Testing exceptions with BOOST

Question

I'm using boost test framework 1.47 and I'm having difficulties testing my exceptions

Here is my exception class

class VideoCaptureException : public std::exception
{

    std::string m_Description;
public:
    VideoCaptureException(const char* description)
    {
        m_Description = std::string(description);
    }
    VideoCaptureException(const std::string& description)
    {
        m_Description = description;
    }
    virtual ~VideoCaptureException() throw() {}
    virtual const char* what() const throw()
    {
        return m_Description.c_str();
    }
}

I'm trying to test code that simply throws this exception

BOOST_CHECK_THROW( source.StopCapture(), VideoCaptureException )

For some reason it doesn't work.

unknown location(0): fatal error in "testVideoCaptureSource": unknown type
testVideoCaptureSource.cpp(28): last checkpoint

What is it that I'm doing wrong?

Answer 1

After encountering this error myself, I have tracked it down to a silly, but easy-to-make mistake:

throw new VideoCaptureException( "uh-oh" );

will fail with that error message, while:

throw VideoCaptureException( "uh-oh" );

will succeed.

---

The new variant causes a pointer to an exception to be caught, rather than the exception itself. The boost library doesn't know what to do with this, so it just says "unknown type".

It would be nice if the library explained the situation properly, but hopefully anybody else hitting "fatal error: unknown type" will find this page and see how to fix it!