@deftypefun {int} {gnutls_set_default_priority_append} (gnutls_session_t @var{session}, const char * @var{add_prio}, const char ** @var{err_pos}, unsigned @var{flags})
@var{session}: is a @code{gnutls_session_t}  type.

@var{add_prio}: is a string describing priorities to be appended to default

@var{err_pos}: In case of an error this will have the position in the string the error occurred

@var{flags}: must be zero

Sets the default priority on the ciphers, key exchange methods,
and macs with the additional options in  @code{add_prio} . This is the recommended method of
setting the defaults when only few additional options are to be added. This promotes
consistency between applications using GnuTLS, and allows GnuTLS using applications
to update settings in par with the library.

The  @code{add_prio} string should start as a normal priority string, e.g.,
'-VERS-TLS-ALL:+VERS-TLS1.3:%COMPAT' or '%FORCE_ETM'. That is, it must not start
with ':'.

To allow a user to override the defaults (e.g., when a user interface
or configuration file is available), the functions
@code{gnutls_priority_set_direct()}  or @code{gnutls_priority_set()}  can
be used.

@strong{Returns:} @code{GNUTLS_E_SUCCESS}  on success, or an error code.

@strong{Since:} 3.6.3
@end deftypefun