ruby/doc/contributing/building_ruby.md

# Building Ruby

## Dependencies

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

    * C compiler

    For RubyGems, you will also need:

    * [OpenSSL] 1.1.x or 3.0.x / [LibreSSL]
    * [libyaml] 0.1.7 or later
    * [zlib]

    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.
    * git - 2.32 or later
        * Anterior versions may work; 2.32 or later will prevent build
          errors in case your system `.gitconfig` uses `$HOME` paths.

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](rdoc-ref:RubyVM::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`.

    ```sh
    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.

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

[OpenSSL]: https://www.openssl.org
[LibreSSL]: https://www.libressl.org
[libyaml]: https://github.com/yaml/libyaml/
[zlib]: https://www.zlib.net
[autoconf]: https://www.gnu.org/software/autoconf/
[gperf]: https://www.gnu.org/software/gperf/
[libffi]: https://sourceware.org/libffi/
[gmp]: https://gmplib.org
[rustc]: https://www.rust-lang.org

## 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:

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

    2. Build from the git repository:

        Checkout the CRuby source code:

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

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

        ```sh
        ./autogen.sh
        ```

2. Create a `build` directory inside the repository directory:

    ```sh
    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:

    ```sh
    mkdir ~/.rubies
    ```

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

    ```sh
    ../configure --prefix="${HOME}/.rubies/ruby-master"
    ```

    - Also `-C` (or `--config-cache`) would reduce time to configure from the
      next time.

5. Build Ruby:

    ```sh
    make
    ```

6. [Run tests](testing_ruby.md) to confirm your build succeeded.

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

    ```sh
    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:

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

By the end, your repo will look like this:

```text
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
```

[Download Ruby]: https://www.ruby-lang.org/en/downloads/

### 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](../windows.md).

## 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 make[^caution-gmake-3] 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:

```sh
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:

```sh
# 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)"
```

[^caution-gmake-3]: **CAUTION**: GNU make 3 is missing some features for parallel execution, we
recommend to upgrade to GNU make 4 or later.

### 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:

```sh
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:

```sh
./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.

```sh
./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.

```sh
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.

[Revision 9d0a5148]: https://bugs.ruby-lang.org/projects/ruby-master/repository/git/revisions/9d0a5148ae062a0481a4a18fbeb9cfd01dc10428
[Bug #20243]: https://bugs.ruby-lang.org/issues/20243
[llvm/llvm-project#75290]: https://github.com/llvm/llvm-project/pull/75290
[llvm/llvm-project#75659]: https://github.com/llvm/llvm-project/pull/75659#issuecomment-1861584777
[Ruby Issue Tracking System]: https://bugs.ruby-lang.org

## How to measure coverage of C and Ruby code

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

```sh
./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