WeakRef updated to better support Tango -- and a question

[Jason House]

I'm getting:
  undefined reference to `rt_attachDisposeEvent'
  undefined reference to `rt_detachDisposeEvent'

What can I do to fix that?  I must admit that I didn't use the code as is, but
instead mutated it for my own purposes...  Essentially, I have an AA-like object
that needs to remove the AA entry instead of invalidating a pointer.

Here's the code I used for the function prototypes:
private{
	alias void delegate(Object) DisposeEvent;
	extern(C) void rt_attachDisposeEvent(Object obj, DisposeEvent event);
	extern(C) void rt_detachDisposeEvent(Object obj, DisposeEvent event);
}

== Quote from Bill Baxter (dnewsgroup at billbaxter.com)'s article
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> The unittest in the previous version didn't actually work under Tango...
> oops.  This version also eliminates the string alias and puts imports
> for unittests inside version(UnitTest) {...}
> Also I realized Myron Alexander had made a weak ref class a while back
> called WeakObjectReference, and posted under D.announce.  The main
> difference seems to be that his version uses malloc to allocate one
> pointer, whereas I just use a size_t to hold the pointer so that the GC
> won't see it.  Is there some reason why that won't cut it?
> Still hoping someone will let me add this to scrapple and/or
> tango.scrapple.  Hint hint.
> --bb
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>  name="weakref.d"
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> Content-Disposition: inline;
>  filename="weakref.d"
> /*==========================================================================
>  * weakref.d
>  *    Written in the D Programming Language (http://www.digitalmars.com/d)
>  */
> /***************************************************************************
>  * Creates a weak reference to a class instance.
>  *
>  * A weak reference lets you hold onto a pointer to an object without
>  * preventing the garbage collector from collecting it.
>  * If the garbage collector collects the object then the weak pointer will
>  * become 'null'.  Thus one should always check a weak pointer for null
>  * before doing anything that depends upon it having a value.
>  *
>  * Tested with:
>  *    DMD 1.025 / Phobos 1.025
>  *    DMD 1.025 / Tango 0.99.4
>  *
>  * Usage example:
> ---
>  class Something {}
>  auto a = new Something();
>  auto wa = new WeakRef!(Something)(a);
>  std.gc.fullCollect();
>  // Reference 'a' prevents collection so wa.ptr is non-null
>  assert(wa.ptr is a);
>  delete a;
>  // 'a' is gone now, so wa.ptr magically becomes null
>  assert(wa.ptr is null);
> ---
>  *
>  *
>  * Author:  William V. Baxter III
>  * Contributors:
>  * Date: 21 Jan 2008
>  * Copyright: (C) 2008  William Baxter
>  * License: Public Domain where allowed by law, ZLIB/PNG otherwise.
>  */
> //===========================================================================
> module weakref;
> version(Tango) {
>     private {
>         alias void delegate(Object) DisposeEvt;
>         extern (C) void  rt_attachDisposeEvent( Object obj, DisposeEvt evt );
>         extern (C) void  rt_detachDisposeEvent( Object obj, DisposeEvt evt );
>     }
> }
> class WeakRef(T : Object) {
> private:
>     size_t cast_ptr_;
>     void unhook(Object o) {
>         debug { writefln("Unhook! [%s]",o); }
>         if (cast(size_t)cast(void*)o == cast_ptr_) {
>             version(Tango) {
>                 rt_detachDisposeEvent(o, &unhook);
>             } else {
>                 o.notifyUnRegister(&unhook);
>             }
>             cast_ptr_ = 0;
>         }
>     }
> public:
>     this(T tptr) {
>         cast_ptr_ = cast(size_t)cast(void*)tptr;
>         version(Tango) {
>             rt_attachDisposeEvent(tptr, &unhook);
>         } else {
>             tptr.notifyRegister(&unhook);
>         }
>     }
>     ~this() {
>         T p = ptr();
>         if (p) {
>             version(Tango) {
>                 rt_detachDisposeEvent(p, &unhook);
>             } else {
>                 p.notifyUnRegister(&unhook);
>             }
>         }
>     }
>     T ptr() {
>         return cast(T)cast(void*)cast_ptr_;
>     }
>     WeakRef dup() {
>         return new WeakRef(ptr());
>     }
> }
> version(UnitTest) {
> version(Tango) {
>     import tango.core.Memory;
>     alias GC.collect collect;
> } else {
>     static import std.gc;
>     alias std.gc.fullCollect collect;
> }
> unittest {
>     class Something {
>         int value;
>         this(int v) { value = v; }
>         ~this() { value = -1; }
>     }
>     WeakRef!(Something) wa;
>     auto a = new Something(1);
>     wa = new WeakRef!(Something)(a);
>     assert(a is wa.ptr);
>     collect();
>     assert(a is wa.ptr);
>     delete a;
>     // a now gone so should be collected
>     collect();
>     assert(wa.ptr is null);
> }
> }
> //--- Emacs setup ---
> // Local Variables:
> // c-basic-offset: 4
> // indent-tabs-mode: nil
> // End:
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