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Building Ruby

Dependencies

  1. Install the prerequisite dependencies for building the CRuby interpreter:

    • C compiler

    For RubyGems, you will also need:

    If you want to build from the git repository, you will also need:

    • autoconf - 2.67 or later
    • gperf - 3.1 or later
      • Usually unneeded; only if you edit some source files using gperf
    • ruby - 3.0 or later
      • We can upgrade this version to system ruby version of the latest Ubuntu LTS.

  2. Install optional, recommended dependencies:

    • libffi (to build fiddle)
    • gmp (if you wish to accelerate Bignum operations)
    • rustc - 1.58.0 or later, if you wish to build YJIT.

    If you want to link the libraries (e.g., gmp) installed into other than the OS default place, typically using Homebrew on macOS, pass the --with-opt-dir (or --with-gmp-dir for gmp) option to configure.

    configure --with-opt-dir=$(brew --prefix gmp):$(brew --prefix jemalloc)

    As for the libraries needed for particular extensions only and not for Ruby (openssl, readline, libyaml, zlib), you can add --with-EXTLIB-dir options to the command line or to CONFIGURE_ARGS environment variable. The command line options will be embedded in rbconfig.rb, while the latter environment variable is not embedded and is only used when building the extension libraries.

    export CONFIGURE_ARGS=""
for ext in openssl readline libyaml zlib; do
  CONFIGURE_ARGS="${CONFIGURE_ARGS} --with-$ext-dir=$(brew --prefix $ext)"
done

Quick start guide

  1. Download ruby source code:

    Select one of the below.

    1. Build from the tarball:

      Download the latest tarball from Download Ruby page and extract it. Example for Ruby 3.0.2:

      tar -xzf ruby-3.0.2.tar.gz
cd ruby-3.0.2

    2. Build from the git repository:

      Checkout the CRuby source code:

      git clone https://github.com/ruby/ruby.git
cd ruby

      Run the GNU Autoconf script (which generates the configure script):

      ./autogen.sh

  2. Create a build directory inside the repository directory:

    mkdir build && cd build

    While it's not necessary to build in a dedicated directory like this, it's good practice to do so.

  3. We'll eventually install our new Ruby in ~/.rubies/ruby-master, so we'll create that directory:

    mkdir ~/.rubies

  4. Run the configure script (which generates the Makefile):

    ../configure --prefix="${HOME}/.rubies/ruby-master"
    • Also -C (or --config-cache) would reduce time to configure from the next time.

  5. Build Ruby:

    make

  6. Run tests to confirm your build succeeded.

  7. Install our newly-compiled Ruby into ~/.rubies/ruby-master:

    make install
    • If you need to run make install with sudo and want to avoid document generation with different permissions, you can use make SUDO=sudo install.

  8. You can then try your new Ruby out, for example:

    ~/.rubies/ruby-master/bin/ruby -e "puts 'Hello, World!'"

By the end, your repo will look like this:

ruby
├── autogen.sh      # Pre-existing Autoconf script, used in step 1
├── configure       # Generated in step 1, which generates the `Makefile` in step 4
├── build           # Created in step 2 and populated in step 4
│   ├── GNUmakefile # Generated by `../configure`
│   ├── Makefile    # Generated by `../configure`
│   ├── object.o    # Compiled object file, built my `make`
│   └── ... other compiled `.o` object files
│
│ # Other interesting files:
├── include
│   └── ruby.h      # The main public header
├── internal
│   ├── object.h
│   └── ... other header files used by the `.c` files in the repo root.
├── lib
│   └── # Default gems, like `bundler`, `erb`, `set`, `yaml`, etc.
├── spec
│   └── # A mirror of the Ruby specification from github.com/ruby/spec
├── test
│   ├── ruby
│   └── ...
├── object.c
└── ... other `.c` files

Unexplainable Build Errors

If you are having unexplainable build errors, after saving all your work, try running git clean -xfd in the source root to remove all git ignored local files. If you are working from a source directory that's been updated several times, you may have temporary build artifacts from previous releases which can cause build failures.

Building on Windows

The documentation for building on Windows can be found in the separated file.

More details

If you're interested in continuing development on Ruby, here are more details about Ruby's build to help out.

Running make scripts in parallel

In GNU make1 and BSD make implementations, to run a specific make script in parallel, pass the flag -j<number of processes>. For instance, to run tests on 8 processes, use:

make test-all -j8

We can also set MAKEFLAGS to run all make commands in parallel.

