为什么MVS编译器可以将参数'myStruct'转换为'myStruct&'。并没有文件错误C2664：不能将'myStruct'转换为'myStruct& [英] Why the MVS compiler can convert argument 'myStruct' to 'myStruct &'. And did not file error C2664: cannot convert 'myStruct' to 'myStruct &'

问题描述

我有一个类，其中我使用 std :: mem_fn 来选择辅助函数。

I have a class where I use std::mem_fn to choose between helper functions.

1. 为什么我的代码被编译和运行如果我在 m_funcContainer 减少了& 在代码& 中注释掉 / ** / myStruct / *& /

1. Why my code get compiled and run If I am missing & in m_funcContainer deceleration ? In the code & commented out with /**/ myStruct/*&*/

std :: map< std :: string，std :: function< void（const myClass *，myStruct / *& * /）> m_funcContainer

（但是 m_funcContainerInt p>

(but in case of m_funcContainerInt the compiler rise compile error)

错误C2664：'void（int&）const'：不能将参数1从
'int'转换为'int& '

error C2664: 'void (int &) const' : cannot convert argument 1 from 'int' to 'int &'

1. 我觉得我没有在最好的方法，你能帮我制定技术上更正确的标题吗？

为什么编译器可以转换在
中的参数'myStruct'到'myStruct&'std :: function

Why the compiler can convert argument 'myStruct' to 'myStruct &' in std::function

我的简化代码是

myClass.h

#include <memory>
#include <map>
#include <functional>

struct ExtraFlag
{
};

struct Flag
{
};

struct myStruct
{
    std::shared_ptr<ExtraFlag>         extraFlag;
    std::shared_ptr<Flag>              flag;

    explicit myStruct()
    {
    }
};

class myClass
{
private:
    std::map < std::string, std::function<void(const myClass*, myStruct/*&*/) >> m_funcContainer;
    std::map < std::string, std::function<void(const myClass*, int/*&*/) >> m_funcContainerInt;

private:
    void funcMyStruct(myStruct& arg1) const;
    void funcInt(int& arg1) const;
public:
    myClass();
};

myClass.cpp

#include "myClass.h"
myClass::myClass()
{
    m_funcContainer["func"] = std::mem_fn(&myClass::funcMyStruct);
    myStruct myStructInstance;
    m_funcContainer.at("func")(this, myStructInstance);

    int a;
    m_funcContainerInt["func"] = std::mem_fn(&myClass::funcInt);
    m_funcContainerInt.at("func")(this, a);
}
void myClass::funcMyStruct(myStruct& arg1) const
{}

void myClass::funcInt(int& arg1) const
{}

已编辑我正在编译Microsoft Visual Studio 2013

EDITED I am compiling on Microsoft visual studio 2013

推荐答案

您的问题是MSVC2013不是一个C ++编译器的默认设置。它编译与C ++密切相关的语言，但是具有扩展。

Your problem is that MSVC2013 is not a C++ compiler under its default settings. It is compiles a language closely related to C++, but with "extensions". You are being bitten by one of them.

/ Za 会关闭（大多数）语言扩充功能

/Za will turn off (most?) language extensions, I believe including the one causing you a problem here.

我听说过有些MSVC（系统标题）附带的标题可能会有的问题， / Za 。并且，使用 / Za 关闭编译和测试的代码可能会在打开 / Za 时发生意外的行为更改。我会默认在新文件或项目中包含它，如果您有一个旧项目激活它并测试，它不会导致问题。

I have heard reports that some headers that ship with MSVC (system headers) can have problems with /Za. And, code that was compiled and tested with /Za off could have unexpected behavior changes with /Za turned on. I would include it by default in new files or projects, and if you have an old project activate it and test that it doesn't cause problems.

这篇关于为什么MVS编译器可以将参数'myStruct'转换为'myStruct&'。并没有文件错误C2664：不能将'myStruct'转换为'myStruct&的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！