Finally, ARRAY_SIZE!

[ccan] / ccan / array_size / array_size.h

diff --git a/ccan/array_size/array_size.h b/ccan/array_size/array_size.h
new file mode 100644 (file)
index 0000000..c561c0a
--- /dev/null
+++ b/ccan/array_size/array_size.h
@@ -0,0 +1,25 @@
+#ifndef CCAN_ARRAY_SIZE_H
+#define CCAN_ARRAY_SIZE_H
+#include "config.h"
+#include <ccan/build_assert/build_assert.h>
+
+/**
+ * ARRAY_SIZE - get the number of elements in a visible array
+ * @arr: the array whose size you want.
+ *
+ * This does not work on pointers, or arrays declared as [], or
+ * function parameters.  With correct compiler support, such usage
+ * will cause a build error (see build_assert).
+ */
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + _array_size_chk(arr))
+
+#if HAVE_BUILTIN_TYPES_COMPATIBLE_P && HAVE_TYPEOF
+/* Two gcc extensions.
+ * &a[0] degrades to a pointer: a different type from an array */
+#define _array_size_chk(arr)                                           \
+       EXPR_BUILD_ASSERT(!__builtin_types_compatible_p(typeof(arr),    \
+                                                       typeof(&(arr)[0])))
+#else
+#define _array_size_chk(arr) 0
+#endif
+#endif /* CCAN_ALIGNOF_H */