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
  17 // A better replacement for assert(false) to indicate a place in the code that should not be
  18 // reachable.  This should improve on the sometimes poor false-positive warnings emitted by
  19 // compilers when they cannot detect that some condition flagged by assert(false) cannot occur,
  20 // either because assert is reduced to a no-op by NDEBUG or because assert is not marked as noreturn
  21 // in the MSVC headers.  This is inspired by LLVM's LLVM_BUILTIN_UNREACHABLE
  22 // (llvm/include/llvm/Support/Compiler.h).
  23
  24 #if defined _MSC_VER
  25 #define O3TL_UNREACHABLE_detail __assume(false)
  26 #else // assuming Clang or GCC with support for:
  27 #define O3TL_UNREACHABLE_detail __builtin_unreachable()
  28 #endif
  29
  30 #define O3TL_UNREACHABLE                                                                           \
  31     do                                                                                             \
  32     {                                                                                              \
  33         assert(false);                                                                             \
  34         O3TL_UNREACHABLE_detail;                                                                   \
  35     } while (false)
  36
  37 #endif
  38
  39 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */