问题
I was looking for a way to stop a thread that perform a task every 2 seconds. I decided to try to use a std::promise/future so that the thread can exit immediately when the promise is set.
#include <future>
#include <iostream>
#include <chrono>
#include <csignal>
std::promise<void> stop;
int main() {
std::signal(SIGINT, [] (int) { stop.set_value(); } );
auto future = stop.get_future();
while (future.wait_for(std::chrono::seconds(1)) != std::future_status::ready) {
std::cout << "I'm still there" << std::endl;
}
}
Actually this does not work and crashes that way:
$ ./a.out I'm still there ^Cterminate called after throwing an instance of 'std::system_error'
what(): Unknown error -1 Abandon (core dumped)
Ok, One should take care of what he does in handler context, but I must say I was not expecting this crash; and I don't really understand it... Do you have any idea?
回答1:
I believe what you have here is undefined behaviour as a result of calling a standard library function (not in list of signal safe functions) in the signal handler.
The limitations on the signal handler function (that is user-defined) are extensive and are documented here.
Another thing to watch out for is if the signal handler refers to any object with static or thread-local(since C++11) storage duration that is not std::atomic
(since C++11) or volatile std::sig_atomic_t
.
And as @BasileStarynkevitch pointed out, if you are on Linux, ensure that only async-signal-safe functions are called from the signal handler.
来源:https://stackoverflow.com/questions/53015313/is-it-possible-to-set-a-promise-in-a-signal-handler