@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1998, 1999, 2002, 2003, 2004,
+@c 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/internals
@node GNU Emacs Internals, Standard Errors, Tips, Top
internal aspects of GNU Emacs that may be of interest to C programmers.
@menu
-* Building Emacs:: How to preload Lisp libraries into Emacs.
+* Building Emacs:: How the dumped Emacs is made.
* Pure Storage:: A kludge to make preloaded Lisp functions sharable.
* Garbage Collection:: Reclaiming space for Lisp objects no longer used.
+* Memory Usage:: Info about total size of Lisp objects made so far.
* Writing Emacs Primitives:: Writing C code for Emacs.
* Object Internals:: Data formats of buffers, windows, processes.
@end menu
-@node Building Emacs, Pure Storage, GNU Emacs Internals, GNU Emacs Internals
+@node Building Emacs
@appendixsec Building Emacs
@cindex building Emacs
@pindex temacs
extra time is not too severe a problem.
@cindex @file{site-load.el}
+
You can specify additional files to preload by writing a library named
-@file{site-load.el} that loads them. You may need to increase the value
-of @code{PURESIZE}, in @file{src/puresize.h}, to make room for the
-additional data. (Try adding increments of 20000 until it is big
-enough.) However, the advantage of preloading additional files
-decreases as machines get faster. On modern machines, it is usually not
-advisable.
+@file{site-load.el} that loads them. You may need to add a definition
+
+@example
+#define SITELOAD_PURESIZE_EXTRA @var{n}
+@end example
+
+@noindent
+to make @var{n} added bytes of pure space to hold the additional files.
+(Try adding increments of 20000 until it is big enough.) However, the
+advantage of preloading additional files decreases as machines get
+faster. On modern machines, it is usually not advisable.
After @file{loadup.el} reads @file{site-load.el}, it finds the
documentation strings for primitive and preloaded functions (and
-variables) in the file @file{etc/DOC} where they are stored, by calling
-@code{Snarf-documentation} (@pxref{Accessing Documentation}).
+variables) in the file @file{etc/DOC} where they are stored, by
+calling @code{Snarf-documentation} (@pxref{Definition of
+Snarf-documentation,, Accessing Documentation}).
@cindex @file{site-init.el}
You can specify other Lisp expressions to execute just before dumping
@item
Specify a non-@code{nil} value for
-@code{byte-compile-dynamic-docstrings} as a local variable in each these
+@code{byte-compile-dynamic-docstrings} as a local variable in each of these
files, and load them with either @file{site-load.el} or
@file{site-init.el}. (This method has the drawback that the
documentation strings take up space in Emacs all the time.)
@file{site-init.el} that would alter any of the features that users
expect in an ordinary unmodified Emacs. If you feel you must override
normal features for your site, do it with @file{default.el}, so that
-users can override your changes if they wish. @xref{Start-up Summary}.
+users can override your changes if they wish. @xref{Startup Summary}.
+
+ In a package that can be preloaded, it is sometimes useful to
+specify a computation to be done when Emacs subsequently starts up.
+For this, use @code{eval-at-startup}:
+
+@defmac eval-at-startup body@dots{}
+This evaluates the @var{body} forms, either immediately if running in
+an Emacs that has already started up, or later when Emacs does start
+up. Since the value of the @var{body} forms is not necessarily
+available when the @code{eval-at-startup} form is run, that form
+always returns @code{nil}.
+@end defmac
@defun dump-emacs to-file from-file
@cindex unexec
- This function dumps the current state of Emacs into an executable file
+This function dumps the current state of Emacs into an executable file
@var{to-file}. It takes symbols from @var{from-file} (this is normally
the executable file @file{temacs}).
-If you use this function in an Emacs that was already dumped, you must
-set @code{command-line-processed} to @code{nil} first for good results.
-@xref{Command Line Arguments}.
+If you want to use this function in an Emacs that was already dumped,
+you must run Emacs with @samp{-batch}.
@end defun
-@deffn Command emacs-version
- This function returns a string describing the version of Emacs that is
-running. It is useful to include this string in bug reports.
-
-@example
-@group
-(emacs-version)
- @result{} "GNU Emacs 19.29.1 (i386-debian-linux) \
- of Tue Jun 6 1995 on balloon"
-@end group
-@end example
-
-Called interactively, the function prints the same information in the
-echo area.
-@end deffn
-
-@defvar emacs-build-time
-The value of this variable is the time at which Emacs was built at the
-local site.
-
-@example
-@group
-emacs-build-time
- @result{} "Tue Jun 6 14:55:57 1995"
-@end group
-@end example
-@end defvar
-
-@defvar emacs-version
-The value of this variable is the version of Emacs being run. It is a
-string such as @code{"19.29.1"}.
-@end defvar
-
- The following two variables did not exist before Emacs version 19.23,
-which reduces their usefulness at present, but we hope they will be
-convenient in the future.
-
-@defvar emacs-major-version
-The major version number of Emacs, as an integer. For Emacs version
-19.29, the value is 19.
-@end defvar
-
-@defvar emacs-minor-version
-The minor version number of Emacs, as an integer. For Emacs version
-19.29, the value is 29.
-@end defvar
-
-@node Pure Storage, Garbage Collection, Building Emacs, GNU Emacs Internals
+@node Pure Storage
@appendixsec Pure Storage
@cindex pure storage
Emacs Lisp uses two kinds of storage for user-created Lisp objects:
@dfn{normal storage} and @dfn{pure storage}. Normal storage is where
-all the new data created during an Emacs session is kept; see the
+all the new data created during an Emacs session are kept; see the
following section for information on normal storage. Pure storage is
used for certain data in the preloaded standard Lisp files---data that
should never change during actual use of Emacs.
preload additional libraries or add features to the standard ones.
