Per-project linker choice is not honoured

[Kleidukos]

Context:

I'm converting a project to cabal, and it has many shell scripts with such invocations:

export USE_LINKER=lld

ghc -Wall -i../.. \
  -odir ../../build \
  -hidir ../../build \
  ../../libiced_hs.a \
  ${USE_LINKER+-optl -fuse-ld="$USE_LINKER"} \
  main.hs

(https://github.com/ibaryshnikov/iced-hs/blob/5c7ad27deba8fad4f29df7d16d67881c21ca1508/examples/radio/build.sh#L7-L12)

However it's unclear to me how to create a working setup where lld is used reliably.

## Reproducer

$ git clone https://github.com/haskell-text/text-display
$ cd text-display
$ git switch use-lld
$ cabal build

<no location info>: error:
    Warning: Couldn't figure out linker information!
             Make sure you're using GNU ld, GNU gold or the built in OS X linker, etc.
collect2: fatal error: cannot find ‘ld’
compilation terminated.
`gcc' failed in phase `Linker'. (Exit code: 1)

What is the preferred workflow these days?

[TeofilC]

Incidentally I have recently created a GHC issue asking the same question but about GHC: https://gitlab.haskell.org/ghc/ghc/-/issues/25726

[TeofilC]

Btw I think the issue is that in your case you are passing -fuse-ld=lld to your linker, which is probably ld.bfd or ld.gold. But you are meant to pass it to gcc.

I saw the same message and this is what was causing it for me.