[![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 = "v0.4.4" http_archive( name = "bazel-zig-cc", sha256 = "ad6384b4d16ebb3e5047df6548a195e598346da84e5f320250beb9198705ac81", 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() ``` 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 ` 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. ## Alternative download URLs Currently zig is downloaded from [dl.jakstys.lt/zig](https://dl.jakstys.lt/zig/), which is nuts. One should provide a way to specify alternative URLs for the zig toolchain. ## Toolchain and platform target locations The path to Bazel toolchains is `@zig_sdk//:_toolchain`. It should be moved to `@zig_sdk//toolchain:` or similar; so the user-facing targets are in their own namespace. Likewise, platforms are `@zig_sdk//:_platform`, and should be moved to `@zig_sdk//: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 \ --run_under=qemu-aarch64-static \ --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: ``` ## Transient docker environment ``` $ docker run -e CC=/usr/bin/false -ti --rm -v $(pwd):/x -w /x debian:bullseye-slim # apt update && apt install direnv git -y # . .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]. 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