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Re: [PATCH] libstdc++: istreambuf_iterator proxy
On Sun, 8 Oct 2017 16:59:39 +0200
François Dumont <frs.dumont@gmail.com> wrote:
> ...
> >>> We have three issues with istreambuf_iterator:
> >>> - debug-dependent behaviour
> >> Fixed.
> > + __glibcxx_requires_cond(_M_sbuf,
> > _M_message(__gnu_debug::__msg_inc_istreambuf)
> > ._M_iterator(*this));
> > vs
> >
> > + __glibcxx_requires_cond(_M_sbuf && !_S_is_eof(_M_sbuf->sgetc()),
> > _M_message(__gnu_debug::__msg_inc_istreambuf)
> > ._M_iterator(*this));
> >
> > and
> >
> > + __glibcxx_requires_cond(_M_sbuf
> > + && !traits_type::eq_int_type(_M_c,traits_type::eof()),
> > _M_message(__gnu_debug::__msg_inc_istreambuf)
> > ._M_iterator(*this));
> > vs
> >
> > + __glibcxx_requires_cond(_M_sbuf && !_S_is_eof(_M_sbuf->sgetc()),
> > _M_message(__gnu_debug::__msg_inc_istreambuf)
> > ._M_iterator(*this));
> >
> > I'm insist on the first variant. It free from code that may lead to different
> > behaviour between debug/non-debug (like _M_sbuf->sgetc()).
>
> The first patch fixed the impact of the Debug mode on the
> istreambuf_iterator state. This kind of difference is classical with
> Debug mode, this mode usually introduces additional calls to some
> operators or in this case to sgetc.
>
The key is "_M_sbuf->sgetc()" and "_S_is_eof" that may call ->sgetc() too.
This may lead to difference in debug/non-debug behaviour.
Solution without such difference exist and was presented here.