OCaml 5.1.1 - First Release Candidate
Two months (and half) after the release of OCaml 5.1.0, we have discovered three significant regressions in OCaml 5.1.0, affecting the packaging of executables, the typechecking of OCaml programs, and the performance of numerical codes.
Since those regressions affect many users and could have lasting effects, we have decided to cut a patch release of OCaml 5.1 with fixes for those issues next week.
To give time for opam packages to test this patch version, we have just published a first release candidate for OCaml 5.1.1 . The full list of changes in this release candidate is available below.
As a major exception to our policy for patch releases, OCaml 5.1.1 will
contain one breaking change in the standard library: the
Compression flag has
been removed from the
This drastic measure was taken because supporting zstd compression in the
standard library made zstd a dependency of all OCaml executables. Since the
compiler should not impose its dependency on end-users, the support for
compressed marshaling has been moved to a compiler internal library in 5.1.1.
This internally library might be released as an independent library in later
releases of OCaml but not in OCaml 5.1.1 to give us time to polish the library
integration and packaging.
The base compiler can be installed as an opam switch with the following commands on opam 2.1 and later:
opam switch create 5.1.1~rc1
The source code for the release candidate is also directly available on:
Fine-Tuned Compiler Configuration
If you want to tweak the configuration of the compiler, you can switch to the option variant with:
opam switch create <switch_name> ocaml-variants.5.1.1~rc1+options <option_list>
option_list is a space-separated list of
ocaml-option-* packages. For instance, for a
opam switch create 5.1.1~rc1+flambda+nffa ocaml-variants.5.1.1~rc1+options ocaml-option-flambda ocaml-option-no-flat-float-array
All available options can be listed with
opam search ocaml-option.
See full changelog
Changes in OCaml 5.1.1
Standard Library Dependency Fix:
- (breaking change) #12562, #12734, #12783: Remove the
Marshal.Compressionflag to the
Marshal.to_*functions introduced in 5.1 by #12006, as it cannot be implemented without risking to link -lzstd with all ocamlopt-generated executables. The compilers are still able to use ZSTD compression for compilation artefacts. (Xavier Leroy and David Allsopp, report by Kate Deplaix, review by Nicolás Ojeda Bär, Kate Deplaix, and Damien Doligez).
Type System Bug Fix:
- #12623, fix the computation of variance composition (Florian Angeletti, report by Vesa Karvonen, review by Gabriel Scherer)
GC Performance Regression Fixes
#12318: GC: simplify the meaning of custom_minor_max_size: blocks with out-of-heap memory above this limit are now allocated directly in the major heap. (Damien Doligez, report by Stephen Dolan, review by Gabriel Scherer)
#12439: Finalize and collect dead custom blocks during minor collection (Damien Doligez, review by Xavier Leroy, Gabriel Scherer and KC Sivaramakrishnan)
Miscellaneous Bug Fixes
#12757: Fix ocamlnat (native toplevel) by registering frametables correctly (Stephen Dolan, Nick Barnes and Mark Shinwell, review by Vincent Laviron and Sébastien Hinderer)