Intro to the Ruby VM - Speaker Deck

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INTRO TO THE RUBY VM @ASHLEYNELLIS Ashley Ellis

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WHAT THE HECK’S A VM?

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“A VIRTUAL MACHINE (VM) IS AN OPERATING SYSTEM (OS) OR APPLICATION ENVIRONMENT THAT IS INSTALLED ON SOFTWARE WHICH IMITATES DEDICATED HARDWARE.” Source: http://searchservervirtualization.techtarget.com/deﬁnition/virtual-machine

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RUBY CODE -> BYTECODE

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YARV YET ANOTHER RUBY VIRTUAL MACHINE

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PREPARING YOUR CODE FOR YARV

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TOKENIZING: GOES THROUGH EACH CHARACTER AND CONVERTS THEM TO A SERIES OF TOKENS THAT RUBY UNDERSTANDS 10 -> tInteger

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PARSING: TOKENS ARE GROUPED INTO SENTENCES AND PHRASES THAT MAKE SENSE TO RUBY

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‣ SINCE RUBY 1.9, AFTER YOUR RUBY CODE IS PARSED AND TOKENIZED IT’S COMPILED TO BYTE CODE USING YARV. ‣ THIS IS VERY SIMILAR TO HOW JAVA WORKS, THE JVM COMPILES IT TO JAVA BYTE CODE. ‣ BEFORE 1.9 RUBY WAS BEING INTERPRETED TO C AND THEN THE C COMPILES TO MACHINE CODE.

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COMPILER VS INTERPRETER

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COMPILER: FROM SOURCE CODE TO MACHINE LEVEL CODE ONCE (UNTIL THE PROGRAM IS CHANGED) INTERPRETER: DOES SOME CONVERSION WORK EVERY TIME A STATEMENT OR FUNCTION IS EXECUTED

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RUBY IS STILL CLASSIFIED AS AN INTERPRETED LANGUAGE

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INTERMEDIATE REPRESENTATION COMBINES COMPILING AND INTERPRETING

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PRE 1.9- *TRAVERSES* ABSTRACT SYNTAX TREE (AST) (KIND OF LIKE THE DOM) NOW - YARV COMPILES THAT AST TO YARV BYTECODE AND THEN RUNS IT. https://www.igvita.com/2008/12/11/ruby-ast-for-fun-and-proﬁt/

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Shaughnessy, P. (2013). How Ruby Executes Your Code. In Ruby under a microscope: An illustrated guide to Ruby internals (1st ed., p. 360). No Starch Press.

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Shaughnessy, P. (2013). How Ruby Executes Your Code. In Ruby under a microscope: An illustrated guide to Ruby internals (1st ed., p. 360). No Starch Press.

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SOO…WHY SHOULD I CARE?

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‣ DEBUGGING WAT MOMENTS ‣ PERFORMANCE OPTIMIZATION ‣ METAPROGRAMMING ‣ KNOWING WHEN TO USE WHAT LANGUAGE

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RESOURCES FOR OTHER LANGUAGES ▸ Python ▸ Also an Intermediate Language (Compiled and Interpreted) ▸ dis function to see CPython byte code ▸ https://docs.python.org/2/ library/dis.html ▸ Javascript ▸ Interpreted with optional JIT (just- in-time) compilation support. ▸ All modern day browsers use the JIT ▸ Capstone.js or similar tools can be used to disassemble code to byte code ▸ http://alexaltea.github.io/ capstone.js/

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SOURCES ‣ http://searchservervirtualization.techtarget.com/deﬁnition/virtual- machine ‣ Shaughnessy, P. (2013). Ruby under a microscope: An illustrated guide to Ruby internals (1st ed., p. 360). No Starch Press. ‣ Cooper, P. (2011, August 5). Using Ripper to See How Ruby Is Parsing Your Code. Retrieved December 2, 2015, from http:// www.rubyinside.com/using-ripper-to-see-how-ruby-is-parsing-your- code-5270.html ‣ https://www.igvita.com/2008/12/11/ruby-ast-for-fun-and-proﬁt/