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OCaml 4.06.0

This page describes OCaml version 4.06.0, released on 2017-11-03.

Opam Switches

This release is available as multiple OPAM switches:

  • 4.06.0 — Official 4.06.0 release
  • 4.06.0+afl — Official 4.06.0 release with afl-fuzz instrumentation
  • 4.06.0+default-unsafe-string — Official 4.06.0 release without safe strings by default
  • 4.06.0+flambda — Official 4.06.0 release with flambda activated
  • 4.06.0+force-safe-string — Official 4.06.0 release with -safe-string enabled.
  • 4.06.0+fp — Official 4.06.0 release with frame-pointers
  • 4.06.0+fp+flambda — Official 4.06.0 release with frame-pointers and flambda activated

What's new

Some of the highlights in release 4.06 are:

  • Strings (type string) are now immutable by default. In-place modification must use the type bytes of byte sequences, which is distinct from string. This corresponds to the -safe-string compile-time option, which was introduced in OCaml 4.02 in 2014, and which is now the default.

  • Object types can now extend a previously-defined object type, as in <t; a: int>.

  • Destructive substitution over module signatures can now express more substitutions, such as S with type M.t := type-expr and S with module M.N := path.

  • Users can now define operators that look like array indexing, e.g. let ( .%() ) = List.nth in [0; 1; 2].%(1)

  • New escape \u{XXXX} in string literals, denoting the UTF-8 encoding of the Unicode code point XXXX.

  • Full Unicode support was added to the Windows runtime system. In particular, file names can now contain Unicode characters.

  • An alternate register allocator based on linear scan can be selected with ocamlopt -linscan. It reduces compilation time compared with the default register allocator.

  • The Num library for arbitrary-precision integer and rational arithmetic is no longer part of the core distribution and can be found as a separate OPAM package.

For a comprehensive list of changes and details on all new features, bug fixes, optimizations, etc., please consult the changelog.

Source distribution

  • Source tarball (.tar.gz) for compilation under Unix (including Linux and MacOS X) and Microsoft Windows (including Cygwin).
  • Also available in .zip format.
  • OPAM is a source-based distribution of OCaml and many companion libraries and tools. Compilation and installation are automated by powerful package managers.
  • The official development repo is hosted on GitHub.

The INSTALL file of the distribution provides detailed compilation and installation instructions -- see also the Windows release notes for instructions on how to build under Windows.

Alternative Compilers

Additionally, the following projects allow you to compile OCaml code to targets traditionally associated with other languages:

  • Js_of_ocaml is a stable OCaml to JavaScript compiler.
  • BuckleScript is a newer OCaml to JavaScript compiler. See its wiki for an explanation of how it differs from js_of_ocaml.
  • OCaml-java is a stable OCaml to Java compiler.

User's manual

The user's manual for OCaml can be:


This is the changelog.

(Changes that can break existing programs are marked with a "*")

Language features:

  • MPR#6271, MPR#7529, GPR#1249: Support let open M in ... in class expressions and class type expressions.
    (Alain Frisch, reviews by Thomas Refis and Jacques Garrigue)

  • GPR#792: fix limitations of destructive substitutions, by allowing S with type t := type-expr, S with type M.t := type-expr, S with module M.N := path.
    (Valentin Gatien-Baron, review by Jacques Garrigue and Leo White)

  • GPR#1064, GPR#1392: extended indexing operators, add a new class of user-defined indexing operators, obtained by adding at least one operator character after the dot symbol to the standard indexing operators: e,g .%(), .?[], .@{}<-:

    let ( .%() ) = List.nth in
    [0; 1; 2].%(1)

    After this change, functions or methods with an explicit polymorphic type annotation and of which the first argument is optional now requires a space between the dot and the question mark, e.g. <f:'a.?opt:int->unit> must now be written <f:'a. ?opt:int->unit>.
    (Florian Angeletti, review by Damien Doligez and Gabriel Radanne)

  • GPR#1118: Support inherited field in object type expression

    type t = < m : int >
    type u = < n : int; t; k : int >

    (Runhang Li, reivew by Jeremy Yallop, Leo White, Jacques Garrigue, and Florian Angeletti)

  • GPR#1232: Support Unicode character escape sequences in string literals via the \u{X+} syntax. These escapes are substituted by the UTF-8 encoding of the Unicode character.
    (Daniel Bünzli, review by Damien Doligez, Alain Frisch, Xavier Leroy and Leo White)
  • GPR#1247: M.(::) construction for expressions and patterns (plus fix printing of (::) in the toplevel)
    (Florian Angeletti, review by Alain Frisch, Gabriel Scherer)
  • GPR#1252: The default mode is now safe-string, can be overridden at configure time or at compile time. (See GPR#1386 below for the configure-time options) This breaks the code that uses the string type as mutable strings (instead of Bytes.t, introduced by 4.02 in 2014).
    (Damien Doligez)

  • GPR#1253: Private extensible variants This change breaks code relying on the undocumented ability to export extension constructors for abstract type in signature. Briefly,

    module type S = sig
      type t
      type t += A

    must now be written

    module type S = sig
      type t = private ..
      type t += A

    (Leo White, review by Alain Frisch)

  • GPR#1333: turn off warning 40 by default (Constructor or label name used out of scope)
    (Leo White)

  • GPR#1348: accept anonymous type parameters in with constraints: S with type _ t = int.
    (Valentin Gatien-Baron, report by Jeremy Yallop)

Type system

  • MPR#248, GPR#1225: unique names for weak type variables

    # ref [];;
    - : '__weak1 list ref = {contents = []}

(Florian Angeletti, review by Frédéric Bour, Jacques Garrigue, Gabriel Radanne and Gabriel Scherer)

  • MPR#6738, MPR#7215, MPR#7231, GPR#556: Add a new check that let rec bindings are well formed.
    (Jeremy Yallop, reviews by Stephen Dolan, Gabriel Scherer, Leo White, and Damien Doligez)
  • GPR#1142: Mark assertions nonexpansive, so that assert false can be used as a placeholder for a polymorphic function.
    (Stephen Dolan)

Standard library:

  • MPR#1771, MPR#7309, GPR#1026: Add update to maps. Allows to update a binding in a map or create a new binding if the key had no binding

    val update: key -> ('a option -> 'a option) -> 'a t -> 'a t

    (Sébastien Briais, review by Daniel Buenzli, Alain Frisch and Gabriel Scherer)

  • MPR#7515, GPR#1147: Arg.align now optionally uses the tab character '\t' to separate the "unaligned" and "aligned" parts of the documentation string. If tab is not present, then space is used as a fallback. Allows to have spaces in the unaligned part, which is useful for Tuple options. (Nicolas Ojeda Bar, review by Alain Frisch and Gabriel Scherer)

  • GPR#615: Format, add symbolic formatters that output symbolic pretty-printing items. New fields have been added to the formatter_out_functions record, thus this change will break any code building such record from scratch. When building Format.formatter_out_functions values redefinining the out_spaces field, { fmt_out_funs with out_spaces = f; } should be replaced by { fmt_out_funs with out_spaces = f; out_indent = f; } to maintain the old behavior.
    (Richard Bonichon and Pierre Weis, review by Alain Frisch, original request by Spiros Eliopoulos in GPR#506)

  • GPR#943: Fixed the divergence of the Pervasives module between the stdlib and threads implementations. In rare circumstances this can change the behavior of existing applications: the implementation of Pervasives.close_out used when compiling with thread support was inconsistent with the manual. It will now not suppress exceptions escaping Pervasives.flush anymore. Developers who want the old behavior should use Pervasives.close_out_noerr instead. The stdlib implementation, used by applications not compiled with thread support, will now only suppress Sys_error exceptions in Pervasives.flush_all. This should allow exceedingly unlikely assertion exceptions to escape, which could help reveal bugs in the standard library.
    (Markus Mottl, review by Hezekiah M. Carty, Jeremie Dimino, Damien Doligez, Alain Frisch, Xavier Leroy, Gabriel Scherer and Mark Shinwell)

  • GPR#1034: List.init : int -> (int -> 'a) -> 'a list
    (Richard Degenne, review by David Allsopp, Thomas Braibant, Florian Angeletti, Gabriel Scherer, Nathan Moreau, Alain Frisch)

  • GRP#1091 Add the Uchar.{bom,rep} constants.
    (Daniel Bünzli, Alain Frisch)

  • GPR#1091: Add Buffer.add_utf_{8,16le,16be}_uchar to encode Uchar.t values to the corresponding UTF-X transformation formats in Buffer.t values.
    (Daniel Bünzli, review by Damien Doligez, Max Mouratov)

  • GPR#1175: Bigarray, add a change_layout function to each Array[N] submodules.
    (Florian Angeletti)

  • GPR#1306: In the MSVC and Mingw ports, Sys.rename src dst no longer fails if file dst exists, but replaces it with file src, like in the other ports.
    (Xavier Leroy)
  • GPR#1314: Format, use the optional width information when formatting a boolean: "%8B", "%-8B" for example
    (Xavier Clerc, review by Gabriel Scherer)

  • c9cc0f25138ce58e4f4e68c4219afe33e2a9d034: Resurrect tabulation boxes in module Format. Rewrite/extend documentation of tabulation boxes.
    (Pierre Weis)

Other libraries:

  • MPR#7564, GPR#1211: Allow forward slashes in the target of symbolic links created by Unix.symlink under Windows. (Nicolas Ojeda Bar, review by David Allsopp)
  • MPR#7640, GPR#1414: reimplementation of Unix.execvpe to fix issues with the 4.05 implementation. The main issue is that the current directory was always searched (last), even if the current directory is not listed in the PATH.
    (Xavier Leroy, report by Louis Gesbert and Arseniy Alekseyev, review by Ivan Gotovchits)
  • GPR#997, GPR#1077: Deprecate Bigarray.*.map_file and add Unix.map_file as a first step towards moving Bigarray to the stdlib
    (Jérémie Dimino and Xavier Leroy)
  • GPR#1178: remove the Num library for arbitrary-precision arithmetic. It now lives as a separate project with an OPAM package called num.
    (Xavier Leroy)
  • GPR#1217: Restrict Unix.environment in privileged contexts; add Unix.unsafe_environment.
    (Jeremy Yallop, review by Mark Shinwell, Nicolas Ojeda Bar, Damien Doligez and Hannes Mehnert)

  • GPR#1321: Reimplement Unix.isatty on Windows. It no longer returns true for the null device.
    (David Allsopp)

Compiler user-interface and warnings:

  • MPR#7361, GPR#1248: support ocaml.warning in all attribute contexts, and arrange so that ocaml.ppwarning is correctly scoped by surrounding ocaml.warning attributes.
    (Alain Frisch, review by Florian Angeletti and Thomas Refis)

  • MPR#7444, GPR#1138: trigger deprecation warning when a "deprecated" attribute is hidden by signature coercion.
    (Alain Frisch, report by bmillwood, review by Leo White)

  • MPR#7472: ensure .cmi files are created atomically, to avoid corruption of .cmi files produced simultaneously by a run of ocamlc and a run of ocamlopt.
    (Xavier Leroy, from a suggestion by Gerd Stolpmann)

  • MPR#7514, GPR#1152: add -dprofile option, similar to -dtimings but also displays memory allocation and consumption. The corresponding addition of a new compiler-internal Profile module may affect some users of compilers-libs/ocamlcommon (by creating module conflicts).
    (Valentin Gatien-Baron, report by Gabriel Scherer)
  • MPR#7620, GPR#1317: Typecore.force_delayed_checks does not run with -i option.
    (Jacques Garrigue, report by Jun Furuse)

  • MPR#7624: handle warning attributes placed on let bindings.
    (Xavier Clerc, report by dinosaure, review by Alain Frisch)

  • GPR#896: -compat-32 is now taken into account when building .cmo/.cma.
    (Hugo Heuzard)

  • GPR#948: the compiler now reports warnings-as-errors by prefixing them with "Error (warning ..):", instead of "Warning ..:" and a trailing "Error: Some fatal warnings were triggered" message.
    (Valentin Gatien-Baron, review by Alain Frisch)

  • GPR#1032: display the output of -dtimings as a hierarchy.
    (Valentin Gatien-Baron, review by Gabriel Scherer)

  • GPR#1114, GPR#1393, GPR#1429: refine the (ocamlc -config) information on C compilers: the variables {bytecode,native}_c_compiler are deprecated (the distinction is now mostly meaningless) in favor of a single c_compiler variable combined with ocaml{c,opt}_cflags and ocaml{c,opt}_cppflags.
    (Sébastien Hinderer, Jeremy Yallop, Gabriel Scherer, review by Adrien Nader and David Allsopp)

  • GPR#1189: allow MSVC ports to use -l option in ocamlmklib.
    (David Allsopp)
  • GPR#1332: fix ocamlc handling of -output-complete-obj.
    (François Bobot)

  • GPR#1336: -thread and -vmthread option information is propagated to PPX rewriters.
    (Jun Furuse, review by Alain Frisch)

Code generation and optimizations:

  • MPR#5324, GPR#375: An alternative Linear Scan register allocator for ocamlopt, activated with the -linscan command-line flag. This allocator represents a trade-off between worse generated code performance for higher compilation speed (especially interesting in some cases graph coloring is necessarily quadratic).
    (Marcell Fischbach and Benedikt Meurer, adapted by Nicolas Ojeda Bar, review by Nicolas Ojeda Bar and Alain Frisch)

  • MPR#6927, GPR#988: On macOS, when compiling bytecode stubs, plugins, and shared libraries through -output-obj, generate dylibs instead of bundles.

  • MPR#7447, GPR#995: incorrect code generation for nested recursive bindings.
    (Leo White and Jeremy Yallop, report by Stephen Dolan)

  • MPR#7501, GPR#1089: Consider arrays of length zero as constants when using Flambda.
    (Pierre Chambart, review by Mark Shinwell and Leo White)

  • MPR#7531, GPR#1162: Erroneous code transformation at partial applications.
    (Mark Shinwell)

  • MPR#7614, GPR#1313: Ensure that inlining does not depend on the order of symbols (flambda).
    (Leo White, Xavier Clerc, report by Alex, review by Gabriel Scherer and Pierre Chambart)

  • MPR#7616, GPR#1339: don't warn on mutation of zero size blocks.
    (Leo White)

  • MPR#7631, GPR#1355: -linscan option crashes ocamlopt.
    (Xavier Clerc, report by Paul Steckler)

  • MPR#7642, GPR#1411: ARM port: wrong register allocation for integer multiply on ARMv4 and ARMv5; possible wrong register allocation for floating-point multiply and add on VFP and for floating-point negation and absolute value on soft FP emulation.
    (Xavier Leroy, report by Stéphane Glondu and Ximin Luo, review and additional sightings by Mark Shinwell)

  • GPR#659: Remove support for SPARC native code generation.
    (Mark Shinwell)
  • GPR#850: Optimize away some physical equality.
    (Pierre Chambart, review by Mark Shinwell and Leo White)

  • GPR#856: Register availability analysis.
    (Mark Shinwell, Thomas Refis, review by Pierre Chambart)

  • GPR#1143: tweaked several allocation functions in the runtime by checking for likely conditions before unlikely ones and eliminating some redundant checks.
    (Markus Mottl, review by Alain Frisch, Xavier Leroy, Gabriel Scherer, Mark Shinwell and Leo White)

  • GPR#1183: compile curried functors to multi-argument functions earlier in the compiler pipeline; correctly propagate [@@inline] attributes on such functors; mark functor coercion veneers as stubs.
    (Mark Shinwell, review by Pierre Chambart and Leo White)

  • GPR#1195: Merge functions based on partiality rather than Parmatch.irrefutable. (Leo White, review by Thomas Refis, Alain Frisch and Gabriel Scherer)

  • GPR#1215: Improve compilation of short-circuit operators (Leo White, review by Frédéric Bour and Mark Shinwell)

  • GPR#1250: illegal ARM64 assembly code generated for large combined allocations.
    (report and initial fix by Steve Walk, review and final fix by Xavier Leroy)

  • GPR#1271: Don't generate Ialloc instructions for closures that exceed Max_young_wosize; instead allocate them on the major heap. (Related to GPR#1250.)
    (Mark Shinwell)

  • GPR#1294: Add a configure-time option to remove the dynamic float array optimization and add a floatarray type to let the user choose when to flatten float arrays. Note that float-only records are unchanged: they are still optimized by unboxing their fields.
    (Damien Doligez, review by Alain Frisch and Mark Shinwell)

  • GPR#1304: Mark registers clobbered by PLT stubs as destroyed across allocations.
    (Mark Shinwell, Xavier Clerc, report and initial debugging by Valentin Gatien-Baron)

  • GPR#1323: make sure that frame tables are generated in the data section and not in the read-only data section, as was the case before in the PPC and System-Z ports. This avoids relocations in the text segment of shared libraries and position-independent executables generated by ocamlopt.
    (Xavier Leroy, review by Mark Shinwell)

  • GPR#1330: when generating dynamically-linkable code on AArch64, always reference symbols (even locally-defined ones) through the GOT.
    (Mark Shinwell, review by Xavier Leroy)


  • MPR#1956, GPR#973: tools/check-symbol-names checks for globally linked names not namespaced with caml_. (Stephen Dolan)

  • MPR#6928, GPR#1103: ocamldoc, do not introduce an empty <h1> in index.html when no -title has been provided.
    (Pierre Boutillier)

  • MPR#7048: ocamldoc, in -latex mode, don't escape Latin-1 accented letters.
    (Xavier Leroy, report by Hugo Herbelin)

  • MPR#7351: ocamldoc, use semantic tags rather than <br> tags in the html backend.
    (Florian Angeletti, request and review by Daniel Bünzli )

  • MPR#7352, MPR#7353: ocamldoc, better paragraphs in html output.
    (Florian Angeletti, request by Daniel Bünzli)

  • MPR#7363, GPR#830: ocamldoc, start heading levels at {1 not {2 or {6. This change modifies the mapping between ocamldoc heading level and html heading level, breaking custom css style for ocamldoc.
    (Florian Angeletti, request and review by Daniel Bünzli)

  • MPR#7478, GPR#1037: ocamldoc, do not use as a module preamble documentation comments that occur after the first module element. This change may break existing documentation. In particular, module preambles must now come before any open statement.
    (Florian Angeletti, review by David Allsopp and report by Daniel Bünzli)

  • MPR#7521, GPR#1159: ocamldoc, end generated latex file with a new line.
    (Florian Angeletti)

  • MPR#7575, GPR#1219: Switch compilers from -no-keep-locs to -keep-locs by default: produced .cmi files will contain locations. This provides better error messages. Note that, as a consequence, .cmi digests now depend on the file path as given to the compiler.
    (Daniel Bünzli)

  • MPR#7610, GPR#1346: caml.el (the Emacs editing mode) was cleaned up and made compatible with Emacs 25.
    (Stefan Monnier, Christophe Troestler)

  • MPR#7635, GPR#1383: ocamldoc, add an identifier to module and module type elements.
    (Florian Angeletti, review by Yawar Amin and Gabriel Scherer)

  • GPR#681, GPR#1426: Introduce ocamltest, a new test driver for the OCaml compiler testsuite.
    (Sébastien Hinderer, review by Damien Doligez)

  • GPR#1012: ocamlyacc, fix parsing of raw strings and nested comments, as well as the handling of ' characters in identifiers.
    (Demi Obenour)

  • GPR#1045: ocamldep, add a -shared option to generate dependencies for native plugin files (i.e., .cmxs files).
    (Florian Angeletti, suggestion by Sébastien Hinderer)

  • GPR#1078: add a subcommand -depend to ocamlc and ocamlopt, to behave as ocamldep. Should be used mostly to replace ocamldep in the boot directory to reduce its size in the future.
    (Fabrice Le Fessant)

  • GPR#1036: ocamlcmt (tools/read_cmt) is installed, converts .cmt to .annot.
    (Fabrice Le Fessant)

  • GPR#1180: Add support for recording numbers of direct and indirect calls over the lifetime of a program when using Spacetime profiling.
    (Mark Shinwell)

  • GPR#1457, ocamldoc: restore label for exception in the LaTeX backend (omitted since 4.04.0).
    (Florian Angeletti, review by Gabriel Scherer)


  • MPR#7570: remove unusable -plugin option from the toplevel.
    (Florian Angeletti)

  • GPR#1041: -nostdlib no longer ignored by toplevel.
    (David Allsopp, review by Xavier Leroy)

  • GPR#1231: improved printing of unicode texts in the toplevel, unless OCAMLTOP_UTF_8 is set to false.
    (Florian Angeletti, review by Daniel Bünzli, Xavier Leroy and Gabriel Scherer)

Runtime system:

  • GPR#71: The runtime can now be shut down gracefully by means of the new caml_shutdown and caml_startup_pooled functions. The new c flag in OCAMLRUNPARAM enables shutting the runtime properly on process exit.
    (Max Mouratov, review and discussion by Damien Doligez, Gabriel Scherer, Mark Shinwell, Thomas Braibant, Stephen Dolan, Pierre Chambart, François Bobot, Jacques Garrigue, David Allsopp, and Alain Frisch)

  • GPR#938, GPR#1170, GPR#1289: Stack overflow detection on 64-bit Windows.
    (Olivier Andrieu, tweaked by David Allsopp)

