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  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7. #define DBG(TEXT) do{cout << "( " << m_name << m_id << " " << #TEXT << " )" << endl;}while(0)
  8.  
  9. #define USE_MOVE_SEMANTICS
  10.  
  11. class Foo
  12. {
  13.     string m_name;
  14. 	unsigned int m_id;
  15. public:
  16.  
  17. 	// constructor
  18. 	Foo(const char *name)
  19. 		: m_name(name)
  20. 		, m_id(0)
  21. 	{
  22. 		DBG(constructor);
  23. 	}
  24.  
  25. 	// destructor
  26. 	~Foo()
  27. 	{
  28. 		DBG(destructor);
  29. 	}
  30.  
  31. 	// copy constructor
  32. 	Foo(const Foo &other)
  33. 		: m_name(other.m_name)
  34. 		, m_id(other.m_id + 1)
  35. 	{
  36. 		DBG(copy constructor);
  37. 	}
  38.  
  39. 	// copy assignment operator
  40. 	Foo &operator=(const Foo &other)
  41. 	{
  42. 		m_name = other.m_name;
  43. 		m_id = other.m_id + 1;
  44. 		DBG(copy assignment operator);
  45. 		return *this;
  46. 	}
  47.  
  48. #ifdef USE_MOVE_SEMANTICS
  49.  
  50. 	// move constructor
  51. 	Foo(Foo &&other)
  52. 		: m_name(other.m_name)
  53. 		, m_id(other.m_id + 1)
  54. 	{
  55. 		DBG(move constructor);
  56. 	}
  57.  
  58. 	// move assignment operator
  59. 	Foo &operator=(Foo &&other)
  60. 	{
  61. 		m_name = other.m_name;
  62. 		m_id = other.m_id + 1;
  63. 		DBG(move assignment operator);
  64. 		return *this;
  65. 	}
  66.  
  67. #endif // USE_MOVE_SEMANTICS
  68.  
  69. };
  70.  
  71. int main(void)
  72. {
  73. 	vector<Foo> vec;
  74. 	vec.reserve(1);
  75.  
  76. 	cout << "Foo a(\"A\");" << endl;
  77. 	Foo a("A");
  78.  
  79. 	cout << "vec.push_back(a);" << endl;
  80. 	vec.push_back(a); // No reallocation.
  81.  
  82. 	cout << "vec.push_back(Foo(\"B\"));" << endl;
  83. 	vec.push_back(Foo("B")); // Reallocate memory and move elements.
  84.  
  85. 	cout << "vec[0] = Foo(\"C\");" << endl;
  86. 	vec[0] = Foo("C");
  87.  
  88. 	cout << "return 0;" << endl;
  89. 	return 0;
  90. }
  91.  
Success #stdin #stdout 0s 3076KB
comments (?)
stdin 
Standard input is empty
stdout 
Foo a("A");
( A0 constructor )
vec.push_back(a);
( A1 copy constructor )
vec.push_back(Foo("B"));
( B0 constructor )
( B1 move constructor )
( A2 move constructor )
( A1 destructor )
( B0 destructor )
vec[0] = Foo("C");
( C0 constructor )
( C1 move assignment operator )
( C0 destructor )
return 0;
( A0 destructor )
( C1 destructor )
( B1 destructor )
https://ideone.com/L59FTW
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
secret

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