msgb: Make sure at compile time that headroom is smaller than size

All current code is using constants to allocate the msgb with
headroom. Use a static_assert to make sure that the headroom
is smaller than the size. This makes API misusage unlikely to
happen.

1 files changed, 3 insertions, 0 deletions

diff --git a/include/osmocore/msgb.h b/include/osmocore/msgb.h
index 6fd24c7f..c4f44305 100644
--- a/include/osmocore/msgb.h
+++ b/include/osmocore/msgb.h
@@ -22,6 +22,7 @@
 
 #include <stdint.h>
 #include "linuxlist.h"
+#include "utils.h"
 
 #define MSGB_DEBUG
 
@@ -180,6 +181,8 @@ static inline void msgb_reserve(struct msgb *msg, int len)
 static inline struct msgb *msgb_alloc_headroom(int size, int headroom,
 						const char *name)
 {
+	static_assert(size > headroom, headroom_bigger);
+
 	struct msgb *msg = msgb_alloc(size, name);
 	if (msg)
 		msgb_reserve(msg, headroom);