Error handling

XTI attempts to separate communications errors from system errors by defining two levels of errors:

• Library level errors. Each library function has one or more error returns and indicates failure with a -1. An external integer, t_errno, holds the specific error number when such an failure occurs. This value is set when errors occur but is not cleared by successful library calls. It should therefore be tested only after an error has been indicated. A diagnostic function, t_error, is provided for printing out information on the current transport error.

• System errors. The standard external variable errno, is used to report system errors. Such errors can, of course, affect XTI functioning. When they do, t_errno is set to TSYSERR and errno is set to show the specific system error that occurred. The state of the transport provider may change if a transport error occurs.

The socket interface provides a similar facility with getsockopt when called with an option of SO_ERROR.