Lambda Callback from Pthread?

Question

C++ / C#

The task is to pass a function to the lambda thread to handle, for example, the thread completion event (onload, or maybe onprogress).
I do it like this:

struct Arg {
    void (*func)();
};


void* threadFunction(void *arg) {

      ((Arg*) arg)->func();
}

void Network::open(const char * url, void (*onload)()) {

Arg* arg;
 arg->func = onload; /// сюда передается какая-то лямбда из внешнего метода []() {   };  
    pthread_attr_init(&attr);

    rc = pthread_create(&thread[0], &attr, threadFunction, arg);
    if (rc) {
        Logger::log("ERROR; return code from pthread_create() is %d\n", rc);
        return;
    }

    pthread_attr_destroy(&attr);
}

And without waiting for the thread to complete, I get RUN FINISHED; segmentation fault; core-dumped; , and this happens once in a while.
It turns out that onload is deleted without waiting for the execution of the thread, although it is just necessary that it be saved. How to solve it?

Answer 1

1) worth initializing Arg: Arg* arg = new Arg;
Don't forget to remove it at the end of use (as I understand it in threadFunction).
2) Use std::function<void()>functions instead of c-style to avoid unnecessary lambda removal problems.