Custom compiler support

Ori Pomerantz

In this tutorial you learn how to use a custom compiler with retesteth tests. We do this by following the steps to write and execute a test written in the Huff programming language.

Why Do This?

Sometimes it is convenient to write a test using a different language than the three supported ones (LLL, Solidity, and Yul). While such tests are unlikely to be accepted as standard tests, they can help debug client changes.

Install Huff as part of the Docker

One way to do this is to run restetheth in a docker container you build.

  1. Get the Dockerfile and the script:

    mkdir ~/retestethBuild
    cd ~/retestethBuild
    chmod +x
  2. Edit Dockerfile:

    • On line 1 change the original image from Ubuntu 18.04 to Ubuntu 20.04. This step is necessary because the C libraries on Ubuntu 18.04 are too old for the Huff compiler.

      FROM ubuntu:20.04 as retesteth
    • On the line that downloads the retesteth source from github change the branch from master to develop.

      RUN git clone --depth 1 -b develop /retesteth
    • Before the entry point definition add a command to download and configure the Huff compiler.

      # Huff compiler
      RUN curl -L | bash \
          && ~/.huff/bin/huffup
  3. Issue ./ build.

    You will receive these errors. Ignore them, they are merely an artifact of npm and yarn not being installed on the Docker image.

    /root/.huff/bin/huffup: line 18: npm: command not found
    huffup: warning: It appears your system has an outdated installation of huffc via npm.
    huffup: warning: Uninstalling huffc with npm to allow huffup to take precedence...
    /root/.huff/bin/huffup: line 21: npm: command not found
    /root/.huff/bin/huffup: line 25: yarn: command not found

Update the client configuration

Custom compiler information is provided as part of the client configuration.

  1. Run at least one test to initialize the tests/config directory.

  2. To make life easier, change the ownership of those files:

    sudo find tests/config -exec chown `whoami` {} \;
  3. Copy the t8ntool configuration to t8ntool-huff:

    cd tests/config
    cp -R t8ntool/ t8ntool-huff
  4. Edit tests/config/t8ntool-huff/config to change the customCompilers definition:

    "customCompilers" : {
        ":huff" : ""
  5. Create a file, tests/config/t8ntool-huff/, to call the Huff compiler

    # You can call a custom executable here
    # The code src comes in argument $1 as a path to a file containing the code
    # So if you have custom compiler installed in the system the command would look like:
    # mycompiler $1
    mv $1 $1.huff
    code=`~/.huff/bin/huffc $1.huff -r | grep -v Compiling`
    echo 0x$code
    rm $1.huff
    # Make sure your tool output clean bytecode only with no log or debug messages
    # echo "0x600360005500"

Create a test file that uses Huff

Use this syntax for the code: definition of a contract, such as:

code: |
    #define macro MAIN() = takes(0) returns(0) {
       0x01 0x01 add
       0x00 sstore

The :huff keyword matches the one in tests/config/t8ntool-huff/config, so the retesteth tool knows to call It is followed by the Huff code.

You can see a sample test here.