0MQ version 4.3.4 stable, released on 2020/01/17
================================================

* New DRAFT (see NEWS for 4.2.0) socket option:
  - ZMQ_PRIORITY will set the SO_PRIORITY socket option on the underlying
    sockets. Only supported on Linux.
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* Fixed #4113 - compilation errors on kFreeBSD and GNU/Hurd

* Fixed #4086 - excessive amount of socket files left behind in Windows TMP
                directory

* Fixed #4108 - regression that breaks using IPv6 link-local addresses on Linux

* Fixed #4078 - compilation errors on Android

* Fixed #4074 - compilation error with ulibc and libbsd

* Fixed #4060 - stack overflow on Windows x64

* Fixed #4051 - various compilation errors on Windows ARM 32bit

* Fixed #4043 - various compilation warnings with XCode

* Fixed #4038 - return value of zmq_ctx_get changed unintentionally


0MQ version 4.3.3 stable, released on 2020/09/07
================================================

* Security advisories:
  * CVE-2020-15166: Denial-of-Service on CURVE/ZAP-protected servers by
    unauthenticated clients.
    If a raw TCP socket is opened and connected to an endpoint that is fully
    configured with CURVE/ZAP, legitimate clients will not be able to exchange
    any message. Handshakes complete successfully, and messages are delivered to
    the library, but the server application never receives them.
    For more information see the security advisory:
    https://github.com/zeromq/libzmq/security/advisories/GHSA-25wp-cf8g-938m
  * Stack overflow on server running PUB/XPUB socket (CURVE disabled).
    The PUB/XPUB subscription store (mtrie) is traversed using recursive
    function calls. In the remove (unsubscription) case, the recursive calls are
    NOT tail calls, so even with optimizations the stack grows linearly with the
    length of a subscription topic. Topics are under the control of remote
    clients - they can send a subscription to arbitrary length topics. An
    attacker can thus cause a server to create an mtrie sufficiently large such
    that, when unsubscribing, traversal will cause a stack overflow.
    For more information see the security advisory:
    https://github.com/zeromq/libzmq/security/advisories/GHSA-qq65-x72m-9wr8
  * Memory leak in PUB server induced by malicious client(s) without CURVE/ZAP.
    Messages with metadata are never processed by PUB sockets, but the metadata
    is kept referenced in the PUB object and never freed.
    For more information see the security advisory:
    https://github.com/zeromq/libzmq/security/advisories/GHSA-4p5v-h92w-6wxw
  * Memory leak in client induced by malicious server(s) without CURVE/ZAP.
    When a pipe processes a delimiter and is already not in active state but
    still has an unfinished message, the message is leaked.
    For more information see the security advisory:
    https://github.com/zeromq/libzmq/security/advisories/GHSA-wfr2-29gj-5w87
  * Heap overflow when receiving malformed ZMTP v1 packets (CURVE disabled).
    By crafting a packet which is not valid ZMTP v2/v3, and which has two
    messages larger than 8192 bytes, the decoder can be tricked into changing
    the recorded size of the 8192 bytes static buffer, which then gets overflown
    by the next message. The content that gets written in the overflown memory
    is entirely decided by the sender.
    For more information see the security advisory:
    https://github.com/zeromq/libzmq/security/advisories/GHSA-fc3w-qxf5-7hp6

* Note for packagers: an external, self-contained sha1 library is now
  included in the source tree under external/sha1/ - it is licensed
  under BSD-3-Clause and thus it is fully compatible with libzmq's
  license.
  It is only used if WebSockets support is enabled, and if neither GnuTLS nor
  NSS are available.

* Note for packagers: an internal reimplementation of strlcpy is now included,
  for wider platform compatibility.
  libbsd can be used and is enabled by default if available instead of the
  internal implementation, for better security maintenance in distros.

* Note for packagers: ZeroMQConfig.cmake is now installed in the arch-dependent
  subdirectory - eg: /usr/lib/x86_64-linux-gnu/cmake/

* New DRAFT (see NEWS for 4.2.0) socket type:
  - ZMQ_CHANNEL is a thread-safe alternative to ZMQ_PAIR.
  See doc/zmq_socket.txt for details.

* New DRAFT (see NEWS for 4.2.0) socket option:
  - ZMQ_ONLY_FIRST_SUBSCRIBE will cause only the first part of a multipart
    message to be processed as a subscribe/unsubscribe message, and the rest
    will be forwarded as user data to the application.
  - ZMQ_RECONNECT_STOP will cause a connecting socket to stop trying to
    reconnect in specific circumstances. See the manpage for details.
  - ZMQ_HELLO_MSG to set a message that will be automatically sent to a new
    connection.
  - ZMQ_DISCONNECT_MSG to set a message that will be automatically received when
    a peer disconnects.
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* New DRAFT (see NEWS for 4.2.0) zmq_ctx_get_ext/zmq_ctx_set_ext APIs were added
  to allow enhancing the context options with variable data inputs.
  See doc/zmq_ctx_get_ext.txt and doc/zmq_ctx_set_ext.txt for details.

* New DRAFT (see NEWS for 4.2.0) transport options WS and WSS added for support
  of WebSockets (and secure WebSockets via TLS) via the ZWS 2.0 protocol.
  WSS requires the GnuTLS library for TLS support. ZMQ_WSS_ specific socket
  options were added to support TLS.
  WebSockets support is disabled by default if DRAFT APIs are disabled.

* New DRAFT (see NEWS for 4.2.0) socket type, PEER, which is thread safe and a
  related zmq_connect_peer function which atomically and thread-safely connects
  and returns a routing-id.

* New DRAFT (see NEWS for 4.2.0) zmq_msg_init_buffer API was added to allow
  the construction of a message by copying from an existing buffer.

* New DRAFT (see NEWS for 4.2.0) zmq_poller_size API was added to allow querying
  the number of sockets/fds registered in a zmq_poller.

* ZMTP 3.1 peers will receive subscribe/cancel on PUB/SUB via commands rather
  than using the first byte of the payload.

* zmq_z85_decode now checks that the input string's length is at least 5 characters
  and always a multiple of 5 as per API specification.

* Fixed #3566 - malformed CURVE message can cause memory leak

* Fixed #3567 - missing ZeroMQ_INCLUDE_DIR in ZeroMQConfig.cmake when only
                static lib is built

* Fixed #3576 - CURVE plaintext secrets now stored in libsodium's secure memory

* Fixed #3588 - install debug libraries for debug msvc builds with CMake

* Fixed #3591 - incorrect ZMQ_MAX_SOCKETS default value in doc

* Fixed #3594 - fixed stream_engine use after free due to concurrent heartbeats

* Fixed #3586 - error when compiling with MinGW due to usage of MS-specific
                __except keyword

* Fixed #3603 - fixed CMake build on SL6.9

* Fixed #3607 - added scripts to ease performance graph generation

* Fixed #3608 - fix for IPv4 mapping not supported in DragonFlyBSD

* Fixed #3636 - added ENABLE_PRECOMPILED CMake option to fix build with Ninja

* Fixed #2862 - UDP engine aborts on networking-related errors from socket
                syscalls

* Fixed #3656 - segfault on sending data from XSUB to XPUB

* Fixed #3646 - static-only test run fails

* Fixed #3668 - fixed CMAKE_CXX_FLAGS_* regexes on MSVC

* Fixed #110  - do not include winsock2.h in public zmq.h header

* Fixed #3683 - allow "configure --disable-maintainer-mode"

* Fixed #3686 - fix documentation about sockets blocking on send operations

* Fixed #3323 - fix behavior of ZMQ_CONFLATE on PUB sockets

* Fixed #3698 - fix build on IBM i/PASE/os400

* Fixed #3705 - zero-sized messages cause assertion when glibc assertion are on

* Fixed #3713 - remove dependency on math library by avoiding std::ceil

* Fixed #3694 - build targeting Windows XP is broken

* Fixed #3691 - added support for IPC on Windows 10 via AF_UNIX

* Fixed #3725 - disable by default test that requires sudo on CMake

* Fixed #3727 - fix zmq_poller documentation example

* Fixed #3729 - do not check for FD_OOB when using WSAEventSelect on Windows

* Fixed #3738 - allow renaming the library in CMake

* Fixed #1808 - use AF_UNIX instead of TCP for the internal socket on Windows 10

* Fixed #3758 - fix pthread_set_affinity detection in CMake

* Fixed #3769 - fix undefined behaviour in array.hpp

* Fixed #3772 - fix compiling under msys2-mingw

* Fixed #3775 - add -latomic to the private libs flag in pkg-config if needed

* Fixed #3778 - fix documentation of zmq_poller's thread safety

* Fixed #3792 - do not allow creation of new sockets after zmq_ctx_shutdown

* Fixed #3805 - improve performance of CURVE by reducing copies

* Fixed #3814 - send subscribe/cancel as commands to ZMTP 3.1 peers

* Fixed #3847 - fix building without PGM and NORM

* Fixed #3849 - install .cmake file in arch-dependent subdirectory

* Fixed #4005 - allow building on Windows ARM/ARM64

0MQ version 4.3.2 stable, released on 2019/07/08
================================================

* CVE-2019-13132: a remote, unauthenticated client connecting to a
  libzmq application, running with a socket listening with CURVE
  encryption/authentication enabled, may cause a stack overflow and
  overwrite the stack with arbitrary data, due to a buffer overflow in
  the library. Users running public servers with the above configuration
  are highly encouraged to upgrade as soon as possible, as there are no
  known mitigations. All versions from 4.0.0 and upwards are affected.
  Thank you Fang-Pen Lin for finding the issue and reporting it!

* New DRAFT (see NEWS for 4.2.0) zmq_socket_monitor_versioned API that supports
  a versioned monitoring events protocol as a parameter. Passing 1 results in
  the same behaviour as zmq_socket_monitor.
  Version 2 of the events protocol allows new events, new metadata, different
  socket types for the monitors and more. It is described in details in
  doc/zmq_socket_monitor_versioned.txt

* New DRAFT (see NEWS for 4.2.0) zmq_socket_monitor_pipes_stats that triggers
  a new ZMQ_EVENT_PIPES_STATS to be delivered via zmq_socket_monitor_versioned
  v2 API, which contains the current status of all the queues owned by the
  monitored socket. See doc/zmq_socket_monitor_versioned.txt for details.

* New DRAFT (see NEWS for 4.2.0) zmq_poller_fd that returns the FD of a thread
  safe socket. See doc/zmq_poller.txt for details.

* New DRAFT (see NEWS for 4.2.0) socket options:
  - ZMQ_XPUB_MANUAL_LAST_VALUE is similar to ZMQ_XPUB_MANUAL but allows to avoid
    duplicates when using last value caching.
  - ZMQ_SOCKS_USERNAME and ZMQ_SOCKS_PASSWORD that implement SOCKS5 proxy
    authentication.
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* Implemented background thread names for Windows, when the Visual Studio
  debugger is being used.

