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Change Log: 2.085.0

previous version: 2.084.1 – next version: 2.085.1

Download D 2.085.0
released Mar 01, 2019

2.085.0 comes with 26 major changes and 58 fixed Bugzilla issues. A huge thanks goes to the 49 contributors who made 2.085.0 possible.

List of all bug fixes and enhancements in D 2.085.0.

Compiler changes

  1. Add support for Objective-C classes

    Prior to this release D interfaces were used to represent Objective-C classes. Now proper support for Objective-C classes has been added and D classes can be used instead to represent Objective-C classes. It's preferred to use D classes to represent Objective-C classes.

    This release also adds support for implementing Objective-C subclasses and methods in D.

    To match the behavior in Objective-C some additional changes have been made:

    • static and final methods are virtual. Although final methods are virtual it's not possible to override a final method in a subclass
    • static methods are overridable in subclasses


    extern (Objective-C)
    class NSObject
        static NSObject alloc() @selector("alloc");
        NSObject init() @selector("init");
        void release() @selector("release");
    extern (Objective-C)
    class Foo : NSObject
        override static Foo alloc() @selector("alloc");
        override Foo init() @selector("init");
        int bar(int a) @selector("bar:")
            return a;
    void main()
        auto foo = Foo.alloc.init;
        scope (exit) foo.release();
        assert( == 3);
  2. Add support for Objective-C instance variable

    It's now possible to declare instance variables in Objective-C classes.

    Instance variables in Objective-C are non-fragile. That means that the base class can change (add or remove instance variables) without the subclasses needing to recompile or relink. Thanks to this feature it's not necessary to declare instance variables when creating bindings to Objective-C classes.


    extern (Objective-C)
    class NSObject {}
    extern (Objective-C)
    class Foo : NSObject
        int bar;
        static Foo alloc() @selector("alloc");
        Foo init() @selector("init");
        void release() @selector("release");
        void getBar() @selector("getBar")
            return bar;
    void main()
        auto foo = Foo.alloc.init;
        scope (exit) foo.release(); = 3;
        assert(foo.getBar() == 3);
  3. Add support for Objective-C super calls

    It's now possible to implement an Objective-C method and make a super call to a method in the base class.


    extern (Objective-C)
    class NSObject
        void release() @selector("release");
    extern (Objective-C)
    class Foo : NSObject
        int foo() @selector("foo")
            return 3;
    extern (Objective-C)
    class Bar : Foo
        static Bar alloc() @selector("alloc");
        Bar init() @selector("init");
        override int foo() @selector("foo")
            return + 1;
    void main()
        auto bar = Bar.alloc.init;
        scope (exit) bar.release();
        assert( == 4);
  4. Deprecate Objective-C interfaces

    Prior to this release, it was necessary to represent an Objective-C class as a D interface. Now support for Objective-C classes has been implemented and the class keyword should be used instead.

    The reason for this deprecation is to allow extern (Objective-C) interfaces to be repurposed for representing Objective-C protocols in the future.


    extern (Objective-C) interface NSObject {} // deprecated

    Replace with:

    extern (Objective-C) class NSObject {}
  5. Context-aware assertion error messages

    With this release DMD supports generating context-aware assertion error messages when no error message has been provided by the user. For example, currently the following file:

    void main()
        int a, b = 2;
        assert(a == b);

    would yield this error when compiled and run:

    > dmd -run main.d
    core.exception.AssertError@main.d(4): Assertion failure
    ??:? _d_assertp [0x1c4eae48]
    onlineapp.d:4 _Dmain [0x1c4ead85]

    However, with the new experimental compiler switch -checkaction=context it yields:

    > dmd -checkaction=context -run main.d
    core.exception.AssertError@main.d(4): 0 != 2
    ??:? _d_assert_msg [0x4a3f9cf0]
    ??:? _Dmain [0x4a3f8fc4]

    The new switch already supports a variety of assertion messages:

    string dlang = "d2";
    assert(dlang != dlang); // ERROR: "d2" == "d2"
    struct S { int s; }
    assert(S(0) == S(1)); // ERROR: "S(0) !is S(1)"
    int a = 1, b = 2;
    assert(a > b); // ERROR: 1 <= 2

    Also if no error message can be generated, it will now fallback to displaying the text of the assert expression. For example, for this more complicated assert expression:

    void main()
        int a, b = 2;
        assert(a && (a == b));

    Compiling and running with -checkaction=context will now result in:

    > dmd -checkaction=context -run main.d
    core.exception.AssertError@main.d(4): assert(a && (a == b)) failed
    ??:? _d_assert_msg [0xb7e5fdfc]
    ??:? _Dmain [0xb7e5fd40]

    This switch for context-aware assertion error messages is still experimental and feedback is welcome.

