G ++编译器错误 - 这里首先需要合成的方法 [英] G++ compiler error - Synthesized method first required here

问题描述

 包含在/usr/lib/gcc/x86_64-redhat-linux/4.4的文件中。 6 /../../../../include/c ++/4.4.6/ios：39，
来自/usr/lib/gcc/x86_64-redhat-linux/4.4.6/ .. /../../../include/c++/4.4.6/ostream:40，来自/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../的
 ../../include/c++/4.4.6/iostream:40，从date.h获得
：15，从date.cpp获得
：13：
 / usr / lib / gcc /x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h：在拷贝构造函数'std :: basic_ios< char，std： ：char_traits<炭> > :: basic_ios（const std :: basic_ios< char，std :: char_traits< char>&&）'：
 /usr/lib/gcc/x86_64-redhat-linux/4.4.6/。 ./../../../include/c++/4.4.6/bits/ios_base.h:790：error：'std :: ios_base :: ios_base（const std :: ios_base&）'是私有
 /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:47：错误：在此上下文中
 /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd：在拷贝构造函数'std :: basic_ostream< char，std :: char_traits< char> > :: basic_ostream（const std :: basic_ostream< char，std :: char_traits< char>&&）'：
 /usr/lib/gcc/x86_64-redhat-linux/4.4.6/。 ./../../../include/c++/4.4.6/iosfwd:56：note：合成方法'std :: basic_ios< char，std :: char_traits< char> > :: basic_ios（const std :: basic_ios< char，std :: char_traits< char>&）&）'首先在这里需要
 date.cpp：在函数'std :: ostream operator<（ std :: ostream&; Date&）'：
 date.cpp：389：note：合成方法'std :: basic_ostream< char，std :: char_traits< char> > :: basic_ostream（const std :: basic_ostream< char，std :: char_traits< char>&）&'''首先在这里需要
 make：*** [date.o]错误1 
  

我认为这可能与我的头文件和源文件如何编译在一起，所以这里是代码：

标题：

  #ifndef DATE_H 
 #define DATE_H 
 
 #include< iostream> 
使用namespace std; 
 
 //基本但很长的班级代码
 
 #endif 
  

来源：

  //＃包括< iostream> //尝试使用和不使用这种编译方式进行编译，但没有更改
 #include< cassert> 
 #include< cstdlib> 
 #includedate.h//这是（date.cpp：13）
 //我试过使用命名空间std，只是为了看看会发生什么，但没有改变
  code> 

最后，这是编译器引用的函数（date.cpp：389）：



  ostream操作符<<（lt;& out，const日期&日期）
 {
 //天
出<< date.day; 
 switch（date.day）
 {
案例1：
案例21：
案例31：
 out<< ST; 
休息; 
案例2：
案例22：
 out<< ND; 
休息; 
案例3：
案例23：
 out<< RD; 
休息; 
默认值：
出<< TH; 
休息; 
} 
 
 //月
 const char MONTHS [12] [10] = 
 {January，February，March，April ，五月，六月，
七月，八月，九月，十月，十一月，十二月}; 
 
 out<< of< MONTHS [date.month-1]<< ，; 
 
 //年份
出<< date.year; 
 
退出; 
} 
  

我在这里完全不解。我在最后一个小时搜索了一下，但找不到解决我问题的任何内容。感谢您提前提供任何帮助！

解决方案

问题是您无法返回普通的 code>。你必须返回一个引用作为参数（注意& ）。

  ostream&运算符<<<<<<<<<<<>& out，const Date& date）
  

它不能通过复制上的 out 来创建新的 ostream 对象 return out; 。

Here's the error:

In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ios:39,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ostream:40,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iostream:40,
                 from date.h:15,
                 from date.cpp:13:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h: In copy constructor ‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h:790: error: ‘std::ios_base::ios_base(const std::ios_base&)’ is private
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:47: error: within this context
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd: In copy constructor ‘std::basic_ostream<char, std::char_traits<char> >::basic_ostream(const std::basic_ostream<char, std::char_traits<char> >&)’:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:56: note: synthesized method ‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’ first required here 
date.cpp: In function ‘std::ostream operator<<(std::ostream&, Date&)’:
date.cpp:389: note: synthesized method ‘std::basic_ostream<char, std::char_traits<char> >::basic_ostream(const std::basic_ostream<char, std::char_traits<char> >&)’ first required here 
make: *** [date.o] Error 1

I think it may have to do with how my header and source file are compiling together so here is the code for that:

Header:

#ifndef DATE_H
#define DATE_H

#include <iostream>
using namespace std;

// basic but lengthy class code

#endif

Source:

// #include <iostream>  // tried compiling with and without this, but no change
#include <cassert>
#include <cstdlib>
#include "date.h"       // this is (date.cpp:13)
// I have tried using namespace std, just to see what would happen but nothing changed

Finally, here is the function that the compiler is referring to (date.cpp:389):

ostream operator <<(ostream &out, const Date &date)
{
    // day                                                                      
    out << date.day;
    switch (date.day)
    {
        case 1:
        case 21:
        case 31:
            out << "st";
            break;
        case 2:
        case 22:
            out << "nd";
            break;
        case 3:
        case 23:
            out << "rd";
            break;
        default:
            out << "th";
            break;
    }

    // month                                                                    
    const char MONTHS[12][10] =
    { "January", "February", "March",     "April",   "May",      "June",
        "July",    "August",   "September", "October", "November", "December"};

    out << " of " << MONTHS[date.month - 1] << ", ";

    // year                                                                     
    out << date.year;

    return out;
}

I am completely baffled here. I have Googled around for the last hour but I can't find anything that solves my problem. Thanks for any help in advance!

解决方案

The problem is that you cannot return a plain ostream. You have to return a reference to the one you received as argument (note the &).

ostream & operator <<(ostream &out, const Date &date)

The compiler complains that it cannot create a new ostream object by copying out on the line return out;.

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