[Alephmodular-devel] On errors

[Br'fin <br...@ma...>]

In general, I like the design I put forth for IFailable. It's intent 
was not to cover an object handled by several threads at once.

The area I'm having problem is with with CError objects. As I work on 
it, I'm going lets add this and lets add that. And consequently it 
seems to be lacking a proper elegance to it.


Marathon handles errors like so:

The game hits an error and calls set_game_error(type, code)

Type may be a gameError or a systemError. If it's a gameError, than 
code is limited to a particular subset of codes. If it's a systemError, 
than the particular error is recorded in the code.

Code higher up the hierarchy can check if the game has an 
error_pending, it can read what kind of error is around with get_error 
and can clear the error.


For instance, file finding code might report (systemError, 
fileNotFound) Further up the code sees this and says: Error pending? 
Ok, what is it? File not found? Ok, it's just the preferences, clear 
the error and continue on to create the file.


For a contrasting viewpoint on errors, I looked at Java. That has the 
hierarchy of 'Throwable' leading to 'Exception' (things which your 
program should catch) and 'Error' (Things which your program shouldn't 
catch, they're just too big). And then further breakdowns of errors.

In our case this would work out to one SystemException and then 
GameException with a hierarchy of specific exceptions beneath it.


Another thing about Java exceptions is that the interface is fairly 
simple, You create a new exception and the string argument in the 
creator is optional.


Hsm, was just thinking about exceptions and C++. Exceptions get to be a 
nuisance if the current function itself is just a pass through for an 
exception. (open_preferences would continue to throw a 
fileNotFoundException that originated in open_file and also had to 
propagate through wad_open.) Or do you just need to pussyfoot around 
your declarations to make sure that if you're passing an exception that 
you didn't declare any memory before the point where the exception can 
occur?

-Jeremy Parsons