1 files changed, 48 insertions, 0 deletions
diff --git a/include/o3tl/unreachable.hxx b/include/o3tl/unreachable.hxx
new file mode 100644
index 000000000..604f7a2f7
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+++ b/include/o3tl/unreachable.hxx
@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#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: */