Explicit executable dependencies and cross-compilation

[TheLortex]

When packages use configure scripts, they usually have something like this:

rule
  (targets ...)
  (deps discover.exe)
  (action (run ./discover.exe)))

As of today, this does not work in a cross-compilation setting, because it adds a dependency towards config.exe in the cross-compiled workspace, which is not a good thing (and fails due to missing unix, usually).

My guess is that dune performs the following expansions:

• (deps discover.exe) -> (deps %{dep:discover.exe}) -- pointing to the cross-compiled workspace
• (run ./discover.exe) -> (run %{exe:./discover.exe}) -- pointing to the host workspace (as intended)

A simple workaround is to remove the explicit deps field towards executables, but that might seem counter-intuitive to some package maintainers so I was wondering if this behavior was intended. Thanks !

Using dune master branch and ocaml 4.11.1

[TheLortex]

For reference, here is a small list of packages where I've encountered the issue, along with the workaround commit:

• parsexp: TheLortex/parsexp@a6d9b85
• base: TheLortex/base@62e0a06
• cohttp: TheLortex/ocaml-cohttp@364c1ab
• num: TheLortex/num@8c97ae7
• magic-mime: TheLortex/ocaml-magic-mime@e1791dc
• uri: TheLortex/ocaml-uri@8b1b158

[rgrinberg]

We discussed this in the meeting, and we think that modifying the build rules as you're doing now is the way to go.

We agree that it's unfortunate that the two forms seem interchangeable to the user, but we're not sure how to guide them to use %{exe:..} over %{dep:..} for running the executable.

[TheLortex]

Thank you for the confirmation. I'll move forward updating packages that have this issue then.