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   </header>
   <p>This document describes the changes made to the ERTS application.</p>
 
+<section><title>Erts 10.4</title>
+
+    <section><title>Fixed Bugs and Malfunctions</title>
+      <list>
+        <item>
+          <p>
+	    Do not allocate new bitstring/binary when an empty binary
+	    is appended.</p>
+          <p>
+	    Own Id: OTP-15535 Aux Id: PR-2055 </p>
+        </item>
+        <item>
+          <p>
+	    Document that <c>process_info(_, current_function)</c>
+	    can return <c>{current_function, undefined}</c> in case
+	    of execution of native code.</p>
+          <p>
+	    Own Id: OTP-15543 Aux Id: PR-2089 </p>
+        </item>
+        <item>
+          <p>
+	    Fixed bug in <c>ets:select</c>, <c>ets:match</c> and
+	    friends which could cause the table to remain fixated (as
+	    if <c>ets:safe_fixtable</c> had been called) after the
+	    call returned. This could happen for <c>protected</c>
+	    tables if another concurrent running process transfered
+	    table ownership to the process during its
+	    ets:select/match call. Ownership can be transfered using
+	    either <c>ets:give_away</c> or the <c>heir</c> table
+	    option.</p>
+          <p>
+	    Own Id: OTP-15672</p>
+        </item>
+        <item>
+	    <p>Fixed a Windows-specific bug in <c>file:list_dir/1</c>
+	    that caused it to misbehave on network shares.</p>
+          <p>
+	    Own Id: OTP-15693</p>
+        </item>
+        <item>
+          <p>
+	    Fixed bug when calling <c>enif_whereis_*</c> from NIF
+	    resource destructor. Symtoms could be emulator crash or
+	    hanging scheduler threads.</p>
+          <p>
+	    Own Id: OTP-15694 Aux Id: ERL-863 </p>
+        </item>
+        <item>
+	    <p>Fixed a bug in the error case of <c>apply/3</c>, where
+	    the exception would erroneously have an empty argument
+	    list in some cases.</p>
+          <p>
+	    Own Id: OTP-15698</p>
+        </item>
+      </list>
+    </section>
+
+
+    <section><title>Improvements and New Features</title>
+      <list>
+        <item>
+          <p>
+	    Add support for Erlang Distribution protocol to split the
+	    payload of large signals into several fragments. This
+	    allows other processes to communicate uninterrupted
+	    during the transmission of these signals.</p>
+          <p>
+	    Own Id: OTP-13397</p>
+        </item>
+        <item>
+          <p>
+	    A simple socket API is provided through the socket
+	    module. This is a low level API that does *not* replace
+	    gen_[tcp|udp|sctp]. It is intended to *eventually*
+	    replace the inet driver, but not the high level
+	    gen-modules (gen_tcp, gen_udp and gen_sctp). It also
+	    provides a basic API that facilitates the implementation
+	    of other protocols, than TCP, UDP and SCTP. </p>
+          <p>
+	    Known issues are; No support for the Windows OS
+	    (currently), a small term leakage.</p>
+          <p>
+	    Own Id: OTP-14831</p>
+        </item>
+        <item>
+	    <p>Added NIF functions <seealso
+	    marker="erl_nif#enif_set_pid_undefined"><c>enif_set_pid_undefined</c></seealso>,
+	    <seealso
+	    marker="erl_nif#enif_is_pid_undefined"><c>enif_is_pid_undefined</c></seealso>
+	    and <seealso
+	    marker="erl_nif#enif_compare_pids"><c>enif_compare_pids</c></seealso>.</p>
+          <p>
+	    Own Id: OTP-15011 Aux Id: PR-2147 </p>
+        </item>
+        <item>
+	    <p>Underutilized memory segments (carriers) can now move
+	    between all allocator instances, rather than just between
+	    instances of the same type, which greatly reduces memory
+	    usage in some scenarios. </p>
+          <p>
+	    Own Id: OTP-15063</p>
+        </item>
+        <item>
+	    <p>The emulator will now mark free blocks in pooled
+	    carriers with <c>madvise(2) + MADV_FREE</c> (or similar),
+	    letting the OS reclaim the associated physical memory if
+	    necessary.</p>
+          <p>
+	    Own Id: OTP-15075</p>
+        </item>
+        <item>
+          <p>
+	    New <c>ERL_NIF_SELECT_CANCEL</c> feature added to
+	    <c>enif_select</c> in order to cancel (or "deselect") a
+	    read or write event on a previously selected file
+	    descriptor.</p>
+          <p>
+	    Own Id: OTP-15095</p>
+        </item>
+        <item>
+          <p>
+	    ETS option <c>write_concurrency</c> now also affects and
+	    improves the scalability of <c>ordered_set</c> tables.
