Erlang OTP 22.0-rc1 is available for testing!

February 13, 2019 · by Henrik Nord

OTP 22 Release Candidate 1 #

This is the first of three planned release candidates before the OTP 22 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, as it lets us know that the release candidate got some testing.

Erlang/OTP 22 is a new major release with new features and improvements as well as incompatibilities.

Potential Incompatibilities #

  • gen_* behaviours: If logging of the last N messages through sys:log/2,3 is active for the server, this log is included in the terminate report.
  • New element, Opts, can now be included in a rel tuple in the reltool release specific configuration format: {rel, Name, Vsn, RelApps, Opts}.
  • All external pids/ports/refs created by erlang:list_to_pid and similar functions now compare equal to any other pid/port/ref with same number from that node.
  • The old legacy erl_interface library is deprecated as of OTP 22, and will be removed in OTP 23. This does not apply to the ei library.
  • VxWorks is deprecated as of OTP 22 and will be removed in OTP 23.

Known problems #

Native code generation does not work for all modules due to new BEAM instructions not supported by HiPE the native compiler. However, dialyzer’s automatic compilation to native code still works. Building OTP with the configure option enable-native-libs will not work in this release candidate.

Highlights #

Erts: #

  • Support for Erlang Distribution protocol to split the payload of large signals into several fragments.
  • ETS option write_concurrency now also effects and improves scalability of ordered_set tables.
  • The length/1 BIF used to calculate the length of the list in one go without yielding, even if the list was very long. Now it yields when called with long lists.
  • A new (still experimental) module socket is introduced. It is implemented as a NIF and the idea is that it shall be as “close as possible” to the OS level socket interface.

Compiler: #

  • The compiler has been rewritten to internally use an intermediate representation based on Static Single Assignment (SSA). The new intermediate representation makes more optimizations possible. * The binary matching optimizations are now applicable in many more circumstances than before.
  • Type optimizations are now applied across local function calls, and will remove a lot more redundant type tests than before.
  • All compiler options that can be given in the source file can now be given in the option list on the command line for erlc.

Standard libraries: #

  • Cover now uses the counters module instead of ets for updating counters. The new function cover:local_only/0 allows running Cover in a restricted but faster local-only mode. The increase in speed will vary depending on the type of code being cover-compiled, as an example the compiler test suite runs more than twice as fast with the new Cover.
  • SSL now uses the new logger API, including log levels and verbose debug logging.

For more details see

Pre built versions for Windows can be fetched here:

Online documentation can be browsed here:

The Erlang/OTP source can also be found at GitHub on the official Erlang repository:


Thank you for all your contributions!