[Haskell-cafe] Was directed here for help with why ghc is failing to find mtl.

Haskell Beginner haskell.beginner at gmail.com
Sat May 17 14:49:24 UTC 2014


This is the error message which started it all off:
http://lpaste.net/104242

Then the following conversation happened:
==============================================================================
--- JPMoresmau ------

First package to fail is exceptions. Just open a console and type in

    cabal install exceptions

EclipseFP tries to put some parallel install flags that may make the errors
less visible (a Cabal thing, not an EclipseFP thing). I really don't like
the look of getting warnings in c code, though...

--- haskell_beginner ------

    $ cabal install exceptions
    Resolving dependencies...
    Configuring exceptions-0.6.1...

    /var/folders/3r/gvk584k50jb253024p4wxy3r0000gn/T/5187.c:1:12:
         warning: control reaches end of non-void function [-Wreturn-type]
    int foo() {}
               ^
    1 warning generated.
    Building exceptions-0.6.1...
    Preprocessing library exceptions-0.6.1...
    <command line>: cannot satisfy -package-id
mtl-2.1.2-94c72af955e94b8d7b2f359dadd0cb62
        (use -v for more information)
    Failed to install exceptions-0.6.1
    cabal: Error: some packages failed to install:
    exceptions-0.6.1 failed during the building phase. The exception was:
    ExitFailure 1
    $

What flags can I add to that to get a better error message?

EDIT TO ADD:
Again if there is another layer automatically adding flags to the above
command, I know nothing about it. This includes if Haskell or cabal uses a
config file. I am on a — to my knowledge — completely stock install of
Haskell for Mac OS.

--- JPMoresmau ------

    cabal install -v exceptions

May give more info about why the mtl package cannot be satisfied when it
seems to have been installed.

--- haskell_beginner ------

    $ cabal install -v exceptions
    Reading available packages...
    Choosing modular solver.
    Resolving dependencies...
    Ready to install exceptions-0.6.1
    Waiting for install task to finish...
    Extracting
    /Users/person/Library/Haskell/repo-cache/
hackage.haskell.org/exceptions/0.6.1/exceptions-0.6.1.tar.gz
    to
/var/folders/3r/gvk584k50jb253024p4wxy3r0000gn/T/exceptions-0.6.1-5256...
    Updating exceptions.cabal with the latest revision from the index.
    Configuring exceptions-0.6.1...
    Dependency base ==4.6.0.1: using base-4.6.0.1
    Dependency mtl ==2.1.2: using mtl-2.1.2
    Dependency transformers ==0.3.0.0: using transformers-0.3.0.0

    /var/folders/3r/gvk584k50jb253024p4wxy3r0000gn/T/5256.c:1:12:
         warning: control reaches end of non-void function [-Wreturn-type]
    int foo() {}
               ^
    1 warning generated.
    Using Cabal-1.16.0 compiled by ghc-7.6
    Using compiler: ghc-7.6.3
    Using install prefix:
    /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1
    Binaries installed in:
    /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/bin
    Libraries installed in:
    /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/lib
    Private binaries installed in:
    /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/libexec
    Data files installed in:
    /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/share
    Documentation installed in:
    /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/doc
    Using alex version 3.0.5 found on system at: /usr/bin/alex
    Using ar found on system at: /usr/bin/ar
    No c2hs found
    Using cpphs version 1.18.1 found on system at:
    /Users/person/Library/Haskell/bin/cpphs
    No ffihugs found
    Using gcc version 4.2.1 found on system at: /usr/bin/gcc
    Using ghc version 7.6.3 found on system at: /usr/bin/ghc
    Using ghc-pkg version 7.6.3 found on system at: /usr/bin/ghc-pkg
    No greencard found
    Using haddock version 2.13.2 found on system at: /usr/bin/haddock
    Using happy version 1.18.10 found on system at: /usr/bin/happy
    No hmake found
    Using hpc version 0.6 found on system at: /usr/bin/hpc
    Using hsc2hs version 0.67 found on system at: /usr/bin/hsc2hs
    Using hscolour version 1.20 found on system at:
    /Users/person/Library/Haskell/bin/HsColour
    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
    No pkg-config found
    Using ranlib found on system at: /usr/bin/ranlib
    Using strip found on system at: /usr/bin/strip
    Using tar found on system at: /usr/bin/tar
    No uhc found
    creating dist/build
    creating dist/build/autogen
    Building exceptions-0.6.1...
    Preprocessing library exceptions-0.6.1...
    Building library...
    creating dist/build
    /usr/bin/ghc --make -fbuilding-cabal-package -O -odir dist/build -hidir
dist/build -stubdir dist/build -i -idist/build -isrc -idist/build/autogen
-Idist/build/autogen -Idist/build -optP-include
-optPdist/build/autogen/cabal_macros.h -package-name exceptions-0.6.1
-hide-all-packages -package-db dist/package.conf.inplace -package-id
base-4.6.0.1-6c351d70a24d3e96f315cba68f3acf57 -package-id
mtl-2.1.2-94c72af955e94b8d7b2f359dadd0cb62 -package-id
transformers-0.3.0.0-ff2bb6ac67241ebb987351a3db564af0 -XHaskell98
Control.Monad.Catch Control.Monad.Catch.Pure -Wall -fwarn-tabs -O2
    <command line>: cannot satisfy -package-id
mtl-2.1.2-94c72af955e94b8d7b2f359dadd0cb62
        (use -v for more information)
    Failed to install exceptions-0.6.1
    World file is already up to date.
    cabal: Error: some packages failed to install:
    exceptions-0.6.1 failed during the building phase. The exception was:
    ExitFailure 1
    $

Hope that helps. I don't know what to make of it. :-/

--- JPMoresmau ------

Neither do I! It seems cabal finds a mtl package to use, but when it passes
the exact reference of the package (with a trailing hash to indicate the
specifics of your install), ghc doesn't find it. At least it's nothing to
do with EclipseFP, which is a relief (for me :-p). I suggest you post that
to the Haskell-Cafe mailing list if nobody has any clue here. I know that
MacOS is a bit weird sometimes with PATH and such.
==============================================================================

Thus with the history of this error now told (TL;DR: read JPMoresmau's last
comment above), the question I pose to this mailing list is:

Why is ghc failing to find mtl?

Thanks,
~Haskell Beginner
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