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Cross-compiling Template Haskell via -fexternal-interpreter and IPC
by Alberto Valverde 30 May '17

30 May '17

Hello, I'm trying to put together a GHC 8.0.1 cross-compiler with Template Haskell support. Initially to target Windows (32bits) from a Linux host but a similar procedure should enable to target other platforms too. I'd like to contribute the patches back so I'm asking for advice on how to implement it in order to increase the chances of them being accepted. I've managed to get a working stage 1 cross-compiler with some patches which correctly builds all stage1 libs and GHC + stage 2 compiler and ghc-iserv.exe. However, compiling TH by using wine and ghc-iserver.exe fails because the file descriptor ids that GHC passes as arguments to "wine ghc-iserv.exe" don't make sense in the emulated windows world. I've hacked around this to test the feasibility of the approach by using stdin/stdout instead of creating new pipes and, surprisingly, managed to cross-compile a simple Template Haskell program. I'm considering using a socket for communicating between both processes as a more permanent solution but this would incur in a dependency on the "network" package. Would this be acceptable? Named pipes have also crossed my mind but I'm not sure how well they're supported by wine. Thanks for your attention. Alberto P.S: Code is in the "cross-mingw-hacks" branches of these repositories and is based on the ghc-8.0.1-release tag: https://github.com/albertov/ghc https://github.com/albertov/hsc2hs A Docker image script here that builds it is here: https://github.com/albertov/ghc-cross-compiler-windows-x86

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Finding out if a binding is externally visible
by Sebastian Graf 29 May '17

29 May '17

Hi all, I'm tinkering around with GHCs Call Arity Analysis and Demand Analysis as part of my Master's thesis. The usage analysis part is what I'm interested in in particular. After quite some time spent debugging absent errors, I noticed that certain top-level bindings aren't exported, but still visible in other modules through generated RULE pragmas (e.g. through class instance specialization). These bindings were considered absent in my combined analysis, explaining the very sporadic absent errors I was getting. Is there some function that tells me if an identifier is 'externally visible' in that sense? I think https://downloads.haskell.org/~ghc/8.0.1/docs/html/libraries/ghc-8.0.1/GHC.… is what I'm after, but I want to be sure. Does that function already work when the Ids are still local? Greetings, Sebastian

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RE: [commit: ghc] master: Fix test output after 'Some tidying up of type pretty-printing' (09d5c99)
by Simon Peyton Jones 28 May '17

28 May '17

Sorry about this. I carefully fixed all these and validated...thanks for fixing Simon | -----Original Message----- | From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf Of | git(a)git.haskell.org | Sent: 27 May 2017 15:45 | To: ghc-commits(a)haskell.org | Subject: [commit: ghc] master: Fix test output after 'Some tidying up of | type pretty-printing' (09d5c99) | | Repository : ssh://git@git.haskell.org/ghc | | On branch : master | Link : | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fghc.haske | ll.org%2Ftrac%2Fghc%2Fchangeset%2F09d5c993aae208e3d34a9e715297922b6ea42b3 | f%2Fghc&data=02%7C01%7Csimonpj%40microsoft.com%7Ca2a237b8dabd42f3684f08d4 | a50ef9ad%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636314931129891311& | sdata=VM04DE0U1RBSmJjbV6vCwu8LPvyqwqfo2K1I03W1cW4%3D&reserved=0 | | >--------------------------------------------------------------- | | commit 09d5c993aae208e3d34a9e715297922b6ea42b3f | Author: Bartosz Nitka <niteria(a)gmail.com> | Date: Sat May 27 07:42:26 2017 -0700 | | Fix test output after 'Some tidying up of type pretty-printing' | | Most are cosmetic. There's an interesting change in T7861, | but the error is still accurate. | | | >--------------------------------------------------------------- | | 09d5c993aae208e3d34a9e715297922b6ea42b3f | testsuite/tests/typecheck/should_run/T7861.stderr | 6 +----- | testsuite/tests/typecheck/should_run/Typeable1.stderr | 2 +- | testsuite/tests/typecheck/should_run/tcrun045.stderr | 6 +++--- | 3 files changed, 5 insertions(+), 9 deletions(-) | | diff --git a/testsuite/tests/typecheck/should_run/T7861.stderr | b/testsuite/tests/typecheck/should_run/T7861.stderr | index e9ee5e9..4a1c030 100644 | --- a/testsuite/tests/typecheck/should_run/T7861.stderr | +++ b/testsuite/tests/typecheck/should_run/T7861.stderr | @@ -1,9 +1,5 @@ | T7861: T7861.hs:10:5: error: | - • Couldn't match type ‘a’ with ‘[a]’ | - ‘a’ is a rigid type variable bound by | - the type signature for: | - f :: forall a. (forall b. a) -> a | - at T7861.hs:9:1-23 | + • Occurs check: cannot construct the infinite type: a ~ [a] | Expected type: (forall b. a) -> a | Actual type: (forall b. a) -> [a] | • In the expression: doA | diff --git a/testsuite/tests/typecheck/should_run/Typeable1.stderr | b/testsuite/tests/typecheck/should_run/Typeable1.stderr | index 9a7d3b7..65f6fd4 100644 | --- a/testsuite/tests/typecheck/should_run/Typeable1.stderr | +++ b/testsuite/tests/typecheck/should_run/Typeable1.stderr | @@ -7,7 +7,7 @@ Typeable1.hs:22:5: error: | App :: forall k2 (t :: k2). | () => | forall k1 (a :: k1 -> k2) (b :: k1). | - t ~ a b => | + (t ~ a b) => | TypeRep a -> TypeRep b -> TypeRep t, | in a pattern binding in | 'do' block | diff --git a/testsuite/tests/typecheck/should_run/tcrun045.stderr | b/testsuite/tests/typecheck/should_run/tcrun045.stderr | index 19fca10..f6b1652 100644 | --- a/testsuite/tests/typecheck/should_run/tcrun045.stderr | +++ b/testsuite/tests/typecheck/should_run/tcrun045.stderr | @@ -1,18 +1,18 @@ | | tcrun045.hs:11:10: error: | • Illegal implicit parameter ‘?imp::Int’ | - • In the context: (?imp::Int) | + • In the context: ?imp::Int | While checking an instance declaration | In the instance declaration for ‘C Int’ | | tcrun045.hs:24:1: error: | • Illegal implicit parameter ‘?imp::Int’ | - • In the context: (?imp::Int) | + • In the context: ?imp::Int | While checking the super-classes of class ‘D’ | In the class declaration for ‘D’ | | tcrun045.hs:27:10: error: | • Illegal implicit parameter ‘?imp::Int’ | - • In the context: (?imp::Int) | + • In the context: ?imp::Int | While checking an instance declaration | In the instance declaration for ‘D Int’ | | _______________________________________________ | ghc-commits mailing list | ghc-commits(a)haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.hask | ell.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc- | commits&data=02%7C01%7Csimonpj%40microsoft.com%7Ca2a237b8dabd42f3684f08d4 | a50ef9ad%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636314931129891311& | sdata=MYdcDMAQcDnFVFlc0aNT1NXPHFa%2FT%2FSpNiDIu4hrvOY%3D&reserved=0

