June 2015 - ghc-devs - Haskell.org

RE: [Diffusion] [Build Failed] rGHCc45f8ceb0de0: Elaborate test for Trac #10403
by Simon Peyton Jones 19 Jun '15

19 Jun '15

I think 4945 is failing again -- although not on my machine. Can someone mark it expect_broken again? I'm on a train S | -----Original Message----- | From: noreply(a)phabricator.haskell.org | [mailto:noreply@phabricator.haskell.org] | Sent: 19 June 2015 00:09 | To: Simon Peyton Jones | Subject: [Diffusion] [Build Failed] rGHCc45f8ceb0de0: Elaborate test for | Trac #10403 | | Harbormaster failed to build B4473: rGHCc45f8ceb0de0: Elaborate test for | Trac #10403! | | BRANCHES | master | | USERS | simonpj (Author) | GHC - Testsuite (Auditor) | | COMMIT | https://phabricator.haskell.org/rGHCc45f8ceb0de0 | | EMAIL PREFERENCES | https://phabricator.haskell.org/settings/panel/emailpreferences/ | | To: simonpj, GHC - Testsuite

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missing file
by Simon Peyton Jones 18 Jun '15

18 Jun '15

I'm getting validate failures on HEAD. Missing file perhaps? Simon Unexpected failures: llvm/should_compile T8131b [exit code non-0] (optllvm) <command line>: does not exist: T8131b.cmm

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RE: [commit: ghc] master: Update submodule process to master (c1dc421)
by Simon Peyton Jones 17 Jun '15

17 Jun '15

Thomas | Update submodule process to master | | This allows a warning free build on Windows, and thus an error free | validate. I was excited about this, because GHC has not validated on Windows for ages and ages. But I get the following failures, with HEAD, on 32-bit Windows. I can get more details if you like. I'd LOVE someone to fix these failures. thanks Simon Unexpected passes: driver T2507 (normal) driver T8959a (normal) rts T5250 (normal) rts rdynamic (normal) Unexpected failures: ../../libraries/base/tests/System Timeout001 [bad exit code] (normal) codeGen/should_compile T10518 [exit code non-0] (normal) codeGen/should_fail T8131 [stderr mismatch] (normal) ghci/scripts T5975a [bad stderr] (ghci) perf/haddock haddock.Cabal [[Errno 2] No such file or directory: './perf/haddock/../../../../libraries/Cabal/Cabal/dist-install/haddock.t'] (normal) perf/haddock haddock.base [[Errno 2] No such file or directory: './perf/haddock/../../../../libraries/base/dist-install/haddock.t'] (normal) perf/haddock haddock.compiler [[Errno 2] No such file or directory: './perf/haddock/../../../../compiler/stage2/haddock.t'] (normal) rts outofmem [bad stderr] (normal) Unexpected stat failures: perf/compiler T3294 [stat too good] (normal) perf/compiler T5030 [stat too good] (normal) perf/compiler T5837 [stat too good] (normal) perf/compiler T9961 [stat too good] (normal) perf/should_run T9203 [stat not good enough] (normal) perf/compiler T5321Fun [stat not good enough] (normal) perf/compiler T783 [stat not good enough] (normal) perf/compiler T9675 [stat not good enough] (optasm) perf/compiler T9872d [stat not good enough] (normal) | -----Original Message----- | From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf Of | git(a)git.haskell.org | Sent: 11 June 2015 18:30 | To: ghc-commits(a)haskell.org | Subject: [commit: ghc] master: Update submodule process to master | (c1dc421) | | Repository : ssh://git@git.haskell.org/ghc | | On branch : master | Link : | http://ghc.haskell.org/trac/ghc/changeset/c1dc4216efc3db1a8fbd56a658981b5 | 3b7e42eda/ghc | | >--------------------------------------------------------------- | | commit c1dc4216efc3db1a8fbd56a658981b53b7e42eda | Author: Thomas Miedema <thomasmiedema(a)gmail.com> | Date: Thu Jun 11 19:24:25 2015 +0200 | | Update submodule process to master | | This allows a warning free build on Windows, and thus an error free | validate. | | | >--------------------------------------------------------------- | | c1dc4216efc3db1a8fbd56a658981b53b7e42eda | libraries/process | 2 +- | 1 file changed, 1 insertion(+), 1 deletion(-) | | diff --git a/libraries/process b/libraries/process | index 67efaf5..e0983fb 160000 | --- a/libraries/process | +++ b/libraries/process | @@ -1 +1 @@ | -Subproject commit 67efaf599a03f454a98a3905820ce40aa80825c7 | +Subproject commit e0983fbbfa8a3d81c7b99e83a3169fc686caab62 | | _______________________________________________ | ghc-commits mailing list | ghc-commits(a)haskell.org | http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-commits

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Re: [GHC] #10537: Parser: commas_tup_tail returns spurious "Missing" value
by Alan & Kim Zimmerman 17 Jun '15

17 Jun '15

So it appears the `Missing` item is correct, but it has been given the wrong SrcSpan. Originally it was a `noLoc`. I think I will just advance the column by one, then it is actually correct, and the annotation lookup will only succeed for the first one, so it will all just work. On Wed, Jun 17, 2015 at 5:14 PM, GHC <ghc-devs(a)haskell.org> wrote: > #10537: Parser: commas_tup_tail returns spurious "Missing" value > -------------------------------------+------------------------------------- > Reporter: alanz | Owner: alanz > Type: bug | Status: new > Priority: normal | Milestone: 7.10.2 > Component: Compiler | Version: 7.10.1 > (Parser) | Keywords: > Resolution: | Architecture: > Operating System: Unknown/Multiple | Unknown/Multiple > Type of failure: None/Unknown | Test Case: > Blocked By: | Blocking: > Related Tickets: | Differential Revisions: > -------------------------------------+------------------------------------- > > Comment (by mpickering): > > I think you're right Simon. There is something wrong with the annotations > though, firstly both the Missing elements have the same SrcSpan `L > tests/examples/Tuple.hs:3:24`. > > {{{ > ((tests/examples/Tuple.hs:3:8, AnnComma), > [tests/examples/Tuple.hs:3:9]), > ((tests/examples/Tuple.hs:3:11-17, AnnComma), > [tests/examples/Tuple.hs:3:18]), > ((tests/examples/Tuple.hs:3:20-22, AnnComma), > [tests/examples/Tuple.hs:3:23]), > ((tests/examples/Tuple.hs:3:24, AnnComma), > [tests/examples/Tuple.hs:3:24]), > }}} > > Here are the relevant annotations. Notice how the first three commas are > associated with the preceding item (much like they are for lists) but the > last one is associated directly with the `Missing`. As both `Missing`s > have the same SrcSpan then this is causing duplicated output in `ghc- > exactprint`. > > -- > Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10537#comment:2> > GHC <http://www.haskell.org/ghc/> > The Glasgow Haskell Compiler >

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Validate failures on 7.10 branch
by Simon Peyton Jones 17 Jun '15

17 Jun '15

On a fresh build of the 7.10 branch, I get five validate failures on Linux. They are below. Is this only me? Simon Unexpected failures: driver T8959a [bad stderr] (normal) th T10279 [stderr mismatch] (normal) typecheck/should_fail T10534 [stderr mismatch] (normal) Unexpected stat failures: perf/should_run T4830 [stat not good enough] (normal) perf/should_run T7436 [stat not good enough] (normal)

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MonadFail proposal (MFP): Moving fail out of Monad
by David Luposchainsky 17 Jun '15

17 Jun '15

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello *, the subject says it all. After we successfully put `=>` into Monad, it is time to remove something in return: `fail`. Like with the AMP, I wrote up the proposal in Markdown format on Github, which you can find below as a URL, and in verbatim copy at the end of this email. It provides an overview over the intended outcome, which design decisions we had to take, and how our initial plan for the transition looks like. There are also some issues left open to discussion. https://github.com/quchen/articles/blob/master/monad_fail.md Here's a short abstract: - - Move `fail` from `Monad` into a new class `MonadFail`. - - Code using failable patterns will receive a more restrictive `MonadFail` constraint. Code without this constraint will be safe to use for all Monads. - - Transition will take at least two GHC releases. GHC 7.12 will include the new class, and generate warnings asking users to make their failable patterns compliant. - - Stackage showed an upper bound of less than 500 breaking code fragments when compiled with the new desugaring. For more details, refer to the link or the paste at the end. Let's get going! David aka quchen =============================================================== =============================================================== =============================================================== `MonadFail` proposal (MFP) ========================== A couple of years ago, we proposed to make `Applicative` a superclass of `Monad`, which successfully killed the single most ugly thing in Haskell as of GHC 7.10. Now, it's time to tackle the other major issue with `Monad`: `fail` being a part of it. You can contact me as usual via IRC/Freenode as *quchen*, or by email to *dluposchainsky at the email service of Google*. This file will also be posted on the ghc-devs@ and libraries@ mailing lists, as well as on Reddit. Overview - -------- - - **The problem** - reason for the proposal - - **MonadFail class** - the solution - - **Discussion** - explaining our design choices - - **Adapting old code** - how to prepare current code to transition smoothly - - **Esimating the breakage** - how much stuff we will break (spoiler: not much) - - **Transitional strategy** - how to break as little as possible while transitioning - - **Current status** The problem - ----------- Currently, the `<-` symbol is unconditionally desugared as follows: ```haskell do pat <- computation >>> let f pat = more more >>> f _ = fail "..." >>> in computation >>= f ``` The problem with this is that `fail` cannot (!) be sensibly implemented for many monads, for example `State`, `IO`, `Reader`. In those cases it defaults to `error`. As a consequence, in current Haskell, you can not use `Monad`-polymorphic code safely, because although it claims to work for all `Monad`s, it might just crash on you. This kind of implicit non-totality baked into the class is *terrible*. The goal of this proposal is adding the `fail` only when necessary and reflecting that in the type signature of the `do` block, so that it can be used safely, and more importantly, is guaranteed not to be used if the type signature does not say so. `MonadFail` class - ----------------- To fix this, introduce a new typeclass: ```haskell class Monad m => MonadFail m where fail :: String -> m a ``` Desugaring can now be changed to produce this constraint when necessary. For this, we have to decide when a pattern match can not fail; if this is the case, we can omit inserting the `fail` call. The most trivial examples of unfailable patterns are of course those that match anywhere unconditionally, ```haskell do x <- action >>> let f x = more more >>> in action >>= f ``` In particular, the programmer can assert any pattern be unfailable by making it irrefutable using a prefix tilde: ```haskell do ~pat <- action >>> let f ~pat = more more >>> in action >>= f ``` A class of patterns that are conditionally failable are `newtype`s, and single constructor `data` types, which are unfailable by themselves, but may fail if matching on their fields is done with failable paterns. ```haskell data Newtype a = Newtype a - -- "x" cannot fail do Newtype x <- action >>> let f (Newtype x) = more more >>> in action >>= f - -- "Just x" can fail do Newtype (Just x) <- action >>> let f (Newtype (Just x)) = more more >>> f _ = fail "..." >>> in action >>= f ``` `ViewPatterns` are as failable as the pattern the view is matched against. Patterns like `(Just -> Just x)` should generate a `MonadFail` constraint even when it's "obvious" from the view's implementation that the pattern will always match. From an implementor's perspective, this means that only types (and their constructors) have to be looked at, not arbitrary values (like functions), which is impossible to do statically in general. ```haskell do (view -> pat) <- action >>> let f (view -> pat) = more more >>> f _ = fail "..." >>> in action >>= f do (view -> ~pat) <- action >>> let f (view -> ~pat) = more more >>> in action >>= f ``` A similar issue arises for `PatternSynonyms`, which we cannot inspect during compilation sufficiently. A pattern synonym will therefore always be considered failable. ```haskell do PatternSynonym x <- action >>> let f PatternSynonym x = more more >>> in f _ = fail "..." >>> in action >>= f ``` Discussion - ---------- - - Although for many `MonadPlus` `fail _ = mzero`, a separate `MonadFail` class should be created instead of just using that. - A parser might fail with an error message involving positional information. Some libraries, like `Binary`, provide `fail` as their only interface to fail a decoding step. - Although `STM` is `MonadPlus`, it uses the default `fail = error`. It will therefore not get a `MonadFail` instance. - - What laws should `fail` follow? **Left zero**, ```haskell ∀ s f. fail s >>= f ≡ fail s ``` A call to `fail` should abort the computation. In this sense, `fail` would become a close relative of `mzero`. It would work well with the common definition `fail _ = mzero`, and give a simple guideline to the intended usage and effect of the `MonadFail` class. - - Rename `fail`? **No.** Old code might use `fail` explicitly and we might avoid breaking it, the Report talks about `fail`, and we have a solid migration strategy that does not require a renaming. - - Remove the `String` argument? **No.