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Re: [PATCH 3/4] libstdc++: avoid character accumulation in istreambuf_iterator


On Wed, 15 Nov 2017 22:31:11 +0100
Paolo Carlini <paolo.carlini@oracle.com> wrote:

> Hi,
> 
> On 15/11/2017 11:48, Petr Ovtchenkov wrote:
> > Ask associated streambuf for character when needed instead of
> > accumulate it in istreambuf_iterator object.
> >
> > Benefits from this:
> >    - minus one class member in istreambuf_iterator
> >    - trivial synchronization of states of istreambuf_iterator
> >      and associated streambuf
> > ---
> >   libstdc++-v3/include/bits/streambuf_iterator.h | 34 ++++++++++++--------------
> >   1 file changed, 15 insertions(+), 19 deletions(-)
> >
> > diff --git a/libstdc++-v3/include/bits/streambuf_iterator.h
> > b/libstdc++-v3/include/bits/streambuf_iterator.h index 08fb13b..203da9d 100644
> > --- a/libstdc++-v3/include/bits/streambuf_iterator.h
> > +++ b/libstdc++-v3/include/bits/streambuf_iterator.h
> > @@ -95,19 +95,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >         // NB: This implementation assumes the "end of stream" value
> >         // is EOF, or -1.
> >         mutable streambuf_type*	_M_sbuf;
> > -      mutable int_type		_M_c;
> Obviously this would be an ABI-breaking change, which certainly we don't 
> want. Unless I missed a detailed discussion of the non-trivial way to 
> avoid it in one of the recent threads about these topics...

Is we really worry about frozen sizeof of instantiated template?
(Removed private template member).

If yes, than

   int_type __dummy;

is our all.

> 
> Paolo.

--

   - ptr


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