LDC and DMD are basically at the same frontend, so it is rare to do a `version(LDC)`. GDC is a bit behind atm, but the language and library is really stable. Usually you don't change anything at all between compilers and OS. Most notable exceptions is the SIMD capabilities, and inline assembly is different on GDC. The stdlib covers a lot of ground so portability across OSes is much easier than in you-know-which-language, so small tools tend to blossom.