From fef66301665027f1801a18d796f74584666f41ef Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Mon, 29 Jan 2024 21:46:58 +0100
Subject: [PATCH] patch 9.1.0065: Segfault with CompleteChanged autocommand

Problem:  Segfault with CompleteChanged autocommand
          (markonm )
Solution: Test match->cp_prev for being NULL before accessing it

closes: #13929

Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/insexpand.c                   |  3 ++-
 src/testdir/test_ins_complete.vim | 16 +++++++++++++++-
 src/version.c                     |  2 ++
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/insexpand.c b/src/insexpand.c
index e870147012..ba66e51cfb 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -3075,7 +3075,8 @@ info_add_completion_info(list_T *li)
 
     // Skip the element with the CP_ORIGINAL_TEXT flag at the beginning, in case of
     // forward completion, or at the end, in case of backward completion.
-    match = forward ? match->cp_next : (compl_no_select && match_at_original_text(match) ? match->cp_prev : match->cp_prev->cp_prev);
+    match = forward || match->cp_prev == NULL ? match->cp_next :
+	(compl_no_select && match_at_original_text(match) ? match->cp_prev : match->cp_prev->cp_prev);
 
     while (match != NULL && !match_at_original_text(match))
     {
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index 61ddcd378b..1b6eafe8f0 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -2359,4 +2359,18 @@ func Test_complete_info_index()
   bwipe!
 endfunc
 
-" vim: shiftwidth=2 sts=2 expandtab
+func Test_complete_changed_complete_info()
+  CheckRunVimInTerminal
+  " this used to crash vim, see #13929
+  let lines =<< trim END
+    set completeopt=menuone
+    autocmd CompleteChanged * call complete_info(['items'])
+    call feedkeys("iii\<cr>\<c-p>")
+  END
+  call writefile(lines, 'Xsegfault', 'D')
+  let buf = RunVimInTerminal('-S Xsegfault', #{rows: 5})
+  call WaitForAssert({-> assert_match('^ii', term_getline(buf, 1))}, 1000)
+  call StopVimInTerminal(buf)
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab nofoldenable
diff --git a/src/version.c b/src/version.c
index cf123b5b2a..b361a9caa0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    65,
 /**/
     64,
 /**/