Visual C++ Compiler Error C2316

You know, I was getting this error when porting some exception catching code from Visual C++ 6 to version 9. The error message helpfully states that 'exception' cannot be caught as the destructor and/or copy constructor are inaccessible

Weird thing was, it was wrong. Both the copy constructor and destructor for the class and all it’s ancestors were in public scope.

Eventually there was the figuring out: the exception was being anonymously caught, like so:
try {
whatever();
}
catch (MyExceptionClass&) {}
And to keep MSVC6 happy, earlier in the codebase a preceding programmer had coded:
class MyExceptionClass;
Which did indeed keep MSVC6 happy. MSVC9 asked what I’d done with the copy constructor. Well, dear friend: it’s in the header file that wasn’t included. Delete the forward declaration, add one #include and we are cooking with gas.

If we actually give the compiler the definition of the class being caught it can generate code rather than misleading error messages. Why the error message wasn’t: “No definition for this class” is beyond me.