Re: BSD file flags support in Cygwin?

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Nov 14 19:17, Bill Zissimopoulos wrote:
> Corinna, thanks for your answer.
> 
> My question was largely to confirm my understanding as I probably do not
> have time to produce such a patch currently. For the benefit of the
> discussion and to assist any future attempts at doing this:
> 
> Chflags(2) and friends would be relatively easy to implement. OTOH the
> BSD’s and OSX use stat(2) to report file flags in st_flags. Since Cygwin
> lacks an st_flags field, we would have to somehow change struct stat to
> accommodate it. Do you have guidance on how to handle such a change? Would
> you even want such a change? [I suspect not.]

You're right.  Struct stat is exposed to user space so changing this is
bound to break existing applications.  We *might* get away lightly with
just adding a member to the end as in this case, but is the support for
DOS flags actually worth it?  It's still a hassle to support new and old
apps in Cygwin in such cases.

> [I know some OS’es have had to deal with stat(2) changes over the years,
> but I am not as familiar with Cygwin history.]

An executable has the version info of the Cygwin version at the
time of building compiled in.  This is used in Cygwin to check
what an executable expects.

See winsup/cygwin/include/cygwin/version.h and the usage of the
checks throughout the code.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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