ceph/src/boost/libs/context/doc/html/context/econtext/stack.html

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  25 <div class="section">
  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="context.econtext.stack"></a><a class="link" href="stack.html" title="Stack allocation">Stack allocation</a>
  28 </h3></div></div></div>
  29 <div class="toc"><dl>
  30 <dt><span class="section"><a href="stack/protected_fixedsize.html">Class
  31         <span class="emphasis"><em>protected_fixedsize</em></span></a></span></dt>
  32 <dt><span class="section"><a href="stack/fixedsize.html">Class <span class="emphasis"><em>fixedsize</em></span></a></span></dt>
  33 <dt><span class="section"><a href="stack/segmented.html">Class <span class="emphasis"><em>segmented</em></span></a></span></dt>
  34 <dt><span class="section"><a href="stack/stack_traits.html">Class <span class="emphasis"><em>stack_traits</em></span></a></span></dt>
  35 <dt><span class="section"><a href="stack/stack_context.html">Class <span class="emphasis"><em>stack_context</em></span></a></span></dt>
  36 </dl></div>
  37 <p>
  38         The memory used by the stack is allocated/deallocated via a <span class="emphasis"><em>StackAllocator</em></span>
  39         which is required to model a <span class="emphasis"><em>stack-allocator concept</em></span>.
  40       </p>
  41 <h5>
  42 <a name="context.econtext.stack.h0"></a>
  43         <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
  44         concept</em></span></a>
  45       </h5>
  46 <p>
  47         A <span class="emphasis"><em>StackAllocator</em></span> must satisfy the <span class="emphasis"><em>stack-allocator
  48         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>
  49         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>
  50         is a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span></code>:
  51       </p>
  52 <div class="informaltable"><table class="table">
  53 <colgroup>
  54 <col>
  55 <col>
  56 <col>
  57 </colgroup>
  58 <thead><tr>
  59 <th>
  60                 <p>
  61                   expression
  62                 </p>
  63               </th>
  64 <th>
  65                 <p>
  66                   return type
  67                 </p>
  68               </th>
  69 <th>
  70                 <p>
  71                   notes
  72                 </p>
  73               </th>
  74 </tr></thead>
  75 <tbody>
  76 <tr>
  77 <td>
  78                 <p>
  79                   <code class="computeroutput"><span class="identifier">a</span><span class="special">(</span><span class="identifier">size</span><span class="special">)</span></code>
  80                 </p>
  81               </td>
  82 <td>
  83               </td>
  84 <td>
  85                 <p>
  86                   creates a stack allocator
  87                 </p>
  88               </td>
  89 </tr>
  90 <tr>
  91 <td>
  92                 <p>
  93                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">()</span></code>
  94                 </p>
  95               </td>
  96 <td>
  97                 <p>
  98                   <code class="computeroutput"><span class="identifier">stack_context</span></code>
  99                 </p>
 100               </td>
 101 <td>
 102                 <p>
 103                   creates a stack
 104                 </p>
 105               </td>
 106 </tr>
 107 <tr>
 108 <td>
 109                 <p>
 110                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">deallocate</span><span class="special">(</span>
 111                   <span class="identifier">sctx</span><span class="special">)</span></code>
 112                 </p>
 113               </td>
 114 <td>
 115                 <p>
 116                   <code class="computeroutput"><span class="keyword">void</span></code>
 117                 </p>
 118               </td>
 119 <td>
 120                 <p>
 121                   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>
 122                 </p>
 123               </td>
 124 </tr>
 125 </tbody>
 126 </table></div>
 127 <div class="important"><table border="0" summary="Important">
 128 <tr>
 129 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td>
 130 <th align="left">Important</th>
 131 </tr>
 132 <tr><td align="left" valign="top"><p>
 133           The implementation of <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code> might include logic to protect against
 134           exceeding the context's available stack size rather than leaving it as
 135           undefined behaviour.
 136         </p></td></tr>
 137 </table></div>
 138 <div class="important"><table border="0" summary="Important">
 139 <tr>
 140 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td>
 141 <th align="left">Important</th>
 142 </tr>
 143 <tr><td align="left" valign="top"><p>
 144           Calling <code class="computeroutput"><span class="identifier">deallocate</span><span class="special">()</span></code>
 145           with a <code class="computeroutput"><span class="identifier">stack_context</span></code> not
 146           set by <code class="computeroutput"><span class="identifier">allocate</span><span class="special">()</span></code>
 147           results in undefined behaviour.
 148         </p></td></tr>
 149 </table></div>
 150 <div class="note"><table border="0" summary="Note">
 151 <tr>
 152 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
 153 <th align="left">Note</th>
 154 </tr>
 155 <tr><td align="left" valign="top"><p>
 156           The stack is not required to be aligned; alignment takes place inside
 157           <span class="emphasis"><em>execution_context</em></span>.
 158         </p></td></tr>
 159 </table></div>
 160 <div class="note"><table border="0" summary="Note">
 161 <tr>
 162 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
 163 <th align="left">Note</th>
 164 </tr>
 165 <tr><td align="left" valign="top"><p>
 166           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
 167           stack (growing downwards) or the bottom of the stack (growing upwards).
 168         </p></td></tr>
 169 </table></div>
 170 </div>
 171 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 172 <td align="left"></td>
 173 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Oliver Kowalke<p>
 174         Distributed under the Boost Software License, Version 1.0. (See accompanying
 175         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>)
 176       </p>
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