* Fixed #3358 - test_security_zap failing due to SIGBUS on SPARC64, hard-coded
                IPC socket binds in tests cause race conditions

* Fixed #3361 - enabling GSSAPI support (when using autools) does not work due
                to regression introduced in 4.2.3

* Fixed #3362 - remove documentation for ZMQ_THREAD_PRIORITY context option
                getter, it's not implemented

* Fixed #3363 - tests fail to build due to stricter compiler printf validation
                in new versions of GCC

* Fixed #3367 - try to infer cacheline size at build time, first with
                getconf LEVEL1_DCACHE_LINESIZE, and then by reading
                /sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size
                (autoconf only), and only then falling back to the previous
                default of 64 bytes. Avoids false sharing on POWER and s390x.
                Import ax_func_posix_memalign.m4 as a more reliable check for
                posix_memalign presence on some unix platforms.
                Prefer c++11 atomic primitives to compiler intrinsics, when
                both are available, as the former is more reliable.
                Set test_pair_ipc and test_rebind_ipc to XFAIL on GNU/Hurd due
                to non-functioning getsockname on AF_UNIX.

* Fixed #3370 - Make queue length and HWM state observable

* Fixed #3373 - performance regression in zmq_poll on CentOS 6/7

* Fixed #3375 - assign names to all pthreads created by the library to ease
                debugging

* Fixed #3376 - assigned random TIPC port is not returned by ZMQ_LAST_ENDPOINT

* Fixed #3385 - TCP port in ZMQ_LAST_ENDPOINT depends on global locale

* Fixed #3404 - use std::condition_variable_any when possible

* Fixed #3436 - reconnect interval exponential backoff and may lead to integer
                overflows

* Fixed #3440 - improve zmq_proxy performance by batching of up to 1000
                consecutive messages (if any) and add perf/proxy_thr tool

* Fixed #3451 - fix support of /dev/poll on Solaris

* Fixed #3452 - strnlen may not be available

* Fixed #1462 - test failure in test_filter_ipc due to invalid system groups

* Fixed #3269 - Boost.ASIO integration stopped working with v4.3.0

* Fixed #3479 - ZeroMQ does not build for QNX 6.6 with CMake

* Fixed #3481 - add <ios> include to fix uClibc++ compilation

* Fixed #3491 - build broken on Fedora 30

* Fixed #3494 - ZeroMQConfig.cmake fails if shared libraries are not built

* Fixed #3498 - syntax error on Windows related to socket descriptor type

* Fixed #3500 - PLAIN HELLO message incorrectly uses WELCOME literal, regression
                introduced in 4.3.0

* Fixed #3517 - configure errors because of syntax errors in the use of test
                shell command

* Fixed #3521 - document how to achieve high performance with the PGM transport

* Fixed #3526 - failure case behavior unclear in zmq_msg_send documentation

* Fixed #3537 - fix build on z/OS by using pthread_equal instead of comparing
                variables directly

* Fixed #3546 - CMake links with librt on MinGW which is not available

* Many coding style, duplication, testing and static analysis improvements.


0MQ version 4.3.1 stable, released on 2019/01/12
================================================

* CVE-2019-6250: A vulnerability has been found that would allow attackers to
  direct a peer to jump to and execute from an address indicated by the
  attacker.
  This issue has been present since v4.2.0. Older releases are not affected.
  NOTE: The attacker needs to know in advance valid addresses in the peer's
  memory to jump to, so measures like ASLR are effective mitigations.
  NOTE: this attack can only take place after authentication, so peers behind
  CURVE/GSSAPI are not vulnerable to unauthenticated attackers.
  See https://github.com/zeromq/libzmq/issues/3351 for more details.
  Thanks to Guido Vranken for uncovering the issue and providing the fix!

* Note for packagers: as pkg-config's Requires.private is now used to properly
  propagate dependencies for static builds, the libzmq*-dev or zeromq-devel or
  equivalent package should now depend on the libfoo-dev or foo-devel packages
  of all the libraries that zmq is linked against, or pkg-config --libs libzmq
  will fail due to missing dependencies on end users machines.

* Fixed #3351 - remote code execution vulnerability.

* Fixed #3343 - race condition in ZMQ_PUSH when quickly disconnecting and
                reconnecting causes last part of multi-part message to get
                "stuck" and resent by mistake to the new socket.

* Fixed #3336 - set Requires.private in generate pkg-config file.

* Fixed #3334 - set TCP_NODELAY after connect() on Windows for the I/O socket.

* Fixed #3326 - assert on Android when opening a socket and disabling WiFi.

* Fixed #3320 - build failure on OpenBSD with GCC.

0MQ version 4.3.0 stable, released on 2018/11/28
================================================

