Hello

Here is the latest OCaml Weekly News, for the week of February 04 to 11,
2020.

Table of Contents
─────────────────

OCaml 4.10.0, first release candidate
Luv — cross-platform concurrent I/O: a binding to libuv
Musings on extended pattern-matching syntaxes
Old CWN


OCaml 4.10.0, first release candidate
═════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ocaml-4-10-0-first-release-candidate/5137/1>


octachron announced
───────────────────

  The release of OCaml version 4.10.0 is imminent. We have created a
  release candidate that you can test.

  The source code is available at these addresses:

  • <https://github.com/ocaml/ocaml/archive/4.10.0+rc1.tar.gz>
  • <https://caml.inria.fr/pub/distrib/ocaml-4.10/ocaml-4.10.0+rc1.tar.gz>

  The compiler can also be installed as an OPAM switch with one of the
  following commands.
  ┌────
  │ opam switch create ocaml-variants.4.10.0+rc1 
--repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git
  └────
  or
  ┌────
  │ opam switch create ocaml-variants.4.10.0+rc1+<VARIANT> 
--repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git
  └────
  where you replace <VARIANT> with one of these:
  • afl
  • flambda
  • fp
  • fp+flambda

  We want to know about any bugs. Please report them here:
   <https://github.com/ocaml/ocaml/issues>

  If every goes well, the full release should follow in the next two or
  three weeks.

  *OCaml 4.10.0 changes*


Language features
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#7757], [#1726]: multi-indices for extended indexing operators:
    `a.%{0;1;2}' desugars to `( .%{ ;.. } ) a [|0;1;2|]' (Florian
    Angeletti, review by Gabriel Radanne)

  • *breaking change* [#1859], [#9117]: enforce safe (immutable) strings
     by removing the -unsafe-string option by default. This can be
     overridden by a configure-time option (available since 4.04 in
     2016): –disable-force-safe-string since 4.08, -no-force-safe-since
     between 4.07 and 4.04. In the force-safe-string mode (now the
     default), the return type of the String_val macro in C stubs is
     `const char*' instead of `char*'. This change may break C FFI
     code. (Kate Deplaix)

  • [#6662], [#8908]: allow writing "module _ = E" to ignore module
    expressions (Thomas Refis, review by Gabriel Radanne)


[#7757] <https://github.com/ocaml/ocaml/issues/7757>

[#1726] <https://github.com/ocaml/ocaml/issues/1726>

[#1859] <https://github.com/ocaml/ocaml/issues/1859>

[#9117] <https://github.com/ocaml/ocaml/issues/9117>

[#6662] <https://github.com/ocaml/ocaml/issues/6662>

[#8908] <https://github.com/ocaml/ocaml/issues/8908>


Runtime system
╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8809]: Add a best-fit allocator for the major heap; still
    experimental, it should be much better than current allocation
    policies (first-fit and next-fit) for programs with large heaps,
    reducing both GC cost and memory usage. This new best-fit is not
    (yet) the default; set it explicitly with OCAMLRUNPARAM="a=2" (or
    Gc.set from the program). You may also want to increase the
    `space_overhead' parameter of the GC (a percentage, 80 by default),
    for example OCAMLRUNPARAM="o=85", for optimal speed. (Damien
    Doligez, review by Stephen Dolan, Jacques-Henri Jourdan, Xavier
    Leroy, Leo White)

  • *breaking change* [#8713], [#8940], [#9115], [#9143], [#9202],
     [#9251]: Introduce a state table in the runtime to contain the
     global variables. (The Multicore runtime will have one such state
     for each domain.)

    This changes the status of some internal variables of the OCaml
    runtime; in many cases the header file originally defining the
    internal variable provides a compatibility macro with the old name,
    but programs re-defining those variables by hand need to be fixed.

    (KC Sivaramakrishnan and Stephen Dolan, compatibility hacking by
    David Allsopp, Florian Angeletti, Kate Deplaix, Jacques Garrigue,
    Guillaume Munch-Maccagnoni and Nicolás Ojeda Bär, review by David
    Allsopp, Alain Frisch, Nicolas Ojeda Bar, Gabriel Scherer, Damien
    Doligez, and Guillaume Munch-Maccagnoni)

  • [#8993]: New C functions caml_process_pending_actions{,_exn} in
    caml/signals.h, intended for executing all pending actions inside
    long-running C functions (requested minor and major collections,
    signal handlers, finalisers, and memprof callbacks). The function
    caml_process_pending_actions_exn returns any exception arising
    during their execution, allowing resources to be cleaned-up before
    re-raising. (Guillaume Munch-Maccagnoni, review by Jacques-Henri
    Jourdan, Stephen Dolan, and Gabriel Scherer)

  • *breaking change* [#8691], [#8897], [#9027]: Allocation functions
     are now guaranteed not to trigger any OCaml callback when called
     from C. In long-running C functions, this can be replaced with
     calls to caml_process_pending_actions at safe points. Side effect
     of this change: in bytecode mode, polling for asynchronous
     callbacks is performed at every minor heap allocation, in addition
     to function calls and loops as in previous OCaml
     releases. (Jacques-Henri Jourdan, review by Stephen Dolan, Gabriel
     Scherer and Guillaume Munch-Maccagnoni)

