File Name}). | |
b8d4c8d0 | 1027 | |
c773345a CY |
1028 | @item undo_list |
1029 | @itemx backed_up | |
1030 | @itemx auto_save_file_name | |
7d2d7cc0 | 1031 | @itemx auto_save_file_format |
c773345a CY |
1032 | @itemx read_only |
1033 | @itemx file_format | |
1034 | @itemx file_truename | |
1035 | @itemx invisibility_spec | |
1036 | @itemx display_count | |
1037 | @itemx display_time | |
1038 | These fields store the values of Lisp variables that are automatically | |
1039 | buffer-local (@pxref{Buffer-Local Variables}), whose corresponding | |
1040 | variable names have the additional prefix @code{buffer-} and have | |
1041 | underscores replaced with dashes. For instance, @code{undo_list} | |
29157371 | 1042 | stores the value of @code{buffer-undo-list}. |
b8d4c8d0 GM |
1043 | |
1044 | @item mark | |
c773345a CY |
1045 | The mark for the buffer. The mark is a marker, hence it is also |
1046 | included on the list @code{markers}. @xref{The Mark}. | |
b8d4c8d0 GM |
1047 | |
1048 | @item local_var_alist | |
c773345a CY |
1049 | The association list describing the buffer-local variable bindings of |
1050 | this buffer, not including the built-in buffer-local bindings that | |
1051 | have special slots in the buffer object. (Those slots are omitted | |
1052 | from this table.) @xref{Buffer-Local Variables}. | |
b8d4c8d0 GM |
1053 | |
1054 | @item major_mode | |
1055 | Symbol naming the major mode of this buffer, e.g., @code{lisp-mode}. | |
1056 | ||
1057 | @item mode_name | |
c773345a | 1058 | Pretty name of the major mode, e.g., @code{"Lisp"}. |
b8d4c8d0 GM |
1059 | |
1060 | @item keymap | |
c773345a CY |
1061 | @itemx abbrev_table |
1062 | @itemx syntax_table | |
1063 | @itemx category_table | |
1064 | @itemx display_table | |
1065 | These fields store the buffer's local keymap (@pxref{Keymaps}), abbrev | |
1066 | table (@pxref{Abbrev Tables}), syntax table (@pxref{Syntax Tables}), | |
1067 | category table (@pxref{Categories}), and display table (@pxref{Display | |
1068 | Tables}). | |
b8d4c8d0 GM |
1069 | |
1070 | @item downcase_table | |
c773345a CY |
1071 | @itemx upcase_table |
1072 | @itemx case_canon_table | |
1073 | These fields store the conversion tables for converting text to lower | |
1074 | case, upper case, and for canonicalizing text for case-fold search. | |
b8d4c8d0 GM |
1075 | @xref{Case Tables}. |
1076 | ||
b8d4c8d0 GM |
1077 | @item minor_modes |
1078 | An alist of the minor modes of this buffer. | |
1079 | ||
b8d4c8d0 | 1080 | @item pt_marker |
c773345a CY |
1081 | @itemx begv_marker |
1082 | @itemx zv_marker | |
1083 | These fields are only used in an indirect buffer, or in a buffer that | |
1084 | is the base of an indirect buffer. Each holds a marker that records | |
1085 | @code{pt}, @code{begv}, and @code{zv} respectively, for this buffer | |
b8d4c8d0 GM |
1086 | when the buffer is not current. |
1087 | ||
c773345a CY |
1088 | @item mode_line_format |
1089 | @itemx header_line_format | |
1090 | @itemx case_fold_search | |
1091 | @itemx tab_width | |
1092 | @itemx fill_column | |
1093 | @itemx left_margin | |
1094 | @itemx auto_fill_function | |
c773345a CY |
1095 | @itemx truncate_lines |
1096 | @itemx word_wrap | |
1097 | @itemx ctl_arrow | |
7d2d7cc0 GM |
1098 | @itemx bidi_display_reordering |
1099 | @itemx bidi_paragraph_direction | |
c773345a CY |
1100 | @itemx selective_display |
1101 | @itemx selective_display_ellipses | |
1102 | @itemx overwrite_mode | |
1103 | @itemx abbrev_mode | |
c773345a CY |
1104 | @itemx mark_active |
1105 | @itemx enable_multibyte_characters | |
1106 | @itemx buffer_file_coding_system | |
c773345a CY |
1107 | @itemx cache_long_line_scans |
