// { dg-do compile { target c++11 } }
// { dg-additional-options "-pthread" { target pthread } }

// Copyright (C) 2014-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.

// libstdc++/60497

#include <mutex>
#include <memory>
#include <functional>

struct A;
template<typename T> struct B { T t; };

using UP = std::unique_ptr<B<A>>;

void f(UP&) { }

void g(UP& p)
{
  std::once_flag o;
  std::call_once(o, f, std::ref(p));
}