Rubinius - Tales from the trenches @ Railsclub.ru 2012

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Rubinius Tales from the trenches

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Dirkjan Bussink @dbussink

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Huh?

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Class.stub!(:new).and_return(MyClass)

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Beyond imagination

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class Foo class << self class << self def foo; end end end end class Bar < Foo; end p Bar.singleton_class.foo

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Liskov Substitution Principle

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class SomeList < Array def push(value) value = Proxy.new(value) if value.is_a?(String) ... end end alias_method :<<, :push end Unmarshal uses Array#<<

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StackError

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class PropertySet < Array alias_method :superclass_slice, :[]= private :superclass_slice def []=(name, property) self << property end def <<(property) found = named?(property.name) add_property(property) if found superclass_slice(index(property), property) else super end end end WUT? Ugh Oh, let’s change the meaning!

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class PropertySet def []=(name, property) add_property(property) end def <<(property) add_property(property) end def add_property(property) clear_cache @order << property unless @order.include?(@property) @properties[property.name] = property end end

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IDIOT

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GCC...

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vm/builtin/regexp.cpp:312: warning: control may reach end of non-void function

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GCC is fucking stupid. Avoid inane gcc type punning warning Work around GCC's broken strict aliasing checks. gcc 4.2.1 on freebsd 9 wants a newline at the end Make the gcc gods happy Make the stupid compiler gods happy Appease GCC 4.3

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Ruby is weird

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class MyClass def to_ary puts "we're here" [1] end end def my_method arg yield arg end my_method(MyClass.new) do |*arg| p arg end we're here [#] we're here [1] we're here [[1]] [#] A B C D Call to_ary and ignore

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can't define singleton method "method" for Float obj = 2.0 def obj.method puts "method on float instance" end obj.method No singleton methods on Numeric

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class Numeric def singleton_method_added(name) end end obj = 2.0 def obj.method puts "method on float instance" end obj.method method on float instance Singleton method on a Numeric!

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3 4 5 6 Becomes true on first condition, false on second 10.times do |i| if (i == 3) .. (i == 6) puts i end end

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Ruby’s C-API

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There is no C-API just internals of MRI that people use

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VALUE rb_data_object_alloc(VALUE klass, void *datap, RUBY_DATA_FUNC dmark, RUBY_DATA_FUNC dfree) { NEWOBJ(data, struct RData); if (klass) Check_Type(klass, T_CLASS); OBJSETUP(data, klass, T_DATA); data->data = datap; data->dfree = dfree; data->dmark = dmark; return (VALUE)data; } MRI internals

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NotImplementedError: method `class' called on terminated object (0xXXXXXXXX) Inspect object created with rb_data_object_alloc

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GC can be hard

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C Stack Object* Object* Heap 1 Object Object Heap 2 Object Object GC moves objects

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Old Young String Array Object String String Hash

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Concurrency is tricky

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Out of order execution

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a = 0 b = 0 c = 0 d = 0 Core 1 Core 2 a = 1 c = 1 b = 2 d = 2 Statements can be executed in different order

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addr = Address.new addr.street = "Somestreet" addr.number = 1 shared_addr = addr shared_addr => nil shared_addr => # shared_addr => # shared_addr => # shared_addr => # shared_addr = addr executed before other assignments

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addr = Address.new addr.street = "Somestreet" addr.number = 1 Rubinius.memory_barrier shared_addr = addr