Re: basing *at functions over openat when available?

[Paolo Bonzini]

> P.S. The Cygwin developers discovered that NtCreateFile/NtOpenFile, when
> used to open a relative file, has quadratic behavior in the length of the
> absolute file name being opened, in Windows XP and earlier; this time is
> attributed to the system call and not the application.  Microsoft fixed it
> to have linear performance on relative names in newer versions of Windows,
> and even acknowledged the bug in earlier versions, but is not going to
> address it.  So even if we implemented openat with these functions, it
> would not add any speed to super-long paths under mingw on older Windows.

Yes, my only reason to use NtCreateFile/NtOpenFile would be to have 
non-racy fts, and see if I can eliminate the funny open wrappers.

> More interesting will be implementing utimensat, where there are indeed
> systems with openat and futimes where that may be the best fallback.

Indeed I mentioned fchmodat just as an example (and an ill-chosen one 
apparently), but this applies to any *at function.

Paolo