os: add kernel_version

[SeekingMeaning]

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This allows for e.g. `uname -r`.split(".").first in homebrew/core/gcc to be replaced with OS.kernel_version.major

Uses:

• `uname -r`.split(".").first → OS.kernel_version.major
• `uname -r`.to_i → OS.kernel_version.major
• `uname -r`.chomp → OS.kernel_version
• shell_output("uname -r").strip → OS.kernel_version
• Utils.safe_popen_read("uname", "-r").chomp → OS.kernel_version

[reitermarkus]

Maybe call this kernel_version?

[MikeMcQuaid]

This allows for e.g. `uname -r`.split(".").first in homebrew/core/gcc to be replaced with OS.uname_version.major

Any new utility methods that are used by formulae should be used by at least 3 (ideally a lot more than that) before we add them. I'm not sure I see the advantage here; it's not even actually shorter in this case?

[SeekingMeaning]

Any new utility methods that are used by formulae should be used by at least 3 (ideally a lot more than that) before we add them.

About 17 formulae use uname -r (including versioned gcc's)
See https://github.com/Homebrew/homebrew-core/search?q=%22uname+-r%22

it's not even actually shorter in this case?

Hehe, you might have a point 😆 It's longer but I think it's more clear

[Bo98]

I'm not convinced the --build flag is needed in the case of GCC. That's usually indicative of a bad config.guess.

[SeekingMeaning]

Slightly off-topic, latest GNU config.guess supports arm64 Darwin now: https://git.savannah.gnu.org/gitweb/?p=config.git;a=commitdiff;h=2593751ef276497e312d7c4ce7fd049614c7bf80

[MikeMcQuaid]

Uses:

• `uname -r`.split(".").first → OS.kernel_version.major
• `uname -r`.to_i → OS.kernel_version.major
• `uname -r`.chomp → OS.kernel_version
• shell_output("uname -r").strip → OS.kernel_version
• Utils.safe_popen_read("uname", "-r").chomp → OS.kernel_version

You've changed my mind: I like these.

[MikeMcQuaid]

• What if uname -r fails? (should probably raise)
• Utils.popen_read might be a nicer fit here.

[MikeMcQuaid]

Also: could this get a unit test.

[SeekingMeaning]

• What if uname -r fails? (should probably raise)

I'm not certain, but after checking in brew irb it seems that uname would print an error message (if it has a message to print) and then `uname -r` would return an empty string, so pretty much the same as Utils.popen_read but without silencing error messages

[reitermarkus]

Doesn't Version.create return Version::NULL?

[SeekingMeaning]

That would be Version.parse but that might be excessive in this case since uname -r already returns a valid version string

[reitermarkus]

Suggested change

	@kernel_version ||= if output = Utils.popen_read("uname", "-r").chomp.presence
	@kernel_version ||= if output = Utils.safe_popen_read("uname", "-r").chomp.presence

I don't think this should be able to fail, right?

[SeekingMeaning]

Whoops, I forgot about that. I was just preserving the functionality of OS::Linux::Kernel.version since that's where this came from

We probably won't need the if since safe_popen_read raises an error anyways

[SeekingMeaning]

I'm not sure if we want to preserve this or not

[MikeMcQuaid]

I think so unless you can verify it's unused in e.g. linuxbrew-core in which case: 🔥 it.

[SeekingMeaning]

Looks like this is only used in brew in extend/os/linux/diagnostic (including below_minimum_version?):

% cd $(brew --repo)
% grep -r 'Linux::Kernel' *
Library/Homebrew/test/os/linux/diagnostic_spec.rb:    allow(OS::Linux::Kernel).to receive(:below_minimum_version?).and_return(true)
Library/Homebrew/extend/os/linux/diagnostic.rb:        return unless OS::Linux::Kernel.below_minimum_version?
Library/Homebrew/extend/os/linux/diagnostic.rb:          Your Linux kernel #{OS::Linux::Kernel.version} is too old.
Library/Homebrew/extend/os/linux/diagnostic.rb:          We only support kernel #{OS::Linux::Kernel.minimum_version} or later.

% cd $(brew --repo homebrew/core)
% git remote get-url origin
https://github.com/Homebrew/linuxbrew-core
% grep 'Linux::Kernel' Formula/*
% grep 'Linux::' Formula/*
Formula/clang-format.rb:    if Formula["glibc"].any_version_installed? || OS::Linux::Glibc.system_version < Formula["glibc"].version
Formula/glibc.rb:    Glibc.version >= OS::Linux::Glibc.system_version
Formula/glibc.rb:      Your system's glibc version is #{OS::Linux::Glibc.system_version}, and Homebrew's glibc version is #{Glibc.version}.
Formula/llvm@7.rb:    if Formula["glibc"].any_version_installed? || OS::Linux::Glibc.system_version < Formula["glibc"].version
Formula/llvm@8.rb:    if Formula["glibc"].any_version_installed? || OS::Linux::Glibc.system_version < Formula["glibc"].version
Formula/llvm@9.rb:    if Formula["glibc"].any_version_installed? || OS::Linux::Glibc.system_version < Formula["glibc"].version
Formula/llvm.rb:    if Formula["glibc"].any_version_installed? || OS::Linux::Glibc.system_version < Formula["glibc"].version

[MikeMcQuaid]

Cool! I think you can 🔥 then.

[SeekingMeaning]

So uh, what does 🔥 mean in this context? 😅

[MikeMcQuaid]

Sorry: burn it down (i.e. delete it)

[MikeMcQuaid]

Perfect!