Does log_message() log the line number?

The CI_Exceptions class is called by the function which CI registers as the exception-handler to log and (if enabled) display the exception. Since it is registered with PHP's native exception-handling mechanism, CI's exception-handler expects any exception thrown by your application to use (or extend) the native PHP Exception class.

So, CI_Exceptions is not an Exception (or an extension of Exception), it is simply a collection of methods which handle errors and exceptions, and a property which defines the error/warning levels used by CI.

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide