OTP 25.0-rc1 (Release Candidate 1) has been released

Wed Feb 16 16:26:12 CET 2022

OTP 25.0-rc1

Erlang/OTP 25.0-rc1 is the first release candidate of three before the OTP
25.0 release.

The intention with this release is to get feedback from our users. All
feedback is welcome, even if it is only to say that it works for you.
We encourage users to try it out and give us feedback either by creating an
issue here https://github.com/erlang/otp/issues or by posting to
Erlangforums <https://erlangforums.com> or the mailing list
erlang-questions@REDACTED

All artifacts for the release can be downloaded from the Erlang/OTP Github
<https://github.com/erlang/otp/releases/tag/OTP-25.0-rc1> release and you
can view the new documentation at
https://erlang.org/documentation/doc-13.0-rc1/doc/. You can also install
the latest release using kerl <https://github.com/kerl/kerl> like this: kerl
build 25.0-rc1 25.0-rc1.

Erlang/OTP 25 is a new major release with new features, improvements as
well as a few incompatibilities. Some of the new features are highlighted
below.

Many thanks to all contributors!

Below are some highlights of the release:
Highlights erts & jit

   - The JIT now works for 64-bit ARM processors.
   - The JIT now does type-based optimizations based on type
   information in the BEAM files.
   - Improved the JIT's support for external tools like perf
   and gdb, allowing them to show line numbers and even
   the original Erlang source code when that can be found.

erts, stdlib, kernel

   -

   Users can now configure ETS tables with the
   {write_concurrency, auto} option. This option forces
   tables to automatically change the number of locks that
   are used at run-time depending on how much concurrency
   is detected. The {decentralized_counters, true} option
   is enabled by default when {write_concurrency, auto} is
   active.

   Benchmark results comparing this option with the other
   ETS optimization options are available here:
   benchmarks <https://erlang.org/bench/ets_bench_result_lock_config.html>.
   -

   To enable more optimizations, BEAM files compiled with
   OTP 21 and earlier cannot be loaded in OTP 25.
   -

   The signal queue of a process with
   the process flag message_queue_data=off_heap has been optimized to
   allow parallel reception of signals from multiple processes.
   This can improve performance when many processes are sending in parallel
   to
   one process. See benchmark
   <https://erlang.org/bench/sigq_bench_result.html>.
   -

   The Erlang installation directory is now relocatable on
   the file system given that the paths in the
   installation's RELEASES file are paths that are
   relative to the installations root directory.
   -

   A new option called short has been added to the
   functions erlang:float_to_list/2 and
   erlang:float_to_binary/2. This option creates the
   shortest correctly rounded string representation of the
   given float that can be converted back to the same
   float again.
   -

   Introduction of quote/1 and unquote/1 functions in
   the uri_string module - a replacement for the deprecated functions
   http_uri:encode
   and http_uri:decode.
   -

   The new module peer supersedes the slave module. The
   slave module is now deprecated and will be removed in OTP 27.
   -

   global will now by default prevent
   overlapping partitions due to network issues. This is done by
   actively disconnecting from nodes that reports that
   they have lost connections to other nodes. This will
   cause fully connected partitions to form instead of
   leaving the network in a state with overlapping
   partitions.

   It is possible to turn off the new behavior by setting the
   the kernel configuration parameter prevent_overlapping_partitions to
   false.
   Doing this will retain the same behavior as in OTP 24 and earlier.
   -

   The format_status/2 callback for gen_server, gen_statem
   and gen_event has been deprecated in favor of the new
   format_status/1 callback.

   The new callback adds the possibility to limit and
   change many more things than the just the state.
   -

   The timer module has been modernized and made more
   efficient, which makes the timer server less
   susceptible to being overloaded. The timer:sleep/1
   function now accepts an arbitrarily large integer.

Compiler

   -

   The maybe ... end construction as proposed in EEP-49
   <https://www.erlang.org/eeps/eep-0049>
   has been implemented. It can simplify complex code
   where otherwise deeply nested cases would have to be
   used.

   To enable maybe, give the option {enable,maybe_expr} to
   the compiler. The exact option to use will change in a coming release
   candidate and then it will also be possible to
   use from inside the module being compiled.
   -

   When a record matching or record update fails, a
   {badrecord, ExpectedRecordTag} exception used to be
   raised. In this release, the exception has been changed
   to {badrecord, ActualValue}, where ActualValue is the
   value that was found instead of the expected record.
   -

   Add compile attribute -nifs() to empower compiler and loader with
   information about which functions may be overridden as NIFs by
   erlang:load_nif/2.
   -

   Improved and more detailed error messages when binary construction with
   the
   binary syntax fails.
   This applies both for error messages in the shell and for
   erl_error:format_exception/3,4.

Crypto

   - Add crypto:hash_equals/2 which is a constant time comparision of
   hashvalues.

Dialyzer

   - Optimize operations in the erl_types module. Parallelize the Dialyzer
   pass remote.
   - Added the missing_return and extra_return options to
   raise warnings when specifications differ from inferred
   types. These are similar to, but not quite as verbose
   as overspecs and underspecs.
   - Dialyzer now better understands the types for min/2,
   max/2, and erlang:raise/3. Because of that, Dialyzer
   can potentially generate new warnings. In particular,
   functions that use erlang:raise/3 could now need a spec
   with a no_return() return type to avoid an unwanted
   warning.

Misc

   - A new DEVELOPMENT HOWTO guide
   <https://github.com/erlang/otp/blob/master/HOWTO/DEVELOPMENT.md> has
   been added that
   describes how to build and test Erlang/OTP when fixing
   bugs or developing new functionality.
   - Testing has been
   added to the Github actions run for each opened PR so
   that more bugs are caught earlier when bug fixes and
   new features are proposed.

For more details about new features and potential incompatibilities see

   - https://erlang.org/download/otp_src_25.0-rc1.readme
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