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


On 10/16/2018 10:15 AM, Jonathan Wakely wrote:
On 16/10/18 07:06 +0200, François Dumont wrote:
On 10/15/2018 12:07 PM, 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
@@ -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 }; }

For functions like emplace (which are C++11-only) and for forward_list
(also C++11-only) using this syntax makes it clearer.

But for these functions it just makes cbegin() and cend() look
different to the C++98 begin() and end() functions, for no obvious
benefit.

Simply using { return end(); } would have been another option.

Personnaly I hesitated in writting:

{ return { _Base::cbegin(), this }; }

cause I prefer when you see clearly that Debug implem forward calls to the Normal implem.

I thought that using C++11 direct init was more likely to have gcc elide the copy constructor so I used it everywhere possible.

It should make no difference to elision at all.


Do you want me to restore constructor call ?


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