** The `String` might help error reporting and debugging. `String` may be ugly, but it's the de facto standard for simple text in GHC. No high performance string operations are to be expected with `fail`, so this breaking change would in no way be justified. Also note that explicit `fail` calls would break if we removed the argument. - - How sensitive would existing code be to subtle changes in the strictness behaviour of `do` notation pattern matching? **It doesn't.** The implementation does not affect strictness at all, only the desugaring step. Care must be taken when fixing warnings by making patterns irrefutable using `~`, as that *does* affect strictness. (Cf. difference between lazy/strict State) - - The `Monad` constraint for `MonadFail` seems unnecessary. Should we drop or relax it? What other things should be considered? - Applicative `do` notation is coming sooner or later, `fail` might be useful in this more general scenario. Due to the AMP, it is trivial to change the `MonadFail` superclass to `Applicative` later. (The name will be a bit misleading, but it's a very small price to pay.) - The class might be misused for a strange pointed type if left without any constraint. This is not the intended use at all. I think we should keep the `Monad` superclass for three main reasons: - We don't want to see `(Monad m, MonadFail m) =>` all over the place. - The primary intended use of `fail` is for desugaring do-notation anyway. - Retroactively removing superclasses is easy, but adding them is hard (see AMP). Adapting old code - ----------------- - - Help! My code is broken because of a missing `MonadFail` instance! *Here are your options:* 1. Write a `MonadFail` instance (and bring it into scope) ```haskell #if !MIN_VERSION_base(4,11,0) -- Control.Monad.Fail import will become redundant in GHC 7.16+ import qualified Control.Monad.Fail as Fail #endif import Control.Monad instance Monad Foo where (>>=) = <...bind impl...> -- NB: `return` defaults to `pure` #if !MIN_VERSION_base(4,11,0) -- Monad(fail) will be removed in GHC 7.16+ fail = Fail.fail #endif instance MonadFail Foo where fail = <...fail implementation...> ``` 2. Change your pattern to be irrefutable 3. Emulate the old behaviour by desugaring the pattern match by hand: ```haskell do Left e <- foobar stuff ``` becomes ```haskell do x <- foobar e <- case foobar of Left e' -> e' Right r -> error "Pattern match failed" -- Boooo stuff ``` The point is you'll have to do your dirty laundry yourself now if you have a value that *you* know will always match, and if you don't handle the other patterns you'll get incompleteness warnings, and the compiler won't silently eat those for you. - - Help! My code is broken because you removed `fail` from `Monad`, but my class defines it! *Delete that part of the instance definition.* Esimating the breakage - ---------------------- Using our initial implementation, I compiled stackage-nightly, and grepped the logs for found "invalid use of fail desugaring". Assuming my implementation is correct, the number of "missing `MonadFail`" warnings generated is 487. Note that I filtered out `[]`, `Maybe` and `ReadPrec`, since those can be given a `MonadFail` instance from within GHC, and no breakage is expected from them. The build logs can be found [here][stackage-logs]. Search for "failable pattern" to find your way to the still pretty raw warnings. Transitional strategy - --------------------- The roadmap is similar to the [AMP][amp], the main difference being that since `MonadFail` does not exist yet, we have to introduce new functionality and then switch to it. * **GHC 7.12 / base-4.9** - Add module `Control.Monad.Fail` with new class `MonadFail(fail)` so people can start writing instances for it. `Control.Monad` only re-exports the class `MonadFail`, but not its `fail` method. NB: At this point, `Control.Monad.Fail.fail` clashes with `Prelude.fail` and `Control.Monad.fail`. - *(non-essential)* Add a language extension `-XMonadFail` that changes desugaring to use `MonadFail(fail)` instead of `Monad(fail)`. This has the effect that typechecking will infer a `MonadFail` constraint for `do` blocks with failable patterns, just as it is planned to do when the entire thing is done. - Warn when a `do`-block that contains a failable pattern is desugared, but there is no `MonadFail`-instance in scope: "Please add the instance or change your pattern matching." Add a flag to control whether this warning appears. - Warn when an instance implements the `fail` function (or when `fail` is imported as a method of `Monad`), as it will be removed from the `Monad` class in the future. (See also [GHC #10071][trac-10071]) 3. GHC 7.14 - Switch `-XMonadFail` on by default. - Remove the desugaring warnings. 3. GHC 7.16 - Remove `-XMonadFail`, leaving its effects on at all times. - Remove `fail` from `Monad`. - Instead, re-export `Control.Monad.Fail.fail` as `Prelude.fail` and `Control.Monad.fail`. - `Control.Monad.Fail` is now a redundant module that can be considered deprecated. Current status - -------------- - - [ZuriHac 2015 (29.5. - 31.5.)][zurihac]: Franz Thoma (@fmthoma) and me (David Luposchainsky aka @quchen) started implementing the MFP in GHC. - Desugaring to the new `fail` can be controlled via a new langauge extension, `MonadFailDesugaring`. - If the language extension is turned off, a warning will be emitted for code that would break if it was enabled. - Warnings are emitted for types that *have* a *MonadFail* instance. This still needs to be fixed. - The error message are readable, but should be more so. We're still on this. - - 2015-06-09: Estimated breakage by compiling Stackage. Smaller than expected. [amp]: https://github.com/quchen/articles/blob/master/applicative_monad.md [stackage-logs]: https://www.dropbox.com/s/knz0i979skam4zs/stackage-build.tar.xz?dl=0 [trac-10071]: https://ghc.haskell.org/trac/ghc/ticket/10071 [zurihac]: https://wiki.haskell.org/ZuriHac2015 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJVd0/yAAoJELrQsaT5WQUshbUH/A3W0itVAk7ao8rtxId5unCJ 7StriKVkTyLAkkrbRJngM4MHEKiCsoyIgr8kBIwSHgk194GxeP2NCF4ijuBZoDBt +Uci+6BCBinV8+OzfrfTcJb4+8iw1j+eLWJ/Nz/JDMDNCiyzyC0SMsqGa+ssOz7H /2mqPkQjQgpHuP5PTRLHKPPIsayCQvTbZR1f14KhuMN2SPDE+WY4rqugu//XuIkN u1YssIf5l8mEez/1ljaqGL55cTI0UNg2z0iA0bFl/ajHaeQ6mc5BAevWfSohAMW7 7PIt13p9NIaMHnikmI+YJszm2IEaXuv47mGgbyDV//nHq3fwWN+naB+1mPX2eSU= =vPAL -----END PGP SIGNATURE-----

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Broken build: Documentation mistake
by Páli Gábor János 17 Jun '15

17 Jun '15

Hello there, Looks like there is some problem with one of the recent changes to The User's Guide source code as it cannot be built any more [1] (since about June 4). Here is the error message, hopefully it helps with fixing the cause: [..] Build users_guide.ps latex failed users_guide.tex:15584: Cannot determine size of graphic in docs/users_guide//prof_scc.png (no BoundingBox). users_guide.tex:15584: leading text: ...width=645pt,height=428pt]{prof_scc.png} Unexpected error occured [ -f docs/users_guide/users_guide.ps ] docs/users_guide/ghc.mk:26: recipe for target 'docs/users_guide/users_guide.ps' failed gmake[1]: *** [docs/users_guide/users_guide.ps] Error 1 Makefile:102: recipe for target 'all' failed gmake: *** [all] Error 2 Thanks, Gábor [1] http://haskell.inf.elte.hu/builders/freebsd-amd64-head/652/10.html

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Problem about `DerivedConstants.h` and `tmp.c` in `includes/dist-derivedconstants/header`, GHC 7.8.3
by Zhen Zhang 16 Jun '15

16 Jun '15

Hi everyone, I am having trouble porting some 6.8.2 GHC code to 7.8.3 GHC. The main trouble I met is that, in 6.8.2, there is a includes/mkDerivedConstants.c and some constants about RTS are declared here. While in 7.8.3, there is only a similar `includes/dist-derivedconstants/header` directory containing a bunch of code. Some seems generated like `DerivedConstants.h`, and it seems like `tmp.c` generated this. However, when I added some entries in `tmp.c` and compiled it, then it became the original version ... So I doubted that if there is another file which is equivalent to the includes/mkDerivedConstants.c in 6.8.2? Thank a lot! Zhen

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ANNOUNCE: GHC 7.10.2 Release Candidate 1
by Austin Seipp 15 Jun '15

15 Jun '15

We are pleased to announce the first release candidate for GHC 7.10.2: https://downloads.haskell.org/~ghc/7.10.2-rc1 https://downloads.haskell.org/~ghc/7.10.2-rc1/docs/html/ This includes the source tarball and bindists for Windows, Mac OS X, and Debian Linux. FreeBSD and Solaris binaries will follow soon. These binaries and tarballs have an accompanying SHA256SUMS file signed by my GPG key id (0x3B58D86F). We plan to make the 7.10.2 final release at the end of this coming week - so please test as much as possible; bugs are much cheaper if we find them before the release! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Re: ANNOUNCE: GHC 7.10.2 Release Candidate 1
by Austin Seipp 15 Jun '15

15 Jun '15

Yes, as noted on the ticket, I've bumped the priority and we'll be looking into this - and hopefully have a fix in time for 7.10.2. There are some similar tickets where we get large explosions of terms, so it may be in the same ballpark. On Sun, Jun 14, 2015 at 11:18 PM, Rob Everest <robertce(a)cse.unsw.edu.au> wrote: >> We plan to make the 7.10.2 final release at the end of this coming week - >> so please test as much as possible; bugs are much cheaper if we find them >> before the release! > > > Could I possibly draw attention to #10491? It's a regression in the > simplifier that is causing considerable pain for Accelerate, namely a > compile time of many hours for a 300 line module. It would be unfortunate if > this couldn't be resolved for the 7.10.2 release. -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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