include/o3tl/unreachable.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #ifndef INCLUDED_O3TL_UNREACHABLE_HXX
  11 #define INCLUDED_O3TL_UNREACHABLE_HXX
  12
  13 #include <sal/config.h>
  14
  15 #include <cassert>
  16 #include <utility>
  17
  18 // An approximation of C++23 std::unreachable
  19 // (<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p0627r6.pdf> "Function to mark
  20 // unreachable code").
  21
  22 #if defined __cpp_lib_unreachable
  23
  24 #define O3TL_UNREACHABLE (::std::unreachable())
  25
  26 #else
  27
  28 // This fallback implementation is inspired by LLVM's LLVM_BUILTIN_UNREACHABLE
  29 // (llvm/include/llvm/Support/Compiler.h).
  30
  31 #if defined _MSC_VER
  32 #define O3TL_UNREACHABLE_detail __assume(false)
  33 #else // assuming Clang or GCC with support for:
  34 #define O3TL_UNREACHABLE_detail __builtin_unreachable()
  35 #endif
  36
  37 #define O3TL_UNREACHABLE                                                                           \
  38     do                                                                                             \
  39     {                                                                                              \
  40         assert(false);                                                                             \
  41         O3TL_UNREACHABLE_detail;                                                                   \
  42     } while (false)
  43
  44 #endif
  45
  46 #endif
  47
  48 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */