From 2116ff47eadd54fefc1dd6f7f13431feda64acb5 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Sun, 17 Apr 2022 09:44:47 +0800
Subject: [PATCH 1/2] vim-patch:8.2.0791: a second popup window with terminal
 causes trouble

Problem:    A second popup window with terminal causes trouble.
Solution:   Disallow opening a second terminal-popup window. (closes vim/vim#6101,
            closes vim/vim#6103) Avoid defaulting to an invalid line number.
https://github.com/vim/vim/commit/b5383b174b2436b556f76f14badb1c1f55d6d8f6

This is the only applicable hunk.
---
 src/nvim/ex_docmd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index cbfe6e3789..fc0bb48803 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -2373,8 +2373,13 @@ int parse_cmd_address(exarg_T *eap, char **errormsg, bool silent)
     switch (eap->addr_type) {
     case ADDR_LINES:
     case ADDR_OTHER:
-      // default is current line number
-      eap->line2 = curwin->w_cursor.lnum;
+      // Default is the cursor line number.  Avoid using an invalid
+      // line number though.
+      if (curwin->w_cursor.lnum > curbuf->b_ml.ml_line_count) {
+        eap->line2 = curbuf->b_ml.ml_line_count;
+      } else {
+        eap->line2 = curwin->w_cursor.lnum;
+      }
       break;
     case ADDR_WINDOWS:
       eap->line2 = CURRENT_WIN_NR;

From f823dce100abcc06a12258d92b792fe01d1fe398 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Sun, 17 Apr 2022 09:46:42 +0800
Subject: [PATCH 2/2] test: add a test for #18135

---
 test/functional/ex_cmds/quickfix_commands_spec.lua | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/test/functional/ex_cmds/quickfix_commands_spec.lua b/test/functional/ex_cmds/quickfix_commands_spec.lua
index c956a2df2d..94b7fa1a84 100644
--- a/test/functional/ex_cmds/quickfix_commands_spec.lua
+++ b/test/functional/ex_cmds/quickfix_commands_spec.lua
@@ -109,4 +109,17 @@ describe('quickfix', function()
     ]])
     eq({0, 6, 1, 0, 1}, funcs.getcurpos())
   end)
+
+  it('BufAdd does not cause E16 when reusing quickfix buffer #18135', function()
+    local file = file_base .. '_reuse_qfbuf_BufAdd'
+    write_file(file, ('\n'):rep(100) .. 'foo')
+    source([[
+      set grepprg=internal
+      autocmd BufAdd * call and(0, 0)
+      autocmd QuickFixCmdPost grep ++nested cclose | cwindow
+    ]])
+    command('grep foo ' .. file)
+    command('grep foo ' .. file)
+    os.remove(file)
+  end)
 end)