@defun purecopy object
-This function makes a copy of @var{object} in pure storage and returns
-it. It copies strings by simply making a new string with the same
-characters in pure storage. It recursively copies the contents of
-vectors and cons cells. It does not make copies of other objects such
-as symbols, but just returns them unchanged. It signals an error if
-asked to copy markers.
+This function makes a copy in pure storage of @var{object}, and returns
+it. It copies a string by simply making a new string with the same
+characters, but without text properties, in pure storage. It
+recursively copies the contents of vectors and cons cells. It does
+not make copies of other objects such as symbols, but just returns
+them unchanged. It signals an error if asked to copy markers.
This function is a no-op except while Emacs is being built and dumped;
it is usually called only in the file @file{emacs/lisp/loaddefs.el}, but
You should not change this flag in a running Emacs.
@end defvar
-@node Garbage Collection, Writing Emacs Primitives, Pure Storage, GNU Emacs Internals
+@node Garbage Collection
@appendixsec Garbage Collection
@cindex garbage collector
might as well be reused, since no one will miss them. The second
(``sweep'') phase of the garbage collector arranges to reuse them.
+@c ??? Maybe add something describing weak hash tables here?
+
@cindex free list
The sweep phase puts unused cons cells onto a @dfn{free list}
for future allocation; likewise for symbols and markers. It compacts
((@var{used-conses} . @var{free-conses})
(@var{used-syms} . @var{free-syms})
@end group
- (@var{used-markers} . @var{free-markers})
- @var{used-string-chars}
+ (@var{used-miscs} . @var{free-miscs})
+ @var{used-string-chars}
@var{used-vector-slots}
- (@var{used-floats} . @var{free-floats}))
+ (@var{used-floats} . @var{free-floats})
+ (@var{used-intervals} . @var{free-intervals})
+ (@var{used-strings} . @var{free-strings}))
+@end example
+Here is an example:
+
+@example
@group
(garbage-collect)
- @result{} ((3435 . 2332) (1688 . 0)
- (57 . 417) 24510 3839 (4 . 1))
+ @result{} ((106886 . 13184) (9769 . 0)
+ (7731 . 4651) 347543 121628
+ (31 . 94) (1273 . 168)
+ (25474 . 3569))
@end group
@end example
The number of symbols for which space has been obtained from the
operating system, but that are not currently being used.
-@item used-markers
-The number of markers in use.
+@item used-miscs
+The number of miscellaneous objects in use. These include markers and
+overlays, plus certain objects not visible to users.
-@item free-markers
-The number of markers for which space has been obtained from the
-operating system, but that are not currently being used.
+@item free-miscs
+The number of miscellaneous objects for which space has been obtained
+from the operating system, but that are not currently being used.
@item used-string-chars
The total size of all strings, in characters.
@c Emacs 19 feature
The number of floats for which space has been obtained from the
operating system, but that are not currently being used.
+
+@item used-intervals
+The number of intervals in use. Intervals are an internal
+data structure used for representing text properties.
+
+@item free-intervals
+The number of intervals for which space has been obtained
+from the operating system, but that are not currently being used.
+
+@item used-strings
+The number of strings in use.
+
+@item free-strings
+The number of string headers for which the space was obtained from the
+operating system, but which are currently not in use. (A string
+object consists of a header and the storage for the string text
+itself; the latter is only allocated when the string is created.)
@end table
@end deffn
+@defopt garbage-collection-messages
+If this variable is non-@code{nil}, Emacs displays a message at the
+beginning and end of garbage collection. The default value is
+@code{nil}, meaning there are no such messages.
+@end defopt
+
+@defvar post-gc-hook
+This is a normal hook that is run at the end of garbage collection.
+Garbage collection is inhibited while the hook functions run, so be
+careful writing them.
+@end defvar
+
@defopt gc-cons-threshold
The value of this variable is the number of bytes of storage that must
be allocated for Lisp objects after one garbage collection in order to
the threshold is exhausted, but only the next time the Lisp evaluator is
called.
-The initial threshold value is 300,000. If you specify a larger
+The initial threshold value is 400,000. If you specify a larger
value, garbage collection will happen less often. This reduces the
amount of time spent garbage collecting, but increases total memory use.
You may want to do this when running a program that creates lots of
@code{garbage-collect} will set the threshold back to 10,000.
@end defopt
+@defopt gc-cons-percentage
+The value of this variable specifies the amount of consing before a
+garbage collection occurs, as a fraction of the current heap size.
+This criterion and @code{gc-cons-threshold} apply in parallel, and
+garbage collection occurs only when both criteria are satisfied.
+
+As the heap size increases, the time to perform a garbage collection
+increases. Thus, it can be desirable to do them less frequently in
+proportion.
+@end defopt
+
+ The value returned by @code{garbage-collect} describes the amount of
+memory used by Lisp data, broken down by data type. By contrast, the
+function @code{memory-limit} provides information on the total amount of
+memory Emacs is currently using.
+
@c Emacs 19 feature
@defun memory-limit
This function returns the address of the last byte Emacs has allocated,
memory usage.
@end defun
-@node Writing Emacs Primitives, Object Internals, Garbage Collection, GNU Emacs Internals
+@defvar memory-full
+This variable is @code{t} if Emacs is close to out of memory for Lisp
+objects, and @code{nil} otherwise.
