Identifying the target platform

A common problem is identifying the target platform at compile-time so that specific code can be used, perhaps to work around a quirk, or to access a non-standard feature of the target platform.

Standard compiler platform macros

The following table is a partial extract of [Pre-defined C/C++ Compiler Macros], part of a useful resource to compiler macro definitions.

Please update the table carefully with your platform or corrections:

Platform macros

Platform	Defined macro	Other notes
FreeBSD	__FreeBSD__	Consider using the BSD macro
Linux	linux or __linux
MacOS X	__MACOSX__ or __APPLE__
NetBSD	__NetBSD__	Consider using the BSD macro
OpenBSD	__OpenBSD__	Consider using the BSD macro
Solaris	sun or __sun	SunOS versions < 5 will not have __SVR4 or __svr4__ defined
Windows	_WIN32 or __WIN32__

You can use #if wrappers like:

#if defined (__FreeBSD__)
...
#elif defined (__linux) || defined (linux)
...
#else
...
#endif

Using GNUStep-Make's support

Chris Vetter shared a tip on the use of your GNUmakefile.preamble with the following line:

ADDITIONAL_OBJCFLAGS += -D$(GNUSTEP_HOST_OS)

and then the #if wrappers will look like:

#if defined (freebsd)
...
#elif defined (netbsdelf)
...
#else
...
#endif