Question

我在这里尝试了std：async示例代码 http://www.cplusplus.com/reference/future/async/

但是，遇到未知错误-1的系统错误。有人可以帮帮我吗？谢谢！

以下是我从网站上复制的代码：

// 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.

Answer 1

答案是在编译选项后添加 $ gcc -O3 -g -std=c11 -Wall -Wextra -Werror -Wmissing-prototypes \ > -Wstrict-prototypes -c sw73.c sw73.c: In function ‘shift_CLON’: sw73.c:9:17: error: result of ‘117901309 << 24’ requires 52 bits to represent, but ‘int’ only has 32 bits [-Werror=shift-overflow=] return CLON << 24; ^~ cc1: all warnings being treated as errors $ 。

-pthread

C ++ std :: async遇到system_error？

1 个答案: