March 2015 - Glasgow-haskell-users

Discovery of source dependencies without --make
by Lars Hupel 13 Dec '15

13 Dec '15

(cross-posted from [haskell-cafe]) Hi, I've got a problem in our – admittedly complex – build process. We're running an automated grading system for student-submitted homework exercises. The compilation proceeds in stages: 1) Compile a library file, marked as trustworthy 2) Compile student submissions using Safe Haskell, able to access a whitelisted set of packages and the previously compiled library files 3) Compile the test suite 4) Link everything together into an executable The invocation is similar to this: ghc -c -outputdir "$OUT" -XTrustworthy Library.hs ghc -c -outputdir "$OUT" -i"$OUT" -XSafe "$SUBMISSION" ghc -c -outputdir "$OUT" -i"$OUT" Test_Suite.hs ghc -outputdir "$OUT" -i"$OUT" -o "$OUT/runner" The second stage works well under the assumption that there's just one single submitted file. If there's more than one, I need to specify them in topological order wrt their module dependencies. Consider two simple modules: A.hs > module A where > > import B > import Library B.hs > module B where Invoking GHC with "A.hs" "B.hs" will fail: A.hs:3:1: Failed to load interface for ‘B’ My naive attempt at solving that problem was to just insert "--make" into the compiler flags. No luck, because according to [1, §4.7.3], "--make" will only look at source files and will ignore the "Library.hi" file from the previous compilation stage. If I give the path to "Library.hs" as well, GHC insists on recompiling it with changed flags ("-XSafe" instead of "-XTrustworthy"). Reading a bit further, I discovered the '-M' flag, however, not only does it output Makefile-formatted output, it also ignores .hi files. Is there any way to get the dependency discovery of '--make' without the rest? I know I could probably make it work if I made a package out of the first build stage, but I really want to avoid that in order to not increase the build complexity even further. Cheers Lars [1] <https://downloads.haskell.org/~ghc/7.6.3/docs/html/users_guide/separate-com…>

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Typed splices and type checking
by J. Garrett Morris 08 Apr '15

08 Apr '15

Hello, I've run into another misunderstanding with Template Haskell and typed splices. For example, I was hoping to use typed splices to generate earlier errors from Printf. Here's the world's least handy printf: > class Printf t > where printf :: String -> Q (TExp String) -> Q (TExp t) > > instance Printf String > where printf s t | '%' `notElem` s = [|| $$t ++ s ||] > | otherwise = fail ("Unexpected format %" > ++ [c]) > where (_, _:c:_) = break ('%' ==) s > > instance Printf t => Printf (Char -> t) > where printf s t > | c /= 'c' = fail ("Unexpected format %" ++ [c] ++ > " for character") > | otherwise = [|| \c -> $$(printf s'' > [|| $$t ++ s' ++ [c] ||]) > ||] > where (s', '%':c:s'') = break ('%' ==) s Now, consider these two definitions: > f :: Char -> String > f = $$(printf "foo %c" [||""||]) > h :: Char -> String > h y = $$(printf "foo %c" [||""||]) y I would have expected these to be equivalent, from a type checking perspective. However, while the first types fine, the second generates the error message: > Printing.hs:14:12: > No instance for (Printf t0) arising from a use of `printf' > The type variable `t0' is ambiguous > Note: there are several potential instances: > instance Printf t => Printf (Char -> t) > -- Defined at Printf.hs:20:10 > instance Printf String -- Defined at Printf.hs:9:10 > In the expression: printf "foo %c" [|| "" ||] > In the Template Haskell splice > $$(printf "foo %c" [|| "" ||]) > In the expression: $$(printf "foo %c" [|| "" ||]) Should I have anticipated this? Ought the interaction of typed splices and eta-expansion be problematic? /g -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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SHA256SUMS file for GHC 7.4.2
by Andrés Sicard-Ramírez 31 Mar '15

31 Mar '15

Hi, For GHC 7.10.1 or GHC 7.8.4 I could find the SHA256SUMS files in http://downloads.haskell.org/~ghc/7.10.1/ and http://downloads.haskell.org/~ghc/7.8.4/, respectively. The SHA256SUMS file for GHC 7.4.2 isn't in http://downloads.haskell.org/~ghc/7.4.2/. Where can I find this file? Thanks, -- Andrés

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Re: Welcome, and getting started
by John Wiegley 31 Mar '15

31 Mar '15

>>>>> Neil Mitchell <ndmitchell(a)gmail.com> writes: > Is the ability to generate dlls with both shared and non-shared RTS's a > feature of dynamic linking? At Standard Chartered we build non-shared > (static) dlls on Windows 32bit and shared-RTS dlls/sos on Linux 64bit. Both > are essential to us. I believe for your scenario you would use: Windows: -shared Linux: -dynamic -shared This is from http://www.vex.net/~trebla/haskell/so.xhtml. John

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Re: Welcome, and getting started
by John Wiegley 31 Mar '15

31 Mar '15

>>>>> Simon Marlow <marlowsd(a)gmail.com> writes: > Perhaps some of this would be solved by switching to -dynamic by default for > everything, but there are performance issues with that. Some of these performance issues are documented at: https://ghc.haskell.org/trac/ghc/wiki/DynamicByDefault John

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Parallel Profiling
by Dominic Steinitz 30 Mar '15

30 Mar '15

Does anyone know of any tools for analysing parallel program performance? I am trying to use threadscope but it keeps crashing with my 100M log file and ghc-events-analyze is not going to help as I have many hundreds of threads all carrying out the same computation. I think I’d like a library that would allow me to construct my own analyses rather than display them via GTK. There is ghc-events but that seems to be just for parsing the logs and I couldn’t find anything that used it in the way I would like to (apart from threadscope and ghc-events-analyze of course). Thanks Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com

