c++ - 自动转换错误

Question

class Sample
{
public:
  Sample();
  Sample(int i);
  Sample(Sample& s);
  ~Sample();
};

Sample::Sample()
{
  cout<<"Default constructor called\n";
}

Sample::Sample(int i)
{
  cout<<"1-argument constructor called\n";
}

Sample::Sample(Sample& s)
{
  cout<<"Copy constructor called\n";
}

Sample::~Sample()
{
  cout<<"Destructor called\n";
}

void Fun(Sample s)
{

}

int main()
{
  Sample s1;
  Fun(5);

  return 0;
}

我期望隐式转换为 5。但是，当我编译上面的代码时，我收到以下错误：

main.cpp:7:8: error: no matching function for call to ‘Sample::Sample(Sample)’
main.cpp:7:8: note: candidates are:
Sample.h:10:3: note: Sample::Sample(Sample&)
Sample.h:10:3: note:   no known conversion for argument 1 from ‘Sample’ to ‘Sample&’
Sample.h:9:3: note: Sample::Sample(int)
Sample.h:9:3: note:   no known conversion for argument 1 from ‘Sample’ to ‘int’
Sample.h:8:3: note: Sample::Sample()
Sample.h:8:3: note:   candidate expects 0 arguments, 1 provided
Helper.h:6:13: error:   initializing argument 1 of ‘void Fun(Sample)’

问题是什么？当我删除复制构造函数时，上面的代码编译成功。

提前致谢。

Answer 1

临时对象不能绑定到非常量引用。您的复制构造函数应该是：

Sample::Sample(const Sample&)

删除它会告诉编译器生成一个普通的，它将具有上述签名。