Linker Errors when Constructing an Immutable Struct

Jonathan M Davis via Digitalmars-d digitalmars-d at puremagic.com
Mon Jun 2 00:42:07 PDT 2014


On Mon, 02 Jun 2014 00:13:32 -0700
Adam Wilson via Digitalmars-d <digitalmars-d at puremagic.com> wrote:

> Please consider the following code:
>
> module aurora.immediate.input;
>
> public enum Key : int { //... }
>
> public immutable struct KeyData
> {
>   private Key _key;
>   @property public Key KeyCode() { return _key; }
>
>   private bool _isDown;
>   @property public bool IsDown() { return _isDown; }
>
>   private bool _isUp;
>   @property public bool IsUp() { return _isUp; }
>
>   private bool _isRepeating;
>   @property public bool IsRepeating() { return _isRepeating; }
>
>   @disable this();
>
>   public immutable this(Key key, bool isDown, bool isUp, bool
> isRepeating = false) nothrow
>   {
>       _key = key;
>       _isDown = isDown;
>       _isUp = isUp;
>       _isRepeating = isRepeating;
>   }
> }
>
> module aurora.immediate.window;
> import aurora.immediate.input;
>
> public class Window {
> protected void delegate(immutable(KeyData) args) nothrow onKeyDown;
> private LRESULT internalWndProc(HWND hwnd, UINT message, WPARAM
> wParam, LPARAM lParam) nothrow {
>   if (onKeyDown !is null) onKeyDown(immutable
> KeyData(cast(Key)wParam, true, false, false));
>   return 0;
> }
> }
>
> When compiled and imported as a static library it fails to compile
> with the following linker errors:
> libaurora_immediate64d.lib(window_47a_278.obj) : error LNK2019:
> unresolved external symbol _D6aurora9immediate5input7KeyData6__initZ
> referenced in function
> _D6aurora9immediate6window6Window15internalWndProcMFNbPvkmlZl
> libaurora_immediate64d.lib(window_47a_278.obj) : error LNK2019:
> unresolved external symbol
> _D6aurora9immediate5input7KeyData6__ctorMyFNbNcE6aurora9immediate5input3KeybbbZyS6aurora9immediate5input7KeyData
> referenced in function
> _D6aurora9immediate6window6Window15internalWndProcMFNbPvkmlZl
>
> It appears that the linker cannot find .init and the .ctor. Is this
> a compiler bug or am I doing something wrong? I am wondering if this
> is a problem with immutable structs? Any pointers would be very
> appreciated.
>

It's probably a bug, though I'd point out that all it means when you mark a
struct declaration as immutable is that you've marked all of its members as
immutable (meaning that marking the constructor as immutable is redundant).
Also, if all of the member variables are immutable, there really isn't much
point in declaring getters. You might as well just make them public.
Regardless, I don't know why you'd be getting the errors that you're getting.
You could try just marking all of the members as immutable directly and
removing the getters and seeing if that magically fixes things for you (though
it probably won't). It does sound like a compiler bug though.

- Jonathan M Davis


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