6

在下面的示例中，如何正确调用 ~CImpl 但是当需要移动类时，编译器说它的类型不完整？

如果将 Impl 的声明移到它工作的标头中，我的问题是为什么析构函数被调用得很好，所以看起来类型不完整，但是移动时出现了问题。

文件：C.hpp

#include <memory>

class Impl;


class C
{
public:
    C();
    ~C();

    C(C&&) = default;
    C& operator=(C&&) = default;

    std::unique_ptr<Impl> p;
};

文件 C.cpp

#include "C.hpp"
#include <iostream>

using namespace std;

class Impl
{
public:
    Impl() {}
    virtual ~Impl() = default;
    virtual void f() = 0;
};

class CImpl: public Impl
{
public:
    ~CImpl()
    {
        cout << "~CImpl()" << endl;
    }
    void f()
    {
        cout << "f()" << endl;
    }

};


C::C():
    p(new CImpl())
{}

C::~C()

文件：main.cpp

#include <iostream>
#include <vector>
#include "C.hpp"
using namespace std;
int main(int argc, char *argv[])
{
    vector<C> vc;
    // this won't compile
    //vc.emplace_back(C());
    C c;
    C c2 = move(c); // this won't compile
}

编译器输出：

+ clang++ -std=c++11 -Wall -c C.cpp
+ clang++ -std=c++11 -Wall -c main.cpp
In file included from main.cpp:3:
In file included from ./C.hpp:1:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/memory:80:
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unique_ptr.h:65:16: error: invalid application of 'sizeof' to an incomplete type 'Impl'
        static_assert(sizeof(_Tp)>0,
                      ^~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unique_ptr.h:184:4: note: in instantiation of member function
      'std::default_delete<Impl>::operator()' requested here
          get_deleter()(__ptr);
          ^
./C.hpp:12:5: note: in instantiation of member function 'std::unique_ptr<Impl, std::default_delete<Impl> >::~unique_ptr' requested here
    C(C&&) = default;
    ^
./C.hpp:3:7: note: forward declaration of 'Impl'
class Impl;
      ^
1 error generated.
4

1 回答 1

4

您的析构函数工作正常，因为析构函数的（空）主体位于 C 源文件中，可以访问Impl. 然而，移动构造函数和移动赋值在标头中默认（定义），没有定义Impl.

你可以做的是C(C&&);在头文件和C::C(C&&) = default;源文件中。

于 2014-02-26T17:12:19.190 回答