没有按预期调用复制构造函数(No call to copy constructor as expected)

没有按预期调用复制构造函数(No call to copy constructor as expected)

我有一些像这样的代码：

int a = 5; Foo *foo = new Foo(MoreFoo(a), Bar(a)); // Foo CTOR: Foo(MoreFoo mf, Bar bar): MoreBar(&mf,bar){}

我的编译器给了我一个类型的错误：

no matching function for call to ‘Bar::Bar(Bar)’ note: candidates are: note: Bar::Bar(Bar&) no known conversion for argument 1 from ‘Bar’ to ‘Bar&’

该错误显然与代码Bar(a) 。 Bar显然有适当的CTOR和CCTOR。 我理解为什么编译器抱怨尝试调用类似Bar::Bar(Bar) ，我正在创建一个无名变量（ Bar(a) ），它必须在调用Foo构造函数时被复制，但后来不应该'它只是调用Bar CCTOR？ 为什么我收到错误？

编辑：

你为什么要调用Bar::Bar(Bar)而不是Bar::Bar(Bar&) ？

I have some code like this:

int a = 5; Foo *foo = new Foo(MoreFoo(a), Bar(a)); // Foo CTOR: Foo(MoreFoo mf, Bar bar): MoreBar(&mf,bar){}

My compiler gives me an error of type:

no matching function for call to ‘Bar::Bar(Bar)’ note: candidates are: note: Bar::Bar(Bar&) no known conversion for argument 1 from ‘Bar’ to ‘Bar&’

The error obviously relates to the code Bar(a). Obviously Bar has appropriate CTOR and CCTOR. I understand why the compiler complains about trying to invoke something like Bar::Bar(Bar), I'm creating a nameless variable (Bar(a)) which has to be copied during the call to the Foo constructor, but then shouldn’t it just invoke Bar CCTOR? Why am I getting the error?

Edit:

Why would you ever want to invoke Bar::Bar(Bar) instead of Bar::Bar(Bar&)?

最满意答案

Temporaries不能绑定到引用，除非它们是const -references。

Temporaries cannot be bound to references unless they are references-to-const.