json (1.8.3) and rubyracer gems aren’t compatible with ruby 2.4.0

PS: This is moot anyway because it looks like Rails 4.2 doesn’t fully support Ruby 2.4.0 yet

Ran into this problem trying to upgrade a Rails app to use the new version of Ruby.

make "DESTDIR="
compiling generator.c
generator.c:861:25: error: use of undeclared identifier 'rb_cFixnum'
} else if (klass == rb_cFixnum) {
generator.c:863:25: error: use of undeclared identifier 'rb_cBignum'
} else if (klass == rb_cBignum) {
generator.c:975:5: warning: division by zero is undefined [-Wdivision-by-zero]
rb_scan_args(argc, argv, "01", &opts);


Turns out this is because of Bignum/Fixnum integration that rolled out in ruby 2.4.0

after that I hit another fugly stack trace caused because I hadn’t upgraded therubyracer gem to 0.12.3

I had to include the gems and specific versions in my gemfile

gem 'json', '~> 1.8.6'
gem 'therubyracer', '~> 0.12.3'

then run

bundle update json

Unfortunately, as I mentioned above, I was unable to run Rails 4.2.7 anyway, because it looks like it hasn’t been fully prepped to incorporate Ruby 2.4.0’s integer changes.

Suddenly failing `rvm install`command on os x 10.11 (El Capitan)

This actually started with a strange error, when I went to fire up a rails server in an app I’d been working on the night before.

Unable to load application: LoadError: dlopen(/Users/xxx/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-darwin14/readline.bundle, 9): Library not loaded: /usr/local/opt/readline/lib/libreadline.6.dylib

Like I mentioned, I’d fired up this app less than 24 hours prior, so this was very strange to me. Some quick googling around suggested that I try to reinstall my ruby version so I ran the command

rvm reinstall 2.3.0

Well that errored out with another strange error

ruby-2.3.0 - #configuring...........................................................
ruby-2.3.0 - #post-configuration.
ruby-2.3.0 - #compiling...........
Error running '__rvm_make -j 1',
showing last 15 lines of /Users/xxx/.rvm/log/1476345601_ruby-2.3.0/make.log
compiling enc/trans/newline.c
compiling ./missing/explicit_bzero.c
compiling ./missing/setproctitle.c
compiling dmyenc.c
linking miniruby
dyld: lazy symbol binding failed: Symbol not found: _clock_gettime
  Referenced from: /Users/xxx/.rvm/src/ruby-2.3.0/./miniruby (which was built for Mac OS X 10.12)
  Expected in: /usr/lib/libSystem.B.dylib
dyld: Symbol not found: _clock_gettime
  Referenced from: /Users/xxx/.rvm/src/ruby-2.3.0/./miniruby (which was built for Mac OS X 10.12)
  Expected in: /usr/lib/libSystem.B.dylib
make: *** [.rbconfig.time] Trace/BPT trap: 5
++ return 2
There has been an error while running make. Halting the installation.

You might notice the “(which was built for Mac OS X 10.12)
which is a bit of a hint at what the problem is.

Because the last line hints the problem is with make, I decided to reinstall make with brew and it dumped the solution to the problem in my lap

brew install make
Warning: You have Xcode 8 installed without the CLT;
this causes certain builds to fail on OS X El Capitan (10.11).
Please install the CLT via:
sudo xcode-select --install

Basically I’d upgraded my Xcode version without installing command line tools. Once I ran this command, my rvm reinstall went fine and my readline problems went away.

Merry Christmas Rubyists … Ruby 2.3.0 is here!

Ruby 2.3.0 has been released

Significant new features include &., Array#dig, Hash#dig and the very user-friendly “did you mean” when you get the name of a gem wrong when bundling your gems.

Of course there are performance improvements, but this blog post brilliantly walks through all the new cool stuff in Ruby 2.3.0 … bookmark away!

Also worthy to note that Heroku currently supports Ruby 2.3.0 but is running a preview version, I’d expect an update to the final release before the end of the year


Is Ruby pass-by-reference or pass-by-value?

