如何进行多线程队列处理

Question

默认情况下，C++容器应该是线程安全的。我必须错误地使用queue多线程，因为对于此代码：

#include <thread>
using std::thread;
#include <iostream>
using std::cout;
using std::endl;
#include <queue>
using std::queue;
#include <string>
using std::string;
using std::to_string;
#include <functional>
using std::ref;


void fillWorkQueue(queue<string>& itemQueue) {
    int size = 40000;
    for(int i = 0; i < size; i++)
        itemQueue.push(to_string(i));
}

void doWork(queue<string>& itemQueue) {
    while(!itemQueue.empty()) {
        itemQueue.pop();
    }   
}

void singleThreaded() {
    queue<string> itemQueue;
    fillWorkQueue(itemQueue);
    doWork(itemQueue);
    cout << "done\n";
}

void multiThreaded() {
    queue<string> itemQueue;
    fillWorkQueue(itemQueue);
    thread t1(doWork, ref(itemQueue));
    thread t2(doWork, ref(itemQueue));
    t1.join();
    t2.join();
    cout << "done\n";
}

int main() {
    cout << endl;

    // Single Threaded
    cout << "singleThreaded\n";
    singleThreaded();
    cout << endl;

    // Multi Threaded
    cout << "multiThreaded\n";
    multiThreaded();
    cout << endl;
}

我得到了：

singleThreaded
done

multiThreaded
main(32429,0x10e530000) malloc: *** error for object 0x7fe4e3883e00: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
make: *** [run] Abort trap: 6

Answer 1

正如注释中指出的，STL容器对于读写操作不是线程安全的。而是从TBB或PPL中尝试concurrent_queue类，例如：

void doWork(concurrent_queue<string>& itemQueue) {
    string result;
    while(itemQueue.try_pop(result)) {
        // you have `result`
    }   
}