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Re: using empty_string as the only "" string
From: |
Dmitry Antipov |
Subject: |
Re: using empty_string as the only "" string |
Date: |
Sat, 28 Apr 2007 12:54:31 +0400 |
User-agent: |
Thunderbird 1.5.0.7 (X11/20061008) |
Richard Stallman wrote:
Text properties are attached to characters. A null string has no characters
so it cannot have properties.
Ok, so here is a version with two canonical strings allocated from pure space.
Both canonical strings shares XSTRING(s)->data, but it should be valid since
it can't be modified anyway.
Dmitry
Index: alloc.c
===================================================================
RCS file: /sources/emacs/emacs/src/alloc.c,v
retrieving revision 1.409
diff -u -r1.409 alloc.c
--- alloc.c 16 Apr 2007 03:09:33 -0000 1.409
+++ alloc.c 26 Apr 2007 13:22:16 -0000
@@ -1756,6 +1756,8 @@
string_blocks = NULL;
n_string_blocks = 0;
string_free_list = NULL;
+ empty_string = make_pure_string ("", 0, 0, 0);
+ empty_multibyte_string = make_pure_string ("", 0, 0, 1);
}
@@ -2479,6 +2481,9 @@
int length;
{
Lisp_Object val;
+
+ if (!length)
+ return empty_string;
val = make_uninit_multibyte_string (length, length);
STRING_SET_UNIBYTE (val);
return val;
@@ -2497,6 +2502,8 @@
if (nchars < 0)
abort ();
+ if (!nbytes)
+ return empty_multibyte_string;
s = allocate_string ();
allocate_string_data (s, nchars, nbytes);
Index: emacs.c
===================================================================
RCS file: /sources/emacs/emacs/src/emacs.c,v
retrieving revision 1.401
diff -u -r1.401 emacs.c
--- emacs.c 3 Apr 2007 15:25:28 -0000 1.401
+++ emacs.c 26 Apr 2007 13:22:19 -0000
@@ -133,8 +133,8 @@
/* Hook run by `kill-emacs' before it does really anything. */
Lisp_Object Vkill_emacs_hook;
-/* An empty lisp string. To avoid having to build any other. */
-Lisp_Object empty_string;
+/* An empty lisp strings. To avoid having to build any others. */
+Lisp_Object empty_string, empty_multibyte_string;
/* Search path separator. */
Lisp_Object Vpath_separator;
@@ -2468,9 +2468,6 @@
The hook is not run in batch mode, i.e., if `noninteractive' is non-nil. */);
Vkill_emacs_hook = Qnil;
- empty_string = build_string ("");
- staticpro (&empty_string);
-
DEFVAR_INT ("emacs-priority", &emacs_priority,
doc: /* Priority for Emacs to run at.
This value is effective only if set before Emacs is dumped,
Index: lisp.h
===================================================================
RCS file: /sources/emacs/emacs/src/lisp.h,v
retrieving revision 1.574
diff -u -r1.574 lisp.h
--- lisp.h 17 Mar 2007 18:27:10 -0000 1.574
+++ lisp.h 27 Apr 2007 15:23:33 -0000
@@ -701,7 +701,10 @@
#endif /* not GC_CHECK_STRING_BYTES */
/* Mark STR as a unibyte string. */
-#define STRING_SET_UNIBYTE(STR) (XSTRING (STR)->size_byte = -1)
+#define STRING_SET_UNIBYTE(STR) \
+ do { if (EQ (STR, empty_multibyte_string)) \
+ (STR) = empty_string; \
+ else XSTRING (STR)->size_byte = -1; } while (0)
/* Get text properties. */
#define STRING_INTERVALS(STR) (XSTRING (STR)->intervals + 0)
@@ -3060,7 +3063,8 @@
/* defined in emacs.c */
extern Lisp_Object decode_env_path P_ ((char *, char *));
extern Lisp_Object Vinvocation_name, Vinvocation_directory;
-extern Lisp_Object Vinstallation_directory, empty_string;
+extern Lisp_Object Vinstallation_directory;
+extern Lisp_Object empty_string, empty_multibyte_string;
EXFUN (Fkill_emacs, 1);
#if HAVE_SETLOCALE
void fixup_locale P_ ((void));
Index: lread.c
===================================================================
RCS file: /sources/emacs/emacs/src/lread.c,v
retrieving revision 1.369
diff -u -r1.369 lread.c
--- lread.c 28 Mar 2007 08:16:19 -0000 1.369
+++ lread.c 26 Apr 2007 13:22:35 -0000
@@ -4070,8 +4070,7 @@
in order to do so. However, if you want to customize which suffixes
the loading functions recognize as compression suffixes, you should
customize `jka-compr-load-suffixes' rather than the present variable. */);
- /* We don't use empty_string because it's not initialized yet. */
- Vload_file_rep_suffixes = Fcons (build_string (""), Qnil);
+ Vload_file_rep_suffixes = Fcons (empty_string, Qnil);
DEFVAR_BOOL ("load-in-progress", &load_in_progress,
doc: /* Non-nil iff inside of `load'. */);
- Re: using empty_string as the only "" string, (continued)
- Re: using empty_string as the only "" string, Richard Stallman, 2007/04/26
- Re: using empty_string as the only "" string, Dmitry Antipov, 2007/04/26
- Re: using empty_string as the only "" string, Richard Stallman, 2007/04/27
- Re: using empty_string as the only "" string, Dmitry Antipov, 2007/04/27
- Re: using empty_string as the only "" string, David Kastrup, 2007/04/27
- Re: using empty_string as the only "" string, Richard Stallman, 2007/04/28
- Re: using empty_string as the only "" string,
Dmitry Antipov <=
- Re: using empty_string as the only "" string, Richard Stallman, 2007/04/28