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  1. #include <iostream>
  2. #include <memory>
  3.  
  4. int main()
  5. {
  6.     // create a sharable allocation
  7.     std::shared_ptr<int> var1 = std::make_shared<int>(102);
  8.     std::cout << "*var1 = " << *var1 << '\n';
  9.  
  10.     // create a weak pointer to our shared pointer. we can't do much with
  11.     //  it until we convert it to a shared pointer
  12.     std::weak_ptr<int> var2 = var1;
  13.  
  14.     try
  15.     {   // try shared pointer conversion
  16.         std::shared_ptr<int> varx(var2);
  17.         std::cout << "*var2 = " << *varx << '\n';
  18.     }
  19.     catch(std::exception const& ex)
  20.     {
  21.         std::cout << "Exception: " << ex.what() << '\n';
  22.     }
  23.  
  24.     // release original shared pointer. this will release
  25.     //  the only hard reference to the data, and all weak
  26.     //  pointers become invalid.
  27.     var1.reset();
  28.  
  29.     try
  30.     {   // try that again, but this time it should not work
  31.         std::shared_ptr<int> varx(var2);
  32.         std::cout << "*var2 = " << *varx << '\n';
  33.     }
  34.     catch(std::exception const& ex)
  35.     {
  36.         std::cout << "Exception: " << ex.what() << '\n';
  37.     }
  38. }
Success #stdin #stdout 0s 3480KB
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stdin
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Standard input is empty
stdout
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*var1 = 102
*var2 = 102
Exception: bad_weak_ptr
https://ideone.com/UXb2lO
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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