  • *breaking change* [#9037]: caml_check_urgent_gc is now guaranteed
     not to trigger any finaliser. In long-running C functions, this can
     be replaced with calls to caml_process_pending_actions at safe
     points. (Guillaume Munch-Maccagnoni, review by Jacques-Henri
     Jourdan and Stephen Dolan)

  • [#8619]: Ensure Gc.minor_words remains accurate after a GC. (Stephen
    Dolan, Xavier Leroy and David Allsopp, review by Xavier Leroy and
    Gabriel Scherer)

  • [#8667]: Limit GC credit to 1.0 (Leo White, review by Damien
    Doligez)

  • [#8670]: Fix stack overflow detection with systhreads (Stephen
    Dolan, review by Xavier Leroy, Anil Madhavapeddy, Gabriel Scherer,
    Frédéric Bour and Guillaume Munch-Maccagnoni)

  • *breaking change* [#8711]: The major GC hooks are no longer allowed
     to interact with the OCaml heap. (Jacques-Henri Jourdan, review by
     Damien Doligez)

  • [#8630]: Use abort() instead of exit(2) in caml_fatal_error, and add
    the new hook caml_fatal_error_hook. (Jacques-Henri Jourdan, review
    by Xavier Leroy)

  • [#8641]: Better call stacks when a C call is involved in byte code
    mode (Jacques-Henri Jourdan, review by Xavier Leroy)

  • [#8634], [#8668], [#8684], [#9103] (originally [#847]): Statistical
    memory profiling. In OCaml 4.10, support for allocations in the
    minor heap in native mode is not available, and callbacks for
    promotions and deallocations are not available. Hence, there is not
    any public API for this feature yet. (Jacques-Henri Jourdan, review
    by Stephen Dolan, Gabriel Scherer and Damien Doligez)

  • [#9268], [#9271]: Fix bytecode backtrace generation with large
    integers present. (Stephen Dolan and Mark Shinwell, review by
    Gabriel Scherer and Jacques-Henri Jourdan)


[#8809] <https://github.com/ocaml/ocaml/issues/8809>

[#8713] <https://github.com/ocaml/ocaml/issues/8713>

[#8940] <https://github.com/ocaml/ocaml/issues/8940>

[#9115] <https://github.com/ocaml/ocaml/issues/9115>

[#9143] <https://github.com/ocaml/ocaml/issues/9143>

[#9202] <https://github.com/ocaml/ocaml/issues/9202>

[#9251] <https://github.com/ocaml/ocaml/issues/9251>

[#8993] <https://github.com/ocaml/ocaml/issues/8993>

[#8691] <https://github.com/ocaml/ocaml/issues/8691>

[#8897] <https://github.com/ocaml/ocaml/issues/8897>

[#9027] <https://github.com/ocaml/ocaml/issues/9027>

[#9037] <https://github.com/ocaml/ocaml/issues/9037>

[#8619] <https://github.com/ocaml/ocaml/issues/8619>

[#8667] <https://github.com/ocaml/ocaml/issues/8667>

[#8670] <https://github.com/ocaml/ocaml/issues/8670>

[#8711] <https://github.com/ocaml/ocaml/issues/8711>

[#8630] <https://github.com/ocaml/ocaml/issues/8630>

[#8641] <https://github.com/ocaml/ocaml/issues/8641>

[#8634] <https://github.com/ocaml/ocaml/issues/8634>

[#8668] <https://github.com/ocaml/ocaml/issues/8668>

[#8684] <https://github.com/ocaml/ocaml/issues/8684>

[#9103] <https://github.com/ocaml/ocaml/issues/9103>

[#847] <https://github.com/ocaml/ocaml/issues/847>

[#9268] <https://github.com/ocaml/ocaml/issues/9268>

[#9271] <https://github.com/ocaml/ocaml/issues/9271>


Standard library
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8760]: List.concat_map : ('a -> 'b list) -> 'a list -> 'b list
    (Gabriel Scherer, review by Daniel Bünzli and Thomas Refis)

  • [#8832]: List.find_map : ('a -> 'b option) -> 'a list -> 'b option
    (Gabriel Scherer, review by Jeremy Yallop, Nicolás Ojeda Bär and
    Daniel Bünzli)

  • [#7672], [#1492]: Add `Filename.quote_command' to produce
    properly-quoted commands for execution by Sys.command. (Xavier
    Leroy, review by David Allsopp and Damien Doligez)

  • [#8971]: Add `Filename.null', the conventional name of the "null"
    device. (Nicolás Ojeda Bär, review by Xavier Leroy and Alain Frisch)

  • [#8651]: add '%#F' modifier in printf to output OCaml float
    constants in hexadecimal (Pierre Roux, review by Gabriel Scherer and
    Xavier Leroy)

  • [#8657]: Optimization in [Array.make] when initializing with unboxed
    or young values. (Jacques-Henri Jourdan, review by Gabriel Scherer
    and Stephen Dolan)

