ceph/src/boost/libs/context/doc/html/context/ecv1.html

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  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="context.ecv1"></a><a name="ecv1"></a><a class="link" href="ecv1.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 only enabled if property <span class="emphasis"><em>segmented-stacks=on</em></span>
  37         (enables segmented stacks) or compiler flag <span class="emphasis"><em>BOOST_EXECUTION_CONTEXT=1</em></span>
  38         is specified at 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="ecv1.html#ecv1_operator_call"> <code class="computeroutput">ecv1::operator()()</code></a>).
  73     </p>
  74 <h4>
  75 <a name="context.ecv1.h0"></a>
  76       <span><a name="context.ecv1.usage_of__emphasis_execution_context__emphasis_"></a></span><a class="link" href="ecv1.html#context.ecv1.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.h1"></a>
 117       <span><a name="context.ecv1.inverting_the_control_flow"></a></span><a class="link" href="ecv1.html#context.ecv1.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.h2"></a>
 199       <span><a name="context.ecv1.allocating_control_structures_on_top_of_stack"></a></span><a class="link" href="ecv1.html#context.ecv1.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.h3"></a>
 244       <span><a name="context.ecv1.exception_handling"></a></span><a class="link" href="ecv1.html#context.ecv1.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 <div class="important"><table border="0" summary="Important">
 254 <tr>
 255 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../doc/src/images/important.png"></td>
 256 <th align="left">Important</th>
 257 </tr>
 258 <tr><td align="left" valign="top"><p>
 259         Do not jump from inside a catch block and then re-throw the exception in
 260         another execution context.
 261       </p></td></tr>
 262 </table></div>
 263 <h4>
 264 <a name="context.ecv1.h4"></a>
 265       <span><a name="context.ecv1.parameter_passing"></a></span><a class="link" href="ecv1.html#context.ecv1.parameter_passing">parameter
 266       passing</a>
 267     </h4>
 268 <p>
 269       The void pointer argument passed to <span class="emphasis"><em>execution_context::operator()</em></span>,
 270       in one context, is passed as the last argument of the <span class="emphasis"><em>context-function</em></span>
 271       if the context is started for the first time. In all following invocations
 272       of <span class="emphasis"><em>execution_context::operator()</em></span> the void pointer passed
 273       to <span class="emphasis"><em>execution_context::operator()</em></span>, in one context, is returned
 274       by <span class="emphasis"><em>execution_context::operator()</em></span> in the other context.
 275     </p>
 276 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">X</span> <span class="special">{</span>
 277 <span class="keyword">private</span><span class="special">:</span>
 278     <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception_ptr</span> <span class="identifier">excptr_</span><span class="special">;</span>
 279     <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>
 280     <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>
 281
 282 <span class="keyword">public</span><span class="special">:</span>
 283     <span class="identifier">X</span><span class="special">()</span> <span class="special">:</span>
 284         <span class="identifier">excptr_</span><span class="special">(),</span>
 285         <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>
 286         <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>
 287                     <span class="keyword">try</span> <span class="special">{</span>
 288                         <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>
 289                         <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>
 290                         <span class="identifier">caller_</span><span class="special">(</span> <span class="special">&amp;</span> <span class="identifier">str</span><span class="special">);</span>
 291                     <span class="special">}</span> <span class="keyword">catch</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">bad_cast</span> <span class="keyword">const</span><span class="special">&amp;)</span> <span class="special">{</span>
 292                         <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>
 293                     <span class="special">}</span>
 294                  <span class="special">})</span>
 295     <span class="special">{}</span>
 296
 297     <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>
 298         <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>
 299         <span class="keyword">if</span><span class="special">(</span><span class="identifier">excptr_</span><span class="special">){</span>
 300             <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>
 301         <span class="special">}</span>
 302         <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>
 303     <span class="special">}</span>
 304 <span class="special">};</span>
 305
 306 <span class="identifier">X</span> <span class="identifier">x</span><span class="special">;</span>
 307 <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>
 308
 309 <span class="identifier">output</span><span class="special">:</span>
 310     <span class="number">7</span>
 311 </pre>
 312 <h4>
 313 <a name="context.ecv1.h5"></a>
 314       <span><a name="context.ecv1.class__code__phrase_role__identifier__execution_context__phrase___code_"></a></span><a class="link" href="ecv1.html#context.ecv1.class__code__phrase_role__identifier__execution_context__phrase___code_">Class
 315       <code class="computeroutput"><span class="identifier">execution_context</span></code></a>
 316     </h4>
 317 <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">execution_context</span> <span class="special">{</span>
 318 <span class="keyword">public</span><span class="special">:</span>
 319     <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>
 320
 321     <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>
 322     <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>
 323
 324     <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>
 325     <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>
 326
 327     <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>
 328     <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>
 329
 330     <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>
 331     <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>
 332
 333     <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>
 334     <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>
 335
 336     <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>
 337     <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>
 338
 339     <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>
 340
 341     <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Fn</span> <span class="special">&gt;</span>
 342     <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="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>
 343
 344     <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>
 345
 346     <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>
 347
 348     <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>
 349
 350     <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>
 351
 352     <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>
 353
 354     <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>
 355
 356     <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>
 357     <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>
 358     <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>
 359 <span class="special">};</span>
 360 </pre>
 361 <p>
 362       </p>
 363 <h5>
 364 <a name="ecv1_current_bridgehead"></a>
 365   <span><a name="ecv1_current"></a></span>
 366   <a class="link" href="ecv1.html#ecv1_current">Static member function <code class="computeroutput">current</code>()</a>
 367 </h5>
 368 <p>
 369     </p>
 370 <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>
 371 </pre>
 372 <div class="variablelist">
 373 <p class="title"><b></b></p>
 374 <dl>
 375 <dt><span class="term">Returns:</span></dt>
 376 <dd><p>
 377             Returns an instance of excution_context pointing to the active execution
 378             context.
 379           </p></dd>
 380 <dt><span class="term">Throws:</span></dt>
 381 <dd><p>
 382             Nothing.
 383           </p></dd>
 384 </dl>
 385 </div>
 386 <p>
 387       </p>
 388 <h5>
 389 <a name="ecv1_constructor_bridgehead"></a>
 390   <span><a name="ecv1_constructor"></a></span>
 391   <a class="link" href="ecv1.html#ecv1_constructor">Constructor</a>
 392 </h5>
 393 <p>
 394     </p>
 395 <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>
 396 <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>
 397
 398 <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>
 399 <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>
 400
 401 <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>
 402 <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>
 403 </pre>
 404 <div class="variablelist">
 405 <p class="title"><b></b></p>
 406 <dl>
 407 <dt><span class="term">Effects:</span></dt>
 408 <dd><p>
 409             Creates a new execution context and prepares the context to execute
 410             <code class="computeroutput"><span class="identifier">fn</span></code>. <code class="computeroutput"><span class="identifier">fixedsize_stack</span></code>
 411             is used as default stack allocator (stack size == fixedsize_stack::traits::default_size()).
 412             The constructor with argument type <code class="computeroutput"><span class="identifier">preallocated</span></code>,
 413             is used to create a user defined data <a class="link" href="ecv1.html#ecv1_prealloc">(for
 414             instance additional control structures)</a> on top of the stack.
 415           </p></dd>
 416 </dl>
 417 </div>
 418 <p>
 419       </p>
 420 <h5>
 421 <a name="ecv1_copy%20constructor_bridgehead"></a>
 422   <span><a name="ecv1_copy%20constructor"></a></span>
 423   <a class="link" href="ecv1.html#ecv1_copy%20constructor">Copy
 424       constructor</a>
 425 </h5>
 426 <p>
 427     </p>
 428 <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>
 429 </pre>
 430 <div class="variablelist">
 431 <p class="title"><b></b></p>
 432 <dl>
 433 <dt><span class="term">Effects:</span></dt>
 434 <dd><p>
 435             Copies <code class="computeroutput"><span class="identifier">other</span></code>, e.g. underlying
 436             control structure is shared with <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
 437           </p></dd>
 438 <dt><span class="term">Throws:</span></dt>
 439 <dd><p>
 440             Nothing.
 441           </p></dd>
 442 </dl>
 443 </div>
 444 <p>
 445       </p>
 446 <h5>
 447 <a name="ecv1_move%20constructor_bridgehead"></a>
 448   <span><a name="ecv1_move%20constructor"></a></span>
 449   <a class="link" href="ecv1.html#ecv1_move%20constructor">Move
 450       constructor</a>
 451 </h5>
 452 <p>
 453     </p>
 454 <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>
 455 </pre>
 456 <div class="variablelist">
 457 <p class="title"><b></b></p>
 458 <dl>
 459 <dt><span class="term">Effects:</span></dt>
 460 <dd><p>
 461             Moves underlying control structure to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
 462           </p></dd>
 463 <dt><span class="term">Throws:</span></dt>
 464 <dd><p>
 465             Nothing.
 466           </p></dd>
 467 </dl>
 468 </div>
 469 <p>
 470       </p>
 471 <h5>
 472 <a name="ecv1_copy%20assignment_bridgehead"></a>
 473   <span><a name="ecv1_copy%20assignment"></a></span>
 474   <a class="link" href="ecv1.html#ecv1_copy%20assignment">Copy
 475       assignment operator</a>
 476 </h5>
 477 <p>
 478     </p>
 479 <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>
 480 </pre>
 481 <div class="variablelist">
 482 <p class="title"><b></b></p>
 483 <dl>
 484 <dt><span class="term">Effects:</span></dt>
 485 <dd><p>
 486             Copies the state of <code class="computeroutput"><span class="identifier">other</span></code>
 487             to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>,
 488             control structure is shared.
 489           </p></dd>
 490 <dt><span class="term">Throws:</span></dt>
 491 <dd><p>
 492             Nothing.
 493           </p></dd>
 494 </dl>
 495 </div>
 496 <p>
 497       </p>
 498 <h5>
 499 <a name="ecv1_move%20assignment_bridgehead"></a>
 500   <span><a name="ecv1_move%20assignment"></a></span>
 501   <a class="link" href="ecv1.html#ecv1_move%20assignment">Move
 502       assignment operator</a>
 503 </h5>
 504 <p>
 505     </p>
 506 <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>
 507 </pre>
 508 <div class="variablelist">
 509 <p class="title"><b></b></p>
 510 <dl>
 511 <dt><span class="term">Effects:</span></dt>
 512 <dd><p>
 513             Moves the control structure of <code class="computeroutput"><span class="identifier">other</span></code>
 514             to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 515             using move semantics.
 516           </p></dd>
 517 <dt><span class="term">Throws:</span></dt>
 518 <dd><p>
 519             Nothing.
 520           </p></dd>
 521 </dl>
 522 </div>
 523 <p>
 524       </p>
 525 <h5>
 526 <a name="ecv1_operator_bool_bridgehead"></a>
 527   <span><a name="ecv1_operator_bool"></a></span>
 528   <a class="link" href="ecv1.html#ecv1_operator_bool">Member function
 529       <code class="computeroutput">operator bool</code>()</a>
 530 </h5>
 531 <p>
 532     </p>
 533 <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>
 534 </pre>
 535 <div class="variablelist">
 536 <p class="title"><b></b></p>
 537 <dl>
 538 <dt><span class="term">Returns:</span></dt>
 539 <dd><p>
 540             <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.
 541           </p></dd>
 542 <dt><span class="term">Throws:</span></dt>
 543 <dd><p>
 544             Nothing.
 545           </p></dd>
 546 </dl>
 547 </div>
 548 <p>
 549       </p>
 550 <h5>
 551 <a name="ecv1_operator_not_bridgehead"></a>
 552   <span><a name="ecv1_operator_not"></a></span>
 553   <a class="link" href="ecv1.html#ecv1_operator_not">Member function
 554       <code class="computeroutput">operator!</code>()</a>
 555 </h5>
 556 <p>
 557     </p>
 558 <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>
 559 </pre>
 560 <div class="variablelist">
 561 <p class="title"><b></b></p>
 562 <dl>
 563 <dt><span class="term">Returns:</span></dt>
 564 <dd><p>
 565             <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.
 566           </p></dd>
 567 <dt><span class="term">Throws:</span></dt>
 568 <dd><p>
 569             Nothing.
 570           </p></dd>
 571 </dl>
 572 </div>
 573 <p>
 574       </p>
 575 <h5>
 576 <a name="ecv1_operator_call_bridgehead"></a>
 577   <span><a name="ecv1_operator_call"></a></span>
 578   <a class="link" href="ecv1.html#ecv1_operator_call">Member function
 579       <code class="computeroutput">operator()</code>()</a>
 580 </h5>
 581 <p>
 582     </p>
 583 <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>
 584 </pre>
 585 <div class="variablelist">
 586 <p class="title"><b></b></p>
 587 <dl>
 588 <dt><span class="term">Effects:</span></dt>
 589 <dd><p>
 590             Stores internally the current context data (stack pointer, instruction
 591             pointer, and CPU registers) of the current active context and restores
 592             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
 593             context. The void pointer argument, <code class="computeroutput"><span class="identifier">vp</span></code>,
 594             is passed to the current context to be returned by the most recent call
 595             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>
 596             is executed with arguments <code class="computeroutput"><span class="identifier">args</span></code>
 597             on top of the stack of <code class="computeroutput"><span class="keyword">this</span></code>.
 598           </p></dd>
 599 <dt><span class="term">Note:</span></dt>
 600 <dd><p>
 601             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>
 602             returns <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 603             (e.g. resuming an already running context). If the top-level context
 604             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.
 605           </p></dd>
 606 <dt><span class="term">Returns:</span></dt>
 607 <dd><p>
 608             The void pointer argument passed to the most recent call to <span class="emphasis"><em>execution_context::operator()</em></span>,
 609             if any.
 610           </p></dd>
 611 </dl>
 612 </div>
 613 <p>
 614       </p>
 615 <h5>
 616 <a name="ecv1_operator_call_ontop_bridgehead"></a>
 617   <span><a name="ecv1_operator_call_ontop"></a></span>
 618   <a class="link" href="ecv1.html#ecv1_operator_call_ontop">Member
 619       function <code class="computeroutput">operator(exec_ontop_arg_t)</code>()</a>
 620 </h5>
 621 <p>
 622     </p>
 623 <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">&gt;</span>
 624 <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="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>
 625 </pre>
 626 <div class="variablelist">
 627 <p class="title"><b></b></p>
 628 <dl>
 629 <dt><span class="term">Effects:</span></dt>
 630 <dd><p>
 631             Same as <span class="emphasis"><em>execution_context::operator()</em></span>. Additionally,
 632             function <code class="computeroutput"><span class="identifier">fn</span></code> is executed
 633             with arguments <code class="computeroutput"><span class="identifier">vp</span></code> in
 634             the context of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 635             (e.g. the stack frame of <code class="computeroutput"><span class="identifier">fn</span></code>
 636             is allocated on stack of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>).
 637           </p></dd>
 638 <dt><span class="term">Returns:</span></dt>
 639 <dd><p>
 640             The void pointer argument passed to the most recent call to <span class="emphasis"><em>execution_context::operator()</em></span>,
 641             if any.
 642           </p></dd>
 643 </dl>
 644 </div>
 645 <p>
 646       </p>
 647 <h5>
 648 <a name="ecv1_operator_equal_bridgehead"></a>
 649   <span><a name="ecv1_operator_equal"></a></span>
 650   <a class="link" href="ecv1.html#ecv1_operator_equal">Member
 651       function <code class="computeroutput">operator==</code>()</a>
 652 </h5>
 653 <p>
 654     </p>
 655 <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>
 656 </pre>
 657 <div class="variablelist">
 658 <p class="title"><b></b></p>
 659 <dl>
 660 <dt><span class="term">Returns:</span></dt>
 661 <dd><p>
 662             <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>
 663             represent the same execution context, <code class="computeroutput"><span class="keyword">false</span></code>
 664             otherwise.
 665           </p></dd>
 666 <dt><span class="term">Throws:</span></dt>
 667 <dd><p>
 668             Nothing.
 669           </p></dd>
 670 </dl>
 671 </div>
 672 <p>
 673       </p>
 674 <h5>
 675 <a name="ecv1_operator_notequal_bridgehead"></a>
 676   <span><a name="ecv1_operator_notequal"></a></span>
 677   <a class="link" href="ecv1.html#ecv1_operator_notequal">Member
 678       function <code class="computeroutput">operator!=</code>()</a>
 679 </h5>
 680 <p>
 681     </p>
 682 <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>
 683 </pre>
 684 <div class="variablelist">
 685 <p class="title"><b></b></p>
 686 <dl>
 687 <dt><span class="term">Returns:</span></dt>
 688 <dd><p>
 689             <code class="computeroutput">! (other == * this)</code>
 690           </p></dd>
 691 <dt><span class="term">Throws:</span></dt>
 692 <dd><p>
 693             Nothing.
 694           </p></dd>
 695 </dl>
 696 </div>
 697 <p>
 698       </p>
 699 <h5>
 700 <a name="ecv1_operator_less_bridgehead"></a>
 701   <span><a name="ecv1_operator_less"></a></span>
 702   <a class="link" href="ecv1.html#ecv1_operator_less">Member function
 703       <code class="computeroutput">operator&lt;</code>()</a>
 704 </h5>
 705 <p>
 706     </p>
 707 <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>
 708 </pre>
 709 <div class="variablelist">
 710 <p class="title"><b></b></p>
 711 <dl>
 712 <dt><span class="term">Returns:</span></dt>
 713 <dd><p>
 714             <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
 715             total order of <code class="computeroutput"><span class="identifier">execution_context</span></code>
 716             values places <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
 717             before <code class="computeroutput"><span class="identifier">other</span></code>, false otherwise.
