XS(XS_Test_add_interface) 
{ 
    dXSARGS; 
    dXSFUNCTION(int); 
    if (items != 1) 
        Perl_croak(aTHX_ "Usage: Test::add_interface(i)"); 
    { 
        int     i = (int)SvIV(ST(0)); 
        int     RETVAL; 
        dXSTARG; 
        XSFUNCTION = XSINTERFACE_FUNC(int,cv,XSANY.any_dptr); 
 
        RETVAL = XSFUNCTION(i); 
        XSprePUSH; PUSHi((IV)RETVAL); 
    } 
    XSRETURN(1); 
}