+@end defvar
+
+@defun memory-use-counts
+This returns a list of numbers that count the number of objects
+created in this Emacs session. Each of these counters increments for
+a certain kind of object. See the documentation string for details.
+@end defun
+
+@defvar gcs-done
+This variable contains the total number of garbage collections
+done so far in this Emacs session.
+@end defvar
+
+@defvar gc-elapsed
+This variable contains the total number of seconds of elapsed time
+during garbage collection so far in this Emacs session, as a floating
+point number.
+@end defvar
+
+@node Memory Usage
+@section Memory Usage
+
+ These functions and variables give information about the total amount
+of memory allocation that Emacs has done, broken down by data type.
+Note the difference between these and the values returned by
+@code{(garbage-collect)}; those count objects that currently exist, but
+these count the number or size of all allocations, including those for
+objects that have since been freed.
+
+@defvar cons-cells-consed
+The total number of cons cells that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar floats-consed
+The total number of floats that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar vector-cells-consed
+The total number of vector cells that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar symbols-consed
+The total number of symbols that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar string-chars-consed
+The total number of string characters that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar misc-objects-consed
+The total number of miscellaneous objects that have been allocated so
+far in this Emacs session. These include markers and overlays, plus
+certain objects not visible to users.
+@end defvar
+
+@defvar intervals-consed
+The total number of intervals that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar strings-consed
+The total number of strings that have been allocated so far in this
+Emacs session.
+@end defvar
+
+@node Writing Emacs Primitives
@appendixsec Writing Emacs Primitives
@cindex primitive function internals
@smallexample
@group
DEFUN ("or", For, Sor, 0, UNEVALLED, 0,
- "Eval args until one of them yields non-nil, then return that value.\n\
-The remaining args are not evalled at all.\n\
+ doc: /* Eval args until one of them yields non-nil, then return that value.
+The remaining args are not evalled at all.
+If all args return nil, return nil.
@end group
@group
-If all args return nil, return nil.")
+usage: (or CONDITIONS ...) */)
(args)
Lisp_Object args;
@{
- register Lisp_Object val;
- Lisp_Object args_left;
+ register Lisp_Object val = Qnil;
struct gcpro gcpro1;
@end group
@group
- if (NULL (args))
- return Qnil;
-
- args_left = args;
- GCPRO1 (args_left);
+ GCPRO1 (args);
@end group
@group
- do
+ while (CONSP (args))
@{
- val = Feval (Fcar (args_left));
- if (!NULL (val))
- break;
- args_left = Fcdr (args_left);
+ val = Feval (XCAR (args));
+ if (!NILP (val))
+ break;
+ args = XCDR (args);
@}
- while (!NULL (args_left));
@end group
@group
@code{MANY}, indicating an unlimited number of evaluated arguments (the
equivalent of @code{&rest}). Both @code{UNEVALLED} and @code{MANY} are
macros. If @var{max} is a number, it may not be less than @var{min} and
-it may not be greater than seven.
+it may not be greater than eight.
@item interactive
This is an interactive specification, a string such as might be used as
should receive no arguments when called interactively.
@item doc
-This is the documentation string. It is written just like a
-documentation string for a function defined in Lisp, except you must
-write @samp{\n\} at the end of each line. In particular, the first line
-should be a single sentence.
+This is the documentation string. It uses C comment syntax rather
+than C string syntax because comment syntax requires nothing special
+to include multiple lines. The @samp{doc:} identifies the comment
+that follows as the documentation string. The @samp{/*} and @samp{*/}
+delimiters that begin and end the comment are not part of the
+documentation string.
+
+If the last line of the documentation string begins with the keyword
+@samp{usage:}, the rest of the line is treated as the argument list
+for documentation purposes. This way, you can use different argument
+names in the documentation string from the ones used in the C code.
+@samp{usage:} is required if the function has an unlimited number of
+arguments.
+
+All the usual rules for documentation strings in Lisp code
+(@pxref{Documentation Tips}) apply to C code documentation strings
+too.
@end table
After the call to the @code{DEFUN} macro, you must write the argument
@code{UNGCPRO} cancels the protection of the variables that are
protected in the current function. It is necessary to do this explicitly.
- For most data types, it suffices to protect at least one pointer to
-the object; as long as the object is not recycled, all pointers to it
-remain valid. This is not so for strings, because the garbage collector
-can move them. When the garbage collector moves a string, it relocates
-all the pointers it knows about; any other pointers become invalid.
-Therefore, you must protect all pointers to strings across any point
-where garbage collection may be possible.
-
- The macro @code{GCPRO1} protects just one local variable. If you want
-to protect two, use @code{GCPRO2} instead; repeating @code{GCPRO1} will
-not work. Macros @code{GCPRO3} and @code{GCPRO4} also exist.
-
- These macros implicitly use local variables such as @code{gcpro1}; you
-must declare these explicitly, with type @code{struct gcpro}. Thus, if
-you use @code{GCPRO2}, you must declare @code{gcpro1} and @code{gcpro2}.
+ It suffices to ensure that at least one pointer to each object is
+GC-protected; as long as the object is not recycled, all pointers to
+it remain valid. So if you are sure that a local variable points to
+an object that will be preserved by some other pointer, that local
+variable does not need a @code{GCPRO}. (Formerly, strings were an
+exception to this rule; in older Emacs versions, every pointer to a
+string needed to be marked by GC.)
