OCaml 4.10.1, first release candidate

Dear OCaml users,

The release of OCaml version 4.10.1 is imminent. @octachron and the rest of the compiler dev team have created a release candidate that you can test.

The source code is available at these addresses:


The compiler can also be installed as an OPAM switch with the following commands:

$ opam update
$ opam switch create 4.10.1+rc1 --repositories=default,beta=git://github.com/ocaml/ocaml-beta-repository.git

We want to know about any bugs. Please report them here:

If every goes well, the full release should follow next week.

— OCaml 4.10.1 changes —

This version contains a collection of configuration, build systems and runtime fixes:

Runtime system:

  • #9344, #9368: Disable exception backtraces in bytecode programs
    built with “-output-complete-exe”. At the moment, such programs do
    not embed debug information and exception backtraces where causing
    them to crash.
    (Jérémie Dimino, review by Nicolás Ojeda Bär)

Build system:

  • #9531: fix support for the BFD library on FreeBSD
    (Hannes Mehnert, review by Gabriel Scherer and David Allsopp)

Bug fixes:

  • #9068, #9437: ocamlopt -output-complete-obj failure on FreeBSD 12
    (Xavier Leroy, report by Hannes Mehnert, review by Sébastien Hinderer)

  • #9165: Add missing -function-sections and -O3 flags in Makefiles.
    (Greta Yorsh, review by David Allsopp)

  • #9495: fix a bug where bytecode binaries compiled with -output-complete-exe
    would not execute at_exit hooks at program termination (in particular,
    output channels would not be flushed).
    (Nicolás Ojeda Bär, review by David Allsopp)

  • #9714, #9724: Use the C++ alignas keyword when compiling in C++ in MSVC.
    Fixes a bug with MSVC C++ 2015 onwards.
    (Antonin Décimo, review by David Allsopp and Xavier Leroy)

  • #9736, #9749: Compaction must start in a heap where all free blocks are
    blue, which was not the case with the best-fit allocator.
    (Damien Doligez, report and review by Leo White)


  • #9552: restore ocamloptp build and installation
    (Florian Angeletti, review by David Allsopp and Xavier Leroy)