  6. Avoid calling the struct constructor from const-casts

    In previous versions of DMD, there was an undocumented interaction of const-cast with regular cast, ie. cast(), cast(const) and cast(immutable), where these casts would be expressed as cast(const(typeof(expr))) expr; hence if expr was of type Struct, these casts could potentially call its constructor Struct(expr), as per spec.

    The dangerous part however, was if this occurred with structs that used their first field as alias this, the implicit conversion via alias this would potentially satisfy an implicit struct constructor, leaving the other fields set to init and leading to apparent data corruption from a mere cast().

    In other words, cast() s to S(s) to S(s.implicitCast).

    This can no longer occur, since cast(), cast(const) and cast(immutable) will no longer generate an implicit constructor call. Implicit constructor calls to S() will only occur when one explicitly uses cast(S).

  7. dmd now supports expressive diagnostic error messages with -verrors=context

    With the new CLI option -verrors=context dmd will now show the offending line directly in its error messages. Consider this faulty program test.d:

    void foo()
        a = 1;

    Now run it with -verrors=context:

    > dmd -verrors=context test.d
    test.d(4): Error: undefined identifier a
        a = 1;

  8. memcmp() compares are no longer performed for struct equality tests, memberwise comparisons are done instead, per the spec

    The compiler would sometimes generate code for struct equality tests using memcmp() across the whole struct object. This assumed that:

    1. alignment holes were filled with 0, which is not always the case
    2. there were no floating point NaN values, which should compare as not equal even if the bit patterns match

    The spec requires that the comparison be done in a memberwise manner. This brings the implementation in line with this.

    Equality Expressions

    This can break existing code that relied on the former erroneous behavior. To correct such code, use one of the following:

    1. define an opEquals() operator overload to achieve the desired behavior
    2. use is instead of ==, as is will do a bit compare of the struct object.

    This new behavior is enabled with the -preview=fieldwise compiler switch. It will eventually become the default behavior.

  9. OSX 32-bit is no longer supported

    With this release, the DMD compiler will no longer officially support building 32-bit applications for OSX. For legacy purposes, older releases can be used.

    Motivation: The latest macOS release Mojave is the last version of OSX with support for running 32-bit applications. The D development team wants to focus its efforts and build/test infrastructure on active and important platforms.

  10. -preview and -revert command line switches have been introduced

    Command line switches adding or subtracting features of the D language have been normally added on an ad-hoc basis. Over time this has grown to:

    • -dip25
    • -dip1000
    • -dip1000
    • -dip1008

    Moreover, in parallel -transition has been introduced and the following DMD example is only a subset of the transitional features that DMD supports at the moment:

    dmd -transition=3449 -transition=10378 -transition=14246 -transition=14888 -transition=16997

    While these transitions also have a name alias, it's still not clear for the user whether the transition is (a) an experimental feature or an upcoming breaking change, (b) a warning or help on an upcoming change, or (c) revert of a change for users who don't want to deal with the breaking change for now.

    With this release, DMD gained a -preview command line switch which can be used to test upcoming features or potentially breaking changes. For example, with this release the list of upcoming features is:

    • -preview=dip25: Implements DIP25 (Sealed references)
    • -preview=dip1000: Implements DIP1000 (Scoped Pointers)
    • -preview=dip1008: Implements DIP1008 (@nogc Throwables)
    • -preview=markdown: Enables Markdown replacements in Ddoc
    • -preview=fixAliasThis: Enables a potentially breaking fix for alias this with which DMD will first check the this scope before searching in upper scopes
    • -preview=intpromote: Enables integral promotion for the unary +, - and ~ operators
    • -preview=dtorfields: Enables a potentially breaking fix which enables to destruct fields of partially constructed objects

    Adding new features can be disruptive to existing code bases. By initially putting them behind a -preview switch users will have ample opportunity to adapt to them at their own pace.

    Therefore, for end users the new -preview interface allows a glimpse into the future. As always, feedback and bug reports for all -preview features is very welcome and encouraged, so that potential problems or breakages can be caught early.

    Whenever a -preview feature gets enabled by default, it must pass on all Continuous Integrations, pass the test suite of about 50 of the most popular D packages and be without any other known major real-world issues on Bugzilla.

