Re: [PATCH] __debug::list use C++11 direct initialization

[Jonathan Wakely <jwakely at redhat dot com>]

On 17/10/18 17:03 +0100, Jonathan Wakely wrote:
> On 09/10/18 07:11 +0200, François Dumont wrote:
> > Here is the communication for my yesterday's patch which I thought 
> > svn had failed to commit (I had to interrupt it).
> >
> > Similarly to what I've done for associative containers here is a 
> > cleanup of the std::__debug::list implementation leveraging more on 
> > C++11 direct initialization.
> >
> > I also made sure we use consistent comparison between 
> > iterator/const_iterator in erase and emplace methods.
> >
> > 2018-10-08  François Dumont <fdumont@gcc.gnu.org>
> >
> >     * include/debug/list (list<>::cbegin()): Use C++11 direct
> >     initialization.
> >     (list<>::cend()): Likewise.
> >     (list<>::emplace<>(const_iterator, _Args&&...)): Likewise.
> >     (list<>::insert(const_iterator, initializer_list<>)): Likewise.
> >     (list<>::insert(const_iterator, size_type, const _Tp&)): Likewise.
> >     (list<>::erase(const_iterator, const_iterator)): Ensure consistent
> >     iterator comparisons.
> >     (list<>::splice(const_iterator, list&&, const_iterator,
> >     const_iterator)): Likewise.
> >
> > Tested under Linux x86_64 Debug mode and committed.
> >
> > François
>
> > diff --git a/libstdc++-v3/include/debug/list b/libstdc++-v3/include/debug/list
> > index 8add1d596e0..879e1177497 100644
> > --- a/libstdc++-v3/include/debug/list
> > +++ b/libstdc++-v3/include/debug/list
> > @@ -521,15 +521,17 @@ namespace __debug
> > 	// _GLIBCXX_RESOLVE_LIB_DEFECTS
> > 	// 151. can't currently clear() empty container
> > 	__glibcxx_check_erase_range(__first, __last);
> > -	for (_Base_const_iterator __victim = __first.base();
> > +	for (__decltype(__first.base()) __victim = __first.base();
>
> This change causes the regression.
>
> I think the problem is that the decltype is a reference, so every time
> the loop does ++__victim it changes the iterator stored in __first.


This would work:

       typedef typename __decltype(__first)::iterator_type _Base_iter;
	for (_Base_iter __victim = __first.base();
	     __victim != __last.base(); ++__victim)


Or simply:

#if __cplusplus >= 201103L
       typedef _Base_const_iterator _Base_iter;
#else
       typedef _Base_iterator _Base_iter;
#endif
	for (_Base_iter __victim = __first.base();
	     __victim != __last.base(); ++__victim)


Or just restore the original code which worked fine!