Targets and Tiers
The hosts xclang runs on, the targets it builds for, and how each is tested. How to build for another target is in cross-compiling.
Hosts
A host is a machine the toolchain runs on. Each has its own archive, and every archive carries every target. The "tested on" column names the GitHub-hosted runner.
| host | archive built on | tested on |
|---|---|---|
x86_64-unknown-linux-gnu | Linux x64 | ubuntu-24.04 |
aarch64-unknown-linux-gnu | Linux x64, cross-compiled | ubuntu-24.04-arm |
x86_64-w64-mingw32 | Linux x64, cross-compiled; the toolchain is a MinGW program | windows-2025 |
aarch64-w64-mingw32 | Linux x64, cross-compiled | windows-11-arm |
aarch64-apple-darwin | macOS arm64 | macos-15 |
x86_64-apple-darwin | macOS arm64, cross-compiled | macos-15-intel |
Targets
| target | also spelled | C runtime | runs on | builds on |
|---|---|---|---|---|
x86_64-unknown-linux-gnu | x86_64-pc-linux-gnu, x86_64-linux-gnu (Bazel) | glibc 2.17 | glibc 2.17 or later | every host |
aarch64-unknown-linux-gnu | aarch64-pc-linux-gnu, aarch64-linux-gnu (Bazel) | glibc 2.17 | glibc 2.17 or later | every host |
x86_64-w64-mingw32 | x86_64-w64-windows-gnu, x86_64-pc-windows-gnu | mingw-w64 with UCRT | Windows 10 or later | every host |
aarch64-w64-mingw32 | aarch64-w64-windows-gnu, aarch64-pc-windows-gnu | mingw-w64 with UCRT | Windows 10 or later | every host |
aarch64-apple-darwin | arm64-apple-darwin, arm64-apple-macos, aarch64-apple-macosx, ... | the SDK's libSystem | macOS 13.0 or later | macOS hosts; Linux and Windows hosts with the SDK xclang fetches |
x86_64-apple-darwin | x86_64-apple-macos, x86_64-apple-macosx | the SDK's libSystem | macOS 13.0 or later | macOS hosts; Linux and Windows hosts with the SDK xclang fetches |
x86_64-pc-windows-msvc | x86_64-unknown-windows-msvc | Microsoft's CRT and STL, the hybrid CRT | Windows 10 or later | every host, with the SDK xclang fetches |
aarch64-pc-windows-msvc | aarch64-unknown-windows-msvc | Microsoft's CRT and STL, the hybrid CRT | Windows 10 or later | every host, with the SDK xclang fetches |
All six are tier 1. The macOS targets need Apple's SDK, which comes from Xcode on macOS hosts (macOS). On Linux and Windows hosts they build with the SDK the user fetches from Apple (macOS), and CI runs those programs on arm64 and x64 Macs. The MSVC targets are tier 1 too: CI runs their programs on Windows x64 and arm64 runners (MSVC targets).
What Each Target Has
| Linux | Windows (MinGW) | macOS | Windows (MSVC) | |
|---|---|---|---|---|
| C++ library | libc++, libc++abi, static | libc++, libc++abi, static | libc++, libc++abi, static (not the system's libc++.dylib) | Microsoft's STL, static |
| unwinder | libunwind, static | libunwind, static | the system's (libSystem) | the VC runtime's, static |
| compiler-rt builtins, profile | Supported | Supported | Supported | Supported |
| ASan, TSan, LSan, UBSan, libFuzzer | Supported | Considered | Supported | Supported: UBSan; ASan and libFuzzer for x64 |
| ASan libc++ | Supported | Considered | Supported | none: the STL |
| linker | ld.lld | ld.lld (MinGW driver) | ld64.lld; -fuse-ld=ld for Apple's, without LTO | lld-link |
Sanitizers for the MinGW targets are considered; those of the MSVC targets are in sanitizers.
Tiers
Each target has a tier, as Rust's targets do. The tier says how a target is tested, and so how much a release promises about it.
- Tier 1: built for every release, and its tests run on a GitHub-hosted runner of the target itself; a failure stops the release.
- Tier 2: built for every release, and its tests run under emulation or virtualization: qemu, a virtual machine, Android's emulator, Apple's simulators.
- Tier 3: programs are compiled and linked for it, not run.
For today's six, that means programs built on every host run on a runner of their target, with no emulator (testing).
Not Yet Supported
| status | |
|---|---|
| Sanitizers for MinGW targets | Considered |
Every other target, with its planned tier and its status, is in the roadmap.