June 2012 - Glasgow-haskell-users

GHC build linking error
by wren ng thornton 30 Nov '12

30 Nov '12

Hello all, I'm working on creating some distribution bundles of GHC 7.4.1 and HP 2012.2.0.0 for OSX 10.5 to help rectify the lack of support on older Macs. In building GHC I've run into a linking error in stage1: ld: duplicate symbol ___gmpz_abs in libraries/integer-gmp/gmp/objs/add.o and libraries/integer-gmp/gmp/objs/abs.o Which looks like the same issue discussed in: http://www.haskell.org/pipermail/glasgow-haskell-users/2011-December/021339… The only proposed solution was Sean mentioned explicitly passing the GMP.framework to ./configure via --with-gmp-libraries and --with-gmp-includes; however, I have no such GMP.framework (I'm building from the framework versions of GHC 6.12.1 and HP 2010.1.0.0). So, any ideas on how to fix this? -- Live well, ~wren

3 3

Installing binary tarball fails on Linux
by Johan Tibell 09 Oct '12

09 Oct '12

Hi, I tried to install the GHC 7.4.1 32-bit binary tarball today and ran into the error below. Are 32-bit GHC's not supported on 64-bit Linuxes? The error: Installing library in /usr/local/lib/ghc-7.4.1/ghc-prim-0.2.0.0 ghc-cabal: Bad interface file: dist-install/build/GHC/Classes.hi magic number mismatch: old/corrupt interface file? (wanted 33214052, got 129742) Full log: $ tar jxf ghc-7.4.1-i386-unknown-linux.tar.bz2 $ cd ghc-7.4.1/ tibell@tibell:ghc-7.4.1$ ./configure --prefix=/usr/local checking for path to top of build tree... /tmp/ghc-7.4.1 Build platform inferred as: i386-unknown-linux Host platform inferred as: i386-unknown-linux Target platform inferred as: i386-unknown-linux GHC build : i386-unknown-linux GHC host : i386-unknown-linux GHC target : i386-unknown-linux checking for perl... /usr/bin/perl checking if your perl works in shell scripts... yes checking for a BSD-compatible install... /usr/bin/install -c checking whether ln -s works... yes checking for gsed... sed checking for gcc... /usr/bin/gcc checking for gcc... /usr/bin/gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.out checking for suffix of executables... checking whether we are cross compiling... no checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether /usr/bin/gcc accepts -g... yes checking for /usr/bin/gcc option to accept ISO C89... none needed checking version of gcc... 4.4.3 checking how to run the C preprocessor... /usr/bin/gcc -E checking whether ld understands --hash-size=31... checking whether ld understands --reduce-memory-overheads... checking for extra options to pass gcc when compiling via C... -fwrapv checking Setting up CFLAGS, LDFLAGS, IGNORE_LINKER_LD_FLAGS and CPPFLAGS... done checking Setting up CONF_CC_OPTS_STAGE0, CONF_GCC_LINKER_OPTS_STAGE0, CONF_LD_LINKER_OPTS_STAGE0 and CONF_CPP_OPTS_STAGE0... done checking Setting up CONF_CC_OPTS_STAGE1, CONF_GCC_LINKER_OPTS_STAGE1, CONF_LD_LINKER_OPTS_STAGE1 and CONF_CPP_OPTS_STAGE1... done checking Setting up CONF_CC_OPTS_STAGE2, CONF_GCC_LINKER_OPTS_STAGE2, CONF_LD_LINKER_OPTS_STAGE2 and CONF_CPP_OPTS_STAGE2... done checking for .subsections_via_symbols... no checking for GNU non-executable stack support... yes checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking size of void *... 8 checking for ar... /usr/bin/ar checking whether /usr/bin/ar is GNU ar... yes checking for ar arguments... q checking whether ranlib is needed... no configure: creating ./config.status config.status: creating settings config.status: creating mk/config.mk config.status: creating mk/install.mk **************************************************** Configuration done, ready to 'make install' (see README and INSTALL files for more info.) **************************************************** $ sudo make install make -r --no-print-directory -f ghc.mk install BINDIST=YES NO_INCLUDE_DEPS=YES /usr/bin/install -c -m 755 -d "/usr/local/share/man" /usr/bin/install -c -m 755 -d "/usr/local/share/man/man1" /usr/bin/install -c -m 644 docs/man/ghc.1 "/usr/local/share/man/man1" "rm" -f driver/split/dist/ghc-split echo '#!/usr/bin/perl' >> driver/split/dist/ghc-split echo '$TARGETPLATFORM = "i386-unknown-linux";' >> driver/split/dist/ghc-split echo '$TABLES_NEXT_TO_CODE = "YES";' >> driver/split/dist/ghc-split cat driver/split/dist/ghc-split.prl >> driver/split/dist/ghc-split /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" /usr/bin/install -c -m 755 driver/split/dist/ghc-split "/usr/local/lib/ghc-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghci-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/ghci-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/ghci-7.4.1" echo 'exec "/usr/local/bin/ghc-7.4.1" --interactive ${1+"$@"}' >> "/usr/local/bin/ghci-7.4.1" chmod +x "/usr/local/bin/ghci-7.4.1" "rm" -f "/usr/local/bin/ghci" ln -s ghci-7.4.1 "/usr/local/bin/ghci" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/." && /usr/bin/install -c -m 644 includes/./*.h "/usr/local/lib/ghc-7.4.1/include/./" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/rts" && /usr/bin/install -c -m 644 includes/rts/*.h "/usr/local/lib/ghc-7.4.1/include/rts/" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/rts/prof" && /usr/bin/install -c -m 644 includes/rts/prof/*.h "/usr/local/lib/ghc-7.4.1/include/rts/prof/" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/rts/storage" && /usr/bin/install -c -m 644 includes/rts/storage/*.h "/usr/local/lib/ghc-7.4.1/include/rts/storage/" && /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include/stg" && /usr/bin/install -c -m 644 includes/stg/*.h "/usr/local/lib/ghc-7.4.1/include/stg/" && true /usr/bin/install -c -m 644 includes/ghcautoconf.h includes/ghcplatform.h includes/dist-ghcconstants/header/GHCConstants.h includes/dist-derivedconstants/header/DerivedConstants.h "/usr/local/lib/ghc-7.4.1/include/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/include" /usr/bin/install -c -m 644 rts/dist/build/ffi.h rts/dist/build/ffitarget.h "/usr/local/lib/ghc-7.4.1/include/" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/haddock-ghc-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/haddock-ghc-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'exeprog="haddock"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/haddock-ghc-7.4.1" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/haddock-ghc-7.4.1" cat utils/haddock/haddock.wrapper >> "/usr/local/bin/haddock-ghc-7.4.1" chmod +x "/usr/local/bin/haddock-ghc-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/html/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/latex/" /usr/bin/install -c -m 644 utils/haddock/html/frames.html "/usr/local/lib/ghc-7.4.1/html/" /usr/bin/install -c -m 644 utils/haddock/html/haddock-util.js "/usr/local/lib/ghc-7.4.1/html/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/haskell_icon.gif "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/minus.gif "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/plus.gif "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Classic.theme/xhaddock.css "/usr/local/lib/ghc-7.4.1/html/Classic.theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/hslogo-16.png "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/minus.gif "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/ocean.css "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/plus.gif "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/html/Ocean.std-theme/synopsis.png "/usr/local/lib/ghc-7.4.1/html/Ocean.std-theme/" /usr/bin/install -c -m 644 utils/haddock/latex/haddock.sty "/usr/local/lib/ghc-7.4.1/latex/" "rm" -f "/usr/local/bin/haddock" ln -s haddock-ghc-7.4.1 "/usr/local/bin/haddock" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/hsc2hs" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/hsc2hs" echo '#!/bin/sh' >> "/usr/local/bin/hsc2hs" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/hsc2hs" echo 'exeprog="hsc2hs"' >> "/usr/local/bin/hsc2hs" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/hsc2hs" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/hsc2hs" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/hsc2hs" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/hsc2hs" echo 'HSC2HS_EXTRA="--cflag=-fno-stack-protector "' >> "/usr/local/bin/hsc2hs" cat utils/hsc2hs/hsc2hs.wrapper >> "/usr/local/bin/hsc2hs" chmod +x "/usr/local/bin/hsc2hs" /usr/bin/install -c -m 644 utils/hsc2hs/template-hsc.h "/usr/local/lib/ghc-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghc-pkg-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/ghc-pkg-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'exeprog="ghc-pkg"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/ghc-pkg-7.4.1" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-pkg-7.4.1" cat utils/ghc-pkg/ghc-pkg.wrapper >> "/usr/local/bin/ghc-pkg-7.4.1" chmod +x "/usr/local/bin/ghc-pkg-7.4.1" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghc-pkg" ln -s ghc-pkg-7.4.1 "/usr/local/bin/ghc-pkg" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/runghc" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/runghc" echo '#!/bin/sh' >> "/usr/local/bin/runghc" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/runghc" echo 'exeprog="runghc"' >> "/usr/local/bin/runghc" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/runghc" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/runghc" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/runghc" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/runghc" cat utils/runghc/runghc.wrapper >> "/usr/local/bin/runghc" chmod +x "/usr/local/bin/runghc" "rm" -f "/usr/local/bin/runhaskell" ln -s runghc "/usr/local/bin/runhaskell" /usr/bin/install -c -m 755 -d "/usr/local/bin" "rm" -f "/usr/local/bin/ghc-7.4.1" create () { touch "$1" && chmod 755 "$1" ; } && create "/usr/local/bin/ghc-7.4.1" echo '#!/bin/sh' >> "/usr/local/bin/ghc-7.4.1" echo 'exedir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-7.4.1" echo 'exeprog="ghc-stage2"' >> "/usr/local/bin/ghc-7.4.1" echo 'executablename="$exedir/$exeprog"' >> "/usr/local/bin/ghc-7.4.1" echo 'datadir="/usr/local/share"' >> "/usr/local/bin/ghc-7.4.1" echo 'bindir="/usr/local/bin"' >> "/usr/local/bin/ghc-7.4.1" echo 'topdir="/usr/local/lib/ghc-7.4.1"' >> "/usr/local/bin/ghc-7.4.1" echo 'executablename="$exedir/ghc"' >> "/usr/local/bin/ghc-7.4.1" cat ghc/ghc.wrapper >> "/usr/local/bin/ghc-7.4.1" chmod +x "/usr/local/bin/ghc-7.4.1" "rm" -f "/usr/local/bin/ghc" ln -s ghc-7.4.1 "/usr/local/bin/ghc" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" for i in driver/ghc-usage.txt driver/ghci-usage.txt rts/dist/build/libHSrts.a rts/dist/build/libHSrts_p.a rts/dist/build/libHSrts-ghc7.4.1.so rts/dist/build/libHSrts_l.a rts/dist/build/libHSrts_debug.a rts/dist/build/libHSrts_thr.a rts/dist/build/libHSrts_thr_debug.a rts/dist/build/libHSrts_thr_l.a rts/dist/build/libHSrts_thr_p.a rts/dist/build/libHSrts_debug-ghc7.4.1.so rts/dist/build/libHSrts_thr-ghc7.4.1.so rts/dist/build/libHSrts_thr_debug-ghc7.4.1.so rts/dist/build/libffi.so rts/dist/build/libffi.so.5 rts/dist/build/libffi.so.5.0.10 settings; do \ case $i in \ *.a) \ /usr/bin/install -c -m 644 $i "/usr/local/lib/ghc-7.4.1"; \ true /usr/local/lib/ghc-7.4.1/`basename $i` ;; \ *.dll) \ /usr/bin/install -c -m 644 -s $i "/usr/local/lib/ghc-7.4.1" ;; \ *.so) \ /usr/bin/install -c -m 755 $i "/usr/local/lib/ghc-7.4.1" ;; \ *.dylib) \ /usr/bin/install -c -m 755 $i "/usr/local/lib/ghc-7.4.1";; \ *) \ /usr/bin/install -c -m 644 $i "/usr/local/lib/ghc-7.4.1"; \ esac; \ done /usr/bin/gcc -E -undef -traditional -P -DINSTALLING -DLIB_DIR='"/usr/local/lib/ghc-7.4.1"' -DINCLUDE_DIR='"/usr/local/lib/ghc-7.4.1/include"' -DPAPI_INCLUDE_DIR="" -DPAPI_LIB_DIR="" -x c -Iincludes rts/package.conf.in -o rts/package.conf.install.raw grep -v '^#pragma GCC' rts/package.conf.install.raw | sed -e 's/""//g' -e 's/:[ ]*,/: /g' >rts/package.conf.install /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" for i in utils/haddock/dist/build/tmp/haddock utils/hsc2hs/dist-install/build/tmp/hsc2hs utils/ghc-pkg/dist-install/build/tmp/ghc-pkg utils/runghc/dist-install/build/tmp/runghc ghc/stage2/build/tmp/ghc-stage2; do \ /usr/bin/install -c -m 755 $i "/usr/local/lib/ghc-7.4.1"; \ done "mv" "/usr/local/lib/ghc-7.4.1/ghc-stage2" "/usr/local/lib/ghc-7.4.1/ghc" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1" "rm" -rf "/usr/local/lib/ghc-7.4.1/package.conf.d" /usr/bin/install -c -m 755 -d "/usr/local/lib/ghc-7.4.1/package.conf.d" "/usr/local/lib/ghc-7.4.1/ghc-pkg" --force --global-conf "/usr/local/lib/ghc-7.4.1/package.conf.d" update rts/package.conf.install Reading package info from "rts/package.conf.install" ... done. "utils/ghc-cabal/dist-install/build/tmp/ghc-cabal" install "/usr/local/lib/ghc-7.4.1/ghc" "/usr/local/lib/ghc-7.4.1/ghc-pkg" "strip" "/usr/local/lib/ghc-7.4.1" libraries/ghc-prim dist-install '' '/usr/local' '/usr/local/lib/ghc-7.4.1' '/usr/local/share/doc/ghc/html/libraries' NO Installing library in /usr/local/lib/ghc-7.4.1/ghc-prim-0.2.0.0 ghc-cabal: Bad interface file: dist-install/build/GHC/Classes.hi magic number mismatch: old/corrupt interface file? (wanted 33214052, got 129742) make[1]: *** [install_packages] Error 1 make: *** [install] Error 2 -- Johan

5 8

Type operators in GHC
by Simon Peyton-Jones 19 Sep '12

19 Sep '12

Dear GHC users As part of beefing up the kind system, we plan to implement the "Type operators" proposal for Haskell Prime http://hackage.haskell.org/trac/haskell-prime/wiki/InfixTypeConstructors GHC has had type operators for some kind, so you can say data a :+: b = Left a | Right b but you can only do that for operators which start with ":". As part of the above wiki page you can see the proposal to broaden this to ALL operators, allowing data a + b = Left a | Right b Although this technically inconsistent the value page (as the wiki page discussed), I think the payoff is huge. (And "A foolish consistency is the hobgoblin of little minds", Emerson) This email is (a) to highlight the plan, and (b) to ask about flags. Our preferred approach is to *change* what -XTypeOperators does, to allow type operators that do not start with :. But that will mean that *some* (strange) programs will stop working. The only example I have seen in tc192 of GHC's test suite {-# LANGUAGE TypeOperators #-} comp :: Arrow (~>) => (b~>c, c~>d)~>(b~>d) comp = arr (uncurry (>>>)) Written more conventionally, the signature would look like comp :: Arrow arr => arr (arr b c, arr c d) (arr b d) comp = arr (uncurry (>>>)) or, in infix notation {-# LANGUAGE TypeOperators #-} comp :: Arrow arr => (b `arr` c, c `arr` d) `arr` (b `arr` d) comp = arr (uncurry (>>>)) But tc192 as it stands would become ILLEGAL, because (~>) would be a type *constructor* rather than (as now) a type *variable*. Of course it's easily fixed, as above, but still a breakage is a breakage. It would be possible to have two flags, so as to get - Haskell 98 behaviour - Current TypeOperator behaviuor - New TypeOperator behaviour but it turns out to be Quite Tiresome to do so, and I would much rather not. Can you live with that? http://chrisdone.com/posts/2010-10-07-haskelldb-and-typeoperator-madness.ht…

13 24

recent changes to hsc2hs break wrapping c++
by Evan Laforge 09 Sep '12

09 Sep '12

Recently a change was made to hsc2hs to fix this ticket: http://hackage.haskell.org/trac/ghc/ticket/2897 Unfortunately, the result is I (apparently) can't use it now. Here's how that happens: The change was to remove the dependency on HsFFI.h. However, the solution is to create a little wrapper .c file that includes wrappers around various stdio functions like fputs(). This relies on C allowing implicit casts from void* to e.g. FILE*, and is also happy to let you use undeclared functions. g++ rejects that code. And since I am calling into C++ (via a 'extern "C" { ... }' wrapper) I wind up including C++ headers that contain the structs I want hsc2hs to calculate offsets for. Of course one solution is to use C as hsc2hs expects, but it would be awkward to split my (largish) c++ program's headers into C compatible and C++ only. So meanwhile I've reverted back to an older version of hsc2hs that includes HsFFI.h. Working with c++ headers was maybe not in the original design for hsc2hs, but it's a very useful feature nonetheless. WRT HsFFI.h and the ticket, I added -I(ghc --print-libdir)/include to my hsc2hs rule a long time ago, and it wasn't very hard to do, though I admit it would have been easier had there been documentation about what to do, or a mandatory flag for the HsFFI.h path. It looks like Duncan suggested that already. Or perhaps there's a better way to wrap C++?

