Versions

libc {
  GLIBC_2.1 {
    # variables in normal name space
    argp_err_exit_status; argp_program_bug_address; argp_program_version;
    argp_program_version_hook;

    # a*
    argp_error; argp_failure; argp_help; argp_parse; argp_state_help;
    argp_usage;
  }
}