The windx5 video driver defines the NONAMELESSUNION symbol before including <ddraw.h>, but only if __GNUC__ is defined:

#ifdef __GNUC__
#define NONAMELESSUNION
#endif

This is simply not necessary, as the GNU compilers already supports unnamed unions.

Moreover, defining this symbol even causes trouble in some MinGW configurations, depending on which set of DirectX headers one uses.

There are some sets that requires NONAMELESSUNION to be defined before the first "#include <windows.h>", not just before the first "#include <ddraw.h>". In those cases, the rest of SDL will compile under the assumption that unions are named, but the headers still define unnamed unions, which leads to compiling errors. Recently, that caused a lot of trouble in the mingw-cross-env project.

Long story short: Defining NONAMELESSUNION is unneeded and does more harm than good, so I recommend to remove it.

The attached patch does exactly that.