shared: use union instead of _nm_alignas() for static hash-seedth/authchain-cleanup

We want the the hash-seed array is alined so it can be used both as
guint, guint32, and guint64 directly. Don't use _nm_alignas() but
instead just add the fields to the union so we get proper alignment.

While at at, also let the seed argument to c_siphash_init() be aligned
to 64 integers. c_siphash_init() does not require that, but it tries to
read the seed as (unaligned) LE 64 bit integers. So, it doesn't hurt.

2 files changed, 12 insertions, 6 deletions

diff --git a/shared/nm-glib-aux/nm-hash-utils.c b/shared/nm-glib-aux/nm-hash-utils.c
index 6e728e6b20..3ab39db712 100644
--- a/shared/nm-glib-aux/nm-hash-utils.c
+++ b/shared/nm-glib-aux/nm-hash-utils.c
@@ -45,7 +45,10 @@ _get_hash_key_init (void)
 	 * to use it as guint* or guint64* pointer. */
 	static union {
 		guint8 v8[HASH_KEY_SIZE];
-	} g_arr _nm_alignas (guint64);
+		guint _align_as_uint;
+		guint32 _align_as_uint32;
+		guint64 _align_as_uint64;
+	} g_arr;
 	const guint8 *g;
 	union {
 		guint8 v8[HASH_KEY_SIZE];
@@ -125,14 +128,17 @@ void
 nm_hash_siphash42_init (CSipHash *h, guint static_seed)
 {
 	const guint8 *g;
-	guint seed[HASH_KEY_SIZE_GUINT];
+	union {
+		guint64 _align_as_uint64;
+		guint arr[HASH_KEY_SIZE_GUINT];
+	} seed;
 
 	nm_assert (h);
 
 	g = _get_hash_key ();
-	memcpy (seed, g, HASH_KEY_SIZE);
-	seed[0] ^= static_seed;
-	c_siphash_init (h, (const guint8 *) seed);
+	memcpy (&seed, g, HASH_KEY_SIZE);
+	seed.arr[0] ^= static_seed;
+	c_siphash_init (h, (const guint8 *) &seed);
 }
 
 guint
diff --git a/shared/nm-glib-aux/nm-hash-utils.h b/shared/nm-glib-aux/nm-hash-utils.h
index af115a7c67..07518868cf 100644
--- a/shared/nm-glib-aux/nm-hash-utils.h
+++ b/shared/nm-glib-aux/nm-hash-utils.h
@@ -34,7 +34,7 @@ void nm_hash_siphash42_init (CSipHash *h, guint static_seed);
  *
  * Note, that this is guaranteed to use siphash42 under the hood (contrary to
  * all other NMHash API, which leave this undefined). That matters at the point,
- * where the caller needs to be sure that a reasonably strong hasing algorithm
+ * where the caller needs to be sure that a reasonably strong hashing algorithm
  * is used.  (Yes, NMHash is all about siphash24, but otherwise that is not promised
  * anywhere).
  *