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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-08-25 07:46:20

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. ;-)