Copying opam switches – it should Just Work™

David Allsopp (Tarides UK)

OCaml’s ecosystem centres around compilation from source code, rather than precompiled binaries. The compiler itself is only provided as a source distribution and OCaml’s official package repository in opam also manages source code packages only. Even on a high spec. machine, compiling OCaml from source code takes a minute, for many users, it’s slower. The recommended workflows1 for OCaml development focus on having a compiler installation for each individual project. Various solutions are available downstream for trying to reduce the set-up required to get a working OCaml compiler for a project ranging from predistributed binaries to rewriting binary artefacts. This talk presents an unexpected journey which began as a series of fixes to eliminate some esoteric failures of OCaml programs to launch, yet ended with a series of relatively simple changes to OCaml which allow various downstream workarounds to be brought home to upstream OCaml.