3 6

API function to check whether one type fits "in" another
by "Philip K. F. Hölzenspies" 23 Jul '12

23 Jul '12

L.S., I sent this to the cvs-ghc list, but was - correctly - redirected here. We're trying to write an alternative interactive front-end (alternative to ghci). This front-end is very type-driven; terms are composed not as characters on a prompt, but as applications of terms to terms. At every application of a term to another, we want to check whether the application is well typed and what type variables would have to change. Suppose I want to build the term flip fmap (+) :: Num n => ((n -> n) -> b) -> n -> b In our front-end, however, we do not need the flip; we leave unfilled holes with their type annotated, so the above would really look like this (where [[ and ]] denote a hole): fmap [[ (n -> n) -> b ]] (+) :: Num n => n -> b We start this off by asking for the types of these separate things, using GHC.exprType, giving: fmap: ForAllTy f (ForAllTy a (ForAllTy b (FunTy (TyConApp GHC.Base.Functor [TyVarTy f]) (FunTy (FunTy (TyVarTy a) (TyVarTy b)) (FunTy (AppTy (TyVarTy f) (TyVarTy a)) (AppTy (TyVarTy f) (TyVarTy b))))))) (+): ForAllTy a (FunTy (TyConApp GHC.Num.Num [TyVarTy a]) (FunTy (TyVarTy a) (FunTy (TyVarTy a) (TyVarTy a)))) (Note that 'Var' things are pretty printed to just show their name, whereas all the constructors of Type are displayed using show.) The thing that we really want to ask the GHC-API is whether (+) 'fits into' the second argument-hole of fmap, i.e. we want to know whether (type of +) ForAllTy a (FunTy (TyConApp GHC.Num.Num [TyVarTy a]) (FunTy (TyVarTy a) (FunTy (TyVarTy a) (TyVarTy a)))) fits into (type of second argument of fmap) ForAllTy f (ForAllTy a (FunTy (TyConApp GHC.Base.Functor [TyVarTy f]) (AppTy (TyVarTy f) (TyVarTy a)))) What I'm looking for is a function fitsInto :: TermType -> HoleType -> Maybe [(TyVar,Type)] I have found many functions in TcUnify / Unify / TcMatches that look somewhat like this, but in all cases they required extra arguments. When these extra arguments are filled with arbitrary values, the result is always Nothing or some sort of panic. Any pointers would be truly welcome. Regards, Philip

4 6

Occasional segfault in GHCi w/ 7.4.1-rc1 and 64bit OS X
by austin seipp 17 Jul '12

17 Jul '12

Hello GHC hackers, I have been trying the recent 7.4.1-rc1 release on my OSX Snow Leopard machine. I am using the 64bit OSX .tar.bz. I used virthualenv/hsenv to set up a virtual environment to test packages with the RC, but I discovered that GHCi seems to segfault somewhat randomly when invoked. I cannot reproduce this problem with 7.0.4 (64bit,) 7.2.2 (64bit,) or 7.5.20111223 (also 64bit.) I have invoked GHCi probably a hundred times each, and have never had it crash. I can crash the RC fairly reliably however. I looked at the shell scripts that invoke GHC and ran GDB with the proper arguments. I got a backtrace like so: $ gdb /Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219/ghc GNU gdb 6.3.50-20050815 (Apple version gdb-1518) (Sat Feb 12 02:52:12 UTC 2011) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared libraries .... done warning: Could not find object file "/Users/ian/zz64/ghc-7.4.0.20111219/rts/dist/build/libHSrts_thr.a(ffi64.o)" - no debug information available for "../src/x86/ffi64.c". warning: Could not find object file "/Users/ian/zz64/ghc-7.4.0.20111219/rts/dist/build/libHSrts_thr.a(prep_cif.o)" - no debug information available for "../src/prep_cif.c". warning: Could not find object file "/Users/ian/zz64/ghc-7.4.0.20111219/rts/dist/build/libHSrts_thr.a(types.o)" - no debug information available for "../src/types.c". (gdb) r -B/Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219 --interactive Starting program: /Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219/ghc -B/Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219 --interactive Reading symbols for shared libraries + done GHCi, version 7.4.0.20111219: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x00000000ae21cf68 0x00000001ae2060da in evacuate1 () (gdb) bt #0 0x00000001ae2060da in evacuate1 () #1 0x00000001ae20b868 in scavenge_block1 () Previous frame inner to this frame (gdb could not unwind past this frame) (gdb) So it looks like a GC bug at first glance, but I haven't done rigorous investigation. Again this doesn't happen every time - probably 1/3 the time it crashes, the other 2/3 the time it seems to work fine. This naturally also affects `runghc`. Is this a known issue? Or should I file a bug and investigate further? Perhaps something forgot to get something merged into the 7.4 branch? -- Regards, Austin

