Can C++11 tell if std::thread is active?
No, I don't think that this is possible. I would also try to think about your design and if such a check is really necessary, maybe you are looking for something like the interruptible threads from boost.
However, you can use std::async
- which I would do anyway - and then rely on the features std::future
provides you.
Namely, you can call std::future::wait_for
with something like std::chrono::seconds(0)
. This gives you a zero-cost check and enables you to compare the std::future_status
returned by wait_for
.
auto f = std::async(foo);
...
auto status = f.wait_for(std::chrono::seconds(0));
if(status == std::future_status::timeout) {
// still computing
}
else if(status == std::future_status::ready) {
// finished computing
}
else {
// There is still std::future_status::defered
}
Gearoid Murphy
https://www.linkedin.com/in/gearoid-murphy-a6003983/
Updated on July 06, 2022Comments
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Gearoid Murphy almost 2 years
To my surprise, a C++11 std::thread object that has finished executing, but has not yet been joined is still considered an active thread of execution. This is illustrated in the following code example (built on Xubuntu 13.03 with g++ 4.7.3). Does anyone know if the C++11 standard provides a means to detect if a std::thread object is still actively running code?
#include <thread> #include <chrono> #include <iostream> #include <pthread.h> #include <functional> int main() { auto lambdaThread = std::thread([](){std::cout<<"Excuting lambda thread"<<std::endl;}); std::this_thread::sleep_for(std::chrono::milliseconds(250)); if(lambdaThread.joinable()) { std::cout<<"Lambda thread has exited but is still joinable"<<std::endl; lambdaThread.join(); } return 0; }
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Gearoid Murphy over 10 yearsThat's a nice solution
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Yann over 9 yearsWorth noting that this is c++11, so using semaphores might have to be the solution if you don't have that available