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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="coroutine.stack"></a><a class="link" href="stack.html" title="Stack allocation">Stack allocation</a>
</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="stack/protected_stack_allocator.html">Class <span class="emphasis"><em>protected_stack_allocator</em></span></a></span></dt>
<dt><span class="section"><a href="stack/standard_stack_allocator.html">Class <span class="emphasis"><em>standard_stack_allocator</em></span></a></span></dt>
<dt><span class="section"><a href="stack/stack_context.html">Class <span class="emphasis"><em>stack_context</em></span></a></span></dt>
<dt><span class="section"><a href="stack/segmented_stack.html">Segmented stacks</a></span></dt>
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<p>
A <span class="emphasis"><em>coroutine</em></span> uses internally a <span class="emphasis"><em>context</em></span>
which manages a set of registers and a stack. The memory used by the stack
is allocated/deallocated via a <span class="emphasis"><em>stack-allocator</em></span> which is
required to model a <span class="emphasis"><em>stack-allocator concept</em></span>.
</p>
<h4>
<a name="coroutine.stack.h0"></a>
<span><a name="coroutine.stack._emphasis_stack_allocator_concept__emphasis_"></a></span><a class="link" href="stack.html#coroutine.stack._emphasis_stack_allocator_concept__emphasis_"><span class="emphasis"><em>stack-allocator
concept</em></span></a>
</h4>
<p>
A <span class="emphasis"><em>stack-allocator</em></span> must satisfy the <span class="emphasis"><em>stack-allocator
concept</em></span> requirements shown in the following table, in which <code class="computeroutput"><span class="identifier">a</span></code> is an object of a <span class="emphasis"><em>stack-allocator</em></span>
type, <code class="computeroutput"><span class="identifier">sctx</span></code> is a <code class="computeroutput"><span class="identifier">stack_context</span></code>, and <code class="computeroutput"><span class="identifier">size</span></code>
is a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span></code>:
</p>
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expression
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return type
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notes
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<p>
<code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">(</span>
<span class="identifier">sctx</span><span class="special">,</span>
<span class="identifier">size</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">void</span></code>
</p>
</td>
<td>
<p>
creates a stack of at least <code class="computeroutput"><span class="identifier">size</span></code>
bytes and stores both values in <code class="computeroutput"><span class="identifier">sctx</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">deallocate</span><span class="special">(</span>
<span class="identifier">sctx</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">void</span></code>
</p>
</td>
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<p>
deallocates the stack created by <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">()</span></code>
</p>
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<div class="important"><table border="0" summary="Important">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../doc/src/images/important.png"></td>
<th align="left">Important</th>
</tr>
<tr><td align="left" valign="top"><p>
The implementation of <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code> might include logic to protect against
exceeding the context's available stack size rather than leaving it as undefined
behaviour.
</p></td></tr>
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<div class="important"><table border="0" summary="Important">
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<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../doc/src/images/important.png"></td>
<th align="left">Important</th>
</tr>
<tr><td align="left" valign="top"><p>
Calling <code class="computeroutput"><span class="identifier">deallocate</span><span class="special">()</span></code>
with a pointer not returned by <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code> results in undefined behaviour.
</p></td></tr>
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<th align="left">Note</th>
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<tr><td align="left" valign="top"><p>
The stack is not required to be aligned; alignment takes place inside <span class="emphasis"><em>coroutine</em></span>.
</p></td></tr>
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<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
Depending on the architecture <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code> returns an address from the top of the
stack (growing downwards) or the bottom of the stack (growing upwards).
</p></td></tr>
</table></div>
<p>
class <span class="emphasis"><em>boost::coroutines::stack_allocator</em></span> is a typedef
of <span class="emphasis"><em>boost::coroutines::standard_stack_allocator</em></span>.
</p>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2009 Oliver Kowalke<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>)
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