atomic/example8.cpp

// atomic::compare_exchange_weak example:
#include <iostream>       // std::cout
#include <atomic>         // std::atomic
#include <thread>         // std::thread
#include <vector>         // std::vector

// a simple global linked list:
struct Node { int value; Node* next; };
std::atomic<Node*> list_head (nullptr);

void append (int val) {     // append an element to the list
 Node* oldHead = list_head;
 Node* newNode = new Node {val,oldHead};

 // what follows is equivalent to: list_head = newNode, but in a thread-safe way:
 while (!list_head.compare_exchange_weak(oldHead,newNode))
   newNode->next = oldHead;
}

int main ()
{
 // spawn 10 threads to fill the linked list:
 std::vector<std::thread> threads;
 for (int i=0; i<10; ++i) threads.push_back(std::thread(append,i));
 for (auto& th : threads) th.join();

 // print contents:
 for (Node* it = list_head; it!=nullptr; it=it->next)
   std::cout << ' ' << it->value;
 std::cout << '\n';

 // cleanup:
 Node* it; while (it=list_head) {list_head=it->next; delete it;}

 return 0;
}