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<title>Stack allocation</title>
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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="context.econtext.stack"></a><a class="link" href="stack.html" title="Stack allocation">Stack allocation</a>
</h3></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="stack/protected_fixedsize.html">Class
        <span class="emphasis"><em>protected_fixedsize</em></span></a></span></dt>
<dt><span class="section"><a href="stack/fixedsize.html">Class <span class="emphasis"><em>fixedsize</em></span></a></span></dt>
<dt><span class="section"><a href="stack/segmented.html">Class <span class="emphasis"><em>segmented</em></span></a></span></dt>
<dt><span class="section"><a href="stack/stack_traits.html">Class <span class="emphasis"><em>stack_traits</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>
</dl></div>
<p>
        The memory used by the stack is allocated/deallocated via a <span class="emphasis"><em>StackAllocator</em></span>
        which is required to model a <span class="emphasis"><em>stack-allocator concept</em></span>.
      </p>
<h5>
<a name="context.econtext.stack.h0"></a>
        <span><a name="context.econtext.stack._emphasis_stack_allocator_concept__emphasis_"></a></span><a class="link" href="stack.html#context.econtext.stack._emphasis_stack_allocator_concept__emphasis_"><span class="emphasis"><em>stack-allocator
        concept</em></span></a>
      </h5>
<p>
        A <span class="emphasis"><em>StackAllocator</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>StackAllocator</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>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  expression
                </p>
              </th>
<th>
                <p>
                  return type
                </p>
              </th>
<th>
                <p>
                  notes
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">(</span><span class="identifier">size</span><span class="special">)</span></code>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  creates a stack allocator
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">()</span></code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">stack_context</span></code>
                </p>
              </td>
<td>
                <p>
                  creates a stack
                </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>
<td>
                <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>
              </td>
</tr>
</tbody>
</table></div>
<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>
</table></div>
<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>
          Calling <code class="computeroutput"><span class="identifier">deallocate</span><span class="special">()</span></code>
          with a <code class="computeroutput"><span class="identifier">stack_context</span></code> not
          set by <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code>
          results in undefined behaviour.
        </p></td></tr>
</table></div>
<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>
          The stack is not required to be aligned; alignment takes place inside
          <span class="emphasis"><em>execution_context</em></span>.
        </p></td></tr>
</table></div>
<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> stores an address from the top of the
          stack (growing downwards) or the bottom of the stack (growing upwards).
        </p></td></tr>
</table></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2014 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>)
      </p>
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