Dear OCaml users, 

We have the pleasure of celebrating the birthday of Blaise Pascal by announcing the release of OCaml version 5.5.0. 

Some of the highlights in OCaml 5.5.0 are: 

### Module-dependent Functions 

Modules can now be used as function arguments in a form of lightweight functors. 

For instance, we can define a function for printing a map generated by 
the `Map.Make` functor: 

let pp_map (module M: Map.S) pp_key pp_v ppf set = 
if M.is_empty set then 
Format.fprintf ppf "ø" 
else 
let pp_sep ppf () = Format.fprintf ppf ",@ " in 
let pp_binding ppf (k,v) = 
Format.fprintf ppf "@[%a@ =@ %a@]" pp_key k pp_v v 
in 
Format.fprintf ppf "@[{@ %a@ }@]" 
(Format.pp_print_seq ~pp_sep pp_binding) (M.to_seq set) 


We can then apply this function on a string map 

module String_map = Map.Make(String) 

with 

let () = 
let m = String_map.of_list ["Zero", "Zero"; "One", "Un"] in 
let pp_str = Format.pp_print_string in 
Format.printf "%a@." 
(pp_map (module String_map) pp_str pp_str) m 

Compared to first-class modules, the type of the function `pp_map` 

type 'a printer = Format.formatter -> 'a -> unit 
val pp_map: (module M: Map.S) -> M.key printer -> 'a printer -> 'a M.t printer 

is dependent over the value of the module `S`, and thus the function can only 
applied over a statically known module: 

let f (): (module Map.S) = 
if Random.bool () then 
(module Map.Make(Int)) 
else 
(module Map.Make(Float)) 
let fail = pp_map (f ()) 

Error: This expression has type 
(module M : Map.S) -> 
(Format.formatter -> M.key -> unit) -> 
(Format.formatter -> 'a -> unit) -> Format.formatter -> 'a M.t -> unit 
but an expression was expected of type (module Map.S) -> 'b 
The module M would escape its scope 
This function is module-dependent. The dependency is preserved 
when the function is passed a static module argument (module M : S) 
or (module M). Its argument here is not static, so the type-checker 
tried instead to change the function type to be non-dependent. 


### Relocatable Compiler 

A compiler installation can now be moved or copied with no risk 
of hard-to-debug errors due to mixing incompatible bytecode runtime interpreters. 

In practice, this means that creating a local switch when there is a 
global switch with the same compiler version and configuration 
available can be done by cloning the global switch rather than 
recompiling the whole compiler. 

This should considerably reduce the time required to create 
new local opam switches out-of-the-box. 

### Polymorphic Functions as Function Arguments 

Higher-rank polymorphic functions can now be defined directly by 
using an explicit type annotation in a function argument 

let apply_map (map: 'a 'b. ('a -> 'b) -> 'a list -> 'b list) = 
map string_of_int [1;2;3], map List.singleton ["x"; "y"] 
let _ = apply_map List.map 

Previously defining such a function required going through either a record or an object 
with a polymorphic field or methods 

type map = { map: 'a 'b. ('a -> 'b) -> 'a list -> 'b list } 
let apply_map {map} = 
map string_of_int [1;2;3], map List.singleton ["x"; "y"] 

### Search and Replace Substring Functions 

The `String` module has been extended with many functions 
for searching and replacing substrings inside a string. 

let _true = String.includes ~affix:"aba" "abbaba" 
let sentence = String.replace_all ~sub:"𝄽" ~by:"word" "A 𝄽 is re𝄽ed" 

The substring search is using the 2-way string matching algorithm 
which has the advantage of requiring constant space memory overhead 
independently of the needle size. 

### Generalised Local Definitions 

It is now always possible to define locally a type, 
a class, a module type or any kind of item that can be defined 
globally: 

let mandelbrot n x = 
let type t = Converge | Escape of int in 
... 
match orbit n x with 
| Converge -> 0 
| Exit_at n -> colorize n 

### External Types 

When interfacing with foreign function libraries, it is now possible 
to define external type 

type int_gmp = external "mpz_t" 
type float_gmp = external "mpf_t" 

Compared to an abstract type definition, the external type name 
"mpz_t" (resp. `mpf_t`) makes the type distinguishable from any 
non-abstract types or external types with a different name. 

In particular, this makes FFI types better behaved when combined with 
Generalised Abstract Data Types (GADTs). For instance, The typechecker 
is able to prove that 

let ok: (int_gmp,[` A] ) Type.eq -> _ = function _ -> . 

is a total function because the external type `int_gmp` is not compatible 
with a polymorphic variant type. 

### Warning: Abstract types in the current module 

The astute reader has probably noticed in the definition above that, 
in OCaml 5.4.0, the typechecker does accept 

type int_gmp 
let ok: (int_gmp, [` A] ) Type.eq -> _ = function _ -> . 

as total. 

Indeed until OCaml 5.5.0, abstract types defined in the current module 

type a 
type b 

were considered as unique and provably different 

let f: 'x. (a,b) Type.eq -> 'x = function _ -> . 

However, this special rule for local definition of abstract types was 
very brittle. As soon as one moved outside of the current module, it 
was no longer possible to prove that the types were different. 

module M = struct 
type a 
type b 
end 
let fail: 'x. (M.a,M.b) Type.eq -> 'x = function _ -> . 

Error: This match case could not be refuted. 
Here is an example of a value that would reach it: Equal 

This special typechecking rule has been removed in OCaml 5.5.0. If you were relying on it, 
for instance, because you used an abstract type as type-level label in a GADTs, you 
can change your abstract type definition to a possibly private abbreviation of a polymorphic variant 

type a = private [`A] 
type b = [`B] 

or a (possibly private) sum type 

type a = A 
type b = private B 

If you were using an abstract type as both a type-level label and a FFI type, you 
can now use an external type definition which will give you a provably distinct type 
even outside of the current module. 

### GC improvements 

Some of the ongoing work to improve the pacing of the garbage 
collector has been integrated in OCaml 5.5.0, two of the important 
changes in OCaml 5.5 GC are 

- the addition of a sweep-only phase at the start of major GC 
- the addition of an idle phase to smooth the behaviour of the GC 
at the start. 

### Many incremental changes 

- The Windows implementation is no more reliant on Winpthreads 
- Around 60 new standard library functions 
- Around 90 various improvements 
- A dozen of documentation updates 
- Around 40 bug fixes 

Please report any unexpected behaviours on the [OCaml issue 
tracker](https://github.com/ocaml/ocaml/issues) and post any questions or 
comments you might have on our discussion forums at 

- [ https://discuss.ocaml.org/ | https://discuss.ocaml.org ] 

The full list of changes can be found in the full changelog. 

Happy hacking, 
Florian Angeletti for the OCaml team. 


Installation Instructions 
------------------------------- 

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

opam update 
opam switch create 5.5.0 

The source code for the release is also directly available on: 

- GitHub: https://github.com/ocaml/ocaml/releases/download/5.5.0/ocaml-5.5.0.tar.gz 
- OCaml archives at Inria: https://caml.inria.fr/pub/distrib/ocaml-5.5/ocaml-5.5.0.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+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+flambda+nffa ocaml-variants.5.5.0+options ocaml-option-flambda ocaml-option-no-flat-float-array 


Changes in OCaml 5.5.0 
--------------------------------- 

### Language features: 

* (*breaking change*) [#13681](https://github.com/ocaml/ocaml/issues/13681), [#13682](https://github.com/ocaml/ocaml/issues/13682), [#13683](https://github.com/ocaml/ocaml/issues/13683), [#13684](https://github.com/ocaml/ocaml/issues/13684), [#13275](https://github.com/ocaml/ocaml/issues/13275) : 
Introduce a new type `(module M : S) -> t[M]` that corresponds to 
module-dependent functions (also called: modular explicits). 
val mapM: (module M : Monad) (f : 'a -> 'b M.t) : 'a list -> 'b list M.t 
(Samuel Vivien review by Leo White, Gabriel Scherer, Florian Angeletti, 
Jacques Garrigue and Stephen Dolan) 

- [#14040](https://github.com/ocaml/ocaml/issues/14040): generalize the constructs `let module`, `let exception` and `let open` 
to most other structure items, for example: 
let type t = ... in ... 
let type Effect.t += Yield in ... 
(Nicolás Ojeda Bär, review by Valentin Gatien-Baron) 

- [#13806](https://github.com/ocaml/ocaml/issues/13806): Enable the use of function parameters with polymorphic types. 
let extract (getter : 'a . 'a t -> 'a) = ... 
let runST (m : 's . ('s, 'a) ST.t) : 'a = ... 
(Ulysse Gérard, Leo White, review by Florian Angeletti, Samuel Vivien, Gabriel 
Scherer and Jacques Garrigue) 


* (*breaking change*) [#13712](https://github.com/ocaml/ocaml/issues/13712): Introduce a new kind `Type_external` and syntax 
`type t = external "name"` to discriminate external types from other types 
and each other. This PR turns primitive types into external and removes the 
past behavior of discriminating abstract types defined in the current module. 
(Takafumi Saikawa, Jacques Garrigue, review by Richard Eisenberg) 

* (*breaking change*) [#14009](https://github.com/ocaml/ocaml/issues/14009): infix extension points/attributes appearing in local structure items, 
eg `let module%foo[@bar] ... in ...` are attached to the AST node of the 
corresponding structure item (similar to their global counterparts) and no 
longer to the enclosing `let` expression. Extension points/attributes that 
are to be attached to the enclosing `let` expression are to be written next to 
the `let` keyword, eg `let%foo[@bar] module ... in ...`. The same holds for 
`let exception` and `let open`. 
(Nicolás Ojeda Bär, review by Gabriel Scherer) 

- [#14029](https://github.com/ocaml/ocaml/issues/14029): Recognize `%identity` as nonexpansive 
(Stephen Dolan and Olivier Nicole, review by Hugo Heuzard, Jacques Garrigue, 
Jeremy Yallop, and Gabriel Scherer) 

### Standard library: 

- [#13372](https://github.com/ocaml/ocaml/issues/13372): New Format and Printf printf-like functions that accept a 
heterogeneous list as arguments. 
Format.lprintf "@[%s@ %d@]@." [ "x ="; 1 ] 
(Leonardo Santos, review by Florian Angeletti and Gabriel Scherer) 

- [#14437](https://github.com/ocaml/ocaml/issues/14437): Add String.split_{first,last,all} and String.rsplit_all 
split_first: sep:string -> string -> (string * string) option 
split_all: sep:string -> drop:(string -> bool) -> string -> string list 
(Daniel Bünzli, review by Nicolás Ojeda Bär and Florian Angeletti) 

- [#14436](https://github.com/ocaml/ocaml/issues/14436): Add String.replace_{first,last,all} 
replace_first: sub:string -> by:string -> ?start:int -> string -> string 
(Daniel Bünzli, review by Nicolás Ojeda Bär, Ali Caglayan and 
Florian Angeletti) 

- [#14439](https://github.com/ocaml/ocaml/issues/14439): Add String.includes, to complete the trio: 
starts_with: prefix:string -> string -> bool 
ends_with: suffix:string -> string -> bool 
includes: affix:string -> string -> bool 
(Daniel Bünzli, review by Nicolás Ojeda Bär and Olivier Nicole) 

- [#14381](https://github.com/ocaml/ocaml/issues/14381): Add String.find_{first,last}_index, String.find_{first,last}, 
String.[r]find_all. 
find_first_index: (char -> bool) -> ?start:int -> string -> int option 
(Daniel Bünzli, review by Nicolás Ojeda Bär, Ali Caglayan and 
Florian Angeletti) 

- [#14438](https://github.com/ocaml/ocaml/issues/14438): Add String.is_empty 
(Daniel Bünzli, review by Nicolás Ojeda Bär and Gabriel Scherer) 

- [#14440](https://github.com/ocaml/ocaml/issues/14440): Add String.of_char 
(Daniel Bünzli, review by Nicolás Ojeda Bär and Gabriel Scherer) 

- [#14352](https://github.com/ocaml/ocaml/issues/14352): Add String.{drop,take,cut}_{first,last}. 
take_first: int -> string -> string 
cut_first: int -> string -> string * string 
(Daniel Bünzli, review by David Allsopp, Nicolás Ojeda Bär and 
Vincent Laviron) 

- [#14362](https://github.com/ocaml/ocaml/issues/14362): Add String.{drop,take,cut}_{first,last}_while 
drop_first_while: (char -> bool) -> string -> string 
(Daniel Bünzli, review by Nicolás Ojeda Bär and David Allsopp) 

- [#13916](https://github.com/ocaml/ocaml/issues/13916): Add Option.product and Option.Syntax. 
(Nicolás Ojeda Bär, review by Daniel Bünzli, Gabriel Scherer and David 
Allsopp) 

- [#13995](https://github.com/ocaml/ocaml/issues/13995): Option.blend: ('a -> 'a -> 'a) -> 'a option -> 'a option -> 'a option 
(Kate Deplaix, review by Daniel Bünzli, Gabriel Scherer, 
Nicolás Ojeda Bär, Florian Angeletti and Josh Berdine) 

- [#13920](https://github.com/ocaml/ocaml/issues/13920): add Option.{for_all, exists} 
(Gabriel Scherer, review by Kate Deplaix, Nicolás Ojeda Bär, Richard Eisenberg 
and Jeremy Yallop) 

- [#14185](https://github.com/ocaml/ocaml/issues/14185): List.split_map: ('a -> 'b * 'c) -> 'a list -> 'b list * 'c list 
(Jeremy Yallop, review by Daniel Bünzli, Nicolás Ojeda Bär and Damien Doligez) 

- [#14043](https://github.com/ocaml/ocaml/issues/14043), [#14393](https://github.com/ocaml/ocaml/issues/14393): Lazy.Mutexed: simple mutex-protected lazy thunks, 
that may block the entire domain/thread on initialization races. 
(Gabriel Scherer, suggestion by Kate Deplaix and Pierre Chambart, 
review by KC Sivaramakrishnan, Florian Angeletti, Kate Deplaix 
and Daniel Bünzli) 

- [#14118](https://github.com/ocaml/ocaml/issues/14118): Add {Set,Map}.S.is_singleton 
(Kate Deplaix, review by Daniel Bünzli, Vincent Laviron, Nicolás Ojeda Bär 
and Stephen Dolan) 

- [#14060](https://github.com/ocaml/ocaml/issues/14060): Add Hashtbl.find_and_replace and Hashtbl.find_and_remove. 
find_and_replace: ('k, 'a) Hashtbl.t -> 'k -> 'a -> 'a option 
find_and_remove: ('k, 'a) Hashtbl.t -> 'k -> 'a option 
(Sacha-Élie Ayoun, review by Nicolás Ojeda Bär and Gabriel Scherer) 

- [#14227](https://github.com/ocaml/ocaml/issues/14227): Add List.filter_mapi. 
(Émile Trotignon, review by Nicolás Ojeda Bär, Jan Midtgaard and 
Damien Doligez) 

- [#14432](https://github.com/ocaml/ocaml/issues/14432): Add floor division, ceil division, Euclidean division and remainder 
to the Int, Int32, Int64 and Nativeint modules: `fdiv`, `cdiv`, `ediv`. 
(Xavier Leroy, review by Ali Caglayan, Nicolás Ojeda Bär, Gabriel Scherer) 

- [#14433](https://github.com/ocaml/ocaml/issues/14433): Add bit-counting functions `leading_zeros`, `leading_sign_bits`, 
`trailing_zeros`, `bit_count`, `unsigned_bitsize`, `signed_bitsize` 
to Int, Int32, Int64, and Nativeint 
(Xavier Leroy, review by Ali Caglayan and David Allsopp) 


- [#10177](https://github.com/ocaml/ocaml/issues/10177): Seq.(delay : (unit -> 'a t) -> 'a t) 
(Gabriel Scherer, review by Jeremy Yallop and François Pottier) 

- [#13343](https://github.com/ocaml/ocaml/issues/13343): Add Array.stable_sort_sub 
(François Pottier, review by Gabriel Scherer, Corentin Leruth and Nicolás 
Ojeda Bär) 

- [#14363](https://github.com/ocaml/ocaml/issues/14363): Preserve the backtrace at exceptional domain termination. Domain.join 
on an exceptionally terminated domain re-raises the exception with the 
backtrace. 
(KC Sivaramakrishnan, report by Nathan Taylor, review by Gabriel Scherer, 
David Allsopp) 

- [#13728](https://github.com/ocaml/ocaml/issues/13728): Add Sys.runtime_executable containing the full path (if available) to 
the currently executing runtime. 
(David Allsopp, review by Nicolás Ojeda Bär and Daniel Bünzli) 

- [#14086](https://github.com/ocaml/ocaml/issues/14086): Add Domain.count. 
(Nicolás Ojeda Bär, review by David Allsopp, Gabriel Scherer, Daniel Bünzli 
and KC Sivaramakrishnan) 

- [#12877](https://github.com/ocaml/ocaml/issues/12877): Dynarray.rev_iter, Dynarray.rev_iteri 
(Gabriel Scherer, review by Léo Andrès, Jeremy Yallop and Nicolás Ojeda Bär) 

- [#14084](https://github.com/ocaml/ocaml/issues/14084): Future-proof Dynarray implementation against a smarter compiler 
(Basile Clément, review by Gabriel Scherer) 

### Tools: 

- [#13728](https://github.com/ocaml/ocaml/issues/13728), [#14014](https://github.com/ocaml/ocaml/issues/14014), [#14243](https://github.com/ocaml/ocaml/issues/14243), [#14244](https://github.com/ocaml/ocaml/issues/14244), [#14245](https://github.com/ocaml/ocaml/issues/14245) : The compiler is now relocatable: it 
can be copied/moved to a different directory and everything still 
works. 
(David Allsopp, review by Nicolás Ojeda Bär, Jonah Beckford, Daniel Bünzli, 
Antonin Décimo, Damien Doligez, Hugo Heuzard, Samuel Hym, 
and Vincent Laviron) 


- [#14055](https://github.com/ocaml/ocaml/issues/14055): Invert BUILD_PATH_PREFIX_MAP in directories loaded at startup 
by the debugger. 
(Pierre Boutillier, review by Gabriel Scherer and Daniel Bünzli) 

* (*breaking change*) [#13638](https://github.com/ocaml/ocaml/issues/13638): ocamlmklib exits with code 4 if passed an unrecognised option, as it 
does with an unrecognised file. 
(David Allsopp, review by Antonin Décimo and Sébastien Hinderer) 

- [#13941](https://github.com/ocaml/ocaml/issues/13941), [#13961](https://github.com/ocaml/ocaml/issues/13961): Fix `ocamltest` variable handing. 
(Damien Doligez, report by Olivier Nicole, review by Gabriel Scherer) 

- [#13962](https://github.com/ocaml/ocaml/issues/13962): Little ocamltest refactors. Fix error handling in C code, 
leaking file descriptors, code style. 
(Antonin Décimo, review by Gabriel Scherer) 

- [#14059](https://github.com/ocaml/ocaml/issues/14059): Fix flaky TSan tests 
(Fabrice Buoro and Olivier Nicole, review by Gabriel Scherer) 

- [#13966](https://github.com/ocaml/ocaml/issues/13966), [#13969](https://github.com/ocaml/ocaml/issues/13969): Enable "generalized polymorphic #install_printer" 
in the debugger 
(Pierre Boutillier and Gabriel Scherer, review by Florian Angeletti) 

- [#14063](https://github.com/ocaml/ocaml/issues/14063) : Debugger fallbacks to "looking for 'module_name'.ml in the 
loadpath" when seeking source files. It improves hit rate for 
sources of installed packages. 
(Pierre Boutillier, review by Gabriel Scherer) 

- [#14032](https://github.com/ocaml/ocaml/issues/14032), [#14034](https://github.com/ocaml/ocaml/issues/14034): Update to and require FlexDLL 0.44. 
(Jan Midtgaard, Antonin Décimo, review by David Allsopp) 

- [#14239](https://github.com/ocaml/ocaml/issues/14239): Fix `#show_constructor` when printing non-GADT type parameters 
(Takafumi Saikawa, Jacques Garrigue, review by Gabriel Scherer) 

- [#14245](https://github.com/ocaml/ocaml/issues/14245): ocamlobjinfo now displays the runtime invoked by a bytecode 
executable (either from the RNTM section or by analysing the shebang lines) 
(David Allsopp, review by Damien Doligez and Samuel Hym) 

