From fcb8bba28414daa6dd73809b1af31d571dcc9160 Mon Sep 17 00:00:00 2001
From: Zbigniew Chyla <zbigniew.chyla@nokia.com>
Date: Sun, 22 Mar 2015 21:51:45 +0200
Subject: Add compile-time check for arg type to NITEMS()

If a pointer (not array) is passed to NITEMS() macro, gcc will emit
compilation warning.
The actual check is based on newly added COMPILE_CHECK_IS_ARRAY macro.

The change doesn't affect generated binary code.
---
 compiler.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'compiler.h')

diff --git a/compiler.h b/compiler.h
index 8159d776..4fde42db 100644
--- a/compiler.h
+++ b/compiler.h
@@ -37,6 +37,27 @@
 #define UNUSED
 #endif
 
+/*
+ * Macro for compile-time checking if argument is an array.
+ * It expands to constant expression with int value 0.
+ */
+#if defined(__GNUC__)
+#define COMPILE_CHECK_IS_ARRAY(arr) ( \
+    0 * (int) sizeof(({ \
+        struct { \
+            int unused_int; \
+            typeof(arr) unused_arr; \
+        } zero_init = {0}; \
+        typeof(arr) arg_is_not_array UNUSED = { \
+            zero_init.unused_arr[0], \
+        }; \
+        1; \
+    })) \
+)
+#else
+#define COMPILE_CHECK_IS_ARRAY(arr) 0
+#endif
+
 /* Needed because 4.x versions of GCC are really annoying */
 #define ignore_return(funcall) \
     do { \
-- 
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