1 // Copyright David Abrahams 2009. Distributed under the Boost
2 // Software License, Version 1.0. (See accompanying
3 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
4
5 #include <boost/move/detail/config_begin.hpp>
6 #include <iostream>
7 #include <boost/core/lightweight_test.hpp>
8
9 #ifdef NO_MOVE
10 # undef BOOST_COPY_ASSIGN_REF
11 # define BOOST_COPY_ASSIGN_REF(X) X const&
12 # undef BOOST_COPYABLE_AND_MOVABLE
13 # define BOOST_COPYABLE_AND_MOVABLE(X)
14 # define MOVE(x) (x)
15 #else
16 #include <boost/move/utility_core.hpp>
17 # define MOVE(x) boost::move(x)
18 #endif
19
20 struct X
21 {
XX22 X() : id(instances++)
23 {
24 std::cout << "X" << id << ": construct\n";
25 }
26
XX27 X(X const& rhs) : id(instances++)
28 {
29 std::cout << "X" << id << ": <- " << "X" << rhs.id << ": **copy**\n";
30 ++copies;
31 }
32
33 // This particular test doesn't exercise assignment, but for
34 // completeness:
operator =X35 X& operator=(BOOST_COPY_ASSIGN_REF(X) rhs)
36 {
37 std::cout << "X" << id << ": <- " << "X" << rhs.id << ": assign\n";
38 return *this;
39 }
40
41 #ifndef NO_MOVE
operator =X42 X& operator=(BOOST_RV_REF(X) rhs)
43 {
44 std::cout << "X" << id << ": <- " << "X" << rhs.id << ": move assign\n";
45 return *this;
46 }
47
XX48 X(BOOST_RV_REF(X) rhs) : id(instances++)
49 {
50 std::cout << "X" << id << ": <- " << "X" << rhs.id << ": ..move construct..\n";
51 ++copies;
52 }
53 #endif
54
~XX55 ~X() { std::cout << "X" << id << ": destroy\n"; }
56
57 unsigned id;
58
59 static unsigned copies;
60 static unsigned instances;
61
62 BOOST_COPYABLE_AND_MOVABLE(X)
63 };
64
65 unsigned X::copies = 0;
66 unsigned X::instances = 0;
67
68 #define CHECK_COPIES( stmt, min, max, comment ) \
69 { \
70 unsigned const old_copies = X::copies; \
71 \
72 std::cout << "\n" comment "\n" #stmt "\n===========\n"; \
73 { \
74 stmt; \
75 } \
76 unsigned const n = X::copies - old_copies; \
77 volatile unsigned const minv(min), maxv(max); \
78 BOOST_TEST(n <= maxv); \
79 if (n > maxv) \
80 std::cout << "*** max is too low or compiler is buggy ***\n"; \
81 BOOST_TEST(n >= minv); \
82 if (n < minv) \
83 std::cout << "*** min is too high or compiler is buggy ***\n"; \
84 \
85 std::cout << "-----------\n" \
86 << n << "/" << max \
87 << " possible copies/moves made\n" \
88 << max - n << "/" << max - min \
89 << " possible elisions performed\n\n"; \
90 \
91 if (n > minv) \
92 std::cout << "*** " << n - min \
93 << " possible elisions missed! ***\n"; \
94 }
95
96 struct trace
97 {
tracetrace98 trace(char const* name)
99 : m_name(name)
100 {
101 std::cout << "->: " << m_name << "\n";
102 }
103
~tracetrace104 ~trace()
105 {
106 std::cout << "<-: " << m_name << "\n";
107 }
108
109 char const* m_name;
110 };
111
sink(X)112 void sink(X)
113 {
114 trace t("sink");
115 }
116
nrvo_source()117 X nrvo_source()
118 {
119 trace t("nrvo_source");
120 X a;
121 return a;
122 }
123
urvo_source()124 X urvo_source()
125 {
126 trace t("urvo_source");
127 return X();
128 }
129
identity(X a)130 X identity(X a)
131 {
132 trace t("identity");
133 return a;
134 }
135
136 X lvalue_;
lvalue()137 X& lvalue()
138 {
139 return lvalue_;
140 }
141 typedef X rvalue;
142
ternary(bool y)143 X ternary( bool y )
144 {
145 X a, b;
146 return MOVE(y?a:b);
147 }
148
main(int argc,char * argv[])149 int main(int argc, char* argv[])
150 {
151 (void)argv;
152 // Double parens prevent "most vexing parse"
153 CHECK_COPIES( X a(( lvalue() )), 1U, 1U, "Direct initialization from lvalue");
154 CHECK_COPIES( X a(( rvalue() )), 0U, 1U, "Direct initialization from rvalue");
155
156 CHECK_COPIES( X a = lvalue(), 1U, 1U, "Copy initialization from lvalue" );
157 CHECK_COPIES( X a = rvalue(), 0U, 1U, "Copy initialization from rvalue" );
158
159 CHECK_COPIES( sink( lvalue() ), 1U, 1U, "Pass lvalue by value" );
160 CHECK_COPIES( sink( rvalue() ), 0U, 1U, "Pass rvalue by value" );
161
162 CHECK_COPIES( nrvo_source(), 0U, 1U, "Named return value optimization (NRVO)" );
163 CHECK_COPIES( urvo_source(), 0U, 1U, "Unnamed return value optimization (URVO)" );
164
165 // Just to prove these things compose properly
166 CHECK_COPIES( X a(urvo_source()), 0U, 2U, "Return value used as ctor arg" );
167
168 // Expect to miss one possible elision here
169 CHECK_COPIES( identity( rvalue() ), 0U, 2U, "Return rvalue passed by value" );
170
171 // Expect to miss an elision in at least one of the following lines
172 CHECK_COPIES( X a = ternary( argc == 1000 ), 0U, 2U, "Return result of ternary operation" );
173 CHECK_COPIES( X a = ternary( argc != 1000 ), 0U, 2U, "Return result of ternary operation again" );
174 return boost::report_errors();
175 }
176
177 #include <boost/move/detail/config_end.hpp>
178