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ANNOUNCE: GHC version 7.10.1
by Austin Seipp 27 Mar '15

27 Mar '15

============================================================== The (Interactive) Glasgow Haskell Compiler -- version 7.10.1 ============================================================== The GHC Team is pleased to announce a new major release of GHC. There have been a number of significant changes since the last major release, including: * Several new language features and changes have been implemented: - Applicative is now a superclass of Monad and in the Prelude. - Many prelude combinators have been generalized - Static pointers * GHC now has preliminary and experimental support for DWARF based debugging. * `integer-gmp` has been completely rewritten. * Type-checking plugins can now extend the type checker. * Support for partial type signatures * Many bugfixes and other performance improvements. * Preliminary support for 'backpack' features like signatures. * Typeable is now generated by default for all data types automatically. We've also fixed a handful of issues reported since RC3: - A bug in the call arity analysis that would result in invalid core was fixed (#10176) - A bug in the Win32 package causing it to fail to load was fixed (#10165) - ghc-prim has (correctly) been bumped to version 0.4.0.0, to comply with the PVP. - Several libraries have been bumped to their latest available versions after coordination. The full release notes are here: https://downloads.haskell.org/~ghc/7.10.1/docs/html/users_guide/release-7-1… How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: https://www.haskell.org/ghc/ We supply binary builds in the native package format for many platforms, and the source distribution is available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ GHC developers' home page http://ghc.haskell.org/trac/ghc/ Haskell home page http://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, is here: https://ghc.haskell.org/trac/ghc/wiki/Platforms https://ghc.haskell.org/trac/ghc/wiki/CodeOwners Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: https://ghc.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC's developer's site run by Trac: https://ghc.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at https://www.haskell.org/mailman/listinfo/glasgow-haskell-users https://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see https://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: https://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: https://www.haskell.org/ghc/reportabug Hashes & Signatures ~~~~~~~~~~~~~~~~~ On https://downloads.haskell.org/~ghc/7.10.1/ you will find a signed copy of the SHA256 hashes for the tarballs, using my GPG key (0F8F 3AA9 9235 C704 ADA0 B419 B942 AEE5 3B58 D86F). -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Splices returning splices
by J. Garrett Morris 23 Mar '15

23 Mar '15

Hello, I'm attempting to write a quasiquoter with relatively full antiquotation support. In doing so, I've arrived at I think an odd problem: the expression grammar in Language.Haskell.TH.Syntax doesn't seem to include splices. This seems to mean that my antiquotations can't themselves include splices, which is quite limiting. Am I misinterpreting? The type system in "Template metaprogramming for Haskell" seems to imply no such restriction on the occurrences of splices. (As an additional complication: what I really need to do is return typed splices; my "quasiquoter" relies on its expected type to determine its behavior. However, this seems like an uninteresting extension of the above problem.) Thanks, /g -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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ANNOUNCE: GHC 7.10.1 Release Candidate 3
by Austin Seipp 19 Mar '15

19 Mar '15

We are pleased to announce the third release candidate for GHC 7.10.1: https://downloads.haskell.org/~ghc/7.10.1-rc3 https://downloads.haskell.org/~ghc/7.10.1-rc3/docs/html/ This includes the source tarball and bindists for Windows and Debian Linux. FreeBSD, CentOS and Mac OS X binary distributions will follow soon. These binaries and tarballs have an accompanying SHA256SUMS file signed by my GPG key id (0x3B58D86F). We plan to make the 7.10.1 final release at the end of this week - so please test as much as possible; bugs are much cheaper if we find them before the release! The list of issues we plan on fixing can always be found in an up-to-date form here: https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-7.10.1 -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Re: ANNOUNCE: GHC 7.10.1 Release Candidate 3
by Miëtek Bak 17 Mar '15

17 Mar '15

As I wrote previously — the bindist name does mention ‘deb7’, so perhaps this is all working as intended, and perhaps supporting such ancient distributions is not actually needed. However, the GHC 7.8.4, 7.8.3, and 7.8.2 bindists work fine with glibc 2.11, so this is a regression. -- Miëtek On 2015-03-17, at 08:25, Herbert Valerio Riedel <hvriedel(a)gmail.com> wrote: > On 2015-03-17 at 03:09:23 +0100, Miëtek Bak wrote: >> As with 7.10.1-rc2, installation fails on CentOS 6 (i386), Debian 6, and Ubuntu 10.04 LTS, in one of two following ways — >> >> 1. On i386: >> >> "utils/ghc-cabal/dist-install/build/tmp/ghc-cabal-bindist" copy libraries/ghc-prim dist-install "strip" '' '/app/ghc' '/app/ghc/lib/ghc-7.10.0.20150316' '/app/ghc/share/doc/ghc/html/libraries' 'v p dyn' >> ghc-cabal/dist-install/build/tmp/ghc-cabal: symbol lookup error: libraries/integer-gmp2/dist-install/build/libHSinteger-gmp-1.0.0.0-6zeGtnFHpaVBJ80QaL9uVu-ghc7.10.0.20150316.so: undefined symbol: __gmpn_ior_n > > Well, it shouldn't be very surprising that the deb7 (wheezy) ghc bindist > doesn't work on deb6 (squeeze), as it's been compile-time configured for > the environment provided by deb7 which has newer libraries with more > features/symbols. > > So what's needed here is probably a 2nd linux bindist build on an > ancient enough (i.e. the one with the oldest libraries among > CentOS6/Deb6/Ubuntu10.04) Linux environment.

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