February 2012 - Glasgow-haskell-users

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

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

7 8

Records in Haskell
by Simon Peyton-Jones 28 Mar '12

28 Mar '12

Friends Provoked the (very constructive) Yesod blog post on "Limitations of Haskell", and the follow up discussion, I've started a wiki page to collect whatever ideas we have about the name spacing issue for record fields. http://hackage.haskell.org/trac/ghc/wiki/Records As Simon M said on Reddit, this is something we'd like to fix; but we need a consensus on how to fix it. Simon

41 183

ANNOUNCE: GHC version 7.2.1
by Ian Lynagh 27 Mar '12

27 Mar '12

============================================================= The (Interactive) Glasgow Haskell Compiler -- version 7.2.1 ============================================================= The GHC Team is pleased to announce a new major release of GHC, 7.2.1. The 7.2 branch is intended to be more of a "technology preview" than normal GHC stable branches; in particular, it supports a significantly improved version of DPH, as well as new features such as compiler plugins and "safe Haskell". The design of these new features may evolve as we get more experience with them. See the release notes for more details of what's new and what's changed. We are also using this branch as an opportunity to work out the best workflows to use with git. We expect the 7.2 branch to be short-lived, with 7.4.1 coming out shortly after ICFP as normal. Full release notes are here: http://www.haskell.org/ghc/docs/7.2.1/html/users_guide/release-7-2-1.html How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: http://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://hackage.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: http://hackage.haskell.org/trac/ghc/wiki/Contributors Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://hackage.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: http://hackage.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://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 http://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug

9 16

Inlining and generic programming
by José Pedro Magalhães 14 Mar '12

14 Mar '12

Hello all, First of all, I'm sorry that this email is so absurdly long. But it's not easy to explain the problem at hand, so I took a step-by-step approach. The executive summary is: GHC can do a *great *job with inlining, but often it doesn't, and I don't understand why. So I have some questions, which are highlighted in the text below. In general, any insights regarding inlining or improving the performance of generics are welcome. My final goal is to be able to state that generic functions (in particular using GHC.Generics) will have no runtime overhead whatsoever when compared to a handwritten type-specific version. The setting Generic programming is based on representing datatypes in a uniform way using a small set of representation types. Functions defined on those representation types can then be applied to all datatypes, because we can convert between datatypes and their representations. However, generic functions tend to be slower than their specialised counterparts, because they have to deal with the conversions. But clever inlining (together with other compiler optimisations) can completely remove this overhead. The problem I'm tackling is how to tell GHC exactly what it should in the particular case of optimisation of generic code. Simplified example I'll focus on the problem of optimising a non-trivial function for generic enumeration of terms. My experience shows that GHC does quite good at optimising simple functions, especially consumers (like generic equality). But producers are trickier. First, we'll need some auxiliary functions: -- | Interleave elements from two lists. Similar to (++), but swap left and > -- right arguments on every recursive application. > -- > -- From Mark Jones' talk at AFP2008 > {-# NOINLINE (|||) #-} > (|||) :: [a] -> [a] -> [a] > [] ||| ys = ys > (x:xs) ||| ys = x : ys ||| xs > > > -- | Diagonalization of nested lists. Ensure that some elements from every > -- sublist will be included. Handles infinite sublists. > -- > -- From Mark Jones' talk at AFP2008 > {-# NOINLINE diag #-} > diag :: [[a]] -> [a] > diag = concat . foldr skew [] . map (map (\x -> [x])) > > skew :: [[a]] -> [[a]] -> [[a]] > skew [] ys = ys > skew (x:xs) ys = x : combine (++) xs ys > > combine :: (a -> a -> a) -> [a] -> [a] -> [a] > combine _ xs [] = xs > combine _ [] ys = ys > combine f (x:xs) (y:ys) = f x y : combine f xs ys > The particular implementation of these functions doesn't really matter. What's important is that we have a way to interleave lists (|||) and a way to diagonalise a matrix into a list (diag). We mark these functions as NOINLINE because inlining them will only make the core code more complicated (and may prevent rules from firing). Suppose we have a type of Peano natural numbers: data Nat = Ze | Su Nat deriving Eq > Implementing enumeration on this type is simple: enumNat :: [Nat] > enumNat = [Ze] ||| map Su enumNat > Now, a generic representation of Nat in terms of sums and products could look something like this: type RepNat = Either () Nat > That is, either a singleton (for the Ze case) or a Nat (for the Su case). Note that I am building a shallow representation, since at the leaves we have Nat, and not RepNat. This mimics the situation with current generic programming libraries (in particular GHC.Generics). We'll need a way to convert between RepNat and Nat: toNat :: RepNat -> Nat > toNat (Left ()) = Ze > toNat (Right n) = Su n > > fromNat :: Nat -> RepNat > fromNat Ze = Left () > fromNat (Su n) = Right n > (In fact, since we're only dealing with a generic producer we won't need the fromNat function.) To get an enumeration for RepNat, we first need to know how to enumerate units and sums: enumU :: [()] > enumU = [()] > > enumEither :: [a] -> [b] -> [Either a b] > enumEither ea eb = map Left ea ||| map Right eb > Now we can define an enumeration for RepNat: enumRepNat :: [RepNat] > enumRepNat = enumEither enumU enumNatFromRep > With the conversion function toNat, we can use enumRepNat to get an enumeration for Nat directly: enumNatFromRep :: [Nat] > enumNatFromRep = map toNat enumRepNat > First, convince yourself that enumNatFromRep and enumNat are equivalent functions: take 100 enumNat == take 100 enumNatFromRep > Now, what I want is that enumNatFromRep generates the same core code as enumNat. That should be possible; here are the necessary steps: map toNat enumRepNat > > == { inline enumRepNat } > > map toNat (enumEither enumU enumNatFromRep) > > == { inline enumEither } > > map toNat (map Left enumU ||| map Right enumNatFromRep) > > == { inline enumU } > > map toNat (map Left [()] ||| map Right enumNatFromRep) > > == { inline map } > > map toNat ([Left ()] ||| map Right enumNatFromRep) > > == { free theorem (|||): forall f a b. map f (a ||| b) = map f a ||| map f > b } > > map toNat [Left ()] ||| map toNat (map Right enumNatFromRep) > > == { inline map } > > [toNat (Left ())] ||| map toNat (map Right enumNatFromRep) > > == { definition of toNat (or inline toNat + case of constant) } > > [Ze] ||| map toNat (map Right enumNatFromRep) > > == { functor composition law: forall f g l. map f (map g l) = map (f . g) > l } > > [Ze] ||| map (toNat . Right) enumNatFromRep > > == { definition of toNat (or inline toNat + case of constant) } > > [Ze] ||| map Su enumNatFromRep > Now let's see what the compiler generates. I'm using GHC-7.4.1. Let's compile with -O1 and use -ddump-simpl to see the final simplifier output (core code) for enumNatFromRep: EnumAlone.enumNatFromRep :: [EnumAlone.Nat] > [GblId, > Str=DmdType, > Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=0, Value=False, > ConLike=False, Cheap=False, Expandable=False, > Guidance=IF_ARGS [] 30 0}] > EnumAlone.enumNatFromRep = > GHC.Base.map > @ EnumAlone.RepNat > @ EnumAlone.Nat > EnumAlone.toNat > EnumAlone.enumRepNat > > EnumAlone.enumRepNat [Occ=LoopBreaker] :: [EnumAlone.RepNat] > [GblId, Str=DmdType] > EnumAlone.enumRepNat = > EnumAlone.||| > @ (Data.Either.Either () EnumAlone.Nat) lvl4_rvV lvl5_rvW > Ah, it didn't even inline enumRepNat because it made it a loop breaker. We certainly want to inline it, so let's add a pragma: {-# INLINE enumRepNat #-} > Recompiling, we get: EnumAlone.enumRepNat [InlPrag=INLINE (sat-args=0)] > :: [EnumAlone.RepNat] > [GblId, > Str=DmdType, > Unf=Unf{Src=InlineStable, TopLvl=True, Arity=0, Value=False, > ConLike=False, Cheap=False, Expandable=False, > Guidance=ALWAYS_IF(unsat_ok=False,boring_ok=False) > Tmpl= EnumAlone.enumEither > @ () @ EnumAlone.Nat EnumAlone.enumU > EnumAlone.enumNatFromRep}] > EnumAlone.enumRepNat = > EnumAlone.||| > @ (Data.Either.Either () EnumAlone.Nat) lvl4_rvV lvl5_rvW > > EnumAlone.enumNatFromRep [Occ=LoopBreaker] :: [EnumAlone.Nat] > [GblId, Str=DmdType] > EnumAlone.enumNatFromRep = > GHC.Base.map > @ EnumAlone.RepNat > @ EnumAlone.Nat > EnumAlone.toNat > EnumAlone.enumRepNat > So no real difference in the generated code, other than the reassignment of loop breakers. For some reason enumRepNat still doesn't get inlined. *Question: why won't GHC inline enumRepNat, even when I tell it to do so with an INLINE pragma?* Well, let's inline it ourselves, then. We redefine enumNatFromRep to: enumNatFromRep = map toNat (enumEither enumU enumNatFromRep) > This however doesn't help much. We get the following core: lvl6_rw5 :: [Data.Either.Either () EnumAlone.Nat] > [GblId] > lvl6_rw5 = > EnumAlone.