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Re: [PATCH 3/4] libstdc++: avoid character accumulation in istreambuf_iterator
On Thu, 16 Nov 2017 12:29:37 +0100
Paolo Carlini <paolo.carlini@oracle.com> wrote:
> Hi,
>
> On 16/11/2017 12:03, Petr Ovtchenkov wrote:
> > On Thu, 16 Nov 2017 10:39:02 +0100
> > Paolo Carlini <paolo.carlini@oracle.com> wrote:
> >
> >> Hi,
> >>
> >> On 16/11/2017 06:31, Petr Ovtchenkov wrote:
> >>> Is we really worry about frozen sizeof of instantiated template?
> >> Yes we do. See https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html
> >> under "Prohibited Changes", point 8.
> >>
> >> Of course removing the buffering has performance implications too -
> >> that's why it's there in the first place!
> > "buffering" here is a secondary buffering (after streambuf).
> > No relation to performance, but place for incoherence with
> > state of attached streambuf.
> It depends, we may be dealing with an unbuffered stream. For sure at the
> time we measured a performance impact in some cases, likewise whoever
> implemented it in the first place (not me) otherwise, again, why bothering?
This part of code is from SGI, so I suspect that nobody here really
measure performance difference between "bufferred" and "non-buffered"
implementations. Just because we have only implementation
with _M_c in isreambuf_iterator.
>
> Paolo.
>
--
- ptr