I was confused by Ruby’s variable assignment paradigm for a while, and even after reading this Stackoverflow thread and checking out out other threads about the same thing I was no closer to understanding it clearly. And in the words of the great Albert Einstein …

“if you can’t explain it simply you don’t understand it well enough”

I eventually figured it out by reading page 53-54 of what I think is the best Ruby book on the market right now, turns out its actually pretty simple to understand.

Ruby ALWAYS passes references to objects on assignment, BUT some types in ruby are stored in variables as immediate values because they are immutable.

For example (you can try these out in irb)

me = we = “we”
me #=> “we”
we #=> “we”
me #=> “WE”
we #=> “WE”

me = we = [1, 2, 3]
we #=> [1, 2, 3]
me #=> [1, 2, 3]
we << 4
we #=> [1, 2, 3, 4]
me #=> [1, 2, 3, 4]

Ruby does this for all its types, but with primitives that are immutable, namely integers, symbols, nil, and the booleans true and false, it takes a shortcut and actually stores the value IN the variable itself, because … what are you going to do? change an immutable object? 🙂

Pretty clever when you think about it IMO.

I upgraded to Ruby 2.1.0 and all I got was this lousy T-shirt …

Ruby 2.1.0 was released about 2 weeks ago, and after seeing a notable speed performance improvement with my Rails app when going from 1.9.3 to 2.0.0 I was excited to see if the same would happen with Ruby 2.1.0.

I quickly ran another set of very casual tests, mainly running test suites and noting startup times of rails commands and rake tasks at the command line. What I saw was a 20% improvement in those tasks. Nothing to sneeze at …

Excited, I rushed to upgrade my tiny Rails app to ruby 2.1.0 and after doing it I tracked the difference in New Relic

This was my result (deployment happened about 18:00 on December 25th, app is setup to run with one puma worker and 8-16 threads proxied to nginx)

New Relic graph after upgrading to Ruby 2.1.0 (18:00 on the graph)As you can see, there wasn’t much of an improvement in performance at all. In fact here is the graph after a full day of running in the wild.

New Relic graph of my app after a full day of running with Ruby 2.1.0


So while you might get better startup times on Rails tasks, you probably won’t see too much of a speed boost on your servers.

Improved GC

What I found interesting, though, is the improved garbage collection. The brown part of the graph (GC execution) almost completely disappears in ruby 2.1.0. And its no wonder, a lot of work went into improving Garbage collection in ruby 2.1.0

The garbage collector in Ruby 2.1 implements a form of generational garbage collection, with Ruby calling their implementation RGenGC (Restricted Generational Garbage Collection).  This replaces the “Mark & Sweep” implementation used in previous versions of Ruby

Using RGenGC provides high compatibility with existing extensions while still bringing performance improvements.  Popular objects Array, String, Hash, Object, and Numeric are Write-Barrier protected, thus able to take advantage of the RGenGC system

The moral of the story? Ruby 2.1.0 has a small performance boost over Ruby 2.0 and upgrading to it should give you a bit of a boost with your Rails app, more if its a pretty big app with non-trivial time spent doing GC.

PS: Brian Hempel has created an awesome site that benchmarks ruby versions using Rails. His results are in line with what I found
PS2: Sorry there wasn’t actually a T-shirt, I just liked the title

tracking down *exactly* where a Ruby object method is defined

Ever spent way longer than you would have liked trying to find out exactly where a particular Ruby object method is defined, especially in something like Rails where a method could have been included from a plugin, gem, helper, or otherwise metaprogrammed in?

Well with Ruby 1.9.3 … you can now do this


and get this back

=> [“/Users/xxx/.rvm/gems/ruby-1.9.3-p362/gems/state_machine-1.1.2/lib/state_machine/machine.rb”, 752]

Blew my mind, and I’ve been writing Ruby for almost 6 years now.