1108 | @itemx point_before_scroll | |
1109 | @itemx left_fringe_width | |
1110 | @itemx right_fringe_width | |
1111 | @itemx fringes_outside_margins | |
1112 | @itemx scroll_bar_width | |
1113 | @itemx indicate_empty_lines | |
1114 | @itemx indicate_buffer_boundaries | |
1115 | @itemx fringe_indicator_alist | |
1116 | @itemx fringe_cursor_alist | |
1117 | @itemx scroll_up_aggressively | |
1118 | @itemx scroll_down_aggressively | |
1119 | @itemx cursor_type | |
1120 | @itemx cursor_in_non_selected_windows | |
1121 | These fields store the values of Lisp variables that are automatically | |
1122 | buffer-local (@pxref{Buffer-Local Variables}), whose corresponding | |
1123 | variable names have underscores replaced with dashes. For instance, | |
1124 | @code{mode_line_format} stores the value of @code{mode-line-format}. | |
b8d4c8d0 GM |
1125 | |
1126 | @item last_selected_window | |
1127 | This is the last window that was selected with this buffer in it, or @code{nil} | |
1128 | if that window no longer displays this buffer. | |
b8d4c8d0 GM |
1129 | @end table |
1130 | ||
1131 | @node Window Internals | |
520f2425 | 1132 | @subsection Window Internals |
b8d4c8d0 GM |
1133 | @cindex internals, of window |
1134 | @cindex window internals | |
1135 | ||
7d2d7cc0 GM |
1136 | The fields of a window (for a complete list, see the definition of |
1137 | @code{struct window} in @file{window.h}) include: | |
b8d4c8d0 GM |
1138 | |
1139 | @table @code | |
1140 | @item frame | |
1141 | The frame that this window is on. | |
1142 | ||
1143 | @item mini_p | |
1144 | Non-@code{nil} if this window is a minibuffer window. | |
1145 | ||
1146 | @item parent | |
1147 | Internally, Emacs arranges windows in a tree; each group of siblings has | |
1148 | a parent window whose area includes all the siblings. This field points | |
1149 | to a window's parent. | |
1150 | ||
1151 | Parent windows do not display buffers, and play little role in display | |
1152 | except to shape their child windows. Emacs Lisp programs usually have | |
1153 | no access to the parent windows; they operate on the windows at the | |
1154 | leaves of the tree, which actually display buffers. | |
1155 | ||
b8d4c8d0 | 1156 | @item hchild |
ee2d5b5e CY |
1157 | @itemx vchild |
1158 | These fields contain the window's leftmost child and its topmost child | |
1159 | respectively. @code{hchild} is used if the window is subdivided | |
1160 | horizontally by child windows, and @code{vchild} if it is subdivided | |
7d2d7cc0 GM |
1161 | vertically. In a live window, only one of @code{hchild}, @code{vchild}, |
1162 | and @code{buffer} (q.v.) is non-@code{nil}. | |
b8d4c8d0 GM |
1163 | |
1164 | @item next | |
ee2d5b5e CY |
1165 | @itemx prev |
1166 | The next sibling and previous sibling of this window. @code{next} is | |
520f2425 GM |
1167 | @code{nil} if the window is the right-most or bottom-most in its group; |
1168 | @code{prev} is @code{nil} if it is the left-most or top-most in its | |
ee2d5b5e CY |
1169 | group. |
1170 | ||
1171 | @item left_col | |
1172 | The left-hand edge of the window, measured in columns, relative to the | |
1173 | leftmost column in the frame (column 0). | |
1174 | ||
1175 | @item top_line | |
1176 | The top edge of the window, measured in lines, relative to the topmost | |
1177 | line in the frame (line 0). | |
1178 | ||
1179 | @item total_cols | |
1180 | @itemx total_lines | |
1181 | The width and height of the window, measured in columns and lines | |
1182 | respectively. The width includes the scroll bar and fringes, and/or | |
1183 | the separator line on the right of the window (if any). | |
b8d4c8d0 GM |
1184 | |
