I have the following program:
#include <vector>
#include <cassert>
class NoCopy {
public:
explicit NoCopy(int d) : data(d) {}
[[noreturn]] NoCopy(const NoCopy& other) : data(other.data) {
assert(false); // Attempted to copy
}
[[noreturn]] NoCopy& operator=(const NoCopy& other) {
assert(false); // Attempted to copy
}
NoCopy(NoCopy&& other) {
assert(!other._movedFrom); // NoCopy should not have been moved from twice
other._movedFrom = true;
data = other.data;
}
NoCopy& operator=(NoCopy&& other) {
assert(!other._movedFrom); // NoCopy should not have been moved from twice
other._movedFrom = true;
data = other.data;
return *this;
}
// Just some data so that we can assert on it's contents.
int data;
private:
bool _movedFrom = false;
};
int main() {
std::vector<NoCopy> v3;
v3.reserve(3);
v3.emplace_back(6);
v3.emplace_back(7);
v3.emplace_back(8);
std::vector<NoCopy> v4;
std::move(v3.begin(), v3.end(), std::back_inserter(v4));
assert(v4[0].data == 6);
assert(v4[1].data == 7);
assert(v4[2].data == 8);
return 0;
}
I would expect the std::move line to call the move constructor of the instances of NoCopy, but instead the program asserts on line 9 (copy constructor). What am I doing wrong?
