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

From: William E. Kempf (wekempf_at_[hidden])
Date: 2003-01-14 06:18:01

David Abrahams said:
> "William E. Kempf" <wekempf_at_[hidden]> writes:
>
>> 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.
>
> Remember that it's a bad idea to carry dynamically-allocated state in an
> exception object.  Translating to readable strings at the throw point is
> ill-advised.

Agreed, but that's an implementation detail.  IOW, the exception should
carry the error code, but what purpose is there in having the interface
expose this detail?

BTW:  The filesystem_error carries a lot of dynamically-allocated state
(as in 1/2 of the member data is, at least potentially, allocated).

William E. Kempf
wekempf_at_[hidden]