GHC status report

[Simon Marlow]

On 01/05/2014 02:26, George Colpitts wrote:
> To elaborate, in the past, I had a lot of problems using libraries from
> the ghci prompt on the Mac but I haven't tried recently.
>
> As an example, on the web page
> <http://www.cs.yale.edu/homes/hudak/SOE/software1.htm> for the book the
> Haskell School of Expression it says:
>
>     Note for OS X users: running graphics applications from GHCi is no
>     longer supported. Instead, one has to compile a graphics program
>     using GHC in order to run it (see example/GMIExamples.lhs for an
>     example).
>
> I had similar problems using the Yale Euterpea music program from ghci.
> When I inquired I was referred to
> https://ghc.haskell.org/trac/ghc/ticket/4244 and
> https://ghc.haskell.org/trac/ghc/ticket/781. I see that the latter is
> now scheduled for 7.10.1

I think we just punted on all the problems and assumed that dynamic 
linking would fix everything.  What we've found is that dynamic linking 
causes a whole new set of problems and complexities.  Meanwhile, many of 
the original problems have been fixed (except #781, which is kind of 
unfixable, but fortunately is also quite rare).

Unfortunately dynamic linking is needed to support GHCi and TH on 
unregisterised platforms.  In 7.8, GHCi and TH now works on some 
platforms where it didn't before (albeit not very widely used platforms).

Cheers,
Simon


>
> On Wed, Apr 30, 2014 at 1:45 PM, Simon Marlow <marlowsd at gmail.com
> <mailto:marlowsd at gmail.com>> wrote:
>
>     On 30/04/2014 01:35, George Colpitts wrote:
>
>         It doesn't have anything about the dynamic linking changes made
>         for 7.8.
>         I think it's worth mentioning the improvements we expect to get from
>         that. The highlights of the release notes do mention it, so
>         maybe that
>         suffices.
>
>         In particular, I'm hoping that it is going to fix a lot of
>         problems with
>         using foreign libraries such as OpenGL from ghci. I could be
>         wrong about
>         that though.
>
>
>     I'd like to understand more about what those problems are.  As a
>     data point, at Facebook we're using static linking (I compiled GHC
>     with DYNAMIC_GHC_PROGRAMS=NO), we're loading upwards of 50 3rd-party
>     C++ libraries and one gigantic shared library consisting of a ton of
>     in-house C++ code, together with all our Haskell code into GHCi, and
>     it works perfectly.  The key to using the static linker is to not
>     use it for C++ code - you want all your external C++ code in shared
>     libraries and load those using the system linker.
>
>     Dynamic linking has been a huge headache in GHC, and it's not clear
>     that it's an overall improvement compared with the static linker.
>       Now that 7.8 is out of the way, it's time to have a conversation
>     about whether we want to do dynamic linking again for 7.10, or
>     revert to static linking.  I think Austin is going to update
>     https://ghc.haskell.org/trac/__ghc/wiki/DynamicGhcPrograms
>     <https://ghc.haskell.org/trac/ghc/wiki/DynamicGhcPrograms>, and then
>     we'll see where we stand.
>
>     Cheers,
>     Simon
>
>
>
>
>         On Tue, Apr 29, 2014 at 6:13 PM, Simon Peyton Jones
>         <simonpj at microsoft.com <mailto:simonpj at microsoft.com>
>         <mailto:simonpj at microsoft.com <mailto:simonpj at microsoft.com>>__>
>         wrote:
>
>              As Austin has told us, there’s a draft of the *GHC Status
>         Report for
>              the HCAR*, here:____
>
>         https://ghc.haskell.org/trac/__ghc/wiki/Status/May14____
>         <https://ghc.haskell.org/trac/ghc/wiki/Status/May14____>
>
>
>              Have we missed out something  you have been working hard
>         on?  Do
>              take a moment to add a bullet in an appropriate place (it’s a
>              wiki).  I’d like to be sure that we are giving credit to
>         all the
>              appropriate people, so please help us fix that too.  GHC is
>         a team
>              effort.____
>
>              Deadline is 1 May I think.____
>
>              Thanks____
>
>              Simon____
>
>              __ __
>
>
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