cgo: cross-compilation

[ianthehat]

This is currently not possible, as we can only build the standard library in "pure" mode if we are cross compiling.
In theory there is no reason to limit this quite so much, but we need a way to pick the pure version of the standard library when cross compiling without having to compile all libraries in pure mode.

[steeve]

Would it be possible to specify the toolchain itself?

The reason is I worry that relying on things like CGO_CFLAGS, CGO_CPPFLAGS, CGO_CXXFLAGS, CGO_FFLAGS, CGO_LDFLAGS or CC/CXX env vars might be a little overlapping with Bazel's way of doing things, which in my view is far more powerful.

[steeve]

hey @ianthehat, any good news for the new year ? :)

[ianthehat]

Not even looked at this yet I am afraid

[jayconrod]

(Re-triaging old issues)

This should work, at least theoretically. You can target a platform with --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64_cgo (note the _cgo suffix). An appropriate C/C++ toolchain must be configured.

Leaving this issue open because we don't have adequate test coverage or documentation yet.

[devastating]

(Re-triaging old issues)

This should work, at least theoretically. You can target a platform with --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64_cgo (note the _cgo suffix). An appropriate C/C++ toolchain must be configured.

Leaving this issue open because we don't have adequate test coverage or documentation yet.

Hello @jayconrod ,
Is this theoretically working for Linux only? I've tried it with "--platforms @io_bazel_rules_go//go/toolchain:darwin_amd64_cgo", and the binary built still shows "Binary was compiled with 'CGO_ENABLED=0', go-sqlite3 requires cgo to work. This is a stub"

These are the flags I was using:
CC=/usr/bin/gcc CXX=/usr/bin/g++ --features=pure --stamp --platforms @io_bazel_rules_go//go/toolchain:darwin_amd64_cgo

We are trying to cross-compile for darwin on Linux; my experiment is done on darwin and the result is the same.

Thanks in advance!

[jayconrod]

@devastating The --features=pure flag disables cgo. Try without that.

[devastating]

@devastating The --features=pure flag disables cgo. Try without that.

@jayconrod It works on MacOS - however, when I tried to really cross-compile on Linux, I got the error:

ERROR: While resolving toolchains for target @io_bazel_rules_go//:cgo_context_data: no matching toolchains found for types @bazel_tools//tools/cpp:toolchain_type

Did the "_cgo" build feature not support cross-compilation? We are using bazel 1.1.0 release.
Thank you in advance!

[devastating]

I guessed I will have to wait until #1642 is close..

[ChuntaoLu]

Hey, this issue has been open for a while, is cross compiling cgo still not doable today?

[steeve]

It is if you supply your own C toolchain.

Alternatively, you can try this approach: https://dev.to/kristoff/zig-makes-go-cross-compilation-just-work-29ho