Re: Updated GnuTLS from MSYS2 and Emacs's `dynamic-library-alist'

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 30 Apr 2015 13:46:37 +0200
> From: Alexander Shukaev <haroogan@gmail.com>
> 
> Recently, the GnuTLS from MSYS2 has been updated to the 3.4 version. As a
> result, the name of corresponding DLL has changed. Currently to
> "libgnutls-30.dll", but maybe it's a mistake and we will change it to
> "libgnutls-34.dll".

It's not a mistake.  The "30" part is not coming from the version of
the package, it is a combination of the ABI version and the "age"
value.  If you are interested in this stuff (you shouldn't be, it has
no meaning for humans), read the GnuTLS configuration files, they
explain how "30" is computed.

> In any case, currently Emacs has the following GnuTLS
> setting in the `dynamic-library-alist':
> 
>     (gnutls "libgnutls-28.dll" "libgnutls-26.dll")

Only if you are looking at an old git checkout, or at Emacs 24.5.  The
current git HEAD already has a fix for this change.

> What would be your recommendation to properly add new versions of GnuTLS?

It requires changes on the C level, due to ABI incompatibility.  See
the changes mad in this commit:

  commit dc79845aac339db1cdcbbfc48d8f1569ed9a5aa2
  Author: Chris Zheng <chriszheng99@gmail.com>
  Date:   Sat Apr 11 18:06:52 2015 +0300

      Support GnuTLS v3.4 and later on MS-Windows

      * src/gnutls.c (syms_of_gnutls) <libgnutls-version>: New DEFSYM.
      * lisp/term/w32-win.el (dynamic-library-alist): Determine which
      GnuTLS DLL to load according to value of libgnutls-version.

      Fixes: bug#20294

> Upstream or should I create a custom MSYS2 patch? Note that aside from Git
> version, we also support release versions such as 24.5, and it seems like a
> patch is inevitable in this case right?

Stefan decided not to release any more 24.x versions, unless there's
some crucial bug or issue with 24.5, so we currently don't see any
reason to release a patched 24.x.  In fact, AFAIU, this latest version
of GnuTLS is not stable enough yet to recommend it for general
population, and AFIR even had some minor security issues.  So I think
users of Emacs 24.5 will be better off using the 3.3 series of GnuTLS.