libstdc++-v3/testsuite/27_io/rvalue_streams.cc

   1 // Copyright (C) 2008-2024 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-do run { target c++11 } }
  19
  20 #include <sstream>
  21 #include <string>
  22 #include <testsuite_hooks.h>
  23
  24 void
  25 test01()
  26 {
  27   int i = 1742;
  28   std::ostringstream() << i;
  29   std::string result ("1742");
  30   int i2;
  31   std::istringstream(result) >> i2;
  32   VERIFY (i == i2);
  33 }
  34
  35 struct X { bool as_rvalue; };
  36
  37 void operator>>(std::istream&, X& x) { x.as_rvalue = false; }
  38 void operator>>(std::istream&, X&& x) { x.as_rvalue = true; }
  39
  40 // LWG 2328 Rvalue stream extraction should use perfect forwarding
  41 void
  42 test02()
  43 {
  44   X x;
  45   std::istringstream is;
  46   auto&& ref1 = (std::move(is) >> x);
  47   VERIFY( &ref1 == &is );
  48   VERIFY( x.as_rvalue == false );
  49   auto&& ref2 = (std::move(is) >> std::move(x));
  50   VERIFY( &ref2 == &is );
  51   VERIFY( x.as_rvalue == true );
  52
  53   char arr[2];
  54 #if __cplusplus <= 201703L
  55   std::istringstream("x") >> &arr[0];
  56 #endif
  57   std::istringstream("x") >> arr;
  58   VERIFY( std::string(arr) == "x" );
  59 }
  60
  61 // LWG 1203 More useful rvalue stream insertion
  62 void
  63 test03()
  64 {
  65   int i = 1203;
  66   std::string result = (std::ostringstream() << "i = " << i).str();
  67   VERIFY( result == "i = 1203" );
  68
  69   std::ostringstream os;
  70   std::ostringstream&& ros = std::move(os) << result;
  71   VERIFY( &ros == &os );
  72   VERIFY( ros.str() == result );
  73
  74   std::stringstream ss;
  75   std::stringstream&& rss = std::move(ss) << result;
  76   VERIFY( &rss == &ss );
  77   VERIFY( rss.str() == result );
  78
  79   std::istringstream is("first second third");
  80   std::istringstream&& ris = std::move(is) >> result;
  81   VERIFY( &ris == &is );
  82   VERIFY( result == "first" );
  83
  84   std::stringstream ss2("fourth fifth sixth");
  85   std::stringstream&& rss2 = std::move(ss2) >> result;
  86   VERIFY( &rss2 == &ss2 );
  87   VERIFY( result == "fourth" );
  88 }
  89
  90 struct A { friend void operator<<(std::ios_base&, A) { } };
  91
  92 struct O : private std::ios_base { friend void operator<<(O&, int) { } };
  93
  94 template<typename Ostream, typename T, typename = void>
  95   struct is_insertable
  96   : std::false_type
  97   { };
  98
  99 template<typename> using void_t = void;
 100
 101 template<typename Ostream, typename T>
 102   using insert_result
 103     = decltype(std::declval<Ostream>() << std::declval<const T&>());
 104
 105 template<typename Ostream, typename T>
 106   struct is_insertable<Ostream, T, void_t<insert_result<Ostream, T>>>
 107   : std::true_type
 108   { };
 109
 110 // LWG 1203 negative tests
 111 void
 112 test04()
 113 {
 114   static_assert( is_insertable<std::ios_base&, A>::value,
 115       "valid using the friend operator<<" );
 116   static_assert( !is_insertable<std::ios_base&&, A>::value,
 117       "ill-formed because ios_base is not derived from ios_base" );
 118
 119   static_assert( is_insertable<O&, int>::value,
 120       "valid using the friend operator<<" );
 121   static_assert( !is_insertable<O&&, int>::value,
 122       "ill-formed because O is not publicly derived from ios_base" );
 123 }
 124
 125 int
 126 main()
 127 {
 128   test01();
 129   test02();
 130   test03();
 131   test04();
 132 }