# Please add "source /path/to/bash-autocomplete.sh" to your .bashrc to use this.
_clang()
{
  local cur prev words cword arg flags
  _init_completion -n : || return

  # bash always separates '=' as a token even if there's no space before/after '='.
  # On the other hand, '=' is just a regular character for clang options that
  # contain '='. For example, "-stdlib=" is defined as is, instead of "-stdlib" and "=".
  # So, we need to partially undo bash tokenization here for integrity.
  local w1="${COMP_WORDS[$cword - 1]}"
  local w2="${COMP_WORDS[$cword - 2]}"
  if [[ "$cur" == -* ]]; then
    # -foo<tab>
    arg="$cur"
  elif [[ "$w1" == -*  && "$cur" == '=' ]]; then
    # -foo=<tab>
    arg="$w1=,"
  elif [[ "$w1" == -* ]]; then
    # -foo <tab> or -foo bar<tab>
    arg="$w1,$cur"
  elif [[ "$w2" == -* && "$w1" == '=' ]]; then
    # -foo=bar<tab>
    arg="$w2=,$cur"
  fi

  flags=$( "${COMP_WORDS[0]}" --autocomplete="$arg" 2>/dev/null )
  # If clang is old that it does not support --autocomplete,
  # fall back to the filename completion.
  if [[ "$?" != 0 ]]; then
    _filedir
    return
  fi

  if [[ "$cur" == '=' ]]; then
    COMPREPLY=( $( compgen -W "$flags" -- "") )
  elif [[ "$flags" == "" || "$arg" == "" ]]; then
    _filedir
  else
    # Bash automatically appends a space after '=' by default.
    # Disable it so that it works nicely for options in the form of -foo=bar.
    [[ "${flags: -1}" == '=' ]] && compopt -o nospace
    COMPREPLY=( $( compgen -W "$flags" -- "$cur" ) )
  fi
}
complete -F _clang clang