Lily

Lily is an experimental C++ linter based on linear types. It is a result of my bachelor thesis.

Downloading the repository

git clone --recursive-submodules $REPO_URL

Building

Please use the Nix package manager if possible, it makes everything way, way easier.

Alternatively if you don't want to build the project yourself, you can just use a prebuilt Docker image, see here.

Nix

nix-build --attr lily default.nix

The resulting executable is located in result/bin/. If you wish to install it onto your system using Nix, use nix-env -f default.nix -iA lily.

You may also build a more static version of the executable by using static-exe instead of lily in the commands above.

Developing with Nix

Use nix-shell shell.nix to create a development shell -- a shell with all development dependencies such as Cabal, GHC, etc.

You can use normal Cabal commands when in Nix shell to work on Lily:

• To build Lily using Cabal (better for development, incremental builds):

cabal new-build lily

• To build and run Lily using Cabal with some arguments in $ARGS:

cabal new-run lily -- $ARGS

• To open a GHCi REPL using Cabal:

cabal new-repl lily

Updating dependenies using Niv

The niv tool is used to manage the version of nixpkgs. It is currently pinned to a version of nixpkgs for which lily builds and works.

To update the version of nixpkgs, use the command niv update in the development nix-shell.

Creating and using a Docker image with Nix

Requires Nix, Docker. Warning: Creates a ~300MB image.

1. Create and load the image using Nix

docker load -i $(nix-build --attr docker default.nix)

2. Run the image in current directory

docker run -itv $PWD:/data lily-docker lily [ARGS...]

Example usage:

docker run -itv $PWD:/data lily-docker lily lint examples/various.cpp

Cabal/Stack

Seek the Cabal CI workflow in this repository for guidance.

1. Ensure that your GHC version is 8.8.3
2. Ensure that you have Clang installed with libraries
3. Install my clang-pure fork located in the deps/ folder using Cabal/Stack. For more instructions, view the file DEV.md in deps/clang-pure. Ideally it should be built by cabal new-build in the main folder but who knows?
4. Install this project using Cabal/Stack.
5. Pray that everything worked.

Using

Assuming that $LILY is the way to invoke Lily as it might depend on which installation was chosen.

Use the following command to lint an example file examples/doublemove.cpp:

$LILY lint examples/doublemove.cpp 

Extending

A common issue might be assigning a type to an expression from some C++ library. In order to add your own annotations, modify the initialInferState function in src/Type/Infer.hs. Note that std::move is there as a functioning example of a user-added annotation.