C Redefinition Header Files winsock2 h

Question

How do I prevent from including header files twice  The problem is I m including the  in MyClass h and then I m including MyClass h in many files  so it includes  multiple times and redefinition error occurs  How to prevent   I m using  pragma once instead of include guards  and I guess that s fine   MyClass h      MyClass h  pragma once   include  lt winsock2 h gt   class MyClass       methods public   MyClass unsigned short port    virtual  MyClass void        EDIT  Few of the errors I m getting  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

User · Answer

I checked the recursive includes  I spotted the header files which include  recursively  some  include  windows h  and  include  Winsock h  and write a  include  Winsock2 h   in this files  i added  include  Winsock2 h  as the first include   Just a matter of patience  look at includes one by one and establish this order  first   include  Winsock2 h  then  include  windows h

User · Answer

I ran into this problem when trying to pull a third party package which was apparently including windows h somewhere in it s mess of headers   Defining  WINSOCKAPI  at the project level was much easier  not to mention more maintainable  than wading through their soup and fixing the problematic include

User · Answer

pragma once is based on the full path of the filename  So what you likely have is there are two identical copies of either MyClass h or Winsock2 h in different directories

User · Answer

pragma once is flakey  even on MS compilers  and is not supported by many other compilers  As many other people have mentioned  using include guards is the way to go  Don t use  pragma once at all - it ll make your life much easier

User · Answer

In VS 2015  the following will work    define  WINSOCKAPI    While the following won t    define WIN32 LEAN AND MEAN

User · Answer

I wouldn t use just FILENAME H but   ifndef FILENAME H AF06570D B36E 4B82 8F97 C456AF4A38FD  define FILENAME H AF06570D B36E 4B82 8F97 C456AF4A38FD    code stuff  endif    FILENAME H AF06570D B36E 4B82 8F97 C456AF4A38FD   I have always used a postfix guid  I came across a very poor code base some years ago that had different header files with the same file name and include guard  The files in question had defined a class with the same name  If only namespaces were used  Some projects compiled some didn t  Using unique guards was a part of the solution in differentiating headers and their contents   On Windows with Visual Studio use guidgen exe  on Linux uuidgen -t

User · Answer

I found this link windows h and winsock2 h which has an alternative that worked great for me    define  WINSOCKAPI        stops windows h including winsock h  include  lt windows h gt   include  lt winsock2 h gt    I was having trouble finding where the issue occurred but by adding that  define I was able to build without figuring it out

User · Answer

include guards are the standard way of doing this    pragma once is not  meaning that not all compilers support it

User · Answer

In my project  I use VS 2008 SP1  works next solution   Header file     myclass h  pragma once  define  WINSOCKAPI   include  lt windows h gt    Cpp class     myclass cpp  include  Util h   include  winsock2class h   pragma comment lib   Ws2 32 lib     where  include  winsock2class h  mean class which implemented winsock2 h      winsock2class h  include  lt winsock2 h gt   include  lt windows h gt   pragma comment lib   Ws2 32 lib

User · Answer

As others suggested  the problem is when windows h is included before WinSock2 h  Because windows h includes winsock h   You can not use both WinSock2 h and winsock h   Solutions    Include WinSock2 h before windows h  In the case of precompiled headers  you should solve it there  In the case of simple project  it is easy  However in big projects  especially when writing portable code  without precompiled headers  it can be very hard  because when your header with WinSock2 h is included  windows h can be already included from some other header implementation file  Define WIN32 LEAN AND MEAN before windows h or project wide  But it will exclude many other stuff you may need and you should include it by your own  Define  WINSOCKAPI  before windows h or project wide  But when you include WinSock2 h you get macro redefinition warning  Use windows h instead of WinSock2 h when winsock h is enough for your project  in most cases it is   This will probably result in longer compilation time but solves any errors warnings

User · Answer

I ve run into the same issue and here is what I have discovered so far   From this output fragment -    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    -It appears that both ws2def h and winsock h have been included in your solution   If you look at the file ws2def h it starts with the following comment -        Copyright  c  Microsoft Corporation  All rights reserved   Module Name       ws2def h  Abstract       This file contains the core definitions for the Winsock2     specification that can be used by both user-mode and      kernel mode modules       This file is included in WINSOCK2 H  User mode applications     should include WINSOCK2 H rather than including this file     directly  This file can not be included by a module that also     includes WINSOCK H   Environment       user mode or kernel mode  --     Pay attention to the last line -  This file can not be included by a module that also includes WINSOCK H   Still trying to rectify the problem without making changes to the code   Let me know if this makes sense

User · Answer

By using  header guards     ifndef MYCLASS H  define MYCLASS H     This is unnecessary  see comments     pragma once     MyClass h   include  lt winsock2 h gt   class MyClass       methods public      MyClass unsigned short port       virtual  MyClass void        endif

User · Answer

This problem is caused when including  lt windows h gt  before  lt winsock2 h gt   Try arrange your include list that  lt windows h gt  is included after  lt winsock2 h gt  or define  WINSOCKAPI  first    define  WINSOCKAPI        stops windows h including winsock h  include  lt windows h gt          include  MyClass h        Which includes  lt winsock2 h gt    See also this

User · Answer

I actually ran into an issue where I had to define winsock2 h as the first include  it seems it has other issues with includes from other packages  Hope this is helpful to someone who runs into same issue  not just windows h but all includes

User · Answer

You should use header guard   put those line at the top of the header file   ifndef PATH FILENAME H  define PATH FILENAME H   and at the bottom   endif

User · Answer

Oh - the ugliness of Windows     Order of includes are important here   You need to include winsock2 h before windows h   Since windows h is probably included from your precompiled header  stdafx h   you will need to include winsock2 h from there    include  lt winsock2 h gt   include  lt windows h gt

[c++] C++ Redefinition Header Files (winsock2.h)

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