I know that code is from Martin, and I don't mean this as pointing with the finger. There are code reviews, too.
This is a case of the proverbial thin wrapper around a system function, as public API of Phobos. Amongst the large set of operating system abstractions, this one is somewhat deceiving, because it looks the same on each platform, but the parameter has a different meaning on each system. Instead of taking e.g. octal!777 it should really be a D specific enum, IMHO. It is a coincidence that both Windows and POSIX use a 32-bit integer for file attributes, but not technically sound to confuse them in a public API. I'm posting this because concerning the parameter we have a similar situation with our file mode specifiers, which are forwarded to C library functions as is. Depending on the platform they change their meaning as well. Although there many standard flags, "don't inherit file handle in child processes" has never been standardized and cannot be retrofitted in Phobos right now, because we an enum wasn't used in the first place. </rant> -- Marco