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

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