oml: Fix compiler warning about aliasing

Make the fill_fom_hdr return the header and use it throughout.

  CC       abis_nm.o
In file included from ../../include/openbsc/debug.h:8:0,
                 from abis_nm.c:38:
abis_nm.c: In function ‘abis_nm_opstart’:
abis_nm.c:1763:34: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
                                  ^
/home/ich/install/openbsc/include/osmocom/core/logging.h:23:74: note: in definition of macro ‘DEBUGP’
 #define DEBUGP(ss, fmt, args...) logp(ss, __FILE__, __LINE__, 0, fmt, ## args)
                                                                          ^
abis_nm.c:1763:2: note: in expansion of macro ‘abis_nm_debugp_foh’
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
  ^
abis_nm.c:1763:34: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
                                  ^
/home/ich/install/openbsc/include/osmocom/core/logging.h:23:74: note: in definition of macro ‘DEBUGP’
 #define DEBUGP(ss, fmt, args...) logp(ss, __FILE__, __LINE__, 0, fmt, ## args)
                                                                          ^
abis_nm.c:1763:2: note: in expansion of macro ‘abis_nm_debugp_foh’
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
  ^
abis_nm.c:1763:34: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
                                  ^
/home/ich/install/openbsc/include/osmocom/core/logging.h:23:74: note: in definition of macro ‘DEBUGP’
 #define DEBUGP(ss, fmt, args...) logp(ss, __FILE__, __LINE__, 0, fmt, ## args)
                                                                          ^
abis_nm.c:1763:2: note: in expansion of macro ‘abis_nm_debugp_foh’
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
  ^
abis_nm.c:1763:34: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
                                  ^
/home/ich/install/openbsc/include/osmocom/core/logging.h:23:74: note: in definition of macro ‘DEBUGP’
 #define DEBUGP(ss, fmt, args...) logp(ss, __FILE__, __LINE__, 0, fmt, ## args)
                                                                          ^
abis_nm.c:1763:2: note: in expansion of macro ‘abis_nm_debugp_foh’
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
  ^
abis_nm.c:1763:34: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
                                  ^
/home/ich/install/openbsc/include/osmocom/core/logging.h:23:74: note: in definition of macro ‘DEBUGP’
 #define DEBUGP(ss, fmt, args...) logp(ss, __FILE__, __LINE__, 0, fmt, ## args)
                                                                          ^
abis_nm.c:1763:2: note: in expansion of macro ‘abis_nm_debugp_foh’
  abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);

1 files changed, 5 insertions, 3 deletions

diff --git a/openbsc/src/libbsc/abis_nm.c b/openbsc/src/libbsc/abis_nm.c
index c29e21b3d..3bf55ec56 100644
--- a/openbsc/src/libbsc/abis_nm.c
+++ b/openbsc/src/libbsc/abis_nm.c
@@ -93,7 +93,7 @@ static void fill_om_hdr(struct abis_om_hdr *oh, uint8_t len)
 	oh->length = len;
 }
 
-static void fill_om_fom_hdr(struct abis_om_hdr *oh, uint8_t len,
+static struct abis_om_fom_hdr *fill_om_fom_hdr(struct abis_om_hdr *oh, uint8_t len,
 			    uint8_t msg_type, uint8_t obj_class,
 			    uint8_t bts_nr, uint8_t trx_nr, uint8_t ts_nr)
 {
@@ -106,6 +106,7 @@ static void fill_om_fom_hdr(struct abis_om_hdr *oh, uint8_t len,
 	foh->obj_inst.bts_nr = bts_nr;
 	foh->obj_inst.trx_nr = trx_nr;
 	foh->obj_inst.ts_nr = ts_nr;
+	return foh;
 }
 
 static struct msgb *nm_msgb_alloc(void)
@@ -1753,12 +1754,13 @@ static int __simple_cmd(struct gsm_bts *bts, uint8_t msg_type)
 int abis_nm_opstart(struct gsm_bts *bts, uint8_t obj_class, uint8_t i0, uint8_t i1, uint8_t i2)
 {
 	struct abis_om_hdr *oh;
+	struct abis_om_fom_hdr *foh;
 	struct msgb *msg = nm_msgb_alloc();
 
 	oh = (struct abis_om_hdr *) msgb_put(msg, ABIS_OM_FOM_HDR_SIZE);
-	fill_om_fom_hdr(oh, 0, NM_MT_OPSTART, obj_class, i0, i1, i2);
+	foh = fill_om_fom_hdr(oh, 0, NM_MT_OPSTART, obj_class, i0, i1, i2);
 
-	abis_nm_debugp_foh(DNM, (struct abis_om_fom_hdr *) oh->data);
+	abis_nm_debugp_foh(DNM, foh);
 	DEBUGPC(DNM, "Sending OPSTART\n");
 
 	return abis_nm_sendmsg(bts, msg);