+
+ The macro @code{GCPRO1} protects just one local variable. If you
+want to protect two, use @code{GCPRO2} instead; repeating
+@code{GCPRO1} will not work. Macros, @code{GCPRO3}, @code{GCPRO4},
+@code{GCPRO5}, and @code{GCPRO6} also exist. These macros implicitly
+use local variables such as @code{gcpro1}; you must declare these
+explicitly, with type @code{struct gcpro}. Thus, if you use
+@code{GCPRO2}, you must declare @code{gcpro1} and @code{gcpro2}.
Alas, we can't explain all the tricky details here.
+ Built-in functions that take a variable number of arguments actually
+accept two arguments at the C level: the number of Lisp arguments, and
+a @code{Lisp_Object *} pointer to a C vector containing those Lisp
+arguments. This C vector may be part of a Lisp vector, but it need
+not be. The responsibility for using @code{GCPRO} to protect the Lisp
+arguments from GC if necessary rests with the caller in this case,
+since the caller allocated or found the storage for them.
+
You must not use C initializers for static or global variables unless
-they are never written once Emacs is dumped. These variables with
-initializers are allocated in an area of memory that becomes read-only
-(on certain operating systems) as a result of dumping Emacs. @xref{Pure
-Storage}.
+the variables are never written once Emacs is dumped. These variables
+with initializers are allocated in an area of memory that becomes
+read-only (on certain operating systems) as a result of dumping Emacs.
+@xref{Pure Storage}.
Do not use static variables within functions---place all static
variables at top level in the file. This is necessary because Emacs on
of these functions are called, and add a call to
@code{syms_of_@var{filename}} there.
+@anchor{Defining Lisp variables in C}
+@vindex byte-boolean-vars
The function @code{syms_of_@var{filename}} is also the place to define
any C variables that are to be visible as Lisp variables.
@code{DEFVAR_LISP} makes a C variable of type @code{Lisp_Object} visible
in Lisp. @code{DEFVAR_INT} makes a C variable of type @code{int}
visible in Lisp with a value that is always an integer.
@code{DEFVAR_BOOL} makes a C variable of type @code{int} visible in Lisp
-with a value that is either @code{t} or @code{nil}.
+with a value that is either @code{t} or @code{nil}. Note that variables
+defined with @code{DEFVAR_BOOL} are automatically added to the list
+@code{byte-boolean-vars} used by the byte compiler.
+
+ If you define a file-scope C variable of type @code{Lisp_Object},
+you must protect it from garbage-collection by calling @code{staticpro}
+in @code{syms_of_@var{filename}}, like this:
+
+@example
+staticpro (&@var{variable});
+@end example
Here is another example function, with more complicated arguments.
-This comes from the code for the X Window System, and it demonstrates
-the use of macros and functions to manipulate Lisp objects.
+This comes from the code in @file{window.c}, and it demonstrates the use
+of macros and functions to manipulate Lisp objects.
@smallexample
@group
DEFUN ("coordinates-in-window-p", Fcoordinates_in_window_p,
Scoordinates_in_window_p, 2, 2,
"xSpecify coordinate pair: \nXExpression which evals to window: ",
- "Return non-nil if POSITIONS is in WINDOW.\n\
- \(POSITIONS is a list, (SCREEN-X SCREEN-Y)\)\n\
+ "Return non-nil if COORDINATES is in WINDOW.\n\
+COORDINATES is a cons of the form (X . Y), X and Y being distances\n\
+...
@end group
@group
- Returned value is list of positions expressed\n\
- relative to window upper left corner.")
- (coordinate, window)
- register Lisp_Object coordinate, window;
+If they are on the border between WINDOW and its right sibling,\n\
+ `vertical-line' is returned.")
+ (coordinates, window)
+ register Lisp_Object coordinates, window;
@{
- register Lisp_Object xcoord, ycoord;
+ int x, y;
@end group
@group
- if (!CONSP (coordinate)) wrong_type_argument (Qlistp, coordinate);
- CHECK_WINDOW (window, 2);
- xcoord = Fcar (coordinate);
- ycoord = Fcar (Fcdr (coordinate));
- CHECK_NUMBER (xcoord, 0);
- CHECK_NUMBER (ycoord, 1);
+ CHECK_LIVE_WINDOW (window, 0);
+ CHECK_CONS (coordinates, 1);
+ x = XINT (Fcar (coordinates));
+ y = XINT (Fcdr (coordinates));
@end group
+
@group
- if ((XINT (xcoord) < XINT (XWINDOW (window)->left))
- || (XINT (xcoord) >= (XINT (XWINDOW (window)->left)
- + XINT (XWINDOW (window)->width))))
- return Qnil;
- XFASTINT (xcoord) -= XFASTINT (XWINDOW (window)->left);
+ switch (coordinates_in_window (XWINDOW (window), &x, &y))
+ @{
+ case 0: /* NOT in window at all. */
+ return Qnil;
@end group
+
@group
- if (XINT (ycoord) == (screen_height - 1))
- return Qnil;
+ case 1: /* In text part of window. */
+ return Fcons (make_number (x), make_number (y));
@end group
+
@group
- if ((XINT (ycoord) < XINT (XWINDOW (window)->top))
- || (XINT (ycoord) >= (XINT (XWINDOW (window)->top)
- + XINT (XWINDOW (window)->height)) - 1))
- return Qnil;
+ case 2: /* In mode line of window. */
+ return Qmode_line;
@end group
+
@group
- XFASTINT (ycoord) -= XFASTINT (XWINDOW (window)->top);
- return (Fcons (xcoord, Fcons (ycoord, Qnil)));
+ case 3: /* On right border of window. */
+ return Qvertical_line;
+@end group
+
+@group
+ default:
+ abort ();
+ @}
@}
@end group
@end smallexample
@file{lisp.h} contains the definitions for some important macros and
functions.
