unreachable.hxx

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
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#ifndef INCLUDED_O3TL_UNREACHABLE_HXX
#define INCLUDED_O3TL_UNREACHABLE_HXX
 
#include <sal/config.h>
 
#include <cassert>
#include <utility>
 
// An approximation of C++23 std::unreachable
// (<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p0627r6.pdf> "Function to mark
// unreachable code").
 
#if defined __cpp_lib_unreachable
 
#define O3TL_UNREACHABLE (::std::unreachable())
 
#else
 
// This fallback implementation is inspired by LLVM's LLVM_BUILTIN_UNREACHABLE
// (llvm/include/llvm/Support/Compiler.h).
 
#if defined _MSC_VER
#define O3TL_UNREACHABLE_detail __assume(false)
#else // assuming Clang or GCC with support for:
#define O3TL_UNREACHABLE_detail __builtin_unreachable()
#endif
 
#define O3TL_UNREACHABLE                                                                           \
    do                                                                                             \
    {                                                                                              \
        assert(false);                                                                             \
        O3TL_UNREACHABLE_detail;                                                                   \
    } while (false)
 
#endif
 
#endif
 
/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */