Fix destruction order problem in getCoreAllocator

[folly.git] / folly / futures / README.md

diff --git a/folly/futures/README.md b/folly/futures/README.md
index a9d7d88e7e28f88dad14c5a352001e3048fe7f75..ec50fa8d1fbec2f4351dd994462cc427de4350fb 100644 (file)
--- a/folly/futures/README.md
+++ b/folly/futures/README.md
@@ -159,7 +159,7 @@ Although inspired by the C++11 std::future interface, it is not a drop-in replac
 </span><span class="n">p</span><span class="p">.</span><span class="n">setValue</span><span class="p">(</span><span class="p">)</span><span class="p">;</span><span class="">
 </span></pre></div>
 
-<p>This is legal and technically threadsafe. However, it is important to realize that you do not know in which thread <tt>x</tt>, <tt>y</tt>, and/or <tt>z</tt> will execute. Maybe they will execute in Thread A when <tt>p.setValue()</tt> is called. Or, maybe they will execute in Thread B when <tt>f.then</tt> is called. Or, maybe <tt>x</tt> will execute in Thread B, but <tt>y</tt> and/or <tt>z</tt> will execute in Thread A. There&#039;s a race between <tt>setValue</tt> and <tt>then</tt>&#x2014;whichever runs last will execute the callback. The only guarantee is that one of them will run the callback.</p>
+<p>This is legal and technically threadsafe. However, it is important to realize that you do not know in which thread <tt>x</tt>, <tt>y</tt>, and/or <tt>z</tt> will execute. Maybe they will execute in Thread A when <tt>p.setValue()</tt> is called. Or, maybe they will execute in Thread B when <tt>f.then</tt> is called. Or, maybe <tt>x</tt> will execute in Thread A, but <tt>y</tt> and/or <tt>z</tt> will execute in Thread B. There&#039;s a race between <tt>setValue</tt> and <tt>then</tt>&#x2014;whichever runs last will execute the callback. The only guarantee is that one of them will run the callback.</p>
 
 <p>Naturally, you will want some control over which thread executes callbacks. We have a few mechanisms to help.</p>
 
@@ -824,13 +824,19 @@ Although inspired by the C++11 std::future interface, it is not a drop-in replac
 <p>Interrupts allow Future holders to send signals in the form of exceptions to Promise holders, who are free to handle the interrupt as they please (or not at all). For example:</p>
 
 <div class="remarkup-code-block" data-code-lang="cpp"><pre class="remarkup-code"><span class="k">auto</span><span class=""> </span><span class="n">p</span><span class=""> </span><span class="o">=</span><span class=""> </span><span class="n">std</span><span class="o">:</span><span class="o">:</span><span class="n">make_shared</span><span class="o">&lt;</span><span class="n">Promise</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="o">&gt;</span><span class="p">(</span><span class="p">)</span><span class="p">;</span><span class="">
-</span><span class="n">p</span><span class="o">-</span><span class="o">&gt;</span><span class="n">setInterruptHandler</span><span class="p">(</span><span class="p">[</span><span class="n">p</span><span class="p">]</span><span class="p">(</span><span class="k">const</span><span class=""> </span><span class="n">exception_wrapper</span><span class="o">&amp;</span><span class=""> </span><span class="n">e</span><span class="p">)</span><span class="p">&#123;</span><span class="">
+</span><span class="n">p</span><span class="o">-</span><span class="o">&gt;</span><span class="n">setInterruptHandler</span><span class="p">(</span><span class="p">[</span><span class="n">weakPromise</span><span class=""> </span><span class="o">=</span><span class=""> </span><span class="n">folly</span><span class="o">:</span><span class="o">:</span><span class="n">to_weak_ptr</span><span class="p">(</span><span class="n">p</span><span class="p">)</span><span class="p">]</span><span class="p">(</span><span class="">
+</span><span class="">    </span><span class="k">const</span><span class=""> </span><span class="n">exception_wrapper</span><span class="o">&amp;</span><span class=""> </span><span class="n">e</span><span class="p">)</span><span class=""> </span><span class="p">&#123;</span><span class="">
+</span><span class="">  </span><span class="k">auto</span><span class=""> </span><span class="n">promise</span><span class=""> </span><span class="o">=</span><span class=""> </span><span class="n">weakPromise</span><span class="p">.</span><span class="n">lock</span><span class="p">(</span><span class="p">)</span><span class="p">;</span><span class="">
 </span><span class="">  </span><span class="c1">// Handle the interrupt. For instance, we could just fulfill the Promise
 </span><span class="">  </span><span class="c1">// with the given exception:
-</span><span class="">  </span><span class="n">p</span><span class="o">-</span><span class="o">&gt;</span><span class="n">setException</span><span class="p">(</span><span class="n">e</span><span class="p">)</span><span class="p">;</span><span class="">
-</span><span class="">  
-  </span><span class="c1">// Or maybe we want the Future to complete with some special value
-</span><span class="">  </span><span class="n">p</span><span class="o">-</span><span class="o">&gt;</span><span class="n">setValue</span><span class="p">(</span><span class="mi">42</span><span class="p">)</span><span class="p">;</span><span class="">
+</span><span class="">  </span><span class="k">if</span><span class=""> </span><span class="p">(</span><span class="n">promise</span><span class="p">)</span><span class=""> </span><span class="p">&#123;</span><span class="">
+</span><span class="">    </span><span class="n">promise</span><span class="o">-</span><span class="o">&gt;</span><span class="n">setException</span><span class="p">(</span><span class="n">e</span><span class="p">)</span><span class="p">;</span><span class="">
+</span><span class="">  </span><span class="p">&#125;</span><span class="">
+</span><span class="">
+</span><span class="">  </span><span class="c1">// Or maybe we want the Future to complete with some special value
+</span><span class="">  </span><span class="k">if</span><span class=""> </span><span class="p">(</span><span class="n">promise</span><span class="p">)</span><span class=""> </span><span class="p">&#123;</span><span class="">
+</span><span class="">    </span><span class="n">promise</span><span class="o">-</span><span class="o">&gt;</span><span class="n">setValue</span><span class="p">(</span><span class="mi">42</span><span class="p">)</span><span class="p">;</span><span class="">
+</span><span class="">  </span><span class="p">&#125;</span><span class="">
 </span><span class="">
 </span><span class="">  </span><span class="c1">// Or maybe we don&#039;t want to do anything at all! Including not setting
 </span><span class="">  </span><span class="c1">// this handler in the first place.