C2065'cout':未声明的标识符

时间:2018-08-31 14:44:20

标签: c++ visual-studio stl visual-studio-2017 cout

因此,我是C ++的完整入门者,并且我正在尝试制作一个简单的“ Hello world”程序进行作业。我的代码如下:

#include "stdafx.h"
#include <iostream>
using namespace std;
int main() {
    cout<<"hello world!";
    return 0;
}

由于某些原因,VS2017在cout处引发错误,表示未定义。我已经阅读了一些有关旧帖子的内容,并在#include "stdafx.h中进行了添加,以查看是否可以按照旧建议解决该问题,但这仍然给我带来了错误。有什么想法吗?

编辑:

还是一个完整的菜鸟,但是当我搜索它时会出现多个版本的stdafx.h,这看起来像是“主要”一个:

  // stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently,
// but are changed infrequently

#pragma once

#ifndef STRICT
#define STRICT
#endif

#include "targetver.h"

[!if SERVICE_APP]
#define _ATL_FREE_THREADED
[!else]
#define _ATL_APARTMENT_THREADED
[!endif]

#define _ATL_NO_AUTOMATIC_NAMESPACE

#define _ATL_CSTRING_EXPLICIT_CONSTRUCTORS  // some CString constructors will be explicit

[!if PREVIEW_HANDLER || THUMBNAIL_HANDLER || SEARCH_HANDLER]
#ifdef _MANAGED
#error File type handlers cannot be built as managed assemblies.  Set the Common Language Runtime options to no CLR support in project properties.
#endif

#ifndef _UNICODE
#error File type handlers must be built Unicode.  Set the Character Set option to Unicode in project properties.
#endif

#define SHARED_HANDLERS

[!endif]
[!if SUPPORT_MFC]
#include <afxwin.h>
#include <afxext.h>
#include <afxole.h>
#include <afxodlgs.h>
#include <afxrich.h>
#include <afxhtml.h>
#include <afxcview.h>
#include <afxwinappex.h>
#include <afxframewndex.h>
#include <afxmdiframewndex.h>

#ifndef _AFX_NO_OLE_SUPPORT
#include <afxdisp.h>        // MFC Automation classes
#endif // _AFX_NO_OLE_SUPPORT
[!endif]
[!if SUPPORT_COMPLUS]

#include <comsvcs.h>
[!endif]

#define ATL_NO_ASSERT_ON_DESTROY_NONEXISTENT_WINDOW

#include "resource.h"
#include <atlbase.h>
#include <atlcom.h>
#include <atlctl.h>

1 个答案:

答案 0 :(得分:5)

error C2065: 'cout': undeclared identifier是缺少#include <iostream>的结果。第一个原因可能是stdafx.h的内容。您提供的一个,我不确定它与您的main.cpp /项目有什么关系。让我们从一个新项目开始: ... VS2017 IDE:创建一个新项目,ConsoleApplication项目类型,并用您的函数替换main()函数。

一个VS2017 IDE(15.8.2)全新的ConsoleApplication项目:ConsoleApplication1

// ConsoleApplication1.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>

using namespace std;

int main() {

    cout << "hello world!";
    return 0;
}

stdafx.h:(由IDE生成)

// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once

#include "targetver.h"


// TODO: reference additional headers your program requires here

stdafx.cpp:(由IDE生成)

// stdafx.cpp : source file that includes just the standard includes
// ConsoleApplication1.pch will be the pre-compiled header
// stdafx.obj will contain the pre-compiled type information

#include "stdafx.h"

// TODO: reference any additional headers you need in STDAFX.H
// and not in this file

targetver.h:(由IDE生成)

#pragma once

// Including SDKDDKVer.h defines the highest available Windows platform.

// If you wish to build your application for a previous Windows platform, include WinSDKVer.h and
// set the _WIN32_WINNT macro to the platform you wish to support before including SDKDDKVer.h.

#include <SDKDDKVer.h>

**这段代码可以完美运行。 **

-

“搜索时会出现stdafx.h的多个版本” -您是什么意思?在您的项目中?在网上?您不能只从互联网上获取一个stdafx.hstdafx.h内容是针对每个项目量身定制的,并非通用。例如,我在上面提供的是IDE默认的新ConsoleApplication项目stdafx.h。您可以根据项目需要将其添加到文件中。