Wrap and execute packaged_task inside lambda

Question

I'm trying to wrap a packaged_task in a lambda in order to stock them inside a container. I wrote a test code below for simulating the wrapping and calling the lambda function. My code is as follows:

int test()
{
    return 10;
}

int main()
{
    auto task = std::make_shared<std::packaged_task<int()>>(test);
    auto result = task->get_future();
    auto wrapper = [=]() { (*task)(); };
    wrapper();
}

The program got aborted with the following exception:

terminate called after throwing an instance of 'std::system_error' what(): Unknown error -1 Aborted (core dumped)

Could someone explain me why the exception is thrown?

score 3 · Accepted Answer · answered Jan 07 '19 at 17:13

3

std::packaged_task::operator() indirectly uses std::call_once, which, according to this link, requires pthread library to operate, otherwise it throws std::system_error. So to get rid of this exception, you need to build with -lpthread. Sounds weird, but worked for me.

answered Jan 07 '19 at 17:13

grungegurunge

841
7
13

Yes it is working by adding -lpthread to my gcc command. Thank you very much! – Minee Jan 07 '19 at 20:52

Wrap and execute packaged_task inside lambda

1 Answers1