Found because `json` has a bad example in its test suite.
This implementation still offers better encapsulation.

This reverts commit 28e60b00.

This reverts commit e026e186..12a2e32d.

[Fixes https://bugs.ruby-lang.org/issues/15409]

This reverts commits:
dc38e99813
22c082fcfd
b499e0f9ff
58e5876646

Add test for overriden private methods

[Fixes https://bugs.ruby-lang.org/issues/12136]

fstring pool should be sync with other Ractors.

vm_sync.h does not need to include vm_core.h and ractor_pub.h.

signal can interrupt Ractor.select, but if there is no exception,
Ractor.select should restart automatically.

https://github.com/ruby/tmpdir/commit/af7b020a89

https://github.com/ruby/tmpdir/commit/84684d80f9

https://github.com/ruby/tmpdir/commit/f335f2c23e

https://github.com/ruby/tmpdir/commit/414c00ebe6

https://github.com/ruby/tmpdir/commit/ac12877306

This is not "diff", but show expected and actual results both,
just to get rid of `NoMethodError` when an assertion failed.

Most gzip tools support concatenated gz streams in a gz file. This
offers a way to handle such gz files in Ruby.

Fixes [Bug #9790]
Fixes [Bug #11180]
Fixes [Bug #14804]

https://github.com/ruby/zlib/commit/e2ce56de7d

https://github.com/ruby/net-smtp/commit/b706942392

The helo argument is not important, but the helo argument must be
specified to specify the user and secret arguments.
If helo, user, secret, and authtype arguments are keyword arguments,
it is not necessary to specify the helo argument.

https://github.com/ruby/net-smtp/commit/269774deac

In tlsconnect(), the host name is checked when
@ssl_context.verify_mode is not OpenSSL::SSL::VERIFY_NONE, but the
verify_mode of @ssl_context generated by default is nil.

https://github.com/ruby/net-smtp/commit/bde75a15b5

https://github.com/ruby/erb/commit/660255cf24

* Enables Mutex to be used as synchronization between multiple Fibers
  of the same Thread.
* With a Fiber scheduler we can yield to another Fiber on contended
  Mutex#lock instead of blocking the entire thread.
* This also makes the behavior of Mutex consistent across CRuby, JRuby and TruffleRuby.
* [Feature #16792]