From: Christoffer Aasted <dezzadk@gmail.com>
Date: Thu, 18 Jun 2026 19:43:44 +0000 (+0000)
Subject: patch 9.2.0677: Cannot clear the alternate file register #
X-Git-Tag: v9.2.0677^0
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;ds=inline;p=thirdparty%2Fvim.git

patch 9.2.0677: Cannot clear the alternate file register #

Problem:  Cannot clear the alternate file register #
Solution: Allow to clear it (Christoffer Aasted)

closes: #20537

Signed-off-by: Christoffer Aasted <dezzadk@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index b3448bf892..afcdca16b0 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -1,4 +1,4 @@
-*change.txt*	For Vim version 9.2.  Last change: 2026 May 31
+*change.txt*	For Vim version 9.2.  Last change: 2026 Jun 18
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1334,19 +1334,19 @@ and ":put" commands and with CTRL-R.
 		feature}
 							*quote_#* *quote#*
 6. Alternate file register "#
-Contains the name of the alternate file for the current window.  It will
-change how the |CTRL-^| command works.
-This register is writable, mainly to allow for restoring it after a plugin has
-changed it.  It accepts buffer number: >
-    let altbuf = bufnr(@#)
-    ...
-    let @# = altbuf
-It will give error |E86| if you pass buffer number and this buffer does not
-exist.
-It can also accept a match with an existing buffer name: >
+Contains the |alternate-file| name for current window
+This register is writeable and changes which buffer CTRL-^ enters.
+A String is matched against existing buffer names, like |:buffer|: >
     let @# = 'buffer_name'
-Error |E93| if there is more than one buffer matching the given name or |E94|
-if none of buffers matches the given name.
+Also supports using buffer number and |file-pattern|.
+
+Throws
+  |E86| when the buffer number does not exist
+  |E93| when more than one buffer matches
+  |E94| when none match
+
+Clear the register with empty String: >
+    let @# = ''
 
 7. Expression register "=			*quote_=* *quote=* *@=*
 This is not really a register that stores text, but is a way to use an
diff --git a/runtime/doc/version9.txt b/runtime/doc/version9.txt
index a7778b5fef..a515589de5 100644
--- a/runtime/doc/version9.txt
+++ b/runtime/doc/version9.txt
@@ -1,4 +1,4 @@
-*version9.txt*	For Vim version 9.2.  Last change: 2026 Jun 13
+*version9.txt*	For Vim version 9.2.  Last change: 2026 Jun 18
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -52687,6 +52687,7 @@ Changed ~
 - Rewrite the clientserver socketserver backend to use channels and JSON.
 - During |complete()|-triggered completion, CTRL-N and CTRL-P are now subject
   to insert-mode mappings.
+- It is possible to clear the alternate file register |quote#|.
 
 
 							*added-9.3*
diff --git a/src/register.c b/src/register.c
index 358fe6454f..971cd70891 100644
--- a/src/register.c
+++ b/src/register.c
@@ -3152,6 +3152,12 @@ write_reg_contents_ex(
 
     if (name == '#')
     {
+	if (len == 0)
+	{
+	  curwin->w_alt_fnum = 0; // clear altfile
+	  return;
+	}
+
 	buf_T	*buf;
 
 	if (VIM_ISDIGIT(*str))
diff --git a/src/testdir/test_registers.vim b/src/testdir/test_registers.vim
index bb1dd31f3e..1bf3d6f607 100644
--- a/src/testdir/test_registers.vim
+++ b/src/testdir/test_registers.vim
@@ -396,6 +396,11 @@ func Test_set_register()
   call assert_equal('Xfile_alt_1', getreg('#'))
   call setreg('#', b2)
   call assert_equal('Xfile_alt_2', getreg('#'))
+  call setreg('#', '')
+  call assert_equal('', getreg('#'))
+  call setreg('#', 'alt_1')
+  let @# = ''
+  call assert_equal('', getreg('#'))
 
   let ab = 'regwrite'
   call setreg('=', '')
diff --git a/src/version.c b/src/version.c
index 5aa9fde1c1..d2e01aecbc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -759,6 +759,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    677,
 /**/
     676,
 /**/