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    <p>One of the founding principles of C++ is that you don't pay for what you don't use. That means in this case that contexts where taking a <code>shared_ptr</code> to <code>this</code> is unnecessary shouldn't incur any reference counting overhead. This also means that it shouldn't happen automatically even e.g. as a feature of <code>enable_shared_from_this</code>, since you might want to pass a short-lived lambda to an algorithm (<code>for_each</code>, etc.) in which case the lambda doesn't outlive its scope.</p> <p>I'd suggest adapting the <a href="http://jrb-programming.blogspot.co.uk/2012/11/another-alternative-to-lambda-move.html" rel="nofollow noreferrer">lambda-wrapper pattern</a>; in that case it's used for <code>move</code> capture of a large object (<a href="https://stackoverflow.com/questions/10280937/how-to-capture-stdunique-ptr-by-move-for-a-lambda-in-stdfor-each">How to capture std::unique_ptr &quot;by move&quot; for a lambda in std::for_each</a>), but it can equally be used for shared capture of <code>this</code>:</p> <pre><code>template&lt;typename T, typename F&gt; class shared_this_lambda { std::shared_ptr&lt;T&gt; t; // just for lifetime F f; public: shared_this_lambda(std::shared_ptr&lt;T&gt; t, F f): t(t), f(f) {} template&lt;class... Args&gt; auto operator()(Args &amp;&amp;...args) -&gt; decltype(this-&gt;f(std::forward&lt;Args&gt;(args)...)) { return f(std::forward&lt;Args&gt;(args)...); } }; template&lt;typename T&gt; struct enable_shared_this_lambda { static_assert(std::is_base_of&lt;std::enable_shared_from_this&lt;T&gt;, T&gt;::value, "T must inherit enable_shared_from_this&lt;T&gt;"); template&lt;typename F&gt; auto make_shared_this_lambda(F f) -&gt; shared_this_lambda&lt;T, F&gt; { return shared_this_lambda&lt;T, F&gt;( static_cast&lt;T *&gt;(this)-&gt;shared_from_this(), f); } template&lt;typename F&gt; auto make_shared_this_lambda(F f) const -&gt; shared_this_lambda&lt;const T, F&gt; { return shared_this_lambda&lt;const T, F&gt;( static_cast&lt;const T *&gt;(this)-&gt;shared_from_this(), f); } }; </code></pre> <p>Use by inheriting <code>enable_shared_this_lambda</code> in addition to <code>enable_shared_from_this</code>; you can then explicitly request that any long-lived lambdas take a shared <code>this</code>:</p> <pre><code>doSomethingAsynchronously(make_shared_this_lambda([this] { someMember_ = 42; })); </code></pre>
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    1. POUsing C++11 lambdas asynchronously, safely
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    1. USecatmur
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    1. COYes, but you also need to have someMember_ atomic or mutexed if threads are involved.
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      1. USJohan Lundberg
    2. COThanks, I think I'll adopt this pattern. Still not entirely convinced it's a good thing that shared_ptr is a library-level feature given that it makes this so cumbersome, but them's the breaks, I guess.
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      1. USNick Hutchinson
 

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