New build failure on 2.7.4-alpine-amd64 (maybe revisit #364?)

[keithlayne]

Sure looks like #364 broke my build. Specifically, I'm on 2.7.4-alpine on amd64 and the short version is that every single gem with native dependencies that bundle tried to install failed.

FROM ruby:2.7.4-alpine
RUN apk add --no-cache build-base
WORKDIR /app
RUN printf "source 'https://rubygems.org'\nruby '2.7.4'\ngem 'racc'" > Gemfile
RUN bundle install

Building this will fail, but if you s/7.4/6.8/, it builds fine.

[keithlayne]

Also, just so this is clear, my image build failures began immediately after the most recent push to docker hub.

[bpo]

I'm seeing the same issue with all builds of native gems on the latest 2.7.4-alpine3.14 - complaints about "cannot find -lucontext", for example when building bcrypt:

linking shared-object bcrypt_ext.so
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld:
cannot find -lucontext
collect2: error: ld returned 1 exit status
make: *** [Makefile:262: bcrypt_ext.so] Error 1
 
make failed, exit code 2

[keithlayne]

Ugh, I feel dumb, I skimmed over those log lines and missed them, but those make it obvious I think that #364 is the culprit.

[keithlayne]

Found a workaround that also should have been obvious: add libucontext-dev via apk. Can confirm this fixes my build for the moment.

[keithlayne]

Seems like that's included for the build of ruby? So I more probably need to add libucontext because ruby needs it at runtime...will test.

[tianon]

Ooof, just went to file this issue myself -- thanks for chasing this down with some good details, folks. 😄

I guess we ought to make #364 actually conditional and only apply it for architectures which do require it. 😩

The other option would be to just always keep libucontext-dev installed, which would add ~249KB to our overall image size. 🤔

[tianon]

(To be clear - @yosifkit is currently typing up a solution and should have a PR open ASAP.)

[cameronbourgeois]

I came here to file this issue too! Commit #364 has broken our builds.

Running apk add libucontext-dev fixed our builds for now too 👍 Thanks for that.

[keithlayne]

AFAICT the lib is only needed at build time for gems with native extensions...seems like using gems with native extensions works, even if -lucontext was passed to the linker during the build. I guess if it doesn't actually use the lib, then it's basically a no-op? Then I guess it's not actually getting used in the ruby build on x86_64? This is totally unimportant, and I'm totally curious 😁

[tianon]

@keithlayne correct -- it's only even necessary on three architectures, so fixing it to be architecture-conditional (and keeping libucontext-dev on the affected architectures) is #366

[cameronbourgeois]

I don't know why my comment was marked as spam 🤔 ?