# Bytecode in Ruby 1.9 **URL:** \ **Category:** ruby-talk\ **Created:** [4 September 2009 14:58 UTC](https://rubytalk.org/t/bytecode-in-ruby-1-9/55246 "2009-09-04T14:58:58Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Wim\_Vander\_schelden](https://avatars.discourse-cdn.com/v4/letter/w/ed655f/32.png) [@Wim\_Vander\_schelden](https://rubytalk.org/u/Wim_Vander_schelden)\ **Post date:** [4 September 2009 14:58 UTC](https://rubytalk.org/t/bytecode-in-ruby-1-9/55246/1 "2009-09-04T14:58:58Z")
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? On instruction I find nothing about is the trace instruction. Does anyone know how it works? Kind regards, Wim > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Mark\_Moseley](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@Mark\_Moseley](https://rubytalk.org/u/Mark_Moseley)\ **Post date:** [4 September 2009 15:50 UTC](https://rubytalk.org/t/bytecode-in-ruby-1-9/55246/2 "2009-09-04T15:50:47Z")
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 > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).