  • [#8716]: Optimize [Array.fill] and [Hashtbl.clear] with a new
    runtime primitive (Alain Frisch, review by David Allsopp, Stephen
    Dolan and Damien Doligez)

  • [#8530]: List.sort: avoid duplicate work by chop (Guillaume
    Munch-Maccagnoni, review by David Allsopp, Damien Doligez and
    Gabriel Scherer)


[#8760] <https://github.com/ocaml/ocaml/issues/8760>

[#8832] <https://github.com/ocaml/ocaml/issues/8832>

[#7672] <https://github.com/ocaml/ocaml/issues/7672>

[#1492] <https://github.com/ocaml/ocaml/issues/1492>

[#8971] <https://github.com/ocaml/ocaml/issues/8971>

[#8651] <https://github.com/ocaml/ocaml/issues/8651>

[#8657] <https://github.com/ocaml/ocaml/issues/8657>

[#8716] <https://github.com/ocaml/ocaml/issues/8716>

[#8530] <https://github.com/ocaml/ocaml/issues/8530>


Other libraries
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#1939], [#2023]: Implement Unix.truncate and Unix.ftruncate on
    Windows. (Florent Monnier and Nicolás Ojeda Bär, review by David
    Allsopp)


[#1939] <https://github.com/ocaml/ocaml/issues/1939>

[#2023] <https://github.com/ocaml/ocaml/issues/2023>


Code generation and optimizations
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8806]: Add an [@@immediate64] attribute for types that are known
    to be immediate only on 64 bit platforms (Jérémie Dimino, review by
    Vladimir Keleshev)

  • [#9028], [#9032]: Fix miscompilation by no longer assuming that
    untag_int (tag_int x) = x in Cmmgen; the compilation of `(n lsl 1) +
    1', for example, would be incorrect if evaluated with a large value
    for `n'. (Stephen Dolan, review by Vincent Laviron and Xavier Leroy)

  • [#8672]: Optimise Switch code generation on booleans. (Stephen
    Dolan, review by Pierre Chambart)

  • [#8990]: amd64: Emit 32bit registers for Iconst_int when we can
    (Xavier Clerc, Tom Kelly and Mark Shinwell, review by Xavier Leroy)

  • [#2322]: Add pseudo-instruction `Ladjust_trap_depth' to replace
    dummy Lpushtrap generated in linearize (Greta Yorsh and Vincent
    Laviron, review by Xavier Leroy)

  • [#8707]: Simplif: more regular treatment of Tupled and Curried
    functions (Gabriel Scherer, review by Leo White and Alain Frisch)

  • [#8526]: Add compile-time option -function-sections in ocamlopt to
    emit each function in a separate named text section on supported
    targets. (Greta Yorsh, review by Pierre Chambart)

  • [#2321]: Eliminate dead ICatch handlers (Greta Yorsh, review by
    Pierre Chambart and Vincent Laviron)

  • [#8919]: lift mutable lets along with immutable ones (Leo White,
    review by Pierre Chambart)

  • [#8909]: Graph coloring register allocator: the weights put on
    preference edges should not be divided by 2 in branches of
    conditional constructs, because it is not good for performance and
    because it leads to ignoring preference edges with 0 weight. (Eric
    Stavarache, review by Xavier Leroy)

  • [#9006]: int32 code generation improvements (Stephen Dolan, designed
    with Greta Yorsh, review by Xavier Clerc, Xavier Leroy and Alain
    Frisch)

  • [#9041]: amd64: Avoid stall in sqrtsd by clearing
    destination. (Stephen Dolan, with thanks to Andrew Hunter, Will
    Hasenplaugh, Spiros Eliopoulos and Brian Nigito. Review by Xavier
    Leroy)


[#8806] <https://github.com/ocaml/ocaml/issues/8806>

[#9028] <https://github.com/ocaml/ocaml/issues/9028>

[#9032] <https://github.com/ocaml/ocaml/issues/9032>

[#8672] <https://github.com/ocaml/ocaml/issues/8672>

[#8990] <https://github.com/ocaml/ocaml/issues/8990>

[#2322] <https://github.com/ocaml/ocaml/issues/2322>

[#8707] <https://github.com/ocaml/ocaml/issues/8707>

[#8526] <https://github.com/ocaml/ocaml/issues/8526>

[#2321] <https://github.com/ocaml/ocaml/issues/2321>

[#8919] <https://github.com/ocaml/ocaml/issues/8919>

[#8909] <https://github.com/ocaml/ocaml/issues/8909>

[#9006] <https://github.com/ocaml/ocaml/issues/9006>

[#9041] <https://github.com/ocaml/ocaml/issues/9041>


Manual and documentation
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8718], [#9089]: syntactic highlighting for code examples in the
    manual (Florian Angeletti, report by Anton Kochkov, review by
    Gabriel Scherer)

  • [#9101]: add links to section anchor before the section title, make
    the name of those anchor explicits. (Florian Angeletti, review by
    Daniel Bünzli, Sébastien Hinderer, and Gabriel Scherer)

  • [#9257], cautionary guidelines for using the internal runtime API
    without too much updating pain. (Florian Angeletti, review by Daniel
    Bünzli, Guillaume Munch-Maccagnoni and KC Sivaramakrishnan)

  • [#8950]: move local opens in pattern out of the extension chapter
    (Florian Angeletti, review and suggestion by Gabriel Scherer)

  • [#9088], [#9097]: fix operator character classes (Florian Angeletti,
    review by Gabriel Scherer, report by Clément Busschaert)

  • [#9169]: better documentation for the best-fit allocation policy
    (Gabriel Scherer, review by Guillaume Munch-Maccagnoni and Florian
    Angeletti)


[#8718] <https://github.com/ocaml/ocaml/issues/8718>

[#9089] <https://github.com/ocaml/ocaml/issues/9089>

[#9101] <https://github.com/ocaml/ocaml/issues/9101>

[#9257] <https://github.com/ocaml/ocaml/issues/9257>

[#8950] <https://github.com/ocaml/ocaml/issues/8950>

[#9088] <https://github.com/ocaml/ocaml/issues/9088>

[#9097] <https://github.com/ocaml/ocaml/issues/9097>

[#9169] <https://github.com/ocaml/ocaml/issues/9169>


Compiler user-interface and warnings
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8833]: Hint for (type) redefinitions in toplevel session (Florian
    Angeletti, review by Gabriel Scherer)

  • [#2127], [#9185]: Refactor lookup functions. Included observable
    changes:
    • makes the location of usage warnings and alerts for constructors
      more precise
    • don't warn about a constructor never being used to build values
      when it has been defined as private
    (Leo White, Hugo Heuzard review by Thomas Refis, Florian Angeletti)

  • [#8702], [#8777]: improved error messages for fixed row polymorphic
    variants (Florian Angeletti, report by Leo White, review by Thomas
    Refis)

  • [#8844]: Printing faulty constructors, inline records fields and
    their types during type mismatches. Also slightly changed other type
    mismatches error output. (Mekhrubon Turaev, review by Florian
    Angeletti, Leo White)

  • [#8885]: Warn about unused local modules (Thomas Refis, review by
    Alain Frisch)

  • [#8872]: Add ocamlc option "-output-complete-exe" to build a
    self-contained binary for bytecode programs, containing the runtime
    and C stubs. (Stéphane Glondu, Nicolás Ojeda Bär, review by Jérémie
    Dimino and Daniel Bünzli)

  • [#8874]: add tests for typechecking error messages and pack them
    into pretty-printing boxes. (Oxana Kostikova, review by Gabriel
    Scherer)

  • [#8891]: Warn about unused functor parameters (Thomas Refis, review
    by Gabriel Radanne)

  • [#8903]: Improve errors for first-class modules (Leo White, review
    by Jacques Garrigue)

  • [#8914]: clarify the warning on unboxable types used in external
    primitives (61) (Gabriel Scherer, review by Florian Angeletti,
    report on the Discourse forum)

  • [#9046]: disable warning 30 by default This outdated warning
    complained on label/constructor name conflicts within a
    mutually-recursive type declarations; there is now no need to
    complain thanks to type-based disambiguation. (Gabriel Scherer)


[#8833] <https://github.com/ocaml/ocaml/issues/8833>

[#2127] <https://github.com/ocaml/ocaml/issues/2127>

[#9185] <https://github.com/ocaml/ocaml/issues/9185>

[#8702] <https://github.com/ocaml/ocaml/issues/8702>

[#8777] <https://github.com/ocaml/ocaml/issues/8777>

[#8844] <https://github.com/ocaml/ocaml/issues/8844>

[#8885] <https://github.com/ocaml/ocaml/issues/8885>

[#8872] <https://github.com/ocaml/ocaml/issues/8872>

[#8874] <https://github.com/ocaml/ocaml/issues/8874>

[#8891] <https://github.com/ocaml/ocaml/issues/8891>

[#8903] <https://github.com/ocaml/ocaml/issues/8903>

[#8914] <https://github.com/ocaml/ocaml/issues/8914>

[#9046] <https://github.com/ocaml/ocaml/issues/9046>


Tools
╌╌╌╌╌

  • *breaking change* [#6792], [#8654] ocamldebug now supports programs
     using Dynlink. This changes ocamldebug messages, which may break
     compatibility with older emacs modes. (Whitequark and Jacques-Henri
     Jourdan, review by Gabriel Scherer and Xavier Clerc)

  • [#8621]: Make ocamlyacc a Windows Unicode application (David
    Allsopp, review by Nicolás Ojeda Bär)

  • *breaking change* [#8834], `ocaml': adhere to the XDG base directory
     specification to locate an `.ocamlinit' file. Reads an
     `$XDG_CONFIG_HOME/ocaml/init.ml' file before trying to lookup
     `~/.ocamlinit'. On Windows the behaviour is unchanged. (Daniel
     C. Bünzli, review by David Allsopp, Armaël Guéneau and Nicolás
     Ojeda Bär)

  • [#9113]: ocamldoc: fix the rendering of multi-line code blocks in
    the 'man' backend. (Gabriel Scherer, review by Florian Angeletti)

  • [#9127], [#9130]: ocamldoc: fix the formatting of closing brace in
    record types. (David Allsopp, report by San Vu Ngoc)

  • [#9181]: make objinfo work on Cygwin and look for the
    caml_plugin_header symbol in both the static and the dynamic symbol
    tables. (Sébastien Hinderer, review by Gabriel Scherer and David
    Allsopp)


[#6792] <https://github.com/ocaml/ocaml/issues/6792>

[#8654] <https://github.com/ocaml/ocaml/issues/8654>

[#8621] <https://github.com/ocaml/ocaml/issues/8621>

[#8834] <https://github.com/ocaml/ocaml/issues/8834>

[#9113] <https://github.com/ocaml/ocaml/issues/9113>

[#9127] <https://github.com/ocaml/ocaml/issues/9127>

[#9130] <https://github.com/ocaml/ocaml/issues/9130>

[#9181] <https://github.com/ocaml/ocaml/issues/9181>


Build system
╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8840]: use ocaml{c,opt}.opt when available to build internal tools
    On my machine this reduces parallel-build times from 3m30s to
    2m50s. (Gabriel Scherer, review by Xavier Leroy and Sébastien
    Hinderer)

  • [#8650]: ensure that "make" variables are defined before use; revise
    generation of config/util.ml to better quote special characters
    (Xavier Leroy, review by David Allsopp)

  • [#8690], [#8696]: avoid rebuilding the world when files containing
    primitives change. (Stephen Dolan, review by Gabriel Scherer,
    Sébastien Hinderer and Thomas Refis)

  • [#8835]: new configure option –disable-stdlib-manpages to disable
    building and installation of the library manpages. (David Allsopp,
    review by Florian Angeletti and Gabriel Scherer)

  • [#8837]: build manpages using ocamldoc.opt when available cuts the
    manpages build time from 14s to 4s (Gabriel Scherer, review by David
    Allsopp and Sébastien Hinderer, report by David Allsopp)

  • [#8843], [#8841]: fix use of off_t on 32-bit systems. (Stephen
    Dolan, report by Richard Jones, review by Xavier Leroy)

  • [#8947], [#9134]: fix/improve support for the BFD library (Sébastien
    Hinderer, review by Damien Doligez)

  • [#8951]: let make's default target build the compiler (Sébastien
    Hinderer, review by David Allsopp)

  • [#8995]: allow developers to specify frequently-used configure
    options in Git (ocaml.configure option) and a directory for
    host-specific, shareable config.cache files (ocaml.configure-cache
    option). See HACKING.adoc for further details. (David Allsopp,
    review by Gabriel Scherer)

  • [#9136]: Don't propagate Cygwin-style prefix from configure to
    Makefile.config on Windows ports. (David Allsopp, review by
    Sébastien Hinderer)


[#8840] <https://github.com/ocaml/ocaml/issues/8840>

[#8650] <https://github.com/ocaml/ocaml/issues/8650>

[#8690] <https://github.com/ocaml/ocaml/issues/8690>

[#8696] <https://github.com/ocaml/ocaml/issues/8696>

[#8835] <https://github.com/ocaml/ocaml/issues/8835>

[#8837] <https://github.com/ocaml/ocaml/issues/8837>

[#8843] <https://github.com/ocaml/ocaml/issues/8843>

[#8841] <https://github.com/ocaml/ocaml/issues/8841>

[#8947] <https://github.com/ocaml/ocaml/issues/8947>

[#9134] <https://github.com/ocaml/ocaml/issues/9134>

[#8951] <https://github.com/ocaml/ocaml/issues/8951>

[#8995] <https://github.com/ocaml/ocaml/issues/8995>

[#9136] <https://github.com/ocaml/ocaml/issues/9136>


Internal/compiler-libs changes
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • [#8828]: Added abstractions for variants, records, constructors,
    fields and extension constructor types mismatch. (Mekhrubon Turaev,
    review by Florian Angeletti, Leo White and Gabriel Scherer)

  • [#7927], [#8527]: Replace long tuples into records in typeclass.ml
    (Ulugbek Abdullaev, review by David Allsopp and Gabriel Scherer)

  • [#1963]: split cmmgen into generic Cmm helpers and clambda
    transformations (Vincent Laviron, review by Mark Shinwell)

  • [#1901]: Fix lexing of character literals in comments (Pieter
    Goetschalckx, review by Damien Doligez)

  • [#1932]: Allow octal escape sequences and identifiers containing
    apostrophes in ocamlyacc actions and comments. (Pieter Goetschalckx,
    review by Damien Doligez)

  • [#2288]: Move middle end code from [Asmgen] to [Clambda_middle_end]
    and [Flambda_middle_end].  Run [Un_anf] from the middle end, not
    [Cmmgen]. (Mark Shinwell, review by Pierre Chambart)

  • [#8692]: Remove Misc.may_map and similar (Leo White, review by
    Gabriel Scherer and Thomas Refis)

  • [#8677]: Use unsigned comparisons in amd64 and i386 emitter of
    Lcondbranch3. (Greta Yorsh, review by Xavier Leroy)

