On Sat, Sep 29, 2007 at 03:39:05AM +0900, Nobuyoshi Nakada wrote:
> >   VALUE rb_cFoo = rb_define_class("Foo", rb_cObject);
> >   rb_undef_alloc_func(rb_cFoo);
> 
> It makes impossible to create any instances at all.
> 
>   rb_undef_method(rb_singleton_class(rb_cFoo), "new");

Instances can still be created with Data_Wrap_Struct.  But maybe that's
not what the OP intended.  I saw the word "extension" and made an
assumption.

Paul