RFR: 8343020: SecureDirectoryStream not supported on MacOS

[Brian Burkhalter]

On Thu, 24 Oct 2024 21:54:55 GMT, David M. Lloyd <duke at openjdk.org> wrote:

> OpenJDK will not produce SecureDirectoryStreams on MacOS. Support for SecureDirectoryStream on UNIX-like OSes is predicated on the `SUPPORTS_OPENAT` flag in UnixNativeDispatcher. That flag in turn is set when the runtime environment supports `openat`, `fstatat`, `unlinkat`, `renameat`, `futimesat`, and `fdopendir`.
> 
> This fails on MacOS because `futimesat` does not exist on that platform, apparently having been a proposed-but-not-accepted part of POSIX some time ago. While there is an indirect replacement that is supported on MacOS - `utimensat` - this is not actually needed, because the unique functionality provided by `futimesat` (that is, performing the action of `futimes` relative to an open directory file descriptor) is not utilized, since the only place this function is used passes `NULL` as the relative filename argument.
> 
> Replacing this with simply calling `futimes` instead allows `SecureDirectoryStream` to function on MacOS.

There is no `noreg-*` label on the issue. Is this change covered by an existing test?

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PR Comment: https://git.openjdk.org/jdk/pull/21696#issuecomment-2436530199