Installing Haskell profile libraries

This blog post was originally written back in 2010-11-23

Profiling with GHC is done by compiling with the -prof parameter, which compiles the program with profile code that can be activated by executing the program with ./myprogram +RTS -p -RTS. This creates log file called myprogram.prof.

>>> ghc -prof --make -O2 myfile.hs
>>> ./myfile +RTS -p -RTS
>>> cat myfile.prof

Unfortunately this doesn’t work out-of-the-box. You have to install the profiling versions of all libraries and all depending libraries. And even more unfortunately, cabal doesn’t resolve dependencies for profiling libraries.

>>> cabal install --reinstall -p libraryname

Update: To automatically install the profiling libraries for future installations edit the ~/.cabal/config and set the profiling options to True. (thanks Erik)

Update2: You may only do this for libraries. I got leksah-server complaining about -N2 option not being available with profiling executable.

But the reinstallation produces errors like:

Directory.hs:2:4:
    The export item `Permissions(Permissions, readable, writable,
                                 executable, searchable)'
    attempts to export constructors or class methods that are not visible here
cabal: Error: some packages failed to install:
MissingH-1.1.0.3 depends on haskell98-1.0.1.1 which failed to install.
haskell98-1.0.1.1 failed during the building phase. The exception was:
ExitFailure 1

or

>>     Could not find module `Data.List.Utils':
>>       Perhaps you haven't installed the profiling libraries for package
>> missingh-1.1.0.3?
>>       Use -v to see a list of the files searched for.

I also tried removing and recompiling some packages completely like so

>>> ghc-pkg unregister MissingH    # case-sensitive
>>> cabal unpack MissingH
>>> cd MissingH-1.1.0.3/
>>> cabal configure -prof
>>> cabal build
>>> cabal install

There are some fundamental libraries which cannot be installed via cabal (like parsec3), so you rather have to:

>>> sudo apt-get install libghc6-*-prof

But eventually I found out that my packages are broken anyway (check with ghc-pkg check) and I had to reinstall Haskell platform, which also didn’t work because:

>>> sudo apt-get purge ghc6    # didn't work

Just do:

>>> mv ~/.ghc6 ~/.ghc6.bak
>>> sudo apt-get purge ghc6
>>> sudo apt-get install --reinstall haskell-platform

Some links which were quite helpful: