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ci | ||
test | ||
toolchain | ||
.bazelrc | ||
.bazelversion | ||
.build.yml | ||
.envrc | ||
.gitignore | ||
BUILD | ||
LICENSE | ||
README.md | ||
WORKSPACE | ||
go.mod | ||
go.sum | ||
release | ||
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repositories.bzl |
README.md
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"
http_archive(
name = "bazel-zig-cc",
sha256 = "e78a9930daa40c47fa67de7e371851452d3eedbb5f56d2904d46e2784888e21e",
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.
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)
- golang/go #46644 cmd/link: with CC=zig: SIGSERV when cross-compiling to darwin/amd64 (CLOSED)
- ziglang/zig #9050 golang linker segfault (CLOSED)
- ziglang/zig #7917 [meta] better c/c++ toolchain compatibility (CLOSED)
- ziglang/zig #7915 ar-compatible command for zig cc (CLOSED)
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.