+	    The implementation is based on a data structure called
+	    contention adapting search tree, where the lock
+	    granularity adapts to the actual amount of concurrency
+	    exploited by the applications in runtime.</p>
+          <p>
+	    Own Id: OTP-15128</p>
+        </item>
+        <item>
+          <p>
+	    Build configuration of the <c>crypto</c> application has
+	    been moved from the <c>erts</c> application into the
+	    <c>crypto</c> application.</p>
+          <p>
+	    Own Id: OTP-15129</p>
+        </item>
+        <item>
+	    <p>Anonymous functions that don't capture environment are
+	    now created at load-time instead of in run-time.</p>
+          <p>
+	    Own Id: OTP-15195 Aux Id: PR-1812 </p>
+        </item>
+        <item>
+          <p>
+	    Optimize updates of maps with identical keys and values.
+	    E.g. in the example below the original Map will be reused
+	    as the return of the update.</p>
+          <p>
+	    1> Map = #{ a => b }. #{ a => b } 2> Map#{ a := b }.</p>
+          <p>
+	    Own Id: OTP-15211 Aux Id: PR-1889 </p>
+        </item>
+        <item>
+          <p>
+	    Optimize <c>binary:match/2</c> and
+	    <c>binary:matches/2</c> to use memchr internally.</p>
+          <p>
+	    Own Id: OTP-15238 Aux Id: PR-1803 </p>
+        </item>
+        <item>
+          <p>
+	    The runtime system used to terminate when a message
+	    larger than 2 Gb was passed over the distribution. The
+	    send operation will now instead throw a
+	    <c>system_limit</c> exeption.</p>
+          <p>
+	    Own Id: OTP-15261</p>
+        </item>
+        <item>
+          <p>
+	    Change the first module called by erts to be names
+	    erl_init instead of otp_ring0. systools in sasl have been
+	    updated to reflect this change.</p>
+          <p>
+	    Own Id: OTP-15336 Aux Id: PR-1825 </p>
+        </item>
+        <item>
+          <p>
+	    Minor adjustments made to build system for parallel
+	    configure.</p>
+          <p>
+	    Own Id: OTP-15340 Aux Id: OTP-14625 </p>
+        </item>
+        <item>
+          <p>
+	    Two new NIF interface functions <c>enif_select_read</c>
+	    and <c>enif_select_write</c>. They are similar to
+	    existing <c>enif_select</c> but allow a custom event
+	    message as argument.</p>
+          <p>
+	    Own Id: OTP-15349 Aux Id: PR-2084 </p>
+        </item>
+        <item>
+	    <p>The embedded copy of <c>zlib</c> has been updated from
+	    <c>1.2.8</c> to <c>1.2.11</c>.</p>
+	    <p>Note that this copy is only used as a fallback when
+	    the target platform doesn't provide any <c>zlib</c>
+	    development libraries. If your system provides
+	    <c>zlib</c> then it will be used even if it is older than
+	    <c>1.2.11</c>.</p>
+          <p>
+	    Own Id: OTP-15351 Aux Id: ERL-749 </p>
+        </item>
+        <item>
+          <p>
+	    New NIF function <c>enif_make_monitor_term</c>.</p>
+          <p>
+	    Own Id: OTP-15362 Aux Id: PR-2127 </p>
+        </item>
+        <item>
+	    <p>Appending lists (The ++ operator) will now yield
+	    properly on large inputs.</p>
+          <p>
+	    Own Id: OTP-15427</p>
+        </item>
+        <item>
+	    <p>The <c>length/1</c> BIF used to calculate the length
+	    of the list in one go without yielding, even if the list
+	    was very long. In OTP 22, <c>length/1</c> will yield when
+	    called with a long lists.</p>
+          <p>
+	    Own Id: OTP-15439</p>
+        </item>
+        <item>
+          <p>
+	    Processes sending messages are now punished with a
+	    reduction cost based on message size. That is, a process
+	    sending a large message will yield earlier than before.</p>
+          <p>
+	    Own Id: OTP-15513 Aux Id: ERL-773 </p>
+        </item>
+        <item>
+	    <p>The transitory emulator option <c>+ztma true</c>
+	    (introduced in OTP 21.3) has been removed.</p>
+          <p>
+	    Own Id: OTP-15581 Aux Id: OTP-15580 </p>
+        </item>
+        <item>
+	    <p>In OTP 22, HiPE (the native code compiler) is not
+	    fully functional. The reasons for this are:</p>
+	    <p>There are new BEAM instructions for binary matching
+	    that the HiPE native code compiler does not support.</p>
+	    <p>The new optimizations in the Erlang compiler create
+	    new combination of instructions that HiPE currently does
+	    not handle correctly.</p>
+	    <p>If erlc is invoked with the <c>+native</c> option, and
+	    if any of the new binary matching instructions are used,
+	    the compiler will issue a warning and produce a BEAM file
+	    without native code.</p>
+          <p>
