linker: undefined symbol when an interface is derived from.
kb3ctd2 at yahoo.com
Mon Feb 26 20:35:58 PST 2007
"Neal Alexander" <wqeqweuqy at hotmail.com> wrote in message
news:es053h$19iq$1 at digitalmars.com...
> Yea, file2 is some other code that isn't hugely relevant.
Well, the error is referring to file2.d, so my guess is that the problem is
there. Would help if I knew what was in it.
> Anyway, I tried compiling d3d8.d in with it, but it gives 'multiple
> defined' type errors during the parsing stage since the module is imported
> i guess (cant build without the type definitions in it).
This is because you've named the file d3d8.d, but the module statement at
the top says "module directx". If you put different things for the filename
and for the module declaration, weird things result, so that should read
"module d3d8" instead.
> d3d8.d is just a "header" anyway it shouldn't need to be explicitly
> compiled right? Also, i don't understand why an interface definition
> produces a symbol in the binary haha.
I think you do need to compile it, because even though IDirect3D8 is just an
interface, it's a different kind of interface, a COM interface. COM
interfaces don't work quite the same way as D interfaces. When you derive a
D class from a COM interface, D seems to create a "shim" interface so that
the class can implement the interface, and that shim is what's actually
being inserted into the symbol table, and is what D needs.
In fact, I just worked up a simple example just now, and this seems to be
exactly what's happening:
class Foo : ComObject, IFoo
interface IFoo : IUnknown
Now, when I compile with the command line
I get the error
Error 42: Symbol Undefined _D7comtest4IFoo11__InterfaceZ
Hm. So I compile with
dmd dtest.d comtest.d
and it compiles fine.
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