On 01/05/14 14:48, Dominick Samperi wrote:
The problem with some graphics libraries used via FFI (and other libraries
that are not thread-safe), if I understand the situation correctly, is that ghci
forks a thread when it shouldn't, causing some programs to miscalculate
the available stack space (because they think there is only one thread).
>
The new dynamic linking support and the flag -fno-ghci-sandbox fixes
this problem, and I would not vote for the removal of these features.
So I understand how -fno-ghci-sandbox avoids problems with GUI libraries
that use thread-local state. But how is dynamic linking involved here?
What improved in GHC 7.8 relative to 7.6 for you? And could you
clarify "miscalculate the available stack space"? What needs to
calculate stack space? Why? C stack space?
We can certainly make a smoother experience around -fno-ghci-sandbox for
using GUI libraries.
It is not clear to me from Simon's original post how linking to all of
those C++ libs can continue to work if dynamic linking is removed
in 7.10? Perhaps I misunderstand what you mean by "revert to
static linking"?
When I say "revert to static linking" I mean make GHCi static linked,
and have it load Haskell code compiled for static linking using the RTS
linker (like it did in 7.6). Foreign libraries would still be loaded
using the system linker, as they always have been.
To be clear, I'm not officially proposing that we drop dynamic linking,
but I think it's worthwhile exploring the design space again, given that
we know dynamic linking has been tougher than we expected.
Cheers,
Simon
Thanks,
Dominick
On Wed, Apr 30, 2014 at 9:26 PM, George Colpitts
<george.colpi...@gmail.com> 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 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
On Wed, Apr 30, 2014 at 1:45 PM, Simon Marlow <marlo...@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, and then we'll see
where we stand.
Cheers,
Simon
On Tue, Apr 29, 2014 at 6:13 PM, Simon Peyton Jones
<simo...@microsoft.com <mailto:simo...@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____
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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