I’ve been wanting to take a look at Ruby’s core for sometime. I will try do do some coding with Ruby’s source from this week and write some blog posts along.

This week, I want to setup the development enviroment, I will test on both Mac and Linux(Ubuntu) to see if there is any difference.

Compile ruby from source

First, pull the source from github(I will use 2.5.1 version)

mkdir workspace
cd workspace
git clone --depth 1 --branch v2_5_1 git@github.com:ruby/ruby.git ruby_source
cd ruby_source

On Mac, we will need autoconf, openssl(as the default tls library of Mac is not compatible with Ruby), and readline to compile Ruby from source.

brew install autoconf openssl readline

Run autoconf inside ruby_source directory

mkdir build
cd build
../configure --prefix=$PWD/install
             --with-openssl-dir="$(brew --prefix openssl)" 
             --with-readline-dir="$(brew --prefix readline)" 
make install

On Ubuntu, we will need to install the following libraries

apt-get install -y build-essentials libssl-dev libreadline-dev zlib1g-dev bison ruby

Funny thing is we will need a working Ruby in order to compile Ruby from source; therefore, the command above also installs ruby from apt. After that, we compile and install same as on Mac.

If there is no problem, we will have ruby binary installed to workspace/ruby/build/install directory.


During compilation process, there is a mini version of Ruby called miniruby, this one will be use to compile the full version of Ruby. Because it’s a minified version, compiling of miniruby is much faster than the full version. We can use it to test our changes in Ruby’s source and have a faster feedback. In fact, Ruby the command make run is use for this purpose.

In order to invoke make run we need to create a test.rb file in ruby source folder, for example

cd ruby_source
echo "puts 'hello world'" > test.rb
cd build
make run

Another useful command is make runruby, this one also run test.rb but with full version of ruby.

So the workflow when making change Ruby would be like

  1. Making some changes
  2. Wring some code to test new feature in test.rb
  3. Running it with make run

Debugging using gdb(Linux only)

One of the important thing when working with C code is debugging(or any other language for that matter), on Linux it would be gdb. To debug using gdb we can use make gdb. This will invoke miniruby, run test.rb and exit(if there is no error). So for example

echo "put 'Hello world'" > test.rb
cd build
make gdb

Debugging using lldb(Mac)

It is very troublesome to setup gdb on Mac, we can use lldb which is provided together with clang and llvm’s friends on Mac. Ruby also provide the command make lldb with same function as make gdb. It will stop right before execution of the script, we can inspect code, set breakpoint from there. For example

echo "put 'Hello world'" > test.rb
cd build
make lldb

So, that’s all for this time. Next week, I will try to create some simple method with Ruby and do some simple debug with gdb/lldb.