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Fix regexp matching with atomic strings and optimised backtracking

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This bug occurs when an atomic pattern is matched at the end of
a string and the on-failure-keep-string-jump optimisation is
in effect, as in:

  (string-match "\\'\\(?:ab\\)*\\'" "a")

which succeeded but clearly should not (bug#58726).

Reported by Michael Heerdegen.

* src/regex-emacs.c (PREFETCH): Add reset parameter.
(re_match_2_internal): Use it for proper atomic pattern treatment.
* test/src/regex-emacs-tests.el (regexp-atomic-failure): New test.
This commit is contained in:
Mattias Engdegård 2022-10-23 15:40:37 +02:00
parent b5ada7aa6f
commit 36f5a1a7e7
2 changed files with 14 additions and 5 deletions
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14
src/regex-emacs.c
View File

@ -3446,14 +3446,18 @@ static bool bcmp_translate (re_char *, re_char *, ptrdiff_t,
/* Call before fetching a character with *d. This switches over to
string2 if necessary.
`reset' is executed before backtracking if there are no more characters.
Check re_match_2_internal for a discussion of why end_match_2 might
not be within string2 (but be equal to end_match_1 instead). */
#define PREFETCH() \
#define PREFETCH(reset) \
while (d == dend) \
{ \
/* End of string2 => fail. */ \
if (dend == end_match_2) \
goto fail; \
{ \
reset; \
goto fail; \
} \
/* End of string1 => advance to string2. */ \
d = string2; \
dend = end_match_2; \
@ -4252,7 +4256,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
int pat_charlen, buf_charlen;
int pat_ch, buf_ch;
PREFETCH ();
PREFETCH (d = dfail);
if (multibyte)
pat_ch = string_char_and_length (p, &pat_charlen);
else
@ -4280,7 +4284,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
int pat_charlen;
int pat_ch, buf_ch;
PREFETCH ();
PREFETCH (d = dfail);
if (multibyte)
{
pat_ch = string_char_and_length (p, &pat_charlen);
@ -4486,7 +4490,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
if (d2 == dend2) break;
/* If necessary, advance to next segment in data. */
PREFETCH ();
PREFETCH (d = dfail);
/* How many characters left in this segment to match. */
dcnt = dend - d;

5
test/src/regex-emacs-tests.el
View File

@ -867,4 +867,9 @@ This evaluates the TESTS test cases from glibc."
(should (equal (string-match "[[:lower:]]" "ẞ") 0))
(should (equal (string-match "[[:upper:]]" "ẞ") 0))))
(ert-deftest regexp-atomic-failure ()
"Bug#58726."
(should (equal (string-match "\\`\\(?:ab\\)*\\'" "a") nil))
(should (equal (string-match "\\`a\\{2\\}*\\'" "a") nil)))
;;; regex-emacs-tests.el ends here