From 6456fae9ba8e72c74b2c0c499eaf09974604ff30 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Tue, 22 Feb 2022 13:37:31 +0000
Subject: [PATCH] patch 8.2.4440: crash with specific regexp pattern and string

Problem:    Crash with specific regexp pattern and string.
Solution:   Stop at the start of the string.

---
 src/regexp_bt.c                  | 5 +++++
 src/testdir/test_regexp_utf8.vim | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index b71b862..e017ba5 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -4431,6 +4431,11 @@ regmatch(
 			    if (rex.input == rex.line)
 			    {
 				// backup to last char of previous line
+				if (rex.lnum == 0)
+				{
+				    status = RA_NOMATCH;
+				    break;
+				}
 				--rex.lnum;
 				rex.line = reg_getline(rex.lnum);
 				// Just in case regrepeat() didn't count
diff --git a/src/testdir/test_regexp_utf8.vim b/src/testdir/test_regexp_utf8.vim
index 6d0ce59..5d1bd47 100644
--- a/src/testdir/test_regexp_utf8.vim
+++ b/src/testdir/test_regexp_utf8.vim
@@ -223,3 +223,10 @@ func Test_match_invalid_byte()
   call delete('Xinvalid')
 endfunc
 
+func Test_match_too_complicated()
+  set regexpengine=1
+  exe "vsplit \xeb\xdb\x99"
+  silent! buf \&\zs*\zs*0
+  bwipe!
+  set regexpengine=0
+endfunc
-- 
2.27.0