* The following DRAFT APIs have been marked as STABLE and will not change
  anymore:
  - ZMQ_MSG_T_SIZE context option (see doc/zmq_ctx_get.txt)
  - ZMQ_THREAD_AFFINITY_CPU_ADD and ZMQ_THREAD_AFFINITY_CPU_REMOVE (Posix only)
    context options, to add/remove CPUs to the affinity set of the I/O threads.
    See doc/zmq_ctx_set.txt and doc/zmq_ctx_get.txt for details.
  - ZMQ_THREAD_NAME_PREFIX (Posix only) context option, to add a specific
    integer prefix to the background threads names, to easily identify them.
    See doc/zmq_ctx_set.txt and doc/zmq_ctx_get.txt for details.
  - ZMQ_GSSAPI_PRINCIPAL_NAMETYPE and ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE
    socket options, for the corresponding GSSAPI features. Additional
    definitions for principal name types:
    - ZMQ_GSSAPI_NT_HOSTBASED
    - ZMQ_GSSAPI_NT_USER_NAME
    - ZMQ_GSSAPI_NT_KRB5_PRINCIPAL
    See doc/zmq_gssapi.txt for details.
  - ZMQ_BINDTODEVICE socket option (Linux only), which will bind the
    socket(s) to the specified interface. Allows to use Linux VRF, see:
    https://www.kernel.org/doc/Documentation/networking/vrf.txt
    NOTE: requires the program to be ran as root OR with CAP_NET_RAW
  - zmq_timers_* APIs. These functions can be used for cross-platforms timed
    callbacks. See doc/zmq_timers.txt for details.
  - The following socket monitor events:
    - ZMQ_EVENT_HANDSHAKE_FAILED_NO_DETAIL: unknown errors during handshake.
    - ZMQ_EVENT_HANDSHAKE_SUCCEEDED: Handshake completed with authentication.
    - ZMQ_EVENT_HANDSHAKE_FAILED_PROTOCOL: Protocol errors with peers or ZAP.
    - ZMQ_EVENT_HANDSHAKE_FAILED_AUTH: Failed authentication requests.
    See doc/zmq_socket_monitor.txt for more details and error codes.
  - zmq_stopwatch_intermediate which returns the time elapsed without stopping
    the stopwatch.
  - zmq_proxy_steerable command 'STATISTICS' to retrieve stats about the amount
    of messages and bytes sent and received by the proxy.
    See doc/zmq_proxy_steerable.txt for more information.

* The build-time configuration option to select the poller has been split, and
  new API_POLLER (CMake) and --with-api-poller (autoconf) options will now
  determine what system call is used to implement the zmq_poll/zmq_poller APIs.
  The previous POLLER and --with-poller options now only affects the
  internal I/O thread. In case API_POLLER is not specified, the behaviour keeps
  backward compatibility intact and will be the same as with previous releases.

* The non-default "poll" poller for the internal I/O thread (note: NOT for the
  zmq_poll/zmq_poller user APIs!) has been disabled on Windows as WSAPoll does
  not report connection failures. For more information see:
  - https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/
  - https://curl.haxx.se/mail/lib-2012-10/0038.html
  - https://bugs.python.org/issue16507

* New epoll implementation for Windows, using the following implementation:
  https://github.com/piscisaureus/wepoll/tree/v1.5.4
  To use this, select "epoll" as the poller option in the build system.
  Note for distributors: the wepoll source code is embedded and distributed.
  It is licensed under the BSD-2-Clause and thus it is compatible with LGPL-3.0.
  Note that, if selected at build time, the license text must be distributed
  with the binary in accordance to the license terms. A copy can be found at:
  external/wepoll/license.txt

* The pre-made Visual Studio solutions file are deprecated, and users are
  encouraged to use the CMake solution generation feature instead.

* New DRAFT (see NEWS for 4.2.0) socket options:
  - ZMQ_ROUTER_NOTIFY to deliver a notification when a peer connects and/or
    disconnects in the form of a routing id plus a zero-length frame.
  - ZMQ_MULTICAST_LOOP to control whether the data sent should be looped back
    on local listening sockets for UDP multicast sockets (ZMQ_RADIO).
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* New perf tool, perf/benchmark_radix_tree, to measure the performance of the
  different internal implementations of the trie algorithm used to track
  subscriptions. Requires a compiler that supports C++11.

* New autoconf flag "--enable-force-CXX98-compat" which will force -std=gnu++98
  and, if the compiler supports them (clang++ at the moment), it will also add
  -Wc++98-compat -Wc++98-compat-pedantic so that compatibility with C++98 can
  be tested.

* Many, many coding style, duplication and static analysis improvements.

* Many, many improvements to the CMake build system, especially on Windows.

* Many, many improvements to unit tests.

* Fixed #3036 - Compilation error when -pedantic is used.

* Fixed #3028 - Failure when zmq_poller_destroy is called after zmq_ctx_term.

* Fixed #2989 - CMake: Linker PDB install rule does not work when Visual Studio
                generators are used.

* Fixed #3045 - configure.ac: search for dladdr only when using libunwind.

* Fixed #3060 - REQ sockets terminate TCP connection after first heartbeat if
                ZMQ_HEARTBEAT_IVL is set.

* Fixed #2212 - UDP: need ability to specify bind address separately from
                multicast address for multi-homed hosts.

* Fixed #2891 - UDP: address name resolution is limited to dotted IPv4 rather
                than being capable of IPv4, IPv6, and hostname lookup.

* Fixed #3085 - autoconf/CMake getrandom test does not check if it's working but
                only for its presence.

* Fixed #3090 - compilation broken with Solaris Studio.

* Fixed #3094 - UDP: pass interface via IP[V6]_MULTICAST_IF if provided.

* Fixed #3061 - implement ZMTP 3.1 ping/pong context sending/receiving.

* Fixed #2188 - Added documentation for new zmq_poller API.

* Fixed #3088 - zmq_poller_add/zmq_poller_modify should reject invalid events
                arguments.

* Fixed #3042 - Fixed compilation on ARM with ZMQ_ATOMIC_PTR_MUTEX.

* Fixed #3107 - test_immediate_3/test_reconnect_inproc do not terminate with
                POLL as the I/O thread poller under Windows.

