Merge pull request #25636 from thom311/th/wcast-align-fixes

all: avoid various "-Wcast-align=strict" warnings

src/basic/fd-util.c

@@ -501,7 +501,8 @@ void cmsg_close_all(struct msghdr *mh) {
 
         CMSG_FOREACH(cmsg, mh)
                 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
-                        close_many((int*) CMSG_DATA(cmsg), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int));
+                        close_many(CMSG_TYPED_DATA(cmsg, int),
+                                   (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int));
 }
 
 bool fdname_is_valid(const char *s) {

src/basic/hashmap.c

@@ -373,8 +373,9 @@ static void get_hash_key(uint8_t hash_key[HASH_KEY_SIZE], bool reuse_is_ok) {
 }
 
 static struct hashmap_base_entry* bucket_at(HashmapBase *h, unsigned idx) {
-        return (struct hashmap_base_entry*)
-                ((uint8_t*) storage_ptr(h) + idx * hashmap_type_info[h->type].entry_size);
+        return CAST_ALIGN_PTR(
+                        struct hashmap_base_entry,
+                        (uint8_t *) storage_ptr(h) + idx * hashmap_type_info[h->type].entry_size);
 }
 
 static struct plain_hashmap_entry* plain_bucket_at(Hashmap *h, unsigned idx) {

src/basic/socket-util.h

@@ -175,15 +175,17 @@ int flush_accept(int fd);
 #define CMSG_FOREACH(cmsg, mh)                                          \
         for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg)))
 
+#define CMSG_TYPED_DATA(cmsg, type)                                     \
+        ({                                                              \
+                struct cmsghdr *_cmsg = cmsg;                           \
+                _cmsg ? CAST_ALIGN_PTR(type, CMSG_DATA(_cmsg)) : (type*) NULL; \
+        })
+
 struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length);
 
 /* Type-safe, dereferencing version of cmsg_find() */
-#define CMSG_FIND_DATA(mh, level, type, ctype) \
-        ({                                                            \
-                struct cmsghdr *_found;                               \
-                _found = cmsg_find(mh, level, type, CMSG_LEN(sizeof(ctype))); \
-                (ctype*) (_found ? CMSG_DATA(_found) : NULL);         \
-        })
+#define CMSG_FIND_DATA(mh, level, type, ctype)                          \
+        CMSG_TYPED_DATA(cmsg_find(mh, level, type, CMSG_LEN(sizeof(ctype))), ctype)
 
 /* Resolves to a type that can carry cmsghdr structures. Make sure things are properly aligned, i.e. the type
  * itself is placed properly in memory and the size is also aligned to what's appropriate for "cmsghdr"

src/fundamental/macro-fundamental.h

@@ -354,6 +354,16 @@ static inline size_t ALIGN_TO(size_t l, size_t ali) {
                 ((l) + (ali) - 1) & ~((ali) - 1),                      \
                 VOID_0)
 
+/* Similar to ((t *) (void *) (p)) to cast a pointer. The macro asserts that the pointer has a suitable
+ * alignment for type "t". This exists for places where otherwise "-Wcast-align=strict" would issue a
+ * warning or if you want to assert that the cast gives a pointer of suitable alignment. */
+#define CAST_ALIGN_PTR(t, p)                                    \
+        ({                                                      \
+                const void *_p = (p);                           \
+                assert(((uintptr_t) _p) % __alignof__(t) == 0); \
+                (t *) _p;                                       \
+        })
+
 #define UPDATE_FLAG(orig, flag, b)                      \
         ((b) ? ((orig) | (flag)) : ((orig) & ~(flag)))
 #define SET_FLAG(v, flag, b) \

src/libsystemd-network/sd-dhcp6-client.c

@@ -1293,7 +1293,7 @@ static int client_receive_message(
                 if (cmsg->cmsg_level == SOL_SOCKET &&
                     cmsg->cmsg_type == SO_TIMESTAMP &&
                     cmsg->cmsg_len == CMSG_LEN(sizeof(struct timeval)))
-                        triple_timestamp_from_realtime(&t, timeval_load((struct timeval*) CMSG_DATA(cmsg)));
+                        triple_timestamp_from_realtime(&t, timeval_load(CMSG_TYPED_DATA(cmsg, struct timeval)));
         }
 
         if (client->transaction_id != (message->transaction_id & htobe32(0x00ffffff)))

src/libsystemd-network/sd-dhcp6-lease.c

@@ -619,7 +619,7 @@ static int dhcp6_lease_parse_message(
                                 return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
                                                               "Received information refresh time option with an invalid length (%zu).", optlen);
 
-                        irt = unaligned_read_be32((be32_t *) optval) * USEC_PER_SEC;
+                        irt = unaligned_read_be32(optval) * USEC_PER_SEC;
                         break;
                 }
         }