[cfe-dev] libc++ std::map self-assignment bug

[Karen Shaeffer]

On Fri, Nov 29, 2013 at 02:19:44AM +0100, Kal wrote:
> Hi Howard, etc,
> 
> libc++3.4 (rc1/trunk) std::map doesn't support self-assignment for std <
> c++11. The relevant code is:
> 
>     _LIBCPP_INLINE_VISIBILITY
>     map& operator=(const map& __m)
>         {
> #if __cplusplus >= 201103L
>             __tree_ = __m.__tree_;
> #else
>             __tree_.clear();
>             __tree_.value_comp() = __m.__tree_.value_comp();
>             __tree_.__copy_assign_alloc(__m.__tree_);
>             insert(__m.begin(), __m.end());
> #endif
>             return *this;
>         }
> 
> Maybe should be like:
> 
>     _LIBCPP_INLINE_VISIBILITY
>     map& operator=(const map& __m)
>         {
> #if __cplusplus >= 201103L
>             __tree_ = __m.__tree_;
> #else
>             if (this != &__m) {
>                 __tree_.clear();
>                 __tree_.value_comp() = __m.__tree_.value_comp();
>                 __tree_.__copy_assign_alloc(__m.__tree_);
>                 insert(__m.begin(), __m.end());
>             }
> #endif
>             return *this;
>         }
> 
> I see the same issue with unordered_map& operator=(const unordered_map&
> __u).
> 
> Thanks!
> Kal
--- end quoted text ---

Hi Kal,
I don't speak for Howard or anyone else. But my understanding is the stl library
generally doesn't perform checks like that with the goal of best possible performance.
I see a lot of code in stdlibc++ just like that.

enjoy,
Karen
-- 
Karen Shaeffer                 Be aware: If you see an obstacle in your path,
Neuralscape Services           that obstacle is your path.        Zen proverb