Function parse_sub_exp

compat/regex/regcomp.c:2448–2482

  return tree;
}

/* This function build the following tree, from regular expression
   (<reg_exp>):
	 SUBEXP
	    |
	<reg_exp>
*/

static bin_tree_t *
parse_sub_exp (re_string_t *regexp, regex_t *preg, re_token_t *token,
	       reg_syntax_t syntax, int nest, reg_errcode_t *err)
{
  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
  bin_tree_t *tree;
  size_t cur_nsub;
  cur_nsub = preg->re_nsub++;

  fetch_token (token, regexp, syntax | RE_CARET_ANCHORS_HERE);

  /* The subexpression may be a null string.  */
  if (token->type == OP_CLOSE_SUBEXP)
    tree = NULL;
  else
    {
      tree = parse_reg_exp (regexp, preg, token, syntax, nest, err);
      if (BE (*err == REG_NOERROR && token->type != OP_CLOSE_SUBEXP, 0))
	*err = REG_EPAREN;
      if (BE (*err != REG_NOERROR, 0))
	return NULL;
    }

  if (cur_nsub <= '9' - '1')
    dfa->completed_bkref_map |= 1 << cur_nsub;

  tree = create_tree (dfa, tree, NULL, SUBEXP);
  if (BE (tree == NULL, 0))
    {