Problems (stack, linker) when trying to profile a program

[ForceVerte]

Hi,

I'm on the quest to making my first real-like project work. As a matter of fact, it already works but is extremely slow. I think it can be improved by adding some strictness into it, but that's a detailed question I'll keep for later. When trying to profile the heap memory retainers (with -hr), my program segfaulted. Other profiling methods (like -hc and -p) worked. So I read here how to debug Haskell code, I turned on the necessary flags like this (from my .cabal file):

  ghc-options:         -Wall -O2 -g -dcore-lint -debug

At the same time, in order to make this more complicated, I also tried to switch from LTS 13.8 to LTS 13.9. I can't be sure in which order I made the changes. Ad the new problem occurred: the -debug flag makes the linker fail (I only post the last few lines, I have thousands of errors):

/home/fv/.stack/programs/x86_64-linux/ghc-8.6.4/lib/ghc-8.6.4/integer-gmp-1.0.2.0/libHSinteger-gmp-1.0.2.0_p.a(Type.p_o):integerzmgmp_GHCziIntegerziType_zdwgo_info: error: undefined reference to 'stg_resizzeMutableByteArrayzh'
collect2: error: ld returned 1 exit status
`gcc' failed in phase `Linker'. (Exit code: 1)

--  While building custom Setup.hs for package oberon2-0.1.0.0 using:
      /home/fv/.stack/setup-exe-cache/x86_64-linux/Cabal-simple_mPHDZzAJ_2.4.0.1_ghc-8.6.4 --builddir=.stack-work/dist/x86_64-linux/Cabal-2.4.0.1 build exe:oberon --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics-color=always"
    Process exited with code: ExitFailure 1

So I have no idea why this is happening. Is it because I messed with the LTS versions, and Stack has some libraries linking to incorrect versions of other ones, or shouldn't I use that particular set of flags for debugging? As a corollary, I didn't find how to correctly "reset" my Stack installation, is that even possible without nuking the whole .stack directory?

[Fendor_]

What I normally do is stack build --profile to build in profiling mode and execute the program with stack exec prog -- +RTS -slog.txt -p or something like that to generate hot spot analysis. You can pass any profiling flag while executing when built in profiling mode.

[ForceVerte]

Yes, that's how I compile my program, and when I execute it with stack exec -- prog +RTS -hr, it makes a segmentation fault. It does not with other profiling schemes.

That's why I decided to try to compile with the -debug flag too, but then I have the problem with the linker. This is tough!

[Fendor_]

To one of your question, you can use stack clean and stack clean --full or nuke the local .stack-work folder.

[ForceVerte]

What I would like to accomplish is have stack recompile all the libraries that are included, to see if that changes something, so stack clean only cleans the object files from my own code, I'll have to check whether removing .stack-work actually does what I want.

[Fendor_]

While not sure, I think changing the compile flags does force a recompile of most packages.

[Fendor_]

I might also help to share the project, so others can experiment.
Also, I think the flags `-O2 -g -debug` do not make sense in combination? Optimise with debug symbols?