Lars Ingebrigtsen wrote:

> I don't have access to a Fedora system to test on

"make check" works for me on Fedora 30 again; thanks.

> Hm...  Since GnuTLS no longer supports compression at all, I would have
> assumed that on newer OS versions this would be a NOOP.

Yes, the newer GnuTLS implementations are stub functions that are marked 
obsolescent, which causes GCC to warn when you compile code calling them, and if 
--enable-gcc-warnings is used this caused the Emacs build to fail. The fix I 
installed was to call these obsolescent functions only in older GnuTLS versions, 
where they are not obsolescent.

Come to think of it, Emacs shouldn't make the :compression feature visible on 
newer-GnuTLS systems, since the feature is obsolescent and just clutters up the 
runtime and data. So I installed the attached patch, which causes this feature 
(and the :encrypt-then-mac feature) to be exported to the Lisp level only if the 
underlying GnuTLS library supports the feature. This gives a bit more info to 
the Lisp code (if it wants it) and simplifies the data and the low-level code 
slightly.