Description:
------------
Oniguruma has
onig_set_match_stack_limit_size()
and it should be used for mbregex.

extern int main(int argc, char* argv[])
{
#define MAX_SIZE   1000000

  int len;
  int i;
  char s[MAX_SIZE];

  len = atoi(argv[1]);
  fprintf(stdout, "len: %d\n", len);
  for (i = 0; i < len; i++) {
    s[i] = ' ';
  }
  s[len] = 'a';
  s[len + 1] = '\0';

  onig_set_match_stack_limit_size(30000);

  exec(ONIG_ENCODING_UTF8, ONIG_ENCODING_UTF8, ONIG_OPTION_NONE,
       "\\s+$", s);
  return 0;
}