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

[Jonathan Wakely <jwakely at redhat dot com>]

On 17/10/18 17:10 +0100, Jonathan Wakely wrote:
> 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!


Unrelated to this change, I'm also seeing some test failures when run
with -O0 -D_GLIBCXX_DEBUG e.g.

make check RUNTESTFLAGS="conformance.exp=23_containers/unordered_*/cliterators.cc --target_board=unix/-O0/-D_GLIBCXX_DEBUG"

There are linker errors:

FAIL: 23_containers/unordered_map/requirements/cliterators.cc (test for excess errors)
Excess errors:
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.h:332: undefined reference to `__gnu_debug::_Safe_local_iterator_base::_M_attach_single(__gnu_debug::_Safe_sequence_base*, bool)'
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.h:332: undefined reference to `__gnu_debug::_Safe_local_iterator_base::_M_attach_single(__gnu_debug::_Safe_sequence_base*, bool)'
collect2: error: ld returned 1 exit status
UNRESOLVED: 23_containers/unordered_map/requirements/cliterators.cc compilation failed to produce executable