def parse_include(self, start):
        i = start
        while i:
            if self.text[i] == '\n':
                i += 1
                break
            i -= 1
        line_start = i
        if not (self.text[line_start:start] == "" or self.text[line_start:start].isspace()):
            self.env.msg.fatal(
                "Unexpected text before include",
                messages.SourceRef(line_start, start-1, filename=self.path)
            )
        inc_regex = re.compile(r'`include\s+("([^\r\n]+)"|<([^\r\n]+)>)')
        m_inc = inc_regex.match(self.text, start)
        if m_inc is None:
            self.env.msg.fatal(
                "Invalid usage of include directive",
                messages.SourceRef(start, start+7, filename=self.path)
            )
        incl_path_raw = m_inc.group(2) or m_inc.group(3)
        end = m_inc.end(0)-1
        path_start = m_inc.start(1)
        tail_regex = re.compile(r'(?:[ \t]*/\*[^\r\n]*?\*/)*[ \t]*(?://[^\r\n]*?|/\*[^\r\n]*?)?\r?\n')
        if not tail_regex.match(self.text, end+1):
            tail_capture_regex = re.compile(r'[^\r\n]*?\r?\n')
            m = tail_capture_regex.match(self.text, end+1)
            self.env.msg.fatal(
                "Unexpected text after include",
                messages.SourceRef(end+1, m.end(0)-1, filename=self.path)
            )
        if os.path.isabs(incl_path_raw):
            incl_path = incl_path_raw
        else:
            for search_path in self.search_paths:
                incl_path = os.path.join(search_path, incl_path_raw)
                if os.path.isfile(incl_path):
                    break
            else:
                incl_path = os.path.join(os.path.dirname(self.path), incl_path_raw)
        if not os.path.isfile(incl_path):
            self.env.msg.fatal(
                "Could not find '%s' in include search paths" % incl_path_raw,
                messages.SourceRef(path_start, end, filename=self.path)
            )
        incl_ref = self.incl_ref
        while incl_ref:
            if os.path.samefile(incl_path, incl_ref.path):
                self.env.msg.fatal(
                    "Include of '%s' results in a circular reference" % incl_path_raw,
                    messages.SourceRef(path_start, end, filename=self.path)
                )
            incl_ref = incl_ref.parent
        return(end, incl_path)