  • GPR#1070, GPR#1295: enable gcc typechecking for caml_alloc_sprintf, caml_gc_message. Make caml_gc_message a variadic function. Fix many caml_gc_message format strings.
    (Olivier Andrieu, review and 32bit fix by David Allsopp)

  • GPR#1073: Remove statically allocated compare stack.
    (Stephen Dolan)

  • GPR#1086: in Sys.getcwd, just fail instead of calling getwd() if HAS_GETCWD is not set.
    (Report and first fix by Sebastian Markbåge, final fix by Xavier Leroy, review by MarK Shinwell)

  • GPR#1269: Remove 50ms delay at exit for programs using threads.
    (Valentin Gatien-Baron, review by Stephen Dolan)

  • GPR#1309: open files with O_CLOEXEC (or equivalent) in caml_sys_open, thus unifying the semantics between Unix and Windows and also eliminating race condition on Unix.
    (David Allsopp, report by Andreas Hauptmann)
  • GPR#1326: Enable use of CFI directives in AArch64 and ARM runtime systems' assembly code (asmrun/arm64.S). Add CFI directives to enable unwinding through caml_c_call and caml_call_gc with correct termination of unwinding at main.
    (Mark Shinwell, review by Xavier Leroy and Gabriel Scherer, with thanks to Daniel Bünzli and Fu Yong Quah for testing)

  • GPR#1338: Add -g for bytecode runtime system compilation.
    (Mark Shinwell)

  • GPR#1416, GPR#1444: switch the Windows 10 Console to UTF-8 encoding.
    (David Allsopp, reviews by Nicolás Ojeda Bär and Xavier Leroy)

Manual and documentation:

  • MPR#6548: remove obsolete limitation in the description of private type abbreviations.
    (Florian Angeletti, suggestion by Leo White)

  • MPR#6676, GPR#1110: move record notation to tutorial.
    (Florian Angeletti, review by Gabriel Scherer)

  • MPR#6676, GPR#1112: move local opens to tutorial.
    (Florian Angeletti)

  • MPR#6676, GPR#1153: move overriding class definitions to reference manual and tutorial.
    (Florian Angeletti)

  • MPR#6709: document the associativity and precedence level of pervasive operators.
    (Florian Angeletti, review by David Allsopp)

  • MPR#7254, GPR#1096: Rudimentary documentation of ocamlnat.
    (Mark Shinwell)

  • MPR#7281, GPR#1259: fix .TH macros in generated manpages.
    (Olaf Hering)

  • MPR#7507: Align the description of the printf conversion specification "%g" with the ISO C90 description.
    (Florian Angeletti, suggestion by Armaël Guéneau)

  • MPR#7551, GPR#1194 : make the final ";;" potentially optional in caml_example.
    (Florian Angeletti, review and suggestion by Gabriel Scherer)

  • MPR#7588, GPR#1291: make format documentation predictable.
    (Florian Angeletti, review by Gabriel Radanne)

  • MPR#7604: Minor Ephemeron documentation fixes.
    (Miod Vallat, review by Florian Angeletti)

  • GPR#594: New chapter on polymorphism troubles: weakly polymorphic types, polymorphic recursion,and higher-ranked polymorphism.
    (Florian Angeletti, review by Damien Doligez, Gabriel Scherer, and Gerd Stolpmann)

  • GPR#1187: Minimal documentation for compiler plugins.
    (Florian Angeletti)

  • GPR#1202: Fix Typos in comments as well as basic grammar errors.
    (JP Rodi, review and suggestions by David Allsopp, Max Mouratov, Florian Angeletti, Xavier Leroy, Mark Shinwell and Damien Doligez)

  • GPR#1220: Fix -keep-docs option in ocamlopt manpage.
    (Etienne Millon)

Compiler distribution build system:

  • MPR#6373, GPR#1093: Suppress trigraph warnings from macOS assembler.
    (Mark Shinwell)

  • MPR#7639, GPR#1371: fix configure script for correct detection of int64 alignment on Mac OS X 10.13 (High Sierra) and above; fix bug in configure script relating to such detection.
    (Mark Shinwell, report by John Whitington, review by Xavier Leroy)

  • GPR#558: enable shared library and natdynlink support on more Linux platforms.
    (Felix Janda, Mark Shinwell)