    However, as the behavior of DMD could still deviate slightly from previous versions, sometimes a -revert switch might be introduced by the D development team which allows an easy opt-out of a new feature for users in case they run into issues. As of now, DMD offers these reverts:

    • -revert=dip25: Reverts DIP25 changes
    • -revert=import: Revert to single phase name lookup

    Transitioning to new features (or fixing an important bug) is very often not trivial which is why an additional -transition exists. The -transition options are informational only and intended to help gauge the problems of an upcoming change or assist debugging these changes. For example, DMD currently supports these transitions:

    • -transition=field: List all non-mutable fields which occupy an object instance
    • -transition=checkimports: Emit deprecation messages about 10378 anomalies
    • -transition=complex: Emit deprecation messages for all usages of complex or imaginary types
    • -transition=tls: List all variables going into the thread local storage
    • -transition=vmarkdown: List instances of Markdown replacements in Ddoc

    -transition command line switches might be turned into actual deprecations if the importance of a change is considered high enough (compared to the impact on real-world code), but they are only intended as information for developers on where they would be affected by a certain transition.

    As all of this information will be updated continuously with each release, all three command line switches support a help page with either h, help or ? option listing all currently available options:

    > dmd -preview=help
    > dmd -revert=help
    > dmd -transition=help

    IMPORTANT: All old command line switches will continue to work and won't be deprecated. However, they were removed from the documentation and new code is encouraged to use -preview or -revert where applicable.

  11. Transition to C++11 character types

    With C++11 comes the advent of changed character type mangling. D's default behavior will be to conform to this after a one release transition period. A new switch -extern-std={c++98,c++11} is added to control the version that compatibility is set to. This switch sets __traits(getTargetInfo, "cppStd") to the value of __cplusplus that the corresponding version of the C++ standard defines.

    Of particular note is the new difference between wchar and wchar_t on Windows. This will manifest itself as compile errors when interfacing wchar* with wchar_t* code when calling the Windows API. A cast will resolve the issue.

    Going forward we recommend using WCHAR instead of wchar or wchar_t when interfacing to Windows API functions. (WCHAR is Microsoft Windows' 16 bit character type.)

    C++ Type Equivalence

    c++98 behavior:

    D Posix DMC++ Windows VC++ Windows
    wchar unsigned short wchar_t wchar_t
    dchar wchar_t unsigned unsigned
    wchar_t wchar_t wchar_t wchar_t
    WCHAR -- wchar_t wchar_t


    D Posix DMC++ Windows VC++ Windows
    wchar char16_t wchar_t char16_t
    dchar char32_t unsigned char32_t
    wchar_t wchar_t wchar wchar_t
    WCHAR -- wchar wchar_t

    Name Mangling:

    c++98 behavior:

    D Posix DMC++ Windows VC++ Windows
    wchar t _Y _W
    dchar w I I
    wchar_t w _Y _W


    D Posix DMC++ Windows VC++ Windows
    wchar Ds _Y _S
    dchar Di I _U
    wchar_t w _Y _W

Runtime changes

  1. Added GC.profileStats() to core.memory

    Allows access to current GC profiling information. See core.memory.GC.ProfileStats for a list of profile stats.

  2. Added core.stdcpp.new_

    Added core.stdcpp.new_, which exposes interfaces for C++ global new/delete operators. This allows D programs to conveniently allocate from the C++ heap, which is useful when sharing memory between languages.

  3. Added core.sys.linux.sched.CPU_COUNT.

    Added core.sys.linux.sched.CPU_COUNT, which returns the number of CPUs in set.

  4. Added core.sys.linux.sched.CPU_ISSET.

    Added core.sys.linux.sched.CPU_ISSET, which tests to see if cpu is a member of set.

  5. Moved std.conv.emplace, std.algorithm.mutation.move, std.algorithm.mutation.moveEmplace, and std.functional.forward to core/lifetime.d

    emplace is the counterpart to destroy, so it has been moved to also live in druntime (core/lifetime.d) where it is accessible by projects that use a shallow runtime library stack. move, moveEmplace, and forward are related low-level construction machinery which also belong in core.lifetime.

  6. GC cleanup can now be configured as a DRT GC option

    The default cleanup method for the GC is to unconditionally run a collection before runtime termination to finalize objects that are still alive and hold resources that affect system state outside the current process. This combines the worst of possible alternatives: it can cause a considerable delay and does not guarantee finalization of all objects as roots might still exist.