-@node Object Internals, , Writing Emacs Primitives, GNU Emacs Internals
+ If you define a function which is side-effect free, update the code
+in @file{byte-opt.el} which binds @code{side-effect-free-fns} and
+@code{side-effect-and-error-free-fns} so that the compiler optimizer
+knows about it.
+
+@node Object Internals
@appendixsec Object Internals
@cindex object internals
GNU Emacs Lisp manipulates many different types of data. The actual
-data are stored in a heap and the only access that programs have to it is
-through pointers. Pointers are thirty-two bits wide in most
+data are stored in a heap and the only access that programs have to it
+is through pointers. Pointers are thirty-two bits wide in most
implementations. Depending on the operating system and type of machine
-for which you compile Emacs, twenty-four to twenty-six bits are used to
-address the object, and the remaining six to eight bits are used for a
-tag that identifies the object's type.
+for which you compile Emacs, twenty-nine bits are used to address the
+object, and the remaining three bits are used for the tag that
+identifies the object's type.
Because Lisp objects are represented as tagged pointers, it is always
possible to determine the Lisp data type of any object. The C data type
* Process Internals:: Components of a process structure.
@end menu
-@node Buffer Internals, Window Internals, Object Internals, Object Internals
+@node Buffer Internals
@appendixsubsec Buffer Internals
@cindex internals, of buffer
@cindex buffer internals
We describe them here, naming them by the names used in the C code.
Many are accessible indirectly in Lisp programs via Lisp primitives.
+Two structures are used to represent buffers in C. The
+@code{buffer_text} structure contains fields describing the text of a
+buffer; the @code{buffer} structure holds other fields. In the case
+of indirect buffers, two or more @code{buffer} structures reference
+the same @code{buffer_text} structure.
+
+Here is a list of the @code{struct buffer_text} fields:
+
@table @code
-@item name
-The buffer name is a string that names the buffer. It is guaranteed to
-be unique. @xref{Buffer Names}.
+@item beg
+This field contains the actual address of the buffer contents.
-@item save_modified
-This field contains the time when the buffer was last saved, as an integer.
-@xref{Buffer Modification}.
+@item gpt
+This holds the character position of the gap in the buffer.
+@xref{Buffer Gap}.
+
+@item z
+This field contains the character position of the end of the buffer
+text.
+
+@item gpt_byte
+Contains the byte position of the gap.
+
+@item z_byte
+Holds the byte position of the end of the buffer text.
+
+@item gap_size
+Contains the size of buffer's gap. @xref{Buffer Gap}.
+
+@item modiff
+This field counts buffer-modification events for this buffer. It is
+incremented for each such event, and never otherwise changed.
+
+@item save_modiff
+Contains the previous value of @code{modiff}, as of the last time a
+buffer was visited or saved in a file.
+
+@item overlay_modiff
+Counts modifications to overlays analogous to @code{modiff}.
+
+@item beg_unchanged
+Holds the number of characters at the start of the text that are known
+to be unchanged since the last redisplay that finished.
+
+@item end_unchanged
+Holds the number of characters at the end of the text that are known to
+be unchanged since the last redisplay that finished.
+
+@item unchanged_modified
+Contains the value of @code{modiff} at the time of the last redisplay
+that finished. If this value matches @code{modiff},
+@code{beg_unchanged} and @code{end_unchanged} contain no useful
+information.
+
+@item overlay_unchanged_modified
+Contains the value of @code{overlay_modiff} at the time of the last
+redisplay that finished. If this value matches @code{overlay_modiff},
+@code{beg_unchanged} and @code{end_unchanged} contain no useful
+information.
+
+@item markers
+The markers that refer to this buffer. This is actually a single
+marker, and successive elements in its marker @code{chain} are the other
+markers referring to this buffer text.
+
+@item intervals
+Contains the interval tree which records the text properties of this
+buffer.
+@end table
+
+The fields of @code{struct buffer} are:
+
+@table @code
+@item next
+Points to the next buffer, in the chain of all buffers including killed
+buffers. This chain is used only for garbage collection, in order to
+collect killed buffers properly. Note that vectors, and most kinds of
+objects allocated as vectors, are all on one chain, but buffers are on a
+separate chain of their own.
+
+@item own_text
+This is a @code{struct buffer_text} structure. In an ordinary buffer,
+it holds the buffer contents. In indirect buffers, this field is not
+used.
+
+@item text
+This points to the @code{buffer_text} structure that is used for this
+buffer. In an ordinary buffer, this is the @code{own_text} field above.
+In an indirect buffer, this is the @code{own_text} field of the base
+buffer.
+
+@item pt
+Contains the character position of point in a buffer.
+
+@item pt_byte
+Contains the byte position of point in a buffer.
+
+@item begv
+This field contains the character position of the beginning of the
+accessible range of text in the buffer.
+
+@item begv_byte
+This field contains the byte position of the beginning of the
+accessible range of text in the buffer.
+
+@item zv
+This field contains the character position of the end of the
+accessible range of text in the buffer.
+
+@item zv_byte
+This field contains the byte position of the end of the
+accessible range of text in the buffer.
+
+@item base_buffer
+In an indirect buffer, this points to the base buffer. In an ordinary
+buffer, it is null.
+
+@item local_var_flags
+This field contains flags indicating that certain variables are local in
+this buffer. Such variables are declared in the C code using
+@code{DEFVAR_PER_BUFFER}, and their buffer-local bindings are stored in
+fields in the buffer structure itself. (Some of these fields are
+described in this table.)