Having the right --jobs flag will ensure all processors are utilized when building software projects. To do this effectively, you can set MAKEFLAGS in your shell configuration/profile:

# On macOS with Fish shell:
export MAKEFLAGS="--jobs "(sysctl -n hw.ncpu)

# On macOS with Bash/ZSH shell:
export MAKEFLAGS="--jobs $(sysctl -n hw.ncpu)"

# On Linux with Fish shell:
export MAKEFLAGS="--jobs "(nproc)

# On Linux with Bash/ZSH shell:
export MAKEFLAGS="--jobs $(nproc)"

Miniruby vs Ruby

Miniruby is a version of Ruby which has no external dependencies and lacks certain features. It can be useful in Ruby development because it allows for faster build times. Miniruby is built before Ruby. A functional Miniruby is required to build Ruby. To build Miniruby:

make miniruby

Debugging

You can use either lldb or gdb for debugging. Before debugging, you need to create a test.rb with the Ruby script you'd like to run. You can use the following make targets:

  • make run: Runs test.rb using Miniruby
  • make lldb: Runs test.rb using Miniruby in lldb
  • make gdb: Runs test.rb using Miniruby in gdb
  • make runruby: Runs test.rb using Ruby
  • make lldb-ruby: Runs test.rb using Ruby in lldb
  • make gdb-ruby: Runs test.rb using Ruby in gdb

Compiling for Debugging

You should configure Ruby without optimization and other flags that may interfere with debugging:

./configure --enable-debug-env optflags="-O0 -fno-omit-frame-pointer"

Building with Address Sanitizer

Using the address sanitizer (ASAN) is a great way to detect memory issues. It can detect memory safety issues in Ruby itself, and also in any C extensions compiled with and loaded into a Ruby compiled with ASAN.

./autogen.sh
mkdir build && cd build
../configure CC=clang-18 cflags="-fsanitize=address -fno-omit-frame-pointer -DUSE_MN_THREADS=0" # and any other options you might like
make

The compiled Ruby will now automatically crash with a report and a backtrace if ASAN detects a memory safety issue. To run Ruby's test suite under ASAN, issue the following command. Note that this will take quite a long time (over two hours on my laptop); the RUBY_TEST_TIMEOUT_SCALE and SYNTAX_SUGEST_TIMEOUT variables are required to make sure tests don't spuriously fail with timeouts when in fact they're just slow.

RUBY_TEST_TIMEOUT_SCALE=5 SYNTAX_SUGGEST_TIMEOUT=600 make check

Please note, however, the following caveats!

  • ASAN will not work properly on any currently released version of Ruby; the necessary support is currently only present on Ruby's master branch (and the whole test suite passes only as of commit Revision 9d0a5148).
  • Due to Bug #20243, Clang generates code for threadlocal variables which doesn't work with M:N threading. Thus, it's necessary to disable M:N threading support at build time for now (with the -DUSE_MN_THREADS=0 configure argument).
  • ASAN will only work when using Clang version 18 or later - it requires llvm/llvm-project#75290 related to multithreaded fork.
  • ASAN has only been tested so far with Clang on Linux. It may or may not work with other compilers or on other platforms - please file an issue on Ruby Issue Tracking System if you run into problems with such configurations (or, to report that they actually work properly!)
  • In particular, although I have not yet tried it, I have reason to believe ASAN will not work properly on macOS yet - the fix for the multithreaded fork issue was actually reverted for macOS (see llvm/llvm-project#75659). Please open an issue on Ruby Issue Tracking System if this is a problem for you.

How to measure coverage of C and Ruby code

You need to be able to use gcc (gcov) and lcov visualizer.

./autogen.sh
./configure --enable-gcov
make
make update-coverage
rm -f test-coverage.dat
make test-all COVERAGE=true
make lcov
open lcov-out/index.html

If you need only C code coverage, you can remove COVERAGE=true from the above process. You can also use gcov command directly to get per-file coverage.

If you need only Ruby code coverage, you can remove --enable-gcov. Note that test-coverage.dat accumulates all runs of make test-all. Make sure that you remove the file if you want to measure one test run.

You can see the coverage result of CI: https://rubyci.org/coverage

Footnotes

  1. CAUTION: GNU make 3 is missing some features for parallel execution, we recommend to upgrade to GNU make 4 or later. ↩