(Vsearch_whitespace_regexp): New variable.

(syms_of_search): Defvar it.
(compile_pattern_1): Call re_set_whitespace_regexp with it.
(search_buffer): No regexp is trivial if Vsearch_whitespace_regexp is non-nil.

src/ChangeLog

+2004-11-19  Richard M. Stallman  <rms@gnu.org>
+
+	* search.c (Vsearch_whitespace_regexp): New variable.
+	(syms_of_search): Defvar it.
+	(compile_pattern_1): Call re_set_whitespace_regexp with it.
+	(search_buffer): No regexp is trivial if Vsearch_whitespace_regexp
+	is non-nil.
+
+	* regex.c (regex_compile): Substitute whitespace_regexp
+	for spaces, if it is nonzero.
+	(whitespace_regexp): New variable.
+	(re_set_whitespace_regexp): New function.
+
 2004-11-19  Kim F. Storm  <storm@cua.dk>
 
 	* indent.c (Fvertical_motion): Fix last change.

src/search.c

@@ -83,6 +83,8 @@ static Lisp_Object last_thing_searched;
 
 Lisp_Object Qinvalid_regexp;
 
+Lisp_Object Vsearch_whitespace_regexp;
+
 static void set_search_regs ();
 static void save_search_regs ();
 static int simple_search ();
@@ -161,8 +163,15 @@ compile_pattern_1 (cp, pattern, translate, regp, posix, multibyte)
   BLOCK_INPUT;
   old = re_set_syntax (RE_SYNTAX_EMACS
 		       | (posix ? 0 : RE_NO_POSIX_BACKTRACKING));
+
+  re_set_whitespace_regexp (NILP (Vsearch_whitespace_regexp) ? NULL
+			    : SDATA (Vsearch_whitespace_regexp));
+
   val = (char *) re_compile_pattern ((char *)raw_pattern,
 				     raw_pattern_size, &cp->buf);
+
+  re_set_whitespace_regexp (NULL);
+
   re_set_syntax (old);
   UNBLOCK_INPUT;
   if (val)
@@ -1051,7 +1060,7 @@ search_buffer (string, pos, pos_byte, lim, lim_byte, n,
       return pos;
     }
 
-  if (RE && !trivial_regexp_p (string))
+  if (RE && !(trivial_regexp_p (string) && NILP (Vsearch_whitespace_regexp)))
     {
       unsigned char *p1, *p2;
       int s1, s2;
@@ -2998,6 +3007,14 @@ syms_of_search ()
   saved_last_thing_searched = Qnil;
   staticpro (&saved_last_thing_searched);
 
+  DEFVAR_LISP ("search-whitespace-regexp", &Vsearch_whitespace_regexp,
+      /* doc: Regexp to substitute for bunches of spaces in regexp search.
+Some commands use this for user-specified regexps.
+Spaces that occur inside character classes or repetition operators
+or other such regexp constructs are not replaced with this.
+A value of nil (which is the normal value) means treat spaces literally.  */);
+  Vsearch_whitespace_regexp = Qnil;
+
   defsubr (&Slooking_at);
   defsubr (&Sposix_looking_at);
   defsubr (&Sstring_match);