Ruby 2.4.0-preview3 Released

We are pleased to announce the release of Ruby 2.4.0-preview3.

Ruby 2.4.0-preview3 is the third preview of Ruby 2.4.0. This preview3 is released to get feedback from the community. Feel free to send feedback since you can still influence the features.

Introduce hash table improvement (by Vladimir Makarov)

Improve the internal structure of hash table (st_table) by introducing open addressing and an inclusion order array. This improvement has been discussed with many people, especially with Yura Sokolov.

Binding#irb: Start a REPL session similar to binding.pry

While you are debugging, you may often use p to see the value of variables. With pry you can use binding.pry in your application to launch a REPL and run any Ruby code. r56624 introduces binding.irb which behaves like that with irb.

Unify Fixnum and Bignum into Integer

Though ISO/IEC 30170:2012 doesn’t specify details of the Integer class, Ruby had two visible Integer classes: Fixnum and Bignum. Ruby 2.4 unifies them into Integer. All C extensions which touch the Fixnum or Bignum class need to be fixed.

See also the ticket and akr’s slides.

String supports Unicode case mappings

String/Symbol#upcase/downcase/swapcase/capitalize(!) now handle Unicode case mappings instead of only ASCII case mappings.

Performance improvements

Ruby 2.4 also contains the following performance improvements including language changes:

Array#max, Array#min

[x, y].max and [x, y].min are optimized to not create a temporary array under certain conditions.


Added Regexp#match?, which executes a regexp match without creating a back reference object and changing $~ to reduce object allocation.

Other performance improvements


Thread#report_on_exception and Thread.report_on_exception

Ruby ignores exceptions in threads unless another thread explicitly joins them. With report_on_exception = true, you can notice if a thread has died due to an unhandled exception.

Send us feedback what should be the default for report_on_exception and about report-on-GC, which shows a report when a thread is garbage collected without join.

Thread deadlock detection now shows threads with their backtrace and dependency

Ruby has deadlock detection around waiting threads, but its report doesn’t include enough information for debugging. Ruby 2.4’s deadlock detection shows threads with their backtrace and dependent threads.

Try and enjoy programming with Ruby 2.4.0-preview3, and send us feedback!

Other notable changes since 2.3

See NEWS and ChangeLog for details.

With those changes, 2470 files changed, 283051 insertions(+), 64902 deletions(-) since Ruby 2.3.0!



    SIZE:   12615328 bytes
    SHA1:   fefe49f6a7d5b642936c324f3b05aaac827355db
    SHA256: 305a2b2c627990e54965393f6eb1c442eeddfa149128ccdd9f4334e2e00a2a52
    SHA512: 6602c65a7b1e3bc680acc48217108f4335e84fdd74a9cf06f2e2f9ad00a2fccacf9fa035a912bc9d5cc3f0c7a5e21475971dfac37b0364311ef3645f25c7ddf9

    SIZE:   15758023 bytes
    SHA1:   f6a6ec9f7fedad0bf4efee2e42801cc963f60dca
    SHA256: c35fe752ccfabf69bf48e6aab5111c25a05938b428936f780638e2111934c9dd
    SHA512: 68556d5252b6813b4c8eeba32733e940207f80694b5c5d20e69bf01eb52929ed2466496b05a895a5ad4831d430695e17624eb35b728b2d4d7cf02df756ac48b4

    SIZE:   9957596 bytes
    SHA1:   66592b1a52f985638d639e7c3dd6bdda4e0569d0
    SHA256: b14be2b5c80bff0d6894ae2b37afdb17a968413e70236ec860f3e2d670b4c317
    SHA512: 5be20f0b2609745790c2b22f2228e69a840f63c34a117a1f95fd5436af211f0a6db2758d513d3e095a2d97c53c80793579cb2a1e00e70cf72c487a88c4a40d33

    SIZE:   17579012 bytes
    SHA1:   15d08cff952da3844ae54887b7f74b12d47c9ee2
    SHA256: b95a8f67fb7d6e852db77c5660c8878c14d68eb72c5501dac164a7e640ecb06e
    SHA512: fa15e1b7ab0cab56c9a580e1b1e2fee250ee0b9c59546079675a1931a36e37131bd37d64033c75e05d8e9d9fcc33ce7850254d3acaca2136cf3bd08b070244f0

Release Comment

See also the release schedule and other information: