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26 <div class="titlepage"><div><div><h4 class="title">
27 <a name="context.abstract_context.stack.segmented"></a><a class="link" href="segmented.html" title="Class segmented_stack">Class <span class="emphasis"><em>segmented_stack</em></span></a>
28 </h4></div></div></div>
30 <span class="bold"><strong>Boost.Context</strong></span> supports usage of a <span class="emphasis"><em>segmented_stack</em></span>,
31 e. g. the size of the stack grows on demand. The coroutine is created with
32 a minimal stack size and will be increased as required. Class <span class="emphasis"><em>segmented_stack</em></span>
33 models the <span class="emphasis"><em>stack-allocator concept</em></span>. In contrast to
34 <span class="emphasis"><em>protected_fixedsize_stack</em></span> and <span class="emphasis"><em>fixedsize_stack</em></span>
35 it creates a stack which grows on demand.
37 <div class="note"><table border="0" summary="Note">
39 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
40 <th align="left">Note</th>
42 <tr><td align="left" valign="top"><p>
43 Segmented stacks are currently only supported by <span class="bold"><strong>gcc</strong></span>
44 from version <span class="bold"><strong>4.7</strong></span> <span class="bold"><strong>clang</strong></span>
45 from version <span class="bold"><strong>3.4</strong></span> onwards. In order to
46 use a __segmented_stack__ <span class="bold"><strong>Boost.Context</strong></span>
47 must be built with <span class="bold"><strong>toolset=gcc segmented-stacks=on</strong></span>
48 at b2/bjam command-line. Applications must be compiled with compiler-flags
49 <span class="bold"><strong>-fsplit-stack -DBOOST_USE_SEGMENTED_STACKS</strong></span>.
52 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">context</span><span class="special">/</span><span class="identifier">segmented_stack</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
54 <span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">traitsT</span> <span class="special">></span>
55 <span class="keyword">struct</span> <span class="identifier">basic_segmented_stack</span>
56 <span class="special">{</span>
57 <span class="keyword">typedef</span> <span class="identifier">traitT</span> <span class="identifier">traits_type</span><span class="special">;</span>
59 <span class="identifier">basic_segmented_stack</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span> <span class="special">=</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">default_size</span><span class="special">());</span>
61 <span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">();</span>
63 <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&);</span>
64 <span class="special">}</span>
66 <span class="keyword">typedef</span> <span class="identifier">basic_segmented_stack</span><span class="special"><</span> <span class="identifier">stack_traits</span> <span class="special">></span> <span class="identifier">segmented_stack</span><span class="special">;</span>
69 <a name="context.abstract_context.stack.segmented.h0"></a>
70 <span><a name="context.abstract_context.stack.segmented._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"></a></span><a class="link" href="segmented.html#context.abstract_context.stack.segmented._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"><code class="computeroutput"><span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">()</span></code></a>
72 <div class="variablelist">
73 <p class="title"><b></b></p>
75 <dt><span class="term">Preconditions:</span></dt>
77 <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span>
78 <span class="special"><=</span> <span class="identifier">size</span></code>
79 and <code class="computeroutput"><span class="special">!</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> <span class="special">&&</span>
80 <span class="special">(</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> <span class="special">>=</span>
81 <span class="identifier">size</span><span class="special">)</span></code>.
83 <dt><span class="term">Effects:</span></dt>
85 Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code>
86 Bytes and stores a pointer to the stack and its actual size in <code class="computeroutput"><span class="identifier">sctx</span></code>. Depending on the architecture
87 (the stack grows downwards/upwards) the stored address is the highest/lowest
93 <a name="context.abstract_context.stack.segmented.h1"></a>
94 <span><a name="context.abstract_context.stack.segmented._code__phrase_role__keyword__void__phrase___phrase_role__identifier__deallocate__phrase__phrase_role__special_____phrase___phrase_role__identifier__stack_context__phrase___phrase_role__special___amp___phrase___phrase_role__identifier__sctx__phrase__phrase_role__special_____phrase___code_"></a></span><a class="link" href="segmented.html#context.abstract_context.stack.segmented._code__phrase_role__keyword__void__phrase___phrase_role__identifier__deallocate__phrase__phrase_role__special_____phrase___phrase_role__identifier__stack_context__phrase___phrase_role__special___amp___phrase___phrase_role__identifier__sctx__phrase__phrase_role__special_____phrase___code_"><code class="computeroutput"><span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span>
95 <span class="special">&</span> <span class="identifier">sctx</span><span class="special">)</span></code></a>
97 <div class="variablelist">
98 <p class="title"><b></b></p>
100 <dt><span class="term">Preconditions:</span></dt>
102 <code class="computeroutput"><span class="identifier">sctx</span><span class="special">.</span><span class="identifier">sp</span></code> is valid, <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> <span class="special"><=</span>
103 <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> and <code class="computeroutput"><span class="special">!</span>
104 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span>
105 <span class="special">&&</span> <span class="special">(</span>
106 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span>
107 <span class="special">>=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>.
109 <dt><span class="term">Effects:</span></dt>
111 Deallocates the stack space.
115 <div class="note"><table border="0" summary="Note">
117 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
118 <th align="left">Note</th>
120 <tr><td align="left" valign="top"><p>
121 If the library is compiled for segmented stacks, __segmented_stack__
122 is the only available stack allocator.
126 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
127 <td align="left"></td>
128 <td align="right"><div class="copyright-footer">Copyright © 2014 Oliver Kowalke<p>
129 Distributed under the Boost Software License, Version 1.0. (See accompanying
130 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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