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diff --git a/lib/must_be.h b/lib/must_be.h
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+++ b/lib/must_be.h
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+/*
+ * SPDX-FileCopyrightText: 2019-2023, Alejandro Colomar <alx@kernel.org>
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+
+#ifndef SHADOW_INCLUDE_LIBMISC_MUST_BE_H_
+#define SHADOW_INCLUDE_LIBMISC_MUST_BE_H_
+
+
+#include <config.h>
+
+#include <assert.h>
+
+
+/*
+ * SYNOPSIS
+ *	int must_be(bool e);
+ *
+ * ARGUMENTS
+ *	e	Expression to be asserted.
+ *
+ * DESCRIPTION
+ *	This macro fails compilation if 'e' is false.  If 'e' is true,
+ *	it returns (int) 0, so it doesn't affect the expression in which
+ *	it is contained.
+ *
+ *	This macro is similar to static_assert(3).  While
+ *	static_assert(3) can only be used where a statement is allowed,
+ *	this must_be() macro can be used wherever an expression is
+ *	allowed.
+ *
+ * RETURN VALUE
+ *	0
+ *
+ * ERRORS
+ *	If 'e' is false, the compilation will fail, as when using
+ *	static_assert(3).
+ *
+ * EXAMPLES
+ *	#define must_be_array(a)  must_be(is_array(a))
+ *
+ *	#define NITEMS(a)  (sizeof(a) / sizeof(*(a)) + must_be_array(a))
+ *
+ *	int foo[42];
+ *	int bar[NITEMS(foo)];
+ */
+
+
+#define must_be(e)                                                            \
+(                                                                             \
+	0 * (int) sizeof(                                                     \
+		struct {                                                      \
+			static_assert(e, "");                                 \
+			int ISO_C_forbids_a_struct_with_no_members_;          \
+		}                                                             \
+	)                                                                     \
+)
+
+
+/*
+ * SYNOPSIS
+ *	int must_be_array(a);
+ *
+ * ARGUMENTS
+ *	a	Array.
+ *
+ * DESCRIPTION
+ *	This macro fails compilation if 'a' is not an array.  It is
+ *	useful in macros that accept an array as a parameter, where this
+ *	macro can validate the macro argument.  It prevent passing a
+ *	pointer to such macros, which would otherwise produce silent
+ *	bugs.
+ *
+ * RETURN VALUE
+ *	0
+ *
+ * ERRORS
+ *	If 'a' is not an array, the compilation will fail.
+ *
+ * EXAMPLES
+ *	int a[10];
+ *	int *p;
+ *
+ *	must_be_array(a);  // Ok
+ *	must_be_array(p);  // Compile-time error
+ *
+ * SEE ALSO
+ *	must_be()
+ */
+
+
+#define is_same_type(a, b)    __builtin_types_compatible_p(a, b)
+#define is_same_typeof(a, b)  is_same_type(typeof(a), typeof(b))
+#define is_array(a)           (!is_same_typeof((a), &(a)[0]))
+#define must_be_array(a)      must_be(is_array(a))
+
+
+#endif  // include guard