2009/3/22 liyu <yunw...@msn.com>: > I am not sure it's a bug of tango or dmd, so i post it here. The example > code as below > > ... > > The result is: > Library successfully loaded > Symbol dllprint found. Address = 0x1000308c > mydll.DummyC > mydll.DummyC > tango.core.exception.assertexcept...@test(35): Assertion failure > > As you see, var a is a instance of DummyC which is a subclass of DummyB, but > the cast is failure.
This is, unfortunately, a limitation imposed by Windows DLLs. DLLs cannot, by their nature, load symbols out of the host application that loads them. As a result, the typeinfo of classes is duplicated, one copy in the host and one in each DLL. Thus you end up with classes which _look_ the same, but casting them will inevitably fail. There is no real robust solution while still using DLLs, and the problem only exists on Windows. DDL attempts (and succeeds, quite nicely) in performing manual dynamic linking. http://www.dsource.org/projects/ddl
