C++ compiling on Windows and Linux: ifdef switch

I want to run some c++ code on Linux and Windows. There are some pieces of code that I want to include only for one operating system and not the other. Is there a standard #ifdef that once can use?

Something like:

  #ifdef LINUX_KEY_WORD
    ... // linux code goes here.
  #elif WINDOWS_KEY_WORD
    ... // windows code goes here.
  #else 
  #error "OS not supported!"
  #endif

---

The question is indeed a duplicate but the answers here are much better, especially the accepted one.

use:

#ifdef __linux__ 
    //linux code goes here
#elif _WIN32
    // windows code goes here
#else

#endif

You can do:

#if MACRO0
    //code...
#elif MACRO1
    //code...
#endif

…where the identifier can be:

    __linux__       Defined on Linux
    __sun           Defined on Solaris
    __FreeBSD__     Defined on FreeBSD
    __NetBSD__      Defined on NetBSD
    __OpenBSD__     Defined on OpenBSD
    __APPLE__       Defined on Mac OS X
    __hpux          Defined on HP-UX
    __osf__         Defined on Tru64 UNIX (formerly DEC OSF1)
    __sgi           Defined on Irix
    _AIX            Defined on AIX
    _WIN32          Defined on Windows

I know it is not answer but added if someone looking same in Qt

In Qt

https://wiki.qt.io/Get-OS-name-in-Qt

QString Get::osName()
{
#if defined(Q_OS_ANDROID)
    return QLatin1String("android");
#elif defined(Q_OS_BLACKBERRY)
    return QLatin1String("blackberry");
#elif defined(Q_OS_IOS)
    return QLatin1String("ios");
#elif defined(Q_OS_MAC)
    return QLatin1String("osx");
#elif defined(Q_OS_WINCE)
    return QLatin1String("wince");
#elif defined(Q_OS_WIN)
    return QLatin1String("windows");
#elif defined(Q_OS_LINUX)
    return QLatin1String("linux");
#elif defined(Q_OS_UNIX)
    return QLatin1String("unix");
#else
    return QLatin1String("unknown");
#endif
}

It depends on the used compiler.

For example, Windows' definition can be WIN32 or _WIN32.

And Linux' definition can be UNIX or __unix__ or LINUX or __linux__.

This response isn't about macro war, but producing error if no matching platform is found.

#ifdef LINUX_KEY_WORD   
... // linux code goes here.  
#elif WINDOWS_KEY_WORD    
... // windows code goes here.  
#else     
#error Platform not supported
#endif

If #error is not supported, you may use static_assert (C++0x) keyword. Or you may implement custom STATIC_ASSERT, or just declare an array of size 0, or have switch that has duplicate cases. In short, produce error at compile time and not at runtime

It depends on the compiler. If you compile with, say, G++ on Linux and VC++ on Windows, this will do :

#ifdef linux
    ...
#elif _WIN32
    ...
#else
    ...
#endif

No, these defines are compiler dependent. What you can do, use your own set of defines, and set them on the Makefile. See this thread for more info.