fork download
copy 
  1. #include <iostream>
  2. using namespace std;
  3.  
  4. struct A {
  5.     std::string s;
  6.     A(const std::string& s) : s(s) {}
  7.     A(const A& o) : s(o.s) { std::cout << "move failed!\n"; }
  8.     A(A&& o) : s(std::move(o.s)) {}
  9.     A& operator=(const A&) { std::cout << "copy assigned\n"; return *this; }
  10.     A& operator=(A&& other) {
  11.         std::cout << s << " " << other.s << endl;
  12.         s = std::move(other.s);
  13.         std::cout << "move assigned\n";
  14.         std::cout << s << " " << other.s << endl;
  15.         return *this;
  16.     }
  17. };
  18.  
  19. A f(A a) { return a; }
  20.  
  21. struct B : A {
  22. 	B(const std::string& s) : A(s) { }
  23.     std::string s2;
  24.     int n;
  25.     // implicit move assignment operator B& B::operator=(B&&)
  26.     // calls A's move assignment operator
  27.     // calls s2's move assignment operator
  28.     // and makes a bitwise copy of n
  29. };
  30.  
  31. int main()
  32. {
  33.     A a1("foo"), a2("bar");
  34.     std::cout << "Trying to move-assign A from rvalue temporary\n";
  35.     a1 = f(A("asda")); // move-assignment from rvalue temporary
  36.     std::cout << "Trying to move-assign A from xvalue\n";
  37.     a2 = std::move(a1); // move-assignment from xvalue
  38.  
  39.     std::cout << "Trying to move-assign B\n";
  40.     B b1("foo"), b2("bar");
  41.     std::cout << "Before move, b1.s = \"" << b1.s << "\"\n";
  42.     b2 = std::move(b1); // calls implicit move assignment
  43.     std::cout << "After move, b1.s = \"" << b1.s << "\"\n";
  44. }
Success #stdin #stdout 0s 3232KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Trying to move-assign A from rvalue temporary
foo asda
move assigned
asda foo
Trying to move-assign A from xvalue
bar asda
move assigned
asda bar
Trying to move-assign B
Before move, b1.s = "foo"
bar foo
move assigned
foo bar
After move, b1.s = "bar"
https://ideone.com/cY9w2X
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!