  • GPR#1104: remove support for the NeXTStep platform.
    (Sébastien Hinderer)
  • GPR#1130: enable detection of IBM XL C compiler (one need to run configure with -cc <path to xlc compiler>). Enable shared library support for bytecode executables on AIX/xlc (tested on AIX 7.1, XL C 12). To enable 64-bit, run both configure and make world with OBJECT_MODE=64.
    (Konstantin Romanov, Enrique Naudon)

  • GPR#1203: speed up the manual build by using ocamldoc.opt.
    (Gabriel Scherer, review by Florian Angeletti)

  • GPR#1214: harden config/Makefile against # characters in PREFIX.
    (Gabriel Scherer, review by David Allsopp and Damien Doligez)

  • GPR#1216: move Compplugin and friends from BYTECOMP to COMP.
    (Leo White, review by Mark Shinwell)

  • GPR#1242: disable C plugins loading by default.
    (Alexey Egorov)
  • GPR#1275: correct configure test for Spacetime availability.
    (Mark Shinwell)

  • GPR#1278: discover presence of <sys/shm.h> during configure for afl runtime.
    (Hannes Mehnert)

  • GPR#1386: provide configure-time options to fine-tune the safe-string options and default settings changed by GPR#1525.

    The previous configure option -safe-string is now renamed -force-safe-string.

    At configure-time, -force-safe-string forces all module to use immutable strings (this disables the per-file, compile-time -unsafe-string option). The new default-(un)safe-string options let you set the default choice for the per-file compile-time option. (The new GPR#1252 behavior corresponds to having -default-safe-string, while 4.05 and older had -default-unsafe-string).

    (Gabriel Scherer, review by Jacques-Pascal Deplaix and Damien Doligez)

  • GPR#1409: Fix to enable NetBSD/powerpc to work.
    (Håvard Eidnes)

Internal/compiler-libs changes:

  • MPR#6826, GPR#828, GPR#834: improve compilation time for open.
    (Alain Frisch, review by Frédéric Bour and Jacques Garrigue)

  • MPR#7127, GPR#454, GPR#1058: in toplevel, print bytes and strip strings longer than the size specified by the print_length directive.
    (Fabrice Le Fessant, initial PR by Junsong Li)

  • GPR#406: remove polymorphic comparison for Types.constructor_tag in compiler.
    (Dwight Guth, review by Gabriel Radanne, Damien Doligez, Gabriel Scherer, Pierre Chambart, Mark Shinwell)

  • GRP#1119: Change Set (private) type to inline records.
    (Albin Coquereau)

  • GPR#1127: move config/{m,s}.h to byterun/caml and install them. User code should not have to include them directly since they are included by other header files. Previously {m,s}.h were not installed but they were substituted into caml/config.h; they are now just #include-d by this file. This may break some scripts relying on the (unspecified) presence of certain #define in config.h instead of m.h and s.h — they can be rewritten to try to grep those files if they exist.
    (Sébastien Hinderer)
  • GPR#1281: avoid formatter flushes inside exported printers in Location.
    (Florian Angeletti, review by Gabriel Scherer)

Bug fixes

  • MPR#5927: Type equality broken for conjunctive polymorphic variant tags.
    (Jacques Garrigue, report by Leo White)

  • MPR#6329, GPR#1437: Introduce padding word before "data_end" symbols to ensure page table tests work correctly on an immediately preceding block of zero size.
    (Mark Shinwell, review by Xavier Leroy)

  • MPR#6587: only elide Pervasives from printed type paths in unambiguous context.
    (Florian Angeletti and Jacques Garrigue)

  • MPR#6934: nonrec misbehaves with GADTs.
    (Jacques Garrigue, report by Markus Mottl)

  • MPR#7070, GPR#1139: Unexported values can cause non-generalisable variables error.
    (Leo White)

  • MPR#7261: Warn on type constraints in GADT declarations.
    (Jacques Garrigue, report by Fabrice Le Botlan)

  • MPR#7321: Private type in signature clashes with type definition via functor instantiation.
    (Jacques Garrigue, report by Markus Mottl)

  • MPR#7372, GPR#834: fix type-checker bug with GADT and inline records.
    (Alain Frisch, review by Frédéric Bour and Jacques Garrigue)

  • MPR#7344: Inconsistent behavior with type annotations on let.
    (Jacques Garrigue, report by Leo White)

  • MPR#7468: possible GC problem in caml_alloc_sprintf.
    (Xavier Leroy, discovery by Olivier Andrieu)

