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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="thread.changes"></a><a class="link" href="changes.html" title="Changes since boost 1.40"> Changes since boost 1.40</a>
</h2></div></div></div>
<p>
The 1.41.0 release of Boost adds futures to the thread library. There are also
a few minor changes.
</p>
<a name="thread.changes.changes_since_boost_1_35"></a><h4>
<a name="id2654091"></a>
<a class="link" href="changes.html#thread.changes.changes_since_boost_1_35">Changes since boost
1.35</a>
</h4>
<p>
The 1.36.0 release of Boost includes a few new features in the thread library:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
New generic <a class="link" href="synchronization.html#thread.synchronization.lock_functions.lock_multiple" title="Non-member function lock(Lockable1,Lockable2,...)"><code class="computeroutput"><span class="identifier">lock</span><span class="special">()</span></code></a>
and <a class="link" href="synchronization.html#thread.synchronization.lock_functions.try_lock_multiple" title="Non-member function try_lock(Lockable1,Lockable2,...)"><code class="computeroutput"><span class="identifier">try_lock</span><span class="special">()</span></code></a>
functions for locking multiple mutexes at once.
</li>
<li class="listitem">
Rvalue reference support for move semantics where the compilers supports
it.
</li>
<li class="listitem">
A few bugs fixed and missing functions added (including the serious win32
condition variable bug).
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">scoped_try_lock</span></code> types are
now backwards-compatible with Boost 1.34.0 and previous releases.
</li>
<li class="listitem">
Support for passing function arguments to the thread function by supplying
additional arguments to the <a class="link" href="thread_management.html#thread.thread_management.thread" title="Class thread"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span></code></a> constructor.
</li>
<li class="listitem">
Backwards-compatibility overloads added for <code class="computeroutput"><span class="identifier">timed_lock</span></code>
and <code class="computeroutput"><span class="identifier">timed_wait</span></code> functions
to allow use of <code class="computeroutput"><span class="identifier">xtime</span></code> for
timeouts.
</li>
</ul></div>
<a name="thread.changes.changes_since_boost_1_34"></a><h4>
<a name="id2654272"></a>
<a class="link" href="changes.html#thread.changes.changes_since_boost_1_34">Changes since boost
1.34</a>
</h4>
<p>
Almost every line of code in <span class="bold"><strong>Boost.Thread</strong></span>
has been changed since the 1.34 release of boost. However, most of the interface
changes have been extensions, so the new code is largely backwards-compatible
with the old code. The new features and breaking changes are described below.
</p>
<a name="thread.changes.new_features"></a><h4>
<a name="id2654306"></a>
<a class="link" href="changes.html#thread.changes.new_features">New Features</a>
</h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
Instances of <a class="link" href="thread_management.html#thread.thread_management.thread" title="Class thread"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span></code></a> and of the various lock
types are now movable.
</li>
<li class="listitem">
Threads can be interrupted at <a class="link" href="thread_management.html#interruption_points"><span class="emphasis"><em>interruption
points</em></span></a>.
</li>
<li class="listitem">
Condition variables can now be used with any type that implements the
<a class="link" href="synchronization.html#thread.synchronization.mutex_concepts.lockable" title="Lockable Concept"><code class="computeroutput"><span class="identifier">Lockable</span></code> concept</a>, through the
use of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition_variable_any</span></code> (<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition</span></code> is a <code class="computeroutput"><span class="keyword">typedef</span></code>
to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition_variable_any</span></code>, provided for
backwards compatibility). <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition_variable</span></code>
is provided as an optimization, and will only work with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unique_lock</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">></span></code> (<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">::</span><span class="identifier">scoped_lock</span></code>).
</li>
<li class="listitem">
Thread IDs are separated from <a class="link" href="thread_management.html#thread.thread_management.thread" title="Class thread"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span></code></a>, so a thread can obtain
it's own ID (using <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">get_id</span><span class="special">()</span></code>), and IDs can be used as keys in associative
containers, as they have the full set of comparison operators.
</li>
<li class="listitem">
Timeouts are now implemented using the Boost DateTime library, through
a typedef <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">system_time</span></code> for absolute timeouts, and
with support for relative timeouts in many cases. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">xtime</span></code>
is supported for backwards compatibility only.
</li>
<li class="listitem">
Locks are implemented as publicly accessible templates <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">lock_guard</span></code>,
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unique_lock</span></code>, <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_lock</span></code>,
and <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">upgrade_lock</span></code>, which are templated on
the type of the mutex. The <a class="link" href="synchronization.html#thread.synchronization.mutex_concepts.lockable" title="Lockable Concept"><code class="computeroutput"><span class="identifier">Lockable</span></code> concept</a> has been extended
to include publicly available <a class="link" href="synchronization.html#thread.synchronization.mutex_concepts.lockable.lock" title="void lock()"><code class="computeroutput"><span class="identifier">lock</span><span class="special">()</span></code></a>
and <a class="link" href="synchronization.html#thread.synchronization.mutex_concepts.lockable.unlock" title="void unlock()"><code class="computeroutput"><span class="identifier">unlock</span><span class="special">()</span></code></a>
member functions, which are used by the lock types.
