From 44db8213d38c39877d2148eff6a72f4beccfb94e Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Tue, 25 Jan 2022 21:26:17 +0000
Subject: [PATCH] patch 8.2.4219: reading before the start of the line

Problem:    Reading before the start of the line.
Solution:   Check boundary before trying to read the character.
---
 src/register.c              | 2 +-
 src/testdir/test_visual.vim | 7 +++++++
 src/version.c               | 2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/register.c b/src/register.c
index d604bae6b0deb..03f7f4ec9604c 100644
--- a/src/register.c
+++ b/src/register.c
@@ -1474,7 +1474,7 @@ yank_copy_line(struct block_def *bd, long y_idx, int exclude_trailing_space)
     {
 	int s = bd->textlen + bd->endspaces;
 
-	while (VIM_ISWHITE(*(bd->textstart + s - 1)) && s > 0)
+	while (s > 0 && VIM_ISWHITE(*(bd->textstart + s - 1)))
 	{
 	    s = s - (*mb_head_off)(bd->textstart, bd->textstart + s - 1) - 1;
 	    pnew--;
diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index b2beda08d0aa8..af54615c48a10 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -1247,6 +1247,13 @@ func Test_visual_put_blockedit_zy_and_zp()
   bw!
 endfunc
 
+func Test_visual_block_yank_zy()
+  new
+  " this was reading before the start of the line
+  exe "norm o\<C-T>\<Esc>\<C-V>zy"
+  bwipe!
+endfunc
+
 func Test_visual_block_with_virtualedit()
   CheckScreendump
 
diff --git a/src/version.c b/src/version.c
index 9dcf34928f8de..a3efb046bdf58 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4219,
 /**/
     4218,
 /**/