  • [#8766]: Parmatch: introduce a type for simplified pattern heads
    (Gabriel Scherer and Thomas Refis, review by Stephen Dolan and
    Florian Angeletti)

  • [#8774]: New implementation of Env.make_copy_of_types (Alain Frisch,
    review by Thomas Refis, Leo White and Jacques Garrigue)

  • [#7924]: Use a variant instead of an int in Bad_variance exception
    (Rian Douglas, review by Gabriel Scherer)

  • [#8890]: in -dtimings output, show time spent in C linker clearly
    (Valentin Gatien-Baron)

  • [#8910], [#8911]: minor improvements to the printing of module types
    (Gabriel Scherer, review by Florian Angeletti)

  • [#8913]: ocamltest: improve 'promote' implementation to take skipped
    lines/bytes into account (Gabriel Scherer, review by Sébastien
    Hinderer)

  • [#8908]: Use an option instead of a string for module names ("_"
    becomes None), and a dedicated type for functor parameters: "()"
    maps to "Unit" (instead of "*"). (Thomas Refis, review by Gabriel
    Radanne)

  • [#8928]: Move contains_calls and num_stack_slots from Proc to
    Mach.fundecl (Greta Yorsh, review by Florian Angeletti and Vincent
    Laviron)

  • [#8959], [#8960], [#8968], [#9023]: minor refactorings in the typing
    of patterns:
    • refactor the {let,pat}_bound_idents* functions
    • minor bugfix in type_pat
    • refactor the generic pattern-traversal functions in Typecore and
      Typedtree
    • restrict the use of Need_backtrack
    (Gabriel Scherer and Florian Angeletti, review by Thomas Refis and
    Gabriel Scherer)

  • [#9030]: clarify and document the parameter space of type_pat
    (Gabriel Scherer and Florian Angeletti and Jacques Garrigue, review
    by Florian Angeletti and Thomas Refis)

  • [#8975]: "ocamltests" files are no longer required or used by
    "ocamltest". Instead, any text file in the testsuite directory
    containing a valid "TEST" block will be automatically included in
    the testsuite. (Nicolás Ojeda Bär, review by Gabriel Scherer and
    Sébastien Hinderer)

  • [#8992]: share argument implementations between executables (Florian
    Angeletti, review by Gabriel Scherer)

  • [#9015]: fix fatal error in pprint_ast ([#8789]) (Damien Doligez,
    review by …)


[#8828] <https://github.com/ocaml/ocaml/issues/8828>

[#7927] <https://github.com/ocaml/ocaml/issues/7927>

[#8527] <https://github.com/ocaml/ocaml/issues/8527>

[#1963] <https://github.com/ocaml/ocaml/issues/1963>

[#1901] <https://github.com/ocaml/ocaml/issues/1901>

[#1932] <https://github.com/ocaml/ocaml/issues/1932>

[#2288] <https://github.com/ocaml/ocaml/issues/2288>

[#8692] <https://github.com/ocaml/ocaml/issues/8692>

[#8677] <https://github.com/ocaml/ocaml/issues/8677>

[#8766] <https://github.com/ocaml/ocaml/issues/8766>

[#8774] <https://github.com/ocaml/ocaml/issues/8774>

[#7924] <https://github.com/ocaml/ocaml/issues/7924>

[#8890] <https://github.com/ocaml/ocaml/issues/8890>

[#8910] <https://github.com/ocaml/ocaml/issues/8910>

[#8911] <https://github.com/ocaml/ocaml/issues/8911>

[#8913] <https://github.com/ocaml/ocaml/issues/8913>

[#8908] <https://github.com/ocaml/ocaml/issues/8908>

[#8928] <https://github.com/ocaml/ocaml/issues/8928>

[#8959] <https://github.com/ocaml/ocaml/issues/8959>

[#8960] <https://github.com/ocaml/ocaml/issues/8960>

[#8968] <https://github.com/ocaml/ocaml/issues/8968>

[#9023] <https://github.com/ocaml/ocaml/issues/9023>

[#9030] <https://github.com/ocaml/ocaml/issues/9030>

[#8975] <https://github.com/ocaml/ocaml/issues/8975>

[#8992] <https://github.com/ocaml/ocaml/issues/8992>

[#9015] <https://github.com/ocaml/ocaml/issues/9015>

[#8789] <https://github.com/ocaml/ocaml/issues/8789>


Bug fixes
╌╌╌╌╌╌╌╌╌

  • [#5673], [#7636]: unused type variable causes generalization error
    (Jacques Garrigue and Leo White, review by Leo White, reports by
    Jean-Louis Giavitto and Christophe Raffalli)

  • [#6922], [#8955]: Fix regression with -principal type inference for
    inherited methods, allowing to compile ocamldoc with -principal
    (Jacques Garrigue, review by Leo White)

  • [#7925], [#8611]: fix error highlighting for exceptionally long
    toplevel phrases (Kyle Miller, reported by Armaël Guéneau, review by
    Armaël Guéneau and Nicolás Ojeda Bär)

  • [#8622]: Don't generate #! headers over 127 characters. (David
    Allsopp, review by Xavier Leroy and Stephen Dolan)

  • [#8715]: minor bugfixes in CamlinternalFormat; removes the unused
    and misleading function CamlinternalFormat.string_of_formatting_gen
    (Gabriel Scherer and Florian Angeletti, review by Florian Angeletti
    and Gabriel Radanne)

  • [#8792], [#9018]: Possible (latent) bug in Ctype.normalize_type
    removed incrimined Btype.log_type, replaced by Btype.set_type
    (Jacques Garrigue, report by Alain Frisch, review by Thomas Refis)

  • [#8856], [#8860]: avoid stackoverflow when printing cyclic type
    expressions in some error submessages. (Florian Angeletti, report by
    Mekhrubon Turaev, review by Leo White)

  • [#8875]: fix missing newlines in the output from MSVC
    invocation. (Nicolás Ojeda Bär, review by Gabriel Scherer)

  • [#8921], [#8924]: Fix stack overflow with Flambda (Vincent Laviron,
    review by Pierre Chambart and Leo White, report by Aleksandr
    Kuzmenko)

  • [#8892], [#8895]: fix the definition of Is_young when CAML_INTERNALS
    is not defined. (David Allsopp, review by Xavier Leroy)

  • [#8896]: deprecate addr typedef in misc.h (David Allsopp, suggestion
    by Xavier Leroy)

  • [#8981]: Fix check for incompatible -c and -o options. (Greta Yorsh,
    review by Damien Doligez)

  • [#9019], [#9154]: Unsound exhaustivity of GADTs from incomplete
    unification Also fixes bug found by Thomas Refis in [#9012] (Jacques
    Garrigue, report and review by Leo White, Thomas Refis)

  • [#9031]: Unregister Windows stack overflow handler while shutting
    the runtime down. (Dmitry Bely, review by David Allsopp)

  • [#9051]: fix unregistered local root in win32unix/select.c (could
    result in `select' returning file_descr-like values which weren't in
    the original sets) and correct initialisation of some blocks
    allocated with caml_alloc_small. (David Allsopp, review by Xavier
    Leroy)

  • [#9073], [#9120]: fix incorrect GC ratio multiplier when allocating
    custom blocks with caml_alloc_custom_mem in runtime/custom.c (Markus
    Mottl, review by Gabriel Scherer and Damien Doligez)

  • [#9209], [#9212]: fix a development-version regression caused by
    [#2288] (Kate Deplaix and David Allsopp, review by Sébastien
    Hinderer and Gabriel Scherer )

  • [#9218], [#9269]: avoid a rare wrong module name error with "-annot"
    and inline records. (Florian Angeletti, review by Gabriel Scherer,
    report by Kate Deplaix)

  • [#9261]: Fix a soundness bug in Rec_check, new in 4.10 (from
    [#8908]) (Vincent Laviron, review by Jeremy Yallop and Gabriel
    Scherer)


[#5673] <https://github.com/ocaml/ocaml/issues/5673>

[#7636] <https://github.com/ocaml/ocaml/issues/7636>

[#6922] <https://github.com/ocaml/ocaml/issues/6922>

[#8955] <https://github.com/ocaml/ocaml/issues/8955>

[#7925] <https://github.com/ocaml/ocaml/issues/7925>

[#8611] <https://github.com/ocaml/ocaml/issues/8611>

[#8622] <https://github.com/ocaml/ocaml/issues/8622>

[#8715] <https://github.com/ocaml/ocaml/issues/8715>

[#8792] <https://github.com/ocaml/ocaml/issues/8792>

[#9018] <https://github.com/ocaml/ocaml/issues/9018>

[#8856] <https://github.com/ocaml/ocaml/issues/8856>

[#8860] <https://github.com/ocaml/ocaml/issues/8860>

[#8875] <https://github.com/ocaml/ocaml/issues/8875>

[#8921] <https://github.com/ocaml/ocaml/issues/8921>

[#8924] <https://github.com/ocaml/ocaml/issues/8924>

[#8892] <https://github.com/ocaml/ocaml/issues/8892>

[#8895] <https://github.com/ocaml/ocaml/issues/8895>

[#8896] <https://github.com/ocaml/ocaml/issues/8896>

[#8981] <https://github.com/ocaml/ocaml/issues/8981>

[#9019] <https://github.com/ocaml/ocaml/issues/9019>

[#9154] <https://github.com/ocaml/ocaml/issues/9154>

[#9012] <https://github.com/ocaml/ocaml/issues/9012>

[#9031] <https://github.com/ocaml/ocaml/issues/9031>

[#9051] <https://github.com/ocaml/ocaml/issues/9051>

[#9073] <https://github.com/ocaml/ocaml/issues/9073>

[#9120] <https://github.com/ocaml/ocaml/issues/9120>

[#9209] <https://github.com/ocaml/ocaml/issues/9209>

[#9212] <https://github.com/ocaml/ocaml/issues/9212>

[#2288] <https://github.com/ocaml/ocaml/issues/2288>

[#9218] <https://github.com/ocaml/ocaml/issues/9218>

[#9269] <https://github.com/ocaml/ocaml/issues/9269>

[#9261] <https://github.com/ocaml/ocaml/issues/9261>

[#8908] <https://github.com/ocaml/ocaml/issues/8908>


Luv — cross-platform concurrent I/O: a binding to libuv
═══════════════════════════════════════════════════════

  Archive:
  
<https://discuss.ocaml.org/t/luv-cross-platform-concurrent-i-o-a-binding-to-libuv/5145/1>


Anton Bachin announced
──────────────────────

  I am pleased to announce the first release of [**Luv**], a binding to
  [libuv]. libuv is the cross-platform C library inside Node.js that
  does I/O, wraps system calls, and drives Node's main loop.

