bin | ||
ci | ||
test | ||
toolchain | ||
.bazelrc | ||
.bazelversion | ||
.build.yml | ||
.envrc | ||
.gitignore | ||
BUILD | ||
go.mod | ||
go.sum | ||
LICENSE | ||
README.md | ||
release | ||
relnotes.awk | ||
repositories.bzl | ||
WORKSPACE |
Bazel zig cc toolchain
This is a C/C++ toolchain that can (cross-)compile C/C++ programs. It contains clang-12, musl, glibc (versions 2-2.33, selectable), all in a ~40MB package. Read here 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 = "0.3.1"
http_archive(
name = "bazel-zig-cc",
sha256 = "d1fad7b044b0a70c584ada97010cb9d350a596a1df26ca04cb4846e83ed2482f",
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(register = [
"x86_64-linux-gnu.2.28",
"x86_64-macos-gnu",
])
The snippet above will download the zig toolchain and register it for the following platforms:
x86_64-linux-gnu.2.28
for["@platforms//os:linux", "@platforms//cpu:x86_64"]
.x86_64-macos-gnu
for["@platforms//os:macos", "@platforms//cpu:x86_64"]
.
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
is aliased to
x86_64-linux-gnu.2.28
. To find out which toolchains can be registered or
used, run:
$ bazel query @zig_sdk//... | sed -En '/.*_toolchain$/ s/.*:(.*)_toolchain$/\1/p'
Read #Known Issues before using.
Known Issues
Parallel zig c++
invocations may fail
Severity: High
Task: ziglang/zig #9431 FileNotFound when compiling macos
Background: there is a race when calling zig c++
, which Bazel does a lot.
This may fail compilation. Yours truly only reproduced it on macos with a cold
cache. Based on that, a workaround in the toolchain exists, named
speed_first_safety_later
. The possible values are auto
(default), yes
,
no
.
relocation error with glibc < 2.32
Severity: High
Background: one of our internal shared libraries (which we must build with glibc 2.19) does not load on an older system:
id: relocation error: /lib/x86_64-linux-gnu/libnss_uber.so.2: symbol pthread_sigmask, version GLIBC_2.2.5 not defined in file libc.so.6 with link time reference
Severity is high, because there is no known workaround: the shared library, when built with this toolchain, will not work on our target system.
newer zig fails darwin tests
Severity: no yet triaged
Task: not yet triaged.
If zig is upgraded in this repository to nightly, it can't build the Darwin executable. This section will be updated when more details are identified.
fcntl64 linking error on glibc < 2.28
Severity: Low
Task: ziglang/zig #9485 glibc 2.27 or older: fcntl64 not found, but zig's glibc headers refer it
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).
cgo for darwin (macos)
Severity: Low
Task: rules/go #2894 Per-arch_target linker flags
Background: until there is a better "global" way (i.e. the task is solved), all
go_binary
targets destined for Darwin (macos) need an extra gc_linkopts
flag:
go_binary(
<...>
gc_linkopts = select({
"@platforms//os:macos": ["-s", "-w", "-buildmode=pie"],
"//conditions:default": [],
}),
)
incorrect glibc version autodetection
Severity: Low
Task: ziglang/zig zig detects wrong libc version #6469
Background: zig detects an incorrect glibc version when not specified.
Therefore, until the task is resolved, registering a GNU toolchain without a
version suffix (e.g. linux_amd64_gnu
) is not recommended. We recommend
specifying the suffix to the oldest system that is mean to run the compiled
binaries. This is safe, because glibc is backwards-compatible. Alternatively,
use musl.
Closed issues
- ziglang/zig #9139 zig c++ hanging when compiling in parallel (CLOSED, thanks andrewrk)
- golang/go #46644 cmd/link: with CC=zig: SIGSERV when cross-compiling to darwin/amd64 (CLOSED, thanks kubkon)
- ziglang/zig #9050 golang linker segfault (CLOSED, thanks kubkon)
- ziglang/zig #7917 [meta] better c/c++ toolchain compatibility (CLOSED, thanks andrewrk)
- ziglang/zig #7915 ar-compatible command for zig cc (CLOSED, thanks andrewrk)
Testing
linux cgo + glibc 2.19
$ bazel build --platforms @io_bazel_rules_go//go/toolchain:linux_amd64_cgo //test:hello
$ file bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello
bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello: 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
linux cgo + musl
$ bazel build \
--platforms @io_bazel_rules_go//go/toolchain:linux_amd64_cgo \
--extra_toolchains @zig_sdk//:linux_amd64_musl_toolchain //test:hello
...
$ file ../bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello
../bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, Go BuildID=redacted, with debug_info, not stripped
$ ../bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/hello_/hello
hello, world
macos cgo
$ bazel build --platforms @io_bazel_rules_go//go/toolchain:darwin_amd64_cgo //test:gognu
...
$ file bazel-bin/test/gognu_/gognu
bazel-bin/test/gognu_/gognu: Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>
Transient docker environment
$ docker run -e CC=/usr/bin/false -ti --rm -v $(pwd):/x -w /x debian:buster-slim
# apt update && apt install wget git -y
# . .envrc
And run the bazel build
commands above. Take a look at .build.yml
and see
how CI does it.
Credits
Many thanks to Adam Bouhenguel and his bazel-zig-cc, the parent of this repository.