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Message-ID: <6d1a8071-76f7-b634-b4ce-07ce6c18a8d9@dronecode.org.uk>
Date: Mon, 10 Jan 2022 15:39:05 +0000
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Subject: Re: Cygwin setup writing incorrect symlinks for native
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To: David Allsopp <David DOT Allsopp AT cl DOT cam DOT ac DOT uk>,
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From: Jon Turney <jon DOT turney AT dronecode DOT org DOT uk>
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On 09/01/2022 09:35, David Allsopp wrote:
> Jon Turney wrote:
>> On 06/01/2022 16:45, David Allsopp wrote:
>>> Jon Turney wrote:
>>>> On 06/01/2022 10:46, David Allsopp wrote:
>>>>> Running Cygwin setup 2.912 with --symlink-type native (or
>>>>> CYGWIN=winsymlinks:native) is not correctly translating all symlinks.
>>>>> A default install has these faulty ones:
>>>>>
>>>>> /etc/pki/tls/cert.pem ->
>>>>> \??\/etc\pki\ca-trust\extracted\pem\tls-ca-bundle.pem
>>>>> /etc/pki/tls/certs/ca-bundle.crt ->
>>>>> \??\/etc\pki\ca-trust\extracted\pem\tls-ca-bundle.pem
>>>>> /etc/pki/tls/certs/ca-bundle.trust.crt ->
>>>>> \??\/etc\pki\ca-trust\extracted\openssl\ca-bundle.trust.crt
>>>>> /etc/ssl/certs -> \??\/etc\pki\tls\certs /lib/security/cacerts ->
>>>>> \??\/etc\pki\ca-trust\extracted\java\cacerts
>>>>> /usr/share/doc/groff-1.22.4/pdf/mom-pdf.pdf ->
>>>>> \??\/usr\share\doc\groff-1.22.4\examples\mom\mom-pdf.pdf
>>>>
>>>>
[...]
>>
>> Thanks for testing.  It seems I still didn't have this quite right and
>> these symlinks just happened to work for cygwin, but not native tools.
>>
>> Please try
>>
>>     https://cygwin.com/setup/setup-2.914.x86_64.exe
>>     https://cygwin.com/setup/setup-2.914.x86.exe
> 
> I'm afraid that's just changed the \??\ to \\?\ on those symlinks.

Well, that has the advantage of being correct :)

(since it's the 'Win32 File Namespace' prefix, which 
CreateSymbolicLinkW() is documented to accept for the target filename, 
and is required when that exceeds MAX_PATH (260) characters)

In my (brief) testing, e.g. the CMD builtin 'type' is able to open 
symlinks of this form.  However, it seems there are some parts of 
Windows (e.g. DIR, File Explorer), which don't handle symlinks like that 
well.

So, I've copied the behaviour of the cygwin DLL, which avoids using that 
prefix if the target is less than MAX_PATH characters.  This seem to 
work better in those cases with typical paths (but I'd claim we're just 
working around a bug in Windows here, as things will still be broken if 
the cygwin root is a path long enough that we can't do that).

Please try:

   https://cygwin.com/setup/setup-2.915.x86_64.exe
   https://cygwin.com/setup/setup-2.915.x86.exe


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