OTP 29.0-rc1 #

Erlang/OTP 29.0-rc1 is the first release candidate of three before the OTP 29.0 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 at https://github.com/erlang/otp/issues or by posting to Erlang Forums.

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-17.0-rc1/doc. You can also install the latest release using kerl like this:

kerl build 29.0-rc1 29.0-rc1.

Erlang/OTP 29 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!

General #

• In the default code path for the Erlang system, the current working directory (.) is now in the last position instead of the first.

• There is no longer a 32-bit Erlang/OTP build for Windows.

New language features #

• Native records as described in EEP-79 has been implemented. A native record is a data structure similar to the traditional tuple-based records, except that is a true data type. Native records are considered experimental in Erlang/OTP 29 and possibly also in Erlang/OTP 30.

• The new is_integer/3 guard BIF makes it possible to easily verify that a value is both an integer and within a certain range. For example: is_integer(I, 0, 100)

• Multi-valued comprehensions according to EEP 78 are now supported. For example, [-I, I || I <- [1, 2, 3]] will produce [-1,1,-2,2,-3,3].

• By enabling the compr_assign feature, it is now possible to bind variables in a comprehensions. For example: [H || E <- List, H = erlang:phash2(E), H rem 10 =:= 0]

Compiler and JIT improvements #

• In the documentation for the [compile] module, there is now a section with recommendations for implementors of languages running on the BEAM.

• The JIT now generates better code for matching or creating binaries with multiple little-endian segments.

• The compiler will generate more efficient code for map comprehensions with constant values that don’t depend on the generator. Example: #{K => 42 || K <- List}

Compiler warnings #

There are several new compiler warnings enabled by default. For each such warning, there is an option to disable it.

• There will now be a warning when using the catch operator, which has been deprecated for a long time. It is recommended to instead use try…catch but is also possible to disable the warning by using the nowarn_deprecated_catch option.

• There will now be a warning when exporting variables out of a subexpression. For example: file:open(File, AllOpts = [write, {encoding,utf8}]). This warning can be disabled using the nowarn_export_var_subexpr compiler option.

• The compiler will now warn for uses of the and and or operators. This warning can be disabled using the nowarn_obsolete_bool_op compiler option.

• The compiler will now warn for matches such as {a,B} = {X,Y}, which is better written as {a=X,B=Y}. This warning can be disabled using the nowarn_match_alias_pats option.

For a long time, there has been a warning for using the obsolete guard tests (such as list(L) instead of is_list(L). In Erlang/OTP 30, the old guards will be removed from the language.

STDLIB #

• There are new functions for randomly permutating a list: rand:shuffle/1 and rand:shuffle_s/2.

SSH #

• The default key exchange algorithm is now mlkem768x25519-sha256, a hybrid quantum-resistant algorithm combining ML-KEM-768 with X25519. This provides protection against both classical and quantum computer attacks while maintaining backward compatibility through automatic fallback to other algorithms when peers don’t support it.

For more details about new features and potential incompatibilities see the README.