bug#14380: 24.3; `network-stream-open-tls' fails in some imap servers on w32

[Ted Zlatanov <tzz@lifelogs.com>]

On Fri, 10 May 2013 21:44:12 +0100 João Távora <joaotavora@gmail.com> wrote: 

JT> Honestly I thought builtin tls was some kind of tls library in elisp.
JT> Needing external libraries doesn't make it very builtin :-), but
JT> that's just my opinion.

Implementing TLS in ELisp is possible, sure, but it would be extremely
slow and there's considerable risk in reimplementing that protocol.  We
chose to use GnuTLS instead, which is a fast reliable C implementation
and is available for W32 and all our other platforms.

JT> In any case, my description shows how it "almost worked" with whatever
JT> tls client it found (it was probably cygwin's, but I didn't check).
JT> You might want to avoid these bug reports by fixing it the way I
JT> suggested or some other way. Or not. All is OK from my part.

I've seen dozens of bugs related to "almost working" external TLS
binaries on all platforms.  It was one of the reasons I did the initial
GnuTLS integration with Emacs.  My vote is to require GnuTLS with Emacs
and to only support it, but there are some questions there, mainly for
W32 and Mac OS X: do we auto-update GnuTLS?  What happens when the
GnuTLS we install conflicts with another system install?  And so on...

Ted