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HsParTy
by Simon Peyton Jones 28 May '17

28 May '17

Alan Do you know why HsTypes.ppr_mono_ty contains any uses of 'maybeParen'? Shouldn't the parens all be put in by HsParTy? I tripped over this when I mistakenly added what I thought were missing maybeParen calls for HsAppTy and HsAppTys, but that was flagged as an error by a test in tests/printer. So why are there /any/ maybeParen calls? Simon

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Status of ircbfowse
by Takenobu Tani 28 May '17

28 May '17

Dear devs, Does anyone know about the operational status of ircbrowse[1]? Recently, it has been stopped all the time. Did that useful service end? [1]: http://ircbrowse.net/ Regards, Takenobu

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Re: [ANNOUNCE] GHC 8.2.1 release candidate 2
by Ryan Scott 26 May '17

26 May '17

Alberto, > I've manage to reproduce the CK bug without any external dependencies and > opened a ticket with an attached module that fails to compile with > 8.2.1-rc2 (w/o explicit KindSignature) but compiles fine with 8.0.2. Thanks for doing this! > Will hopefully follow up soon with the Cabal issues I'm experiencing One thing that might be useful to do is to invoke Cabal with high verbosity (e.g., -v3) and post the logs somewhere. I wouldn't be surprised if Nix was passing some uncommonly used flags that have regressed in recent versions of Cabal. Ryan S.

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RE: Trees that Grow in the hsSyn AST
by David Feuer 26 May '17

26 May '17

I haven't looked in detail yet, but there seem to be good ideas. I have two questions: 1. Which is better to start with: HsSyn or Core? Intuition suggests this sort of thing could be very helpful for making zapping more reliable and ensuring its efficiency, but there may be better reasons to start with HsSyn. 2. If we're making intrusive changes to representations, would now be a sensible era to consider switching to a different variable representation (unbound, bound, abt, etc)? David FeuerWell-Typed, LLP -------- Original message --------From: Simon Peyton Jones via ghc-devs <ghc-devs(a)haskell.org> Date: 5/25/17 6:48 PM (GMT-05:00) To: Alan & Kim Zimmerman <alan.zimm(a)gmail.com>, ghc-devs(a)haskell.org Subject: RE: Trees that Grow in the hsSyn AST Folks Do take a look at this: · We propose to re-engineer HsSyn itself. This will touch a lot of code. · But it’s very neat, and will bring big long-term advantages · And we can do it a bit at a time The wiki page https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow has the details. It’s entirely an internal change, not a change to GHC’s specification, so it’s independent of the GHC proposals process. But I’d value the opinion of other GHC devs. Alan has done a prototype first step, which worked out rather well. Rather than having HsExpr Id (which we all know means “HsExpr after the typechecker” but tha’s a bit inexplicit, we have HsExpr GhcTc meaning “HsExpr after GHC’s Tc pass”. In some ways this is quite superficial, but it unlocks the Trees That Grow machiney. Please ask questions etc. Alan and Shayan can record the answers in the wiki. I’m inclined to go ahead with this, so yell soon if you disagree. Simon From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Alan & Kim Zimmerman Sent: 24 May 2017 22:52 To: ghc-devs(a)haskell.org Subject: Trees that Grow in the hsSyn AST Hi all You may be aware that Shayan Najd presented the paper "Trees that Grow"[1] at HIW last year. Based on the following mandate > As in my previous email to Shayan (attached). Wiki page, describe goals, design, > approach. Point to prototype implementation. Seek comments. You can say that >I am supportive! > > Simon We have set up a Wiki page at [2] describing a prototype implementation of the first stage of this for the hsSyn AST, which is to change the polymorphic variable from one of RdrName / Name / Id to an index type. This is presented as a fabricator diff at [3]. Please take a look and provide feedback. Regards Alan [1] http://www.jucs.org/jucs_23_1/trees_that_grow/jucs_23_01_0042_0062_najd.pdf<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.jucs.or…> [2] https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow [3] https://phabricator.haskell.org/D3609

