Support for arm64 / aarch64

[moderation]

Envoy Proxy just implemented rules_foreign_cc today with PR envoyproxy/envoy#5218. My builds for Linux x86_64 and macOS are working fine. However my arm64 / aarch64 builds are failing with the following error.

ERROR: While resolving toolchains for target //bazel/foreign_cc:zlib: no matching toolchains found for types @rules_foreign_cc//tools/build_defs/shell_toolchain/toolchains:shell_commands

It looks like only Linux, Windows and macOS are supported on the x86_64 architecture after looking at https://github.com/bazelbuild/rules_foreign_cc/blob/master/tools/build_defs/shell_toolchain/toolchains/toolchain_mappings.bzl

/cc @htuch

[irengrig]

Sorry.
Yes, this is a bug with rules_foreign_cc to not provide the default toolchain implementation.
I just added default toolchain in #213, with "linux" be assumed to be a os name to be passed to CMake. (I.e. that is what is recorded into CMake's crosstool file.
If the platform name should be different, it can be overridden with passing correct CMAKE_SYSTEM_NAME, but as we better try to pass the correct name, I will try to improve on that)

I will continue to check it with amd64/aarch64 later today in a Docker container. Are there more speicfic details to take into account?

Sorry again.

[moderation]

Thanks. I can confirm that if I modify the following Envoy will build on aarch64.

diff --git a/~/Library/rules_foreign_cc/tools/build_defs/shell_toolchain//toolchains/toolchain_mappings.bzl b/~/Library/envoyproxy/moderation/rules_foreign_cc/tools/build_defs/shell_toolchain/toolchains/toolchain_mappings.bzl
index af9647e..42fa81a 100644
--- a/~/Library/rules_foreign_cc/tools/build_defs/shell_toolchain//toolchains/toolchain_mappings.bzl
+++ b/~/Library/envoyproxy/moderation/rules_foreign_cc/tools/build_defs/shell_toolchain/toolchains/toolchain_mappings.bzl
@@ -11,7 +11,7 @@ TOOLCHAIN_MAPPINGS = [
     _ToolchainMapping(
         exec_compatible_with = [
             "@bazel_tools//platforms:linux",
-            "@bazel_tools//platforms:x86_64",
+            "@bazel_tools//platforms:aarch64",
         ],
         file = "@rules_foreign_cc//tools/build_defs/shell_toolchain/toolchains/impl:linux_commands.bzl",
     ),

I'll try using CMAKE_SYSTEM_NAME. I did have a couple of tries at adding a new ToolchainMapping section but ran into errors. So hopefully it won't be too hard to add aarch64 in addition to x86_64. There are teams building Envoy for the IBM ppc64le architecture as well so I expect there will be several architectures that need to be added.

[irengrig]

I just provided the possibility to introduce custom ToolchainMappings: #214.
Please refer to example there.
I will make it now that CMAKE_SYSTEM_NAME comes from os_name() function, if it is not windows-linux-osx.

Currently I am experimenting with the amd64/alpine container, should I select some better variant?

[moderation]

I just tested the latest commit and it works on aarch64. Thanks for the quick turnaround.

[irengrig]

I will make it now that CMAKE_SYSTEM_NAME comes from os_name() function

Done in #215.

[irengrig]

I just tested the latest commit and it works on aarch64. Thanks for the quick turnaround.

Cool, thank you!

[irengrig]

Can I close the issue then?

[moderation]

Yes - thanks again for the quick turnaround.