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  1. #include <iostream>
  2.  
  3. struct X
  4. {
  5.     X() : id(instances++)
  6.     {
  7.         std::cout << "X" << id << ": construct\n";
  8.     }
  9.  
  10.     X(X const& rhs) : id(instances++)
  11.     {
  12.         std::cout << "X" << id << ": <- " << "X" << rhs.id << ": **copy**\n";
  13.         ++copies;
  14.     }
  15.  
  16.     X(X&& rhs) : id(instances++)
  17.     {
  18.         std::cout << "X" << id << ": <- " << "X" << rhs.id << ": **move**\n";
  19.         ++moves;
  20.     }
  21.  
  22.     // This particular test doesn't exercise assignment, but for
  23.     // completeness:
  24.     X& operator=(X const& rhs)
  25.     {
  26.         std::cout << "X" << id << ": <- " << "X" << rhs.id << ": copy-assign\n";
  27.     }
  28.  
  29.     X& operator=(X&& rhs)
  30.     {
  31.         std::cout << "X" << id << ": <- " << "X" << rhs.id << ": move-assign\n";
  32.     }
  33.  
  34.     ~X() { std::cout << "X" << id << ": destroy\n"; }
  35.  
  36.     X& operator+=( const X& rhs ) {
  37.         std::cout << "X" << id << ": += " << "X" << rhs.id << ": add-assign\n";
  38.         return *this;
  39.     }
  40.  
  41.     unsigned id;
  42.  
  43.     static unsigned copies;
  44.     static unsigned moves;
  45.     static unsigned instances;
  46. };
  47.  
  48. X operator+( X lhs, const X& rhs ) {
  49.     std::cout << "X" << lhs.id << ": +  " << "X" << rhs.id << ": add\n";
  50.     lhs += rhs;
  51.     return lhs;
  52. }
  53.  
  54. unsigned X::copies    = 0;
  55. unsigned X::moves     = 0;
  56. unsigned X::instances = 0;
  57.  
  58. #define CHECK_COPIES( stmt, min, max_copies, max_moves, comment )           \
  59. {                                                                           \
  60.     unsigned const old_copies = X::copies;                                  \
  61.     unsigned const old_moves  = X::moves;                                   \
  62.                                                                             \
  63.     std::cout << "\n" comment "\n" #stmt "\n===========\n";                 \
  64.     {                                                                       \
  65.         stmt;                                                               \
  66.     }                                                                       \
  67.     unsigned const n = X::copies - old_copies;                              \
  68.     unsigned const m = X::moves  - old_moves;                               \
  69.     unsigned const t = n+m;                                                 \
  70.     if (t < min)                                                            \
  71.         std::cout << "*** min is too high or compiler is buggy ***\n";      \
  72.     if (n > max_copies)                                                     \
  73.         std::cout << "*** max_copies is too low or compiler is buggy ***\n";\
  74.     if (m > max_moves)                                                      \
  75.         std::cout << "*** max_moves is too low or compiler is buggy ***\n"; \
  76.                                                                             \
  77.                                                                             \
  78.     std::cout << "-----------\n"                                            \
  79.               << n << "/" << max_copies                                     \
  80.               << " possible copies made\n"                                  \
  81.               << m << "/" << max_moves                                      \
  82.               << " possible moves made\n"                                   \
  83.               << max_copies - t << "/" << max_copies - min                  \
  84.               << " possible elisions performed\n\n";                        \
  85.                                                                             \
  86.     if (t > min)                                                            \
  87.         std::cout << "*** " << t - min                                      \
  88.                   << " possible elisions missed! ***\n";                    \
  89. }
  90.  
  91. X lvalue_;
  92. X& lvalue()
  93. {
  94.     return lvalue_;
  95. }
  96. typedef X rvalue;
  97.  
  98. int main()
  99. {
  100.     CHECK_COPIES( lvalue() + lvalue(), 1, 2, 1, "lvalue + lvalue" );
  101.     CHECK_COPIES( rvalue() + lvalue(), 0, 2, 2, "rvalue + lvalue" );
  102.     CHECK_COPIES( lvalue() + rvalue(), 1, 2, 1, "lvalue + rvalue" );
  103. }
Success #stdin #stdout 0s 2856KB
comments (?)
stdin
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Standard input is empty
stdout
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X0: construct

lvalue + lvalue
lvalue() + lvalue()
===========
X1: <- X0: **copy**
X1: +  X0: add
X1: += X0: add-assign
X2: <- X1: **move**
X2: destroy
X1: destroy
-----------
1/2 possible copies made
1/1 possible moves made
0/1 possible elisions performed

*** 1 possible elisions missed! ***

rvalue + lvalue
rvalue() + lvalue()
===========
X3: construct
X3: +  X0: add
X3: += X0: add-assign
X4: <- X3: **move**
X4: destroy
X3: destroy
-----------
0/2 possible copies made
1/2 possible moves made
1/2 possible elisions performed

*** 1 possible elisions missed! ***

lvalue + rvalue
lvalue() + rvalue()
===========
X5: construct
X6: <- X0: **copy**
X6: +  X5: add
X6: += X5: add-assign
X7: <- X6: **move**
X7: destroy
X6: destroy
X5: destroy
-----------
1/2 possible copies made
1/1 possible moves made
0/1 possible elisions performed

*** 1 possible elisions missed! ***
X0: destroy
https://ideone.com/q1ETx3
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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