package opam-compiler

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Plugin to create switches using custom compilers


Dune Dependency






This plugin can manage switches using various sources for compilers, such as git branches, github PRs, etc

Published: 06 Oct 2020



A WIP opam plugin to manage compiler installations.

It can be used to create switches from various sources such as the main repository, ocaml-multicore, or a local directories. It can use tag names, branch names, or PR numbers to specify what to install.

Once installed, these are normal opam switches, and one can install packages in them. To iterate on a compiler feature and try opam packages at the same time, it supports to ways to reinstall the compiler: either a safe and slow technique that will reinstall all packages, or a quick way that will just overwrite the compiler in place.


This is an opam plugin. Once installed, it will be available globally using opam compiler ARGS. To install it, pin it to get a development version:

opam pin add opam-compiler 'git+'

Creating a switch

opam compiler create is a wrapper around opam switch create that will use a custom. The documentation can be found here, but as an example, the following is recognized:

# Use this pull request number
opam compiler create '#1234'

# Use this branch
opam compiler create 'myself/ocaml:mybranch'

It will try determine a switch name and description from the source name, but it is also possible to pass an explicit switch name:

# Use an explicit switch name
opam compiler create '#1234' --switch optimize-list-map

The resulting switch can be used like a normal switch: one can install packages, update them, etc.

By default, the compiler will be built using a plain ./configure command, which will create a vanilla compiler. It is possible to override this:

# Just build the bytecode compiler from a pull request
opam compiler create '#1234' --configure-command "./configure --disable-native-compiler"

Dependencies (8)

  1. lwt < "5.7.0"
  2. re
  3. lwt_ssl
  4. github-unix
  5. cmdliner < "1.1.0"
  6. bos
  7. ocaml >= "4.08.0"
  8. dune >= "2.5"

Dev Dependencies (1)

  1. alcotest >= "1.2.0" & with-test

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