Erlang/OTP 26.0-rc2 is the second release candidate of three before the OTP 26.0 release. The release candidate 2 fixes some bugs found in the first release candidate and there are also a few additional features.

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.

All artifacts for the release can be downloaded from the Erlang/OTP Github release and you can view the new documentation at https://erlang.org/documentation/doc-14.0-rc2/doc/. You can also install the latest release using kerl like this: kerl build 26.0-rc2 26.0-rc2.

Erlang/OTP 26 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 RC2

Parsetools

• Leex has been extended with optional column number support.

Stdlib

• The family of enumeration functions in module lists has been extended with
  enumerate/3 that allows a step value to be supplied.
• Update Unicode to version 15.0.0.
• proc_lib:start*/* has become synchronous when the
  started process fails. This requires that a failing
  process use a new function proc_lib:init_fail/2,3, or
  exits, to indicate failure. All OTP behaviours have
  been fixed to do this.

Dialyzer

• Added the new built-in type dynamic() introduced in EEP 61, PR introducing EEP 61 improving support for gradual type checkers.

SSL

• Change the client default verify option to verify_peer.
  Note that this makes it mandatory to also supply trusted CA certificates or explicitly set
  verify to verify_none. This also applies when using the so called
  anonymous test cipher suites defined in TLS versions pre TLS-1.3.

Highlights RC1

The Shell

There are a lot of new features and improvements in the Erlang shell:

• auto-complete of variables, record names, record fields names, map keys, function parameter types and filenames.
• Open external editor in the shell to edit
  the current expression.
• defining records (with types), functions, specs and types in the shell.

New terminal

• The TTY/terminal subsystem has been rewritten.
  Windows users will notice that erl.exe has the same
  functionality as a normal Unix shell and that werl.exe is just a
  symlink to erl.exe. This makes the Windows Erlang terminal
  experience identical to that of Unix.

Compiler and JIT optimizations:

• Creation and matching of binaries with segments of fixed sizes have been optimized.

• Creation and matching of UTF-8 segments have been optimized.

• Appending to binaries has been optimized.

• The compiler and JIT now generate better code for creation of small maps where all keys
  are literals known at compile time.

• Thanks to the optimizations above the performance of the base64 module has been
  significantly improved. For example, on an x86_64 system with the JIT both encode and
  decode are almost three times faster than in Erlang/OTP 25.

Maps

• Map comprehensions as suggested in EEP 58 has now been
  implemented.

• Some map operations have been optimized by changing the
  internal sort order of atom keys. This changes the
  (undocumented) order of how atom keys in small maps are
  printed and returned by maps:to_list/1 and maps:next/1.
  The new order is unpredictable and may change between
  different invocations of the Erlang VM.

• Introducing the new function maps:iterator/2 for creating an interator
  that return the map elements in a deterministic order.
  There are also new modifiers k and K for the format
  string in io:format() to support printing map elements
  ordered.

Dialyzer

• Dialyzer has a new incremental mode that be invoked by
  giving the --incremental option when running Dialyzer.
  This new incremental mode is likely to become the
  default in a future release.

Misc ERTS, Stdlib, Kernel, Compiler

• Multi time warp mode is now enabled by default.
  This assumes that all code executing on the system is
  time warp safe.

• Support for UTF-8 atoms and strings in the NIF
  interface including new functions enif_make_new_atom,
  enif_make_new_atom_len and enif_get_string_length.

• The BIFs min/2 and max/2 are now allowed to be used in
  guards and match specs.

• Improved the selective receive optimization, which can
  now be enabled for references returned from other
  functions. This greatly improves the performance of
  gen_server:send_request/3, gen_server:wait_response/2,
  and similar functions.

• New trace feature call_memory. Similar to call_time
  tracing, but instead of measure accumulated time in
  traced functions it measures accumulated heap space
  consumed by traced functions. It can be used to compare
  how much different functions are contributing to
  garbage collection being triggered.

• It is no longer necessary to enable a feature in the
  runtime system in order to load modules that are using
  it. It is sufficient to enable the feature in the
  compiler when compiling it.

• inet:setopts/2 has got 3 new options: reuseport, reuseport_lb and exclusiveaddruse.

• Fix so that -fno-omit-frame-pointer is applied to all
  of the Erlang VM when using the JIT so that tools, such
  as perf, can crawl the process stacks.

• In the lists module, the zip family of functions now takes
  options to allow handling lists of different lengths.

• Added the zip:zip_get_crc32/2 function to retrieve the
  CRC32 checksum from an opened ZIP archive.
  gen_server optimized by caching callback functions

• The modules Erlang DNS resolver inet_res and helper
  modules have been updated for RFC6891; to handle OPT RR
  with DNSSEC OK (DO) bit.

• Introduced application:get_supervisor/1.

• Cache OTP boot code paths, to limit how many folders
  that are being accessed during a module lookup. Can be
  disabled with -cache_boot_path false.

SSL

• Support for Kernel TLS (kTLS), has been added to the
  SSL application, for TLS distribution (-proto_dist
inet_tls), the SSL option {ktls, true}.

• Improved error checking and handling of ssl options.

• Mitigate memory usage from large certificate chains by
  lowering the maximum handshake size. This should not
  effect the common cases, if needed it can be configured
  to a higher value.

• For security reasons the SHA1 and DSA
  algorithms are no longer among the default values.

• Add encoding and decoding of use_srtp hello extension
  to facilitate for DTLS users to implement SRTP
  functionality.

For more details about new features and potential incompatibilities see the readme