</li>
</ul></div>
<a name="thread.changes.breaking_changes"></a><h4>
<a name="id2654800"></a>
<a class="link" href="changes.html#thread.changes.breaking_changes">Breaking Changes</a>
</h4>
<p>
The list below should cover all changes to the public interface which break
backwards compatibility.
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
<a class="link" href="synchronization.html#thread.synchronization.mutex_types.try_mutex" title="Typedef try_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">try_mutex</span></code></a> has been removed, and
the functionality subsumed into <a class="link" href="synchronization.html#thread.synchronization.mutex_types.mutex" title="Class mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span></code></a>. <a class="link" href="synchronization.html#thread.synchronization.mutex_types.try_mutex" title="Typedef try_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">try_mutex</span></code></a> is left as a <code class="computeroutput"><span class="keyword">typedef</span></code>, but is no longer a separate class.
</li>
<li class="listitem">
<a class="link" href="synchronization.html#thread.synchronization.mutex_types.recursive_try_mutex" title="Typedef recursive_try_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">recursive_try_mutex</span></code></a> has been removed,
and the functionality subsumed into <a class="link" href="synchronization.html#thread.synchronization.mutex_types.recursive_mutex" title="Class recursive_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">recursive_mutex</span></code></a>. <a class="link" href="synchronization.html#thread.synchronization.mutex_types.recursive_try_mutex" title="Typedef recursive_try_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">recursive_try_mutex</span></code></a> is left as
a <code class="computeroutput"><span class="keyword">typedef</span></code>, but is no longer
a separate class.
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">thread</span><span class="special">::</span><span class="identifier">lock_ops</span></code> has been removed. Code that
relies on the <code class="computeroutput"><span class="identifier">lock_ops</span></code>
implementation detail will no longer work, as this has been removed, as
it is no longer necessary now that mutex types now have public <a class="link" href="synchronization.html#thread.synchronization.mutex_concepts.lockable.lock" title="void lock()"><code class="computeroutput"><span class="identifier">lock</span><span class="special">()</span></code></a>
and <a class="link" href="synchronization.html#thread.synchronization.mutex_concepts.lockable.unlock" title="void unlock()"><code class="computeroutput"><span class="identifier">unlock</span><span class="special">()</span></code></a>
member functions.
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">scoped_lock</span></code> constructors
with a second parameter of type <code class="computeroutput"><span class="keyword">bool</span></code>
are no longer provided. With previous boost releases,
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">::</span><span class="identifier">scoped_lock</span> <span class="identifier">some_lock</span><span class="special">(</span><span class="identifier">some_mutex</span><span class="special">,</span><span class="keyword">false</span><span class="special">);</span></pre>
could be used to create a lock object that was associated with a mutex,
but did not lock it on construction. This facility has now been replaced
with the constructor that takes a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">defer_lock_type</span></code>
as the second parameter:
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">::</span><span class="identifier">scoped_lock</span> <span class="identifier">some_lock</span><span class="special">(</span><span class="identifier">some_mutex</span><span class="special">,</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">defer_lock</span><span class="special">);</span></pre>
</li>
<li class="listitem">
The <code class="computeroutput"><span class="identifier">locked</span><span class="special">()</span></code>
member function of the <code class="computeroutput"><span class="identifier">scoped_lock</span></code>
types has been renamed to <a class="link" href="synchronization.html#thread.synchronization.locks.unique_lock.owns_lock" title="bool owns_lock() const"><code class="computeroutput"><span class="identifier">owns_lock</span><span class="special">()</span></code></a>.
</li>
<li class="listitem">
You can no longer obtain a <a class="link" href="thread_management.html#thread.thread_management.thread" title="Class thread"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span></code></a> instance representing the
current thread: a default-constructed <a class="link" href="thread_management.html#thread.thread_management.thread" title="Class thread"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span></code></a> object is not associated
with any thread. The only use for such a thread object was to support the
comparison operators: this functionality has been moved to <a class="link" href="thread_management.html#thread.thread_management.thread.id" title="Class boost::thread::id"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span><span class="special">::</span><span class="identifier">id</span></code></a>.
</li>
<li class="listitem">
The broken <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">read_write_mutex</span></code> has been replaced with
<a class="link" href="synchronization.html#thread.synchronization.mutex_types.shared_mutex" title="Class shared_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_mutex</span></code></a>.
</li>
<li class="listitem">
<a class="link" href="synchronization.html#thread.synchronization.mutex_types.mutex" title="Class mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span></code></a> is now never recursive.
For Boost releases prior to 1.35 <a class="link" href="synchronization.html#thread.synchronization.mutex_types.mutex" title="Class mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span></code></a> was recursive on Windows
and not on POSIX platforms.
</li>
<li class="listitem">
When using a <a class="link" href="synchronization.html#thread.synchronization.mutex_types.recursive_mutex" title="Class recursive_mutex"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">recursive_mutex</span></code></a> with a call to
<a class="link" href="synchronization.html#thread.synchronization.condvar_ref.condition_variable_any.wait" title="template<typename lock_type> void wait(lock_type& lock)"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition_variable_any</span><span class="special">::</span><span class="identifier">wait</span><span class="special">()</span></code></a>,
the mutex is only unlocked one level, and not completely. This prior behaviour
was not guaranteed and did not feature in the tests.
</li>
</ul></div>
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<td align="right"><div class="copyright-footer">Copyright © 2007 -8 Anthony Williams<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
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