Ocaml Versions Save

Bug fixes. See detailed list of changes.

• Breaking change: Marshal.Compression has been removed, compressed marshaling has been moved to an internal compiler library
• Bug fixes. See detailed list of changes.

OCaml 5.1.0 is still a relatively experimental release compared to the OCaml 4.14 branch. Some of the highlights in OCaml 5.1.0 are:

• Many runtime performance regression and memory-leaks fixes (dynlinking, weak array, weak hash sets, GC with idle domains, GC prefetching).
• Restored support for native code generation on RISC-V and s390x architectures.
• Restored Cygwin port.
• Reduced installation size (50% reduction)
• Compressed compilation artefacts (.cmi, .cmt, .cmti, .cmo, .cma files)
• 19 error message improvements
• 14 standard library functions made tail-recursive with Tail-Recursion-Modulo-Cons (TRMC), such as List.append and List.map.
• 57 new standard library functions
• More examples in the standard library documentation
• 42 bug fixes

OCaml 5.0.0 introduces a completely new runtime environment with support for shared memory parallelism and effect handlers.

As a language, OCaml 5 is fully compatible with OCaml 4 down to the performance characteristics of your programs. In other words, any code that works with OCaml 4 should work the same with OCaml 5.

The currently known exceptions to this rule are:

• the removal of many long-deprecated functions and modules
• changes to the internal runtime API
• the performance of ephemerons is currently (and temporarily) strongly degraded.

• Integrated support for "go to definitions" in Merlin.
• Standard library: new modules In_channel and Out_channel, many new functions in Seq module, UTF decoding and validation support for strings and bytes.
• Runtime optimisation: GC prefetching. Benchmarks show a speedup of around 20% in GC-heavy programs.
• Improved error messages in particular for module-level error.
• Deprecated functions and modules in preparation for OCaml 5. In particular, the Stream and Genlex modules are now deprecated.
• Type variables can be explicitly introduced in value and variant constructor declarations. For instance,

    val fold: ('acc -> 'elt -> 'acc) -> 'acc -> 'elt list -> 'acc
    type showable = Show: 'a * ('a -> string) -> showable

can now be written as

    val fold: 'acc 'elt. ('acc -> 'elt -> 'acc) -> 'acc -> 'elt list -> 'acc
    type showable = Show: 'a. 'a * ('a -> string) -> showable

• Tail-call with up to 64 arguments are now guaranteed to be optimized for all architectures.
• Experimental tail modulo cons (TMC) transformation

Regression fix release. See the detailed list of changes.

• Safe points: a multicore prerequisite that ensures that ocamlopt-generated code can always be interrupted.
• The best-fit GC allocation policy is the now default policy (and many other GCs improvements).
• Named existential type variables in pattern matching Showable (type a) (x, show : a * (a -> string)).
• Improved error messages for functor application and functor types.
• Let-punning for monadic let: let* x = x in can be shortened to let* x in.
• Module type substitutions SIG with module type T = F(X).S.
• Many other quality of life improvements
• Many bug fixes

See the detailed list of changes.

Bug fixes. See detailed list of changes.

• Major progress in reducing the difference between the mainline and multicore runtime
• A new configuration option ocaml-option-nnpchecker which emits an alarm when the garbage collector finds out-of-heap pointers that could cause a crash in the multicore runtime
• Support for macOS/arm64
• Mnemonic names for warnings
• Many quality of life improvements
• Many bug fixes

See the detailed list of changes

Bug fixes. See detailed list of changes