    The cleanup behaviour can now be configured by a DRT option to the GC configuration, e.g. by passing --DRT-gcopt=cleanup:none on the command line. Three options are provided:

    • collect: run a collection (the default for backward compatibility)
    • none: do nothing
    • finalize: all live objects are finalized unconditionally

    As usual, you can also embed the configuration into the application by redefining rt_options, e.g.

    extern(C) __gshared string[] rt_options = [ "gcopt=cleanup:none" ];
  7. A garbage collector with precise heap scanning can now be selected

    Precise heap scanning can now be enabled by a DRT option to the GC configuration, e.g. by passing --DRT-gcopt=gc:precise on the command line or by redefining rt_options. See the documentation for details.

  8. GC.realloc is now more consistent and robust

    The specification of core.memory.GC.realloc has changed slightly:

    • GC.realloc now returns null for failure. (It used to return the original pointer but that is is not a good indication of failure as it might also be returned on success. It can lead to overwriting memory if an enlargement was requested.)
    • as with, the caller has to ensure that there are no other live pointers to the memory passed to GC.realloc (This used to be required only when passing a new size 0).
    • as a consequence the GC is allowed to free the memory immediately (the previous implementation did this for objects larger than 4kB when shrinking).
    • block attribute bits on the existing block are only set if it is reused (the previous implementation didn't set bits if it reused a small block).

    The implementation now properly verifies that pointers are actually base pointers to allocated GC memory (passing other pointers could have crashed immediately or corrupt the GC).

  9. User supplied garbage collectors can now be linked with the runtime

    A GC registry has been implemented that allows to add garbage collector implementations by just linking them into the binary. See the documentation for details.

  10. Added core.stdcpp.allocator

    Added core.stdcpp.allocator, which exposes the C++ std::allocator<T> class. This is a required foundation for any of the allocating STL container types.

  11. char/wchar fields in most D runtime (core.* and rt.*) structs are now zero-initialized

    Fields that are single char/wchar or fixed-length arrays of such are now initialized to all zero bits instead of all one bits for most structs in the D runtime (core.* and rt.* modules). This simplifies initialization and removes the need to store init data when it makes the entire struct zero-initialized. Most affected structs are used for interoperability with C APIs.

Dub changes

  1. dub fetch now supports <package>@<version> as a shortcut

    dub fetch <package>@<version> is a shortcut for dub fetch <package> --version=<version>:

    > dub fetch gitcompatibledubpackage@1.0.4
    Fetching gitcompatibledubpackage 1.0.4...

  2. extraDependencyFiles attribute added

    Using attribute extraDependencyFiles a list of files can be specified causing rebuild on change.

  3. File system supplier enabled

    Existing file system supplier is enabled for usage. It searches a certain directory for files with names of the form "[package name]-[version].zip".

    Example dub fetch mypackage --registry=file:///etc/dub/packages/

  4. toolchainRequirements recipe entry

    DUB now supports a new entry in dub.json or dub.sdl to restrict the versions of DUB and of compilers supported by a package.


        "toolchainRequirements": {
            "dub": "~>1.10",
            "frontend": ">=2.068 <2.083"


    toolchainRequirements dub="~>1.10" frontend=">=2.068|<2.083"

    Supported entries in toolchainRequirements are:

    • dub
    • frontend
    • dmd
    • ldc
    • gdc

    Each can contain a version specification, where DMD-like versions are supported in addition to SemVer versions. For compilers, instead of a version specification, the keyword no can also be used to indicate that the compiler should not be used for this package.

    Example scenario:
    Package that needs DUB>=1.12, and that will only build with LDC>=1.10:


        "toolchainRequirements": {
            "dub": ">=1.12",
            "dmd": "no",
            "gdc": "no",
            "ldc": ">=1.10"


    toolchainRequirements dub=">=1.12" dmd="no" gdc="no" ldc=">=1.10"

List of all bug fixes and enhancements in D 2.085.0:

DMD Compiler regressions

  1. Bugzilla 16214: [REG2.069] ICE: Assertion `fd->semanticRun == PASSsemantic3done' failed.
  2. Bugzilla 16652: [Reg 2.071] returned rvalue destroyed too early
  3. Bugzilla 17518: [Reg 2.063] confusing error message with inout constructor/ctor
  4. Bugzilla 18372: REG(2.072): error missing line number: Error: undefined identifier __va_list_tag
  5. Bugzilla 19494: [REG 2.080.0][objc] interface main.NSObject.Class conflicts with interface main.NSObject.Class
  6. Bugzilla 19499: __c_long_double has exact match with double
  7. Bugzilla 19523: "undefined identifier" causes DMD crash
  8. Bugzilla 19618: Incorrect conversion of function returning typeof(null) to function returning an associative array
  9. Bugzilla 19639: Initializing static array with slice enum of different length crashes the compiler
  10. Bugzilla 19652: [REG2.084] alias this chain no longer works
  11. Bugzilla 19654: [REG master] cannot have final methods in objc interfaces
  12. Bugzilla 19672: Function uses the stack to read a static array parameter but it is passed in the registers
  13. Bugzilla 19685: Nested aggregate overlaps not detected

