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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. // modified largely from
  5. // http://d...content-available-to-author-only...e.jp/toburau/20090722/1248283158
  6.  
  7. /*
  8. class Test {
  9. public:
  10. 	Test& operator=(const Test& rhs);
  11. };
  12. Test& Test::operator=(const Test& rhs)
  13. {
  14. 	if (this == &rhs) return *this;	         // *****
  15. };
  16. */
  17.  
  18. //-----------------------------------------------------
  19.  
  20. class Data
  21. {
  22. 	int num;
  23. public:
  24. 	Data(void) : num(0) { }
  25. 	Data(int _num) : num(_num) { }
  26. 	Data(const Data &rhs) {
  27. 		cout << "copy constructor is called" << endl;
  28. 		num = rhs.num;
  29. 	}
  30. 	void show(void) {
  31. 		cout << num << endl;
  32. 	}
  33. };
  34.  
  35. class CopyTest {
  36. 	Data *m_pData;
  37. public:
  38. 	CopyTest(void) {
  39. 		m_pData = new Data(0);
  40. 	}
  41. 	CopyTest(int _num) {
  42. 		m_pData = new Data(_num);
  43. 	}
  44. 	void show(void) {
  45. 		m_pData->show();
  46. 	}
  47. 	CopyTest& operator=(const CopyTest& rhs);
  48. };
  49.  
  50. CopyTest& CopyTest::operator=(const CopyTest& rhs) /*****/
  51. {
  52. 	Data *p = m_pData;
  53. //	m_pData = new Data(*rhs.m_pData); // case 0 // OK // copy constructor is called
  54. //	m_pData = new Data(*(rhs.m_pData)); // case 1 // OK
  55. 	m_pData = new Data(*(rhs).m_pData)); // case 2 // NG
  56. 	delete p;
  57. 	return *this;
  58. }
  59.  
  60.  
  61. int main() {
  62. 	CopyTest cpyObjA, cpyObjB(31);
  63.  
  64. 	cpyObjA.show();
  65. 	cpyObjB.show();
  66.  
  67. 	cout << "## after" << endl;	
  68. 	cpyObjA = cpyObjB;
  69. 	cpyObjA.show();
  70. 	cpyObjB.show();
  71.  
  72. 	return 0;
  73. }
Compilation error #stdin compilation error #stdout 0s 3428KB
comments (?)
stdin
copy 
Standard input is empty
compilation info 
prog.cpp: In member function ‘CopyTest& CopyTest::operator=(const CopyTest&)’:
prog.cpp:55:36: error: expected ‘;’ before ‘)’ token
  m_pData = new Data(*(rhs).m_pData)); // case 2 // NG
                                    ^
stdout
copy 
Standard output is empty
https://ideone.com/7qnzLP
自己代入その2 @ toburau
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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