patch 9.1.0296: regexp: engines do not handle case-folding well

Problem:  Regex engines do not handle case-folding well
Solution: Correctly calculate byte length of characters to skip

When the regexp engine compares two utf-8 codepoints case insensitively
it may match an adjacent character, because it assumes it can step over
as many bytes as the pattern contains.

This however is not necessarily true because of case-folding, a
multi-byte UTF-8 character can be considered equal to some single-byte
value.

Let's consider the pattern 'ſ' and the string 's'. When comparing and
ignoring case, the single character 's' matches, and since it matches
Vim will try to step over the match (by the amount of bytes of the
pattern), assuming that since it matches, the length of both strings is
the same.

However in that case, it should only step over the single byte
value 's' so by 1 byte and try to start matching after it again. So for the
backtracking engine we need to ensure:
- we try to match the correct length for the pattern and the text
- in case of a match, we step over it correctly

The same thing can happen for the NFA engine, when skipping to the next
character to test for a match. We are skipping over the regstart
pointer, however we do not consider the case that because of
case-folding we may need to adjust the number of bytes to skip over. So
this needs to be adjusted in find_match_text() as well.

A related issue turned out, when prog->match_text is actually empty. In
that case we should try to find the next match and skip this condition.

fixes: #14294
closes: #14433

Signed-off-by: Christian Brabandt <cb@256bit.org>

diff --git a/src/mbyte.c b/src/mbyte.c
index d6fb7ecc761d2800138bd70d5f66cd7d71ce4875..3be75099f10e6269718a3c20830fe978700e3bcd 100644 (file)
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -3800,6 +3800,15 @@ utf_strnicmp(
  * Returns zero if s1 and s2 are equal (ignoring case), the difference between
  * two characters otherwise.
  */
+    int
+mb_strnicmp2(char_u *s1, char_u *s2, int n1, int n2)
+{
+    if (n1 == n2 || !enc_utf8)
+       return mb_strnicmp(s1, s2, n1);
+    else
+       return utf_strnicmp(s1, s2, n1, n2);
+}
+
     int
 mb_strnicmp(char_u *s1, char_u *s2, size_t nn)
 {

diff --git a/src/proto/mbyte.pro b/src/proto/mbyte.pro
index 7883b3b4c7331093ea3b3618fed492151eef9794..c49f7e7072a68e3db3c7a8b8d61ee1773879d42e 100644 (file)
--- a/src/proto/mbyte.pro
+++ b/src/proto/mbyte.pro
@@ -48,6 +48,7 @@ int utf_islower(int a);
 int utf_tolower(int a);
 int utf_isupper(int a);
 int mb_strnicmp(char_u *s1, char_u *s2, size_t nn);
+int mb_strnicmp2(char_u *s1, char_u *s2, int n1, int n2);
 void show_utf8(void);
 int latin_head_off(char_u *base, char_u *p);
 int dbcs_screen_head_off(char_u *base, char_u *p);

diff --git a/src/regexp.c b/src/regexp.c
index 4373ae0cfaf41f6e875db7990471e16fded85bc0..4e85ebc29e728059112bab54daf8149023b5cdf9 100644 (file)
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1606,7 +1606,9 @@ mb_decompose(int c, int *c1, int *c2, int *c3)
 /*
  * Compare two strings, ignore case if rex.reg_ic set.
  * Return 0 if strings match, non-zero otherwise.
- * Correct the length "*n" when composing characters are ignored.
+ * Correct the length "*n" when composing characters are ignored
+ * or for utf8 when both utf codepoints are considered equal because of
+ * case-folding but have different length (e.g. 's' and 'ſ')
  */
     static int
 cstrncmp(char_u *s1, char_u *s2, int *n)
@@ -1615,6 +1617,13 @@ cstrncmp(char_u *s1, char_u *s2, int *n)
 
     if (!rex.reg_ic)
        result = STRNCMP(s1, s2, *n);
+    else if (enc_utf8)
+    {
+       int l2 = mb_ptr2len(s2);
+       result = MB_STRNICMP2(s1, s2, *n, l2);
+       if (result == 0 && l2 < *n)
+           *n = l2;
+    }
     else
        result = MB_STRNICMP(s1, s2, *n);
 

diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 5d9450d8712b3f284ca6c23e341ce142e07a58a8..2a03fec579c82feb9e0e897e76650a422b522c38 100644 (file)
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -3816,6 +3816,14 @@ regmatch(
                        }
                    }
                }
+               else if (enc_utf8)
+               {
+                   if (cstrncmp(opnd, rex.input, &len) != 0)
+                   {
+                       status = RA_NOMATCH;
+                       break;
+                   }
+               }
                else
                    for (i = 0; i < len; ++i)
                        if (opnd[i] != rex.input[i])

diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 5e4fadd028bdcae30bc109a5c6d9f0315e291183..451720a09dd88c192d19a9104bf42c69dea620fc 100644 (file)
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -5666,7 +5666,12 @@ find_match_text(colnr_T *startcol, int regstart, char_u *match_text)
     for (;;)
     {
        match = TRUE;
-       len2 = MB_CHAR2LEN(regstart); // skip regstart
+       // skip regstart
+       len2 = MB_CHAR2LEN(regstart);
+       if (enc_utf8 && len2 > 1 && MB_CHAR2LEN(PTR2CHAR(rex.line + col)) != len2)
+           // because of case-folding of the previously matched text, we may need
+           // to skip fewer bytes than mb_char2len(regstart)
+           len2 = mb_char2len(utf_fold(regstart));
        for (len1 = 0; match_text[len1] != NUL; len1 += MB_CHAR2LEN(c1))
        {
            c1 = PTR2CHAR(match_text + len1);
@@ -7503,7 +7508,7 @@ nfa_regexec_both(
 
        // If match_text is set it contains the full text that must match.
        // Nothing else to try. Doesn't handle combining chars well.
-       if (prog->match_text != NULL && !rex.reg_icombine)
+       if (prog->match_text != NULL && *prog->match_text != NUL && !rex.reg_icombine)
        {
            retval = find_match_text(&col, prog->regstart, prog->match_text);
            if (REG_MULTI)

diff --git a/src/testdir/test_regexp_utf8.vim b/src/testdir/test_regexp_utf8.vim
index 6669dee57e4cc7af650ed2d5bb4ba297c6da5d11..9980e5b7f5505e47142b5825522f6f882bdb4305 100644 (file)
--- a/src/testdir/test_regexp_utf8.vim
+++ b/src/testdir/test_regexp_utf8.vim
@@ -587,4 +587,32 @@ func Test_combining_chars_in_collection()
   bw!
 endfunc
 
+func Test_search_multibyte_match_ascii()
+  new
+  " Match single 'ſ' and 's'
+  call setline(1,  'das abc heraus abc ſich abc ſind')
+  for i in range(0, 2)
+    exe "set re="..i
+    let ic_match = matchbufline('%', '\c\%u17f', 1, '$')->mapnew({idx, val -> val.text})
+    let noic_match = matchbufline('%', '\C\%u17f', 1, '$')->mapnew({idx, val -> val.text})
+    call assert_equal(['s', 's', 'ſ','ſ'], ic_match, "Ignorecase Regex-engine: " .. &re)
+    call assert_equal(['ſ','ſ'], noic_match, "No-Ignorecase Regex-engine: " .. &re)
+  endfor
+  " Match several 'ſſ' and 'ss'
+  call setline(1,  'das abc herauss abc ſſich abc ſind')
+  for i in range(0, 2)
+    exe "set re="..i
+    let ic_match = matchbufline('%', '\c\%u17f\%u17f', 1, '$')->mapnew({idx, val -> val.text})
+    let noic_match = matchbufline('%', '\C\%u17f\%u17f', 1, '$')->mapnew({idx, val -> val.text})
+    let ic_match2 = matchbufline('%', '\c\%u17f\+', 1, '$')->mapnew({idx, val -> val.text})
+    let noic_match2 = matchbufline('%', '\C\%u17f\+', 1, '$')->mapnew({idx, val -> val.text})
+
+    call assert_equal(['ss', 'ſſ'], ic_match, "Ignorecase Regex-engine: " .. &re)
+    call assert_equal(['ſſ'], noic_match, "No-Ignorecase Regex-engine: " .. &re)
+    call assert_equal(['s', 'ss', 'ſſ', 'ſ'], ic_match2, "Ignorecase Regex-engine: " .. &re)
+    call assert_equal(['ſſ','ſ'], noic_match2, "No-Ignorecase Regex-engine: " .. &re)
+  endfor
+  bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

diff --git a/src/version.c b/src/version.c
index 2c6e7d02fdcbaaf4f3cc21200578217c7f961d5a..c63b141aa9399140318a292a91c4fcab639c8a46 100644 (file)
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    296,
 /**/
     295,
 /**/

diff --git a/src/vim.h b/src/vim.h
index 4507674fcde6efb73c2ab9455f0f4ab969120d3c..33d592038d1f2dead21e883bf142566e69ca4661 100644 (file)
--- a/src/vim.h
+++ b/src/vim.h
@@ -1751,6 +1751,7 @@ void *vim_memset(void *, int, size_t);
 
 # define MB_STRICMP(d, s)      mb_strnicmp((char_u *)(d), (char_u *)(s), (int)MAXCOL)
 # define MB_STRNICMP(d, s, n)  mb_strnicmp((char_u *)(d), (char_u *)(s), (int)(n))
+# define MB_STRNICMP2(d, s, n1, n2)    mb_strnicmp2((char_u *)(d), (char_u *)(s), (int)(n1), (int)(n2))
 
 #define STRCAT(d, s)       strcat((char *)(d), (char *)(s))
 #define STRNCAT(d, s, n)    strncat((char *)(d), (char *)(s), (size_t)(n))