https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99356
Bug ID: 99356
Summary: Recursive std::shared_future:s with
std::launch::deferred sporadically deadlock
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: fiesh at zefix dot tv
Target Milestone: ---
Trying to sail around 97949, we switched to using std::shared_future combined
with std::launch::deferred instead of using std::call_once.
Now again this leads to sporadic deadlocks under Windows.
The following code exemplifies the behavior:
----------------------------------------
#include <chrono>
#include <future>
#include <iostream>
#include <thread>
int main() {
auto const future0 =
std::shared_future<void>{std::async(std::launch::deferred, []() {
using namespace std::chrono_literals;
std::cout << "future0 running..." << std::endl;
std::this_thread::sleep_for(1s);
std::cout << "future0 done." << std::endl;
})};
auto const future1 =
std::shared_future<void>{std::async(std::launch::deferred, [future0]() {
std::cout << "future0 running..." << std::endl;
future0.get();
std::cout << "future0 done." << std::endl;
})};
auto const getFuture = [future1]() {
std::cout << "getting future1..." << std::endl;
future1.get();
std::cout << "got future1." << std::endl;
};
std::thread t0(getFuture);
std::thread t1(getFuture);
t0.join();
t1.join();
std::cout << "done" << std::endl;
}
----------------------------------------
If there's a workaround, we'd be very grateful.