### Runtime system: 

- [#14365](https://github.com/ocaml/ocaml/issues/14365): Add an Idle phase to the GC for better performance on small 
heaps and for a smooth start at program launch and after a forced major GC. 
(Damien Doligez, review by Stephen Dolan and Nick Barnes) 

- [#13416](https://github.com/ocaml/ocaml/issues/13416): Implement concurrency primitives using WinAPI instead of 
winpthreads on Windows. 
(Antonin Décimo, review by Samuel Hym, Gabriel Scherer, Miod Vallat, 
B. Szilvasy, and Nicolás Ojeda Bär) 

- [#14367](https://github.com/ocaml/ocaml/issues/14367): Gc.Tweak mechanism to allow named GC parameters 
(Stephen Dolan and Nick Barnes, review by Gabriel Scherer, David Allsopp and 
Antonin Décimo) 

- [#13574](https://github.com/ocaml/ocaml/issues/13574), [#13594](https://github.com/ocaml/ocaml/issues/13594): Generational scanning of stack frames for ARM 64 bits, POWER, 
and RISC-V. This reduces minor GC work in the presence of deep call stacks. 
(Xavier Leroy, review by Miod Vallat, Gabriel Scherer and Olivier Nicole) 

- [#14416](https://github.com/ocaml/ocaml/issues/14416): Spawned domains will record backtraces if the parent domain has 
enabled it. 
(Nathan Taylor, review by Gabriel Scherer) 

- [#14275](https://github.com/ocaml/ocaml/issues/14275): Add function caml_c_thread_register_in_domain, which makes it 
possible to register "C threads" in another domain than 0 (which is 
what caml_c_thread_register does). The function takes a domain unique 
ID in which to register the thread. The domain must be running 
when the function is called. 
(Jack Nørskov Jørgensen, review by Gabriel Scherer, 
Guillaume Munch-Maccagnoni) 


- [#13616](https://github.com/ocaml/ocaml/issues/13616): Change free list representation in shared heap 
(Sadiq Jaffer, review by Damien Doligez) 

- [#13580](https://github.com/ocaml/ocaml/issues/13580): Introduce sweep-only phase at start of major GC cycle, 
to reduce latent-garbage delay and therefore improve GC performance. 
(Stephen Dolan and Nick Barnes, review by KC Sivaramakrishnan) 

- [#14053](https://github.com/ocaml/ocaml/issues/14053): Statmemprof: it is now possible to replace a profile in the 
current domain without stopping it in all domains. 
Added the function [Gc.Memprof.is_sampling]. 
(Guillaume Munch-Maccagnoni, review by Gabriel Scherer) 

- [#14168](https://github.com/ocaml/ocaml/issues/14168): restore the stack size statistic in `Gc.stat` and adds a new 
`live_stacks_words` field tracking the total size in words of live stacks. 
(Florian Angeletti, review by Gabriel Scherer) 

- [#14189](https://github.com/ocaml/ocaml/issues/14189): Add runtime counters EV_C_MINOR_PROMOTED_WORDS and 
EV_C_MINOR_ALLOCATED_WORDS. EV_C_MINOR_PROMOTED_WORDS reports words promoted 
by minor GC and EV_C_MINOR_ALLOCATED_WORDS reports words allocated by minor 
GC. Both have equivalent bytes counters. Also updated the documentation for 
EV_C_MINOR_PROMOTED and EV_C_MINOR_ALLOCATED to qualify scope of the values 
reported as being per-domain. 
(Tim McGilchrist, review by Nick Barnes, Sadiq Jaffer and 
Gabriel Scherer) 

* (*breaking change*) [#14243](https://github.com/ocaml/ocaml/issues/14243): Explicit relative paths in ld.conf (".", "..", "./<path...>", 
"../<path...>") are interpreted as being relative to the directory ld.conf 
was loaded from, and the default ld.conf now uses relative paths, rather than 
embedding the absolute path to the Standard Library. The brave may continue to 
put implicit paths in ld.conf. The interpretation of CAML_LD_LIBRARY_PATH is 
unaltered. Additionally, ld.conf is loaded from all of $OCAMLLIB/ld.conf, 
$CAMLLIB/ld.conf and standard_library_default/ld.conf rather than just the 
first one found. ld.conf files with CRLF line endings are now consistently 
normalised on both Windows and Unix. 
(David Allsopp, review by Jonah Beckford, Damien Doligez and Hugo Heuzard) 

- [#14244](https://github.com/ocaml/ocaml/issues/14244): Added --with-relative-libdir which allows the runtime and the 
compilers to locate the Standard Library relative to where the binaries 
themselves are installed, removing the absolute path previously embedded in 
caml_standard_library_default. Executables linked with `ocamlc -custom` now 
always attempt to load bytecode from the executable itself, rather than first 
trying `argv[0]`. 
(David Allsopp, review by Jonah Beckford, Antonin Décimo, Damien Doligez, 
Samuel Hym and Vincent Laviron) 

- [#14245](https://github.com/ocaml/ocaml/issues/14245): Introduce Runtime IDs for use in filename mangling to allow different 
configurations and different versions of the runtime system to coexist 
harmoniously on a single system. The IDs are used, along with the host 
triplet, to provide mangled names for the ocamlrun executable and its variants 
and the DLL versions of both the bytecode and native runtimes, with symlinks 
created for the original names. They are also used to mangle the names of stub 
libraries so that stub libraries compiled for a given configuration of the 
runtime will only be sought by that runtime. The behaviour is disabled by 
configuring with --disable-suffixing. 
(David Allsopp, review by Damien Doligez and Samuel Hym) 

- [#12269](https://github.com/ocaml/ocaml/issues/12269), [#12410](https://github.com/ocaml/ocaml/issues/12410), [#13063](https://github.com/ocaml/ocaml/issues/13063): Fix unsafety, deadlocks, and/or leaks should 
rare errors happen during domain creation and thread 
creation/registration. 
(Guillaume Munch-Maccagnoni, review by Gabriel Scherer, B. Szilvasy, 
Miod Vallat) 

- [#14337](https://github.com/ocaml/ocaml/issues/14337): Fix potential segfault due to the C callback mechanism dropping 
continuations without calling `caml_continuation_use`. 
(Max Slater, review by Nick Barnes and Stephen Dolan) 

- [#14461](https://github.com/ocaml/ocaml/issues/14461): Fix racy socketpair on Windows. Address-in-use errors would sometimes 
occur when concurrent threads or processes were trying to create socketpairs. 
(Jessie Grosen, review by Antonin Décimo and Nicolás Ojeda Bär) 

- [#14820](https://github.com/ocaml/ocaml/issues/14820): caml_ba_alloc must account for memory it allocated itself. 
CAML_BA_SUBARRAY (introduced in 5.2) with data=NULL would result in the 
Gc accounting for the allocation as 0 bytes, which can eventually lead 
to OOM. This condition never occurs in the compiler itself, but occurs 
in external C bindings that attempt to create a new bigarray in the 
shape of an existing one. For backwards compatibility ignore CAML_BA_SUBARRAY 
when data is NULL. 
(Edwin Török, review by Damien Doligez) 

### Type system: 

- [#13781](https://github.com/ocaml/ocaml/issues/13781): Set scope of internal type nodes during abbreviation expansion 
rather than recursing during unification. 
(Jacques Garrigue, review by Gabriel Scherer) 

* (*breaking change*) [#14066](https://github.com/ocaml/ocaml/issues/14066): catch invalid aliases introduced by signature constraints during 
merging rather than in subtyping: 
```ocaml 
module X = struct end module F (_:sig end) = struct end 
module type T = (sig module X0 : sig end module X1 = X0 end) 
with module X0 := F(X) 
``` 
Before, it failed with a subtyping error. Now, it fails with a proper error, 
explaining that `X1` would keep an invalid alias to `F(X)` 
(Clement Blaudeau, review by Florian Angeletti) 

* (*breaking change*) [#14100](https://github.com/ocaml/ocaml/issues/14100): Do not ignore type-constraints and module-constraints when building 
the approximated signature of recursive modules. Ignoring those constraints 
resulted in incorrect (wrong set of fields, wrong shadowing between fields) 
approximated signatures, failing to typecheck, as in: 
```ocaml 
module X0 : sig type t end 
module rec X : ((sig module A : sig end end) with module A := X0) 
and Y : sig type t = X.A.t end (* Unbound type constructor X.A.t *) 
``` 
Now, type and module constraints are properly merged during approximation , 
reusing the infrastructure for normal merging of constraints, but disabling 
any wellformedness check. 
(Clement Blaudeau and Ryan Tjoa, review by Florian Angeletti) 

- [#14327](https://github.com/ocaml/ocaml/issues/14327): Allow retyping as-patterns that contain existentials 
(completing [#14229](https://github.com/ocaml/ocaml/issues/14229)) 
(Jacques Garrigue and Takafumi Saikawa, reported by Olivier Nicole, 
review by Gabriel Scherer) 

- [#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) 

### Compiler user-interface and warnings: 

- [#14330](https://github.com/ocaml/ocaml/issues/14330): add suggestions when a signature mismatch is likely to be be caused by 
spellchecking mistakes, for instance 
``` 
module M: sig type albatross end = struct type albatros end 
``` 
(Malo Monin, Florian Angeletti, review by Gabriel Scherer) 

- [#12628](https://github.com/ocaml/ocaml/issues/12628): Improved error message for unsafe values: print out the full path for 
the value that is unsafe when they are detected during the compilation of 
recursive modules. 
(Shivam Acharya, review by Gabriel Scherer and Florian Angeletti) 


- [#14076](https://github.com/ocaml/ocaml/issues/14076), 14111: error messages, add a short explanation for mismatched 
universal variables and universal quantifications. 
(Florian Angeletti, review by Gabriel Scherer) 

- [#14126](https://github.com/ocaml/ocaml/issues/14126): Document the `-i-variance` option and `+-`, `-+` variance indicators 
in the reference manual. 
(Takafumi Saikawa, review by Florian Angeletti) 

- [#14146](https://github.com/ocaml/ocaml/issues/14146): add an error message for external declaration with 
a non-syntactic arity 
``` 
external fail: (int -> int as 'a) -> 'a = "%identity" 
``` 
rather than failing with an internal error. 
(Florian Angeletti, review by Gabriel Scherer) 

- [#14147](https://github.com/ocaml/ocaml/issues/14147): print row types in error messages when they are a type constructor, 
e.g. `< foo : int; .. as $0>` when $0 is introduced by a GADT constructor 
(Stefan Muenzel, review by Jacques Garrigue and Florian Angeletti) 

- [#14190](https://github.com/ocaml/ocaml/issues/14190): `ocaml -e` now also processes `-init` (previously it was ignored). 
(Emile Trotignon, review by David Allsopp and @ygrek) 

- [#14225](https://github.com/ocaml/ocaml/issues/14225): do not raise unused-constructor warning on private 
constructor in type implementations, for example 
`type safe = private Safe`, which are typically used to 
create new fresh/generative types (here `safe`) to be used 
as GADT indices. 
(Gabriel Scherer, review by Nicolás Ojeda Bär and Florian Angeletti, 
report by Kate Deplaix) 

- [#14244](https://github.com/ocaml/ocaml/issues/14244): Add -set-runtime-default option to the compiler, allowing the default 
value of the Standard Library location used by the runtime to be overridden. 
(Antonin Décimo, review by David Allsopp, Jonah Beckford, Damien Doligez and 
Samuel Hym) 

- [#14245](https://github.com/ocaml/ocaml/issues/14245): New option -launch-method for ocamlc allows the method used by a 
tendered bytecode executable to locate the interpreter to be given explicitly. 
In particular, it makes it easier to specify the use of the executable 
launcher on Unix. New option -runtime-search extends the bytecode executable 
header to be able to search for the runtime interpreter in the directory 
containing the executable and in PATH rather than relying on a single 
hard-coded path. 
(David Allsopp, review by Damien Doligez and Samuel Hym) 

- [#14315](https://github.com/ocaml/ocaml/issues/14315): enable -i-variance also for classes and extension constructors, 
and add description of -i-variance in manpages and the manual 
(Takafumi Saikawa, review by Florian Angeletti and Jacques Garrigue) 

- [#14373](https://github.com/ocaml/ocaml/issues/14373): remove the OCAML_BINANNOT_WITHENV environment variable, and 
always strip typing environment in cmt files 
(Florian Angeletti, review by David Allsopp) 

### Other libraries: 

- [#13700](https://github.com/ocaml/ocaml/issues/13700), [#14454](https://github.com/ocaml/ocaml/issues/14454), [#14715](https://github.com/ocaml/ocaml/issues/14715): Use POSIX thread-safe getgrnam_r, getgrgid_r, 
getpwnam_r, getpwuid_r, gmtime_r, localtime_r, getlogin_r, and fix mktime 
error checking. 
(Antonin Décimo, review by Florian Angeletti, David Allsopp, Stefan Muenzel, 
Gabriel Scherer, and Miod Vallat) 

- [#14406](https://github.com/ocaml/ocaml/issues/14406): Better handling of address length for unix sockets, improving Haiku 
compatibility. 
(Sylvain Kerjean, review by Antonin Décimo and Nicolás Ojeda Bär) 

* (*breaking change*) [#14046](https://github.com/ocaml/ocaml/issues/14046): On Windows, `Unix.kill pid Sys.sigkill` causes the receiving process 
to exit with code ERROR_PROCESS_ABORTED (1067) instead of 0. 
(Nicolás Ojeda Bär, review by Miod Vallat, Antonin Décimo and David Allsopp) 

- [#14020](https://github.com/ocaml/ocaml/issues/14020): Add Unix.unsetenv. 
(Nicolás Ojeda Bär, review by Antonin Décimo and David Allsopp) 

- [#13447](https://github.com/ocaml/ocaml/issues/13447): Symmetrize shared `Sys` and `Unix` functions. Apply fixes 
of [#12072](https://github.com/ocaml/ocaml/issues/12072), [#12184](https://github.com/ocaml/ocaml/issues/12184), [#12320](https://github.com/ocaml/ocaml/issues/12320), and [#13166](https://github.com/ocaml/ocaml/issues/13166), from `Sys.rename` to 
`Unix.rename`. Make `caml_sys_close` raise on error, allowing 
`Filename.temp_file` retries if close fails. Flush buffers when 
calling `caml_sys_system_command` on Windows. Error with EINVAL 
instead of ENOENT if the command string is not a valid C string. 
(Antonin Décimo, review by Gabriel Scherer and Nicolás Ojeda Bär) 

- [#14310](https://github.com/ocaml/ocaml/issues/14310): Deprecate union sock_addr_union for struct sockaddr_storage 
and socklen_param_type for socklen_t. 
(Antonin Décimo, review by Nicolás Ojeda Bär, David Allsopp and Samuel Hym) 

- [#14391](https://github.com/ocaml/ocaml/issues/14391): unload native dynlinked objects when an error occurs and it is safe to 
do so. (Fixes [#14323](https://github.com/ocaml/ocaml/issues/14323)) 
(Nicolás Ojeda Bär, review by Vincent Laviron) 

### Code generation and optimizations: 

- [#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) 

### Manual and documentation: 

- [#14684](https://github.com/ocaml/ocaml/issues/14684), [#14782](https://github.com/ocaml/ocaml/issues/14782), [#14838](https://github.com/ocaml/ocaml/issues/14838): Improve ocamlc's and ocamlopt's manual pages and fix 
small issues in the manual 
(Samuel Hym, review by Florian Angeletti, Antonin Décimo, Gabriel Scherer and 
Nicolás Ojeda Bär) 

- [#14397](https://github.com/ocaml/ocaml/issues/14397): Improve documentation of type-directed disambiguation of array 
literals 
(Alicia Michael, review by Olivier Nicole and Florian Angeletti) 

- [#14293](https://github.com/ocaml/ocaml/issues/14293): Improve documentation of Runtime_events.Timestamp 
(Raphaël Proust, review by Gabriel Scherer) 

- [#13747](https://github.com/ocaml/ocaml/issues/13747): Document support for native debugging with GDB and LLDB. 
(Tim McGilchrist, review by Daniel Bünzli, Samuel Hym, Olivier Nicole 
and Antonin Décimo) 

* (*breaking change*) [#13975](https://github.com/ocaml/ocaml/issues/13975): documented the `[@remove_aliases]` built-in attribute for signatures 
(introduced by [#1652](https://github.com/ocaml/ocaml/issues/1652) in 2018). Small refactor of the code that fetches the 
attribute. 
(Clement Blaudeau, review by Gabriel Scherer) 

- [#14002](https://github.com/ocaml/ocaml/issues/14002): Add anchors to items and headings of the web version of the API 
documentation for easier linking. 
(Nicolás Ojeda Bär, report by Louis Roché, review by Gabriel Scherer and 
Florian Angeletti) 

- [#14023](https://github.com/ocaml/ocaml/issues/14023): Add documentation for the [row_more] function. 
(Richard Eisenberg, review by Jacques Garrigue) 

- [#14038](https://github.com/ocaml/ocaml/issues/14038): Fall back immediately to user-agent-defined fonts when web fonts 
fail to load. 
(toastal) 

- [#14048](https://github.com/ocaml/ocaml/issues/14048): document modular explicits 
(Gabriel Scherer, review by Samuel Vivien, Ali Caglayan, 
Didier Remy and François Pottier) 

- [#13994](https://github.com/ocaml/ocaml/issues/13994): document external types 
(Gabriel Scherer, review by Jan Midtgaard, Jacques Garrigue 
and Florian Angeletti) 

- [#14077](https://github.com/ocaml/ocaml/issues/14077): Add missing `item-attribute` rule for `let-binding`s in documentation 
for attributes. 
(Shon Feder) 

- [#14228](https://github.com/ocaml/ocaml/issues/14228): Trim leading spaces from first lines of LaTeX `ocamldoccode` 
environments. 
(Yukai Chou, review by Nicolás Ojeda Bär) 

- [#14248](https://github.com/ocaml/ocaml/issues/14248): Added documentation about the way `Domain.join` triggers a 
`Thread.join` on the domain's systhreads. 
(Raphaël Proust, review by Gabriel Scherer) 

- [#14392](https://github.com/ocaml/ocaml/issues/14392): Fix AsciiDoc files, add more markup, xrefs, documentation. 
(Antonin Décimo, review by Gabriel Scherer and David Allsopp) 

- [#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) 

### Internal/compiler-libs changes: 

- [#13913](https://github.com/ocaml/ocaml/issues/13913): Use Blake128 as the hash function for the compiler's CRCs 
(Vincent Laviron, review by Xavier Leroy and Gabriel Scherer) 

- [#13911](https://github.com/ocaml/ocaml/issues/13911), [#14117](https://github.com/ocaml/ocaml/issues/14117), [#14127](https://github.com/ocaml/ocaml/issues/14127): Refactor the merging of signature constraints, by 
splitting the monolithic merge function into separate, specialized functions 
(for merging types, modules and module types) - sharing only the recursive 
part for handling deep constraints. 
(Clement Blaudeau, review by Florian Angeletti and Samuel Vivien, fix by Ryan 
Tjoa) 

- [#14120](https://github.com/ocaml/ocaml/issues/14120), [#14474](https://github.com/ocaml/ocaml/issues/14474), [#14476](https://github.com/ocaml/ocaml/issues/14476): Associate Uids to items that don't have a concrete 
definition; improves Merlin's renaming for functors. 
(Ulysse Gérard, review by Florian Angeletti and Gabriel Scherer) 


- [#13839](https://github.com/ocaml/ocaml/issues/13839), [#14008](https://github.com/ocaml/ocaml/issues/14008): Reimplement `let open`, `let module` and `let exception` in 
terms of a single construct. 
(Nicolás Ojeda Bär, review by Gabriel Scherer, Samuel Vivien, Ulysse Gérard 
and Vincent Laviron, temporary regression reported by Antonio Monteiro) 

- [#13980](https://github.com/ocaml/ocaml/issues/13980) Refactor `type-approx` and improve some errors' locations. 
(Leo White, Ulysse Gérard, review by Samuel Vivien and Florian Angeletti) 

- [#14024](https://github.com/ocaml/ocaml/issues/14024): Fix unterminated-string-initialization warnings from the C compiler. 
(Antonin Décimo, review by David Allsopp and Miod Vallat) 

- [#14094](https://github.com/ocaml/ocaml/issues/14094): toplevel, simplify check on installed printer types 
(Florian Angeletti, review by Gabriel Scherer) 