@item modtime
This field contains the modification time of the visited file. It is
-set when the file is written or read. Every time the buffer is written
-to the file, this field is compared to the modification time of the
-file. @xref{Buffer Modification}.
+set when the file is written or read. Before writing the buffer into a
+file, this field is compared to the modification time of the file to see
+if the file has changed on disk. @xref{Buffer Modification}.
@item auto_save_modified
This field contains the time when the buffer was last auto-saved.
+@item auto_save_failure_time
+The time at which we detected a failure to auto-save, or -1 if we didn't
+have a failure.
+
@item last_window_start
This field contains the @code{window-start} position in the buffer as of
the last time the buffer was displayed in a window.
+@item clip_changed
+This flag is set when narrowing changes in a buffer.
+
+@item prevent_redisplay_optimizations_p
+this flag indicates that redisplay optimizations should not be used
+to display this buffer.
+
@item undo_list
This field points to the buffer's undo list. @xref{Undo}.
-@item syntax_table_v
+@item name
+The buffer name is a string that names the buffer. It is guaranteed to
+be unique. @xref{Buffer Names}.
+
+@item filename
+The name of the file visited in this buffer, or @code{nil}.
+
+@item directory
+The directory for expanding relative file names.
+
+@item save_length
+Length of the file this buffer is visiting, when last read or saved.
+This and other fields concerned with saving are not kept in the
+@code{buffer_text} structure because indirect buffers are never saved.
+
+@item auto_save_file_name
+File name used for auto-saving this buffer. This is not in the
+@code{buffer_text} because it's not used in indirect buffers at all.
+
+@item read_only
+Non-@code{nil} means this buffer is read-only.
+
+@item mark
+This field contains the mark for the buffer. The mark is a marker,
+hence it is also included on the list @code{markers}. @xref{The Mark}.
+
+@item local_var_alist
+This field contains the association list describing the buffer-local
+variable bindings of this buffer, not including the built-in
+buffer-local bindings that have special slots in the buffer object.
+(Those slots are omitted from this table.) @xref{Buffer-Local
+Variables}.
+
+@item major_mode
+Symbol naming the major mode of this buffer, e.g., @code{lisp-mode}.
+
+@item mode_name
+Pretty name of major mode, e.g., @code{"Lisp"}.
+
+@item mode_line_format
+Mode line element that controls the format of the mode line. If this
+is @code{nil}, no mode line will be displayed.
+
+@item header_line_format
+This field is analoguous to @code{mode_line_format} for the mode
+line displayed at the top of windows.
+
+@item keymap
+This field holds the buffer's local keymap. @xref{Keymaps}.
+
+@item abbrev_table
+This buffer's local abbrevs.
+
+@item syntax_table
This field contains the syntax table for the buffer. @xref{Syntax Tables}.
+@item category_table
+This field contains the category table for the buffer.
+
+@item case_fold_search
+The value of @code{case-fold-search} in this buffer.
+
+@item tab_width
+The value of @code{tab-width} in this buffer.
+
+@item fill_column
+The value of @code{fill-column} in this buffer.
+
+@item left_margin
+The value of @code{left-margin} in this buffer.
+
+@item auto_fill_function
+The value of @code{auto-fill-function} in this buffer.
+
@item downcase_table
This field contains the conversion table for converting text to lower case.
-@xref{Case Table}.
+@xref{Case Tables}.
@item upcase_table
This field contains the conversion table for converting text to upper case.
-@xref{Case Table}.
+@xref{Case Tables}.
@item case_canon_table
This field contains the conversion table for canonicalizing text for
-case-folding search. @xref{Case Table}.
+case-folding search. @xref{Case Tables}.
@item case_eqv_table
This field contains the equivalence table for case-folding search.
-@xref{Case Table}.
+@xref{Case Tables}.
-@item display_table
-This field contains the buffer's display table, or @code{nil} if it doesn't
-have one. @xref{Display Tables}.
+@item truncate_lines
+The value of @code{truncate-lines} in this buffer.
-@item markers
-This field contains the chain of all markers that currently point into
-the buffer. Deletion of text in the buffer, and motion of the buffer's
-gap, must check each of these markers and perhaps update it.
-@xref{Markers}.
+@item ctl_arrow
+The value of @code{ctl-arrow} in this buffer.
-@item backed_up
-This field is a flag that tells whether a backup file has been made
-for the visited file of this buffer.
+@item selective_display
+The value of @code{selective-display} in this buffer.
-@item mark
-This field contains the mark for the buffer. The mark is a marker,
-hence it is also included on the list @code{markers}. @xref{The Mark}.
+@item selective_display_ellipsis
+The value of @code{selective-display-ellipsis} in this buffer.
-@item mark_active
-This field is non-@code{nil} if the buffer's mark is active.
+@item minor_modes
+An alist of the minor modes of this buffer.
-@item local_var_alist
-This field contains the association list describing the variables local
-in this buffer, and their values, with the exception of local variables
-that have special slots in the buffer object. (Those slots are omitted
-from this table.) @xref{Buffer-Local Variables}.
+@item overwrite_mode
+The value of @code{overwrite_mode} in this buffer.
-@item base_buffer
-This field holds the buffer's base buffer (if it is an indirect buffer),
-or @code{nil}.
+@item abbrev_mode
+The value of @code{abbrev-mode} in this buffer.
-@item keymap
-This field holds the buffer's local keymap. @xref{Keymaps}.
+@item display_table
+This field contains the buffer's display table, or @code{nil} if it doesn't
+have one. @xref{Display Tables}.
-@item overlay_center
-This field holds the current overlay center position. @xref{Overlays}.
