Feedback on this post is welcomed on Discuss!

We are happy to announce the second alpha release of opam 2.2.0. It contains some fixes and a new feature for Windows. You can view the full list in the release note.

This version is an alpha, we invite users to test it to spot previously unnoticed bugs to head towards the stable release.

Windows Support

The first alpha came with native Windows compatibility. This second alpha comes with a more simple init for Windows: we no longer rely on an already present Cygwin UNIX-like environment for Windows as a compatibility layer. During initialisation, opam now proposes to embed its own fully managed Cygwin install.

The main opam-repository Windows compliance is still a work in progress, we recommend to use existing compatible repository (originally from @fdopen) and 32/64 bit mingw-w64 packages (by @dra27).

How to Test opam on Windows

This alpha requires a preexisting Cygwin installation for compiling opam.

  1. Check that you have all dependencies installed:
    • autoconf, make, patch, curl
    • MinGW compilers: mingw64-x86_64-gcc-g++, mingw64-i686-gcc-g++
    • Or if you want to use the MSVC port of OCaml, you'll need to install Visual Studio or Visual Studio Build Tools
  2. Download & extract the opam archive
  3. In the directory launch make cold
  4. A coffee later, you now have an opam executable!
  5. Start your preferred Windows terminal (cmd or PowerShell), and initialise opam with the Windows sunset repository:
    • opam init git+

From here, you can try to install the sunset repository packages. If you find any bugs, please submit an issue. It will help opam-repository maintainers to add Windows repository packages into the main repository.

Hint: if you use the MinGW compiler, don't forget to add to your PATH the path to libc dlls (usually C:\cygwin64\usr\x86_64-w64-mingw32\sys-root\mingw\bin). Or compile opam with make cold CONFIGURE_ARGS=--with-private-runtime, and if you change opam location, don't forget to copy Opam.Runtime.amd64 (or Opam.Runtime.i386) with it.

Updates & fixes

  • opam var have now a more informative error message in case of package variable
  • opam lint: update Error 29 on package variables on filters to check also conflicts: field
  • opam admin lint: clean output when called not from a terminal
  • configure: error if no complementary compiler is found on Windows

Try it!

In case you plan a possible rollback, you may want to first backup your ~/.opam directory.

The upgrade instructions are unchanged:

  1. Either from binaries: run

    bash -c "sh <(curl -fsSL --version 2.2.0~alpha2"

    or download manually from the Github "Releases" page to your PATH.

  2. Or from source, manually: see the instructions in the README.

You should then run:

opam init --reinit -ni

Please report any issues to the bug-tracker.

Thanks for trying this new release out, and we hope you will enjoy the new features!