From 8d02ce1ed75d008c34a5c9aaa51b67cbb9d33baa Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Tue, 25 Jan 2022 18:24:00 +0000
Subject: [PATCH] patch 8.2.4217: illegal memory access when undo makes Visual
 area invalid

Problem:    Illegal memory access when undo makes Visual area invalid.
Solution:   Correct the Visual area after undo.
---
 src/testdir/test_visual.vim | 15 +++++++++++++++
 src/undo.c                  |  2 ++
 src/version.c               |  2 ++
 3 files changed, 19 insertions(+)

diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index 9b322fd21..b2beda08d 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -1339,5 +1339,20 @@ func Test_visual_ex_copy_line()
   bwipe!
 endfunc
 
+" This was leaving the end of the Visual area beyond the end of a line.
+" Set 'undolevels' to start a new undo block.
+func Test_visual_undo_deletes_last_line()
+  new
+  call setline(1, ["aaa", "ccc", "dyd"])
+  set undolevels=100
+  exe "normal obbbbbbbbbxbb\<Esc>"
+  set undolevels=100
+  /y
+  exe "normal ggvjfxO"
+  undo
+  normal gNU
+  bwipe!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/undo.c b/src/undo.c
index 4d186d453..636144aef 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -3029,6 +3029,8 @@ u_undo_end(
 	}
     }
 #endif
+    if (VIsual_active)
+	check_pos(curbuf, &VIsual);
 
     smsg_attr_keep(0, _("%ld %s; %s #%ld  %s"),
 	    u_oldcount < 0 ? -u_oldcount : u_oldcount,
-- 
2.34.1