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    <p>Firstly, this signature will not compile:</p> <pre><code>// inside spinlock class template&lt;typename F, typename... Ars&gt; std::result_of(F(Args...)) exec(F fun, Args&amp;&amp;... args) { // locks the memory and then executes fun(args...) }; </code></pre> <p>The return type needs to be</p> <pre><code>typename std::result_of&lt;F(Args...)&gt;::type </code></pre> <p>If your compiler implements <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3436.html" rel="nofollow">N3436</a> then this function will not participate in overload resolution when <code>fun(args...)</code> is not a valid expression, but that is not required in C++11 and not implemented by many compilers yet. You will need to implement your own SFINAE check to prevent <code>result_of</code> giving an error when <code>fun(args...)</code> is not valid, or rewrite it without <code>result_of</code></p> <pre><code>template&lt;typename F, typename... Args&gt; auto exec(F fun, Args&amp;&amp;... args) -&gt; decltype(fun(std::forward&lt;Args&gt;(args)...)) { // locks the memory and then executes fun(args...) } </code></pre> <p>Then you can overload it for functions that need the additional parameter passed in:</p> <pre><code>template&lt;typename F, typename... Args&gt; auto exec(F fun, Args&amp;&amp;... args) -&gt; decltype(fun(*this-&gt;shared_memory, std::forward&lt;Args&gt;(args)...)) { // locks the memory and then executes fun(*shared_memory, args...) } </code></pre> <p>When <code>fun(std::forward&lt;Args&gt;(args)...)</code> is not valid the first overload will not participate in overload resolution. When <code>fun(*this-&gt;shared_memory, std::forward&lt;Args&gt;(args)...)</code> is not valid the second overload will not participate in overload resolution. If neither is valid the call will be ill-formed, if both are valid the call will be ambiguous.</p>
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    1. COYeah, sorry, `typename std::result_of<F(Args...)>::type` was actually what I meant (I wrote kinda quickly). But... I've tested your SFINAE (which I knew what was, but never tried using it)... worked perfectly! Thank you very much! =D
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    2. COBoth your signatures worked if T isn't void; but what should I do to prevent a reference to void if T (from the class) is void? :(
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    3. COI didn't understand your question until I realized you want to pass `volatile T&` but the `spinlock::shared_memory` member is a `volatile T*` so I've edited my answer to use `*this->shared_memory` ... but obviously that won't work if `T` is `void`, there's no way you can declare a function to take `volatile void&` anyway so it shouldn't be a problem
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