[PATCH] libstdc++: Implement C++20 atomic<shared_ptr> and atomic<weak_ptr>

[Stephan Bergmann]

On 1/17/22 01:12, Jonathan Wakely via Libstdc++ wrote:
> Here's the finished version of that patch, which is all inline in the
> header, and performs faster too.
> 
> Tested powerpc64le-linux and x86_64-linux.
> Pushed to trunk.

FYI, recent Clang still requires typename in two places to compile 
<memory> with -std=c++20,

> diff --git a/libstdc++-v3/include/bits/shared_ptr_atomic.h b/libstdc++-v3/include/bits/shared_ptr_atomic.h
> index 900499bae32..50aa46370ca 100644
> --- a/libstdc++-v3/include/bits/shared_ptr_atomic.h
> +++ b/libstdc++-v3/include/bits/shared_ptr_atomic.h
> @@ -456,8 +456,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        typename _Tp::element_type* _M_ptr;
>        _Atomic_count _M_refcount;
>  
> -      static _Atomic_count::pointer
> -      _S_add_ref(_Atomic_count::pointer __p)
> +      static typename _Atomic_count::pointer
> +      _S_add_ref(typename _Atomic_count::pointer __p)
>        {
>  	if (__p)
>  	  {