1185 | @item buffer | |
ee2d5b5e | 1186 | The buffer that the window is displaying. |
b8d4c8d0 GM |
1187 | |
1188 | @item start | |
ee2d5b5e CY |
1189 | A marker pointing to the position in the buffer that is the first |
1190 | character displayed in the window. | |
b8d4c8d0 GM |
1191 | |
1192 | @item pointm | |
1193 | @cindex window point internals | |
1194 | This is the value of point in the current buffer when this window is | |
1195 | selected; when it is not selected, it retains its previous value. | |
1196 | ||
1197 | @item force_start | |
1198 | If this flag is non-@code{nil}, it says that the window has been | |
1199 | scrolled explicitly by the Lisp program. This affects what the next | |
1200 | redisplay does if point is off the screen: instead of scrolling the | |
1201 | window to show the text around point, it moves point to a location that | |
1202 | is on the screen. | |
1203 | ||
1204 | @item frozen_window_start_p | |
1205 | This field is set temporarily to 1 to indicate to redisplay that | |
1206 | @code{start} of this window should not be changed, even if point | |
1207 | gets invisible. | |
1208 | ||
1209 | @item start_at_line_beg | |
1210 | Non-@code{nil} means current value of @code{start} was the beginning of a line | |
1211 | when it was chosen. | |
1212 | ||
b8d4c8d0 GM |
1213 | @item use_time |
1214 | This is the last time that the window was selected. The function | |
1215 | @code{get-lru-window} uses this field. | |
1216 | ||
1217 | @item sequence_number | |
1218 | A unique number assigned to this window when it was created. | |
1219 | ||
1220 | @item last_modified | |
1221 | The @code{modiff} field of the window's buffer, as of the last time | |
1222 | a redisplay completed in this window. | |
1223 | ||
1224 | @item last_overlay_modified | |
1225 | The @code{overlay_modiff} field of the window's buffer, as of the last | |
1226 | time a redisplay completed in this window. | |
1227 | ||
1228 | @item last_point | |
1229 | The buffer's value of point, as of the last time a redisplay completed | |
1230 | in this window. | |
1231 | ||
1232 | @item last_had_star | |
1233 | A non-@code{nil} value means the window's buffer was ``modified'' when the | |
1234 | window was last updated. | |
1235 | ||
1236 | @item vertical_scroll_bar | |
1237 | This window's vertical scroll bar. | |
1238 | ||
7d2d7cc0 GM |
1239 | @item left_margin_cols |
1240 | @itemx right_margin_cols | |
ee2d5b5e | 1241 | The widths of the left and right margins in this window. A value of |
7d2d7cc0 GM |
1242 | @code{nil} means no margin. |
1243 | ||
1244 | @item left_fringe_width | |
1245 | @itemx right_fringe_width | |
1246 | The widths of the left and right fringes in this window. A value of | |
1247 | @code{nil} or @code{t} means use the values of the frame. | |
1248 | ||
1249 | @item fringes_outside_margins | |
1250 | A non-@code{nil} value means the fringes outside the display margins; | |
1251 | othersize they are between the margin and the text. | |
b8d4c8d0 GM |
1252 | |
1253 | @item window_end_pos | |
1254 | This is computed as @code{z} minus the buffer position of the last glyph | |
1255 | in the current matrix of the window. The value is only valid if | |
1256 | @code{window_end_valid} is not @code{nil}. | |
1257 | ||
1258 | @item window_end_bytepos | |
1259 | The byte position corresponding to @code{window_end_pos}. | |
1260 | ||
1261 | @item window_end_vpos | |
1262 | The window-relative vertical position of the line containing | |
1263 | @code{window_end_pos}. | |
1264 | ||
1265 | @item window_end_valid | |
1266 | This field is set to a non-@code{nil} value if @code{window_end_pos} is truly | |
