libstdc++-v3/testsuite/20_util/function_objects/invoke/constexpr.cc

   1 // Copyright (C) 2019 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-options "-std=gnu++2a" }
  19 // { dg-do compile { target c++2a } }
  20
  21 #include <functional>
  22
  23 #ifndef __cpp_lib_constexpr_invoke
  24 # error "Feature test macro for constexpr invoke is missing"
  25 #elif __cpp_lib_constexpr_invoke < 201907L
  26 # error "Feature test macro for constexpr invoke has wrong value"
  27 #endif
  28
  29 constexpr int inc(int i) { return i + 1; }
  30 constexpr auto inc_f = &inc;
  31 static_assert( std::invoke(inc_f, 2) == 3);
  32
  33 struct Dec
  34 {
  35   constexpr int operator()(int i) const { return i - 1; }
  36 };
  37
  38 static_assert( std::invoke(Dec{}, 5) == 4 );