||| > @ (Data.Either.Either () EnumAlone.Nat) lvl4_rw3 lvl5_rw4 > > EnumAlone.enumNatFromRep [Occ=LoopBreaker] :: [EnumAlone.Nat] > [GblId, Str=DmdType] > EnumAlone.enumNatFromRep = > GHC.Base.map > @ EnumAlone.RepNat @ EnumAlone.Nat EnumAlone.toNat lvl6_rw5 > GHC is really keen on floating that (|||) out. Let's be very explicit about inlining: {-# INLINE toNat #-} > {-# INLINE enumU #-} > {-# INLINE enumEither #-} > Also, maybe it's floating it out because it doesn't have anything else to do to it. Let's add the free theorem of (|||) as a rule: {-# RULES "ft |||" forall f a b. map f (a ||| b) = map f a ||| map f b #-} > We needed this in our manual derivation, so GHC should need it too. Recompiling, we see we've made some progress: lvl5_ryv :: [Data.Either.Either () EnumAlone.Nat] > [GblId] > lvl5_ryv = > GHC.Base.map > @ EnumAlone.Nat > @ (Data.Either.Either () EnumAlone.Nat) > (Data.Either.Right @ () @ EnumAlone.Nat) > EnumAlone.enumNatFromRep > > lvl6_ryw :: [EnumAlone.Nat] > [GblId] > lvl6_ryw = > GHC.Base.map > @ (Data.Either.Either () EnumAlone.Nat) > @ EnumAlone.Nat > EnumAlone.toNat > lvl5_ryv > > EnumAlone.enumNatFromRep [Occ=LoopBreaker] :: [EnumAlone.Nat] > [GblId, Str=DmdType] > EnumAlone.enumNatFromRep = > EnumAlone.||| @ EnumAlone.Nat lvl4_ryu lvl6_ryw > enumNatFromRep finally starts with (|||) directly. But its second argument, lvl6_ryw, is a map of lvl5_ryv, which is itself a map! At this stage I expected GHC to be aware of the fusion law for map, but it seems that it isn't. *Question: why is map fusion not happening automatically?* Let's add it as a rule: {-# RULES "map/map1" forall f g l. map f (map g l) = map (f . g) l #-} > And now we're in a much better situation: lvl3_ryD :: [Data.Either.Either () EnumAlone.Nat] > [GblId, Caf=NoCafRefs] > lvl3_ryD = > GHC.Types.: > @ (Data.Either.Either () EnumAlone.Nat) > EnumAlone.fromNat1 > (GHC.Types.[] @ (Data.Either.Either () EnumAlone.Nat)) > > lvl4_ryE :: [EnumAlone.Nat] > [GblId] > lvl4_ryE = > GHC.Base.map > @ (Data.Either.Either () EnumAlone.Nat) > @ EnumAlone.Nat > EnumAlone.toNat > lvl3_ryD > > lvl5_ryF :: [EnumAlone.Nat] > [GblId] > lvl5_ryF = > GHC.Base.map > @ EnumAlone.Nat > @ EnumAlone.Nat > EnumAlone.Su > EnumAlone.enumNatFromRep > > EnumAlone.enumNatFromRep [Occ=LoopBreaker] :: [EnumAlone.Nat] > [GblId, Str=DmdType] > EnumAlone.enumNatFromRep = > EnumAlone.||| @ EnumAlone.Nat lvl4_ryE lvl5_ryF > Note how toNat is entirely gone from the second part of the enumeration (lvl5_ryF). Strangely enough, the enumerator for Ze (lvl4_ryE) is still very complicated: map toNat ([Left ()]). Why doesn't GHC simplify this to just [Ze]? Apparently because GHC doesn't simplify map over a single element list. *Question: why doesn't GHC optimise map f [x] to [f x]?* Let's tell it to do so: {-# RULES "map/map2" forall f x. map f (x:[]) = (f x):[] #-} > Now we're finally where we wanted: lvl_ryA :: [EnumAlone.Nat] > [GblId, Caf=NoCafRefs] > lvl_ryA = > GHC.Types.: > @ EnumAlone.Nat EnumAlone.Ze (GHC.Types.[] @ EnumAlone.Nat) > > lvl3_ryD :: [EnumAlone.Nat] > [GblId] > lvl3_ryD = > GHC.Base.map > @ EnumAlone.Nat > @ EnumAlone.Nat > EnumAlone.Su > EnumAlone.enumNatFromRep > > EnumAlone.enumNatFromRep [Occ=LoopBreaker] :: [EnumAlone.Nat] > [GblId, Str=DmdType] > EnumAlone.enumNatFromRep = > EnumAlone.||| @ EnumAlone.Nat lvl_ryA lvl3_ryD > This is what I wanted: no more representation types (Either or ()), and the code looks exactly like what is generated for the handwritten enumNat. More realistic generic programming Now let's see if we can transport this to the setting of a generic programming library. I'll use a bare-bones version of GHC.Generics: infixr 5 :+: > infixr 6 :*: > > data U = U deriving (Show, Read) > data a :+: b = L a | R b deriving (Show, Read) > data a :*: b = a :*: b deriving (Show, Read) > newtype Var a = Var a deriving (Show, Read) > newtype Rec a = Rec a deriving (Show, Read) > > class Representable a where > type Rep a > to :: Rep a -> a > from :: a -> Rep a > Let's represent Nat in this library: instance Representable Nat where > type Rep Nat = U :+: (Rec Nat) > from Ze = L U > from (Su n) = R (Rec n) > to (L U) = Ze > to (R (Rec n)) = Su n > (Note, in particular, that we do not need INLINE pragmas on the from/to methods. This might just be because GHC thinks these are small and inlines them anyway, but in general we want to make sure they are inlined, so we typically use pragmas there.) Now we need to implement enumeration