alexrp/d-programming-language.org — comment on commit 5d57f8f590800b92eb6ce15e6f2a42cd6060f2b9
File:  line 0
By TurkeyMan:

I doubt all those OS's and architectures you already added are in use ;)

That said, I've been experimenting with PSP, there's a Nintendo DS compiler floating around, I think it's only a matter of time (if not already) that Android and iOS toolchains get used. These are all GDC based, which is easy to build for any platform/architecture now.

I think the main reason for proactively defining platforms/architectures is that it encourages vendors to use the names already defined. A common problem with C/C++ toolchains is that vendors for particular platforms almost always just make their own defines up. Consequently, 2 different toolchains for the same platform/system are rarely identified the same way, leading to a big block of ifdef spam at the top of all common headers.