Add musl binary gem support

[stanhu]

This will allow Alpine-based containers to use the precompiled gems without having to install gcompat.

Relates to #648

[cbandy]

I wonder why this one is unknown-linux while below is linux.

[stanhu]

@cbandy I think it's because the gnu compiler is installed via the Ubuntu packages, while the musl compiler is built and installed from https://github.com/richfelker/musl-cross-make.git (see rake-compiler/rake-compiler-dock@da4268d5#diff-f840daec2e49fd92de367e204a8dc78d8713fc3ea99f724da29a841798730fa9):

$ docker run -it ghcr.io/rake-compiler/rake-compiler-dock-image:1.9.1-mri-x86_64-linux-gnu bash
root@06bb6bae360a:/# dpkg -S x86_64-linux-gnu-gcc
gcc-9: /usr/bin/x86_64-linux-gnu-gcc-ranlib-9
gcc: /usr/bin/x86_64-linux-gnu-gcc-ar
gcc: /usr/bin/x86_64-linux-gnu-gcc
gcc-9: /usr/share/man/man1/x86_64-linux-gnu-gcc-9.1.gz
gcc: /usr/share/man/man1/x86_64-linux-gnu-gcc-ranlib.1.gz
gcc: /usr/bin/x86_64-linux-gnu-gcc-ranlib
gcc: /usr/bin/x86_64-linux-gnu-gcc-nm
gcc-9: /usr/bin/x86_64-linux-gnu-gcc-ar-9
gcc-9: /usr/share/man/man1/x86_64-linux-gnu-gcc-ranlib-9.1.gz
gcc-9: /usr/share/man/man1/x86_64-linux-gnu-gcc-ar-9.1.gz
gcc: /usr/share/man/man1/x86_64-linux-gnu-gcc.1.gz
gcc: /usr/share/man/man1/x86_64-linux-gnu-gcc-ar.1.gz
gcc: /usr/share/man/man1/x86_64-linux-gnu-gcc-nm.1.gz
gcc-9: /usr/share/man/man1/x86_64-linux-gnu-gcc-nm-9.1.gz
gcc-9: /usr/bin/x86_64-linux-gnu-gcc-9
gcc-9: /usr/bin/x86_64-linux-gnu-gcc-nm-9

$ docker run -it ghcr.io/rake-compiler/rake-compiler-dock-image:1.9.1-mri-x86_64-linux-musl bash
root@e97ee7e32d0e:/# which x86_64-unknown-linux-musl-gcc
/usr/bin/x86_64-unknown-linux-musl-gcc
root@e97ee7e32d0e:/# dpkg -S x86_64-unknown-linux-musl-gcc
dpkg-query: no path found matching pattern *x86_64-unknown-linux-musl-gcc*

[stanhu]

Does it make sense to test arm64 as well?

diff --git a/.github/workflows/binary-gems.yml b/.github/workflows/binary-gems.yml
index fbed528..3e9fd13 100644
--- a/.github/workflows/binary-gems.yml
+++ b/.github/workflows/binary-gems.yml
@@ -172,6 +172,10 @@ jobs:
             image_platform: linux/x86_64
             gem_platform: x86_64-linux-musl
             dockerfile: alpine
+          - from_image: alpine
+            image_platform: linux/arm64
+            gem_platform: aarch64-linux-musl
+            dockerfile: alpine

     runs-on: ubuntu-latest
     steps:

[larskanis]

I know from ffi.gem that platform x86_64-linux-gnu needs a more recent rubygems version than platform x86_64-linux. And pg-1.6.0-x86_64-linux.gem fully works on alpine without any segfaults, when gcompat is installed. So there's no need to explicit exclude pg-1.6.0-x86_64-linux.gem from musl based systems (in contrast to ffi.gem). That's why I would like to add platform x86_64-linux-musl without renaming x86_64-linux to x86_64-linux-gnu. Does someone has experience with that?

[stanhu]

@larskanis See the detailed notes by @flavorjones in rake-compiler/rake-compiler-dock#117:

Given the inconsisent behavior of gem and bundle when the gem in question ships linux and linux-musl platform gems, it seems pretty clear that it's not a good idea to do this.

So the recommendation has to be:

• either:
  • ship a -linux platform gem that works for both gnu and musl systems,
  • or ship both -linux-gnu and -linux-musl platform gems.
• do NOT ship -linux and -linux-musl platform gems for the same version.

[larskanis]

Thank you @stanhu for the pointer! I checked it and my conclusion is that it makes more sense to provide linux and linux-musl gems. This is because the situation is different from what is described in rake-compiler/rake-compiler-dock#117 . The pg-1.6.0-x86_64-linux.gem and pg-1.6.0-aarch64-linux.gem both work on musl and succeeds the full test suite there. So when old ruby / rubygem / bundler versions pick the non-musl version, then it isn't a bad choice. It fully works when gcompat is present on the system.

The only thing I worry about is the situation when rubygems or bundler completely fails. I can reproduce the Could not find gems matching 'rcee_precompiled (= 0.5.0.1)' valid for all resolution platforms on ruby-3.0 (updated rubygems), bundler 2.5.6/2.5.7, rubygems-3.5.7. But newer bundler-2.5.x versions fix this particular issue and updating bundler is easy, even on older systems and system provided rubies.

IMHO the added requirement of a more recent rubygems version is worse than the "bad" decision to install the non-musl gem on a musl system.

[stanhu]

@larskanis Ok! I've updated this to test both linux and linux-musl gems, with and without gcompat, respectively.

[larskanis]

Oh, I should have notified you. I already put #649 together. The problem is that it fails because after sucessfully building linux-musl gem, it tries to build linux platform gem in addition in the musl image, possibly due to a broken platform selection logic in rake-compiler. See here where x86_64-linux is in the chain of linux-musl.gem

[stanhu]

Thanks. I'll close this in favor of #657 then.

[larskanis]

@stanhu Thank you for helping with musl support! I merged #657 now. Will push a new release in the next days.

[stanhu]

Great! Looking forward to the next release.