| 1 | //We need to declare: |
|---|---|
| 2 | // |
| 3 | //2 conversions: rv<T> & and const rv<T> & |
| 4 | //1 rv<T> & constructor: move constructor |
| 5 | //1 const rv<T> & constructor: copy constructor |
| 6 | //1 T & constructor: copy constructor |
| 7 | // |
| 8 | //Optimization: |
| 9 | //Since RVO is better than move-construction, |
| 10 | //avoid copy constructor overloading. |
| 11 | |
| 12 | #include <boost/move/utility_core.hpp> |
| 13 | #include <iostream> |
| 14 | |
| 15 | bool moved = false; |
| 16 | |
| 17 | class obj |
| 18 | { |
| 19 | BOOST_COPYABLE_AND_MOVABLE(obj) |
| 20 | public: |
| 21 | |
| 22 | obj() |
| 23 | { |
| 24 | std::cout << "constructing obj"<< "\n"; |
| 25 | } |
| 26 | |
| 27 | ~obj() |
| 28 | {} |
| 29 | |
| 30 | obj(const obj &) |
| 31 | { |
| 32 | std::cout << "copy construct from const obj"<< "\n"; |
| 33 | } |
| 34 | |
| 35 | // copy construct from movable object (non-const rvalue, explicitly moved lvalue) |
| 36 | obj(BOOST_RV_REF(obj)) |
| 37 | { |
| 38 | std::cout << "move construct from movable rvalue"<< "\n"; |
| 39 | } |
| 40 | |
| 41 | obj& operator =(BOOST_COPY_ASSIGN_REF(obj)) |
| 42 | { |
| 43 | std::cout << "copy assign from const obj"<< "\n"; |
| 44 | return *this; |
| 45 | } |
| 46 | |
| 47 | obj& operator =(BOOST_RV_REF(obj)) |
| 48 | { |
| 49 | std::cout << "move assign from movable rvalue"<< "\n"; |
| 50 | return *this; |
| 51 | } |
| 52 | }; |
| 53 | |
| 54 | |
| 55 | obj rvalue_func() { return obj(); } |
| 56 | const obj const_rvalue_func() { return obj(); } |
| 57 | obj& lvalue_func() { static obj o; return o; } |
| 58 | const obj& const_lvalue_func() { static obj o; return o; } |
| 59 | |
| 60 | obj produce() { return obj(); } |
| 61 | |
| 62 | void consume(obj){} |
| 63 | |
| 64 | int main() |
| 65 | { |
| 66 | { consume(produce()); } |
| 67 | { obj o = produce(); } |
| 68 | { obj o(produce()); } |
| 69 | { |
| 70 | obj o1(rvalue_func()); |
| 71 | obj o2 = const_rvalue_func(); |
| 72 | obj o3 = lvalue_func(); |
| 73 | obj o4 = const_lvalue_func(); |
| 74 | // can't explicitly move temporaries |
| 75 | //obj o5 = boost::move(rvalue_func()); |
| 76 | obj o5; |
| 77 | //Maybe missed optimization: copied |
| 78 | o5 = rvalue_func(); |
| 79 | //Explicit forward works OK and optimized |
| 80 | o5 = boost::forward<obj>(t: rvalue_func()); |
| 81 | |
| 82 | obj o7 = boost::move(t&: lvalue_func()); |
| 83 | obj o8 = boost::move(t: const_lvalue_func()); |
| 84 | |
| 85 | obj o; |
| 86 | o = rvalue_func(); |
| 87 | o = const_rvalue_func(); |
| 88 | o = lvalue_func(); |
| 89 | o = const_lvalue_func(); |
| 90 | // can't explicitly move temporaries |
| 91 | //o = boost::move(rvalue_func()); |
| 92 | o = boost::forward<obj>(t: rvalue_func()); |
| 93 | o = boost::move(t: const_rvalue_func()); |
| 94 | o = boost::move(t&: lvalue_func()); |
| 95 | o = boost::move(t: const_lvalue_func()); |
| 96 | } |
| 97 | return 0; |
| 98 | } |
| 99 | |
| 100 | //We need to declare: |
| 101 | // |
| 102 | //2 conversions: rv<T> & and const rv<T> & |
| 103 | //1 rv<T> & constructor: move constructor |
| 104 | //1 const rv<T> & constructor: copy constructor |
| 105 | //1 T & constructor: copy constructor |
| 106 |