Cross Compilation of Ruby

System Specifications

Build Architecture: x86_64-linux-gnu
Host Architecture: riscv64-unknown-linux-gnu
Operating System for Installation Procedure: Ubuntu 20.04

Pre-requisites

Pre-requisites for installing ruby from source can be installed using the following command 

sudo apt-get -y install libc6-dev libssl-dev libmysql++-dev libsqlite3-dev make build-essential libssl-dev libreadline6-dev zlib1g-dev libyaml-dev

Other than this, ruby itself is needed for building ruby from source.

sudo apt install ruby

There is another thing which needs to be taken care of before building ruby from source. If ruby is installed on system itself using apt, then cross compiling ruby will end up in an error as shown in the image below. This error is seen in ruby 2.7.0p0 (2019-12-25 revision 647ee6f091) [x86_64-linux-gnu].

ruby_system_error

To tackle this issue, one workaround is to install build ruby for native system, then delete ruby which was installed through apt. This procedure will be added in the Build section.

Getting source code

Source code of ruby can be obtained from github repository using the command below: 

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

Build

Installing ruby for native architecture

Before cross-compiling, one must install ruby from source on the native machine which will solve the error described in Pre-requisites section above.

  • (THIS STEP IS STRONGLY RECOMMENDED !)In the source directory, create a folder with any name in which Makefile will be generated otherwise there will be a lot of files made in the source directory (possibly create copy of repo directory).
  • In the source directory of ruby run following command to generate configure file. 
./autogen.sh
  • After this, run the following configure command to generate Makefile. 
../configure --prefix=$PREFIX #$PREFIX is where you want to install binary files at the end, so replace it.
  • After the above command is completed, run following command to start the build 
make -j$(nproc) #-j$(nproc) uses parallelism for make
  • After the above command is complete, run following command to install the binaries on the specified path mentioned in --prefix above 
make install
  • Now ruby should be available in the $PREFIX path (also in the .bashrc). Add $PREFIX path to $PATH variable and uninstall the the ruby installed using apt otherwise, the source will keep using that one for building and the error will persist. 
sudo apt purge ruby

Cross-Compiling Ruby for riscv64-unknown-linux-gnu

  • After the ruby installed using apt is uninstalled from the system, clean the working directory with following command. 
make clean
  • After cleaning the working directory, generate the Makefile again for cross-compiling ruby for riscv64-unknown-linux-gnu target and host using the command below 
../../configure --prefix=$PREFIX --build=x86_64-linux-gnu --host=riscv64-unknown-linux-gnu --target=riscv64-unknown-linux-gnu
  • After the above command is successful, start build with following command 
make -j(nproc)
  • Install the binaries in path mentioned with --prefix above with following command 
make install
  • After this process, ruby will be installed inside $PREFIX/ directory.

Note: Currently, this process (as checked on version 3.1.2) installs ruby without extensions shown in the following image

ruby_extensions