class 的移动构造函数和移动赋值运算符

Question

我正在尝试为嵌入式设备编译以下代码（它是来自 TI 的交叉编译器，具有 C++11 (C++0) 的实验性支持）。目标：

arm-arago-linux-gnueabi Thread model: posix gcc version 4.5.3 20110311 (prerelease) (GCC)

无法编译移动构造函数和移动赋值运算符的默认说明符 (/home/user/test/main.cpp:40:26: error: 'th& th::operator=(th&&)' cannot be defaulted)。

std::make_unique & emplace_back 未实现，那些不可用。

我需要更改代码中的哪些内容才能使其适用于此平台？

class th {
    public:
        void func() {
            sleep(3);
            *this->progress = 100;
        }

        th(int* prog) :
            progress(prog), 
            m_thread(std::thread(&th::func, this)) {};

        th(th const& other) = delete;
        th(th && other) = default;
        th& operator=(th const& other) = delete;
        th& operator=(th &&) = default;

        void join() { m_thread.join(); }
        int *progress;

    private:
        std::thread m_thread;
};

int main(void) {

        std::vector<int> progress;
        progress.push_back(-1);
        progress.push_back(-1);

        std::deque<std::unique_ptr<th>> deq;

        std::cout << "progress[0]:" << progress[0] << std::endl;
        std::cout << "progress[1]:" << progress[1] << std::endl;

        std::cout << "executing threads..." << std::endl;

        for(size_t i = 0; i < 2; ++i) {
            deq.push_back(std::unique_ptr<th>(new th(&progress[i])));
        }

        while(true) {
            std::cout << "SIZE:" << deq.size() << std::endl;

            if(deq.size() == 0)
                break;

            for (std::deque<std::unique_ptr<th>>::iterator it = deq.begin(); it != deq.end(); it++) {
                //std::cout << (*it)->progress << std::endl;
                if(*((*it)->progress) == 100) {
                    std::cout << "JOIN & DELETE" << std::endl;
                    (*it)->join();
                    deq.erase(it);
                }
                else {
                    std::cout << "STILL RUNNING" << std::endl;
                }
                    //std::cout << *((*it)->progress) << std::endl;
            }
            sleep(1);
        }

    exit(EXIT_SUCCESS);
}

Answer 1

gcc 4.5.x不支持生成move特殊成员函数，see N3053 for more details, and also https://gcc.gnu.org/gcc-4.5/cxx0x_status.html for the gcc C++11 support features, so you're out of luck with the compiler. Your code compiles fine on gcc5/6 and clang, see it live here.

一个选择是完全删除这些行

th(th const& other) = delete;
th(th && other) = default;
th& operator=(th const& other) = delete;
th& operator=(th &&) = default;

并让编译器完成工作并为您生成特殊的成员函数。顺便说一句，默认情况下将删除复制构造函数和复制赋值运算符，因为 std::thread 是不可复制的。

class 的移动构造函数和移动赋值运算符

Move constructor and move assignement operator for class

c++

gcc

move-semantics

c++11