[RFC] err |= ios_base::failbit or err = ios_base::failbit?!?

[Paolo Carlini]

Nathan Myers wrote:

> On Mon, Jan 05, 2004 at 03:42:05PM +0100, Paolo Carlini wrote:
>
>> the standard, in 22.2.2.1.2, p11-12, always talks about:
>>
>> "... ios_base::failbit is assigned to err."
>>
>> On the other hand, we have been always doing:
>>
>> err |= ios_base::failbit.
>> ...
>> Again, I'm not at all sure that the standard prescribes this.
>
> If, in every case where it prescribes assigning failbit, that point
> could not be reached unless the error state was already clear, then
> they are equivalent. I suspect that was the reasoning in committee.
> Have you found a case where the code can set failbit but the error
> state was not zero? (I.e., maybe our use of operator|= is merely
> defensive coding.)

Well this is the sequence of calls:

  get -> do_get -> _M_extract_int(float)

the latter contains the |= and nothing in the middle in our implementation,
(neither in 22.2.2.1.2) changes the err passed by get.

Therefore, it looks like we have *plenty* of cases!!!

Paolo.