new

/*
 * call-seq:
 *   SystemCallError.new(msg, errno)  => system_call_error_subclass
 *
 * If _errno_ corresponds to a known system error code, constructs
 * the appropriate <code>Errno</code> class for that error, otherwise
 * constructs a generic <code>SystemCallError</code> object. The
 * error number is subsequently available via the <code>errno</code>
 * method.
 */

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

    if (klass == rb_eSystemCallError) {
        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), &klass)) {
            /* 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(NUM2LONG(error));
    else err = "unknown error";
    if (!NIL_P(mesg)) {
        VALUE str = mesg;
        size_t len;

        StringValue(str);
        len = strlen(err)+RSTRING(str)->len+3;
        mesg = rb_str_new(0, len);
        snprintf(RSTRING(mesg)->ptr, len+1, "%s - %.*s", err,
                (int)RSTRING(str)->len, RSTRING(str)->ptr);
        rb_str_resize(mesg, strlen(RSTRING(mesg)->ptr));
    }
    else {
        mesg = rb_str_new2(err);
    }
    rb_call_super(1, &mesg);
    rb_iv_set(self, "errno", error);
    return self;
}