In search.c simple_search(), a reverse search can underrun the buffer.
In a debug build, this will assert in DEC_BYTEBPOS. This doesn't
happen on most reverse searches because you need the initial substring
of the buffer to match the tail of the pattern, or the buffer pointer
won't get to where it tries to decrement from 1.
At least, that's what I think is going on. I will commit when I've
constructed a test case and verified the theory.
This patch also includes the usual marginal doc "IMHO improvements".
This patch is informational only, I used cvs diff -w to generate it.
Do not apply this patch.
RCS file: /pack/xemacscvs/XEmacs/xemacs/src/ChangeLog,v
retrieving revision 1.1112
diff -u -U0 -r1.1112 ChangeLog
--- src/ChangeLog 5 Dec 2007 08:26:00 -0000 1.1112
+++ src/ChangeLog 5 Dec 2007 09:08:30 -0000
＠＠ -0,0 +1,5 ＠＠
+2007-12-05 Stephen J. Turnbull <stephen(a)xemacs.org>
+ * search.c (simple_search): Fix underrun in reverse search.
+ (search_buffer): Clarify decision to use boyer_moore or not.
RCS file: /pack/xemacscvs/XEmacs/xemacs/src/search.c,v
retrieving revision 1.47
diff -u -w -r1.47 search.c
--- src/search.c 1 Oct 2007 08:07:53 -0000 1.47
+++ src/search.c 5 Dec 2007 09:08:34 -0000
＠＠ -1371,14 +1371,17 ＠＠
boyer_moore_ok = 0;
if (translated != c || inverse != c)
- /* Keep track of which character set row
- contains the characters that need translation. */
+ /* Keep track of which charset and character set row
+ contains the characters that need translation.
+ Zero out the bits corresponding to the last byte.
int charset_base_code = c & ~ICHAR_FIELD3_MASK;
if (charset_base == -1)
charset_base = charset_base_code;
else if (charset_base != charset_base_code)
- /* If two different rows appear, needing translation,
- then we cannot use boyer_moore search. */
+ /* If two different rows appear, needing translation, then
+ we cannot use boyer_moore search. See the comment at the
+ head of boyer_moore(). */
boyer_moore_ok = 0;
memcpy (pat, tmp_str, new_bytelen);
＠＠ -1468,6 +1471,13 ＠＠
+ /* If lim < len, then there are too few buffer positions to hold the
+ pattern between the beginning of the buffer and lim. Adjust to
+ ensure pattern fits. If we don't do this, we can assert in the
+ DEC_BYTEBPOS below. */
+ if (lim < len)
+ lim = len;
while (n < 0)
＠＠ -1505,6 +1515,7 ＠＠
if (n == 0)
XEmacs-Patches mailing list