commit https://github.com/vim/vim/commit/d3c907b5d2b352482b580a0cf687cbbea4c19ea1 Author: Bram Moolenaar <Bram@vim.org> Date: Wed Aug 17 21:32:09 2016 +0200 patch 7.4.2223 Problem: Buffer overflow when using latin1 character with feedkeys(). Solution: Check for an illegal character. Add a test.

" Test for joining lines.

func Test_join_with_count()
  new
  call setline(1, ['one', 'two', 'three', 'four'])
  normal J
  call assert_equal('one two', getline(1))
  %del
  call setline(1, ['one', 'two', 'three', 'four'])
  normal 10J
  call assert_equal('one two three four', getline(1))
  quit!
endfunc