rb: fix compilation issue

rb.h uses an inline definition of rb_remove which uses NULL.
since the standard declaration of NULL can be found in stdlib.h, we
need to include it.

1 files changed, 3 insertions, 0 deletions

diff --git a/rb.h b/rb.h
index 1483977..c5bde89 100644
--- a/rb.h
+++ b/rb.h
@@ -19,6 +19,9 @@
 #ifndef RING_BUFFER_H
 #define RING_BUFFER_H
 
+/* needed for the definition of NULL */
+#include <stdlib.h>
+
 #include <stdint.h>
 #include <sys/types.h>