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Diffstat (limited to 'lispref/internals.texi')
| -rw-r--r-- | lispref/internals.texi | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/lispref/internals.texi b/lispref/internals.texi index db7694585aa..7767f0feeb3 100644 --- a/lispref/internals.texi +++ b/lispref/internals.texi @@ -44,6 +44,7 @@ the real runnable Emacs executable. These arguments direct environment, resulting in an Emacs that is still impure but no longer bare. +@cindex dumping Emacs It takes a substantial time to load the standard Lisp files. Luckily, you don't have to do this each time you run Emacs; @file{temacs} can dump out an executable program called @file{emacs} that has these files @@ -86,6 +87,7 @@ calling @code{Snarf-documentation} (@pxref{Definition of Snarf-documentation,, Accessing Documentation}). @cindex @file{site-init.el} +@cindex preloading additional functions and variables You can specify other Lisp expressions to execute just before dumping by putting them in a library named @file{site-init.el}. This file is executed after the documentation strings are found. @@ -491,6 +493,7 @@ Emacs session. @node Writing Emacs Primitives @appendixsec Writing Emacs Primitives @cindex primitive function internals +@cindex writing Emacs primitives Lisp primitives are Lisp functions implemented in C. The details of interfacing the C function so that Lisp can call it are handled by a few @@ -539,6 +542,7 @@ usage: (or CONDITIONS ...) */) @end group @end smallexample +@cindex @code{DEFUN}, C macro to define Lisp primitives Let's start with a precise explanation of the arguments to the @code{DEFUN} macro. Here is a template for them: @@ -619,6 +623,8 @@ receives exactly two arguments: the first is the number of Lisp arguments, and the second is the address of a block containing their values. They have types @code{int} and @w{@code{Lisp_Object *}}. +@cindex @code{GCPRO} and @code{UNGCPRO} +@cindex protect C variables from garbage collection Within the function @code{For} itself, note the use of the macros @code{GCPRO1} and @code{UNGCPRO}. @code{GCPRO1} is used to ``protect'' a variable from garbage collection---to inform the garbage @@ -672,6 +678,7 @@ macro. (This definition is used because those systems put all variables declared static in a place that becomes read-only after dumping, whether they have initializers or not.) +@cindex @code{defsubr}, Lisp symbol for a primitive Defining the C function is not enough to make a Lisp primitive available; you must also create the Lisp symbol for the primitive and store a suitable subr object in its function cell. The code looks like @@ -696,6 +703,8 @@ of these functions are called, and add a call to @anchor{Defining Lisp variables in C} @vindex byte-boolean-vars +@cindex defining Lisp variables in C +@cindex @code{DEFVAR_INT}, @code{DEFVAR_LISP}, @code{DEFVAR_BOOL} 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 @@ -706,6 +715,7 @@ 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. +@cindex @code{staticpro}, protect file-scope variables from GC 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: |