Profiling with Stack

Question

I'm trying to get profiling working in Stack, so that I can get the same metrics as the one indicated on Chapter 25 of RWH. I started a new Stack project, as follows:

stack new test

Then, as indicated here I ran:

stack install --executable-profiling --library-profiling --ghc-options="-rtsopts"

However this command fails with the following error:

    While constructing the BuildPlan the following exceptions were encountered:

--  While attempting to add dependency,
    Could not find package base in known packages

--  Failure when adding dependencies:    
      base: needed (>=4.7 && <5), stack configuration has no specified version (latest applicable is 4.9.0.0)
    needed for package test-0.1.0.0

Recommended action: try adding the following to your extra-deps in /home/damian/test/stack.yaml
- base-4.9.0.0

You may also want to try the 'stack solver' command

I've tried the recommendations above, without success.

If I run stack build then the program is built without errors.

As an additional question, I wonder whether is not possible to run stack test or stack exec with the flags above (this seems more logical than installing a the executable in order to profile it).

Answer 1

It works for me on lts-6.4. To me, this indicates that you don't have a profiling version of base installed. This would need to get installed when installing GHC. What does stack exec -- which ghc say? If ghc isn't located in your stack root, ~/.stack/programs, then this means that you're using a custom GHC install, which may lack a profiling version of base. To resolve, either:

1) Remove custom install and run "stack setup" 2) Alternatively, set system-ghc: false and run "stack setup"

Answer 2

stack install is equivalent to stack build --copy-bins, so you should be able to run

stack build --executable-profiling --library-profiling --ghc-options="-rtsopts"

which will result in a compiled executable somewhere underneath your .stack-work/ directory (stack will tell you where). You should then be able to run it and get the .prof file you are expecting.