Re: Exceptions vs Error return values

[Ted Dennison<dennison@telepath.com>]

In article <uzo9dgxtf.fsf@gsfc.nasa.gov>, Stephen Leake says...
>
>hfrumblefoot@yahoo.com (Hambut) writes:
>
>> The 'thin' binding provides a lot of functions returning an integer.
>> The value of this integer encodes a whole range of possible errors.
>> I want to replace this 'C'-esque way of doing stuff with Ada
>> exceptions; my question is "What is a sensible guideline for
>> choosing between exceptions and error return codes?"
>
>I always raise an exception whenever the function cannot do what the
>caller expected.
>
>On the other hand, I don't define a different exception for every
>error. There are two mechanisms to encode different errors; either use
>Ada.Exceptions.Raise_Exception with a message string, or provide a
>function that returns an error code. In the case of Windows stuff,
>raising Windows_Error, and allowing the user to get the Windows error
>code, is sufficient.


If there is another call that can be made to get the exact error code, I'd
usually just provide a binding to that. Otherwise, I'm with Steven in that I
don't like to create tons of different exceptions. I ususally just create one
named "Error" (eg: Sockets.Error). I also used to tack any extra info onto the
exception message. The problem I found with doing that is that there are often
arbitrary limits on the maximum length of that message. What I prefer to do
these days is define an error message string (as Ada.Strings.Unbounded), and
provide that to the user.

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