 718           </p></dd>
 719 <dt><span class="term">Throws:</span></dt>
 720 <dd><p>
 721             Nothing.
 722           </p></dd>
 723 </dl>
 724 </div>
 725 <p>
 726       </p>
 727 <h5>
 728 <a name="ecv1_operator_greater_bridgehead"></a>
 729   <span><a name="ecv1_operator_greater"></a></span>
 730   <a class="link" href="ecv1.html#ecv1_operator_greater">Member
 731       function <code class="computeroutput">operator&gt;</code>()</a>
 732 </h5>
 733 <p>
 734     </p>
 735 <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>
 736 </pre>
 737 <div class="variablelist">
 738 <p class="title"><b></b></p>
 739 <dl>
 740 <dt><span class="term">Returns:</span></dt>
 741 <dd><p>
 742             <code class="computeroutput"><span class="identifier">other</span> <span class="special">&lt;</span>
 743             <span class="special">*</span> <span class="keyword">this</span></code>
 744           </p></dd>
 745 <dt><span class="term">Throws:</span></dt>
 746 <dd><p>
 747             Nothing.
 748           </p></dd>
 749 </dl>
 750 </div>
 751 <p>
 752       </p>
 753 <h5>
 754 <a name="ecv1_operator_lesseq_bridgehead"></a>
 755   <span><a name="ecv1_operator_lesseq"></a></span>
 756   <a class="link" href="ecv1.html#ecv1_operator_lesseq">Member
 757       function <code class="computeroutput">operator&lt;=</code>()</a>
 758 </h5>
 759 <p>
 760     </p>
 761 <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>
 762 </pre>
 763 <div class="variablelist">
 764 <p class="title"><b></b></p>
 765 <dl>
 766 <dt><span class="term">Returns:</span></dt>
 767 <dd><p>
 768             <code class="computeroutput"><span class="special">!</span> <span class="special">(</span><span class="identifier">other</span> <span class="special">&lt;</span>
 769             <span class="special">*</span> <span class="keyword">this</span><span class="special">)</span></code>
 770           </p></dd>
 771 <dt><span class="term">Throws:</span></dt>
 772 <dd><p>
 773             Nothing.
 774           </p></dd>
 775 </dl>
 776 </div>
 777 <p>
 778       </p>
 779 <h5>
 780 <a name="ecv1_operator_greatereq_bridgehead"></a>
 781   <span><a name="ecv1_operator_greatereq"></a></span>
 782   <a class="link" href="ecv1.html#ecv1_operator_greatereq">Member
 783       function <code class="computeroutput">operator&gt;=</code>()</a>
 784 </h5>
 785 <p>
 786     </p>
 787 <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>
 788 </pre>
 789 <div class="variablelist">
 790 <p class="title"><b></b></p>
 791 <dl>
 792 <dt><span class="term">Returns:</span></dt>
 793 <dd><p>
 794             <code class="computeroutput"><span class="special">!</span> <span class="special">(*</span>
 795             <span class="keyword">this</span> <span class="special">&lt;</span>
 796             <span class="identifier">other</span><span class="special">)</span></code>
 797           </p></dd>
 798 <dt><span class="term">Throws:</span></dt>
 799 <dd><p>
 800             Nothing.
 801           </p></dd>
 802 </dl>
 803 </div>
 804 <p>
 805       </p>
 806 <h5>
 807 <a name="ecv1__bridgehead"></a>
 808   <span><a name="ecv1_"></a></span>
 809   <a class="link" href="ecv1.html#ecv1_">Non-member function <code class="computeroutput">operator&lt;&lt;()</code></a>
 810 </h5>
 811 <p>
 812     </p>
 813 <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>
 814 <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>
 815 <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>
 816 </pre>
 817 <div class="variablelist">
 818 <p class="title"><b></b></p>
 819 <dl>
 820 <dt><span class="term">Efects:</span></dt>
 821 <dd><p>
 822             Writes the representation of <code class="computeroutput"><span class="identifier">other</span></code>
 823             to stream <code class="computeroutput"><span class="identifier">os</span></code>.
 824           </p></dd>
 825 <dt><span class="term">Returns:</span></dt>
 826 <dd><p>
 827             <code class="computeroutput"><span class="identifier">os</span></code>
 828           </p></dd>
 829 </dl>
 830 </div>
 831 </div>
 832 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 833 <td align="left"></td>
 834 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Oliver Kowalke<p>
 835         Distributed under the Boost Software License, Version 1.0. (See accompanying
 836         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>)
 837       </p>
 838 </div></td>
 839 </tr></table>
 840 <hr>
 841 <div class="spirit-nav">
 842 <a accesskey="p" href="ecv2.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="stack.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
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