jarle Building Windows
Building Bun on Windows
This document describes the build process for Windows. If you run into problems, please join the #contributing channel on our Discord for help.
It is strongly recommended to use PowerShell 7 (pwsh.exe) instead of the default powershell.exe.
Prerequisites
Enable Scripts
By default, running unverified scripts are blocked.
Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Unrestricted
System Dependencies
Bun v1.1 or later. We use Bun to run it's own code generators.
irm bun.sh/install.ps1 | iex
Visual Studio with the "Desktop Development with C++" workload. While installing, make sure to install Git as well, if Git for Windows is not already installed.
Visual Studio can be installed graphically using the wizard or through WinGet:
winget install "Visual Studio Community 2022" --override "--add Microsoft.VisualStudio.Workload.NativeDesktop Microsoft.VisualStudio.Component.Git " -s msstore
After Visual Studio, you need the following:
- LLVM 21.1.8
- Go
- Rust
- NASM
- Perl
- Ruby
- Node.js
The Zig compiler is automatically downloaded, installed, and updated by the building process.
Scoop can be used to install these remaining tools easily.
irm https://get.scoop.sh | iex
scoop install nodejs-lts go rust nasm ruby perl ccache
# scoop seems to be buggy if you install llvm and the rest at the same time
scoop install llvm@21.1.8
For Windows ARM64, download LLVM 21.1.8 directly from GitHub releases (first version with ARM64 Windows builds):
# Download and install LLVM for ARM64
Invoke-WebRequest -Uri "https://github.com/llvm/llvm-project/releases/download/llvmorg-21.1.8/LLVM-21.1.8-woa64.exe" -OutFile "$env:TEMP\LLVM-21.1.8-woa64.exe"
Start-Process -FilePath "$env:TEMP\LLVM-21.1.8-woa64.exe" -ArgumentList "/S" -Wait
If you intend on building WebKit locally (optional, x64 only), you should install these packages:
scoop install make cygwin python
Cygwin is not required for ARM64 builds as WebKit is provided as a pre-built binary.
From here on out, it is expected you use a PowerShell Terminal with .\scripts\vs-shell.ps1 sourced. This script is available in the Bun repository and can be loaded by executing it:
.\scripts\vs-shell.ps1
To verify, you can check for an MSVC-only command line such as mt.exe
Get-Command mt
Building
bun run build
# after the initial `bun run build` you can use the following to build
ninja -Cbuild/debug
If this was successful, you should have a bun-debug.exe in the build/debug folder.
.\build\debug\bun-debug.exe --revision
You should add this to $Env:PATH. The simplest way to do so is to open the start menu, type "Path", and then navigate the environment variables menu to add C:\.....\bun\build\debug to the user environment variable PATH. You should then restart your editor (if it does not update still, log out and log back in).
Extra paths
- WebKit is extracted to
build/debug/cache/webkit/ - Zig is extracted to
build/debug/cache/zig/bin/zig.exe
Tests
You can run the test suite either using bun test <path> or by using the wrapper script bun node:test <path>. The bun node:test command runs every test file in a separate instance of bun.exe, to prevent a crash in the test runner from stopping the entire suite.
# Setup
bun i --cwd packages\bun-internal-test
# Run the entire test suite with reporter
# the package.json script "test" uses "build/debug/bun-debug.exe" by default
bun run test
# Run an individual test file:
bun-debug test node\fs
bun-debug test "C:\bun\test\js\bun\resolve\import-meta.test.js"
Troubleshooting
.rc file fails to build
llvm-rc.exe is odd. don't use it. use rc.exe, to do this make sure you are in a visual studio dev terminal, check rc /? to ensure it is Microsoft Resource Compiler
failed to write output 'bun-debug.exe': permission denied
you cannot overwrite bun-debug.exe if it is already open. you likely have a running instance, maybe in the vscode debugger?