* Fixed #3046 - Aborts when iOS abuses EBADF to report a socket has been
                reclaimed.

* Fixed #3136 - Cannot set ZMQ_HEARTBEAT_TTL to more than 655.3 seconds.

* Fixed #3083 - link with -latomic when needed.

* Fixed #3162 - build failure with MUSL libc.

* Fixed #3158 - -1 value of ZMQ_RECONNECT_IVL was not correctly handled on some
                platforms.

* Fixed #3170 - improved documentation for ZMQ_PAIR.

* Fixed #3168 - correctly use symbols map on Debian/kFreeBSD and Debian/HURD
                to avoid exporting standard library symbols.

* Fixed #3168 - correctly process ZMTP 3.1 cancel/subscribe commands.

* Fixed #3171 - improve documentation for ZMQ_CONFLATE.

* Fixed #2876 - stack overflow on Windows 64.

* Fixed #3191 - race condition with received message causes
                ZMQ_CONNECT_ROUTING_ID to be assigned to wrong socket.

* Fixed #3005 - added documentation for new zmq_timers_* API.

* Fixed #3222 - use /Z7 debug on Release builds too on Windows (CMake).

* Fixed #3226 - possible PGM receiver crash.

* Fixed #3236 - UDP dish socket can't bind to a multicast port already in use.

* Fixed #3242 - improve HWM documentation.

* Fixed #2488 - improve zmq_msg_send doc return value documentation.

* Fixed #3268 - HWM in ZMQ_DGRAM socket does not respect multipart message.

* Fixed #3284 - added support for ZMQ_MULTICAST_HOPS with UDP sockets.

* Fixed #3245 - use-after-free reported in zmq::pipe_t::terminate.

* Fixed #1400 - use patricia trie for subscription to improve performances and
                memory usage. Note: only active in DRAFT builds for now.

* Fixed #3263 - fix abort on Windows when a large TCP read is requested and
                fails.

* Fixed #3312 - fix build on Android Things 1.06 with Termux.


0MQ version 4.2.5 stable, released on 2018/03/23
================================================

* Fixed #3018 - fix backward-incompatible change in the NULL auth
                mechanism that slipped in 4.2.3 and made connections
                with a ZAP domain set on a socket but without a working
                ZAP handler fail. See ZMQ_ZAP_ENFORCE_DOMAIN and RFC27.

* Fixed #3016 - clarify in zmq_close manpage that the operation will
                complete asynchronously.

* Fixed #3012 - fix CMake build problem when using LIBZMQ_WERROR and a
                compiler other than GCC.


0MQ version 4.2.4 stable, released on 2018/03/21
================================================

* New DRAFT (see NEWS for 4.2.0) socket options:
  - ZMQ_LOOPBACK_FASTPATH to enable faster TCP loopback on Windows
  - ZMQ_METADATA to set application-specific metadata on a socket
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* New DRAFT (see NEWS for 4.2.0) context options:
  - ZMQ_ZERO_COPY_RECV to disable zero-copy receive to save memory
    at the expense of slower performance
  See doc/zmq_ctx_set.txt and doc/zmq_ctx_get.txt for details.

* New DRAFT API zmq_stopwatch_intermediate which returns the time
  elapsed without stopping the stopwatch.

* TIPC: support addressing TIPC Port Identity addresses.

* Added CMake option to disable tests: BUILD_TESTS

* Added CMake and autotools make targets to support clang-formatter:
  make clang-format, clang-format-check and clang-format-diff to
  help developers make sure their code conforms to the style guidelines

* For distributors: a new test framework has been added, which
  includes a copy of the Unity source code. This source code library is
  distributed under the MIT license and thus is compatible with
  libzmq's LGPL3.

* Fixed #2867 - add ZeroMQConfig.cmake.in to distributable tarball

* Fixed #2868 - fix OpenBSD build

* Fixed #2870 - fix VC++ 11.0 (VS2012) build

* Fixed #2879 - prevent duplicate connections on PUB sockets

* Fixed #2872 - fix CMake tests on Windows

* Fixed #2895 - fix assert on Windows with POLL

* Fixed #2920 - fix Windows build with Intel compiler

* Fixed #2930 - use std::atomic when available with VC++ and VS2015

* Fixed #2910 - fix race condition with ZMQ_LINGER socket option

* Fixed #2927 - add support for ZMQ_XPUB_NODROP on ZMQ_RADIO

* Fixed #2820 - further clarify ZMQ_XPUB_VERBOSE(R) documentation.

* Fixed #2911 - ZMQ_DISH over UDP triggers errno_assert() after hitting
                watermark

* Fixed #2942 - ZMQ_PUB crash when due to high volume of subscribe and
                unsubscribe messages, an unmatched unsubscribe message is
                received in certain conditions

* Fixed #2946 - fix Windows CMake build when BUILD_SHARED is off

* Fixed #2960 - fix build with GCC 8

* Fixed #2967 - fix race condition on thread safe sockets due to pthread
                condvar timeouts on OSX

* Fixed #2977 - fix TIPC build-time availability check to be more relaxed

* Fixed #2966 - add support for WindRiver VxWorks 6.x

* Fixed #2963 - fix some PVS Studio static analysis warnings

* Fixed #2983 - fix MinGW cross-compilation

* Fixed #2991 - fix mutex assert at shutdown when the zmq context is part
                of a class declared as a global static


0MQ version 4.2.3 stable, released on 2017/12/13
================================================

* API change: previously ZMQ_POLLOUT on a ZMQ_ROUTER socket returned always
  true due to how the type works. When ZMQ_ROUTER_MANDATORY is set, sending
  fails when the peer is not available, but ZMQ_POLLOUT always returns true
  anyway, which does not make sense. Now when ZMQ_ROUTER_MANDATORY is set,
  ZMQ_POLLOUT on a ZMQ_ROUTER will return true only if at least one peer is
  available.
  Given ZMQ_POLLOUT with ZMQ_ROUTER was not usable at all previously, we do
  not consider this a breakage warranting a major or minor version increase.

* ZMQ_IDENTITY has been renamed to ZMQ_ROUTING_ID and ZMQ_CONNECT_RID has been
  renamed to ZMQ_CONNTECT_ROUTING_ID to disambiguate. ZMQ_IDENTITY and
  ZMQ_CONNECT_RID are still available to keep backward compatibility, and will
  be removed in a future release after further advance notice.

* DRAFT API change: zmq_poller_wait, zmq_poller_wait_all and zmq_poller_poll
  have been changed to be inline with other existing APIs that have a timeout
  to return EAGAIN instead of ETIMEDOUT as the errno value.
  See #2713 for details.

* Existing non-DRAFT socket types ZMQ_REP/REQ, ZMQ_ROUTER/DEALER and
  ZMQPUB/SUB, that were previously declared deprecated, have been reinstated
  as stable and supported. See #2699 for details.

* Tweetnacl: add support for, and use preferably if available, getrandom() as
  a simpler and less error-prone alternative to /dev/urandom on OSes where it
  is available (eg: Linux 3.18 with glibc 2.25).

* Curve: all remaining traces of debug output to console are now removed, and
  new DRAFT events are available to properly debug CURVE, PLAIN, GSSAPI and
  ZAP events and failures. See below for details on the new events.

* New DRAFT (see NEWS for 4.2.0) socket options:
  - ZMQ_GSSAPI_PRINCIPAL_NAMETYPE and ZMQ_GSSAPI_SERVICE_PRINCIPAL_NAMETYPE, for
    the corresponding GSSAPI features. Additional definitions for principal
    name types:
    - ZMQ_GSSAPI_NT_HOSTBASED
    - ZMQ_GSSAPI_NT_USER_NAME
    - ZMQ_GSSAPI_NT_KRB5_PRINCIPAL
    See doc/zmq_gssapi.txt for details.
  - ZMQ_BINDTODEVICE (Linux only), which will bind the socket(s) to the
    specified interface. Allows to use Linux VRF, see:
    https://www.kernel.org/doc/Documentation/networking/vrf.txt
    NOTE: requires the program to be ran as root OR with CAP_NET_RAW
  - ZMQ_ZAP_ENFORCE_DOMAIN, enables strict RFC 27 compatibility mode and makes
    the ZAP Domain mandatory when using security. See:
    https://rfc.zeromq.org/spec:27/ZAP
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* New DRAFT (see NEWS for 4.2.0) context options:
  - ZMQ_THREAD_AFFINITY_CPU_ADD and ZMQ_THREAD_AFFINITY_CPU_REMOVE (Posix only),
    to add and remove CPUs to the affinity set of the I/O threads. Useful to pin
    the background threads to specific CPUs.
  - ZMQ_THREAD_NAME_PREFIX (Posix only), to add a specific integer prefix to the
    background threads names, to easily identify them for debugging purposes.
  See doc/zmq_ctx_set.txt and doc/zmq_ctx_get.txt for details.

* New DRAFT (see NEWS for 4.2.0) message property name definitions to facilitate
  the use of zmq_msg_gets:
  - ZMQ_MSG_PROPERTY_ROUTING_ID
  - ZMQ_MSG_PROPERTY_SOCKET_TYPE
  - ZMQ_MSG_PROPERTY_USER_ID
  - ZMQ_MSG_PROPERTY_PEER_ADDRESS
  See doc/zmq_msg_gets.txt for details.

* New DRAFT (see NEWS for 4.2.0) API zmq_socket_get_peer_state, to be used to
  query the state of a specific peer (via routing-id) of a ZMQ_ROUTER socket.

* New DRAFT (see NEWS for 4.2.0) Socket Monitor events:
  - ZMQ_EVENT_HANDSHAKE_FAILED_NO_DETAIL, unknown system error and returns errno
  - ZMQ_EVENT_HANDSHAKE_SUCCEEDED, handshake was successful
  - ZMQ_EVENT_HANDSHAKE_FAILED_PROTOCOL, protocol errors between peers or server
    and ZAP handler. Returns one of ZMQ_PROTOCOL_ERROR_* - see manpage for list
  - ZMQ_EVENT_HANDSHAKE_FAILED_AUTH, failed authentication, returns ZAP status
  These events trigger when the ZMTP security mechanism handshake is
  completed or failed. See doc/zmq_socket_monitor.txt for more information.

* New DRAFT (see NEWS for 4.2.0) zmq_proxy_steerable command 'STATISTICS' to
  retrieve stats about the amount of messages and bytes sent and received by
  the proxy. See doc/zmq_proxy_steerable.txt for more information.

* Add new autoconf --disable-libunwind option to stop building with libunwind
  even if it is available.

* Add new autoconf --disable-Werror option to avoid building with the Werror
  flag.

* Use pkg-config as the first method for finding and building with external
  optional dependencies such as libnorm, libpgm and gssapi.

* On Posix platform where the feature is available, name the ZMQ background
  threads to simplify debugging: "ZMQbg/<num_thread>"

* Improve performance of zmq_poller_* (and zmq_poll and zmq_proxy when building
  with DRAFT APIs enabled).

