关于error LNK2005错误的问题。

[baoyz]

昨天，写一个关于EXCEL文件的程序。基于对话框。使用的是CSpreadSheet.h（网上到处都有）。
把头文件加入CMAINDLG中，编译通过。
再把头文件加入CUSERAPPLY1DLG(USERAPPLY1类)中，编译错误。
出现

USERAPPLY1.obj : error LNK2005: "public: __thiscall CSpreadSheet::CSpreadSheet(class CString,class CString,bool)" (??0CSpreadSheet@@QAE@VCString@@0_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: __thiscall CSpreadSheet::~CSpreadSheet(void)" (??1CSpreadSheet@@QAE@XZ) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::AddHeaders(class CStringArray &,bool)" (?AddHeaders@CSpreadSheet@@QAE_NAAVCStringArray@@_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::DeleteSheet(void)" (?DeleteSheet@CSpreadSheet@@QAE_NXZ) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::DeleteSheet(class CString)" (?DeleteSheet@CSpreadSheet@@QAE_NVCString@@@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::AddRow(class CStringArray &,long,bool)" (?AddRow@CSpreadSheet@@QAE_NAAVCStringArray@@J_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::AddCell(class CString,class CString,long,bool)" (?AddCell@CSpreadSheet@@QAE_NVCString@@0J_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::AddCell(class CString,short,long)" (?AddCell@CSpreadSheet@@QAE_NVCString@@FJ@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::ReplaceRows(class CStringArray &,class CStringArray &)" (?ReplaceRows@CSpreadSheet@@QAE_NAAVCStringArray@@0@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::ReadRow(class CStringArray &,long)" (?ReadRow@CSpreadSheet@@QAE_NAAVCStringArray@@J@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::ReadColumn(class CStringArray &,class CString,bool)" (?ReadColumn@CSpreadSheet@@QAE_NAAVCStringArray@@VCString@@_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::ReadColumn(class CStringArray &,short)" (?ReadColumn@CSpreadSheet@@QAE_NAAVCStringArray@@F@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::ReadCell(class CString &,class CString,long,bool)" (?ReadCell@CSpreadSheet@@QAE_NAAVCString@@V2@J_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::ReadCell(class CString &,short,long)" (?ReadCell@CSpreadSheet@@QAE_NAAVCString@@FJ@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: void __thiscall CSpreadSheet::BeginTransaction(void)" (?BeginTransaction@CSpreadSheet@@QAEXXZ) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::Commit(void)" (?Commit@CSpreadSheet@@QAE_NXZ) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::RollBack(void)" (?RollBack@CSpreadSheet@@QAE_NXZ) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "public: bool __thiscall CSpreadSheet::Convert(class CString)" (?Convert@CSpreadSheet@@QAE_NVCString@@@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "private: bool __thiscall CSpreadSheet::Open(void)" (?Open@CSpreadSheet@@AAE_NXZ) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "private: short __thiscall CSpreadSheet::CalculateColumnNumber(class CString,bool)" (?CalculateColumnNumber@CSpreadSheet@@AAEFVCString@@_N@Z) already defined in PRICEDlg.obj
USERAPPLY1.obj : error LNK2005: "private: void __thiscall CSpreadSheet::GetExcelDriver(void)" (?GetExcelDriver@CSpreadSheet@@AAEXXZ) already defined in PRICEDlg.obj
Debug/PRICE.exe : fatal error LNK1169: one or more multiply defined symbols found
Error executing link.exe.

找过多个方法：
1、头文件中做类似的处理：#ifndef MY_H_FILE //如果没有定义这个宏
#define MY_H_FILE //定义这个宏
……. //头文件主体内容
…….
#endif
无效，文件本身就有，再加一个还是无效。
2、使用预编译来做，在头文件中加入：
#pragma once
无效。
3、在IDE下Project->Settings->Link页,选categroy为custom,将force file output前打勾，有一堆的警告。不知是否影响效果。
4、将.CPP包含头文件的顺序改变。
原来是

#include "stdafx.h"
#include "MAIN.h"
#include "USERAPPLY1.h"
#include "CSpreadSheet.h"

改为

#include "CSpreadSheet.h"
#include "stdafx.h"
#include "MAIN.h"
#include "USERAPPLY1.h"

可以编译但是不能适用"CSpreadSheet.h"中定义的函数。
#include "CSpreadSheet.h"不在第1行编译就失败。
请用过"CSpreadSheet.h"的高人指点。

[iyranly]

One of the following may be a cause:

1、The most common cause of this error is accidentally linking with both the single-threaded and multithreaded libraries. Ensure that the application project file includes only the appropriate libraries and that any third-party libraries have appropriately created single-threaded or multithreaded versions.


2、The given symbol was a packaged function (created by compiling with /Gy) and was included in more than one file but was changed between compilations. Recompile all files that include the symbol.


3、The given symbol was defined differently in two member objects in different libraries, and both member objects were used.


4、An absolute was defined twice, with a different value in each definition.

[buyong]

重复定义了
在CUSERAPPLY1DLG中不加头文件，改为声明
class CSpreadSheet;

[iyranly]

http://www.cnblogs.com/zealsoft/archive/2006/04/24/383567.aspx

[iyranly]

只要工程中有两个以上的地方包含这个头文件就会出现这个错误。解决的办法很简单，建立一个CSpreadSheet.cpp文件，然后在这个文件的开头加上：


#include “stdafx.h”
#include “CSpreadSheet.h”
然后把CSpreadSheet.h中的从”// Open spreadsheet for reading and writing”（含）到”#endif”（不含）之前的语句都剪切到CSpreadSheet.cpp中，也就是将类的声明和实现分离，再将CSpreadSheet.cpp文件加到工程中，这样就可以了。

[baoyz]

To:buyong
class CSpreadSheet;以后，构造函数CSpreadSheet ss("t2.xls","t2",true);不能使用了。
error C2079: 'ss' uses undefined class 'CSpreadSheet'
改成声明后是否需要加其他语句？

To:云之巅
方法可用。谢谢。加分。

[iyranly]

谢谢

[baoyz]

加分了。

[masktime]

我最近也遇到这个问题，云之巅，问题解决了，哈哈