  ┌────
  │ let () =
  │   let timer = Luv.Timer.init () |> Stdlib.Result.get_ok in
  │   ignore (Luv.Timer.start timer 1000 (fun () ->
  │     print_endline "Hello, world!"));
  │ 
  │   print_endline "Waiting...";
  │   ignore (Luv.Loop.run ())
  └────

  <https://github.com/aantron/luv>

  Luv exposes sockets, files, subprocesses, FS events, and many other OS
  APIs. Indeed, Luv is an independent alternative to the standard
  [`Unix'], and does not depend on `Unix'. The easiest way to get an
  idea of all that is available is to quickly scroll through the [list
  of modules in the API docs].

  You are invited to glance through all of Luv's documentation:

  • [Project page]
  • [User guide]
  • [API reference]
  • [Examples], which are discussed in the guide…
  • …and the [documentation of libuv]

  libuv is focused primarily on [event-driven programming], which makes
  it similar to Async or Lwt. However, it does not offer a promise data
  type — the API is written in terms of callbacks.

  libuv also supports [multithreading] and [multiprocessing]. In
  particular, libuv allows running multiple event loops in multiple
  threads, which makes it a ready candidate for use with a multicore
  runtime.

  A major advantage of libuv is that, because it is a core module of
  Node, it is [well-maintained] and supports [many platforms]. Luv
  inherits these properties.

  Luv uses [ctypes] to greatly minimize the amount of C code in the
  repo. A thorough [test suite] checks return values, I/O effects, and
  interaction with the OCaml garbage collector and threading
  runtime. Luv vendors libuv to avoid version conflicts, and, when you
  install Luv, it automatically builds its internal libuv.

  One of the main goals of Luv is to be easy to integrate into larger
  projects. For example, there may be an experimental version of Lwt
  based on it. To that end, Luv is as unopinionated as possible. It
  sticks closely to the libuv API, making no unnecessary design
  decisions, and deviating only where changes are necessary to integrate
  with OCaml, or where libuv has an awkward API due to the limitations
  of C.

  And with all that… Happy systems programming :)


[**Luv**] <https://github.com/aantron/luv>

[libuv] <http://github.com/libuv/libuv>

[`Unix'] <https://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html>

[list of modules in the API docs]
<https://aantron.github.io/luv/luv/index.html#api-reference>

[Project page] <https://github.com/aantron/luv>

[User guide] <https://aantron.github.io/luv/>

[API reference]
<https://aantron.github.io/luv/luv/index.html#api-reference>

[Examples] <https://github.com/aantron/luv/tree/master/example>

[documentation of libuv] <http://docs.libuv.org/en/v1.x/>

[event-driven programming]
<https://aantron.github.io/luv/basics.html#event-loops>

[multithreading] <https://aantron.github.io/luv/threads.html>

[multiprocessing] <https://aantron.github.io/luv/processes.html>

[well-maintained]
<https://github.com/libuv/libuv/blob/master/MAINTAINERS.md#readme>

[many platforms]
<https://github.com/libuv/libuv/blob/master/SUPPORTED_PLATFORMS.md#readme>

[ctypes] <https://github.com/ocamllabs/ocaml-ctypes>

[test suite] <https://github.com/aantron/luv/tree/master/test>


Musings on extended pattern-matching syntaxes
═════════════════════════════════════════════

  Archive:
  
<https://discuss.ocaml.org/t/musings-on-extended-pattern-matching-syntaxes/3600/57>


Continuing this old thread, Alexander Bashkirov announced
─────────────────────────────────────────────────────────

  We reviewed this thread quite carefully along with features of other
  languages and summed up the results [here].

  We also started an [active patterns RFC discussion].


[here]
<https://github.com/bash-spbu/ways-of-pattern-matching-extending-overview>

[active patterns RFC discussion] <https://github.com/ocaml/RFCs/pull/12>


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed of the
  archives].

  If you also wish to receive it every week by mail, you may subscribe
  [online].

  [Alan Schmitt]


[send me a message] <mailto:alan.schm...@polytechnique.org>

[the archive] <http://alan.petitepomme.net/cwn/>

[RSS feed of the archives] <http://alan.petitepomme.net/cwn/cwn.rss>

[online] <http://lists.idyll.org/listinfo/caml-news-weekly/>

[Alan Schmitt] <http://alan.petitepomme.net/>

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