c++ - 错误 : "Attempt to use a deleted function" when moving a promise

Question

我正在尝试编写一个包含 promise / future 的示例。关于 this reference page 中的示例他们这样做了，并且在他们的在线编译器中工作得很好。当我在我的 Mac 上执行此操作(源代码在下面)时，它会抛出此错误，指示没有 move 运算符。谁能告诉我哪里出了问题？

头文件:

#ifndef Demonstration9_hpp
#define Demonstration9_hpp

#include <iostream>
#include <thread>
#include <future>

using namespace std;

inline namespace demo9
{
    class Demonstration9
    {
    private:
        bool Job1();
        void Job2();

    public:
        void Run();
    };
}

#endif /* Demonstration9_hpp */

源文件:

#include "Demonstration9.hpp"

bool job1(string test_string)
{
    this_thread::sleep_for(chrono::milliseconds(500));
    return test_string == "test";
}

void job2()
{
    this_thread::sleep_for(chrono::milliseconds(500));
}

bool Demonstration9::Run()
{
    promise<bool> j1_promise;
    future<bool> j1_future = j1_promise.get_future();
    thread t1(job1, "test", move(j1_promise));
    j1_future.wait();  // wait for result
    cout << "result=" << j1_future.get() << '\n';
    t1.join();  // wait for thread completion

    // Demonstrate using promise<void> to signal state between threads.
    promise<void> j2_promise;
    future<void> j2_future = j2_promise.get_future();
    thread t2(job2, move(j2_promise));
    j2_future.wait();
    t2.join();
}

构建日志:

In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.cpp:9: In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.hpp:13: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:342:5: error: attempt to use a deleted function __invoke(_VSTD::move(_VSTD::get<1>(__t)), _VSTD::move(_VSTD::get<_Indices>(__t))...); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:352:5: note: in instantiation of function template specialization 'std::__1::__thread_execute >, bool (*)(std::__1::basic_string), const char *, std::__1::promise , 2, 3>' requested here __thread_execute(__p, _Index()); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:368:47: note: in instantiation of function template specialization 'std::__1::__thread_proxy >, bool (*)(std::__1::basic_string), const char *, std::__1::promise > >' requested here int __ec = __libcpp_thread_create(&__t_, &__thread_proxy<_Gp>, __p.get()); ^ /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.cpp:26:12: note: in instantiation of function template specialization 'std::__1::thread::thread), char const (&)[5], std::__1::promise , void>' requested here thread t1(job1, "test", move(j1_promise)); ^ In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.cpp:9: In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.hpp:12: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/iostream:38: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ios:216: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__locale:15: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:470: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string_view:169: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__string:56: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/algorithm:640: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1590:5: note: '~__nat' has been explicitly marked deleted here ~__nat() = delete; ^ In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.cpp:9: In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.hpp:13: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:342:5: error: attempt to use a deleted function __invoke(_VSTD::move(_VSTD::get<1>(__t)), _VSTD::move(_VSTD::get<_Indices>(__t))...); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:352:5: note: in instantiation of function template specialization 'std::__1::__thread_execute >, void (*)(), std::__1::promise , 2>' requested here __thread_execute(__p, _Index()); ^ /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:368:47: note: in instantiation of function template specialization 'std::__1::__thread_proxy >, void (*)(), std::__1::promise > >' requested here int __ec = __libcpp_thread_create(&__t_, &__thread_proxy<_Gp>, __p.get()); ^ /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.cpp:34:12: note: in instantiation of function template specialization 'std::__1::thread::thread , void>' requested here thread t2(job2, move(j2_promise)); ^ In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.cpp:9: In file included from /Users/maurits/Github/CPP-Demonstrations/src/Demonstration9.hpp:12: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/iostream:38: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/ios:216: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__locale:15: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:470: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string_view:169: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__string:56: In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/algorithm:640: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1590:5: note: '~__nat' has been explicitly marked deleted here ~__nat() = delete; ^ 2 errors generated.

Answer 1

线

thread t1(job1, "test", move(j1_promise));

正在尝试调用

job1("test", move(j1_promise));

在一个单独的线程中。但是您的 job1 只接受一个参数。