libstdc++-v3/testsuite/18_support/launder/1.cc

   1 // Copyright (C) 2016-2021 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++17" }
  19 // { dg-do run { target c++17 } }
  20
  21 #include <new>
  22 #include <testsuite_hooks.h>
  23 #include <testsuite_tr1.h>
  24
  25 void
  26 test01()
  27 {
  28   struct S {
  29     int i;
  30   } s;
  31   auto p = std::launder( &s.i );
  32   VERIFY( p == &s.i );
  33 }
  34
  35
  36 void
  37 test02()
  38 {
  39   // C++17 1.8 [intro.object]
  40   struct X { const int n; };
  41   union U { X x; float f; };
  42
  43   U u = {{ 1 }};
  44   u.f = 5.f; // OK, creates new subobject of u (9.3)
  45   X *p = new (&u.x) X {2}; // OK, creates new subobject of u
  46   VERIFY(p->n == 2); // OK
  47   VERIFY(*std::launder(&u.x.n) == 2); // OK
  48   // assert(u.x.n == 2); undefined behavior, u.x does not name new subobject
  49 }
  50
  51 int
  52 main()
  53 {
  54   test01();
  55   test02();
  56 }