From: "Suraj N. Kurapati" <sunaku@...>
Date: 2008-04-18T10:57:14+09:00
Subject: Re: ruby_init() and C call stack in Ruby 1.9

Paul Brannan wrote:
> On Fri, Apr 18, 2008 at 12:22:52AM +0900, Suraj N. Kurapati wrote:
>> I really wish Ruby's C API was like OpenGL: a state machine.
>> It doesn't matter from what stack position you query/modify the
>> machine  state.
> 
> This would perhaps allow you to run multiple interpreters in the same
> process,

I don't think this would allow multiple interpreters because there
is still only one global instance of the state machine (like in OpenGL).

Instead, multiple interpreters would be possible if ruby_init()
returned a token (which identifies a particular instance of the
interpreter) and you used the token whenever calling Ruby's C API.

Alternatively, you could attach/detach a particular Ruby instance
to/from the global state machine.  This is similar to pushing and
popping ModelView matrices in OpenGL and operating on one matrix at
a time.

> but it would not solve the stack initialization problem.  Ruby
> needs to know the size and location of the stack so the GC can mark
> objects on the stack.

If ruby_init() dynamically allocated its own stack region, then it
would know both the size and location of the stack.

As a result, you could use Ruby's C API from any C call stack
without causing trouble for Ruby (since Ruby has its own private
stack which is hidden and isolated from the user).