GHC linker cannot find lHSsemigroups

Question

I'm attempting to compile a Haskell project on Windows with profiling enabled, using the following command.

ghc --make -O -prof -fprof-auto game_dangerous.hs

I develop the project myself and the same source code compiled and linked fine without profiling. As expected (from previous experience) I ran into a number of errors of the form:

Could not find module `Data.Vector.Mutable'
Perhaps you haven't installed the profiling libraries for package `vector-0.12.0.2'?

I proceeded to iteratively reinstall packages based on the errors encountered using for example:

cabal install -p vector --reinstall

Cabal kept giving me warnings about possibly breaking packages with the reinstalls but I pressed on as (as far as I could see) every package that could be broken was going to get reinstalled itself as I moved through the tree of dependencies. Also, I've previously followed the same process on another machine and it worked fine. After reinstalling all the required packages my project now compiles but the linker fails with this error:

C://Program Files//Haskell Platform//8.6.3//mingw//bin/ld.exe: cannot find -lHSsemigroups-0.18.5-8pPnWqWrcWhEagTFf5Pnk2_p
collect2.exe: error: ld returned 1 exit status
`gcc.exe' failed in phase `Linker'. (Exit code: 1)

However, the build does complete successfully without profiling enabled. Does anyone know what may have gone wrong and how to fix the issue? Thanks in advance.

Steven

Nick Pershyn Nick Pershyn · Accepted Answer · 2020-02-17T20:58:40

I would try making a .cabal file for your program, where you explicitly specify the cabal packages your program depends on and use cabal v2-build to compile your program. It will warn you about missing dependencies of your program until you include them all in build-depends section of the .cabal file. You only need to include the dependencies of your program, not the dependencies of the dependencies. After that you can add cabal.project.local to enable profiling and maybe something else. It should be enough to run cabal v2-build to build your program and packages it depends on with profiling(and other options in the cabal.project.local) enabled.

You need to have profiling enabled in the packages used by your program to support profiling in it. Cabal v2 builds allows you to have multiple instances of the same package. Those instances are different because different flags and options have been used to build them.

It is possible to achieve the same result using a separate package database for your program. That is using ghc-pkg with --package-db option.

Another option is to use stack. It will solve the same issues, but differently at the cost of more space and some performance penalties in ghc(compared to ghc built from source which can be used with cabal).

GHC linker cannot find lHSsemigroups

1 Answers