From a364cdb648ae009fa7aa05382f5659335683d349 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Thu, 20 Apr 2017 21:12:30 +0200
Subject: [PATCH] patch 8.0.0571: negative line number when using :z^ in an
 empty buffer

Problem:    The cursor line number becomes negative when using :z^ in an empty
            buffer. (neovim #6557)
Solution:   Correct the line number.  Also reset the column.
---
 src/ex_cmds.c             | 8 +++++++-
 src/testdir/test_ex_z.vim | 9 ++++++++-
 src/version.c             | 2 ++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 4b0bdef59c..309474ce04 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -4664,6 +4664,8 @@ ex_z(exarg_T *eap)
 
     if (curs > curbuf->b_ml.ml_line_count)
 	curs = curbuf->b_ml.ml_line_count;
+    else if (curs < 1)
+	curs = 1;
 
     for (i = start; i <= end; i++)
     {
@@ -4686,7 +4688,11 @@ ex_z(exarg_T *eap)
 	}
     }
 
-    curwin->w_cursor.lnum = curs;
+    if (curwin->w_cursor.lnum != curs)
+    {
+	curwin->w_cursor.lnum = curs;
+	curwin->w_cursor.col = 0;
+    }
     ex_no_reprint = TRUE;
 }
 
diff --git a/src/testdir/test_ex_z.vim b/src/testdir/test_ex_z.vim
index 608a36c490..6e03b0bff9 100644
--- a/src/testdir/test_ex_z.vim
+++ b/src/testdir/test_ex_z.vim
@@ -68,7 +68,7 @@ func Test_z()
   bw!
 endfunc
 
-func Test_z_bug()
+func Test_z_overflow()
   " This used to access invalid memory as a result of an integer overflow
   " and freeze vim.
   normal ox
@@ -76,3 +76,10 @@ func Test_z_bug()
   z777777776666666
   ')
 endfunc
+
+func Test_z_negative_lnum()
+  new
+  z^
+  call assert_equal(1, line('.'))
+  bwipe!
+endfunc
diff --git a/src/version.c b/src/version.c
index c169765849..81b98c11fc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    571,
 /**/
     570,
 /**/