+@item save_modified
+This field contains the time when the buffer was last saved, as an integer.
+@xref{Buffer Modification}.
+
+@item mark_active
+This field is non-@code{nil} if the buffer's mark is active.
@item overlays_before
This field holds a list of the overlays in this buffer that end at or
This field holds a list of the overlays in this buffer that end after
the current overlay center position. They are sorted in order of
increasing beginning position.
+
+@item overlay_center
+This field holds the current overlay center position. @xref{Overlays}.
+
+@item enable_multibyte_characters
+This field holds the buffer's local value of
+@code{enable-multibyte-characters}---either @code{t} or @code{nil}.
+
+@item buffer_file_coding_system
+The value of @code{buffer-file-coding-system} in this buffer.
+
+@item file_format
+The value of @code{buffer-file-format} in this buffer.
+
+@item auto_save_file_format
+The value of @code{buffer-auto-save-file-format} in this buffer.
+
+@item pt_marker
+In an indirect buffer, or a buffer that is the base of an indirect
+buffer, this holds a marker that records point for this buffer when the
+buffer is not current.
+
+@item begv_marker
+In an indirect buffer, or a buffer that is the base of an indirect
+buffer, this holds a marker that records @code{begv} for this buffer
+when the buffer is not current.
+
+@item zv_marker
+In an indirect buffer, or a buffer that is the base of an indirect
+buffer, this holds a marker that records @code{zv} for this buffer when
+the buffer is not current.
+
+@item file_truename
+The truename of the visited file, or @code{nil}.
+
+@item invisibility_spec
+The value of @code{buffer-invisibility-spec} in this buffer.
+
+@item last_selected_window
+This is the last window that was selected with this buffer in it, or @code{nil}
+if that window no longer displays this buffer.
+
+@item display_count
+This field is incremented each time the buffer is displayed in a window.
+
+@item left_margin_width
+The value of @code{left-margin-width} in this buffer.
+
+@item right_margin_width
+The value of @code{right-margin-width} in this buffer.
+
+@item indicate_empty_lines
+Non-@code{nil} means indicate empty lines (lines with no text) with a
+small bitmap in the fringe, when using a window system that can do it.
+
+@item display_time
+This holds a time stamp that is updated each time this buffer is
+displayed in a window.
+
+@item scroll_up_aggressively
+The value of @code{scroll-up-aggressively} in this buffer.
+
+@item scroll_down_aggressively
+The value of @code{scroll-down-aggressively} in this buffer.
@end table
-@node Window Internals, Process Internals, Buffer Internals, Object Internals
+@node Window Internals
@appendixsubsec Window Internals
@cindex internals, of window
@cindex window internals
@item mini_p
Non-@code{nil} if this window is a minibuffer window.
+@item parent
+Internally, Emacs arranges windows in a tree; each group of siblings has
+a parent window whose area includes all the siblings. This field points
+to a window's parent.
+
+Parent windows do not display buffers, and play little role in display
+except to shape their child windows. Emacs Lisp programs usually have
+no access to the parent windows; they operate on the windows at the
+leaves of the tree, which actually display buffers.
+
+The following four fields also describe the window tree structure.
+
+@item hchild
+In a window subdivided horizontally by child windows, the leftmost child.
+Otherwise, @code{nil}.
+
+@item vchild
+In a window subdivided vertically by child windows, the topmost child.
+Otherwise, @code{nil}.
+
+@item next
+The next sibling of this window. It is @code{nil} in a window that is
+the rightmost or bottommost of a group of siblings.
+
+@item prev
+The previous sibling of this window. It is @code{nil} in a window that
+is the leftmost or topmost of a group of siblings.
+
+@item left
+This is the left-hand edge of the window, measured in columns. (The
+leftmost column on the screen is @w{column 0}.)
+
+@item top
+This is the top edge of the window, measured in lines. (The top line on
+the screen is @w{line 0}.)
+
+@item height
+The height of the window, measured in lines.
+
+@item width
+The width of the window, measured in columns. This width includes the
+scroll bar and fringes, and/or the separator line on the right of the
+window (if any).
+
@item buffer
The buffer that the window is displaying. This may change often during
the life of the window.
-@item dedicated
-Non-@code{nil} if this window is dedicated to its buffer.
+@item start
+The position in the buffer that is the first character to be displayed
+in the window.
@item pointm
@cindex window point internals
This is the value of point in the current buffer when this window is
selected; when it is not selected, it retains its previous value.
-@item start
-The position in the buffer that is the first character to be displayed
-in the window.
-
@item force_start
If this flag is non-@code{nil}, it says that the window has been
scrolled explicitly by the Lisp program. This affects what the next
window to show the text around point, it moves point to a location that
is on the screen.
+@item frozen_window_start_p
+This field is set temporarily to 1 to indicate to redisplay that
+@code{start} of this window should not be changed, even if point
+gets invisible.
+
+@item start_at_line_beg
+Non-@code{nil} means current value of @code{start} was the beginning of a line
+when it was chosen.
+
+@item too_small_ok
+Non-@code{nil} means don't delete this window for becoming ``too small''.
+
+@item height_fixed_p
+This field is temporarily set to 1 to fix the height of the selected
+window when the echo area is resized.
+
+@item use_time
+This is the last time that the window was selected. The function
+@code{get-lru-window} uses this field.
+
+@item sequence_number
+A unique number assigned to this window when it was created.
+
@item last_modified
-The @code{modified} field of the window's buffer, as of the last time
+The @code{modiff} field of the window's buffer, as of the last time
a redisplay completed in this window.
