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  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="context.ecv1_class"></a><a name="ecv1"></a><a class="link" href="ecv1_class.html" title="Class execution_context (version 1)">Class execution_context
  28     (version 1)</a>
  29 </h2></div></div></div>
  30 <div class="note"><table border="0" summary="Note">
  31 <tr>
  32 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
  33 <th align="left">Note</th>
  34 </tr>
  35 <tr><td align="left" valign="top"><p>
  36         This class is enabled if segmented stacks (property <span class="emphasis"><em>segmented-stacks=on</em></span>)
  37         are used or <span class="emphasis"><em>BOOST_EXECUTION_CONTEXT=1</em></span> is specified at
  38         b2-commandline.
  39       </p></td></tr>
  40 </table></div>
  41 <p>
  42       Class <span class="emphasis"><em>execution_context</em></span> encapsulates context switching
  43       and manages the associated context' stack (allocation/deallocation).
  44     </p>
  45 <p>
  46       <span class="emphasis"><em>execution_context</em></span> allocates the context stack (using its
  47       <a class="link" href="stack.html#stack"><span class="emphasis"><em>StackAllocator</em></span></a> argument)
  48       and creates a control structure on top of it. This structure is responsible
  49       for managing context' stack. Instances of <span class="emphasis"><em>execution_context</em></span>,
  50       associated with a specific context, share the ownership of the control structure.
  51       If the last reference goes out of scope, the control structure is destroyed
  52       and the stack gets deallocated via the <span class="emphasis"><em>StackAllocator</em></span>.
  53     </p>
  54 <p>
  55       <span class="emphasis"><em>execution_context</em></span> is copy-constructible, move-constructible,
  56       copy-assignable and move-assignable.
  57     </p>
  58 <p>
  59       <span class="emphasis"><em>execution_context</em></span> maintains a static (thread-local) pointer,
  60       accessed by <span class="emphasis"><em>execution_context::current()</em></span>, pointing to
  61       the active context. On each context switch the pointer is updated. The usage
  62       of this global pointer makes the context switch a little bit slower (due access
  63       of thread local storage) but has some advantages. It allows to access the control
  64       structure of the current active context from arbitrary code paths required
  65       in order to support segmented stacks, which require to call certain maintenance
  66       functions (like __splitstack_getcontext() etc.) before each context switch
  67       (each context switch exchanges the stack).
  68     </p>
  69 <p>
  70       <span class="emphasis"><em>execution_context</em></span> expects a function/functor with signature
  71       <code class="computeroutput"><span class="keyword">void</span><span class="special">(</span><span class="keyword">void</span><span class="special">*</span> <span class="identifier">vp</span><span class="special">)</span></code> (<code class="computeroutput"><span class="identifier">vp</span></code>
  72       is the data passed at the first invocation of <a class="link" href="../"> <code class="computeroutput">execution_context::operator()()</code></a>).
  73     </p>
  74 <h4>
  75 <a name="context.ecv1_class.h0"></a>
  76       <span><a name="context.ecv1_class.usage_of__emphasis_execution_context__emphasis_"></a></span><a class="link" href="ecv1_class.html#context.ecv1_class.usage_of__emphasis_execution_context__emphasis_">usage
  77       of <span class="emphasis"><em>execution_context</em></span></a>
  78     </h4>
  79 <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">n</span><span class="special">=</span><span class="number">35</span><span class="special">;</span>
  80 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">execution_context</span> <span class="identifier">sink</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">execution_context</span><span class="special">::</span><span class="identifier">current</span><span class="special">());</span>
  81 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">execution_context</span> <span class="identifier">source</span><span class="special">(</span>
  82     <span class="special">[</span><span class="identifier">n</span><span class="special">,&amp;</span><span class="identifier">sink</span><span class="special">](</span><span class="keyword">void</span><span class="special">*)</span><span class="keyword">mutable</span><span class="special">{</span>
  83         <span class="keyword">int</span> <span class="identifier">a</span><span class="special">=</span><span class="number">0</span><span class="special">;</span>
  84         <span class="keyword">int</span> <span class="identifier">b</span><span class="special">=</span><span class="number">1</span><span class="special">;</span>
  85         <span class="keyword">while</span><span class="special">(</span><span class="identifier">n</span><span class="special">--&gt;</span><span class="number">0</span><span class="special">){</span>
  86             <span class="identifier">sink</span><span class="special">(&amp;</span><span class="identifier">a</span><span class="special">);</span>
  87             <span class="keyword">auto</span> <span class="identifier">next</span><span class="special">=</span><span class="identifier">a</span><span class="special">+</span><span class="identifier">b</span><span class="special">;</span>
  88             <span class="identifier">a</span><span class="special">=</span><span class="identifier">b</span><span class="special">;</span>
  89             <span class="identifier">b</span><span class="special">=</span><span class="identifier">next</span><span class="special">;</span>
  90         <span class="special">}</span>
  91     <span class="special">});</span>
  92 <span class="keyword">for</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span><span class="special">=</span><span class="number">0</span><span class="special">;</span><span class="identifier">i</span><span class="special">&lt;</span><span class="number">10</span><span class="special">;++</span><span class="identifier">i</span><span class="special">){</span>
  93     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;*(</span><span class="keyword">int</span><span class="special">*)</span><span class="identifier">source</span><span class="special">()&lt;&lt;</span><span class="string">" "</span><span class="special">;</span>
  94 <span class="special">}</span>
  95
  96 <span class="identifier">output</span><span class="special">:</span>
  97     <span class="number">0</span> <span class="number">1</span> <span class="number">1</span> <span class="number">2</span> <span class="number">3</span> <span class="number">5</span> <span class="number">8</span> <span class="number">13</span> <span class="number">21</span> <span class="number">34</span>
  98 </pre>
  99 <p>
 100       This simple example demonstrates the basic usage of <span class="emphasis"><em>execution_context</em></span>.
 101       The context <code class="computeroutput"><span class="identifier">sink</span></code>, returned
 102       by <span class="emphasis"><em>execution_context::current()</em></span>, represents the <span class="emphasis"><em>main</em></span>-context
 103       (function <span class="emphasis"><em>main()</em></span> running) and is one of the captured parameters
 104       in the lambda expression. The lambda that calculates the Fibonacci numbers
 105       is executed inside the context represented by <code class="computeroutput"><span class="identifier">source</span></code>.
 106       Calculated Fibonacci numbers are transferred between the two context' via expression
 107       <span class="emphasis"><em>sink(&amp;a)</em></span> (and returned by <span class="emphasis"><em>source()</em></span>).
 108     </p>
 109 <p>
 110       The locale variables <code class="computeroutput"><span class="identifier">a</span></code>, <code class="computeroutput"><span class="identifier">b</span></code> and <code class="computeroutput"> <span class="identifier">next</span></code>
 111       remain their values during each context switch (<span class="emphasis"><em>yield(a)</em></span>).
 112       This is possible because <code class="computeroutput"><span class="identifier">ctx</span></code>
 113       owns a stack (exchanged by context switch).
 114     </p>
 115 <h4>
 116 <a name="context.ecv1_class.h1"></a>
 117       <span><a name="context.ecv1_class.inverting_the_control_flow"></a></span><a class="link" href="ecv1_class.html#context.ecv1_class.inverting_the_control_flow">inverting
 118       the control flow</a>
 119     </h4>
 120 <pre class="programlisting"><span class="comment">/*
 121  * grammar:
 122  *   P ---&gt; E '\0'
 123  *   E ---&gt; T {('+'|'-') T}
 124  *   T ---&gt; S {('*'|'/') S}
 125  *   S ---&gt; digit | '(' E ')'
 126  */</span>
 127 <span class="keyword">class</span> <span class="identifier">Parser</span><span class="special">{</span>
 128     <span class="comment">// implementation omitted; see examples directory</span>
 129 <span class="special">};</span>
 130
 131 <span class="identifier">std</span><span class="special">::</span><span class="identifier">istringstream</span> <span class="identifier">is</span><span class="special">(</span><span class="string">"1+1"</span><span class="special">);</span>
 132 <span class="keyword">bool</span> <span class="identifier">done</span><span class="special">=</span><span class="keyword">false</span><span class="special">;</span>
 133 <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception_ptr</span> <span class="identifier">except</span><span class="special">;</span>
 134
 135 <span class="comment">// create handle to main execution context</span>
 136 <span class="keyword">auto</span> <span class="identifier">main_ctx</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">execution_context</span><span class="special">::</span><span class="identifier">current</span><span class="special">());</span>
 137 <span class="comment">// execute parser in new execution context</span>
 138 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">execution_context</span> <span class="identifier">source</span><span class="special">(</span>
 139         <span class="special">[&amp;</span><span class="identifier">sink</span><span class="special">,&amp;</span><span class="identifier">is</span><span class="special">,&amp;</span><span class="identifier">done</span><span class="special">,&amp;</span><span class="identifier">except</span><span class="special">](</span><span class="keyword">void</span><span class="special">*){</span>
 140         <span class="comment">// create parser with callback function</span>
 141         <span class="identifier">Parser</span> <span class="identifier">p</span><span class="special">(</span><span class="identifier">is</span><span class="special">,</span>
 142                  <span class="special">[&amp;</span><span class="identifier">sink</span><span class="special">](</span><span class="keyword">char</span> <span class="identifier">ch</span><span class="special">){</span>
 143                         <span class="comment">// resume main execution context</span>
 144                         <span class="identifier">sink</span><span class="special">(&amp;</span><span class="identifier">ch</span><span class="special">);</span>
 145                 <span class="special">});</span>
 146             <span class="keyword">try</span> <span class="special">{</span>
 147                 <span class="comment">// start recursive parsing</span>
 148                 <span class="identifier">p</span><span class="special">.</span><span class="identifier">run</span><span class="special">();</span>
 149             <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(...)</span> <span class="special">{</span>
 150                 <span class="comment">// store other exceptions in exception-pointer</span>
 151                 <span class="identifier">except</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">current_exception</span><span class="special">();</span>
 152             <span class="special">}</span>
 153             <span class="comment">// set termination flag</span>
 154             <span class="identifier">done</span><span class="special">=</span><span class="keyword">true</span><span class="special">;</span>
 155             <span class="comment">// resume main execution context</span>
 156             <span class="identifier">sink</span><span class="special">();</span>
 157         <span class="special">});</span>
 158
 159 <span class="comment">// user-code pulls parsed data from parser</span>
 160 <span class="comment">// invert control flow</span>
 161 <span class="keyword">void</span><span class="special">*</span> <span class="identifier">vp</span> <span class="special">=</span> <span class="identifier">source</span><span class="special">();</span>
 162 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">except</span><span class="special">)</span> <span class="special">{</span>
 163     <span class="identifier">std</span><span class="special">::</span><span class="identifier">rethrow_exception</span><span class="special">(</span><span class="identifier">except</span><span class="special">);</span>
 164 <span class="special">}</span>
 165 <span class="keyword">while</span><span class="special">(</span> <span class="special">!</span> <span class="identifier">done</span><span class="special">)</span> <span class="special">{</span>
 166     <span class="identifier">printf</span><span class="special">(</span><span class="string">"Parsed: %c\n"</span><span class="special">,*</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">*&gt;(</span><span class="identifier">vp</span><span class="special">));</span>
 167     <span class="identifier">vp</span> <span class="special">=</span> <span class="identifier">source</span><span class="special">();</span>
 168     <span class="keyword">if</span> <span class="special">(</span><span class="identifier">except</span><span class="special">)</span> <span class="special">{</span>
 169         <span class="identifier">std</span><span class="special">::</span><span class="identifier">rethrow_exception</span><span class="special">(</span><span class="identifier">except</span><span class="special">);</span>
 170     <span class="special">}</span>
 171 <span class="special">}</span>
 172
 173 <span class="identifier">output</span><span class="special">:</span>
 174     <span class="identifier">Parsed</span><span class="special">:</span> <span class="number">1</span>
 175     <span class="identifier">Parsed</span><span class="special">:</span> <span class="special">+</span>
 176     <span class="identifier">Parsed</span><span class="special">:</span> <span class="number">1</span>
 177 </pre>
 178 <p>
 179       In this example a recursive descent parser uses a callback to emit a newly
 180       passed symbol. Using <span class="emphasis"><em>execution_context</em></span> the control flow
 181       can be inverted, e.g. the user-code pulls parsed symbols from the parser -
 182       instead to get pushed from the parser (via callback).
 183     </p>
 184 <p>
 185       The data (character) is transferred between the two <span class="emphasis"><em>execution_context</em></span>.
 186     </p>
 187 <p>
 188       If the code executed by <span class="emphasis"><em>execution_context</em></span> emits an exception,
 189       the application is terminated. <span class="emphasis"><em>std::exception_ptr</em></span> can
 190       be used to transfer exceptions between different execution contexts.
 191     </p>
 192 <p>
 193       Sometimes it is necessary to unwind the stack of an unfinished context to destroy
 194       local stack variables so they can release allocated resources (RAII pattern).
 195       The user is responsible for this task.
 196     </p>
 197 <a name="ecv1_prealloc"></a><h4>
 198 <a name="context.ecv1_class.h2"></a>
 199       <span><a name="context.ecv1_class.allocating_control_structures_on_top_of_stack"></a></span><a class="link" href="ecv1_class.html#context.ecv1_class.allocating_control_structures_on_top_of_stack">allocating
 200       control structures on top of stack</a>
 201     </h4>
 202 <p>
 203       Allocating control structures on top of the stack requires to allocated the
 204       <span class="emphasis"><em>stack_context</em></span> and create the control structure with placement
 205       new before <span class="emphasis"><em>execution_context</em></span> is created.
 206     </p>
 207 <div class="note"><table border="0" summary="Note">
 208 <tr>
 209 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
 210 <th align="left">Note</th>
 211 </tr>
 212 <tr><td align="left" valign="top"><p>
 213         The user is responsible for destructing the control structure at the top
 214         of the stack.
 215       </p></td></tr>
 216 </table></div>
 217 <pre class="programlisting"><span class="comment">// stack-allocator used for (de-)allocating stack</span>
 218 <span class="identifier">fixedsize_stack</span> <span class="identifier">salloc</span><span class="special">(</span> <span class="number">4048</span><span class="special">);</span>
 219 <span class="comment">// allocate stack space</span>
 220 <span class="identifier">stack_context</span> <span class="identifier">sctx</span><span class="special">(</span> <span class="identifier">salloc</span><span class="special">.</span><span class="identifier">allocate</span><span class="special">()</span> <span class="special">);</span>
 221 <span class="comment">// reserve space for control structure on top of the stack</span>
 222 <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">sp</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special">&lt;</span> <span class="keyword">char</span> <span class="special">*</span> <span class="special">&gt;(</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">sp</span><span class="special">)</span> <span class="special">-</span> <span class="keyword">sizeof</span><span class="special">(</span> <span class="identifier">my_control_structure</span><span class="special">);</span>
 223 <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">sctx</span><span class="special">.</span><span class="identifier">size</span> <span class="special">-</span> <span class="keyword">sizeof</span><span class="special">(</span> <span class="identifier">my_control_structure</span><span class="special">);</span>
 224 <span class="comment">// placement new creates control structure on reserved space</span>
 225 <span class="identifier">my_control_structure</span> <span class="special">*</span> <span class="identifier">cs</span> <span class="special">=</span> <span class="keyword">new</span> <span class="special">(</span> <span class="identifier">sp</span><span class="special">)</span> <span class="identifier">my_control_structure</span><span class="special">(</span> <span class="identifier">sp</span><span class="special">,</span> <span class="identifier">size</span><span class="special">,</span> <span class="identifier">sctx</span><span class="special">,</span> <span class="identifier">salloc</span><span class="special">);</span>
 226 <span class="special">...</span>
 227 <span class="comment">// destructing the control structure</span>
 228 <span class="identifier">cs</span><span class="special">-&gt;~</span><span class="identifier">my_control_structure</span><span class="special">();</span>
 229 <span class="special">...</span>
 230 <span class="keyword">struct</span> <span class="identifier">my_control_structure</span>  <span class="special">{</span>
 231     <span class="comment">// execution context</span>
 232     <span class="identifier">execution_context</span> <span class="identifier">ectx</span><span class="special">;</span>
 233
 234     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAllocator</span> <span class="special">&gt;</span>
 235     <span class="identifier">my_control_structure</span><span class="special">(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">sp</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">stack_context</span> <span class="identifier">sctx</span><span class="special">,</span> <span class="identifier">StackAllocator</span> <span class="identifier">salloc</span><span class="special">)</span> <span class="special">:</span>
 236         <span class="comment">// create execution context</span>
 237         <span class="identifier">ectx</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg</span><span class="special">,</span> <span class="identifier">preallocated</span><span class="special">(</span> <span class="identifier">sp</span><span class="special">,</span> <span class="identifier">size</span><span class="special">,</span> <span class="identifier">sctx</span><span class="special">),</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">entry_func</span><span class="special">)</span> <span class="special">{</span>
 238     <span class="special">}</span>
 239     <span class="special">...</span>
 240 <span class="special">};</span>
 241 </pre>
 242 <h4>
 243 <a name="context.ecv1_class.h3"></a>
 244       <span><a name="context.ecv1_class.exception_handling"></a></span><a class="link" href="ecv1_class.html#context.ecv1_class.exception_handling">exception
 245       handling</a>
 246     </h4>
 247 <p>
 248       If the function executed inside a <span class="emphasis"><em>execution_context</em></span> emits
 249       ans exception, the application is terminated by calling <span class="emphasis"><em>std::terminate()</em></span>.
 250       <span class="emphasis"><em>std::exception_ptr</em></span> can be used to transfer exceptions
 251       between different execution contexts.
 252     </p>
 253 <h4>
 254 <a name="context.ecv1_class.h4"></a>
 255       <span><a name="context.ecv1_class.parameter_passing"></a></span><a class="link" href="ecv1_class.html#context.ecv1_class.parameter_passing">parameter
 256       passing</a>
 257     </h4>
 258 <p>
 259       The void pointer argument passed to <span class="emphasis"><em>execution_context::operator()</em></span>,
 260       in one context, is passed as the last argument of the <span class="emphasis"><em>context-function</em></span>
 261       if the context is started for the first time. In all following invocations
 262       of <span class="emphasis"><em>execution_context::operator()</em></span> the void pointer passed
 263       to <span class="emphasis"><em>execution_context::operator()</em></span>, in one context, is returned
 264       by <span class="emphasis"><em>execution_context::operator()</em></span> in the other context.
 265     </p>
 266 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">X</span> <span class="special">{</span>
 267 <span class="keyword">private</span><span class="special">:</span>
 268     <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception_ptr</span> <span class="identifier">excptr_</span><span class="special">;</span>
 269     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">execution_context</span> <span class="identifier">caller_</span><span class="special">;</span>
 270     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">context</span><span class="special">::</span><span class="identifier">execution_context</span> <span class="identifier">callee_</span><span class="special">;</span>
 271
 272 <span class="keyword">public</span><span class="special">:</span>
 273     <span class="identifier">X</span><span class="special">()</span> <span class="special">:</span>
 274         <span class="identifier">excptr_</span><span class="special">(),</span>
 275         <span class="identifier">caller_</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">execution_context</span><span class="special">::</span><span class="identifier">current</span><span class="special">()</span> <span class="special">),</span>
 276         <span class="identifier">callee_</span><span class="special">(</span> <span class="special">[=]</span> <span class="special">(</span><span class="keyword">void</span> <span class="special">*</span> <span class="identifier">vp</span><span class="special">)</span> <span class="special">{</span>
 277                     <span class="keyword">try</span> <span class="special">{</span>
 278                         <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="special">*</span> <span class="keyword">static_cast</span><span class="special">&lt;</span> <span class="keyword">int</span> <span class="special">*</span> <span class="special">&gt;(</span> <span class="identifier">vp</span><span class="special">);</span>
 279                         <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lexical_cast</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">i</span><span class="special">);</span>
 280                         <span class="identifier">caller_</span><span class="special">(</span> <span class="special">&amp;</span> <span class="identifier">str</span><span class="special">);</span>
 281                     <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(...)</span> <span class="special">{</span>
 282                         <span class="identifier">excptr_</span><span class="special">=</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">current_exception</span><span class="special">();</span>
 283                     <span class="special">}</span>
 284                  <span class="special">})</span>
 285     <span class="special">{}</span>
 286
 287     <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">int</span> <span class="identifier">i</span><span class="special">)</span> <span class="special">{</span>
 288         <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">ret</span> <span class="special">=</span> <span class="identifier">callee_</span><span class="special">(</span> <span class="special">&amp;</span> <span class="identifier">i</span><span class="special">);</span>
 289         <span class="keyword">if</span><span class="special">(</span><span class="identifier">excptr_</span><span class="special">){</span>
 290             <span class="identifier">std</span><span class="special">::</span><span class="identifier">rethrow_exception</span><span class="special">(</span><span class="identifier">excptr_</span><span class="special">);</span>
 291         <span class="special">}</span>
 292         <span class="keyword">return</span> <span class="special">*</span> <span class="keyword">static_cast</span><span class="special">&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">*</span> <span class="special">&gt;(</span> <span class="identifier">ret</span><span class="special">);</span>
 293     <span class="special">}</span>
 294 <span class="special">};</span>
 295
 296 <span class="identifier">X</span> <span class="identifier">x</span><span class="special">;</span>
 297 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">x</span><span class="special">(</span> <span class="number">7</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 298
 299 <span class="identifier">output</span><span class="special">:</span>
 300     <span class="number">7</span>
 301 </pre>
 302 <h4>
 303 <a name="context.ecv1_class.h5"></a>
 304       <span><a name="context.ecv1_class.class__code__phrase_role__identifier__execution_context__phrase___code_"></a></span><a class="link" href="ecv1_class.html#context.ecv1_class.class__code__phrase_role__identifier__execution_context__phrase___code_">Class
 305       <code class="computeroutput"><span class="identifier">execution_context</span></code></a>
 306     </h4>
 307 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">execution_context</span> <span class="special">{</span>
 308 <span class="keyword">public</span><span class="special">:</span>
 309     <span class="keyword">static</span> <span class="identifier">execution_context</span> <span class="identifier">current</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span>
 310
 311     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 312     <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 313
 314     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 315     <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 316
 317     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 318     <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">preallocated</span> <span class="identifier">palloc</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 319
 320     <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 321     <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">execution_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 322
 323     <span class="identifier">execution_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 324     <span class="identifier">execution_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">execution_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 325
 326     <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 327     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 328
 329     <span class="keyword">void</span> <span class="special">*</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">vp</span> <span class="special">=</span> <span class="keyword">nullptr</span><span class="special">);</span>
 330
 331     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 332     <span class="keyword">void</span> <span class="special">*</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 333
 334     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 335     <span class="keyword">void</span> <span class="special">*</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">vp</span><span class="special">,</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 336
 337     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 338
 339     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 340
 341     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 342
 343     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 344
 345     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 346
 347     <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 348
 349     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">charT</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span>
 350     <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span>
 351     <span class="keyword">operator</span><span class="special">&lt;&lt;(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">);</span>
 352 <span class="special">};</span>
 353 </pre>
 354 <p>
 355       </p>
 356 <h5>
 357 <a name="ecv1_current_bridgehead"></a>
 358   <span><a name="ecv1_current"></a></span>
 359   <a class="link" href="ecv1_class.html#ecv1_current">Static member function <code class="computeroutput">current</code>()</a>
 360 </h5>
 361 <p>
 362     </p>
 363 <pre class="programlisting"><span class="keyword">static</span> <span class="identifier">execution_context</span> <span class="identifier">current</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span>
 364 </pre>
 365 <div class="variablelist">
 366 <p class="title"><b></b></p>
 367 <dl>
 368 <dt><span class="term">Returns:</span></dt>
 369 <dd><p>
 370             Returns an instance of excution_context pointing to the active execution
 371             context.
 372           </p></dd>
 373 <dt><span class="term">Throws:</span></dt>
 374 <dd><p>
 375             Nothing.
 376           </p></dd>
 377 </dl>
 378 </div>
 379 <p>
 380       </p>
 381 <h5>
 382 <a name="ecv1_constructor_bridgehead"></a>
 383   <span><a name="ecv1_constructor"></a></span>
 384   <a class="link" href="ecv1_class.html#ecv1_constructor">Constructor</a>
 385 </h5>
 386 <p>
 387     </p>
 388 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 389 <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 390
 391 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 392 <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 393
 394 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">StackAlloc</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 395 <span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator_arg_t</span><span class="special">,</span> <span class="identifier">preallocated</span> <span class="identifier">palloc</span><span class="special">,</span> <span class="identifier">StackAlloc</span> <span class="identifier">salloc</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 396 </pre>
 397 <div class="variablelist">
 398 <p class="title"><b></b></p>
 399 <dl>
 400 <dt><span class="term">Effects:</span></dt>
 401 <dd><p>
 402             Creates a new execution context and prepares the context to execute
 403             <code class="computeroutput"><span class="identifier">fn</span></code>. <code class="computeroutput"><span class="identifier">fixedsize_stack</span></code>
 404             is used as default stack allocator (stack size == fixedsize_stack::traits::default_size()).
 405             The constructor with argument type <code class="computeroutput"><span class="identifier">preallocated</span></code>,
 406             is used to create a user defined data <a class="link" href="../">(for
 407             instance additional control structures)</a> on top of the stack.
 408           </p></dd>
 409 </dl>
 410 </div>
 411 <p>
 412       </p>
 413 <h5>
 414 <a name="ecv1_copy%20constructor_bridgehead"></a>
 415   <span><a name="ecv1_copy%20constructor"></a></span>
 416   <a class="link" href="ecv1_class.html#ecv1_copy%20constructor">Copy
 417       constructor</a>
 418 </h5>
 419 <p>
 420     </p>
 421 <pre class="programlisting"><span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 422 </pre>
 423 <div class="variablelist">
 424 <p class="title"><b></b></p>
 425 <dl>
 426 <dt><span class="term">Effects:</span></dt>
 427 <dd><p>
 428             Copies <code class="computeroutput"><span class="identifier">other</span></code>, e.g. underlying
 429             control structure is shared with <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
 430           </p></dd>
 431 <dt><span class="term">Throws:</span></dt>
 432 <dd><p>
 433             Nothing.
 434           </p></dd>
 435 </dl>
 436 </div>
 437 <p>
 438       </p>
 439 <h5>
 440 <a name="ecv1_move%20constructor_bridgehead"></a>
 441   <span><a name="ecv1_move%20constructor"></a></span>
 442   <a class="link" href="ecv1_class.html#ecv1_move%20constructor">Move
 443       constructor</a>
 444 </h5>
 445 <p>
 446     </p>
 447 <pre class="programlisting"><span class="identifier">execution_context</span><span class="special">(</span> <span class="identifier">execution_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 448 </pre>
 449 <div class="variablelist">
 450 <p class="title"><b></b></p>
 451 <dl>
 452 <dt><span class="term">Effects:</span></dt>
 453 <dd><p>
 454             Moves underlying control structure to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
 455           </p></dd>
 456 <dt><span class="term">Throws:</span></dt>
 457 <dd><p>
 458             Nothing.
 459           </p></dd>
 460 </dl>
 461 </div>
 462 <p>
 463       </p>
 464 <h5>
 465 <a name="ecv1_copy%20assignment_bridgehead"></a>
 466   <span><a name="ecv1_copy%20assignment"></a></span>
 467   <a class="link" href="ecv1_class.html#ecv1_copy%20assignment">Copy
 468       assignment operator</a>
 469 </h5>
 470 <p>
 471     </p>
 472 <pre class="programlisting"><span class="identifier">execution_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 473 </pre>
 474 <div class="variablelist">
 475 <p class="title"><b></b></p>
 476 <dl>
 477 <dt><span class="term">Effects:</span></dt>
 478 <dd><p>
 479             Copies the state of <code class="computeroutput"><span class="identifier">other</span></code>
 480             to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>,
 481             control structure is shared.
 482           </p></dd>
 483 <dt><span class="term">Throws:</span></dt>
 484 <dd><p>
 485             Nothing.
 486           </p></dd>
 487 </dl>
 488 </div>
 489 <p>
 490       </p>
 491 <h5>
 492 <a name="ecv1_move%20assignment_bridgehead"></a>
 493   <span><a name="ecv1_move%20assignment"></a></span>
 494   <a class="link" href="ecv1_class.html#ecv1_move%20assignment">Move
 495       assignment operator</a>
 496 </h5>
 497 <p>
 498     </p>
 499 <pre class="programlisting"><span class="identifier">execution_context</span> <span class="special">&amp;</span> <span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">execution_context</span> <span class="special">&amp;&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 500 </pre>
 501 <div class="variablelist">
 502 <p class="title"><b></b></p>
 503 <dl>
 504 <dt><span class="term">Effects:</span></dt>
 505 <dd><p>
 506             Moves the control structure of <code class="computeroutput"><span class="identifier">other</span></code>
 507             to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 508             using move semantics.
 509           </p></dd>
 510 <dt><span class="term">Throws:</span></dt>
 511 <dd><p>
 512             Nothing.
 513           </p></dd>
 514 </dl>
 515 </div>
 516 <p>
 517       </p>
 518 <h5>
 519 <a name="ecv1_operator_bool_bridgehead"></a>
 520   <span><a name="ecv1_operator_bool"></a></span>
 521   <a class="link" href="ecv1_class.html#ecv1_operator_bool">Member function
 522       <code class="computeroutput">operator bool</code>()</a>
 523 </h5>
 524 <p>
 525     </p>
 526 <pre class="programlisting"><span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 527 </pre>
 528 <div class="variablelist">
 529 <p class="title"><b></b></p>
 530 <dl>
 531 <dt><span class="term">Returns:</span></dt>
 532 <dd><p>
 533             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> points to a control structure.
 534           </p></dd>
 535 <dt><span class="term">Throws:</span></dt>
 536 <dd><p>
 537             Nothing.
 538           </p></dd>
 539 </dl>
 540 </div>
 541 <p>
 542       </p>
 543 <h5>
 544 <a name="ecv1_operator_not_bridgehead"></a>
 545   <span><a name="ecv1_operator_not"></a></span>
 546   <a class="link" href="ecv1_class.html#ecv1_operator_not">Member function
 547       <code class="computeroutput">operator!</code>()</a>
 548 </h5>
 549 <p>
 550     </p>
 551 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 552 </pre>
 553 <div class="variablelist">
 554 <p class="title"><b></b></p>
 555 <dl>
 556 <dt><span class="term">Returns:</span></dt>
 557 <dd><p>
 558             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not point to a control structure.
 559           </p></dd>
 560 <dt><span class="term">Throws:</span></dt>
 561 <dd><p>
 562             Nothing.
 563           </p></dd>
 564 </dl>
 565 </div>
 566 <p>
 567       </p>
 568 <h5>
 569 <a name="ecv1_operator_call_bridgehead"></a>
 570   <span><a name="ecv1_operator_call"></a></span>
 571   <a class="link" href="ecv1_class.html#ecv1_operator_call">Member function
 572       <code class="computeroutput">operator()</code>()</a>
 573 </h5>
 574 <p>
 575     </p>
 576 <pre class="programlisting"><span class="keyword">void</span> <span class="special">*</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">vp</span> <span class="special">=</span> <span class="keyword">nullptr</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
 577 </pre>
 578 <div class="variablelist">
 579 <p class="title"><b></b></p>
 580 <dl>
 581 <dt><span class="term">Effects:</span></dt>
 582 <dd><p>
 583             Stores internally the current context data (stack pointer, instruction
 584             pointer, and CPU registers) of the current active context and restores
 585             the context data from <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, which implies jumping to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>'s
 586             context. The void pointer argument, <code class="computeroutput"><span class="identifier">vp</span></code>,
 587             is passed to the current context to be returned by the most recent call
 588             to <code class="computeroutput"><span class="identifier">execution_context</span><span class="special">::</span><span class="keyword">operator</span><span class="special">()</span></code> in the same thread. <code class="computeroutput"><span class="identifier">fn</span></code>
 589             is executed with arguments <code class="computeroutput"><span class="identifier">args</span></code>
 590             on top of the stack of <code class="computeroutput"><span class="keyword">this</span></code>.
 591           </p></dd>
 592 <dt><span class="term">Note:</span></dt>
 593 <dd><p>
 594             The behaviour is undefined if <code class="computeroutput"><span class="keyword">operator</span><span class="special">()()</span></code> is called while <span class="emphasis"><em>execution_context::current()</em></span>
 595             returns <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 596             (e.g. resuming an already running context). If the top-level context
 597             function returns, <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">exit</span><span class="special">()</span></code> is called.
 598           </p></dd>
 599 <dt><span class="term">Returns:</span></dt>
 600 <dd><p>
 601             The void pointer argument passed to the most recent call to <span class="emphasis"><em>execution_context::operator()</em></span>,
 602             if any.
 603           </p></dd>
 604 </dl>
 605 </div>
 606 <p>
 607       </p>
 608 <h5>
 609 <a name="ecv1_operator_call_ontop_bridgehead"></a>
 610   <span><a name="ecv1_operator_call_ontop"></a></span>
 611   <a class="link" href="ecv1_class.html#ecv1_operator_call_ontop">Member
 612       function <code class="computeroutput">operator(exec_ontop_arg_t)</code>()</a>
 613 </h5>
 614 <p>
 615     </p>
 616 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 617 <span class="keyword">void</span> <span class="special">*</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 618
 619 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span><span class="special">,</span> <span class="keyword">typename</span> <span class="special">...</span> <span class="identifier">Args</span> <span class="special">&gt;</span>
 620 <span class="keyword">void</span> <span class="special">*</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">void</span> <span class="special">*</span> <span class="identifier">data</span><span class="special">,</span> <span class="identifier">exec_ontop_arg_t</span><span class="special">,</span> <span class="identifier">Fn</span> <span class="special">&amp;&amp;</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span> <span class="special">...</span> <span class="identifier">args</span><span class="special">);</span>
 621 </pre>
 622 <div class="variablelist">
 623 <p class="title"><b></b></p>
 624 <dl>
 625 <dt><span class="term">Effects:</span></dt>
 626 <dd><p>
 627             Same as <span class="emphasis"><em>execution_context::operator()</em></span>. Additionally,
 628             function <code class="computeroutput"><span class="identifier">fn</span></code> is executed
 629             with arguments <code class="computeroutput"><span class="identifier">args</span></code> in
 630             the context of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 631             (e.g. the stack frame of <code class="computeroutput"><span class="identifier">fn</span></code>
 632             is allocated on stack of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>).
 633           </p></dd>
 634 <dt><span class="term">Returns:</span></dt>
 635 <dd><p>
 636             The void pointer argument passed to the most recent call to <span class="emphasis"><em>execution_context::operator()</em></span>,
 637             if any.
 638           </p></dd>
 639 </dl>
 640 </div>
 641 <p>
 642       </p>
 643 <h5>
 644 <a name="ecv1_operator_equal_bridgehead"></a>
 645   <span><a name="ecv1_operator_equal"></a></span>
 646   <a class="link" href="ecv1_class.html#ecv1_operator_equal">Member
 647       function <code class="computeroutput">operator==</code>()</a>
 648 </h5>
 649 <p>
 650     </p>
 651 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 652 </pre>
 653 <div class="variablelist">
 654 <p class="title"><b></b></p>
 655 <dl>
 656 <dt><span class="term">Returns:</span></dt>
 657 <dd><p>
 658             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">other</span></code>
 659             represent the same execution context, <code class="computeroutput"><span class="keyword">false</span></code>
 660             otherwise.
 661           </p></dd>
 662 <dt><span class="term">Throws:</span></dt>
 663 <dd><p>
 664             Nothing.
 665           </p></dd>
 666 </dl>
 667 </div>
 668 <p>
 669       </p>
 670 <h5>
 671 <a name="ecv1_operator_notequal_bridgehead"></a>
 672   <span><a name="ecv1_operator_notequal"></a></span>
 673   <a class="link" href="ecv1_class.html#ecv1_operator_notequal">Member
 674       function <code class="computeroutput">operator!=</code>()</a>
 675 </h5>
 676 <p>
 677     </p>
 678 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 679 </pre>
 680 <div class="variablelist">
 681 <p class="title"><b></b></p>
 682 <dl>
 683 <dt><span class="term">Returns:</span></dt>
 684 <dd><p>
 685             <code class="computeroutput">! (other == * this)</code>
 686           </p></dd>
 687 <dt><span class="term">Throws:</span></dt>
 688 <dd><p>
 689             Nothing.
 690           </p></dd>
 691 </dl>
 692 </div>
 693 <p>
 694       </p>
 695 <h5>
 696 <a name="ecv1_operator_less_bridgehead"></a>
 697   <span><a name="ecv1_operator_less"></a></span>
 698   <a class="link" href="ecv1_class.html#ecv1_operator_less">Member function
 699       <code class="computeroutput">operator&lt;</code>()</a>
 700 </h5>
 701 <p>
 702     </p>
 703 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 704 </pre>
 705 <div class="variablelist">
 706 <p class="title"><b></b></p>
 707 <dl>
 708 <dt><span class="term">Returns:</span></dt>
 709 <dd><p>
 710             <code class="computeroutput"><span class="keyword">true</span></code> if <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">!=</span> <span class="identifier">other</span></code> is true and the implementation-defined
 711             total order of <code class="computeroutput"><span class="identifier">execution_context</span></code>
 712             values places <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 713             before <code class="computeroutput"><span class="identifier">other</span></code>, false otherwise.
