From 8ed23cb9874f25ad048ce359d1102c8f487915ec Mon Sep 17 00:00:00 2001 From: Thomas Haller Date: Fri, 10 May 2019 08:03:54 +0200 Subject: shared: use union instead of _nm_alignas() for static hash-seed 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. --- shared/nm-glib-aux/nm-hash-utils.c | 16 +++++++++++----- shared/nm-glib-aux/nm-hash-utils.h | 2 +- 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). * -- cgit v1.2.1