[ianremsen]

I think it's wrong to call it poorly written because the programmer only accounted their C preprocessor code for ~99.99% of desktop and mobile operating systems. The diminishing return for avoiding this approach is so impalpable it hurts. Windows, OSX/iOS/BSD, and Linux/Android literally are everything anyone ever uses, within rounding error.

[ori_b]

The diminishing return approach is this:

     #ifdef LINUX
     // include Linux headers
     #elif defined(BSD)
     // include BSD headers
     #elif defined(WINDOWS)
     // include Windows headers.
     # else
     #error "unsupported system"
     #endif

[viraptor]

If you develop for different platforms then it may actually make sense to do a "if linux / elif bsd / elif windows / else #error unsupported". At least it gives you a proper answer in case you forgot you have some wild crosscompiler in your path. But I understand it's not a popular concern...