 714           </p></dd>
 715 <dt><span class="term">Throws:</span></dt>
 716 <dd><p>
 717             Nothing.
 718           </p></dd>
 719 </dl>
 720 </div>
 721 <p>
 722       </p>
 723 <h5>
 724 <a name="ecv1_operator_greater_bridgehead"></a>
 725   <span><a name="ecv1_operator_greater"></a></span>
 726   <a class="link" href="ecv1_class.html#ecv1_operator_greater">Member
 727       function <code class="computeroutput">operator&gt;</code>()</a>
 728 </h5>
 729 <p>
 730     </p>
 731 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 732 </pre>
 733 <div class="variablelist">
 734 <p class="title"><b></b></p>
 735 <dl>
 736 <dt><span class="term">Returns:</span></dt>
 737 <dd><p>
 738             <code class="computeroutput"><span class="identifier">other</span> <span class="special">&lt;</span>
 739             <span class="special">*</span> <span class="keyword">this</span></code>
 740           </p></dd>
 741 <dt><span class="term">Throws:</span></dt>
 742 <dd><p>
 743             Nothing.
 744           </p></dd>
 745 </dl>
 746 </div>
 747 <p>
 748       </p>
 749 <h5>
 750 <a name="ecv1_operator_lesseq_bridgehead"></a>
 751   <span><a name="ecv1_operator_lesseq"></a></span>
 752   <a class="link" href="ecv1_class.html#ecv1_operator_lesseq">Member
 753       function <code class="computeroutput">operator&lt;=</code>()</a>
 754 </h5>
 755 <p>
 756     </p>
 757 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&lt;=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 758 </pre>
 759 <div class="variablelist">
 760 <p class="title"><b></b></p>
 761 <dl>
 762 <dt><span class="term">Returns:</span></dt>
 763 <dd><p>
 764             <code class="computeroutput"><span class="special">!</span> <span class="special">(</span><span class="identifier">other</span> <span class="special">&lt;</span>
 765             <span class="special">*</span> <span class="keyword">this</span><span class="special">)</span></code>
 766           </p></dd>
 767 <dt><span class="term">Throws:</span></dt>
 768 <dd><p>
 769             Nothing.
 770           </p></dd>
 771 </dl>
 772 </div>
 773 <p>
 774       </p>
 775 <h5>
 776 <a name="ecv1_operator_greatereq_bridgehead"></a>
 777   <span><a name="ecv1_operator_greatereq"></a></span>
 778   <a class="link" href="ecv1_class.html#ecv1_operator_greatereq">Member
 779       function <code class="computeroutput">operator&gt;=</code>()</a>
 780 </h5>
 781 <p>
 782     </p>
 783 <pre class="programlisting"><span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">&gt;=(</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
 784 </pre>
 785 <div class="variablelist">
 786 <p class="title"><b></b></p>
 787 <dl>
 788 <dt><span class="term">Returns:</span></dt>
 789 <dd><p>
 790             <code class="computeroutput"><span class="special">!</span> <span class="special">(*</span>
 791             <span class="keyword">this</span> <span class="special">&lt;</span>
 792             <span class="identifier">other</span><span class="special">)</span></code>
 793           </p></dd>
 794 <dt><span class="term">Throws:</span></dt>
 795 <dd><p>
 796             Nothing.
 797           </p></dd>
 798 </dl>
 799 </div>
 800 <p>
 801       </p>
 802 <h5>
 803 <a name="ecv1_bridgehead"></a>
 804   <span><a name="ecv1"></a></span>
 805   <a class="link" href="ecv1_class.html#ecv1">Non-member function <code class="computeroutput">operator&lt;&lt;()</code></a>
 806 </h5>
 807 <p>
 808     </p>
 809 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">charT</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span>
 810 <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span>
 811 <span class="keyword">operator</span><span class="special">&lt;&lt;(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special">&lt;</span> <span class="identifier">charT</span><span class="special">,</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">execution_context</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">other</span><span class="special">);</span>
 812 </pre>
 813 <div class="variablelist">
 814 <p class="title"><b></b></p>
 815 <dl>
 816 <dt><span class="term">Efects:</span></dt>
 817 <dd><p>
 818             Writes the representation of <code class="computeroutput"><span class="identifier">other</span></code>
 819             to stream <code class="computeroutput"><span class="identifier">os</span></code>.
 820           </p></dd>
 821 <dt><span class="term">Returns:</span></dt>
 822 <dd><p>
 823             <code class="computeroutput"><span class="identifier">os</span></code>
 824           </p></dd>
 825 </dl>
 826 </div>
 827 </div>
 828 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 829 <td align="left"></td>
 830 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Oliver Kowalke<p>
 831         Distributed under the Boost Software License, Version 1.0. (See accompanying
 832         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>)
 833       </p>
 834 </div></td>
 835 </tr></table>
 836 <hr>
 837 <div class="spirit-nav">
 838 <a accesskey="p" href="requirements.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="ecv2_class.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
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