tzcode resync
Corinna Vinschen
corinna-cygwin@cygwin.com
Wed Apr 29 08:34:19 GMT 2020
Hi Mark,
On Apr 29 00:03, Mark Geisert wrote:
> Hi folks,
>
> On Mon, 27 Apr 2020, Corinna Vinschen wrote:
> > On Apr 24 17:19, Yaakov Selkowitz wrote:
> > > Our winsup/cygwin/localtime.cc is a mashup of a very old version of
> > > upstream tzcode's private.h, tzfile.h, and localtime.c with Cygwin-
> > > specific patches for getting the timezone from windows as a fallback,
> > > as well as handling API compatibility with pre-tm_gmtoff binaries.
> > >
> > > The upstream tzcode/tzdata have introduced database changes which
> > > cannot be read by old code. Currently, I am building tzdata in the old
> > > ("rearguard") format to keep compatibility, but at this point we're
> > > *way* behind upstream and we really should update our code. Given how
> > > long it's been though, it's going to be a bit of work.
> >
> > When I updated localtime.cc back in 2012, I tried to keep it in a format
> > which allows further updates from the NetBSD version later on.
> >
> > The last localtime.c update in NetBSD is from 2019. That should be
> > sufficient, shouldn't it?
> >
> > The upstream localtime.c diff from version 1.72 to current 1.122 is
> > 3K lines of code, so it's still a lot of work, probably...
>
> I can take this on. I've looked at the current NetBSD code diffed against
> the version we use: there's a fair amount of prototype rejiggering and
> recoding of localized areas. New code too, of course. I've done this kind
> of thing before and this project seems doable to me.
Sounds good to me. I started with this yesterday but didn't make a lot
of progress, see below. I'd be happy if you like to take over.
> I assume I can bring the current NetBSD code directly into Cygwin? In a
> legal sense, I mean.
Yes, that's perfectly fine, given the BSD license.
> Code-wise I see what Yaakov's suggested and it seems
> like a great way to go.
Yesterday eve I was already looking into this and given how NetBSD
is still under CVS control, I decided trying to pull our localtime.cc
up from 1.72 to 1.122 version by version, just to be really careful.
I managed to get up to 1.83 and stumbled over a big problem in terms
of TZ data format.
Cygwin has a builtin binary representation of the file "posixrules" in
tz_posixrules.h. Since 2000. And unchanged since 2000!
This binary representation is used as posixrules data if the posixrules
file doesn't exist or is unreadable. I have a vague feeling that this
data is hopelessly outdated and, probably, the format changed as well.
So I assume the data in tz_posixrules.h needs either an update, or
we drop the inline data entirely.
Dropping this inline data shouldn't be much of a problem, right?
Cygwin installations shouldn't need it and 3PPs can easily provide
a posixrules file, I guess...
Mark, Yaakov, what's your stance in terms of this posixrules data?
> The other question I have is, once I believe I've got it incorporated into
> Cygwin, what can I use to test that it's operating correctly?
Uhm... Yaakov?
Thanks,
Corinna
--
Corinna Vinschen
Cygwin Maintainer
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