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"containing" memory-consuming computations
by Herbert Valerio Riedel 16 Jul '12

16 Jul '12

Hello GHC Devs, One issue that's been bothering me when writing Haskell programs meant to be long-running processes performing computations on external input-data in terms of an event/request-loop (think web-services, SQL-servers, or REPLs), that it is desirable to be able to limit resource-usage and be able to "contain" the effects of computations which exhausts the resource-limits (i.e. w/o crashing and burning the whole process) For the time-dimension, I'm already using functions such as System.Timeout.timeout which I can use to make sure that even a (forced) pure computation doesn't require (significantly) more wall-clock time than I expect it to. But I'm missing a similar facility for constraining the space-dimension. In some other languages such as C, I have (more or less) the ability to check for /local/ out-of-memory conditions (e.g. by checking the return value of e.g. malloc(3) for heap-allocations, or by handling an OOM exception), rollback the computation, and be able to skip to the next computation request (which hopefully requires less memory...) So, is there already any such facility provided by the GHC Platform I've missed so far? ...and if not, would such a memory-limiting facility be reconcilable with the GHC RTS architecture? Cheers, hvr --

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[GHC Users] Dictionary sharing
by Jonas Almström Duregård 02 Jul '12

02 Jul '12

Hi, Is there a way to ensure that functions in a class instance are treated as top level definitions and not re-evaluated? For instance if I have this: >>> class C a where list :: [a] instance List a => List [a] where list = permutations list <<< How can I ensure that list :: [[X]] is evaluated at most once for any type X (throughout my program)? I assume this is potentially harmful, since list can never be garbage collected and there may exist an unbounded number of X's. I currently have a solution that uses Typeable to memoise the result of the function based on its type. Is there an easier way? Regards, Jonas

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Compiling ghcjs
by Nathan Hüsken 02 Jul '12

02 Jul '12

Hi, I hope this is the correct list to ask this question. I am trying to compile the ghcjs compiler. I am on ubuntu 12.04 and have ghc-7.4.1 installed (via apt-get). I am following the instruction I found here: https://github.com/ghcjs/ghcjs The first trouble comes with "git pull ghcjs". I get: remote: Counting objects: 42, done. remote: Compressing objects: 100% (9/9), done. remote: Total 26 (delta 22), reused 21 (delta 17) Unpacking objects: 100% (26/26), done. >From github.com:ghcjs/packages-Cabal * [new branch] encoding -> ghcjs/encoding * [new branch] ghc-7.2 -> ghcjs/ghc-7.2 * [new branch] ghc-7.4 -> ghcjs/ghc-7.4 * [new branch] master -> ghcjs/master You asked to pull from the remote 'ghcjs', but did not specify a branch. Because this is not the default configured remote for your current branch, you must specify a branch on the command line. So I am doing: git pull ghcjs ghc-7.4 Then "git branch ghc-7.4 ghcjs/ghc-7.4" gives me: fatal: A branch named 'ghc-7.4' already exists. And finaly "perl boot" fails with: Error: libraries/extensible-exceptions/LICENSE doesn't exist. Maybe you haven't done './sync-all get'? at boot line 74, <PACKAGES> line 57. What can I do? Thanks! Nathan

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Strange behavior when using stable names inside ghci?
by Facundo Domínguez 29 Jun '12

29 Jun '12

Hi, The program below when loaded in ghci prints always False, and when compiled with ghc it prints True. I'm using ghc-7.4.1 and I cannot quite explain such behavior. Any hints? Thanks in advance, Facundo {-# LANGUAGE GADTs #-} import System.Mem.StableName import Unsafe.Coerce import GHC.Conc data D where D :: a -> b -> D main = do putStr "type enter" s <- getLine let i = fromEnum$ head$ s++"0" d = D i i case d of D a b -> do let a' = a sn0 <- pseq a'$ makeStableName a' sn1 <- pseq b$ makeStableName b print (sn0==unsafeCoerce sn1)

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