7d2d7cc0 | 1267 | valid. This is @code{nil} if nontrivial redisplay is pre-empted, since in that |
b8d4c8d0 GM |
1268 | case the display that @code{window_end_pos} was computed for did not get |
1269 | onto the screen. | |
1270 | ||
b8d4c8d0 GM |
1271 | @item cursor |
1272 | A structure describing where the cursor is in this window. | |
1273 | ||
1274 | @item last_cursor | |
1275 | The value of @code{cursor} as of the last redisplay that finished. | |
1276 | ||
1277 | @item phys_cursor | |
1278 | A structure describing where the cursor of this window physically is. | |
1279 | ||
1280 | @item phys_cursor_type | |
7d2d7cc0 GM |
1281 | @c FIXME What is this? |
1282 | @c itemx phys_cursor_ascent | |
1283 | @itemx phys_cursor_height | |
1284 | @itemx phys_cursor_width | |
1285 | The type, height, and width of the cursor that was last displayed on | |
1286 | this window. | |
b8d4c8d0 GM |
1287 | |
1288 | @item phys_cursor_on_p | |
1289 | This field is non-zero if the cursor is physically on. | |
1290 | ||
1291 | @item cursor_off_p | |
7d2d7cc0 GM |
1292 | Non-zero means the cursor in this window is logically off. This is |
1293 | used for blinking the cursor. | |
b8d4c8d0 GM |
1294 | |
1295 | @item last_cursor_off_p | |
1296 | This field contains the value of @code{cursor_off_p} as of the time of | |
1297 | the last redisplay. | |
1298 | ||
1299 | @item must_be_updated_p | |
1300 | This is set to 1 during redisplay when this window must be updated. | |
1301 | ||
1302 | @item hscroll | |
1303 | This is the number of columns that the display in the window is scrolled | |
1304 | horizontally to the left. Normally, this is 0. | |
1305 | ||
1306 | @item vscroll | |
1307 | Vertical scroll amount, in pixels. Normally, this is 0. | |
1308 | ||
1309 | @item dedicated | |
1310 | Non-@code{nil} if this window is dedicated to its buffer. | |
1311 | ||
1312 | @item display_table | |
1313 | The window's display table, or @code{nil} if none is specified for it. | |
1314 | ||
1315 | @item update_mode_line | |
1316 | Non-@code{nil} means this window's mode line needs to be updated. | |
1317 | ||
1318 | @item base_line_number | |
1319 | The line number of a certain position in the buffer, or @code{nil}. | |
1320 | This is used for displaying the line number of point in the mode line. | |
1321 | ||
1322 | @item base_line_pos | |
1323 | The position in the buffer for which the line number is known, or | |
7d2d7cc0 GM |
1324 | @code{nil} meaning none is known. If it is a buffer, don't display |
1325 | the line number as long as the window shows that buffer. | |
b8d4c8d0 GM |
1326 | |
1327 | @item region_showing | |
1328 | If the region (or part of it) is highlighted in this window, this field | |
1329 | holds the mark position that made one end of that region. Otherwise, | |
1330 | this field is @code{nil}. | |
1331 | ||
1332 | @item column_number_displayed | |
1333 | The column number currently displayed in this window's mode line, or @code{nil} | |
1334 | if column numbers are not being displayed. | |
1335 | ||
1336 | @item current_matrix | |
7d2d7cc0 GM |
1337 | @itemx desired_matrix |
1338 | Glyph matrices describing the current and desired display of this window. | |
b8d4c8d0 GM |
1339 | @end table |
1340 | ||
1341 | @node Process Internals | |
520f2425 | 1342 | @subsection Process Internals |
b8d4c8d0 GM |
1343 | @cindex internals, of process |
1344 | @cindex process internals | |
1345 | ||
7d2d7cc0 GM |
1346 | The fields of a process (for a complete list, see the definition of |
1347 | @code{struct Lisp_Process} in @file{process.h}) include: | |
b8d4c8d0 GM |
1348 | |
1349 | @table @code | |
1350 | @item name | |
