Fail regular-expression searches immediately at end of range. This

prevents various infinite loops from patterns that match the null
string.

diff --git a/v7/src/edwin/regexp.scm b/v7/src/edwin/regexp.scm
index 4f7bfe4cc4f80b7f49837c87e0da5e33c0a3b4df..b1b3de086e54240b0a5c9306e3fb833471f392bb 100644 (file)
--- a/v7/src/edwin/regexp.scm
+++ b/v7/src/edwin/regexp.scm
@@ -1,10 +1,10 @@
 #| -*-Scheme-*-
 
-$Id: regexp.scm,v 1.83 2004/11/19 16:54:18 cph Exp $
+$Id: regexp.scm,v 1.84 2006/02/18 04:56:22 cph Exp $
 
 Copyright 1986,1989,1991,1992,1993,1995 Massachusetts Institute of Technology
 Copyright 1996,1997,1999,2001,2002,2003 Massachusetts Institute of Technology
-Copyright 2004 Massachusetts Institute of Technology
+Copyright 2004,2006 Massachusetts Institute of Technology
 
 This file is part of MIT/GNU Scheme.
 
@@ -215,24 +215,26 @@ USA.
           (make-mark group index)))))
 
 (define (re-search-buffer-forward regexp syntax-table group start end)
-  (let ((index
-        ((ucode-primitive re-search-buffer-forward)
-         (compiled-regexp/byte-stream regexp)
-         (compiled-regexp/translation-table regexp)
-         (syntax-table-argument syntax-table)
-         registers group start end)))
-    (set! match-group (compute-match-group group index))
-    index))
+  (and (fix:< start end)
+       (let ((index
+             ((ucode-primitive re-search-buffer-forward)
+              (compiled-regexp/byte-stream regexp)
+              (compiled-regexp/translation-table regexp)
+              (syntax-table-argument syntax-table)
+              registers group start end)))
+        (set! match-group (compute-match-group group index))
+        index)))
 
 (define (re-search-buffer-backward regexp syntax-table group start end)
-  (let ((index
-        ((ucode-primitive re-search-buffer-backward)
-         (compiled-regexp/byte-stream regexp)
-         (compiled-regexp/translation-table regexp)
-         (syntax-table-argument syntax-table)
-         registers group start end)))
-    (set! match-group (compute-match-group group index))
-    index))
+  (and (fix:< start end)
+       (let ((index
+             ((ucode-primitive re-search-buffer-backward)
+              (compiled-regexp/byte-stream regexp)
+              (compiled-regexp/translation-table regexp)
+              (syntax-table-argument syntax-table)
+              registers group start end)))
+        (set! match-group (compute-match-group group index))
+        index)))
 
 (define (re-match-buffer-forward regexp syntax-table group start end)
   (let ((index