libstdc++-v3/testsuite/20_util/function/6.cc

   1 // { dg-do run { target c++11 } }
   2 // 2005-01-15 Douglas Gregor <dgregor@cs.indiana.edu>
   3 //
   4 // Copyright (C) 2005-2021 Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 3, or (at your option)
  10 // any later version.
  11 //
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING3.  If not see
  19 // <http://www.gnu.org/licenses/>.
  20
  21 // 20.7.15 polymorphic function object wrapper
  22 #include <functional>
  23 #include <testsuite_hooks.h>
  24
  25 template<typename T>
  26   const T&
  27   as_const(T& t)
  28   { return t; }
  29
  30 // Check that f's target is a reference_wrapper bound to obj.
  31 template<typename Function, typename T>
  32   bool
  33   wraps(Function& f, T& obj)
  34   {
  35     using ref_wrapper_type = std::reference_wrapper<T>;
  36     auto* p = f.template target<ref_wrapper_type>();
  37     return std::addressof(p->get()) == std::addressof(obj);
  38   }
  39
  40 struct secret {};
  41
  42 struct noncopyable_function_object_type
  43 {
  44   noncopyable_function_object_type(secret) {}
  45
  46   int operator()() const { return 42; }
  47   int operator()()       { return 17; }
  48
  49  private:
  50   noncopyable_function_object_type();
  51   noncopyable_function_object_type(const noncopyable_function_object_type&);
  52   void operator=(const noncopyable_function_object_type&);
  53 };
  54
  55 // Put reference_wrappers into function<> wrappers
  56 void test06()
  57 {
  58   using std::function;
  59   using std::ref;
  60   using std::cref;
  61
  62   secret password;
  63   noncopyable_function_object_type x(password);
  64
  65   function<int()> f(ref(x));
  66   VERIFY( f );
  67   VERIFY( f() == 17 );
  68   VERIFY( f.target_type() == typeid(std::ref(x)) ); // LWG 2781
  69   VERIFY( wraps(f, x) );
  70
  71   function<int()> g = f;
  72   VERIFY( g );
  73   VERIFY( g() == 17 );
  74   VERIFY( g.target_type() == f.target_type() );
  75   VERIFY( wraps(g, x) );
  76
  77   function<int()> h = cref(x);
  78   VERIFY( h );
  79   VERIFY( h() == 42 );
  80   VERIFY( h.target_type() == typeid(std::cref(x)) );
  81   VERIFY( wraps(h, as_const(x)) );
  82
  83   const function<int()>& hc = h;
  84   VERIFY( hc.target_type() == h.target_type() );
  85   VERIFY( wraps(hc, as_const(x)) );
  86 }
  87
  88 int main()
  89 {
  90   test06();
  91   return 0;
  92 }