aarch64 support

That's the only "big" architecture that's still missing

I've been working on stabilizing AArch64 (ghc/ghc#16796 (closed)) in hopes that ghc%8.8.1 can finally ship with defensible support. Do you have any sense for which distributions would be most useful to produce bindists for? Currently we build for Debian 9.

IMO, there should be a set of distros for which:

1. ALL ghc versions have bindists
2. ALL arches have bindists

Otherwise it's hard to know for tools like ghcup whether the user can install version x.y.z on his distro on his current arch. We would need a much more complicated .available-versions format.

This also made it hard to bump the "recommended" version for GHC, because 8.6.5 does not have a FreeBSD bindist, but older versions have.

IMO, there should be a set of distros for which:

1. ALL ghc versions have bindists
2. ALL arches have bindists

While this is a great goal, I'm afraid it is really more than we can commit to supporting until we have more hands to help with CI (and perhaps more hardware, for that matter; pushing out a release already takes on the order of days).

For instance, a reasonably dense configuration matrix would be,

• Fedora 29
• Fedora 30
• Debian stable
• Debian testing
• Ubuntu 16.04
• Ubuntu 18.04
• Ubuntu 19.04
• CentOS 7
• FreeBSD 11
• FreeBSD 12?
• Alpine?

[cartesian product]

• i386
• x86_64
• ARMv7
• AArch64

[cartesian product]

• Standard
• DWARF-enabled
• integer-simple

That is over 100 binary distributions. However, there is a tremendous amount of overlap from the perspective of ABI compatibility (as computed by this little hack):

glibc-2.17 gmp-6.0 ncurses-5.9	["CentOS 7"]
glibc-2.19 gmp-6.0 ncurses-5.9	["Debian oldstable"]
glibc-2.23 gmp-6.1 ncurses-6.0	["Ubuntu 16.04 (xenial)"]
glibc-2.24 gmp-6.1 ncurses-6.0	["Debian stable"]
glibc-2.26 gmp-6.1 ncurses-6.0	["Fedora 27"]
glibc-2.27 gmp-6.1 ncurses-6.1	["Fedora 28","Ubuntu 18.04 (bionic)"]
glibc-2.28 gmp-6.1 ncurses-6.1	["Debian testing","Fedora 29","Ubuntu 18.10 (cosmic)"]
glibc-2.29 gmp-6.1 ncurses-6.1	["Fedora 30","Ubuntu 19.04 (disco)"]

So, what were 12 configurations turn into eight. Moreover, glibc maintains backwards compatibility: the Bionic bindist could likely be used on Fedora 28, Debian testing, Fedora 29, Cosmic, Fedora 30 and Disco. Now you are down to six bindists. So, without even trying we cut the size of our configuration space in half; this seems well worth exploiting, even if it does cost a bit of complexity.

This also made it hard to bump the "recommended" version for GHC, because 8.6.5 does not have a FreeBSD bindist, but older versions have.

Yes, I am working on bringing up FreeBSD support under the new CI scheme.

Yes I think that sums up the problems:

1. libc
2. gmp
3. ncurses
4. maybe libffi

DWARF and integer-simple are irrelevant for ghcup I'd say.

Everything except 1. is kinda fixable by static linking (gmp ofc a bit more peculiar).

Then we really only have two builds. One for musl, one for glibc.