Ruby 2.0.0 is looking like its going to be substantially faster than Ruby 1.9.3

In very unscientific tests Ruby 2.0 is 60-70% faster than 1.9.3.
Very promising.

PS: I couldn’t get my test suite to run in Ruby 2.0.0 but I managed to run the very simple
“time bundle exec rake environment” test

The average was
– 7.74s for ruby 2.0.0
– 11.8s for ruby 1.9.3-p368, a 65% speed improvment, right in line with the results from the gist
– 17.07s for rubinius 2.0.0 (1.9 variant) … yeah thats slow

Unit Testing and Mock Objects

Recently, I’ve been working hard to plug one of the biggest holes in my game … testing. I stumbled across this article, which helped make a lot of things clear for me, with respect to mocking and its relation to Unit testing.

This is partially due to the fact that most geeks don’t actually know what a unit test is. They think that testing the methods of a specific class constitutes a unit test, but that’s only part of the story. A unit test test is when you test the methods of a specific class in isolation, and the difference is critical. You know how some people call us “computer scientists”. Yeah, well this is the science part.

If you’re not doing this, you are not unit testing. That’s not meant to deride what you’re doing. I mean that as a literal statement of fact. Anyone, for example, who is using the built in Rails “unit” testing framework with fixtures (or FactoryGirl fixtures) is guilty of this. No test that relies on a separate class, or API, or interfaces with a database in any way is a unit test. It is an integration test (some people call them functional test), and when something goes wrong it is just a matter of time before it misleads you.

Enjoy the article – The Thing about Mock Objects

How to get Ruby Native gems to install on your windows machine

The bane of any ruby/rails developer on a windows box (apart from piddling performance) is seeing the dreaded …
‘gem install error – ‘cl’ is not recognized as an internal or external command’

No more!
Devkit, a tool used by the folks who create the Windows Ruby Installer of each version of ruby helps you with (most) gems that need to be built natively.
Muchos Gracias to them for graciously providing it to us.

From the books: Exceptions to Ruby’s standard variable assignment by reference behavior

The un-reference: immediate values
Some objects in Ruby are stored in variables as immediate values. These include integers, symbols (which look like :this), and the special objects true, false and nil. When you assign one of these values to a variable (x = 1), the variable holds the value itself, rather than a reference to it

— From page 54 of The Well Grounded Rubyist by Robert Black

Filed under Things I did not know about Ruby 😀


Fixing the libxml-ruby gem error: uninitialized constant XML (NameError)

I found the highly recommended libxml-ruby gem but was having a lot of trouble getting my sample code below to work

require 'libxml'
doc = XML::Document.file('http://search.twitter.com/search.atom?q=obama')
root = doc.root
puts "Root element name: #{root.name}"

I kept getting this error

uninitialized constant XML (NameError) Continue reading

php’s print_r equivalent in ruby on rails

I was going through my google analytics logs today and I noticed that a lot of folks were coming to my site on Google searches for stuff like ‘print_r + ruby on rails‘.

So I figured I’d write a blog post about it, because I’ve had the same problem.

What you’re looking for is ‘inspect’.

If you have an array, hash or object that you want to take a quick-and-dirty look at just type in




or if you’re in rails just do …

render :text => posts.inspect and return false

and you’ll get an output of the contents of said array, hash or object.

Here is a screen capture of a quick irb session to show you how it works.

print_r equivalent in ruby on rails

I hope this helps.

Gotcha in Ruby for PHP Developers with multiple assignments of array to variables

The more I work with Ruby and Ruby on Rails, the more I begin to understand (though not necessarily agree with) a lot of the vitriol that has been aimed at PHP over the years by developers using other more rigorous languages.

A few weeks back I ran into this little speed bump while working with Ruby on Rails, where I was  trying to do a multiple assignment like this

x = y = z = []

Most seasoned Rubyists will be waving their arms around and yelling “NOOOOOO!!!”
But coming from a PHP background this seemed perfectly okay to me.

Continue reading