+	    Own Id: OTP-15596</p>
+        </item>
+        <item>
+          <p>
+	    Increased the 'creation' value from 2 to 32 bits. The
+	    'creation' value determines how many times a distributed
+	    node can restart until pids, ports and references may
+	    conflict with such identifiers from an earlier node
+	    incarnation with the same name.</p>
+          <p>
+	    Own Id: OTP-15603</p>
+        </item>
+        <item>
+          <p>
+	    The termination behaviour of processes has changed to
+	    allow processes to yield while sending link exit/monitor
+	    down signals.</p>
+          <p>
+	    The erl crash dump as been expanded to now also include
+	    processes that are termenating but have not yet
+	    terminated.</p>
+          <p>
+	    Own Id: OTP-15610</p>
+        </item>
+        <item>
+          <p>
+	    The dist messages EXIT, EXIT2 and MONITOR_DOWN have been
+	    updated with new versions that send the reason term as
+	    part of the payload of the message instead of as part of
+	    the control message.</p>
+          <p>
+	    The old versions are still present and can be used when
+	    communicating with nodes that don't support the new
+	    versions.</p>
+          <p>
+	    Own Id: OTP-15611</p>
+        </item>
+        <item>
+          <p>
+	    When sending messages, exit, exit2 and monitor down
+	    distributed signals, the process sending will now yield
+	    appropriately.</p>
+          <p>
+	    This means that a terminating process will yield and
+	    possibly be suspended on busy distribution entries while
+	    they are terminating. This means that any memory held by
+	    such processes will not be released until after all
+	    exit/monitor down signals have been sent.</p>
+          <p>
+	    Own Id: OTP-15612</p>
+        </item>
+        <item>
+          <p>
+	    All external pids/ports/refs created by
+	    erlang:list_to_pid/port/ref debug functions now compare
+	    equal to any other pid/port/ref with the same number from
+	    that node.</p>
+          <p>
+	    Before this change they compared differently because the
+	    node creation of the pid/port/ref did not compare equal
+	    to any real pid/port/ref creation.</p>
+          <p>
+	    This will mostly effect pids/ports/refs typed in the
+	    shell.</p>
+          <p>
+	    Own Id: OTP-15613</p>
+        </item>
+        <item>
+          <p>
+	    A new <seealso
+	    marker="erlang#dist_ctrl_set_opt/3"><c>erlang:dist_ctrl_set_opt(DHandle,
+	    get_size, Value)</c></seealso> option has been added.
+	    This option makes it possible to configure the
+	    distribution channel identified by <c>DHandle</c> so that
+	    <seealso
+	    marker="erlang#dist_ctrl_get_data/1"><c>erlang:dist_ctrl_get_data(DHandle)</c></seealso>
+	    also returns the size of the data to pass over the
+	    channel.</p>
+          <p>
+	    Own Id: OTP-15617</p>
+        </item>
+        <item>
+	    <p>The <c>iolist_size/1</c> function is now yielding
+	    which means that an Erlang/OTP system will be responsive
+	    even if the applications running on the system frequently
+	    call <c>iolist_size/1</c> with large iolists.</p>
+          <p>
+	    Own Id: OTP-15631</p>
+        </item>
+        <item>
+          <p>
+	    A simple test suite for the net module has been added.</p>
+          <p>
+	    Own Id: OTP-15635</p>
+        </item>
+        <item>
+	    <p>Added the NIF function <c>enif_term_type</c>, which
+	    helps avoid long sequences of <c>enif_is_xyz</c> by
+	    returning the type of the given term. This is especially
+	    helpful for NIFs that serialize terms, such as JSON
+	    encoders, where it can improve both performance and
+	    readability.</p>
+          <p>
+	    Own Id: OTP-15640</p>
+        </item>
+        <item>
+	    <p>The last call optimization is now applied to BIFs.
+	    When calling a BIF in the tail position of a function,
+	    the return address and stack frame will now be discarded
+	    before calling the BIF. As consequence of this change,
+	    the immediate caller of a tail-called BIF will no longer
+	    be available in stack backtraces.</p>
+          <p>
+	    Own Id: OTP-15674 Aux Id: PR-2177 </p>
+        </item>
+        <item>
+          <p>
+	    Fix GC bug where distributed messages in a processes
+	    mailbox would cause extra GCs. This can be very expensive
+	    if there many messages in the mailbox.</p>
+          <p>
+	    Own Id: OTP-15703</p>
+        </item>
+      </list>
+    </section>
+
+</section>
+
 <section><title>Erts 10.3.1</title>
 
     <section><title>Fixed Bugs and Malfunctions</title>