GHC 7.8 release status

[Luite Stegeman]

I've updated the wiki page, expanding the descriptions and adding code from
the actual implementation: http://ghc.haskell.org/trac/ghc/wiki/Ghc/Hooks
An demo program that uses all hooks here:
https://gist.github.com/luite/6444273
(I've listed the users (or proposers) of every hook, and how they use it,
Thomas / Edsko, can you check that they indeed do what you need?)
The patch is here:
https://github.com/ghcjs/ghcjs-build/blob/master/refs/patches/ghc-hooks.patch

In addition to defining the heterogeneous map and the hooks themselves,
extra exports have been added to make it possible for users to actually
make a hook implementation without copying most of the module's source
code. The demo program implements all hooks to check this.

Also the GHCJS patch is here:

https://github.com/ghcjs/ghcjs-build/blob/master/refs/patches/ghc-ghcjs.patch

It adds the following:
- in DynFlags an extra WayCustom constructor to add a custom 'tag' to
generated files (GHCJS builds multiple architectures to support Template
Haskell among other things, one with the 'js' tag)
- in ForeignCall the JavaScriptCallConv calling convention
- in Platform an ArchJavaScript architecture
- `foreign import javascript' support in the parser and lexer
- The JavaScriptFFI extension that enables the `foreign import javascript'
syntax, only supported on ArchJavaScript (So using it on a regular GHC
would always result in a compile error saying that it's unsupported on the
user's platform)

luite


On Thu, Sep 5, 2013 at 12:17 AM, Thomas Schilling
<nominolo at googlemail.com>wrote:

> I started a wiki page at: http://ghc.haskell.org/trac/ghc/wiki/Ghc/Hooks
>
> Luite: could you please fill in the hooks that your latest patch defines?
>
>
> On 4 Sep 2013, at 19:40, Simon Peyton-Jones <simonpj at microsoft.com> wrote:
>
> > I do need more than a patch, please, please.  A wiki page explaining the
> design, as seen by the user (of the GHC API), the problems it solves, and
> the use-cases it enables, would be most helpful.
> >
> > Simon
> >
> > | -----Original Message-----
> > | From: Thomas Schilling [mailto:nominolo at googlemail.com]
> > | Sent: 04 September 2013 17:26
> > | To: Simon Peyton-Jones; Luite Stegeman
> > | Cc: Nicolas Frisby; "Pedro Magalhães (dreixel at gmail.com)"; Richard
> > | Eisenberg (eir at cis.upenn.edu); Geoffrey Mainland
> > | (mainland at cs.drexel.edu); Iavor Diatchki; Austin Seipp; Edsko de
> Vries;
> > | Ryan Newton (rrnewton at gmail.com); David Luposchainsky; ghc-
> > | devs at haskell.org
> > | Subject: Re: GHC 7.8 release status
> > |
> > |
> > | On 4 Sep 2013, at 15:52, Simon Peyton-Jones <simonpj at microsoft.com>
> > | wrote:
> > |
> > | >  Edsko/Thomas/Luite: if you want anything for 7.8 it'll have to be
> > | jolly soon.  At the moment I don't even know the motivation or design,
> > | let alone implementation.  Could you make a wiki page explaining the
> > | proposed design?  Is it really important to do this for 7.8?
> > |
> > | Yes, it is quite important to get this into 7.8.  Not having these
> > | features in GHC makes it very difficult for people to adopt GHCJS.  One
> > | could argue that GHCJS is not yet production-ready anyway and users
> that
> > | want to try it can figure out building GHC from source to use it, but
> > | this doesn't quite apply.
> > |
> > |  1. GHCJS targets a wider audience than users brave enough to compile
> > | GHC from source. In addition, the next chance to get these features
> into
> > | GHC is in a year from now, so when GHCJS becomes more mature then this
> > | will be a major hurdle for adoption.
> > |
> > |  2. These changes are also required for IDE tools which really mustn't
> > | require users to build a custom version of GHC.
> > |
> > |
> > | Luite's design is actually very flexible.  It simply allows GHC API
> > | users to provide functions that are called instead of (or in addition
> > | to) existing functions in GHC.  Instead of calling, say, "genHardCode",
> > | the driver now looks up whether the user has specified a hook for
> > | genHardCode and calls that instead.
> > |
> > | Currently we only specify a small number of hooks that are sufficient
> > | for our use cases.  Future releases of GHC can be extended to include
> > | more hooks, if that is needed.
> > |
> > | Hooks are stored as an untyped map inside the DynFlags (to avoid issues
> > | with circular dependencies).  Each hook is looked up using a single-
> > | constructor type and type families are used to make this type safe.
> > | There is one use of unsafeCoerce to avoid having to make every hook
> > | function an instance of Typeable.
> > |
> > | Unlike CorePlugins, it is only a GHC API feature, and users cannot
> > | specify plugins to be added via command line options.  If we can come
> up
> > | with a good design, then we could add this in GHC 7.10, but it is not
> > | necessary at this point.
> > |
> > | Luite: Do you have a link to your latest patch?
>
>
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