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

[Jonathan Wakely]

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>
>
>Â Â Â  * include/debug/list (list<>::cbegin()): Use C++11 direct
>Â Â Â  initialization.
>Â Â Â  (list<>::cend()): Likewise.
>Â Â Â  (list<>::emplace<>(const_iterator, _Args&&...)): Likewise.
>Â Â Â  (list<>::insert(const_iterator, initializer_list<>)): Likewise.
>Â Â Â  (list<>::insert(const_iterator, size_type, const _Tp&)): Likewise.
>Â Â Â  (list<>::erase(const_iterator, const_iterator)): Ensure consistent
>Â Â Â  iterator comparisons.
>Â Â Â  (list<>::splice(const_iterator, list&&, const_iterator,
>Â Â Â  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
>@@ -244,11 +244,11 @@ namespace __debug
> #if __cplusplus >= 201103L
>       const_iterator
>       cbegin() const noexcept
>-      { return const_iterator(_Base::begin(), this); }
>+      { return { _Base::begin(), this }; }
> 
>       const_iterator
>       cend() const noexcept
>-      { return const_iterator(_Base::end(), this); }
>+      { return { _Base::end(), this }; }
> 
>       const_reverse_iterator
>       crbegin() const noexcept
>@@ -405,8 +405,8 @@ namespace __debug
> 	emplace(const_iterator __position, _Args&&... __args)
> 	{
> 	  __glibcxx_check_insert(__position);
>-	  return iterator(_Base::emplace(__position.base(),
>-					std::forward<_Args>(__args)...), this);
>+	  return  { _Base::emplace(__position.base(),
>+				   std::forward<_Args>(__args)...), this };
> 	}
> #endif
> 
>@@ -430,7 +430,7 @@ namespace __debug
>       insert(const_iterator __p, initializer_list<value_type> __l)
>       {
> 	__glibcxx_check_insert(__p);
>-	return iterator(_Base::insert(__p.base(), __l), this);
>+	return { _Base::insert(__p.base(), __l), this };
>       }
> #endif
> 
>@@ -439,7 +439,7 @@ namespace __debug
>       insert(const_iterator __position, size_type __n, const _Tp& __x)
>       {
> 	__glibcxx_check_insert(__position);
>-	return iterator(_Base::insert(__position.base(), __n, __x), this);
>+	return { _Base::insert(__position.base(), __n, __x), this };
>       }
> #else
>       void
>@@ -465,7 +465,7 @@ namespace __debug
> 		_Base::insert(__position.base(),
> 			      __gnu_debug::__unsafe(__first),
> 			      __gnu_debug::__unsafe(__last)),
>-		  this
>+		this
> 	      };
> 	  else
> 	    return { _Base::insert(__position.base(), __first, __last), this };
>@@ -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.