From: Alejandro Colomar <alx@kernel.org>
Date: Fri, 4 Aug 2023 17:49:57 +0000 (+0200)
Subject: must_be.h: Add must_be_array() macro
X-Git-Tag: 4.15.0-rc1~209
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c3a8d02b9f66763b3ef1756ba1dec4e9b039d14e;p=thirdparty%2Fshadow.git

must_be.h: Add must_be_array() macro

This macro statically asserts that the argument is an array.

Link: <https://stackoverflow.com/a/57537491>
Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---

diff --git a/lib/must_be.h b/lib/must_be.h
index 30edc558f..2ca7b62a2 100644
--- a/lib/must_be.h
+++ b/lib/must_be.h
@@ -58,4 +58,41 @@
 )
 
 
+/*
+ * 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(typeof(a), typeof(b))
+#define is_array(a)         (!is_same_type((a), &(a)[0]))
+#define must_be_array(a)    must_be(is_array(a))
+
+
 #endif  // include guard