MinGW not defining WIN32, error in preprocessor directives

Question

I am using mingw32-make to compile a project to Windows, which depends on a project called libevent2. I keep receiving this error -

util.h:69:25: fatal error: sys/socket.h: No such file or directory

Obviously a file from the Linux API is trying to be included, which won't work on Windows. Upon further investigation I find however that this file should only be included if WIN32 isn't defined.

#ifdef WIN32
 #include <winsock2.h>
#else
 #include <sys/socket.h>
#endif

Answer 1

You should use _WIN32 and may also want to check for __CYGWIN__

#if defined _WIN32 || defined __CYGWIN__

Answer 2

Are you sure there's nothing undefining WIN32? My installation of MinGW (4.6.1 at this site) definitely defines it:

C:\temp>gcc -E -dM test.c | find /i "win"
#define _WIN32 1
#define __WINT_MAX__ 65535
#define _WINT_T
#define __WINT_MIN__ 0
#define __WIN32 1
#define __WINNT 1
#define __WINNT__ 1
#define __WIN32__ 1
#define __SIZEOF_WINT_T__ 2
#define WIN32 1                 // <-- right here
#define __WINT_TYPE__ short unsigned int
#define WINNT 1

Try passing the -E -dM options to verify if your MinGW compiler is (or isn't) pre-defining the WIN32 macro.

Note that strictly speaking, WIN32 should not be predefined by the compiler (since it's in the user's namespace) - only _WIN32 should. WIN32 should be set by the SDK being used and/or by the build environment - that's the way it works in Microsoft's compilers.

For example, there's the following sequence in windef.h"

#ifndef WIN32
#define WIN32
#endif

and /D "WIN32" is put into Visual Studio C++ projects by default.

See https://stackoverflow.com/a/662543/12711 for more details.