1351 | A string, the name of the process. | |
1352 | ||
1353 | @item command | |
1354 | A list containing the command arguments that were used to start this | |
c73e02fa GM |
1355 | process. For a network or serial process, it is @code{nil} if the |
1356 | process is running or @code{t} if the process is stopped. | |
b8d4c8d0 GM |
1357 | |
1358 | @item filter | |
7d2d7cc0 GM |
1359 | If non-@code{nil}, a function used to accept output from the process |
1360 | instead of a buffer. | |
b8d4c8d0 GM |
1361 | |
1362 | @item sentinel | |
7d2d7cc0 GM |
1363 | If non-@code{nil}, a function called whenever the state of the process |
1364 | changes. | |
b8d4c8d0 GM |
1365 | |
1366 | @item buffer | |
1367 | The associated buffer of the process. | |
1368 | ||
1369 | @item pid | |
1370 | An integer, the operating system's process @acronym{ID}. | |
7d2d7cc0 | 1371 | Pseudo-processes such as network or serial connections use a value of 0. |
b8d4c8d0 GM |
1372 | |
1373 | @item childp | |
7d2d7cc0 GM |
1374 | A flag, @code{t} if this is really a child process. For a network or |
1375 | serial connection, it is a plist based on the arguments to | |
1376 | @code{make-network-process} or @code{make-serial-process}. | |
b8d4c8d0 GM |
1377 | |
1378 | @item mark | |
1379 | A marker indicating the position of the end of the last output from this | |
1380 | process inserted into the buffer. This is often but not always the end | |
1381 | of the buffer. | |
1382 | ||
1383 | @item kill_without_query | |
ee2d5b5e CY |
1384 | If this is non-zero, killing Emacs while this process is still running |
1385 | does not ask for confirmation about killing the process. | |
b8d4c8d0 | 1386 | |
7d2d7cc0 GM |
1387 | @item raw_status |
1388 | The raw process status, as returned by the @code{wait} system call. | |
b8d4c8d0 GM |
1389 | |
1390 | @item status | |
1391 | The process status, as @code{process-status} should return it. | |
1392 | ||
1393 | @item tick | |
1394 | @itemx update_tick | |
1395 | If these two fields are not equal, a change in the status of the process | |
1396 | needs to be reported, either by running the sentinel or by inserting a | |
1397 | message in the process buffer. | |
1398 | ||
1399 | @item pty_flag | |
1400 | Non-@code{nil} if communication with the subprocess uses a @acronym{PTY}; | |
1401 | @code{nil} if it uses a pipe. | |
1402 | ||
1403 | @item infd | |
1404 | The file descriptor for input from the process. | |
1405 | ||
1406 | @item outfd | |
1407 | The file descriptor for output to the process. | |
1408 | ||
b8d4c8d0 GM |
1409 | @item tty_name |
1410 | The name of the terminal that the subprocess is using, | |
1411 | or @code{nil} if it is using pipes. | |
1412 | ||
1413 | @item decode_coding_system | |
1414 | Coding-system for decoding the input from this process. | |
1415 | ||
1416 | @item decoding_buf | |
1417 | A working buffer for decoding. | |
1418 | ||
1419 | @item decoding_carryover | |
1420 | Size of carryover in decoding. | |
1421 | ||
1422 | @item encode_coding_system | |
1423 | Coding-system for encoding the output to this process. | |
1424 | ||
1425 | @item encoding_buf | |
1426 | A working buffer for encoding. | |
1427 | ||
b8d4c8d0 GM |
1428 | @item inherit_coding_system_flag |
1429 | Flag to set @code{coding-system} of the process buffer from the | |
1430 | coding system used to decode process output. | |
c73e02fa GM |
1431 | |
1432 | @item type | |
1433 | Symbol indicating the type of process: @code{real}, @code{network}, | |
7d2d7cc0 | 1434 | @code{serial}. |
c73e02fa | 1435 | |
b8d4c8d0 | 1436 | @end table |
7d2d7cc0 GM |
1437 | |
1438 | @c FIXME Mention src/globals.h somewhere in this file? |