Using QtConcurrent::Exception with boost::exception



  • I want to use an exception hierarchy where the base exception class derives from boost::exception so that I can get the nice and useful diagnostic information that that class has to offer and QtConcurrent::Exception so that I can throw my exceptions across threads.

    Hence, my base exception class looks like:

    @class MyException : public QtConcurrent::Exception, public boost::exception
    {
    public:
    MyException() { };
    virtual ~MyException() throw() { }

    // required by QtConcurrent::Exception to be implemented
    virtual void raise() const { throw *this; }
    virtual MyException* clone() const { return new MyException(*this); }
    

    };@

    Per QtConcurrent::Exception's documentation, raise() and clone() must be implemented in any class derived from QtConcurrent::Exception. So, the rest of my code may look something like:

    @void foo()
    {
    BOOST_THROW_EXCEPTION(MyException());
    }

    int main(int argc, char *argv[])
    {
    QApplication app(argc, argv);

    try
    {
        foo();
    }
    catch (const MyException& me)
    {
        std::cerr << boost::diagnostic_information(me);
    }
    
    return 0;
    

    }@

    However, using the BOOST_THROW_EXCEPTION() macro causes the following compilation error:

    bq. error C2555: 'boost::exception_detail::clone_impl::clone': overriding virtual function return type differs and is not covariant from 'MyException::clone'

    I am not entirely sure what this error is telling me (my fault, not the errors, I'm sure!).

    If I instead use throw MyException(); the code compiles just fine. As I mentioned above, I'd like to use BOOST_THROW_EXCEPTION() so that I get the diagnostic information in my exceptions.

    I know that one possible work-around could be another class derived from just QtConcurrent::Exception that has a boost::exception member, essentially a container for the actual error. But if possible, I would like to continue to have the MyException class inherit from both QtConcurrent::Exception and boost::exception.

    Can someone offer some insight into what the error is saying? Is there any way to accomplish what I want?


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