[Bug libstdc++/66146] call_once not C++11-compliant on ppc64le

[lh_mouse at 126 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66146

LIU Hao <lh_mouse at 126 dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lh_mouse at 126 dot com

--- Comment #53 from LIU Hao <lh_mouse at 126 dot com> ---
Why not implement `call_once` with `__cxa_guard_{acquire,release,abort}`?

It's basically

  ```
  template<typename _Callable, typename... _Args>
  void
  call_once(once_flag& __once, _Callable&& __callable, _Args&&... __args)
    {
      int __r = ::__cxa_guard_acquire(&__once);
      if(__r == 0)
        return;  // passive

      __try {
        _INVOKE(forward<_Callable>(__callable), forward<_Args>(__args)...);
      }
      __catch(...) {
        ::__cxa_guard_abort(&__once);  // exceptional
        __throw_exception_again;
      }
      ::__cxa_guard_release(&__once);  // returning
    }
  ```