Erlang/OTP 20.1 is released

September 27, 2017 · by Henrik Nord

Erlang/OTP 20.1 is the first service release for the 20 major release. The service release contains mostly bug fixes and characteristics improvements but also some new features.

Some highlights for 20.1

  • crypto, public_key: Extend crypto and public_key functions sign and verify with:
  • support for RSASSA-PS padding for signatures and for saltlength setting
  • X9.31 RSA padding.
  • sha, sha224, sha256, sha384, and sha512 for dss signatures as mentioned in NIST SP 800-57 Part 1.
  • ripemd160 to be used for rsa signatures.
  • A new tuple in crypto:supports/0 reports supported MAC algorithms.
  • diameter:
  • Add service option decode_format to allow incoming messages to be decoded into maps instead of records.
  • Decode performance has been improved.
  • Add service/transport option avp_dictionaries to give better support for dictionaries only defining AVPs.
  • erts: Upgraded the ERTS internal PCRE library from version 8.40 to version 8.41.
  • erts, kernel, tools: Profiling with lock counting can now be fully toggled at runtime in the lock counting emulator (-emu_type lcnt). Everything is enabled by default to match the old behavior, but specific categories can be toggled at will with minimal runtime overhead when disabled. Refer to the documentation on lcnt:rt_mask/1 for details.

lcnt:collect and lcnt:clear will no longer block all other threads in the runtime system. This makes it possible to run the lock counting under heavier load.

  • erts: The zlib module has been refactored and all its operations will now yield appropriately, allowing them to be used freely in concurrent applications.
  • erts, tools: Add erlang:iolist_to_iovec/1, which converts an iolist() to an erlang:iovec(), which is suitable for use with enif_inspect_iovec().
  • erts: Add new nif API functions for managing an I/O Queue. The added functions are: enif_ioq_create()enif_ioq_destroy()enif_ioq_enq_binary(), enif_ioq_enqv()enif_ioq_deq()enif_ioq_peek()enif_inspect_iovec()enif_free_iovec()
  • observer/crashdump_viewer:
  • Reading of crash dumps with many binaries is optimized.
  • A progress bar is shown when the detail view for a process is opened.
  • The cdv script now sets ERL_CRASH_DUMP_SECONDS=0 to avoid generating a new crash dump from the node running the Crashdump Viewer.
  • observer: Add system statistics and limits to frontpage in observer.
  • public_key, ssl**: Improved error propagation and reports
  • ssh: A new option modify_algorithms is implemented. It enables specifying changes on the default algorithms list. See the reference manual and the SSH User’s Guide chapter “Configuring algorithms in SSH”.
  • tools/xref: The predefined Xref analysis locals_not_used now understands the -on_load() attribute and does not report unused functions.
  • tools/fprof: When sampling multiple processes and analyzing with totals set to true, the output now sums together all caller and callee entries which concerns the same function. Previous behaviour was to report each contributing entry separately.

You can find the README and the full listing of changes for this service release at

The source distribution and binary distributions for Windows can be downloaded from

Note: To unpack the TAR archive you need a GNU TAR compatible program.

For installation instructions please consult the README file that is part of the distribution.

The Erlang/OTP source can also be found at GitHub on the official Erlang repository, with tag OTP-20.1

The on-line documentation can be found at: You can also download the complete HTML documentation or the Unix manual files

Please report any new issues via Erlang/OTPs public issue tracker

We want to thank all of those who sent us patches, suggestions and bug reports!

Thank you!

The Erlang/OTP Team at Ericsson