From: Hirohito Higashi <h.east.727@gmail.com>
Date: Sat, 1 Aug 2026 13:26:21 +0000 (+0000)
Subject: patch 9.2.0891: MS-Windows: filename-modifier ":8:t" causes underflow
X-Git-Tag: v9.2.0891^0
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=a3df0ea61b708534fb0a2277216adaacf79ece43;p=thirdparty%2Fvim.git

patch 9.2.0891: MS-Windows: filename-modifier ":8:t" causes underflow

Problem:  On MS-Windows using ":8" with ":t", ":e" or ":r" in one
          fnamemodify() gives a wrong result or an out of memory error.
Solution: Recompute the tail after ":8" replaced the name
          (Hirohito Higashi).

related: #20899
closes:  #20903

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/src/filepath.c b/src/filepath.c
index 8bdba335c6..e70b9c300b 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -586,6 +586,10 @@ repeat:
 	    }
 	    *fnamelen = l;
 	}
+
+	// The name was replaced by the short name, "tail" points into the
+	// previous name.
+	tail = gettail(*fnamep);
     }
 #endif // MSWIN
 
diff --git a/src/testdir/test_shortpathname.vim b/src/testdir/test_shortpathname.vim
index b3d7b82be5..a1d9d9816e 100644
--- a/src/testdir/test_shortpathname.vim
+++ b/src/testdir/test_shortpathname.vim
@@ -101,4 +101,24 @@ func Test_ColonEight_notexists()
   call assert_equal(non_exists, fnamemodify(non_exists, ':p:8'))
 endfunc
 
+" ":8" replaces the name, the modifiers after it must use the new name.
+func Test_ColonEight_then_tail()
+  let dir = 'c:/Xtest_C8tail'
+  call s:SetupDir(dir)
+
+  let file = dir . '/longfilename.txt'
+
+  call mkdir(dir, 'D')
+  call writefile([], file, 'D')
+
+  let sfile = fnamemodify(file, ':p:8')
+  if sfile ==? fnamemodify(file, ':p')
+    throw 'Skipped: 8.3 short names are not created on this volume'
+  endif
+
+  call assert_equal(fnamemodify(sfile, ':t'), fnamemodify(file, ':p:8:t'))
+  call assert_equal(fnamemodify(sfile, ':e'), fnamemodify(file, ':p:8:e'))
+  call assert_equal(fnamemodify(sfile, ':r'), fnamemodify(file, ':p:8:r'))
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 09996f74bd..c48aca0ff4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    891,
 /**/
     890,
 /**/