FYI: upstream asn1c progress

[Harald Welte]

Hi all,

upstream asn1c (https://github.com/vlm/asn1c) has made significant
progress in 2017.  It now has basic support for information object
classes, and while doing some S1AP related test I also could compile an
unmodified RANAP ASN.1 syntax from osmo-iuh.git commit
8f2fb0cca5f990b26478e9ec1207fa1e39e691eb - i.e. before all the various
rewrites and hacks that we added to make it pass the much older asn1c
that we were using at the time.

In case anyone wants to play with this, I've had success with asn1c up
to git commit
https://github.com/vlm/asn1c/commit/e700b208bc0b252c85390a80ee63f3687fb2d970
until
https://github.com/vlm/asn1c/commit/ea6635bdae9667bcf6111a25d896c556c946c11a
unfortunately introduces a regression that's tracked in
https://github.com/vlm/asn1c/issues/185

Resolving that regression seems like it requires quite a bit of insight
into asn1c internals, which nobody in Osmocom currently has.

What's still missing from upstream is APER support.  Sadly, he
maintainer @vlm states clearly that APER is not a short-term goal for
him.  However, ss UPER is supported, and there's the somewhat incomplete
Eurecom/OAI hacks (with our fixes on top) as well as work in the
following pull-request https://github.com/vlm/asn1c/pull/125 I don't
think that's such a big issue anymore.  It would be best to create
somewhat of a test suite and then get the APER code up to a state until
it passes that test suite.  I'd be happy to put some of my (or sysmocom
developer) time into that.

But assuming that the regression parsing/compiling the ASN.1 syntax can
somehow be fixed, I think there's some clear "light at the end of the
tunnel" that we could compile the 3GPP syntax for RUA, HNBAP, RANAP and
S1AP as-is, without first rewriting it, and without the asn1tostruct.py
hack.

Regards,
	Harald
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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