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hermetic_cc_toolchain/README.md
2021-06-08 08:01:08 +03:00

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# Bazel zig cc toolchain for Go
This is a prototype zig-cc toolchain that can compile cgo programs with these c
libraries:
- glibc 2.19
- musl
glibc 2.19 is the default. That means, glibc 2.19 toolchain is registered with
these basic constraints:
```
[
"@platforms//os:linux",
"@platforms//cpu:x86_64",
]
```
# Testing
## linux cgo + glibc 2.19
Using the default toolchain:
```
$ bazel build --toolchain_resolution_debug=true //test:gognu
...
$ ../bazel-bin/test/gognu_/gognu
hello, world
$ file ../bazel-bin/test/gognu_/gognu
../bazel-bin/test/gognu_/gognu: 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
```
Explicitly the toolchain explicitly `-gnu`:
```
$ bazel run --platforms @com_github_ziglang_zig//:platform_x86_64-linux-gnu //test:gognu
```
## linux cgo + musl
```
$ bazel build --platforms @com_github_ziglang_zig//:platform_x86_64-linux-musl //test:gomusl
...
$ file ../bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/gomusl_/gomusl
../bazel-out/k8-fastbuild-ST-d17813c235ce/bin/test/gomusl_/gomusl: 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/gomusl_/gomusl
hello, world
```
## macos cgo + gnu
Does not work?
```
$ bazel build --platforms @com_github_ziglang_zig//:platform_x86_64-macos-musl //test:gognu
...
```
## Transient docker environment
```
$ docker run -ti --rm -v $(pwd):/x -w /x debian:buster-slim
# apt update && apt install curl ca-certificates -y && curl -L https://github.com/bazelbuild/bazelisk/releases/download/v1.7.5/bazelisk-linux-amd64 > /usr/local/bin/bazel && chmod +x /usr/local/bin/bazel
# export CC=/usr/bin/false
```
And run the `bazel build` commands above. Take a look at `.build.yml` and see
how CI does it.
# Appendix: compiling manually
zcc
```
#!/bin/bash
exec zig cc -target x86_64-macos-gnu "$@"
```
Build:
``
GOOS=darwin GOARCH=amd64 CC=zcc go build -ldflags "-linkmode external -extldflags -static" hello.go
```