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  1. #include <thread>
  2. #include <iostream>
  3.  
  4. class cl1;
  5. class cl2;
  6.  
  7.  
  8. class cl2 {
  9. public:
  10.     int y;
  11.     cl2(int y) : y(y)   {}          		//ctor
  12. };
  13.  
  14. class cl1 {
  15. public:
  16.     int x;
  17.     cl1(int x) : x(x) {}             	 //ctor
  18.     cl1(cl2& ob1) : x(ob1.y * 2) {}      //ctor for automatic conversion of cl2& to cl1, x = y*2
  19. };
  20.  
  21. void do_work_with_cl(cl1 ob) {				//This works as usual by actually copying the object through the copy constructor
  22.     std::cout << "The x of ob is " << ob.x << std::endl;
  23. }
  24.  
  25. void do_work_with_cl_rref(cl1&& ob) {		//I guess this works because it takes an rvalue and the automatic
  26.                                             //conversion ctor of cl1 does just that
  27.     std::cout <<"Inside the function that takes cl1 as rvalue, x of ob is"  << ob.x << std::endl;
  28. }
  29.  
  30. void do_work_with_cl_lref(cl1& ob) {		//This doesn't work as ob is non-const lvalue reference
  31.     std::cout << "lvalue referenced but the object created through implicit conversion is temporary(i.e rvalue)" << std::endl;
  32. }
  33.  
  34.  
  35. int main() {
  36.     //Normal non-threaded calls
  37.     cl2 ob(100);				//create a cl2 object
  38.     do_work_with_cl(ob);			//This is ok
  39.     do_work_with_cl_rref(ob);	//This too works
  40.     //do_work_with_cl_lref(ob)	//This fails, as suspected
  41.  
  42.     std::cout << "Thread part" << std::endl;
  43.  
  44.     //Now calling the functions through a thread
  45.     std::thread t1(do_work_with_cl_rref, ob);	//Thought this could work here, but doesn't
  46.                                                 //The other functions also don't work, but I can understand why.
  47.     t1.join();
  48. }
  49.  
Success #stdin #stdout 0s 11224KB
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stdin
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Standard input is empty
stdout
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The x of ob is 200
Inside the function that takes cl1 as rvalue, x of ob is200
Thread part
Inside the function that takes cl1 as rvalue, x of ob is200
https://ideone.com/MPZc4C
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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