GCCGO __FILE__ and __LINE__ builtin constants

gcc_go_frontend_lex.cc

// Pick up an identifier.

Token
Lex::gather_identifier()
{
...
  if (has_non_ascii_char)
    return Token::make_identifier_token(buf, is_exported, location);
  else
    {
      Keyword code = keywords.keyword_to_code(pstart, p - pstart);
      if (code == KEYWORD_INVALID)
      {
	buf.assign(pstart, p - pstart);
	if(buf.size() > 1 && buf[0] == '_')
	{
		if(buf == "__LINE__")
		{
			mpz_t val;
			mpz_init_set_ui(val, this->lineno_);
			Token ret = Token::make_integer_token(val, location);
			mpz_clear(val);
			return ret;
		}
		else if(buf == "__FILE__")
		{
			buf = this->input_file_name_;
			return Token::make_string_token(buf, location);
		}
	}

	return Token::make_identifier_token(buf,
					    is_exported, location);
    }
    else
	{
	  switch (code)
...
}