msgb: Add may_alias attribute to struct libgb_msgb_cb
This explicitely allows aliasing of this struct to avoid the warning
shown below. Note, that this warning isn't show when
'-fno-strict-aliasing' is used.
Addresses:
gb/gprs_ns_test.c:85:54: warning: dereferencing type-punned pointer will
break strict-aliasing rules [-Wstrict-aliasing]
diff --git a/include/osmocom/gprs/gprs_msgb.h b/include/osmocom/gprs/gprs_msgb.h
index f4c8554..e277696 100644
--- a/include/osmocom/gprs/gprs_msgb.h
+++ b/include/osmocom/gprs/gprs_msgb.h
@@ -16,7 +16,7 @@
/* Identifier of a MS (inside BTS), equal to 'struct sgsn_mm_ctx' */
uint32_t tlli;
-} __attribute__((packed));
+} __attribute__((packed, may_alias));
#define LIBGB_MSGB_CB(__msgb) ((struct libgb_msgb_cb *)&((__msgb)->cb[0]))
#define msgb_tlli(__x) LIBGB_MSGB_CB(__x)->tlli
#define msgb_nsei(__x) LIBGB_MSGB_CB(__x)->nsei