# Spelunking in Ruby's Source

**URL:** <https://www.ruby-forum.com/t/spelunking-in-rubys-source/64875>\
**Category:** Ruby\
**Created:** [August 15, 2006, 2:19pm UTC](https://www.ruby-forum.com/t/spelunking-in-rubys-source/64875 "2006-08-15T14:19:59Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [August 15, 2006, 2:19pm UTC](https://www.ruby-forum.com/t/spelunking-in-rubys-source/64875/1 "2006-08-15T14:19:59Z")

</div>

Ruby for Rails makes an interesting claim that object\_id(), send(),  
and respond\_to?() are defined on Kernel. I didn’t expect this, so I  
went into the source to verify and it does seem to be true in Ruby  
1.8.x. These seem to be the relevant lines of eval.c:

```
 rb_define_method(rb_mKernel, "respond_to?", obj_respond_to, -1);

 rb_define_method(rb_mKernel, "send", rb_f_send, -1);
 rb_define_method(rb_mKernel, " __send__", rb_f_send, -1);

```

and gc.c:

```
 rb_define_method(rb_mKernel, " __id__", rb_obj_id, 0);
 rb_define_method(rb_mKernel, "object_id", rb_obj_id, 0);

```

My first question is, why are these Kernel methods, instead of  
methods on Object?

I thought Kernel was for methods like puts() that we wanted to have  
globally available but that weren’t necessarily inherent to Object.  
Clearly my understanding is flawed, so would someone please explain  
how it is decided if a method belongs in Object or Kernel?

Fast forwarding to HEAD, this seems to have changed in Ruby 1.9.  
Here are the now relevant lines of eval.c:

```
 rb_define_method(rb_cBasicObject, "respond_to?", obj_respond_to,

```

-1);

```
 rb_define_method(rb_cBasicObject, "send", rb_f_send, -1);
 rb_define_method(rb_cBasicObject, " __send__", rb_f_send, -1);

```

and again for gc.c:

```
 rb_define_method(rb_cBasicObject, " __id__", rb_obj_id, 0);
 rb_define_method(rb_cBasicObject, "object_id", rb_obj_id, 0);

```

Am I reading this right in that the methods have been moved to  
BasicObject in Ruby 1.9?

An unrelated curiosity: while browsing the source I saw these likes  
in eval.c:

```
 rb_define_method(rb_cBasicObject, "send", rb_f_send, -1);
 rb_define_method(rb_cBasicObject, " __send__", rb_f_send, -1);
 rb_define_method(rb_cBasicObject, "__send", rb_f_send, -1);
 rb_define_method(rb_cBasicObject, "funcall", rb_f_funcall, -1);
 rb_define_method(rb_cBasicObject, "__send!", rb_f_funcall, -1);

```

Does that last one mean Matz is cracking under the pressure? 😉

James Edward G. II

---

<div class="post-metadata">

**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [August 16, 2006, 6:19am UTC](https://www.ruby-forum.com/t/spelunking-in-rubys-source/64875/2 "2006-08-16T06:19:31Z")

</div>

On Aug 14, 2006, at 12:53 PM, James Edward G. II wrote:

> I thought Kernel was for methods like puts() that we wanted to have  
> globally available but that weren’t necessarily inherent to  
> Object. Clearly my understanding is flawed, so would someone  
> please explain how it is decided if a method belongs in Object or  
> Kernel?

Everything (almost) belongs in Kernel

% irb  
irb(main):001:0\> obj = Object.new  
=\> #Object:0x35477c  
irb(main):002:0\> obj.methods.map { |x| obj.method(x).inspect }.grep(/  
Kernel/).size  
=\> 40  
irb(main):003:0\> obj.methods.size  
=\> 40

I believe the purpose of BasicObject in 1.9 is to be able to say

class O \< BasicObject # I want BlankSlate without all the extra work  
of undef\_method  
end

I don’t know anything about matz. cracking under the pressure