Question

I want to derive a stringstream so that I can use the operator<< to construct a message which will then be thrown. The API would look like:

error("some text") << " more text " << 42 << std::endl;

This should do a

throw "some text more text 42"

So what I did is make an errorbuf (inheriting from streambuf) which overloads the ‘overflow’ method and then create an ostream(&errorbuf). I wonder if I shouldn’t instead inherit from basic_ostringstream or something…

Answer 1

I’ll trot out my favourite macro again here:

#define ATHROW( msg )                                               \
{                                                                   \
    std::ostringstream os;                                          \
    os << msg;                                                      \
    throw ALib::Exception( os.str(), __LINE__, __FILE__ );          \
}                                                                   \

In use:

ATHROW( "Invalid value: " << x << " should be " << 42 );

the exception type is from my own library, but I think you get the idea. This is much simpler than deriving your own stream class, and avoids lots of nasty complications with op<<().