+@item last_overlay_modified
+The @code{overlay_modiff} field of the window's buffer, as of the last
+time a redisplay completed in this window.
+
@item last_point
-The buffer's value of point, as of the last time
-a redisplay completed in this window.
+The buffer's value of point, as of the last time a redisplay completed
+in this window.
-@item left
-This is the left-hand edge of the window, measured in columns. (The
-leftmost column on the screen is @w{column 0}.)
+@item last_had_star
+A non-@code{nil} value means the window's buffer was ``modified'' when the
+window was last updated.
-@item top
-This is the top edge of the window, measured in lines. (The top line on
-the screen is @w{line 0}.)
+@item vertical_scroll_bar
+This window's vertical scroll bar.
-@item height
-The height of the window, measured in lines.
+@item left_margin_width
+The width of the left margin in this window, or @code{nil} not to
+specify it (in which case the buffer's value of @code{left-margin-width}
+is used.
-@item width
-The width of the window, measured in columns.
+@item right_margin_width
+Likewise for the right margin.
-@item next
-This is the window that is the next in the chain of siblings. It is
-@code{nil} in a window that is the rightmost or bottommost of a group of
-siblings.
+@ignore
+@item last_mark_x
+@item last_mark_y
+???Not used.
+@end ignore
-@item prev
-This is the window that is the previous in the chain of siblings. It is
-@code{nil} in a window that is the leftmost or topmost of a group of
-siblings.
+@item window_end_pos
+This is computed as @code{z} minus the buffer position of the last glyph
+in the current matrix of the window. The value is only valid if
+@code{window_end_valid} is not @code{nil}.
-@item parent
-Internally, Emacs arranges windows in a tree; each group of siblings has
-a parent window whose area includes all the siblings. This field points
-to a window's parent.
+@item window_end_bytepos
+The byte position corresponding to @code{window_end_pos}.
-Parent windows do not display buffers, and play little role in display
-except to shape their child windows. Emacs Lisp programs usually have
-no access to the parent windows; they operate on the windows at the
-leaves of the tree, which actually display buffers.
+@item window_end_vpos
+The window-relative vertical position of the line containing
+@code{window_end_pos}.
+
+@item window_end_valid
+This field is set to a non-@code{nil} value if @code{window_end_pos} is truly
+valid. This is @code{nil} if nontrivial redisplay is preempted since in that
+case the display that @code{window_end_pos} was computed for did not get
+onto the screen.
+
+@item redisplay_end_trigger
+If redisplay in this window goes beyond this buffer position, it runs
+the @code{redisplay-end-trigger-hook}.
+
+@ignore
+@item orig_height
+@item orig_top
+??? Are temporary storage areas.
+@end ignore
+
+@item cursor
+A structure describing where the cursor is in this window.
+
+@item last_cursor
+The value of @code{cursor} as of the last redisplay that finished.
+
+@item phys_cursor
+A structure describing where the cursor of this window physically is.
+
+@item phys_cursor_type
+The type of cursor that was last displayed on this window.
+
+@item phys_cursor_on_p
+This field is non-zero if the cursor is physically on.
+
+@item cursor_off_p
+Non-zero means the cursor in this window is logically on.
+
+@item last_cursor_off_p
+This field contains the value of @code{cursor_off_p} as of the time of
+the last redisplay.
+
+@item must_be_updated_p
+This is set to 1 during redisplay when this window must be updated.
@item hscroll
This is the number of columns that the display in the window is scrolled
horizontally to the left. Normally, this is 0.
-@item use_time
-This is the last time that the window was selected. The function
-@code{get-lru-window} uses this field.
+@item vscroll
+Vertical scroll amount, in pixels. Normally, this is 0.
+
+@item dedicated
+Non-@code{nil} if this window is dedicated to its buffer.
@item display_table
The window's display table, or @code{nil} if none is specified for it.
If the region (or part of it) is highlighted in this window, this field
holds the mark position that made one end of that region. Otherwise,
this field is @code{nil}.
+
+@item column_number_displayed
+The column number currently displayed in this window's mode line, or @code{nil}
+if column numbers are not being displayed.
+
+@item current_matrix
+A glyph matrix describing the current display of this window.
+
+@item desired_matrix
+A glyph matrix describing the desired display of this window.
@end table
-@node Process Internals, , Window Internals, Object Internals
+@node Process Internals
@appendixsubsec Process Internals
@cindex internals, of process
@cindex process internals
The associated buffer of the process.
@item pid
-An integer, the Unix process @sc{id}.
+An integer, the operating system's process @acronym{ID}.
@item childp
A flag, non-@code{nil} if this is really a child process.
message in the process buffer.
@item pty_flag
-Non-@code{nil} if communication with the subprocess uses a @sc{pty};
+Non-@code{nil} if communication with the subprocess uses a @acronym{PTY};
@code{nil} if it uses a pipe.
@item infd
@item tty_name
The name of the terminal that the subprocess is using,
or @code{nil} if it is using pipes.
+
+@item decode_coding_system
+Coding-system for decoding the input from this process.
+
+@item decoding_buf
+A working buffer for decoding.
+
+@item decoding_carryover
+Size of carryover in decoding.
+
+@item encode_coding_system
+Coding-system for encoding the output to this process.
+
+@item encoding_buf
+A working buffer for encoding.
+
+@item encoding_carryover
+Size of carryover in encoding.
+
+@item inherit_coding_system_flag
+Flag to set @code{coding-system} of the process buffer from the
+coding system used to decode process output.
@end table
+
+@ignore
+ arch-tag: 4b2c33bc-d7e4-43f5-bc20-27c0db52a53e
+@end ignore