diff --git a/src/macros.h b/src/macros.h
index c11ee66..4ca24c0 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -396,3 +396,6 @@
 #ifndef MAX
 # define MAX(a, b) ((a) > (b) ? (a) : (b))
 #endif
+
+// Length of the array.
+#define ARRAY_LENGTH(a) (sizeof(a) / sizeof((a)[0]))