- [#13656](https://github.com/ocaml/ocaml/issues/13656), [#14114](https://github.com/ocaml/ocaml/issues/14114), [#14308](https://github.com/ocaml/ocaml/issues/14308): Use C99 stdint.h/inttypes.h fixed-width 
integer types and macros to define OCaml integers. 
(Antonin Décimo, review by Nick Barnes and David Allsopp) 

- [#14148](https://github.com/ocaml/ocaml/issues/14148): Remove an unused field from package_type in typedtree 
(Samuel Vivien, review by Gabriel Scherer) 

- [#14141](https://github.com/ocaml/ocaml/issues/14141): Rename cstrs to constraints when it refers to constraints to avoid 
confusing it with constructors. 
(Stefan Muenzel, review by Nicolás Ojeda Bär) 

- [#14149](https://github.com/ocaml/ocaml/issues/14149): Distinguish `(module M : S)` from `(module M) : (module S)` in 
patterns. 
(Samuel Vivien, review by Gabriel Scherer) 

- [#14161](https://github.com/ocaml/ocaml/issues/14161): refactor the STW-participants machinery to add an intermediate 
category of 'parked' domain structures. 
(Gabriel Scherer, review by Sivaramakrishnan) 

- [#14198](https://github.com/ocaml/ocaml/issues/14198) Constraints on module unpacking are not ghost 
(Thomas Refis, review by Nicolás Ojeda Bär) 

- [#14243](https://github.com/ocaml/ocaml/issues/14243): ocamlc now uses the same code as the runtime to parse ld.conf (via a 
C primitive), eliminating some highly obscure corner cases. 
(David Allsopp, review by Jonah Beckford, Damien Doligez and Hugo Heuzard) 

- [#14260](https://github.com/ocaml/ocaml/issues/14260): Refactor Lambda.structured_constant to avoid duplicate 
representations for string constants 
(Vincent Laviron, review by Nicolás Ojeda Bär and Gabriel Scherer) 

- [#14297](https://github.com/ocaml/ocaml/issues/14297), [#14299](https://github.com/ocaml/ocaml/issues/14299): Avoid iterating on hash tables to produce types or terms 
(Vincent Laviron, review by Nicolás Ojeda Bär and Gabriel Scherer) 

* (*breaking change*) [#14322](https://github.com/ocaml/ocaml/issues/14322): Remove leftover hacks for handling pattern constraints 
As a side effect, `let rec (_ as x) = ...` is now always rejected instead of 
being treated as equivalent to `let rec x = ...` 
(Vincent Laviron, review by Alistair O'Brien and Florian Angeletti) 

- [#14331](https://github.com/ocaml/ocaml/issues/14331): Enforce current_level <= generic_level, and explain create_scope 
(Jacques Garrigue and Takafumi Saikawa, review by Gabriel Scherer) 

* (*breaking change*) [#14388](https://github.com/ocaml/ocaml/issues/14388): Remove support for `let rec (module M : S) = e1 in e2`. 
(Alistair O'Brien, review by Vincent Laviron and Gabriel Scherer) 

- [#14422](https://github.com/ocaml/ocaml/issues/14422): Refactoring an `if match e with p1 -> true | p2 -> false then ...` 
into a match in typetexp. 
(Samuel Vivien, review by Gabriel Scherer) 

- [#13224](https://github.com/ocaml/ocaml/issues/13224): Clarify barriers and spin macros with delayed expansion. 
(Antonin Décimo, review by David Allsopp and Gabriel Scherer) 

- [#14435](https://github.com/ocaml/ocaml/issues/14435), [#14455](https://github.com/ocaml/ocaml/issues/14455), [#14550](https://github.com/ocaml/ocaml/issues/14550): Add the not-root builtin ocamltest action. This 
allows to skip tests that fail if the current user is root (superuser). 
(Kate Deplaix, review by Gabriel Scherer, Nicolás Ojeda Bär, and 
Antonin Décimo) 

- [#14457](https://github.com/ocaml/ocaml/issues/14457): Handle qualified `M.{ x }` patterns in untypeast 
(Basile Clément, review by Florian Angeletti) 

### Build system: 

- [#13705](https://github.com/ocaml/ocaml/issues/13705), [#14444](https://github.com/ocaml/ocaml/issues/14444): Cache test results of custom Autoconf tests from aclocal.m4. 
(Antonin Décimo, review by David Allsopp and Miod Vallat) 

- [#13810](https://github.com/ocaml/ocaml/issues/13810): Support build of cross compilers to native freestanding targets 
(Samuel Hym, review by Antonin Décimo and Romain Calascibetta) 

- [#14243](https://github.com/ocaml/ocaml/issues/14243): New configure option --with-additional-stublibsdir allows an 
additional directory to be added to the start of ld.conf. Additionally, the 
stublibs subdirectory is no longer created, nor added to ld.conf, when 
building OCaml with --disable-shared. 
(David Allsopp, review by Jonah Beckford, Damien Doligez and Hugo Heuzard) 

- [#14244](https://github.com/ocaml/ocaml/issues/14244): When targeting native Windows on Cygwin or MSYS2, preserve 
backslashes in the supplied `--prefix` (in particular, backslashes instead of 
slashes will then be displayed by `ocamlopt -config-var standard_library`). 
If the supplied prefix contains a slash, then it is normalised, as 
previously. 
(David Allsopp, review by Jonah Beckford, Antonin Décimo, Damien Doligez and 
Samuel Hym) 

- [#14245](https://github.com/ocaml/ocaml/issues/14245): New --enable-runtime-search configure option controls the 
-runtime-search option used to build the bytecode binaries in the compiler 
distribution. --enable-runtime-search-target controls the default value of 
-runtime-search used for bytecode executables produced by the compiler. 
(David Allsopp, review by Damien Doligez and Samuel Hym) 

- [#14484](https://github.com/ocaml/ocaml/issues/14484): Set `_WIN32_WINNT` to require Windows 8/Server 2012 Windows header SDK 
support. 
(Antonin Décimo, review by David Allsopp) 

### Bug fixes: 

- [#14123](https://github.com/ocaml/ocaml/issues/14123): Fix integer-overflow problems in heap compaction. 
(Nick Barnes, review by Antonin Décimo). 

