Rob Stewart wrote:

From: "Reece Dunn" <msclrhd@hotmail.com>

...

What about when you use boost::policy::errormsg_storage instead of boost::policy::no_errormsg_storage? Doing this allows the following:

typedef boost::errorcheck< boost::policy::error_storage<>, boost::policy::errormsg_storage > errorcheckmsg;

try { errorcheckmsg em; em( "oops!" ) = -3; // note the special syntax } catch( errorcheckmsg em ) { std::cout << "error: " << em.get_msg() << '\n'; }

resulting in "error: oops!" being outputted. Using your method, the message string will ont be passed and thus you would get "error: unspecified error"! That is why I implemented it as above.

I didn't see anything like that in the code you showed. It was probably in the full implementation, but I was only looking at what's quoted above.

I posted it as a different message (errorcheck) and have been revising it based on comments and suggestions. The full code is attached here.

Anyway, why must either constructor manage the string at this point? Why wouldn't the generation of the string occur at the time it is requested? That is, there is no string to copy if there is no string generated until the get_msg() mf is called. That mf can create the string (reusing it if already computed, of course).

It depends on what you are using it for. The string for the errno handler *is* generated at get_msg() call-time. The above is based on an example Volodya posted where he put the name of the function he was calling into the code. E.g. // [paraphrased]: if( ::read( fn, ... ) < 0 ) report_error( "read", errno ); becomes ec( "read" ) = ::read( fn, ... ); As another example, you could have a handler that supports windows GetLastError and do something like: try { winerr( "Rectangle" ) = ::Rectangle( hDC, 10, 10, 110, 110 ); winerr( "Ellipse" ) = ::Ellipse( hDC, 10, 10, 110, 110 ); } catch( winapi_errorcheck e ) { std::cout << "error: " << e.get_msg() << " - " << e.error_string() << '\n'; } NOTE: I know that mixing GUI/console does not work -- this is just a usage demonstration.

If you find your approach is still needed, no problem. I just wanted to be sure you understood what I had implied.

No worries. I understood your approach, but I was designing it to be as flexible as possible. Regards, Reece _________________________________________________________________ It's fast, it's easy and it's free. Get MSN Messenger today! http://www.msn.co.uk/messenger