libstdc++-v3/testsuite/23_containers/span/back_neg.cc

   1 // Copyright (C) 2019-2025 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 compile { target c++20 } }
  19
  20 #include <span>
  21
  22 constexpr bool
  23 test01(bool b)
  24 {
  25   std::span<int, 0> s;
  26   if (b || !s.empty())
  27     (void) s.back();
  28   return true;
  29 }
  30
  31 static_assert(test01(false));
  32 static_assert(test01(true)); // { dg-error "non-constant" }
  33 // { dg-error "assert_fail" "" { target *-*-* } 0 }
  34 // { dg-prune-output "called in a constant expression" }