GHC 7.4.2 on Ubuntu Trusty

[Yitzchak Gale]

I wrote:
>> This thread makes it clear what a mess
>> we have inherited from the days when GHC was primarily a
>> research compiler. Let's face it - GHC is now also a serious
>> production compiler, and this urgently needs to be cleaned up.

hvr wrote:
> Are you referring to the GMP dependency or something else?
> ...I'm not sure what can be done differently here.

Agreed. No, not any one of those many little details. I mean
the general extreme difficulty of getting almost any version
of GHC working on almost any platform, unless the two
were released within a fairly short time of each other.

Well, that is, not counting your wonderful ppa for Ubuntu.
That is fantastic - but the dire need for it is evidence for
the severity of the problem.

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.

I realize that this might be disruptive to GHC devs, because
as a compiler with a research heritage, GHC experiments with
its own new features on its own source code. But as a compiler
that is used commercially, some general kind of backward
portability is critically important.

The other direction is equally problematic. Although
GHC does support bootstrapping itself from a few previous
releases, porting GHC to a new platform has become harder
and harder as GHC becomes more complex. I think this could
become a threat to the viability of GHC - technology is always
changing.

As a commercial developer, I am always plagued by nagging
worry about GHC portability, forward and backward. Will we
always be able in the future to support code we release, or will
it die someday because there will no longer exist a GHC able
to compile it? Will our whole technology die someday just
because we can't get GHC working on a platform we need
to support?

Thanks,
Yitz