Re: [boost] Re: Next revision of boost::thread & OS error code.

From: Greg Colvin (Gregory.Colvin_at_[hidden])
Date: 2003-01-13 15:56:36

At 03:11 AM 1/14/2003, William E. Kempf wrote:

>Stefano Delli Ponti said:
>> From: "William E. Kempf" <wekempf_at_[hidden]>
>>> David Abrahams said:
>>> > "William E. Kempf" <wekempf_at_[hidden]> writes:
>>> >
>>> >>> People said they wanted it, and the cost is low (one int). I think
>>> Greg is  right that they wanted to attempt system-dependent
>>> recovery.
>>> >>
>>> >> Well, I can agree that the cost is low... so I won't argue too much
>>> about including it.  I just want to feel comfortable with the
>>> rationale.
>>> >
>>> > I think a rationale goes like this:
>>> >
>>> > suppose the platform gives you a function for converting an error
>>> code into an error message (realistic, I think).  How much code do
>>> you have to write in order to take advantage of it?
>>>
>>> Contrasted with, "If a platform has the ability, the error is
>>> translated into a message that's returned as part of what()."  That's
>>> where I feel uncomfortable with the reationale.
>>
>> The rationale may include the possibility, in certain circumstances, to
>> catch a single root exception with a way to discern and react to the
>> effecive os error (without the need for string comparisons).
>
>If the exception type doesn't fold multiple errors into a single unit,
>there's no need for the error code in this situation.  RTTI will provide
>the same capabilities, even if you don't want to have seperate catch
>clauses.

Yes, but that assumes a different exception class for
every error code, including codes on systems that we
may not have thought about yet, or have not even been
invented yet.  So an optional system-defined code of
a system-defined type seems like a good insurance
policy.