libstdc++-v3/testsuite/20_util/reference_wrapper/constexpr.cc

// Copyright (C) 2019-2021 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/>.

// { dg-options "-std=gnu++2a" }
// { dg-do compile { target c++2a } }

#include <functional>

struct F
{
  constexpr int operator()(int i, int j) { return i + j; }
  constexpr int operator()(int i, int j) const { return i * j; }
};

constexpr int
test01(int i, int j)
{
  F f;
  return std::ref(std::ref(f))(i, j);
}

static_assert( test01(1, 2) == 3 );

constexpr int
test02(int i, int j)
{
  F f;
  return std::cref(std::cref(f))(i, j);
}

static_assert( test02(4, 5) == 20 );