DMD Compiler bugs

  1. Bugzilla 12001: __traits(isSame) does not work with the basic types
  2. Bugzilla 16098: align(32) not respected for stack variables
  3. Bugzilla 17090: dmd -transition=? needs quoting => make it -transition=help
  4. Bugzilla 17181: Local imports in templates should be added to imported modules list of module that instantiated it
  5. Bugzilla 18545: Casting away const with cast() triggers alias this, but returns the supertype anyway
  6. Bugzilla 19223: core.simd __vector.array compiler crash
  7. Bugzilla 19224: core.simd __vector.array "__r2.length cannot be evaluated at compile time"
  8. Bugzilla 19574: DMD crashes with templated structs in two identical extern(C++, "") blocks
  9. Bugzilla 19608: [ICE] dmd/backend/cod1.d(3826): Assertion `0' failed.
  10. Bugzilla 19609: [ICE] dmd/expression.d(2790): Segmentation fault
  11. Bugzilla 19627: [CTFE][SIMD] Error: cannot cast int to int[4]
  12. Bugzilla 19628: [CTFE][SIMD] ICE indexing vector array
  13. Bugzilla 19630: [CTFE][SIMD] Error: cannot determine length of vector slice at compile time
  14. Bugzilla 19676: Destructor not called for returned temporary that was cast to void
  15. Bugzilla 19687: Wrong error for overloaded opDispatch + UFCS with non-existing function
  16. Bugzilla 19699: [2.085.0-beta.2] Obj-C segfault - in objc_glue.getClassName

DMD Compiler enhancements

  1. Bugzilla 16360: DMD fails to inline functions that contain a type
  2. Bugzilla 19097: Extend Return Scope Semantics
  3. Bugzilla 19552: -transition is non-intuitive to use - the flag should list options by default

Phobos bugs

  1. Bugzilla 18519: freebsd 11 + phobos + curl, timing out
  2. Bugzilla 18913: Cannot move static array of non-copyable type
  3. Bugzilla 19532: chunkBy assert error involving non-forward input ranges.
  4. Bugzilla 19572: std.array.Appender.put invokes struct constructor via cast
  5. Bugzilla 19580: [non-DMD] std.random seed bootstrap: don't count on reading an uninitialized variable being treated as an ordinary read
  6. Bugzilla 19644: std.range.takeOne opSlice asserts incorrectly when operating on non-forward input range
  7. Bugzilla 19647: std.range.takeOne opSlice incorrect for empty slice of non-forward input range

Phobos enhancements

  1. Bugzilla 19453: Remove unnecessary error checks in std.datetime.systime.currStdTime()
  2. Bugzilla 19526: make std.typecons.RefCounted work in betterC

Druntime bugs

  1. Bugzilla 11393: [GC] GC realloc and free don't ignore interior pointers
  2. Bugzilla 11446: [GC] GC realloc doesn't ignore non-GC owned pointers
  3. Bugzilla 12843: Unit tests fail when GC is compiled with SENTINEL
  4. Bugzilla 15393: Debug versions in GC code doesn't compile.
  5. Bugzilla 17431: GCBits should be @nogc to prevent deadlocks
  6. Bugzilla 19281: GC mishandles allocations >= 4GB
  7. Bugzilla 19522: [GC] GC.query/addrOf/sizeOf fail for freed memory
  8. Bugzilla 19562: core.internal.hash.hashOf array of pointers or delegates should be @safe
  9. Bugzilla 19568: hashOf should not unnecessarily call a struct's fields' postblits & dtors in CTFE
  10. Bugzilla 19571: Incorrect definition of DTM_FIRST in
  11. Bugzilla 19582: Make core.internal.convert.toUbyte in CTFE for arrays work with reference type elements and not call postblits/dtors
  12. Bugzilla 19593: dstrcmp with -profile causes stack overflow

Druntime enhancements

  1. Bugzilla 16377: Make --DRT GC profile information available outside of GC destruction
  2. Bugzilla 19128: argument to alloca may be too large
  3. Bugzilla 19455: GC wastes too much memory
  4. Bugzilla 19524: Make core.checkedint work in betterC bugs

  1. Bugzilla 19592: Rule for IdentifierList is wrong

Contributors to this release (48)

A huge thanks goes to all the awesome people who made this release possible.

previous version: 2.084.1 – next version: 2.085.1