findlib sometimes cannot be built on Windows

[JasonGross]

I'm not sure if this is the right place to report this, but there seems to be a nondeterministic issue with the setup of OCaml/opam on Windows:

<><>Processing actions<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] The compilation of ocamlfind failed at "D:\\cygwin\\bin\\make.exe opt".
-> installed conf-findutils.1
-> installed conf-gmp.4
-> installed dune.3.3.1
#===ERRORwhile compiling ocamlfind.1.9.5====================================#
#context     2.0.10 | win32/x86_64 | ocaml-variants.4.11.1+mingw64c | git+https://github.com/fdopen/opam-repository-mingw.git#opam2
#path        D:/a/fiat-crypto/fiat-crypto/_opam/.opam-switch/build/ocamlfind.1.9.5
#command     D:\cygwin\bin\make.exe opt
#exit-code   2
#env-file    D:/.opam/log/ocamlfind-1[38](https://github.com/mit-plv/fiat-crypto/runs/7199984869?check_suite_focus=true#step:14:39)4-03b1a4.env
#output-file D:/.opam/log/ocamlfind-1384-03b1a4.out
### output ###
# for p in findlib; do ( cd src/$p; /usr/bin/make opt ) || exit; done
# make[1]: Entering directory '/cygdrive/d/a/fiat-crypto/fiat-crypto/_opam/.opam-switch/build/ocamlfind.1.9.5/src/findlib'
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c findlib_config.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_split.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_metatoken.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_meta.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_metascanner.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_topo.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_package_base.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c findlib.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_args.ml
# ocamlopt -I +compiler-libs -g -opaque  -I +unix -I +dynlink -c fl_lint.ml
# ocamlopt -I +compiler-libs -g -a -o findlib.cmxa findlib_config.cmx fl_split.cmx fl_metatoken.cmx fl_meta.cmx fl_metascanner.cmx fl_topo.cmx fl_package_base.cmx findlib.cmx fl_args.cmx fl_lint.cmx
# if [ 1 -gt 0 ]; then \
#     ocamlopt -I +compiler-libs -g -shared -o findlib.cmxs findlib_config.cmx fl_split.cmx fl_metatoken.cmx fl_meta.cmx fl_metascanner.cmx fl_topo.cmx fl_package_base.cmx findlib.cmx fl_args.cmx fl_lint.cmx; \
# fi
# ** Fatal error: Cannot run cygpath -m findlib.cmxs
# File "caml_startup", line 1:
# Error: Error during linking (exit code 2)
# make[1]: *** [Makefile:71: findlib.cmxa] Error 2
# make[1]: Leaving directory '/cygdrive/d/a/fiat-crypto/fiat-crypto/_opam/.opam-switch/build/ocamlfind.1.9.5/src/findlib'
# make: *** [Makefile:18: opt] Error 2
<><>Error report<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+- The following actions failed
| - build ocamlfind 1.9.5
+- 
+- The following changes have been performed (the rest was aborted)
| - install conf-findutils 1
| - install conf-gmp       4
| - install dune           3.3.1
+- 
[NOTE] Pinning command successful, but your installed packages may be out of sync.

https://github.com/mit-plv/fiat-crypto/runs/7199984869?check_suite_focus=true#step:14:68

[smorimoto]

CC: @ocaml/opam-repository

[kit-ty-kate]

Why pinging us? I'm not seeing any reference to cygpath in opam-repository.
I'd suggest to look into ocamlfind or opam-repository-mingw instead

[dra27]

The issue appears to be a sporadic failure when flexlink calls cygpath (I’ve seen it before, too). It’s possibly it can be fixed by adding a retry loop to the call (as it tends to succeed on the following call)