* The TCP unit tests have been refactored to bind and connect to random ports
  rather than hard-coded ones, to allow running tests in parallel.
  There are 6 exceptions where it is necessary to use an hard-coded port to
  test specific code paths that would not be exercised when binding to a
  wildcard port. These are listed in tests/testutil.hpp so that distributions
  can easily patch them if they wish to and so that they can be unique across
  all the tests, allowing parallel runs.
  The IPC unit tests have been changed as well to use unique socket file names
  per test, where before there were some clashes.

* Fixed #2349 - fix building with libsodium when using CMake

* Fixed #2334 - do not assert when tuning socket options fails due to network
  errors, but simply retry again when connecting or send a socket monitor
  ZMQ_EVENT_ACCEPT_FAILED event when binding

* Fixed #2341 - fix source files path in VS2015 solution

* Fixed #2344 - Note that on Windows with VS2012 it is mandatory to increase
  the default stack size to at least 2MB

* Fixed #2348 - ZMQ_ROUTER send with ZMQ_ROUTER_MANDATORY can be stuck in case of
  network problem

* Fixed #2358 - occasional abort on zmq_connect on Windows

* Fixed #2370 - zmq_curve_keypair should return an error on failure rather
  than ignoring them and always returning 0

* Fixed #2452 - __STDC_LIMIT_MACROS before precompiled headers causes VC++
  warning

* Fixed #2457 - fix building with libsodium in Visual Studio solutions

* Fixed #2466 - add const qualifier to internal and public API that does not
  modify parameters

* Fixed #2471 - do more checks for OOM conditions when dynamic allocations is
  used

* Fixed #2476 - assertion causes abort after ZAP stop at shutdown

* Fixed #2479 - improve zmq_poller performance on Windows

* Fixed #2481 - potential memory leaks due to ZMTP handshake failures

* Fixed #2531 - ZMQ_GSSAPI_PRINCIPAL sockopt has no effect on client side

* Fixed #2535 - add BUILD_SHARED and BUILD_STATIC options to CMake, both on by
  default, to toggle shared and static library builds

* Fixed #2537 - use SYSTEM_CLOCK on OSX and CLOCK_MONOTONIC elsewhere for
  internal timers to avoid races

* Fixed #2540 - new zmq_poller used by zmq_poll without DRAFTs

* Fixed #2552 - Fix WITH_DOC CMake build to avoid checking for asciidoc if the
  option is disabled

* Fixed #2567 - Memory leak in REP socket handling

* Fixed #2579 - Compilation issue on Windows with CMake + ninja

* Fixed #2588 - SIGBUS under 64-bit SunOS Sparc

* Fixed #2590 - crash when using ZMQ_IMMEDIATE and ZMQ_LINGER to non-zero

* Fixed #2601 - XPUB_MANUAL subscriptions not removed on peer term

* Fixed #2602 - intermittent memory leak for ZMQ_REQ/REP send/recv

* Fixed #2608 - CURVE server (connect) fails when client rebinds

* Fixed #2610 - print backtraces in mutual exclusion to avoid mixing
  different traces

* Fixed #2621 - add missing CMake files to distributable tarball

* Fixed #2630 - improve compatibility with OpenBSD w.r.t. IPV6_V6ONLY

* Fixed #2638 - note in INSTALL that when using Windows builds on Linux with
  Wine it is necessary to increase the minimum TCP buffers

* Fixed #2632 - Fix file descriptor leak when using Tweetnacl (internal NACL
  implementation) instead of Libsodium, and fix race condition when using
  multiple ZMQ contexts with Tweetnacl

* Fixed #2681 - Possible buffer overflow in CURVE mechanism handshake.
  NOTE: this was protected by an assert previously, so there is no security
  risk.

* Fixed #2704 - test_sockopt_hwm fails occasionally on Windows

* Fixed #2701 - pgm build via cmake doesn't link libzmq with libpgm

* Fixed #2711 - ZAP handler communication errors should be handled consistently

* Fixed #2723 - assertion in src\select.cpp:111 or hang on zmq_ctx_destroy on
  Windows

* Fixed #2728 - fix support O_CLOEXEC when building with CMake

* Fixed #2761 - improve compatibility with TrueOS (FreeBSD 12)

* Fixed #2764 - do not unlink IPC socket files when closing a socket to avoid
  race conditions

* Fixed #2770 - support lcov 1.13 and newer

* Fixed #2787 - add libiphlpapi to PKGCFG_LIBS_PRIVATE for static mingw builds

* Fixed #2788 - document that adding -DZMQ_STATIC is required for Windows
  static builds with Mingw

* Fixed #2789 - description of zmq_atomic_counter_value return value is cloned
  from zmq_atomic_counter_new

* Fixed #2791 - fix building with DRAFT APIs on CentOS 6

* Fixed #2794 - router_t methods should not allocate memory for lookup in
  outpipes

* Fixed #2809 - optimize select() usage on Windows

* Fixed #2816 - add CMake and autoconf check for accept4, as it is not
  available on old Linux releases, and fallback to accept + FD_CLOEXEC

* Fixed #2824 - ZMQ_REQ socket does not report ZMQ_POLLOUT when ZMQ_REQ_RELAXED
  is set

* Fixed #2827 - add support for Haiku

* Fixed #2840 - fix building with VS2008

* Fixed #2845 - correct the ZMQ_LINGER documentation to accurately reflect that
  the default value is -1 (infinite). It never was 30 second in any released
  version, it was only changed briefly and then changed back, but the manpage
  was not reverted.

* Fixed #2861 - CMake/MSVC: export ZMQ_STATIC when needed.

0MQ version 4.2.2 stable, released on 2017/02/18
=============================================

* Improve compatibility with GNU Hurd

* Fixed #2286 - improve CMake on Windows documentation

* Fixed #1235 - improved compatibility with mingw64

* Improve zmq_proxy documentation to state it can return ETERM as well

* Fixed #1442 - SO_NOSIGPIPE and connection closing by peer race condition

* Improve CMake functionality on Windows: ZeroMQConfig.cmake generation CPack
  option, correct static library filename, ship FindSodium.cmake in tarball

* Fixed #2228 - setting HWM after connect on inproc transport leads to infinite
  HWM

* Add support for Visual Studio 2017

* New DRAFT (see NEWS for 4.2.0) zmq_has option "draft" option that returns
  true if the library was built with DRAFT enabled. Useful for FFI bindings.
  See doc/zmq_has.txt for more information

* Fixed #2321 - zmq_z85_decode does not validate its input. The function has
  been fixed to correctly follow RFC32 and return NULL if the input is invalid

* Fixed #2323 - clock_t related crash on Apple iOS 9.3.2 and 9.3.5

* Fixed #1801 - OSX: Cmake installs libzmq in a weird PATH

* Fixed potential divide by zero in zmq::lb_t::sendpipe

* Improve compatibility with OpenIndiana by skipping epoll and using poll/select

* Fix IPv4-in-IPv6 mapped addresses parsing error


0MQ version 4.2.1 stable, released on 2016/12/31
=============================================

* New DRAFT (see NEWS for 4.2.0) Socket Monitor events:
  - ZMQ_EVENT_HANDSHAKE_SUCCEED
  - ZMQ_EVENT_HANDSHAKE_FAILED
  These events trigger when the ZMTP security mechanism handshake is
  completed. See doc/zmq_socket_monitor.txt for more information.

* New DRAFT (see NEWS for 4.2.0) Context options:
  - ZMQ_MSG_T_SIZE
  See doc/zmq_ctx_get.txt for more information.

* Fixed #2268 - improved compatibility with mingw32

* Fixed #2254 - ZMQ_PUB compatibility with libzmq 2.x broken

* Fixed #2245 - added support for VS2017, Windows SDK 10.0.14393.0, toolset v141

* Fixed #2242 - file descriptors leaks on fork+exec

* Fixed #2239 - retired poller item crash from reaper thread

* Fixed #2234 - improved compatibility with AIX 7.1

* Fixed #2225 - cannot pick select for poller

* Fixed #2217 - CMake build uses library version as the ABI version

* Fixed #2208 - added support for ZMQ_TOS on IPv6

* Fixed #2200 - no documentation for ZMQ_SOCKS_PROXY

* Fixed #2199 - no documentation for zmq_curve_public

* Fixed #2196 - fixed build and runtime errors on kFreeBSD


0MQ version 4.2.0 stable, released on 2016/11/04
=============================================

* For Pieter. Thanks for making all of this possible.

  "Tell them I was a writer.
   A maker of software.
   A humanist. A father.
   And many things.
   But above all, a writer.
   Thank You. :)"
   - Pieter Hintjens

* This release introduces new APIs, but it is ABI compatible with
  libzmq 4.1.2 and up.

* Note for ARM and SPARC users: an alignment problem in zmq_msg_t that could in
  some cases and on some CPUs cause a SIGBUS error was solved, but it requires
  a rebuild of your application against the 4.2.0 version of include/zmq.h.
  To clarify, this change does not affect the internals of the library but only
  the public definition of zmq_msg_t, so there is no ABI incompatibility.

* Security with Curve is now available by default thanks to Tweetnacl sources:
  https://tweetnacl.cr.yp.to/index.html
  Libsodium is still fully supported but has to be enabled with the build flag
  --with-libsodium. Distribution and package maintainers are encouraged to use
  libsodium so that the security implementation can be audited and maintained
  separately.

* New Context options:
  - ZMQ_MAX_MSGSZ
  - ZMQ_BLOCKY
  See doc/zmq_ctx_set.txt and doc/zmq_ctx_get.txt for details.

* New Socket options:
  - ZMQ_HANDSHAKE_IVL
  - ZMQ_SOCKS_PROXY
  - ZMQ_XPUB_NODROP
  - ZMQ_XPUB_MANUAL
  - ZMQ_XPUB_WELCOME_MSG
  - ZMQ_STREAM_NOTIFY
  - ZMQ_INVERT_MATCHING
  - ZMQ_HEARTBEAT_IVL
  - ZMQ_HEARTBEAT_TTL
  - ZMQ_HEARTBEAT_TIMEOUT
  - ZMQ_XPUB_VERBOSER
  - ZMQ_CONNECT_TIMEOUT
  - ZMQ_TCP_MAXRT
  - ZMQ_THREAD_SAFE
  - ZMQ_MULTICAST_MAXTPDU
  - ZMQ_VMCI_BUFFER_SIZE
  - ZMQ_VMCI_BUFFER_MIN_SIZE
  - ZMQ_VMCI_BUFFER_MAX_SIZE
  - ZMQ_VMCI_CONNECT_TIMEOUT
  - ZMQ_USE_FD
  See doc/zmq_setsockopt.txt and doc/zmq_getsockopt.txt for details.

* New CURVE helper function to derive z85 public key from secret key:
