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  1.  
  2. #include <iostream>
  3. struct Dim;
  4. struct Group;
  5.  
  6. struct Cross {
  7. 	int i;
  8. 	Cross(int l) :i(l) { std::cout << "Cross() = " << (uint64_t)this << std::endl; }
  9. 	Dim dim();
  10. };
  11.  
  12. struct Dim {
  13. 	Cross * ptr;
  14. 	explicit  Dim(Cross * c) :ptr(c) {
  15. 		std::cout << "Dim(Cross*) = " << (uint64_t)this << " : " << (uint64_t)ptr << std::endl;
  16. 	}
  17. 	Dim(Dim && d) :ptr(d.ptr) {
  18. 		std::cout << "Dim(&&) = " << (uint64_t)this << " : " << (uint64_t)ptr << std::endl;
  19. 	}
  20. 	~Dim() {
  21. 		std::cout << "~Dim() = " << (uint64_t)this << std::endl;
  22. 	}
  23. 	Group group();
  24. };
  25.  
  26. struct Group {
  27. 	Dim * ptr;
  28. 	explicit Group(Dim * c) :ptr(c) {
  29. 		std::cout << "Group(Dim*) = " << (uint64_t)this << " : " << (uint64_t)ptr << std::endl;
  30. 	}
  31. 	Group(Group && d) :ptr(d.ptr) {
  32. 		std::cout << "Group(&&) = " << (uint64_t)this << " : " << (uint64_t)ptr << std::endl;
  33. 	}
  34.  
  35. };
  36.  
  37. Dim Cross::dim() {
  38. 	Dim d(this);
  39. 	return d;
  40. }
  41.  
  42. Group Dim::group() {
  43. 	std::cout << "Dim::group = " << (uint64_t)this << std::endl;
  44. 	Group g(this);
  45. 	return g;
  46. }
  47.  
  48. template<typename D>
  49. struct Op {
  50. 	D g;
  51. 	Op(Op && o) :g(std::move(o.g)) {
  52. 		std::cout << "Op(&&) = " << (uint64_t)this << " : " << (uint64_t)g.ptr << std::endl;
  53. 	}
  54. 	Op(D && gg) :g(std::move(gg)) {
  55. 		std::cout << "Op(D&&) = " << (uint64_t)this << " : " << (uint64_t)g.ptr << std::endl;
  56. 	}
  57. };
  58.  
  59. template<typename D>
  60. struct Cons {
  61. 	D op;
  62. 	Cons(Cons && c) :op(std::move(c.op)) {
  63. 		std::cout << "Cons(&&) = " << (uint64_t)this << " : " << (uint64_t)op.g.ptr << std::endl;
  64. 	}
  65. 	explicit  Cons(D && gg) :op(std::move(gg)) {
  66. 		std::cout << "Cons(Op&&) = " << (uint64_t)this << " : " << (uint64_t)op.g.ptr << std::endl;
  67. 	}
  68. };
  69.  
  70. template<typename D>
  71. decltype(auto) make_consumer1(D &&d) {
  72. 	auto op = Op<decltype(d)>(std::move(d));
  73. 	return Cons<decltype(op)>(std::move(op));
  74. }
  75. template<typename G>
  76. decltype(auto) make_consumer2(G && g) { // <---------если здесь передавать аргумент по значению, то проблема исчезает.
  77. 	auto gop = Op<decltype(g)>(std::move(g));
  78. 	return Cons<decltype(gop)>(std::move(gop));
  79. }
  80.  
  81.  
  82. int main() {
  83. 	Cross c(10);
  84. 	auto cons1 = make_consumer1(c.dim());
  85. 	std::cout << "cons1 " << cons1.op.g.ptr->i << std::endl;
  86. 	auto cons2 = make_consumer2(cons1.op.g.group());
  87. 	std::cout << cons2.op.g.ptr->ptr->i << std::endl; // <------------ ERROR: должно напечатать 10, а печатает мусор
  88. 	return 0;
  89. }
  90.  
Success #stdin #stdout 0s 15240KB
comments (?)
stdin 
Standard input is empty
stdout 
Cross() = 140727019914912
Dim(Cross*) = 140727019914960 : 140727019914912
Op(D&&) = 140727019914976 : 140727019914912
Op(&&) = 140727019914928 : 140727019914912
Cons(Op&&) = 140727019914928 : 140727019914912
~Dim() = 140727019914960
cons1 10
Dim::group = 140727019914960
Group(Dim*) = 140727019914960 : 140727019914960
Op(D&&) = 140727019914976 : 140727019914960
Op(&&) = 140727019914944 : 140727019914960
Cons(Op&&) = 140727019914944 : 140727019914960
-1878505776
https://ideone.com/cdHChZ
language:
C++ (gcc 8.3)
created:
5 years ago
visibility:
public

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