First release candidate for OCaml 4.14.1

The release of OCaml version 4.14.1 is (also) imminent.

This companion release to the OCaml 5.0.0 release will backport many safe bug
fixes from the currently experimental 5.0 branch to the stable 4.14 branch.
A full list of bug fixes is available below.

In order to ensure that the future release works as expected, we are testing
a release candidate during the upcoming weeks.

If you find any bugs, please report them here:

Issues · ocaml/ocaml · GitHub

Installation Instructions

The base compiler can be installed as an opam switch with the following commands on opam 2.1:

opam update
opam switch create 4.14.1~rc1

For previous version of opam, the switch creation command line is slightly more verbose:

opam update
opam switch create 4.14.1~rc1 --repositories=default,beta=git+

It might be also interesting to check the new support for parallelism by installing the domainslib library with

opam install domainslib

The source code for the release candidate is available at these addresses:

Fine-Tuned Compiler Configuration

If you want to tweak the configuration of the compiler, you can switch to the option variant with:

opam update
opam switch create <switch_name> ocaml-variants.4.14.1~rc1+options <option_list>

where <option_list> is a comma-separated list of ocaml-option-* packages. For instance, for a flambda and no-flat-float-array switch:

opam switch create 4.14.1~rc1+flambda+nffa ocaml-variants.4.14.1~rc1+options ocaml-option-flambda ocaml-option-no-flat-float-array

The command line above is slightly more complicated for opam versions before 2.1:

opam update
opam switch create <switch_name> --packages=ocaml-variants.4.14.1~rc1+options,<option_list> --repositories=default,beta=git+

In both cases, all available options can be listed with opam search ocaml-option.

Changes Since OCaml 4.14.0

Compiler user-interface and warnings:

  • #11184, #11670: Stop calling ranlib on created / installed libraries
    (Sébastien Hinderer and Xavier Leroy, review by the same)

Build System:

  • #11370, #11373: Don’t pass CFLAGS to flexlink during configure.
    (David Allsopp, report by William Hu, review by Xavier Leroy and
    Sébastien Hinderer)

  • #11487: Thwart FMA test optimization during configure
    (William Hu, review by David Allsopp and Sébastien Hinderer)

Bug Fixes:

  • #10768, #11340: Fix typechecking regression when combining first class
    modules and GADTs.
    (Jacques Garrigue, report by François Thiré, review by Matthew Ryan)

  • #11204: Fix regression introduced in 4.14.0 that would trigger Warning 17 when
    calling virtual methods introduced by constraining the self type from within
    the class definition.
    (Nicolás Ojeda Bär, review by Leo White)

  • #11263, #11267: caml/{memory,misc}.h: check whether _MSC_VER is defined
    before using it to ensure that the headers can always be used in code which
    turns on -Wundef (or equivalent).
    (David Allsopp and Nicolás Ojeda Bär, review by Nicolás Ojeda Bär and
    Sébastien Hinderer)

  • #11314, #11416: fix non-informative error message for module inclusion
    (Florian Angeletti, report by Thierry Martinez, review by Gabriel Scherer)

  • #11358, #11379: Refactor the initialization of bytecode threading,
    This avoids a “dangling pointer” warning of GCC 12.1.
    (Xavier Leroy, report by Armaël Guéneau, review by Gabriel Scherer)

  • #11387, module type with constraints no longer crash the compiler in presence
    of both shadowing warnings and the -bin-annot compiler flag.
    (Florian Angeletti, report by Christophe Raffalli, review by Gabriel Scherer)

  • #11392, #11392: assertion failure with -rectypes and external definitions
    (Gabriel Scherer, review by Florian Angeletti, report by Dmitrii Kosarev)

  • #11417: Fix regression allowing virtual methods in non-virtual classes.
    (Leo White, review by Florian Angeletti)

  • #11468: Fix regression from #10186 (OCaml 4.13) detecting IPv6 on Windows for
    mingw-w64 i686 port.
    (David Allsopp, review by Xavier Leroy and Sébastien Hinderer)

  • #11489, #11496: More prudent deallocation of alternate signal stack
    (Xavier Leroy, report by @rajdakin, review by Florian Angeletti)

  • #11516, #11524: Fix the deprecated_mutable attribute.
    (Chris Casinghino, review by Nicolás Ojeda Bär and Florian Angeletti)

  • #11194, #11609: Fix inconsistent type variable names in “unbound type var”
    (Ulysse Gérard and Florian Angeletti, review Florian Angeletti and
    Gabriel Scherer)

  • #11622: Prevent stack overflow when printing a constructor or record
    mismatch error involving recursive types.
    (Florian Angeletti, review by Gabriel Scherer)

  • #11732: Ensure that types from packed modules are always generalised
    (Stephen Dolan and Leo White, review by Jacques Garrigue)

  • #11737: Fix segfault condition in Unix.stat under Windows in the presence of
    multiple threads.
    (Marc Lasson, Nicolás Ojeda Bär, review by Gabriel Scherer and David Allsopp)

  • #11776: Extend environment with functor parameters in strengthen_lazy.
    (Chris Casinghino and Luke Maurer, review by Gabriel Scherer)

  • #11533, #11534: follow synonyms again in #show_module_type
    (this had stopped working in 4.14.0)
    (Gabriel Scherer, review by Jacques Garrigue, report by Yaron Minsky)

  • #11768, #11788: Fix crash at start-up of bytecode programs in
    no-naked-pointers mode caused by wrong initialization of caml_global_data
    (Xavier Leroy, report by Etienne Millon, review by Gabriel Scherer)


It’s good to see the monocore branch is still maintained :slight_smile:
I don’t think the effect system will be backported yet the 4.x branch is a great asset/option to have :camel: