[Boost-users] Re: Guidelines for effective exception usage

From: David Abrahams (dave_at_[hidden])
Date: 2004-08-25 11:17:54

"Peter Dimov" <pdimov_at_[hidden]> writes:

> Ben Hutchings wrote:
>> Peter Dimov <pdimov_at_[hidden]> wrote:
>>> Ben Hutchings wrote:
>>>> Peter Dimov <pdimov_at_[hidden]> wrote:
>>>>> Victor A. Wagner Jr. wrote:
>>>>>>
>>>>>> OK, blunt point.
>>>>>> the standard is (insert favorite expletive or "in error") if it
>>>>>> allows use of std::runtime_error to terminate the program due to
>>>>>> low memory situations (run out of memory (due to copying) during
>>>>>> stack unwinding).
>>>>>
>>>>> It does not allow such a thing.
>>>>
>>>> This is an known and unresolved issue:
>>>> http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#254
>>>
>>> "The copy constructors of all exception-derived classes already have
>>> a no throw spec. Reference 18.6.1, 19.1 and 15.4/13."
>>
>> "As they stand, the copy constructors might fail via a call to
>> unexpected. I think what is intended here is that the copy
>> constructors can't fail."
>>
>> (Is it really necessary for us to quote the referenced text at each
>> other?  This is silly.)
>
> Yep. The difference is that the excerpts I quote are correct. ;-)
>
> Whenever throw() is used in the standard, it is intended to mean "the
> function does not throw", not "the function may arbitrarily call
> unexpected() and abort the program."
>
> Of course we all know that throw() actually means the latter, which
> makes it rather useless as both a documentation tool and a static
> nothrow checker tool; nevertheless, in the standard signatures, it is
> supposed to mean the former. Or so Dave says, and he wrote that
> portion, so he must know. ;-) 

Actually I didn't write that portion, but Peter's right about
everything else.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com