new

static VALUE
syserr_initialize(int argc, VALUE *argv, VALUE self)
{
#if !defined(_WIN32)
    char *strerror();
#endif
    const char *err;
    VALUE mesg, error;
    VALUE klass = rb_obj_class(self);

    if (klass == rb_eSystemCallError) {
        st_data_t data = (st_data_t)klass;
        rb_scan_args(argc, argv, "11", &mesg, &error);
        if (argc == 1 && FIXNUM_P(mesg)) {
            error = mesg; mesg = Qnil;
        }
        if (!NIL_P(error) && st_lookup(syserr_tbl, NUM2LONG(error), &data)) {
            klass = (VALUE)data;
            /* change class */
            if (TYPE(self) != T_OBJECT) { /* insurance to avoid type crash */
                rb_raise(rb_eTypeError, "invalid instance type");
            }
            RBASIC(self)->klass = klass;
        }
    }
    else {
        rb_scan_args(argc, argv, "01", &mesg);
        error = rb_const_get(klass, rb_intern("Errno"));
    }
    if (!NIL_P(error)) err = strerror(NUM2INT(error));
    else err = "unknown error";
    if (!NIL_P(mesg)) {
        rb_encoding *le = rb_locale_encoding();
        VALUE str = StringValue(mesg);
        rb_encoding *me = rb_enc_get(mesg);

        mesg = rb_sprintf("%s - %.*s", err,
                          (int)RSTRING_LEN(str), RSTRING_PTR(str));
        if (le != me && rb_enc_asciicompat(me)) {
            le = me;
        }/* else assume err is non ASCII string. */
        OBJ_INFECT(mesg, str);
        rb_enc_associate(mesg, le);
    }
    else {
        mesg = rb_str_new2(err);
        rb_enc_associate(mesg, rb_locale_encoding());
    }
    rb_call_super(1, &mesg);
    rb_iv_set(self, "errno", error);
    return self;
}