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  1. #include <array>
  2. #include <iostream>
  3. #include <memory>
  4.  
  5. const size_t N = 5;
  6.  
  7. struct A
  8. {
  9.   int x;
  10.   A(int x) : x(x) { std::cout << "Created" << std::endl; }
  11.   A(const A& rhs) : x(rhs.x) { std::cout << "Copied" << std::endl; }
  12.   ~A() { std::cout << "Destroyed" << std::endl; }
  13. };
  14.  
  15. int makeElement(size_t i)
  16. {
  17.   return i * i;
  18. }
  19.  
  20. struct Deleter 
  21. {
  22.   Deleter() {};
  23.   void operator()(std::array<A, N>* p) const 
  24.   { 
  25.     for (auto& item : *p) { item.~A(); }
  26.     std::return_temporary_buffer(p); 
  27.   };
  28. };
  29.  
  30. std::unique_ptr<std::array<A, N>, Deleter> makeArrayDynamically()
  31. {
  32.   A* buf;
  33.   std::tie(buf, std::ignore) = std::get_temporary_buffer<A>(N);
  34.   for (size_t i = 0; i < N; ++i)
  35.   {
  36.     new (buf + i) A(makeElement(i));  // Yeah, I will have a leak if some constructor throws
  37.   }
  38.   return { reinterpret_cast<std::array<A, N>*>(buf), Deleter() };
  39. }
  40.  
  41. int main() 
  42. {
  43.   const auto pArr = makeArrayDynamically();
  44.  
  45.   for (const auto& item : *pArr)
  46.   {
  47.     std::cout << item.x << std::endl;    
  48.   }
  49. }
  50.  
Success #stdin #stdout 0s 3460KB
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stdin
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Standard input is empty
stdout
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Created
Created
Created
Created
Created
0
1
4
9
16
Destroyed
Destroyed
Destroyed
Destroyed
Destroyed
https://ideone.com/tbw5lm
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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