def CheckForIncludeWhatYouUse(filename, clean_lines, include_state, error,
                              io=codecs):
  """Reports for missing stl includes.

  This function will output warnings to make sure you are including the headers
  necessary for the stl containers and functions that you use. We only give one
  reason to include a header. For example, if you use both equal_to<> and
  less<> in a .h file, only one (the latter in the file) of these will be
  reported as a reason to include the <functional>.

  Args:
    filename: The name of the current file.
    clean_lines: A CleansedLines instance containing the file.
    include_state: An _IncludeState instance.
    error: The function to call with any errors found.
    io: The IO factory to use to read the header file. Provided for unittest
        injection.
  """
  required = {}  # A map of header name to linenumber and the template entity.
                 # Example of required: { '<functional>': (1219, 'less<>') }

  for linenum in xrange(clean_lines.NumLines()):
    line = clean_lines.elided[linenum]
    if not line or line[0] == '#':
      continue

    # String is special -- it is a non-templatized type in STL.
    matched = _RE_PATTERN_STRING.search(line)
    if matched:
      # Don't warn about strings in non-STL namespaces:
      # (We check only the first match per line; good enough.)
      prefix = line[:matched.start()]
      if prefix.endswith('std::') or not prefix.endswith('::'):
        required['<string>'] = (linenum, 'string')

    for pattern, template, header in _re_pattern_algorithm_header:
      if pattern.search(line):
        required[header] = (linenum, template)

    # The following function is just a speed up, no semantics are changed.
    if not '<' in line:  # Reduces the cpu time usage by skipping lines.
      continue

    for pattern, template, header in _re_pattern_templates:
      if pattern.search(line):
        required[header] = (linenum, template)

  # The policy is that if you #include something in foo.h you don't need to
  # include it again in foo.cc. Here, we will look at possible includes.
  # Let's flatten the include_state include_list and copy it into a dictionary.
  include_dict = dict([item for sublist in include_state.include_list
                       for item in sublist])

  # Did we find the header for this file (if any) and successfully load it?
  header_found = False

  # Use the absolute path so that matching works properly.
  abs_filename = FileInfo(filename).FullName()

  # For Emacs's flymake.
  # If cpplint is invoked from Emacs's flymake, a temporary file is generated
  # by flymake and that file name might end with '_flymake.cc'. In that case,
  # restore original file name here so that the corresponding header file can be
  # found.
  # e.g. If the file name is 'foo_flymake.cc', we should search for 'foo.h'
  # instead of 'foo_flymake.h'
  abs_filename = re.sub(r'_flymake\.cc$', '.cc', abs_filename)

  # include_dict is modified during iteration, so we iterate over a copy of
  # the keys.
  header_keys = include_dict.keys()
  for header in header_keys:
    (same_module, common_path) = FilesBelongToSameModule(abs_filename, header)
    fullpath = common_path + header
    if same_module and UpdateIncludeState(fullpath, include_dict, io):
      header_found = True

  # If we can't find the header file for a .cc, assume it's because we don't
  # know where to look. In that case we'll give up as we're not sure they
  # didn't include it in the .h file.
  # TODO(unknown): Do a better job of finding .h files so we are confident that
  # not having the .h file means there isn't one.
  if filename.endswith('.cc') and not header_found:
    return

  # All the lines have been processed, report the errors found.
  for required_header_unstripped in required:
    template = required[required_header_unstripped][1]
    if required_header_unstripped.strip('<>"') not in include_dict:
      error(filename, required[required_header_unstripped][0],
            'build/include_what_you_use', 4,
            'Add #include ' + required_header_unstripped + ' for ' + template)