From: akr@...
Date: 2020-04-10T07:06:50+00:00
Subject: [ruby-core:97778] [Ruby master Bug#16740] Deprecating and removing the broken Process.clock_getres

Issue #16740 has been updated by akr (Akira Tanaka).

Status changed from Open to Rejected

We discussed this issue at a Ruby developer meeting.
https://bugs.ruby-lang.org/issues/16693

We don't want to remove the method.

(1) Removing a method is incompatible.

(2) Even if OS implementation of clock_getres is buggy, it is standardized in SUS and future OS may have better implementation.


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Bug #16740: Deprecating and removing the broken Process.clock_getres
https://bugs.ruby-lang.org/issues/16740#change-84993

* Author: Eregon (Benoit Daloze)
* Status: Rejected
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
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clock_getres(2) is incorrect (doesn't match the actual resolution for many clocks), buggy (e.g. can return negative values) on almost all platforms and for almost all clock_id.

This is an observation based running specs for it:
https://github.com/ruby/spec/blob/ec844797a51a017ebc93af833e421362b4b24a17/core/process/clock_getres_spec.rb
https://github.com/ruby/spec/blob/ec844797a51a017ebc93af833e421362b4b24a17/core/process/fixtures/clocks.rb#L19-L59

See how many exceptions there are.
And that's not all, even CLOCK_MONOTONIC on Linux is buggy: https://github.com/ruby/actions/runs/395166997#step:16:155

My conclusion is this API is unusable for any purpose.
If people want to know the resolution for clock_gettime(), they need to call it repetitively and see how precise it is.
I will remove the "matches the clock in practice" specs for clock_getres() as I'm tired to maintain them.
But I think we should remove this impossible-to-use correctly API, because it's fundamentally broken on all platforms.

So I propose to deprecate and remove this API, because I believe it harms more than it helps for Rubyists.

Kernel hackers which want to use that function can always call it via Fiddle/FFI, but it shouldn't be a proper Ruby API since it's so broken at the OS level.



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