Re: Meaning of -i and -hidir

The behavior of `-hidir` and `-i` changed in response to this issue: https://gitlab.haskell.org/ghc/ghc/-/issues/16500 We just ran into this and I think the change is unfortunate. I don't think `-hidir` (a flag about output) should override the input search flag. I would like it to at least merge the two so it searches both the `-hidir` and the `-i`s rather than overriding. Reverting the change would be fine too (I think) because you can always specify the same path as `-hidir` and `-i`. As it is now, you can control *both* the input and the output. On Sat, Oct 23, 2021 at 4:26 PM Carter Schonwald wrote:

Could be! I’m far from a computer much of this week

On Sat, Oct 23, 2021 at 2:36 PM Brandon Allbery wrote:

...

I would expect that to be -I and for -i to specify module paths (which might well mean .hi).

On Sat, Oct 23, 2021 at 2:32 PM Carter Schonwald < carter.schonwald@gmail.com> wrote:

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I would assume the -i is for include c header search paths but I could be wrong

On Sat, Oct 23, 2021 at 6:00 AM Oleg Grenrus wrote:

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This looks like a bug.

-hidir documentation says

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Redirects all generated interface files into ⟨dir⟩, instead of the default. Please also note that when doing incremental compilation (by ghc --make or ghc -c), this directory is where GHC looks into to find interface files.

And documentation for -i doesn't mention looking for interface files.

So by doing

% ghc -dynamic-too -c lib/Lib.hs -odir odir -hidir hidir_Lib % ghc -dynamic-too -c Main.hs -odir odir -hidir hidir_Main -ihidir_Lib 1 % ghc odir/Lib.o odir/Main.o -o Demo % ./Demo True

everything compiles, TH is run, and demo works. The result files are

% find . . ./Demo ./Main.hs ./hidir_Main ./hidir_Main/Main.dyn_hi ./hidir_Main/Main.hi ./odir ./odir/Main.dyn_o ./odir/Main.o ./odir/Lib.dyn_o ./odir/Lib.o ./hidir_Lib ./hidir_Lib/Lib.dyn_hi ./hidir_Lib/Lib.hi ./lib ./lib/Lib.hs

---

The confusing error is caused by Lib module in libiserv: https://hackage.haskell.org/package/libiserv which GHC picks!

If we rename your Lib module to Library, the error is way better: Could not find module ‘Library’

I also tried using same -hidir when compiling both modules, then GHC still cannot find the Library interface, even the documentation says it should.

Please open a GHC issue at https://gitlab.haskell.org/ghc/ghc/-/issues

- Oleg On 22.10.2021 19.16, Domínguez, Facundo wrote:

Dear devs,

I'm confused about the meaning of -hidir and -i. Here's my experiment with both ghc-9.2.0 and ghc-8.10.4.

...

$ find ./Main.hs ./lib/Lib.hs

$ ghc -dynamic-too -c lib/Lib.hs -odir odir -hidir hidir_Lib

$ ghc -dynamic-too -c Main.hs -odir odir -ihidir_Lib -hidir hidir_Main

Main.hs:3:1: error: Bad interface file: hidir_Main/Lib.hi hidir_Main/Lib.hi: openBinaryFile: does not exist (No such file or directory) | 3 | import Lib | ^^^^^^^^^^

If I only use -hidir, it still fails with another error

...

$ ghc -dynamic-too -c Main.hs -odir odir -hidir hidir_Lib

Main.hs:7:29: error: Variable not in scope: f | 7 | main = print $(runIO (print f) >> [| True |]) | ^

If I use both -i and -hidir pointing to the same folder, then it works!

...

$ ghc -dynamic-too -c Main.hs -odir odir -ihidir_Lib -hidir hidir_Lib

Now, is this behavior a bug or a feature? And if it is a bug, what is the expected behavior?

Programs copied below.

Thank you! Facundo

...

$ cat lib/Lib.hs module Lib where

f :: Int f = 1

$ cat Main.hs {-# LANGUAGE TemplateHaskell #-}

import Lib import Language.Haskell.TH http://language.haskell.th/

main :: IO () main = print $(runIO (print f) >> [| True |])

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-- brandon s allbery kf8nh allbery.b@gmail.com

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