- [#14035](https://github.com/ocaml/ocaml/issues/14035): Fix the alignment of _Atomic long long unsigned int fields 
before GCC 11.1 on i686. Silence GCC note on newer versions. 
(Antonin Décimo, review by Sadiq Jaffer) 

- [#14010](https://github.com/ocaml/ocaml/issues/14010): Fix miscompilation / liveness errors for string operations 
(Mark Shinwell, Xavier Clerc, review by Xavier Leroy and Gabriel Scherer) 

- [#14036](https://github.com/ocaml/ocaml/issues/14036): Fix nontermination of cycle printing in recursive modules with 
`-short-paths`. Add error message for types considered abstract while 
checking recursive modules. 
(Brandon Stride, review by Florian Angeletti) 

- [#14065](https://github.com/ocaml/ocaml/issues/14065): Fix function signature mismatch of `__tsan_func_exit` with GCC 15. 
Check in the configure step if the TSan provided internal builtins are the 
same as what we expect, introduce `caml_tsan_*` wrappers for the `__tsan_*` 
functions we use. 
(Hari Hara Naveen S, report by Hari Hara Naveen S, 
review by Gabriel Scherer, Antonin Décimo, Olivier Nicole) 

- [#14071](https://github.com/ocaml/ocaml/issues/14071): Fix exception name in Dynlink.Error printer. 
(Etienne Millon, review by Nicolás Ojeda Bär) 

- [#13853](https://github.com/ocaml/ocaml/issues/13853): Format breaks some line too early when there 
is a break hint at the end. 
(Florian Angeletti, review by Gabriel Scherer) 

- [#10570](https://github.com/ocaml/ocaml/issues/10570): Fix handling of caml_sys_argv when exposed directly as an 
external 
(Keryan Didier, review by Vincent Laviron and Gabriel Scherer) 

- [#14155](https://github.com/ocaml/ocaml/issues/14155): Audit unexecuted phrases in compiler expect tests and 
fix all occurrences 
(Stefan Muenzel, review by Gabriel Scherer) 

- [#14163](https://github.com/ocaml/ocaml/issues/14163), [#14176](https://github.com/ocaml/ocaml/issues/14176): add a filename location to the deprecation alert for implicit 
uses of libraries bundled with the compiler (unix,re,threads,dynlink) 
(Florian Angeletti, report by Ali Caglayan, review by Gabriel Scherer) 

- [#14210](https://github.com/ocaml/ocaml/issues/14210): fix TSan-reported data race in weak pointers runtime 
(Gabriel Scherer and Damien Doligez, report by Olivier Nicole, 
review by KC Sivaramakrishnan) 

- [#14213](https://github.com/ocaml/ocaml/issues/14213): Fix shadow-stack-related crashes with TSan 
(Olivier Nicole, report by Nathan Taylor, review by Gabriel Scherer and 
Stefan Muenzel) 

- [#13658](https://github.com/ocaml/ocaml/issues/13658), [#14181](https://github.com/ocaml/ocaml/issues/14181): Fix handling of recursive function types that can result 
in an unbounded number of labeled or optional arguments. 
(Stefan Muenzel, report by Samuel Vivien, review by Florian Angeletti) 

- [#14255](https://github.com/ocaml/ocaml/issues/14255): Fix TSan bug with C calls that take many arguments 
(Olivier Nicole and Miod Vallat, report by Nathan Taylor, review by Gabriel 
Scherer) 

- [#14230](https://github.com/ocaml/ocaml/issues/14230) : ocamltest fails to link test program with -custom in some cases 
(Damien Doligez, review by David Allsopp) 

- [#14279](https://github.com/ocaml/ocaml/issues/14279): -dsource, preserve (mod) and other escaped infix keyword operators in 
the printed source wherever possible. 
(Florian Angeletti, review by Gabriel Scherer) 

- [#14300](https://github.com/ocaml/ocaml/issues/14300), [#14304](https://github.com/ocaml/ocaml/issues/14304): fix a race between memprof and the minor GC, detected by TSan 
(Gabriel Scherer, review by Stephen Dolan and Nick Barnes, 
report by Olivier Nicole) 

- [#14332](https://github.com/ocaml/ocaml/issues/14332): Fix missing TSan instrumentation in subexpressions 
(Vincent Laviron, review by Gabriel Scherer and Olivier Nicole) 

- [#14370](https://github.com/ocaml/ocaml/issues/14370), [#14429](https://github.com/ocaml/ocaml/issues/14429): Fix headers for C++ inclusion. 
(Antonin Décimo, review by Gabriel Scherer) 

- [#14417](https://github.com/ocaml/ocaml/issues/14417): Fix issue with nested packs on macOS. 
(Vincent Laviron, report by Kate Deplaix, review by Gabriel Scherer) 

- [#14423](https://github.com/ocaml/ocaml/issues/14423): Fix detection of SetThreadDescription on 32-bit builds, meaning that 
Thread.set_current_thread_name now works on 32-bit MSVC and uses the correct 
mechanism on 32-bit mingw-w64. 
(David Allsopp, review by Antonin Décimo) 

- [#14431](https://github.com/ocaml/ocaml/issues/14431): Enable native backend for DragonFly BSD. This builds ocamlopt on 
DragonFly. 
(Michael Neumann, review by Gabriel Scherer and Kate Deplaix) 

- [#14495](https://github.com/ocaml/ocaml/issues/14495): Fix infix-tag bug in the minor collector which could cause SEGVs 
in multi-domain programs. 
(Nick Barnes, review by Gabriel Scherer) 

- [#14519](https://github.com/ocaml/ocaml/issues/14519): Fix segfault when using `Runtime_events` under certain 
circumstances due to bad error checking when calling `mmap()`. 
(Mark Elvers, review by Nicolás Ojeda Bär) 

- private, CVE-2026-28364, OSEC-2026-01: robustify intern.c 
(Xavier Leroy and Nicolás Ojeda Bär, review by Olivier Nicole, Mindy Preston, 
Edwin Török, and Gabriel Scherer) 

- [#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) 

- [#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) 

- [#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) 

- [#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) 

- [#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) 

- [#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) 

- [#14667](https://github.com/ocaml/ocaml/issues/14667): enable application related warnings for module-dependent functions 
(Florian Angeletti, review by Gabriel Scherer) 

- [#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) 

- [#14349](https://github.com/ocaml/ocaml/issues/14349), [#14718](https://github.com/ocaml/ocaml/issues/14718), [#14722](https://github.com/ocaml/ocaml/issues/14722): runtime, fix in the orphaning of ephemerons 
(Gabriel Scherer, review by Olivier Nicole and Damien Doligez, 
report by Jan Midtgaard) 

- [#14702](https://github.com/ocaml/ocaml/issues/14702): Fix hidden directory files leaking into the visible load path table. 
When a hidden directory contained a file whose basename was already present, 
the file could be incorrectly added to the visible table. 
(Hugo Heuzard, 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) 

- [#14760](https://github.com/ocaml/ocaml/issues/14760), [#14802](https://github.com/ocaml/ocaml/issues/14802), [#14846](https://github.com/ocaml/ocaml/issues/14846): Correct the detection of argument defaults in 
configure, fixing an incorrect error message when installing OCaml through 
opam on OpenSUSE with the site-config package installed. 
(David Allsopp, report and review by Edwin Török) 

- [#14797](https://github.com/ocaml/ocaml/issues/14797): avoid dropping attributes attached to package types when pretty 
printing in surface syntax. 
(Chet Murthy, review by Nicolás Ojeda Bär) 

- [#14853](https://github.com/ocaml/ocaml/issues/14853), CVE-2026-41083, OSEC-2026-05: fix quoting of filenames 
passed to Filename.quote_command on Windows. 
(David Allsopp, report by Andrew Nesbitt, review by Florian Angeletti)