generically. We do this by giving an instance for each representation type: class GEnum' a where > genum' :: [a] > > instance GEnum' U where > {-# INLINE genum' #-} > genum' = [U] > > instance (GEnum a) => GEnum' (Rec a) where > {-# INLINE genum' #-} > genum' = map Rec genum > > instance (GEnum a) => GEnum' (Var a) where > {-# INLINE genum' #-} > genum' = map Var genum > > instance (GEnum' f, GEnum' g) => GEnum' (f :+: g) where > {-# INLINE genum' #-} > genum' = map L genum' ||| map R genum' > > instance (GEnum' f, GEnum' g) => GEnum' (f :*: g) where > {-# INLINE genum' #-} > --genum' = diag [ [ x :*: y | y <- genum' ] | x <- genum' ] > genum' = diag (map (\x -> map (\y -> x :*: y) genum') genum') > We explicitly tell GHC to inline each case, as before. Note that for products I'm not using the more natural list comprehension syntax because I don't quite understand how that gets translated into core. In the cases for Var and Rec we use genum from the GEnum class: class GEnum a where > genum :: [a] > {-# INLINE genum #-} > default genum :: (Representable a, GEnum' (Rep a)) => [a] > genum = map to genum' > GEnum' is the class used for instantiating the generic representation types, and GEnum is used for user types. We use a default signature to provide a default method that can be used when we have a Representable instance for the type in question. This makes instantiating Nat very easy: instance GEnum Nat > Unfortunately, the core code generated in this situation (with the same RULES as before) is not nice at all: Main.$fGEnumNat_$cgenum [Occ=LoopBreaker] :: [Base.Nat] > [GblId, Str=DmdType] > Main.$fGEnumNat_$cgenum = > GHC.Base.map > @ (Base.Rep Base.Nat) > @ Base.Nat > Base.$fRepresentableNat_$cto > (lvl37_r79y > `cast` (Sym (GEnum.NTCo:GEnum') <Base.U Base.:+: (Base.Rec Base.Nat)> > ; > (GEnum.GEnum' (Sym > (Base.TFCo:R:RepNat)) ; > GEnum.NTCo:GEnum' <Base.Rep > Base.Nat>) > :: [Base.C Base.Nat_Ze_ Base.U > Base.:+: Base.C Base.Nat_Su_ (Base.Rec Base.Nat)] > ~# > [Base.Rep Base.Nat])) > We see a map of the `to` function, which is definitely not what we want. Oddly enough, if we give an explicit definition of genum for Nat, with the inlined default... instance GEnum Nat where genum = map to genum' > ... then we get the optimised code we want: lvl34_r79p :: [Base.Nat] > [GblId, Caf=NoCafRefs] > lvl34_r79p = > GHC.Types.: @ Base.Nat Base.Ze (GHC.Types.[] @ Base.Nat) > > lvl35_r79q :: [Base.Nat] > [GblId] > lvl35_r79q = > GHC.Base.map @ Base.Nat @ Base.Nat Base.Su Main.$fGEnumNat_$cgenum > > Main.$fGEnumNat_$cgenum [Occ=LoopBreaker] :: [Base.Nat] > [GblId, Str=DmdType] > Main.$fGEnumNat_$cgenum = > GEnum.||| @ Base.Nat lvl34_r79p lvl35_r79q > Again, no representation types, no `to`, just the same code that is generated for enumNat. Perfect. But we had to avoid using the default definition, which is a pity. *Question: why won't GHC inline the default method of a class, even when I have a pragma telling it to do so?* Let's look at one more datatype, because Nat does not use products. So let's consider trees: data Tree a = Leaf | Bin a (Tree a) (Tree a) > > instance Representable (Tree a) where > type Rep (Tree a) = U :+: (Var a :*: Rec (Tree a) :*: Rec (Tree a)) > from (Bin x l r) = R (Var x :*: Rec l :*: Rec r) > from Leaf = L U > to (R (Var x :*: (Rec l) :*: (Rec r))) = Bin x l r > to (L U) = Leaf > We give a GEnum instance using the same trick as before: instance GEnum (Tree Int) where genum = map to genum' > (For simplicity only for trees of integers.) The generated code for trees is unfortunately not as nice: a2_r79M > :: [Base.Rec (Base.Tree GHC.Types.Int) > Base.:*: Base.Rec (Base.Tree GHC.Types.Int) > [GblId, Str=DmdType] > a2_r79M = > GEnum.diag > @ (Base.Rec (Base.Tree GHC.Types.Int) > Base.:*: Base.Rec (Base.Tree GHC.Types.Int)) > lvl8_r79L > > lvl9_r79N :: [Base.Tree GHC.Types.Int] > [GblId] > lvl9_r79N = > GHC.Base.map > @ (Base.Rec (Base.Tree GHC.Types.Int) > Base.:*: Base.Rec (Base.Tree GHC.Types.Int)) > @ (Base.Tree GHC.Types.Int) > lvl5_r79H > a2_r79M > > Main.$fGEnumTree_$cgenum [Occ=LoopBreaker] > :: [Base.Tree GHC.Types.Int] > [GblId, Str=DmdType] > Main.$fGEnumTree_$cgenum = > GEnum.||| @ (Base.Tree GHC.Types.Int) lvl4_r79G lvl9_r79N > Note how lvl9_r79N is a map over a2_r79M, and a2_r79M is a `diag`. Ok, we need the free theorem of `diag` to tell GHC how to commute the `diag` with map: {-# RULES "ft/diag" forall f l. map f (diag l) = diag (map (map f) l) #-} > Unfortunately this doesn't change the generated core code. With some more debugging looking at the generated code at each simplifier iteration, I believe that this is because a2_r79M got lifted out too soon, prevent the rule from applying. With some imagination I decided to try the -fno-full-laziness flag to prevent let-floating. I'm not sure this is a good idea in general, but in this particular case it gives much better results: a1_r72i :: [Base.Rec (Base.Tree GHC.Types.Int) > [GblId, Str=DmdType] > a1_r72i = > GHC.Base.map > @ (Base.Tree GHC.Types.Int) > @ (Base.Rec (Base.Tree GHC.Types.Int)) > ((\ (tpl_B1 :: Base.Tree GHC.Types.Int) -> tpl_B1) > `cast` (<Base.Tree GHC.Types.Int> > -> Sym (Base.NTCo:Rec <Base.Tree GHC.Types.Int>) > :: (Base.Tree GHC.Types.Int -> Base.Tree GHC.Types.Int) > ~# > (Base.Tree GHC.Types.Int -> Base.Rec (Base.Tree > GHC.Types.Int)))) > Main.$fGEnumTree_$cgenum > > Main.$fGEnumTree_$cgenum [Occ=LoopBreaker] > :: [Base.Tree GHC.Types.Int] > [GblId, Str=DmdType] > Main.$fGEnumTree_$cgenum = > GEnum.||| > @ (Base.Tree GHC.Types.Int) > (GHC.Types.: > @ (Base.Tree GHC.Types.Int) > (Base.Leaf @ GHC.Types.Int) > (GHC.Types.[] @ (Base.Tree GHC.Types.Int))) > (GEnum.diag > @ (Base.Tree GHC.Types.Int) > (GHC.Base.map > @ (Base.Rec (Base.Tree GHC.Types.Int)) > @ [Base.Tree GHC.Types.Int] > (\ (x_a1yQ :: Base.Rec (Base.Tree GHC.Types.Int)) -> > GHC.Base.map > @ (Base.Rec (Base.Tree GHC.Types.Int)) > @ (Base.Tree GHC.Types.Int) > (\ (x1_X1zB :: Base.Rec (Base.Tree GHC.Types.Int)) -> > Base.Bin > @ GHC.Types.Int > a_r72h > (x_a1yQ > `cast` (Base.NTCo:Rec <Base.Tree GHC.Types.Int> > :: Base.Rec (Base.Tree GHC.Types.Int) ~# > Base.Tree GHC.Types.Int)) > (x1_X1zB > `cast` (Base.NTCo:Rec <Base.Tree GHC.Types.Int> > :: Base.Rec (Base.Tree GHC.Types.Int) ~# > Base.Tree GHC.Types.Int))) > a1_r72i) > a1_r72i)) > Note how our enum is now of the shape `[Leaf] ||| diag y`, which is good. The only catch is that there are some `Rec`s still laying around, with their associated newtype coercions, and a function a1_r72i that basically wraps the recursive enumeration in a Rec, only to be unwrapped in the body of `$fGEnumTree_$cgenum`. I don't know how to get GHC to simplify this code any further. *Question: why do I need -fno-full-laziness for the ft/diag rule to apply?* *Question: why is GHC not getting rid of the Rec newtype in this case?* I have also played with -O2, in particular because of the SpecConstr optimisation, but found that it does not affect these particular examples (perhaps it only becomes important with larger datatypes). I have also experimented with phase control in the rewrite rules and the inline pragmas, but didn't find it necessary for this example. In general, anyway, my experience with the inliner is that it is extremely fragile, especially across different GHC versions, and it's hard to get any guarantees of optimisation. I have also played with the -funfolding-* options before, with mixed results. [1] It's also a pity that certain flags are not explained in detail in the user's manual [2,3], like -fliberate-case, and -fspec-constr-count and threshold, for instance. Thank you for reading this. Any insights are welcome. In particular, I'm wondering if I might be missing some details regarding strictness. Cheers, Pedro [1] http://dreixel.net/research/pdf/ogie.pdf [2] http://www.haskell.org/ghc/docs/latest/html/users_guide/flag-reference.html [3] http://www.haskell.org/ghc/docs/latest/html/users_guide/options-optimise.ht…

2 3

ghci 7.4.1 no longer loading .o files?
by Evan Laforge 06 Mar '12

06 Mar '12

Is there something that changed in 7.4.1 that would cause it to decide to interpret .hs files instead of loading their .o files? E.g.: % ghc -c T.hs % ghci GHCi, version 7.4.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package filepath-1.3.0.0 ... linking ... done. Prelude> :l T [1 of 1] Compiling T ( T.hs, interpreted ) Ok, modules loaded: T. *T> Versus how this works with 7.0.3: % ghc-7.0.3 -c T.hs % ghci-7.0.3 GHCi, version 7.0.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Loading package filepath-1.2.0.0 ... linking ... done. Prelude> :l T Ok, modules loaded: T. Prelude T> It makes a big difference when ghci decides to go interpret 100 files vs just sucking in the .o files. This is OS X, 10.6.8. Anyone else see this?

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Error while installing new packages with GHC 7.4.1
by Antoras 06 Mar '12

06 Mar '12

I updated my GHC version from 7.0.3 to 7.4.1. But after that GHC is unable to install some required packages. For example when I type in 'cabal install -v hoogle' I get a lot of errors (see end of message). Even after reinstalling the newest packages the errors still occurs. I use Linux-x86_64 and get this information: $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.4.1 $ ghc-pkg list | grep Cabal Cabal-1.14.0 How to solve the error? Reading available packages... Resolving dependencies... In order, the following would be installed: deepseq-1.3.0.0 (reinstall) changes: array-0.4.0.0 -> 0.3.0.3 containers-0.4.2.1 (reinstall) changes: array-0.4.0.0 -> 0.3.0.3 Cabal-1.12.0 (new version) binary-0.5.1.0 (reinstall) changes: array-0.4.0.0 -> 0.3.0.3 haskell-src-exts-1.11.1 (new package) syb-0.3.6 (new package) template-haskell-2.7.0.0 (reinstall) cmdargs-0.9.3 (new package) text-0.11.1.13 (reinstall) changes: array-0.4.0.0 -> 0.3.0.3 blaze-builder-0.3.1.0 (new package) enumerator-0.4.18 (new package) blaze-builder-enumerator-0.2.0.3 (new package) hashable-1.1.2.3 (new package) case-insensitive-0.4.0.1 (new package) http-types-0.6.9 (new package) parsec-3.1.2 (new package) network-2.3.0.11 (new package) simple-sendfile-0.2.1 (new package) tagsoup-0.12.6 (new package) time-1.4 (reinstall) random-1.0.1.1 (new package) unordered-containers-0.1.4.6 (new package) uniplate-1.6.6 (new package) wai-0.4.3 (new package) warp-0.4.6.3 (new package) hoogle-4.2.8 (new package) Extracting /home/antoras/.cabal/packages/hackage.haskell.org/deepseq/1.3.0.0/deepseq-1.3.0.0.tar.gz to /tmp/deepseq-1.3.0.016966... Configuring deepseq-1.3.0.0... Dependency array ==0.3.0.3: using array-0.3.0.3 Dependency base ==4.5.0.0: using base-4.5.0.0 Using Cabal-1.10.1.0 compiled by ghc-7.0 Using compiler: ghc-7.4.1 Using install prefix: /home/antoras/.cabal Binaries installed in: /home/antoras/.cabal/bin Libraries installed in: /home/antoras/.cabal/lib/deepseq-1.3.0.0/ghc-7.4.1 Private binaries installed in: /home/antoras/.cabal/libexec Data files installed in: /home/antoras/.cabal/share/deepseq-1.3.0.0 Documentation installed in: /home/antoras/.cabal/share/doc/deepseq-1.3.0.0 Using alex version 2.3.5 found on system at: /usr/bin/alex Using ar found on system at: /usr/bin/ar No c2hs found Using cpphs version 1.12 found on system at: /home/antoras/.cabal/bin/cpphs No ffihugs found Using gcc version 4.6.2 found on system at: /usr/bin/gcc Using ghc version 7.4.1 found on system at: /usr/bin/ghc Using ghc-pkg version 7.4.1 found on system at: /usr/bin/ghc-pkg No greencard found Using haddock version 2.10.0 found on system at: /usr/bin/haddock Using happy version 1.18.6 found on system at: /usr/bin/happy No hmake found Using hsc2hs version 0.67 found on system at: /usr/bin/hsc2hs No hscolour found No hugs found No jhc found Using ld found on system at: /usr/bin/ld No lhc found No lhc-pkg found No nhc98 found Using pkg-config version 0.26 found on system at: /usr/bin/pkg-config Using ranlib found on system at: /usr/bin/ranlib Using strip found on system at: /usr/bin/strip Using tar found on system at: /bin/tar No uhc found Creating dist/build (and its parents) Creating dist/build/autogen (and its parents) Preprocessing library deepseq-1.3.0.0... Building deepseq-1.3.0.0... Building library... Creating dist/build (and its parents) /usr/bin/ghc --make -package-name deepseq-1.3.0.0 -hide-all-packages -fbuilding-cabal-package -i -idist/build -i. -idist/build/autogen -Idist/build/autogen -Idist/build -optP-include -optPdist/build/autogen/cabal_macros.h -odir dist/build -hidir dist/build -stubdir dist/build -package-id array-0.3.0.3-29b5df20d1fe0ed3d8d697b667bb789e -package-id base-4.5.0.0-6db966b4cf8c1a91188e66d354ba065e -O -Wall -XHaskell98 -XCPP Control.DeepSeq [1 of 1] Compiling Control.DeepSeq ( Control/DeepSeq.hs, dist/build/Control/DeepSeq.o ) Control/DeepSeq.hs:56:1: array-0.3.0.3:Data.Array can't be safely imported! The module itself isn't safe. Extracting /home/antoras/.cabal/packages/hackage.haskell.org/haskell-src-exts/1.11.1/haskell-src-exts-1.11.1.tar.gz to /tmp/haskell-src-exts-1.11.116966... Creating /tmp/haskell-src-exts-1.11.116966/haskell-src-exts-1.11.1/dist/setup (and its parents) /usr/bin/ghc --make /tmp/haskell-src-exts-1.11.116966/haskell-src-exts-1.11.1/Setup.hs -o /tmp/haskell-src-exts-1.11.116966/haskell-src-exts-1.11.1/dist/setup/setup -odir /tmp/haskell-src-exts-1.11.116966/haskell-src-exts-1.11.1/dist/setup -hidir /tmp/haskell-src-exts-1.11.116966/haskell-src-exts-1.11.1/dist/setup -i -i/tmp/haskell-src-exts-1.11.116966/haskell-src-exts-1.11.1 -package Cabal-1.14.0 <command line>: cannot satisfy -package Cabal-1.14.0: Cabal-1.14.0-5875475606fe70ef919bbc055077d744 is unusable due to missing or recursive dependencies: array-0.4.0.0-59d1cc0e7979167b002f021942d60f46 containers-0.4.2.1-cfc6420ecc2194c9ed977b06bdfd9e69 directory-1.1.0.2-07820857642f1427d8b3bb49f93f97b0 process-1.1.0.1-18dadd8ad5fc640f55a7afdc7aace500 (use -v for more information) Extracting /home/antoras/.cabal/packages/hackage.haskell.org/syb/0.3.6/syb-0.3.6.tar.gz to /tmp/syb-0.3.616966... Creating /tmp/syb-0.3.616966/syb-0.3.6/dist/setup (and its parents) /usr/bin/ghc --make /tmp/syb-0.3.616966/syb-0.3.6/Setup.hs -o /tmp/syb-0.3.616966/syb-0.3.6/dist/setup/setup -odir /tmp/syb-0.3.616966/syb-0.3.6/dist/setup -hidir /tmp/syb-0.3.616966/syb-0.3.6/dist/setup -i -i/tmp/syb-0.3.616966/syb-0.3.6 -package Cabal-1.14.0 <command line>: cannot satisfy -package Cabal-1.14.0: Cabal-1.14.0-5875475606fe70ef919bbc055077d744 is unusable due to missing or recursive dependencies: array-0.4.0.0-59d1cc0e7979167b002f021942d60f46 containers-0.4.2.1-cfc6420ecc2194c9ed977b06bdfd9e69 directory-1.1.0.2-07820857642f1427d8b3bb49f93f97b0 process-1.1.0.1-18dadd8ad5fc640f55a7afdc7aace500 (use -v for more information) World file is already up to date. cabal: Error: some packages failed to install: Cabal-1.12.0 depends on deepseq-1.3.0.0 which failed to install. binary-0.5.1.0 depends on deepseq-1.3.0.0 which failed to install. blaze-builder-0.3.1.0 depends on deepseq-1.3.0.0 which failed to install. blaze-builder-enumerator-0.2.0.3 depends on deepseq-1.3.0.0 which failed to install. case-insensitive-0.4.0.1 depends on deepseq-1.3.0.0 which failed to install. cmdargs-0.9.3 depends on deepseq-1.3.0.0 which failed to install. containers-0.4.2.1 depends on deepseq-1.3.0.0 which failed to install. deepseq-1.3.0.0 failed during the building phase. The exception was: ExitFailure 1 enumerator-0.4.18 depends on deepseq-1.3.0.0 which failed to install. hashable-1.1.2.3 depends on deepseq-1.3.0.0 which failed to install. haskell-src-exts-1.11.1 failed during the configure step. The exception was: ExitFailure 1 hoogle-4.2.8 depends on syb-0.3.6 which failed to install. http-types-0.6.9 depends on deepseq-1.3.0.0 which failed to install. network-2.3.0.11 depends on deepseq-1.3.0.0 which failed to install. parsec-3.1.2 depends on deepseq-1.3.0.0 which failed to install. random-1.0.1.1 depends on deepseq-1.3.0.0 which failed to install. simple-sendfile-0.2.1 depends on deepseq-1.3.0.0 which failed to install. syb-0.3.6 failed during the configure step. The exception was: ExitFailure 1 tagsoup-0.12.6 depends on deepseq-1.3.0.0 which failed to install. template-haskell-2.7.0.0 depends on deepseq-1.3.0.0 which failed to install. text-0.11.1.13 depends on deepseq-1.3.0.0 which failed to install. time-1.4 depends on deepseq-1.3.0.0 which failed to install. uniplate-1.6.6 depends on syb-0.3.6 which failed to install. unordered-containers-0.1.4.6 depends on deepseq-1.3.0.0 which failed to install. wai-0.4.3 depends on deepseq-1.3.0.0 which failed to install. warp-0.4.6.3 depends on deepseq-1.3.0.0 which failed to install.

5 8

partially applied type synonyms
by Arie Peterson 05 Mar '12

05 Mar '12

Dear list, Is there a good reason that partially applied type synonyms cannot be made instances of classes? - A simple example would be making the identity type 'Id' ("type Id x = x") instance of 'Monad'. This would eliminate the need for some silly occurrences of 'runIdentity', and perhaps narrow the gap between monads and monad transformers. - The reason I complain about this now is a more involved example, where introducing a newtype to work around the restriction is not an option. Well, not as far as I can see now, anyway. Partially applied type synonyms are, in a sense, the anonymous functions at the type level, and one might argue that they deserve the same 'first-class member status' as the lambda at the value level. Kind regards, Arie Peterson

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