# Building WSL

## Prerequisites 

The following tools are required to build WSL: 

- CMake >= 2.25
    - Can be installed with `winget install Kitware.CMake`
- Visual Studio with the following components:
    - Windows SDK 26100
    - MSBuild
    - Universal Windows platform support for v143 build tools (X64 and ARM64)
    - MSVC v143 - VS 2020 C++ ARM64 build tools (Latest + Spectre) (X64 and ARM64)
    - C++ core features
    - C++ ATL for latest v143 tools (X64 and ARM64)
    - C++ Clang compiler for Windows
    - .NET desktop development
    - .NET WinUI app development tools

- Building WSL requires support for symbolic links. To ensure this capability, enable [Developer Mode](https://learn.microsoft.com/en-us/windows/apps/get-started/enable-your-device-for-development) in Windows Settings or execute the build process with Administrator privileges.
    
## Building WSL

Once you have cloned the repository, generate the Visual Studio solution by running:

```
cmake .
```

This will generate a `wsl.sln` file that you can build either with Visual Studio, or via `cmake --build .`.

Build parameters:

- `cmake . -A arm64`: Build a package for ARM64
- `cmake . -DCMAKE_BUILD_TYPE=Release`: Build for release
- `cmake . -DBUILD_BUNDLE=TRUE`: Build a bundle msix package (requires building ARM64 first)

Note: To build and deploy faster during development, see options in `UserConfig.cmake`.


## Deploying WSL 

Once the build is complete, you can install WSL by installing the MSI package found under `bin\<platform>\<target>\wsl.msi`, or by running `powershell tools\deploy\deploy-to-host.ps1`.

To deploy on a Hyper-V virtual machine, you can use `powershell tools\deploy\deploy-to-vm.ps1 -VmName <vm> -Username <username> -Password <password>`

## Running tests

To run unit tests, run: `bin\<platform>\<target>\test.bat`. There's quite a lot of tests so you probably don't want to run everything. Here's a reasonable subset:
`bin\<platform>\<target>\test.bat /name:*UnitTest*`

To run a specific test case run:
`bin\<platform>\<target>\test.bat /name:<class>::<test>`
Example: `bin\x64\debug\test.bat /name:UnitTests::UnitTests::ModernInstall` 

To run the tests for WSL1, add `-Version 1`. 
Example: `bin\x64\debug\test.bat -Version 1` 


After running the tests once, you can add `-f` to skip the package installation, which makes the tests faster (this requires test_distro to be the default WSL distribution).

Example:

```
wsl --set-default test_distro
bin\x64\debug\test.bat /name:*UnitTest* -f
```

## Debugging tests

See [debugging](debugging.md) for general debugging instructions.

To attach a debugger to the unit test process, use: `/waitfordebugger` when calling `test.bat`. 
Use `/breakonfailure` to automatically break on the first test failure.