如何防止包含两次头文件?问题是我在MyClass.h中包含,然后我在许多文件中包含MyClass.h,所以它包含多次和重定义错误发生。如何预防?
我使用了#杂注一次,而不是包含守卫,我想这是很好的。
H:MyClass.h
// MyClass.h
#pragma once
#include <winsock2.h>
class MyClass
{
// methods
public:
MyClass(unsigned short port);
virtual ~MyClass(void);
};
编辑:几个我得到的错误
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(91) : warning C4005: 'AF_IPX' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(460) : see previous definition of 'AF_IPX'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(124) : warning C4005: 'AF_MAX' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(479) : see previous definition of 'AF_MAX'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(163) : warning C4005: 'SO_DONTLINGER' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(402) : see previous definition of 'SO_DONTLINGER'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(206) : error C2011: 'sockaddr' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(485) : see declaration of 'sockaddr'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(384) : error C2143: syntax error : missing '}' before 'constant'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(384) : error C2143: syntax error : missing ';' before 'constant'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(384) : error C2059: syntax error : 'constant'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(437) : error C2143: syntax error : missing ';' before '}'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(437) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(437) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(518) : warning C4005: 'IN_CLASSA' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(287) : see previous definition of 'IN_CLASSA'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(524) : warning C4005: 'IN_CLASSB' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(293) : see previous definition of 'IN_CLASSB'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(530) : warning C4005: 'IN_CLASSC' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(299) : see previous definition of 'IN_CLASSC'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(541) : warning C4005: 'INADDR_ANY' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(304) : see previous definition of 'INADDR_ANY'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(543) : warning C4005: 'INADDR_BROADCAST' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(306) : see previous definition of 'INADDR_BROADCAST'
c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(577) : error C2011: 'sockaddr_in' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(312) : see declaration of 'sockaddr_in'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(132) : error C2011: 'fd_set' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(68) : see declaration of 'fd_set'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(167) : warning C4005: 'FD_SET' : macro redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(102) : see previous definition of 'FD_SET'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(176) : error C2011: 'timeval' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(111) : see declaration of 'timeval'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(232) : error C2011: 'hostent' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(167) : see declaration of 'hostent'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(245) : error C2011: 'netent' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(180) : see declaration of 'netent'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(252) : error C2011: 'servent' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(187) : see declaration of 'servent'
c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(264) : error C2011: 'protoent' : 'struct' type redefinition
c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(199) : see declaration of 'protoent'
发布于 2009-09-03 11:23:11
在<winsock2.h>
之前包含<windows.h>
时会导致此问题。尝试将包含列表排列为在<winsock2.h>
之后包含<windows.h>
,或者先定义_WINSOCKAPI_
:
#define _WINSOCKAPI_ // stops windows.h including winsock.h
#include <windows.h>
// ...
#include "MyClass.h" // Which includes <winsock2.h>
另请参见this。
发布于 2011-11-28 18:47:14
正如其他人所建议的,问题在于何时在WinSock2.h
之前包含windows.h
。因为windows.h
包含winsock.h
。您不能同时使用WinSock2.h
和winsock.h
。
解决方案:
windows.h
之前包含WinSock2.h
。在预编译头的情况下,您应该在那里解决它。在简单项目的情况下,这很容易。然而,在大型项目中(特别是在编写可移植代码时,没有预编译头文件),这可能非常困难,因为当包含带有WinSock2.h
的头文件时,windows.h
可能已经包含在其他一些头文件/实现文件中。windows.h
或项目范围之前定义WIN32_LEAN_AND_MEAN
。但它将排除你可能需要的许多其他东西,你应该自己包括它。windows.h
或项目范围之前定义_WINSOCKAPI_
。但是当你包含WinSock2.h
时,你会得到宏重定义的警告。winsock.h
足够你的项目的时候使用windows.h
而不是WinSock2.h
(大多数情况下是这样的)。这可能会导致较长的编译时间,但会解决所有errors/warnings.发布于 2010-07-15 15:24:30
哦-Windows的丑陋...在这里,includes的顺序很重要。您需要在windows.h之前包含winsock2.h。由于windows.h可能包含在预编译头文件(stdafx.h)中,因此需要在其中包含winsock2.h:
#include <winsock2.h>
#include <windows.h>
https://stackoverflow.com/questions/1372480
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