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Message-ID: <f2641cc4-cfb4-4248-a50c-23e611b0bb9a@SystematicSW.ab.ca>
Date: Thu, 13 Jun 2024 16:39:47 -0600
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Subject: Re: unable to remove oddly-named directory
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To: cygwin AT cygwin DOT com
References: <6f296b1c-ad43-81e3-163b-4bc4d1b8ed4c AT jdrake DOT com>
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From: Brian Inglis via Cygwin <cygwin AT cygwin DOT com>
Reply-To: cygwin AT cygwin DOT com
Cc: Brian Inglis <Brian DOT Inglis AT SystematicSW DOT ab DOT ca>
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On 2024-06-13 14:59, Jeremy Drake via Cygwin wrote:
> Backstory: rust's test suite makes an oddly-named directory as part of a
> test:
> https://github.com/rust-lang/rust/blob/921645c737f1d6d107a0a10ca5ee129d364dcd7a/tests/run-make/non-unicode-in-incremental-dir/rmake.rs
> 
> When trying to clean up after a rust build/test with rm -rf, it results in
> a "Directory not empty" error.

Suggest using rust uutils for this, as rust created it:

	https://uutils.github.io/coreutils/
	https://github.com/uutils/coreutils

> Thankfully, this can be simply reproduced with the following two bash
> commands (on cygwin 3.5.3):
> 
> mkdir -p foo/$'\uD800'
> rm -rf foo
> 
> This fails with: rm: cannot remove 'foo': Directory not empty
> when it should succeed.

That is questionable as that value is a reserved Unicode high surrogate for a 
Unicode character higher than UTF-16 was originally designed for.

$ mkdir -p foo/$'\uD800'
$ rm -rf  foo # /$'\uD800'
/bin/rm: cannot remove 'foo': Directory not empty
$ rm -rf  foo/$'\uD800'
removed directory 'foo/'$'\355\240\200'
$ rm -rf  foo
removed directory 'foo'

These reserved surrogate values should probably either be blocked, or encoded at 
the file system interface layer so they can be round tripped, like the Windows 
reserved characters, in the BMP or SMP PUAs.

Reserved surrogate ranges are D800-DBFF|DC00-DFFF.

Reserved noncharacters are U+FDD0-FDEF, and the last two code points of the BMP 
U+FFFE-FFFF, and each of the SMPs: U+{1-10}FFFE-{1-10}FFFF.

Allowed PUAs are U+E000-F8FF, U+F0000-FFFFD and U+100000-10FFFD.

Corinna? Opinions?

It would also be good to avoid the CSUR U+E000-E82F, U+F8A0-F8FF, U+F0000-F16AF:

	https://www.evertype.com/standards/csur/

and UCSUR U+E830-EDFF, U+F4C0-F4EF, U+F16B0-F1C9F, F1F00-F289F registry ranges:

	https://www.kreativekorp.com/ucsur/

as some fonts may render these, as they are used by applications.

These registry folks are major contributors to Unicode standards, and these 
efforts bring order to supporting, managing, and using minority, minor 
historical or ancient, undeciphered, or constructed (e.g. Mormon, Shaw, Tolkien, 
Le Guin, Star Trek, Star Wars) language scripts or writing systems with glyphs 
not (yet) officially assigned in Unicode Standards.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry

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