Dream tutorial failing on Windows Opam 2.2.0~beta with cygwin due to linking issue

[sophie-xhonneux]

I try to run the first tutorial of dream on Windows and it fails to build with dune with the following error:

3 |  (name main)
           ^^^^
/bin/bash: C:UsersnameAppDataLocalTempbuild_33ef3c_dunelongcmd71db52: No such file or directory
** Fatal error: Error during linking

File "caml_startup", line 1:
Error: Error during linking (exit code 2)

my opam switch looks as follows:

→  webtutorial  arch-x86_64.1,ocaml-base-compiler.5.1.0,ocaml-options-vanilla.1,system-mingw.1  ocaml-base-compiler = 5.1.0 | ocaml-system = 5.1.0

I installed Ocaml on windows by following https://opam.ocaml.org/blog/opam-2-2-0-windows/

[maxRN]

Can you try with version 2.2.1? https://opam.ocaml.org/blog/opam-2-2-1/ I know there have been some bug fixes there, not sure if those address this specific issue, but it might be worth a shot.

[sophie-xhonneux]

I managed to resolve the issue by installing cygwin separately (rather than managed through opam) and making sure it's path came before C:\Windows\System32\base.exe.

I think it's the same issue as described here https://discuss.ocaml.org/t/windows-compiler-support-in-opam-2-2-0-beta2/14648/22

Basically the command gets too long eventually and flexdll relies on the bash.exe see also ocaml/flexdll#138

Not a great solution, but good enough for now :)