From: Mark Moseley <mark@...>
Date: 2009-09-05T00:50:47+09:00
Subject: Re: Bytecode in Ruby 1.9

Wim Vander schelden wrote:
> Hi,
> 
> I've looked all over and I can't seem to find any complete documentation
> about the YARV bytecode. Is there a reference or spec somewhere?
Not that I know of. What I've learned came from debugging vm_exec().

> 
> On instruction I find nothing about is the trace instruction. Does
> anyone know how it works?
Sure. Whether trace instructions are included or not into the bytecode 
is a compile-time switch. It's on by default in all 1.9.x releases so 
you don't need to worry about that.

To use them, you need to install a hook function via 
rb_add_event_hook(). Then the hook will get the trace events when they 
occur.

The ruby-debug-base19 gem uses this extensively; you might want to take 
a look at it.

Mark

> 
> Kind regards,
> 
> Wim

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