RFR: 8293122: (fs) Use file cloning in macOS version of Files::copy method [v4]

[Alan Bateman]

On Mon, 12 Sep 2022 16:22:39 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Use BSD system call `clonefile` if possible when using `Files::copy` on macOS.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8293122: Move rollback unlink to copyFile method

src/java.base/macosx/classes/sun/nio/fs/BsdFileSystem.java line 128:

> 126:         // Attempt to clone the source unless cancellation is not possible,
> 127:         // or attributes are not to be copied
> 128:         if (addressToPollForCancel == 0 && flags.copyPosixAttributes) {

It wouldn't be wrong to the check for copyPosixAttributes here, in which case they would be copied by default (the spec allows for that). The only issue is that someone might become dependent on this and then be surprised when they code behaves differently when run on another platform.

I'm curious if there is a way to test how clone behaves when it fails. What you have is okay although the unlink might only be needed when chown fails.

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PR: https://git.openjdk.org/jdk/pull/10188