ghc-whole-program-compiler-project VS hint

Another thing you can try is the ghc-wpc project which has an interpreter which supports breakpoints, though you may need to hack little a bit to achieve your goals.

If I understand the new GHCJS backend correctly, it diverges from the normal compilation pipeline at STG (see the new StgToJS module subtree). Wouldn't that make it an excellent candidate to use GHC-WPC's machine-readable external STG representation, instead of hooking it directly into the GHC source tree?

Here the goal is to build a high level, easy to understand model for all GHC backend features. Validations is also required. Once we know the semantics of GHC primops and RTS features then it becomes possible to figure out how to compile Haskell programs to GRIN. I started the GHC-WPC project for this reason. GHC-WPC exports the STG intermediate representation for the whole Haskell program, and I wrote an STG interpreter from scratch in Haskell that can run any Haskell program. (i.e. GHC itself) The STG interpreter is the high level model for the GHC primop and RTS semantics. It implements all these in pure Haskell, it does not depend on GHC RTS at all.

I can easily debug any Haskell program with the external STG interpreter. https://www.youtube.com/watch?v=DkDUEd3pUyM https://github.com/grin-compiler/ghc-whole-program-compiler-project

Hello, I'm using the external STG interpreter to observe the runtime behaviour of Haskell programs. Lately I've added an initial call-graph construction feature that I plan to refine further. https://twitter.com/csaba_hruska/status/1417486380536582151 Is there anyone who has dynamic analysis related research ambitions and wants to study Haskell program runtime behaviour in detail? If so then it would be great to talk.

I haven't gotten my hands dirty yet, but really excited hearing GHC-WPC is going on!

Why didn't you mention GHC-WPC? It is also a backend sample. It exports enough information (STG + linker opts + c bits) to interpret the program or to generate a binary executable via the regular GHC codegen system. https://github.com/grin-compiler/ghc-whole-program-compiler-project

You could use the GHC codegen and RTS via the external STG IR. https://github.com/grin-compiler/ghc-whole-program-compiler-project

Remarks: 1. Strict functional languages can be expressed in STG without overhead, because STG has explicit liftedness control. In a strict language every data is unlifted or unboxed. 2. Supporting all GHC primops is not unrealistic. See the primop implementation in the external STG interpreter source code. Here is the implementation of the threading primops.

Mueval is based on hint, which is in turn based on the ghc library.

Yeah, that project is pretty much at the bottom of my list, unfortunately. My top projects these days are mgmt, klister, recursion-schemes, and hint... And that's already too much!

You can try using hint (instead of ghci) though I'm not sure it has the breakpoint functionality.

Have you tried hint?

with haskell.nix, well, you've found the github issue, you need to put the apecs package in the right nix incantation.

But the use case for that is for using a Haskell program A to catch errors in that same Haskell program A. For your use case, using a Haskell program A to automatically grade a Haskell program B, I recommend using the hint library instead, as it allows you to load code from external source files, run tests on them, and manipulate the error messages produced by ghc. (full disclosure: I am the maintainer of that library)

I am thinking of giving hint the ability to evaluate TemplateHaskell expressions. It would indeed be quite difficult to write an interpreter for all of Haskell, so my plan is to use the Exp's Show instance to produce a program which constructs and then splices that Exp, e.g. $(pure (InfixE (Just (LitE (IntegerL 1))) (VarE GHC.Num.+) (Just (LitE (IntegerL 1))))) is a Haskell expression which is equivalent to 1 + 1, so I should be able to ask hint to evaluate that to get 2 without having to write my own Haskell interpreter.

Yes please! Right now all of my open-source projects (most notably hint and recursion-schemes) are about to drop into barely-updated mode, and while I knew this would happen and have been working towards finding co-maintainers, I am now realizing that it wasn't enough. I think such a website would definitely have helped, and I am hoping that once it launches, I'll be able to use it to find some co-maintainers to tide over my projects until I become available again.

hint's API takes a string, not an AST (I plan to fix this). Internally, hint delegates to the ghc library, which does expose a parser which you can use if you want. hint exists to provide a friendlier API than the ghc library for interpreting Haskell code, but it does not expose a friendlier API for parsing Haskell code.