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    copied!<p>There is no (standard) way to reach into a thread and kill it, and this is generally a bad idea anyway. The much cleaner option is to pass a starting time and max duration to the function and then (possibly multiple times as the calculation progresses) check if the current time minus the starting time is too long.</p> <p>I would make something like this:</p> <pre><code>#include &lt;chrono&gt; template &lt;typename Clock = std::chrono::steady_clock&gt; class timeout { public: typedef Clock clock_type; typedef typename clock_type::time_point time_point; typedef typename clock_type::duration duration; explicit timeout(duration maxDuration) : mStartTime(clock_type::now()), mMaxDuration(maxDuration) {} time_point start_time() const { return mStartTime; } duration max_duration() const { return mMaxDuration; } bool is_expired() const { const auto endTime = clock_type::now(); return (endTime - start_time()) &gt; max_duration(); } static timeout infinity() { return timeout(duration::max()); } private: time_point mStartTime; duration mMaxDuration; }; </code></pre> <p>This simple utility tracks the starting time and a max duration (and provides a way of specifying infinity), and allows the user to query simple facts, most importantly whether or not a timeout has occurred.</p> <p>Test below; you can add fake delay by defining/undefining <code>FAKE_DELAY</code>:</p> <pre><code>#include &lt;iostream&gt; #include &lt;future&gt; #define FAKE_DELAY void fake_delay() { #ifdef FAKE_DELAY std::this_thread::sleep_for(std::chrono::milliseconds(1000)); #endif } void short_running_function(timeout&lt;&gt; timelimit) { fake_delay(); if (timelimit.is_expired()) std::cout &lt;&lt; "short running thread ran out of time" &lt;&lt; std::endl; else std::cout &lt;&lt; "short running function finished" &lt;&lt; std::endl; } void long_running_function(timeout&lt;&gt; timelimit) { for (unsigned i = 0; i &lt; 10; ++i) { if (timelimit.is_expired()) { std::cout &lt;&lt; "long running thread ran out of time" &lt;&lt; std::endl; return; } std::cout &lt;&lt; "long running thread doing work" &lt;&lt; std::endl; fake_delay(); } std::cout &lt;&lt; "long running function finished" &lt;&lt; std::endl; } int main() { std::async(short_running_function, timeout&lt;&gt;(std::chrono::milliseconds(500))).wait(); std::async(short_running_function, timeout&lt;&gt;(std::chrono::milliseconds(5000))).wait(); std::async(long_running_function, timeout&lt;&gt;(std::chrono::milliseconds(500))).wait(); std::async(long_running_function, timeout&lt;&gt;(std::chrono::milliseconds(5000))).wait(); std::async(long_running_function, timeout&lt;&gt;::infinity()).wait(); } </code></pre> <p>One possible output with <code>FAKE_DELAY</code> <strong>off</strong>:</p> <blockquote> <p>short running function finished<br> short running function finished<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running function finished<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running function finished<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running function finished </p> </blockquote> <p>One possible output with <code>FAKE_DELAY</code> <strong>on</strong>:</p> <blockquote> <p>short running thread ran out of time<br> short running function finished<br> long running thread doing work<br> long running thread ran out of time<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread ran out of time<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running thread doing work<br> long running function finished </p> </blockquote>
 

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