From bf82e58a702900c70638e8047039fdf5f12f749f Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Wed, 27 Aug 2025 18:14:27 +0200
Subject: [PATCH] patch 9.1.1700: Multiline ignorecase specific pattern does
 not match with 'ignorecase'

Problem:  a pattern that involves a backref on a different line does not
          match when 'ignorecase' is set (QiWei, after v9.1.0645)
Solution: Use MB_STRNICMP when ignorecase is set, fix tests to close
          swapfiles

related: #14756
fixes: #17470
closes: #18104

Signed-off-by: author
Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/regexp.c                     |  5 ++++-
 src/testdir/test_regexp_utf8.vim | 24 ++++++++++++++++++++----
 src/version.c                    |  2 ++
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/regexp.c b/src/regexp.c
index 669b123a3d..dc63cccfcb 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1569,6 +1569,7 @@ reg_nextline(void)
  * Returns RA_FAIL, RA_NOMATCH or RA_MATCH.
  * If "bytelen" is not NULL, it is set to the byte length of the match in the
  * last line.
+ * Optional: ignore case if rex.reg_ic is set.
  */
     static int
 match_with_backref(
@@ -1613,7 +1614,9 @@ match_with_backref(
 	else
 	    len = (int)reg_getline_len(clnum) - ccol;
 
-	if (cstrncmp(p + ccol, rex.input, &len) != 0)
+	// Use case-insensitive compare if rex.reg_ic is set
+	if ((!rex.reg_ic && cstrncmp(p + ccol, rex.input, &len) != 0)
+	    || (rex.reg_ic && MB_STRNICMP(p + ccol, rex.input, len) != 0))
 	    return RA_NOMATCH;  // doesn't match
 	if (bytelen != NULL)
 	    *bytelen += len;
diff --git a/src/testdir/test_regexp_utf8.vim b/src/testdir/test_regexp_utf8.vim
index a4353f1b4b..6eb6bf6fa3 100644
--- a/src/testdir/test_regexp_utf8.vim
+++ b/src/testdir/test_regexp_utf8.vim
@@ -453,7 +453,7 @@ func Run_regexp_multibyte_magic()
   @w
   call assert_equal('k œ̄ṣ́m̥̄ᾱ̆́', getline(18))
 
-  close!
+  bw!
 endfunc
 
 func Test_regexp_multibyte_magic()
@@ -471,7 +471,7 @@ func Test_split_multibyte_to_bytes()
   call setline(1, 'l äö üᾱ̆́')
   s/ \?/ /g
   call assert_equal(' l ä ö ü ᾱ̆́', getline(1))
-  close!
+  bw!
 endfunc
 
 " Test for matchstr() with multibyte characters
@@ -481,7 +481,7 @@ func Test_matchstr_multibyte()
   call assert_equal('בג', matchstr("אבגד", "..", 0, 2))
   call assert_equal('א', matchstr("אבגד", ".", 0, 0))
   call assert_equal('ג', matchstr("אבגד", ".", 4, -1))
-  close!
+  bw!
 endfunc
 
 " Test for 7.4.636
@@ -492,7 +492,7 @@ func Test_search_with_end_offset()
   exe "normal /(/e+\<CR>"
   normal n"ayn
   call assert_equal("a\ncat(", @a)
-  close!
+  bw!
 endfunc
 
 " Check that "^" matches even when the line starts with a combining char
@@ -614,7 +614,23 @@ func Test_search_multibyte_match_ascii()
     call assert_equal(['s', 'ss', 'ſſ', 'ſ'], ic_match3, "Ignorecase Collection Regex-engine: " .. &re)
     call assert_equal(['ſſ','ſ'], noic_match3, "No-Ignorecase Collection Regex-engine: " .. &re)
   endfor
+  set re&vim
   bw!
 endfunc
 
+func Test_replace_multibyte_match_in_multi_lines()
+  new
+  let text = ['ab 1c', 'ab 1c', 'def', '是否 a', '是否 a', 'ghi', '是否a', '是否a', '是否 1', '是否 1']
+  let expected = ['', 'def', '', 'ghi', '', '']
+  for i in range(0, 2)
+    exe "set ignorecase re="..i
+    :%d _
+    call setline(1, text)
+    :%s/\(.\+\)\n\1//g
+    call assert_equal(expected, getline(1, '$'))
+  endfor
+  bw!
+  set ignorecase&vim re&vim
+endfun
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 0bcd55691c..48c5c1c3ea 100644
--- a/src/version.c
+++ b/src/version.c
@@ -724,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1700,
 /**/
     1699,
 /**/