how to catch D Throwables (or exceptions) from C++?

[Timothee Cour via Digitalmars-d-learn]

eg:

```
dlib.d:
extern(C) void dfun(){assert(0, "some_msg");}

clib.cpp:
extern "C" void dfun();
void fun(){
  try{
    dfun();
  }
  catch(...){
    // works but how do i get "some_msg" thrown from D?
  }
}
```