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Adding a new language

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MCJ Vasseur edited this page Jan 3, 2024 · 6 revisions

DOMjudge has a default set of languages but it is possible to add your own.

Every submission is ran in an isolated container so the best way to test a new language is to first get the new language installed in the container via the options of make-chroot start this container with domjudge_run_chroot and test if you can compile and run some default programs to verify that everything can work.

When this works start to build the run/build scripts by looking at similar languages which already exist in DOMjudge and create the language with you own build/run script.

Default DOMjudge will not mount the /tmp which is used by for example R, so in case of such failures check if the tmp dir can be set with an environment variable or extend the chroot-start-stop or look into CREATE_WRITABLE_TEMP_DIR defined here.

Be aware that providing writable directories opens up a security hole where the submission may write data to temp and this way pass information from one testcase run to the next.

Kotlin

Kotlin is an officially supported programming language in the programming environment of the ICPC world finals.

To add the Kotlin programming language to a DOMjudge installation, first, the Kotlin command-line compiler should be installed in the chroot environment of the judgehosts (see Installation of the judgehosts - creating a chroot environment | DOMjudge documentation).

Installing Kotlin on existing judgehost

If there is an already running instance of judgehost, access its terminal and unzip the Kotlin compiler in its chroot environment directory (usually /chroot/domjudge/); optionally, for automatic Kotlin compiler discovery in the Kotlin run script, include the extracted bin/kotlinc in the PATH variable of the chroot environment (can be done by creating a symbolic link to the extracted bin/kotlinc inside a directory already included in the PATH); for example:

# A judgehost terminal

CHROOTDIR="/chroot/domjudge"
KOTLIN_VERSION="1.7.21"

# Download the Kotlin compiler zip.
wget -q "https://github.com/JetBrains/kotlin/releases/download/v$KOTLIN_VERSION/kotlin-compiler-$KOTLIN_VERSION.zip"

# Unzip the Kotlin compiler inside the chroot environment.
unzip -qq -d "$CHROOTDIR/usr/local/lib/" "./kotlin-compiler-$KOTLIN_VERSION.zip"

# Include bin/kotlinc in the PATH variable of the chroot environment by creating a symbolic link.
chroot "$CHROOTDIR/" ln -s "/usr/local/lib/kotlinc/bin/kotlinc" "/usr/local/bin/kotlinc"

# Optionally as a cleanup step, remove the downloaded zip file.
rm "./kotlin-compiler-$KOTLIN_VERSION.zip"

Installing Kotlin by editing judgehost install scripts

You can also modify the judgehost install scripts to add Kotlin; simply edit the misc_tools/dj_make_chroot.in script (this raw script can be found a release tarball or git sources) and add something like the above in an appropriate place; for example, after installing debs (this line), add:

...

# Install Kotlin
KOTLIN_VERSION="1.7.21"
wget -q "https://github.com/JetBrains/kotlin/releases/download/v$KOTLIN_VERSION/kotlin-compiler-$KOTLIN_VERSION.zip"
unzip -qq -d "$CHROOTDIR/usr/local/lib/" "./kotlin-compiler-$KOTLIN_VERSION.zip"
in_chroot "ln -s \"/usr/local/lib/kotlinc/bin/kotlinc\" \"/usr/local/bin/kotlinc\""
rm "./kotlin-compiler-$KOTLIN_VERSION.zip"

...

Judgehost Docker image with Kotlin

If you want a judgehost Docker image with Kotlin, modify the docker/judgehost/chroot-and-tar.sh script in the DOMjudge packaging repository, such as:

#!/bin/bash

# Usage: https://github.com/DOMjudge/domjudge/blob/main/misc-tools/dj_make_chroot.in#L58-L87
/opt/domjudge/judgehost/bin/dj_make_chroot

CHROOTDIR="/chroot/domjudge"
KOTLIN_VERSION="1.7.21"

echo "Downloading Kotlin compiler"
wget -q "https://github.com/JetBrains/kotlin/releases/download/v$KOTLIN_VERSION/kotlin-compiler-$KOTLIN_VERSION.zip" -P /
echo "Extracting Kotlin compiler"
unzip -qq -d "/chroot/domjudge/usr/local/lib/" "/kotlin-compiler-$KOTLIN_VERSION.zip"
chroot "$CHROOTDIR" ln -s "/usr/local/lib/kotlinc/bin/kotlinc" "/usr/local/bin/kotlinc"
rm "/kotlin-compiler-$KOTLIN_VERSION.zip"
echo "Done setting up Kotlin"

cd /
echo "[..] Compressing chroot"
tar -czpf /chroot.tar.gz --exclude=/chroot/tmp --exclude=/chroot/proc --exclude=/chroot/sys --exclude=/chroot/mnt --exclude=/chroot/media --exclude=/chroot/dev --one-file-system /chroot
echo "[..] Compressing judge"
tar -czpf /judgehost.tar.gz /opt/domjudge/judgehost

Then run docker/build.sh to build judgehost and domserver images, or docker/build-judgehost.sh after manually downloading the DOMjudge source (first steps of the docker/build.sh), to build only the judgehost image:

# In the DOMjudge packaging repository root.

cd docker/
DOMJUDGE_VERSION="8.2.2"
wget --quiet "https://www.domjudge.org/releases/domjudge-${DOMJUDGE_VERSION}.tar.gz" -O "./domjudge.tar.gz"
./build-judgehost.sh "localhost/domjudge/judgehost:${DOMJUDGE_VERSION}-kotlin"

Enabling Kotlin in the admin dashboard

After successfully installing the Kotlin command-line compiler on judgehosts, Kotlin language should be enabled in the DOMjudge Jury interface for submissions:

  • Navigate to the DOMjudge website.
  • Login as admin.
  • Go to "Languages" settings.
  • Select kt from "Disabled languages"; if it is already in "Enabled languages", then you are done.
  • Turn the "Allow submit" to "Yes".

A heads-up about the default kt run script: if the DOMjudge version is in range 8.2.0 to 8.2.2 (both inclusive), the automatic Kotlin compiler directory discovery might fail if kotlinc is a symbolic link; one solution is to manually fill-in the KOTLIN_DIR variable in the run script; another solution is to update the run script to its latest commit.

The run script can be edited in the DOMjudge Jury interface: "Languages" - kt - "Compile script / kt" - Content / run.

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