New function filelib:ensure_path/1 will ensure that all directories for the given path exists
New functions groups_from_list/2 and groups_from_list/3 in the maps module
New functions uniq/1uniq/2 in the lists module
New PRNG added to the rand module, for fast pseudo-random numers.
compiler, kernel, stdlib, syntax_tools
Added support for selectable features as described in EEP-60.
Features can be enabled/disabled during compilation with options
(ordinary and +term) to erlc as well as with directives in the file.
Similar options can be used to erl for enabling/disabling features
allowed at runtime. The new maybe expression EEP-49
is fully supported as the feature maybe_expr.
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.
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.
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
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_feature,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.
Change format of feature options and directives for better consistency.
Options to erlc and the -compile(..) directive now has the format {feature,
feature-name, enable | disable}. The -feature(..) now
has the format -feature(feature-name, enable | disable).
crypto
Add crypto:hash_equals/2 which is a constant time comparision of hashvalues.
ssl
Introducing a new (still experimental) option {certs_keys,[cert_key_conf()]}.
With this a list of a certificates with their associated key may be
used to authenticate the client or the server. The
certificate key pair that is considered best and matches
negotiated parameters for the connection will be selected.
public_key
Functions for retrieving OS provided CA-certs added.
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
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.
