* [Caml-list] Third alpha release of OCaml 5.5.0
@ 2026-03-26 13:21 Florian Angeletti
2026-04-20 14:47 ` [Caml-list] First beta " Florian Angeletti
0 siblings, 1 reply; 2+ messages in thread
From: Florian Angeletti @ 2026-03-26 13:21 UTC (permalink / raw)
To: caml-list
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Dear OCaml users,
With the progress of the ongoing stabilisation effort for OCaml 5.5.0, I am happy to
announce the third alpha release for OCaml 5.5.0.
The missing second alpha was unreleased due to an unforeseen interaction between
the relocatable compiler and bootstrapping. This issue is fixed in this third alpha.
Beyond this important change, compared to the first alpha this new alpha release
contains 2 code generation fixes, 3 type system fixes and one standard library
fix (see the Changelog below for a full list).
Thus, it looks like 5.5.0 is stabilizing quite well and we are planning to switch to
a beta release in the beginning of April.
More precisely, the ongoing progress on stabilising the ecosystem is tracked on
the opam readiness for 5.5.0 meta-issue at:
https://github.com/ocaml/opam-repository/issues/29463
There is also a companion alpha opam repository available for this alpha release
opam repo add alpha git+https://github.com/kit-ty-kate/opam-alpha-repository.git
which contains in-progress alpha releases of opam packages that are being updated for
OCaml 5.5.0 .
The final release is still planned for between May and June.
If you find any bugs, please report them here:
https://github.com/ocaml/ocaml/issues
If you are interested by the full list of new features and bug fixes, the
updated change log for OCaml 5.5.0 is available at:
https://github.com/ocaml/ocaml/blob/5.5/Changes
Happy hacking,
Florian Angeletti for the OCaml team.
Changes compared to the first alpha
-----------------------------------------------
## Compiler artefact fixes
- More bootstrap-friendly relocatable compiler
- A bootstrap to fix compiler-libs related issues reported by js_of_ocaml
## Code generation bug fixes
- #14583(https://github.com/ocaml/ocaml/issues/14583): fix bug in linear scan spilling heuristic that in certain situations
could lead to miscompilations.
(Nicolás Ojeda Bär, review by Vincent Laviron)
- #13693(https://github.com/ocaml/ocaml/issues/13693), #14514(https://github.com/ocaml/ocaml/issues/14514): s390x: fix heap corruption with libasmrun_shared.so caused
by PLT lazy binding trampoline saving FPRs into OCaml's fiber stack.
Replace @PLT calls with GOT-indirect calls in the s390x code emitter.
(Zane Hambly, review by David Allsopp and Xavier Leroy)
## Type system bug fixes
- #14434(https://github.com/ocaml/ocaml/issues/14434), #14652(https://github.com/ocaml/ocaml/issues/14652): Protect check_counter_example_pat against polymorphic types,
restoring type soundness.
(Stephen Dolan and Jacques Garrigue, report and review by Alistair O'Brien)
- #14603(https://github.com/ocaml/ocaml/issues/14603), [#14604](https://github.com/ocaml/ocaml/issues/14604): avoid Ctype.apply failures when mixing
polymorphic types and unboxed constructors.
(Gabriel Scherer and Stefan Muenzel, report by Brandon Stride,
review by Florian Angeletti)
- #14626(https://github.com/ocaml/ocaml/issues/14626), [#14675](https://github.com/ocaml/ocaml/issues/14675): take in account module-dependent functions when
determining if an optional argument is non-erasable.
(Alistair O'Brien and Florian Angeletti, review by Gabriel Scherer)
## Standard library fix
- #14635(https://github.com/ocaml/ocaml/issues/14635): Fix a bug in `caml_floatarray_gather` that would cause
the result of `Float.Array.sub`, `Float.Array.append`, `Float.Array.concat`
(when empty) not to be equal to `[||]`.
(Marc Lasson, review by Gabriel Scherer)
## Documentation update
- #13590(https://github.com/ocaml/ocaml/issues/13590): Document automatic command-line expansion of `*` and `?` wildcards by
the runtime under Windows.
(Benjamin Sigonneau, review by Nicolás Ojeda Bär)
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* [Caml-list] First beta release of OCaml 5.5.0
2026-03-26 13:21 [Caml-list] Third alpha release of OCaml 5.5.0 Florian Angeletti
@ 2026-04-20 14:47 ` Florian Angeletti
0 siblings, 0 replies; 2+ messages in thread
From: Florian Angeletti @ 2026-04-20 14:47 UTC (permalink / raw)
To: caml-list
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Dear OCaml users,
With most developer tools available and the good stability of the
compiler, I am happy to announce the first beta release of OCaml
5.5.0.
Compared to the last alpha, this new version improves the manpage for
ocamlopt and fixes:
- two runtime bugs (for ephemerons and the bytecode interpreter)
- two type system bugs (for classes and module-dependent functions)
- three warning or error message bugs
(See the Changelog below for a full list).
Concerning the associated compiler tools, most of them are already
available (as least in a preview version), and there are patches in
progress for the missing ones. You can track the last remaining
update efforts on
https://github.com/ocaml/opam-repository/issues/29463
Thus, it should be safe to test your libraries and programs with the
new version OCaml 5.5.0 version in preparation of the final release.
If everything goes well, we might see a release in May.
If you find any bugs, please report them here:
https://github.com/ocaml/ocaml/issues
If you are interested by the full list of new features and bug fixes, the
updated change log for OCaml 5.5.0 is available at:
https://github.com/ocaml/ocaml/blob/5.5/Changes
Happy hacking,
Florian Angeletti for the OCaml team.
Installation Instructions
--------------------------
The base compiler can be installed as an opam switch with the following commands
on opam 2.1 and later:
opam update
opam switch create 5.5.0~beta1
The source code for the beta is also available at these addresses:
* GitHub: https://github.com/ocaml/ocaml/archive/5.5.0-beta1.tar.gz
* OCaml archives at Inria: https://caml.inria.fr/pub/distrib/ocaml-5.5/ocaml-5.5.0~beta1.tar.gz
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.5.5.0~beta1+options <option_list>
where `option_list` is a space separated list of `ocaml-option-*` packages. For instance, for a flambda and no-flat-float-array switch:
opam switch create 5.5.0~beta1+flambda+nffa ocaml-variants.5.5.0~beta1+options ocaml-option-flambda ocaml-option-no-flat-float-array
All available options can be listed with `opam search ocaml-option`.
Changes compared to the last alpha
-----------------------------------------------
* Documentation Update
- #14684(https://github.com/ocaml/ocaml/issues/14684): Improve ocamlopt's manual page
(Samuel Hym, review by Florian Angeletti)
* Runtime Fixes
- #14644(https://github.com/ocaml/ocaml/issues/14644), #14647(https://github.com/ocaml/ocaml/issues/14647): Fix a bug related to unhandled effects in bytecode.
(Vincent Laviron, report by Thibaut Mattio,
review by Nicolás Ojeda Bär, Stephen Dolan and Olivier Nicole)
- #14349(https://github.com/ocaml/ocaml/issues/14349), #14718(https://github.com/ocaml/ocaml/issues/14718): runtime, fix in the orphaning of ephemerons
(Gabriel Scherer, review by Olivier Nicole and Damien Doligez,
report by Jan Midtgaard)
* Type System Fixes
- #14557(https://github.com/ocaml/ocaml/issues/14557), #12150(https://github.com/ocaml/ocaml/issues/12150), #14696(https://github.com/ocaml/ocaml/issues/14696): ensure that the self type of class cannot escape
through type constraints.
(Leo White, review by Florian Angeletti)
- #14667(https://github.com/ocaml/ocaml/issues/14667): enable application related warnings for module-dependent functions
(Florian Angeletti, review by Gabriel Scherer)
* Error Messages and Warning Fixes
- #14690(https://github.com/ocaml/ocaml/issues/14690): Fix `Name_type_mismatch` error message when the expected type is an
alias: print the expanded path on the right-hand side of the equality, not
the alias twice.
(Weixie Cui, review by Florian Angeletti)
- #14719(https://github.com/ocaml/ocaml/issues/14719), #14721(https://github.com/ocaml/ocaml/issues/14721): compute arity correctly for module-dependent function
(Florian Angeletti, report by Jeremy Yallop, review by Stefan Muenzel)
- #14655(https://github.com/ocaml/ocaml/issues/14655), #14691(https://github.com/ocaml/ocaml/issues/14691): check for size overflow in caml_ba_reshape
(Stephen Dolan, review by Xavier Leroy)
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