Re: Remote GHCi

Simon, As Sumit said, we use dynCompileExpr for core functionality of IHaskell. I am not really sure how the change you are proposing affects that, though. We use dynCompileExpr in several places for evaluation inside the interpreter context: 1. Evaluating a Haskell expression in the interpreter context, converting the result to a ByteString, then using fromDynamic to extract the bytestring and convert it to a value in the compiled context. 2. Getting a file handle from the interpreter context to the compiled context; this does not actually use dynCompileExpr because there were some bugs with dynCompileExpr and so I had to literally copy source from InteractiveEval to reimplement parts of dynCompileExpr (unrelated: the issue was that dyncompileexpr imported and then unimported Data.Dynamic, and this messed with data declarations that had already been created in the interpreter context) 3. Extracting IO a values from the interpreted context to the compiled context so that they could be run; this is necessary to get displayed values from the interpreter back to the compiled code. I think two of our uses, which are both very central to the way IHaskell works, would be impacted by requiring a Binary instance (or similar), which is what I think you are proposing (since we have two uses at least where we marshall `IO x` values via dynCompileExpr, which cannot be serialized, I believe.) I am sure that there are alternative ways to do what we are doing, but they are probably not simple and would take quite a bit of work. -- Andrew On Tue, Nov 17, 2015 at 6:29 AM, Richard Eisenberg wrote:

How does this interact with typechecker plugins? I assume they would still happen in GHC's process.

I've also been thinking about designing and implementing a mechanisms where programmers could specify custom pretty-printers for their types, and GHC would use these pretty-printers in error messages. This action would also probably need to be in the same process.

Would either of these ideas be affected? My guess is "no", because we should be able to be selective in what gets farmed out to the second process and what stays locally.

Richard

On Nov 17, 2015, at 5:10 AM, Simon Marlow wrote:

...

Hi folks - I've been thinking about changing the way we run interpreted code so that it would be run in a separate process. It turns out this has quite a few benefits, and would let us kill some of the really awkward hacks we have in GHC to work around problems that arise because we're running interpreted code and the compiler on the same runtime.

I summarised the idea here: https://ghc.haskell.org/trac/ghc/wiki/RemoteGHCi

I'd be interested to hear if anyone has any thoughts around this, particularly if doing this would make your life difficult in some way. Are people relying on dynCompileExpr for anything?

Cheers, Simon _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

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