我有这段代码
#include <iostream>
#include <vector>
using namespace std;
class ArrayWrapper {
private:
int *_p_vals;
int _size;
public:
//default constructor
ArrayWrapper () : _p_vals( new int[ 64 ] ) , _size( 64 ) {
cout << "default constructor called\n";
}
//constructor 2
ArrayWrapper (int n) : _p_vals( new int[ n ] ) , _size( n ) {
cout << "constructor 2 called\n";
}
//move constructor
ArrayWrapper (ArrayWrapper&& other) : _p_vals(other._p_vals), _size(other._size) {
cout << "move constructor called\n";
other._p_vals = nullptr;
other._size = 0;
}
// copy constructor
ArrayWrapper (const ArrayWrapper& other) : _p_vals( new int[ other._size ] ) , _size( other._size ) {
cout << "copy constructor called\n";
for ( int i = 0; i < _size; ++i )
_p_vals[i] = other._p_vals[i];
}
~ArrayWrapper () {
delete [] _p_vals;
}
void set_val (std::initializer_list <int> vals) {
int i = 0;
for (auto val : vals) {
_p_vals[i] = val;
i++;
}
}
void print_val () const {
for (auto i = 0; i < _size ; i++){
cout <<_p_vals[i] << ":" ;
}
cout << endl;
}
};
ArrayWrapper getArrayWrapper () {
ArrayWrapper A(5);
A.set_val({1,2,3,4,5});
return A;
}
int main () {
ArrayWrapper arr {getArrayWrapper()};
arr.print_val();
return 0;
}
我正在尝试确保调用移动构造函数。但是正在使用一些默认的复制构造函数,因为输出只是这个
constructor 2 called
1:2:3:4:5:
我正在使用以下g ++版本
g++ (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406
我应该进行所有构造函数调用explicit
。我想知道这会有什么帮助。有没有办法可以强制程序调用我上面写的移动构造函数和复制构造函数?
答案 0 :(得分:0)
感谢评论者,我发现编译器正在进行返回值优化(RVO),这会阻止对上面编写的构造函数的调用。我找到了一种禁用RVO的方法。 g ++中的-fno-elide-constructors
开关有效。