What is the state of play with 64-bit D?

[dsimcha]

== Quote from Derek (ddparnell at bigpond.com)'s article
> I've been out of the 'loop' with D for quite awhile now so I haven't been
> keeping up with current developments.
> I will have a need for a decent 64-bit compiled language soon and I was
> wondering how close D is away from this.

DMD now has a 64-bit codegen that works quite well (well enough for serious use,
no showstopper bugs) on Linux.  This has been around since 2.052, released last
February.  It also supports 64-bit on FreeBSD, though I don't know how well that
works because I've never tried it.  On Windows and Mac OS, 64-bit isn't supported.
 On Windows this is because Optlink (the linker DMD uses on Windows) doesn't work
with 64-bit objects.  On Mac OS, I don't know what the bottleneck is.

GDC has also been improving rapidly and is, as far as I can tell, one showstopper
bug
(https://bitbucket.org/goshawk/gdc/issue/226/gc-from-spawned-threads-segfaults-on-64)
away from being usable for serious work on Linux x64.  It already seems usable in
32-bit mode.  There's been some work towards porting it to Windows, but that's
somewhat behind the curve.  The Windows version only supports an ancient front-end
release and 64-bit Windows support is buggy.

LDC is a release behind DMD and GDC, so I haven't been following it.  It's
supposed to support 64-bit Linux, though.