Improve compatibility of RUBY_PLATFORM

[chrisseaton]

Shopify#1

@eightbitraptor

[graalvmbot]

Hello Matt Valentine-House, thanks for contributing a PR to our project!

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[chrisseaton]

Matt is a Shopify employee.

[eregon]

Thank you for the PR!

From https://github.com/eregon/actions-shell/runs/327245855, RUBY_PLATFORM is

• on Linux: x86_64-linux
• on macOS: x86_64-darwin18
• on Windows: x64-mingw32

So the kernel version only seems used on macOS.

[chrisseaton]

Have you taken a look at --with-os-version-style=? We think major is the default (but I'm not used to reading these Autoconf files). We're trying to match a default build. We found gems in the wild depending on this https://github.com/freerange/mocha/blob/master/lib/mocha/macos_version.rb.

[eregon]

The value of RUBY_PLATFORM seems to come from autoconf's $target_os.
In any case, let's match MRI, so on macOS we need the version as this PR does, but on Linux (and I think for other platforms too) we shouldn't have it in RUBY_PLATFORM:
The added spec does not pass on MRI on Linux:

$ jt -u ruby test spec/ruby/core/builtin_constants/builtin_constants_spec.rb
ruby 2.6.2p47 (2019-03-13 revision 67232) [x86_64-linux]
                                                                                             
1)
RUBY_PLATFORM contains the current kernel major version FAILED
Expected "x86_64-linux" =~ /5/
to be truthy but was nil
/home/eregon/code/truffleruby-ws/truffleruby/spec/ruby/core/builtin_constants/builtin_constants_spec.rb:41:in `block (3 levels) in <top (required)>'
/home/eregon/code/truffleruby-ws/truffleruby/spec/ruby/core/builtin_constants/builtin_constants_spec.rb:33:in `<top (required)>'

[eightbitraptor]

Thanks for the feedback @eregon and @chrisseaton - I've pushed a commit that restricts this functionailty to Darwin based OS's only now, and uses the original behaviour for other systems. I've run the tests locally on both Ubuntu 18.04 and macOS 10.15.2 so I'm hopeful 👍

I think it's important to note that we're only replicating the default behaviour of MRI at this stage. I don't have much context about what the --with-os-version-style flag is used for, only that it's possible to compile Ruby with a different setting.

Thanks both.

[eregon]

Thanks for the update, I'll integrate the PR.

https://github.com/freerange/mocha/blob/master/lib/mocha/macos_version.rb

FWIW, a better way to do that seems to be Etc.uname[:release].

I guess 99+% don't set --with-os-version-style, so let's not worry about until we find a problem related to it.

[graalvmbot]

Matt Valentine-House has signed the Oracle Contributor Agreement (based on email address matt -(at)- eightbitraptor -(dot)- com) so can contribute to this repository.

[eregon]

@chrisseaton Could you remove the last commit?
I did the formatting and a few small fixes on top, so rebasing is not easy and the PR already passed CI.

The issue is that if there is an extra commit on the GitHub PR it won't be regarded as "merged" on GitHub (but just closed).

To avoid this kind of issue I add the label in-ci when creating the internal PR.
The label in-ci means the PR is being tested in the internal CI and no new commits should be pushed on the GitHub PR.

[chrisseaton]

Done.

[eregon]

@eightbitraptor @chrisseaton Merged in 83abd2e with a few tweaks, thank you for the PR!