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[![builds.sr.ht status](https://builds.sr.ht/~motiejus/bazel-zig-cc.svg)](https://builds.sr.ht/~motiejus/bazel-zig-cc)
# Bazel zig cc toolchain
This is a C/C++ toolchain that can (cross-)compile C/C++ programs. It contains
clang-13, musl, glibc (versions 2-2.34, selectable), all in a ~40MB package.
Read
[here](https://andrewkelley.me/post/zig-cc-powerful-drop-in-replacement-gcc-clang.html)
about zig-cc; the rest of the README will present how to use this toolchain
from Bazel.
# Usage
Add this to your `WORKSPACE`:
```
BAZEL_ZIG_CC_VERSION = "v0.5.0"
http_archive(
name = "bazel-zig-cc",
sha256 = "7d7e2bcfe15fce3a6d46ab1ed6f06e36a4729ff5e75916023a09b425ef6f32dd",
strip_prefix = "bazel-zig-cc-{}".format(BAZEL_ZIG_CC_VERSION),
urls = ["https://git.sr.ht/~motiejus/bazel-zig-cc/archive/{}.tar.gz".format(BAZEL_ZIG_CC_VERSION)],
)
load("@bazel-zig-cc//toolchain:defs.bzl", zig_register_toolchains = "register_toolchains")
zig_register_toolchains()
# Or, if you are using this in production, you probably want more control:
zig_register_toolchains(
version = "<...>",
url_formats = [
"https://example.internal/zig/zig-{host_platform}-{version}.tar.xz",
],
host_platform_sha256 = { ... },
)
```
And this to `.bazelrc`:
```
build --incompatible_enable_cc_toolchain_resolution
build --extra_toolchains @zig_sdk//:linux_amd64_gnu.2.19_toolchain
build --extra_toolchains @zig_sdk//:linux_arm64_gnu.2.28_toolchain
build --extra_toolchains @zig_sdk//:darwin_amd64_toolchain
build --extra_toolchains @zig_sdk//:darwin_arm64_toolchain
```
The snippets above will download the zig toolchain and register it for the
following platforms:
- `x86_64-linux-gnu.2.19` for `["@platforms//os:linux", "@platforms//cpu:x86_64"]`.
- `x86_64-linux-gnu.2.28` for `["@platforms//os:linux", "@platforms//cpu:aarch64"]`.
- `x86_64-macos-gnu` for `["@platforms//os:macos", "@platforms//cpu:x86_64"]`.
- `aarch64-macos-gnu` for `["@platforms//os:macos", "@platforms//cpu:aarch64"]`.
Note that both Go and Bazel naming schemes are accepted. For convenience with
Go, the following Go-style toolchain aliases are created:
|Bazel (zig) name | Go name |
|---------------- | -------- |
|`x86_64` | `amd64` |
|`aarch64` | `arm64` |
|`macos` | `darwin` |
For example, the toolchain `linux_amd64_gnu.2.28` is aliased to
`x86_64-linux-gnu.2.28`. To find out which toolchains can be registered or
used, run:
```
$ bazel query @zig_sdk//... | grep _toolchain$
```
## Specifying non-default toolchains
You may explicitly request Bazel to use a specific toolchain, even though a
different one is registered using `--extra_toolchains <toolchain>` in
`.bazelrc`. For example, if you wish to compile a specific binary (or run
tests) on linux/amd64/musl, you may specify:
```
--extra_toolchains @zig_sdk//:linux_amd64_musl_toolchain
```
## UBSAN and "SIGILL: Illegal Instruction"
`zig cc` differs from "mainstream" compilers by [enabling UBSAN by
default][ubsan1]. Which means your program may compile successfully and crash
with:
```
SIGILL: illegal instruction
```
This is by design: it encourages program authors to fix the undefined behavior.
There are [many ways][ubsan2] to find the undefined behavior.
# Known Issues In bazel-zig-cc
These are the things you may stumble into when using bazel-zig-cc. I am
unlikely to implement them any time soon, but patches implementing those will
be accepted. See [Questions & Contributions](#questions-amp-contributions) on
how to contribute.
## Zig cache
Currently zig cache is in `$HOME`, so `bazel clean --expunge` does not clear
the zig cache. Zig's cache should be stored somewhere in the project's path.
## Toolchain and platform target locations
The path to Bazel toolchains is `@zig_sdk//:<toolchain>_toolchain`. It should
be moved to `@zig_sdk//toolchain:<toolchain>` or similar; so the user-facing
targets are in their own namespace.
Likewise, platforms are `@zig_sdk//:<platform>_platform`, and should be moved
to `@zig_sdk//:platform:<platform>`.
## OSX: sysroot
For non-trivial programs (and for all darwin/arm64 cgo programs) MacOS SDK may
be necessary. Read [Jakub's comment][sysroot] about it. Support for OSX sysroot
is currently not implemented.
## OSX: different OS targets (Catalina -- Monterey)
[Zig 0.9.0](https://ziglang.org/download/0.9.0/release-notes.html#macOS) may
target macos.10 (Catalina), macos.11 (Big Sur) or macos.12 (Monterey). It
currently targets the lowest version, without ability to change it.
# Known Issues In Upstream
This section lists issues that I've stumbled into when using `zig cc`, and is
outside of bazel-zig-cc's control.
## using glibc 2.27 or older
**Severity: Low**
Task: [ziglang/zig #9485 glibc 2.27 or older: fcntl64 not found, but zig's glibc headers refer it](https://github.com/ziglang/zig/issues/9485)
Background: when glibc 2.27 or older is selected, it may miss `fcntl64`. A
workaround is applied for `x86_64`, but not for aarch64. The same workaround
may apply to aarch64, but the author didn't find a need to test it (yet).
# Closed Upstream Issues
- [ziglang/zig #10386 zig cc regression in 0.9.0](https://github.com/ziglang/zig/issues/10386)(CLOSED, thanks Xavier)
- [ziglang/zig #10312 macho: fail if requested -framework is not found](https://github.com/ziglang/zig/pull/10312) (CLOSED, thanks kubkon)
- [ziglang/zig #10299 [darwin aarch64 cgo] regression](https://github.com/ziglang/zig/issues/10299) (CLOSED, thanks kubkon)
- [ziglang/zig #10297 [darwin x86_64 cgo] regression](https://github.com/ziglang/zig/issues/10297) (CLOSED, thanks kubkon)
- [ziglang/zig #9431 FileNotFound when compiling macos](https://github.com/ziglang/zig/issues/9431) (CLOSED, thanks andrewrk)
- [ziglang/zig #9139 zig c++ hanging when compiling in parallel](https://github.com/ziglang/zig/issues/9139) (CLOSED, thanks andrewrk)
- [ziglang/zig #9050 golang linker segfault](https://github.com/ziglang/zig/issues/9050) (CLOSED, thanks kubkon)
- [ziglang/zig #7917 [meta] better c/c++ toolchain compatibility](https://github.com/ziglang/zig/issues/7917) (CLOSED, thanks andrewrk)
- [ziglang/zig #7915 ar-compatible command for zig cc](https://github.com/ziglang/zig/issues/7915) (CLOSED, thanks andrewrk)
- [ziglang/zig #7667 misplaced relocated glibc stubs (pthread_sigmask)](https://github.com/ziglang/zig/issues/7667) (CLOSED, thanks mjonaitis and andrewrk)
- [rules/go #2894 Per-arch_target linker flags](https://github.com/bazelbuild/rules_go/issues/2894) (CLOSED, thanks mjonaitis)
- [golang/go #46644 cmd/link: with CC=zig: SIGSERV when cross-compiling to darwin/amd64](https://github.com/golang/go/issues/46644) (CLOSED, thanks kubkon)
# Testing
## build & run linux cgo + glibc
```
$ bazel build --platforms @zig_sdk//:linux_amd64_platform //test/go:go
$ file bazel-out/k8-opt-ST-d17813c235ce/bin/test/go/go_/go
bazel-out/k8-opt-ST-d17813c235ce/bin/test/go/go_/go: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.0.0, Go BuildID=redacted, with debug_info, not stripped
$ bazel-out/k8-opt-ST-d17813c235ce/bin/test/go/go_/go
hello, world
```
## test linux cgo + musl on arm64 (under qemu-aarch64)
```
$ bazel test \
--config=qemu-aarch64 \
--platforms @zig_sdk//:linux_arm64_platform \
--extra_toolchains @zig_sdk//:linux_arm64_musl_toolchain //test/...
...
INFO: Build completed successfully, 10 total actions
//test/go:go_test PASSED in 0.2s
```
## macos cgo
```
$ bazel build --platforms @zig_sdk//:darwin_amd64_platform //test/go:go
...
$ file bazel-out/k8-opt-ST-d17813c235ce/bin/test/go/go_/go
bazel-out/k8-opt-ST-d17813c235ce/bin/test/go/go_/go: Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE|HAS_TLV_DESCRIPTORS>
```
## Transient docker environment
```
$ docker run -e CC=/usr/bin/false -ti --rm -v $(pwd):/x -w /x debian:bullseye-slim
# apt update && apt install -y direnv git
# . .envrc
```
And run the `bazel build` commands above. Take a look at `.build.yml` and see
how CI does it.
# Questions & Contributions
Project's mailing list is [~motiejus/bazel-zig-cc][mailing-list]. The mailing
list is used for:
- announcements (I am aiming to send an email with every release).
- user discussions.
- raising issues.
- contributions.
I will generally respond to emails about issues. I may even be able to fix
them. However, no promises: you are much more likely (and welcome!) to get it
fixed by submitting a patch.
To contribute, send your patches to the mailing list, as described in
[git-send-email.io][git-send-email] or via [Sourcehut web UI][video].
Development is happening in the [next][next] branch. It may be incompatible
with main, but is expected to be landed "soon".
Copyright is retained by the contributors.
# Thanks
Many thanks to Adam Bouhenguel and his [bazel-zig-cc][ajbouh], the parent of
this repository. Also, the Zig team for making this all possible and handling
the issues promptly.
[mailing-list]: https://lists.sr.ht/~motiejus/bazel-zig-cc
[ajbouh]: https://github.com/ajbouh/bazel-zig-cc/
[git-send-email]: https://git-send-email.io/
[video]: https://spacepub.space/w/no6jnhHeUrt2E5ST168tRL
[sysroot]: https://github.com/ziglang/zig/issues/10299#issuecomment-989153750
[ubsan1]: https://github.com/ziglang/zig/issues/4830#issuecomment-605491606
[ubsan2]: https://github.com/ziglang/zig/issues/5163
[next]: https://git.sr.ht/~motiejus/bazel-zig-cc/tree/next
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