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  1. #include <iostream>
  2. #include <thread>
  3. #include <unordered_map>
  4.  
  5. using namespace std;
  6.  
  7. class A { 
  8.  public:
  9.   A(unordered_map<int, int>& m) : m(m) {  
  10.   }
  11.   void Start() {
  12.     auto t = std::thread(test1, std::ref(m)); 
  13.     t.join();
  14.   }
  15.  private:
  16.   static void test1(unordered_map<int, int>&  m) {  // complie failed, if the ref change to value(remove &), it's ok, thats confused me
  17.     for (auto i : m) {
  18.       cout << i.first << i.second << endl;
  19.     }   
  20.   }
  21.   unordered_map<int, int> & m;
  22. };
  23.  
  24. int main() {
  25.   unordered_map<int, int> m = {{1,2}, {3,4}};
  26.   A a(m);
  27.   a.Start();
  28. }
  29.  
  30.  
Success #stdin #stdout 0s 4396KB
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34
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https://ideone.com/05hmoR
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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