format specifies type 'unsigned short' but the argument has type 'int' error in network stack

[nashif]

Describe the bug
Build failure when building with llvm:

[ 82%] Building C object zephyr/subsys/net/ip/CMakeFiles/subsys__net__ip.dir/connection.c.obj
[ 83%] Building C object zephyr/subsys/net/ip/CMakeFiles/subsys__net__ip.dir/tcp2.c.obj
/home/nashif/Work/zephyrproject/zephyr/subsys/net/ip/tcp2.c:885:2: error: format specifies type 'unsigned short' but the argument has type 'int' [-Werror,-Wformat]
        conn_send_data_dump(conn);
        ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/nashif/Work/zephyrproject/zephyr/subsys/net/ip/./tcp2_priv.h:102:3: note: expanded from macro 'conn_send_data_dump'
                conn_mss((_conn)));                                     \
                ^~~~~~~~~~~~~~~~~~
/home/nashif/Work/zephyrproject/zephyr/include/net/net_core.h:49:6: note: expanded from macro 'NET_DBG'
                        ##__VA_ARGS__)

To Reproduce

export ZEPHYR_TOOLCHAIN_VARIANT=llvm
west build -b qemu_x86 tests/net/socket/poll

Expected behavior
clean build

[nashif]

the issue still there, was able to fix it with:

diff --git a/subsys/net/ip/tcp2_priv.h b/subsys/net/ip/tcp2_priv.h
index f68eee05af..3c0b71742b 100644
--- a/subsys/net/ip/tcp2_priv.h
+++ b/subsys/net/ip/tcp2_priv.h
@@ -99,7 +99,7 @@
                "send_win=%hu, mss=%hu",                                \
                (_conn), net_pkt_get_len((_conn)->send_data),           \
                conn->unacked_len, conn->send_win,                      \
-               conn_mss((_conn)));                                     \
+               (uint16_t)conn_mss((_conn)));                                   \
        NET_DBG("conn: %p send_data_timer=%hu, send_data_retries=%hu",  \
                (_conn),                                                \
                (bool)k_delayed_work_remaining_get(&(_conn)->send_data_timer),\

[jukkar]

Is there a bug in llvm, as the conn_mss() is returning uint16_t always so there should not be any warning.
The conn_mss() is specified as

#define conn_mss(_conn)					\
	((_conn)->recv_options.mss_found ?		\
	 (_conn)->recv_options.mss : (uint16_t)NET_IPV6_MTU)

and the type of recv_options.mss is

struct tcp_options {
	uint16_t mss;
	uint16_t window;
	bool mss_found : 1;
	bool wnd_found : 1;
};

[nashif]

Is there a bug in llvm, as the conn_mss() is returning uint16_t always so there should not be any warning.

possibly, I was puzzled with this myself.