  • MPR#7496: Fixed conjunctive polymorphic variant tags do not unify with themselves.
    (Jacques Garrigue, report by Leo White)

  • MPR#7506: pprintast ignores attributes in tails of a list.
    (Alain Frisch, report by Kenichi Asai and Gabriel Scherer)

  • MPR#7513: List.compare_length_with mishandles negative numbers / overflow.
    (Fabrice Le Fessant, report by Jeremy Yallop)

  • MPR#7519: Incorrect rejection of program due to faux scope escape.
    (Jacques Garrigue, report by Markus Mottl)

  • MPR#7540, GPR#1179: Fixed setting of breakpoints within packed modules for ocamldebug.
    (Hugo Herbelin, review by Gabriel Scherer, Damien Doligez)

  • MPR#7543: short-paths printtyp can fail on packed type error messages.
    (Florian Angeletti)

  • MPR#7553, GPR#1191: Prevent repeated warnings with recursive modules.
    (Leo White, review by Josh Berdine and Alain Frisch)

  • MPR#7563, GPR#1210: code generation bug when a module alias and an extension constructor have the same name in the same module.
    (Gabriel Scherer, report by Manuel Fähndrich, review by Jacques Garrigue and Leo White)

  • MPR#7591, GPR#1257: on x86-64, frame table is not 8-aligned.
    (Xavier Leroy, report by Mantis user "voglerr", review by Gabriel Scherer)

  • MPR#7601, GPR#1320: It seems like a hidden non-generalized type variable remains in some inferred signatures, which leads to strange errors.
    (Jacques Garrigue, report by Mandrikin)

  • MPR#7609: use-after-free memory corruption if a program debugged under ocamldebug calls Pervasives.flush_all.
    (Xavier Leroy, report by Paul Steckler, review by Gabriel Scherer)

  • MPR#7612, GPR#1345: afl-instrumentation bugfix for classes.
    (Stephen Dolan, review by Gabriel Scherer and David Allsopp)

  • MPR#7617, MPR#7618, GPR#1318: Ambiguous (mistakenly) type escaping the scope of its equation.
    (Jacques Garrigue, report by Thomas Refis)

  • MPR#7619, GPR#1387: position of the optional last semi-column not included in the position of the expression (same behavior as for lists).
    (Christophe Raffalli, review by Gabriel Scherer)

  • MPR#7638: in the Windows Mingw64 port, multithreaded programs compiled to bytecode could crash when raising an exception from C code. This looks like a Mingw64 issue, which we work around with GCC builtins.
    (Xavier Leroy)

  • MPR#7656, GPR#1423: false 'unused type/constructor/value' alarms in the 4.06 development version.
    (Alain Frisch, review by Jacques Garrigue, report by Jacques-Pascal Deplaix)

  • MPR#7657, GPR#1424: ensures correct call-by-value semantics when eta-expanding functions to eliminate optional arguments.
    (Alain Frisch, report by sliquister, review by Leo White and Jacques Garrigue)

  • MPR#7658, GPR#1439: Fix Spacetime runtime system compilation with -force-safe-string.
    (Mark Shinwell, report by Christoph Spiel, review by Gabriel Scherer)

  • GPR#1155: Fix a race condition with WAIT_NOHANG on Windows.
    (Jérémie Dimino and David Allsopp)

  • GPR#1199: Pretty-printing formatting cleanup in pprintast.
    (Ethan Aubin, suggestion by Gabriel Scherer, review by David Allsopp, Florian Angeletti, and Gabriel Scherer)

  • GPR#1223: Fix corruption of the environment when using -short-paths with the toplevel.
    (Leo White, review by Alain Frisch)

  • GPR#1243: Fix pprintast for #... infix operators.
    (Alain Frisch, report by Omar Chebib)

  • GPR#1324: ensure that flambda warning are printed only once.
    (Xavier Clerc)

  • GPR#1329: Prevent recursive polymorphic variant names.
    (Jacques Garrigue, fix suggested by Leo White)

  • GPR#1308: Only treat pure patterns as inactive.
    (Leo White, review by Alain Frisch and Gabriel Scherer)

  • GPR#1390: fix the [@@unboxed] type check to accept parametrized types.
    (Leo White, review by Damien Doligez)

  • GPR#1407: Fix raw_spacetime_lib.
    (Leo White, review by Gabriel Scherer and Damien Doligez)