C++ std::async encounters system_error?

C++ std::async encounters system_error?

本文关键字：error system encounters std async C++      更新时间：2023-10-16

我在此处尝试了std：async示例代码http://www.cplusplus.com/reference/future/async/

但是，我遇到了带有未知错误-1的系统错误。有人可以帮我吗？谢谢！

以下是从网站复制的我的代码：

// async example
#include <iostream>       // std::cout
#include <future>         // std::async, std::future
// a non-optimized way of checking for prime numbers:
bool is_prime (int x) {
  std::cout << "Calculating. Please, wait...n";
  for (int i=2; i<x; ++i) if (x%i==0) return false;
  return true;
}
int main ()
{
  // call is_prime(313222313) asynchronously:
  std::future<bool> fut = std::async (is_prime,313222313);
  std::cout << "Checking whether 313222313 is prime.n";
  // ...
  bool ret = fut.get();      // waits for is_prime to return
  if (ret) std::cout << "It is prime!n";
  else std::cout << "It is not prime.n";
  return 0;
}

，以下是我的命令行：

ubuntu:~/cpp_dynamic_invoke_success/stdasync_test$ g++ isprime.cpp -std=c++11 -o isprime
ubuntu:~/cpp_dynamic_invoke_success/stdasync_test$ ./isprime 
Checking whether 313222313 is prime.
terminate called after throwing an instance of 'std::system_error'
  what():  Unknown error -1
Aborted (core dumped)

我的Ubuntu版本：

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.3 LTS
Release:    14.04
Codename:   trusty

和g 版本。

g++ (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

答案是添加 -pthread aftet汇编选项。

g++ isprime.cpp -std=c++11 -o isprime -pthread
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