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我正在尝试构建一个异步应用程序以允许并行处理大型列表，经过两天的谷歌搜索学习C++，我从以下代码中发现了标题错误：

//
//  main.cpp
//  ThreadedLearning
//
//  Created by Andy Kirk on 19/01/2016.
//  Copyright © 2016 Andy Kirk. All rights reserved.
//
#include <iostream>
#include <thread>
#include <vector>
#include <chrono>
#include <future>
typedef struct {
    long    mailing_id;
    char    emailAddress[100];
} emailStruct ;
typedef struct {
    long    mailing_id = 0;
    int     result = 0;
} returnValues;
returnValues work(emailStruct eMail) {
    returnValues result;
    std::this_thread::sleep_for(std::chrono::seconds(2));
    result.mailing_id = eMail.mailing_id;
    return result;
}
int main(int argc, const char * argv[]) {
    std::vector<emailStruct>    Emails;
    emailStruct eMail;
    // Create a Dummy Structure Vector
    for (int i = 0 ; i < 100 ; ++i) {
        std::snprintf(eMail.emailAddress,sizeof(eMail.emailAddress),"user-%d@email_domain.tld",i);
        eMail.mailing_id = i;
        Emails.push_back(eMail);
    }

    std::vector<std::future<returnValues>> workers;
    int worker_count = 0;
    int max_workers  = 11;

    for ( ; worker_count < Emails.size(); worker_count += max_workers ){
        workers.clear();
        for (int inner_count = 0 ; inner_count < max_workers ; ++inner_count) {
            int entry = worker_count + inner_count;
            if(entry < Emails.size()) {
                emailStruct workItem = Emails[entry];
                auto fut = std::async(&work, workItem);
                workers.push_back(fut);
            }
        }
        std::for_each(workers.begin(), workers.end(), [](std::future<returnValues> & res) {
            res.get();
        });
    }
    return 0;
}

真的不知道我做错了什么，并且找到了有限的答案搜索。 如果相关的话，它在OSX 10和XCode 7上。