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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. struct T { 
  5. 	virtual void foo();
  6. 	int i;
  7. };
  8.  
  9. void displayT() {
  10. 	T ob;
  11. 	char *base = (char*)&ob; // spare me the new style casts
  12. 	int off_i = (char*)&ob.i - base;
  13. 	cout << "sizeof T is " << sizeof ob;
  14. 	cout << "\nsizeof i is " << sizeof ob.i;
  15. 	cout << "\ni is at offset " << off_i;
  16.  
  17. 	string layout (sizeof ob, '*');
  18. 	layout.replace (off_i, sizeof ob.i, sizeof ob.i, 'i');
  19. 	cout << "\nlayout of T is \n" << layout << "\n";
  20. }
  21.  
  22. struct U { 
  23. 	virtual void bar();
  24. 	long long l;
  25. };
  26.  
  27. void displayU() {
  28. 	U ob;
  29. 	char *base = (char*)&ob;
  30. 	int off_l = (char*)&ob.l - base;
  31. 	cout << "sizeof U is " << sizeof ob;
  32. 	cout << "\nsizeof U::l is " << sizeof ob.l;
  33. 	cout << "\nl is at offset " << off_l;
  34.  
  35. 	string layout (sizeof ob, '*');
  36. 	layout.replace (off_l, sizeof ob.l, sizeof ob.l, 'l');
  37. 	cout << "\nlayout of U is \n" << layout << "\n";
  38. }
  39.  
  40. struct Der : T, U{ 
  41. };
  42.  
  43. void displayDer() {
  44. 	Der ob;
  45. 	T &t = ob;
  46. 	U &u = ob;
  47. 	char *base = (char*)&ob;
  48. 	int off_i = (char*)&ob.i - base;
  49. 	int off_l = (char*)&ob.l - base;
  50. 	int off_T = (char*)&t - base;
  51. 	int off_U = (char*)&u - base;
  52.  
  53. 	cout << "sizeof Der is " << sizeof ob;
  54. 	cout << "\nDer::i is at offset " << off_i;
  55. 	cout << "\nDer::l is at offset " << off_l;
  56. 	cout << "\nDer::T is at offset " << off_T;
  57. 	cout << "\nDer::U is at offset " << off_U;
  58.  
  59. 	string layout (sizeof ob, '*');
  60. 	layout.replace (off_T, sizeof(T), sizeof (T), 'T');
  61. 	layout.replace (off_U, sizeof(U), sizeof (U), 'U');
  62. 	layout.replace (off_i, sizeof ob.i, sizeof ob.i, 'i');
  63. 	layout.replace (off_l, sizeof ob.l, sizeof ob.l, 'l');
  64. 	cout << "\nlayout of Der is \n" << layout << "\n";
  65. }
  66.  
  67. struct Der2 : virtual T, U{ 
  68. };
  69.  
  70. void displayDer2() {
  71. 	Der2 ob;
  72. 	T &t = ob;
  73. 	U &u = ob;
  74. 	char *base = (char*)&ob;
  75. 	int off_i = (char*)&ob.i - base;
  76. 	int off_l = (char*)&ob.l - base;
  77. 	int off_T = (char*)&t - base;
  78. 	int off_U = (char*)&u - base;
  79.  
  80. 	cout << "sizeof Der2 is " << sizeof ob;
  81. 	cout << "\nDer2::i is at offset " << off_i;
  82. 	cout << "\nDer2::l is at offset " << off_l;
  83. 	cout << "\nDer2::T is at offset " << off_T;
  84. 	cout << "\nDer2::U is at offset " << off_U;
  85.  
  86. 	string layout (sizeof ob, '*');
  87. 	layout.replace (off_T, sizeof(T), sizeof (T), 'T');
  88. 	layout.replace (off_U, sizeof(U), sizeof (U), 'U');
  89. 	layout.replace (off_i, sizeof ob.i, sizeof ob.i, 'i');
  90. 	layout.replace (off_l, sizeof ob.l, sizeof ob.l, 'l');
  91. 	cout << "\nlayout of Der2 is \n" << layout << "\n";
  92. }
  93.  
  94. struct Der3 : virtual T, virtual U{ 
  95. };
  96.  
  97. void displayDer3() {
  98. 	Der3 ob;
  99. 	T &t = ob;
  100. 	U &u = ob;
  101. 	char *base = (char*)&ob;
  102. 	int off_i = (char*)&ob.i - base;
  103. 	int off_l = (char*)&ob.l - base;
  104. 	int off_T = (char*)&t - base;
  105. 	int off_U = (char*)&u - base;
  106.  
  107. 	cout << "sizeof Der3 is " << sizeof ob;
  108. 	cout << "\nDer3::i is at offset " << off_i;
  109. 	cout << "\nDer3::l is at offset " << off_l;
  110. 	cout << "\nDer3::T is at offset " << off_T;
  111. 	cout << "\nDer3::U is at offset " << off_U;
  112.  
  113. 	string layout (sizeof ob, '*');
  114. 	layout.replace (off_T, sizeof(T), sizeof (T), 'T');
  115. 	layout.replace (off_U, sizeof(U), sizeof (U), 'U');
  116. 	layout.replace (off_i, sizeof ob.i, sizeof ob.i, 'i');
  117. 	layout.replace (off_l, sizeof ob.l, sizeof ob.l, 'l');
  118. 	cout << "\nlayout of Der3 is \n" << layout << "\n";
  119. }
  120.  
  121. int main() {
  122. 	cout << "sizeof void* is " << sizeof(void*) << "\n";
  123. 	displayT();
  124. 	displayU();
  125. 	displayDer();
  126. 	displayDer2();
  127. 	displayDer3();
  128. 	return 0;
  129. }
  130.  
Success #stdin #stdout 0s 3460KB
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stdin
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Standard input is empty
stdout
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sizeof void* is 4
sizeof T is 8
sizeof i is 4
i is at offset 4
layout of T is 
****iiii
sizeof U is 12
sizeof U::l is 8
l is at offset 4
layout of U is 
****llllllll
sizeof Der is 20
Der::i is at offset 4
Der::l is at offset 12
Der::T is at offset 0
Der::U is at offset 8
layout of Der is 
TTTTiiiiUUUUllllllll
sizeof Der2 is 20
Der2::i is at offset 16
Der2::l is at offset 4
Der2::T is at offset 12
Der2::U is at offset 0
layout of Der2 is 
UUUUllllllllTTTTiiii
sizeof Der3 is 24
Der3::i is at offset 8
Der3::l is at offset 16
Der3::T is at offset 4
Der3::U is at offset 12
layout of Der3 is 
****TTTTiiiiUUUUllllllll
https://ideone.com/g5SZwk
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
public

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