From: eregontp@...
Date: 2020-01-06T18:22:12+00:00
Subject: [ruby-core:96693] [Ruby master Feature#8215] Support accessing Fiber-locals and backtraces for a Fiber

Issue #8215 has been updated by Eregon (Benoit Daloze).


`Fiber#[]` and `Fiber#[]=` sounds fine, but what if somebody does:

`some_fiber = Fiber.new { ... }; Thread.new { some_fiber[:fiber_local] }`?

I think that should raise or not be possible.
If it would return the value, it would imply synchronization on every access to fiber locals which seems unfortunate.

By making the API `Fiber.[]`, we can avoid that entirely and have true fiber-locals, which can only be accessed by that Fiber:
```ruby
Fiber[:my_fiber_local] = 42
value = Fiber[:my_fiber_local]
# no way to access fiber locals of another Fiber
```

I think for new APIs we should take the chance to make them only possible to use correctly.
We could even finally have Fiber and Thread local in a consistent way:
```ruby
# access Fiber-local
Fiber[:my_fiber_local]
# access Thread-local
Thread[:my_thread_local]
```

----------------------------------------
Feature #8215: Support accessing Fiber-locals and backtraces for a Fiber
https://bugs.ruby-lang.org/issues/8215#change-83678

* Author: halorgium (Tim Carey-Smith)
* Status: Assigned
* Priority: Normal
* Assignee: ioquatix (Samuel Williams)
* Target version: 
----------------------------------------
=begin
As part of debugging celluloid, I have been wanting to diagnose where the Fibers are running and their various locals.

I would expect the following to work.

  Thread.current[:key] = "outside"
  fiber = Fiber.new do
    Thread.current[:key] = "inside"
    Fiber.yield
  end
  fiber.resume
  fiber[:key] == "inside" # true
  fiber.backtrace # ...

I also wonder whether (({Fiber#[]})) should be implemented, so (({Fiber.current[:key]})) is possible.

For reference, here is the issue on the rubinius issue tracker: ((<"github/rubinius/rubinius/2200"|URL:https://github.com/rubinius/rubinius/issues/2200>))
=end


---Files--------------------------------
0001-cont.c-fiber-local-accessors.patch (2.94 KB)


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