Exception/Error division in D

[deadalnix]

Le 01/06/2012 22:35, Walter Bright a écrit :
> On 6/1/2012 11:14 AM, deadalnix wrote:
>> We are talking about runing scope statement and finally when unwiding
>> the stack,
>> not trying to continue the execution of the program.
>
> Which will be running arbitrary code not anticipated by the assert
> failure, and code that is highly unlikely to be desirable for shutdown.
>
>> This is, most of the time, the point of error/exceptions. You rarely
>> recover
>> from them in real life.
>
> I believe this is a misunderstanding of what exceptions are for. "File
> not found" exceptions, and other errors detected in inputs, are routine
> and routinely recoverable.
>
> This discussion has come up repeatedly in the last 30 years. It's root
> is always the same - conflating handling of input errors, and handling
> of bugs in the logic of the program.
>
> The two are COMPLETELY different and dealing with them follow completely
> different philosophies, goals, and strategies.
>
> Input errors are not bugs, and vice versa. There is no overlap.

I'm pretty sure I understand what you are saying here. We have in fact 3 
cases :
1/ A problem during the execution of an operation (Exceptions).
2/ A logical invalid state in the program (Errors).
3/ The program environment is broken (Error too ATM).

Case 1/ is out of the current discussion scope. In case 3/, it doesn't 
even make sense to throw an Error as we do know, because it isn't even 
sure that this is possible (stack corrupted), or that the information 
provided are correct.

This leave the case 2/ on the table.

Programs are usually an aggregate of several smaller component that 
interacts with each others. Let say, as this is a very common case, I 
have a program that have a network component and another that perform 
some calculations.

If an assert fails in the component that does calculations, it indicate 
a malfunction here. Whatever I do in that module, it is likely that it 
will make no sense. However, unless I consider I may be in case 3/ (but 
then, it isn't even a good response to throw an Error, so we consider we 
aren't) I'm sure that the network module is still in good shape and can 
close the connection.