patch 8.0.0561: undefined behavior when using backslash after empty line commit https://github.com/vim/vim/commit/478af67dd6a9adc456464c3736bda328ae3a28cb Author: Bram Moolenaar <Bram@vim.org> Date: Mon Apr 10 22:22:42 2017 +0200 patch 8.0.0561: undefined behavior when using backslash after empty line Problem: Undefined behavior when using backslash after empty line. Solution: Check for an empty line. (Dominique Pelle, closes https://github.com/vim/vim/issues/1631)

" Tests for the Tcl interface.

if !has('tcl')
  finish
end

function Test_tcldo()
  " Check deleting lines does not trigger ml_get error.
  new
  call setline(1, ['one', 'two', 'three'])
  tcldo ::vim::command %d_
  bwipe!

  " Check switching to another buffer does not trigger ml_get error.
  new
  let wincount = winnr('$')
  call setline(1, ['one', 'two', 'three'])
  tcldo ::vim::command new
  call assert_equal(wincount + 1, winnr('$'))
  bwipe!
  bwipe!
endfunc