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Trees that Grow in the hsSyn AST
by Alan & Kim Zimmerman 25 May '17

25 May '17

Hi all You may be aware that Shayan Najd presented the paper "Trees that Grow"[1] at HIW last year. Based on the following mandate > As in my previous email to Shayan (attached). Wiki page, describe goals, design, > approach. Point to prototype implementation. Seek comments. You can say that >I am supportive! > > Simon We have set up a Wiki page at [2] describing a prototype implementation of the first stage of this for the hsSyn AST, which is to change the polymorphic variable from one of RdrName / Name / Id to an index type. This is presented as a fabricator diff at [3]. Please take a look and provide feedback. Regards Alan [1] http://www.jucs.org/jucs_23_1/trees_that_grow/jucs_23_01_0042_0062_najd.pdf [2] https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow [3] https://phabricator.haskell.org/D3609

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Type class instances in scope
by Tom Sydney Kerckhove 24 May '17

24 May '17

Dear GHC Devs. I am trying to use the GHC API as part of the work that I am doing for my thesis. Currently I am looking for a way to find all the type class instances that are in scope in a given module. Here's what I've tried: ``` getInstancesFromTcmodule :: GhcMonad m => TypecheckedModule -> m () getInstancesFromTcmodule tmod = do let (tcenv, md) = tm_internals_ tmod let insts = tcg_insts tcenv getInsts >>= printO printO $ modInfoInstances $ tm_checked_module_info tmod printO insts printO $ md_insts md printO $ tcg_inst_env tcenv printO :: (GhcMonad m, Outputable a) => a -> m () printO a = showGHC a >>= (liftIO . putStrLn) ``` Unfortunately the output that I get is empty: ``` ([], []) [] [] [] [] ``` For the record, I ran this on the following module: ``` {-# LANGUAGE NoImplicitPrelude #-} module Ints where import Prelude (Int, (+), (-)) f :: Int -> Int f x = x + 1 g :: Int -> Int g x = x - 1 double :: Int -> Int double x = x + x zero :: Int zero = 0 ``` Because I'm using '+' and '-', I definitely expect the instances of 'Num' to be available, but I am also expecting to find ALL the other instances that are available for type checking. Is there any documentation on this matter? Failing that, is there anyone who is willing to help me with this problem? Thank you for your time. -- Tom Sydney Kerckhove

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[ANNOUNCE] GHC 8.2.1 release candidate 2
by Ben Gamari 23 May '17

23 May '17

Hello everyone, The GHC team is very pleased to announce the second candidate of the 8.2.1 release of the Glasgow Haskell Compiler. Source and binary distributions are available at https://downloads.haskell.org/~ghc/8.2.1-rc2/ This is the second of what will likely be either two or three release candidates leading up the final 8.2.1 release. This release will feature, * A new type-indexed Typeable implementation * The long awaited Backpack * Deriving strategies for disambiguating DeriveAnyClass, GeneralizedNewtypeDeriving, and stock mechanisms * Overloaded record fields * Improved compiler performance * Better code generation through more robust tracking of join points * Compact regions for more efficient garbage collection and serialization * Better support for machines with non-uniform memory architectures * More robust support for levity (e.g. RuntimeRep) polymorphism * A simple interface for streaming eventlog data from live processes * Further refinement of DWARF support This candidate fixes most of the issues present in release candidate one including, * #13233: typePrimRep panic while compiling GHC with profiling enabled * #13509: type error involving unboxed tuples * #13426: compile-time memory-usage regression * #13560: Windows binary distributions carry absolute paths to toolchain * #13585: Control.Lens.Wrapped.ala causes compiler panic * #13623: Join points produce bad code for stream fusion As always, please let us know if you have difficulty. Thanks to everyone who has contributed! Happy testing, - Ben

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