std::thread 调用 class 方法

Question

I have a small class:

class MyData{
    Struct1* pS;
public:
    MyData() {
        pS=new Struct1;
    }
    void saveData(Struct1* st) {
        *pS = *st;
    }
    void printData() {
        //print the struct
    }
};

I want to modify the struct (call saveData) from a thread that needs to be running in the background, while the program may call printData sometime.

I have this at the moment, but i don't know if it's thread safe.

void myFunction(MyData* data) {
    while(1){
        data->saveData(someStruct);
    }
}

int main{
    MyData *data = new MyData() ;
    std::thread th_object(myFunction, data) ;
    // more code
    data->printData() ;
}

I also need a way to stop the thread when the programm reaches the end.

Answer 1

You should protect the members from data races with a mutex . Example:

#include <mutex>
#include <thread>
#include <atomic>

struct Struct1 {};

class MyData {
    Struct1 pS;
    std::mutex m_;

public:
    void saveData(Struct1* st) {
        std::unique_lock<std::mutex> lock(m_);
        pS = *st;
    }
    void printData() {
        std::unique_lock<std::mutex> lock(m_);
        Struct1 copy = pS;
        lock.unlock();
        // print copy
    }
};

void myFunction(MyData* data, std::atomic<bool>* stop) {
    while(!*stop) {
        Struct1 s;
        data->saveData(&s);
    }
}

int main() {
    MyData data;
    std::atomic<bool> stop{false};
    std::thread th_object(myFunction, &data, &stop) ;
    data.printData();
    stop = true;
    th_object.join();
}