regression (3.7): bls12-381-unix.0.4.1: No implementations provided for the following modules

[emillon]

Hi,

Once again, this is a regression between 3.6.2 and 3.7.0~alpha1. bls12-381-unix.0.4.1 fails with this error:

        Bls12_381__Fq12 referenced from src/unix/bls12_381_unix.cmxa(Bls12_381__Pairing),
           test/unix/.test_fr.eobjs/native/dune__exe__Test_pairing.cmx
         Bls12_381__G1 referenced from src/unix/bls12_381_unix.cmxa(Bls12_381__Pairing),
           test/unix/.test_fr.eobjs/native/dune__exe__Test_pairing.cmx
         Bls12_381__Fr referenced from src/unix/bls12_381_unix.cmxa(Bls12_381__G2),
           test/unix/.test_fr.eobjs/native/dune__exe__Test_pairing.cmx

I bisected that to fb085c0 (#6594).

The dune file has a combination of private_modules and virtual libraries:

(library
 (public_name bls12-381-unix)
 (name bls12_381_unix)
 (implements bls12-381)
 (modules fr g1 g2 pairing fq12 rustc_bls12_381_stubs rustc_bls12_381_bindings)
 (instrumentation (backend bisect_ppx))
 (private_modules Rustc_bls12_381_stubs Rustc_bls12_381_bindings)
 (libraries zarith ctypes ctypes.foreign bls12-381-gen bls12-381)
 (library_flags :standard -linkall -ccopt -pthread)
 (foreign_stubs
  (language c)
  (names rustc_bls12_381_ctypes_c_stubs)
  (flags (-I%{env:OPAM_SWITCH_PREFIX=}/lib/tezos-rust-libs))
 )
 (c_library_flags (-L%{env:OPAM_SWITCH_PREFIX=}/lib/tezos-rust-libs -lrustc_bls12_381 -lpthread))
)

This might be the same as #7015 or #7018.
Thanks.

[rgrinberg]

Hmm, this one seems different than the others. I'll investigate.

[rgrinberg]

@emillon if you have some time, turning this into a cram test would be quite helpful.

[emillon]

#7038 fixes this; do you still think a repro would be useful?

[rgrinberg]

I think so. A lot of improvements can be made to the closure so improving the test suite would be worthwhile.

[rgrinberg]

Could you post the full command that failed if you still have it?

[emillon]

The failing command is dune runtest -p bls12-381-unix. You can find a log here.

The missing modules are indeed not part of the linked library:

$ (cd _build/default && /home/etienne/scratch/repro-dune/_opam/bin/ocamlopt.opt -w -40 -g
-a -o src/unix/bls12_381_unix.cmxa
-cclib -lbls12_381_unix_stubs -cclib -L/home/etienne/scratch/repro-dune/_opam/lib/tezos-rust-libs -cclib -lrustc_bls12_381 -cclib -lpthread -linkall -ccopt -pthread
src/unix/.bls12_381_unix.objs/native/bls12_381__bls12_381_unix__.cmx
src/unix/.bls12_381_unix.objs/native/bls12_381__bls12_381_unix__Rustc_bls12_381_stubs.cmx 
src/unix/.bls12_381_unix.objs/native/bls12_381__bls12_381_unix__Rustc_bls12_381_bindings.cmx 
src/unix/.bls12_381_unix.objs/native/bls12_381__G2.cmx
src/unix/.bls12_381_unix.objs/native/bls12_381__Pairing.cmx 
src/unix/.bls12_381_unix.objs/native/bls12_381.cmx)

This is wrong because Fq12 is listed in (modules). I'll try to make a smaller repro (which in particular does not depend on rust).

[emillon]

(still reducing the problem)

[emillon]

Got it. Here it is as a standalone dune file, though this can be exploded in various files or a cram test:

(subdir
 virtual
 (library
  (name virtual)
  (virtual_modules a b))
 (rule
  (write-file a.mli ""))
 (rule
  (write-file b.mli "")))

(subdir
 impl
 (library
  (name impl)
  (implements virtual)
  (library_flags :standard -linkall))
 (rule
  (write-file a.ml ""))
 (rule
  (write-file b.ml "include A")))

(test
 (name link)
 (libraries impl))

(rule
 (write-file link.ml ""))

% dune runtest
File "_none_", line 1:             
Error: No implementations provided for the following modules:
         Virtual__A referenced from impl/impl.cmxa(Virtual__B)