GHC 7.4.2 on Ubuntu Trusty

[Edward Z. Yang]

Hey guys,

I have a local branch of ghc-7.8 which can be compiled by 7.10.
The most annoying patch that needed to be backported was AMP
adjustment changes.  I also messed up some stuff involving LANGUAGE
pragmas which I am going to go back and clean up.

    https://github.com/ezyang/ghc/tree/ghc-7.8

There are also some changes to hoopl, transformers and hpc (mostly
because their bootstrap libraries.)

Unfortunately I can't easily Phab these changes.  Any suggestions
for how to coordinate landing these changes?

Edward

Excerpts from Yitzchak Gale's message of 2014-12-28 13:38:47 -0500:
> Resurrecting this thread:
> 
> My impression was that Edward's suggestion was a simple and
> obvious solution to the problem of previous GHC versions quickly
> becoming orphaned and unbuildable. But Austin thought that this
> thread was stuck.
> 
> Would Edward's suggestion be difficult to implement for any
> reason? Specifically, right now would be the time to do it, and
> it would mean:
> 
> 1. Create a 7.8.5 branch.
> 2. Tweak the stage 1 Haskell sources to build with 7.10 and tag
> 3. Create only a source tarball and upload it to the download
> site
> 
> Thanks,
> Yitz
> 
> On Wed, Oct 29, 2014 at 12:10 AM, Edward Z. Yang wrote:
> > Excerpts from Yitzchak Gale's message of 2014-10-28 13:58:08 -0700:
> >> How about this: Currently, every GHC source distribution
> >> requires no later than its own version of GHC for bootstrapping.
> >> Going backwards, that chops up the sequence of GHC versions
> >> into tiny incompatible pieces - there is no way to start with a
> >> working GHC and work backwards to an older version by compiling
> >> successively older GHC sources.
> >>
> >> If instead each GHC could be compiled using at least one
> >> subsequent version, the chain would not be broken. I.e.,
> >> always provide a compatibility flag or some other reasonably
> >> simple mechanism that would enable the current GHC to
> >> compile the source code of at least the last previous released
> >> version.
> >
> > Here is an alternate proposal: when we make a new major version release,
> > we should also make a minor version release of the previous series, which
> > is prepped so that it can compile from the new major version.  If it
> > is the case that one version of the compiler can compile any other
> > version in the same series, this would be sufficient to go backwards.
> >
> > Concretely, the action plan is very simple too: take 7.6 and apply as
> > many patches as is necessary to make it compile from 7.8, and cut
> > a release with those patches.
> >
> > Edward