patch 8.0.0636: when reading the undo file fails may use uninitialized data commit https://github.com/vim/vim/commit/56f2db562ddc6c69026d55360f0cfaacd8adc26a Author: Bram Moolenaar <Bram@vim.org> Date: Sun Jun 11 23:09:15 2017 +0200 patch 8.0.0636: when reading the undo file fails may use uninitialized data Problem: When reading the undo file fails may use uninitialized data. Solution: Always clear the buffer on failure.

" 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