{include,lib/*}: Split refcount initializers from values

Previously refcount types defined in uk/refcount.h and uk/swrefcount.h
provided initializer macros in the form of anonymous struct values (i.e.
designated initializers cast to the struct type). This prevented them
from being used to initialize static variables with nested structs on
some compilers, most notably GCC up to version 12.

This change separates initializers from initial values as two different
macros, the first to be used for initializing (static) variables, with
the second meant for direct assignment to already declared structs.
In addition, all uses of refcount initializers in variable assignments
have been changed to correctly use initial value macros.

Signed-off-by: Andrei Tatar <[email protected]>
Reviewed-by: Maria Sfiraiala <[email protected]>
Reviewed-by: Marco Schlumpp <[email protected]>
Approved-by: Razvan Deaconescu <[email protected]>
GitHub-Closes: unikraft#1245

Author: andreittr

include/uk/refcount.h

@@ -56,7 +56,13 @@ extern "C" {
 	} while (0)
 #endif /* CONFIG_LIBUKDEBUG */
 
-#define UK_REFCOUNT_INITIALIZER(val) ((__atomic){ .counter = (val) })
+/*
+ * We define initializers separate from an initial values.
+ * The former can only be used in (static) variable initializations, while the
+ * latter is meant for assigning to variables or as anonymous data structures.
+ */
+#define UK_REFCOUNT_INITIALIZER(val) { .counter = (val) }
+#define UK_REFCOUNT_INIT_VALUE(val) ((__atomic)UK_REFCOUNT_INITIALIZER(val))
 
 /**
  * Initialize the atomic reference.

include/uk/weak_refcount.h

@@ -17,10 +17,17 @@ struct uk_swrefcount {
 	__atomic strong; /* Number of strong references; <= .refcount */
 };
 
-#define UK_SWREFCOUNT_INITIALIZER(r, s) ((struct uk_swrefcount){ \
+/*
+ * We define initializers separate from an initial values.
+ * The former can only be used in (static) variable initializations, while the
+ * latter is meant for assigning to variables or as anonymous data structures.
+ */
+#define UK_SWREFCOUNT_INITIALIZER(r, s) { \
 	.refcount = UK_REFCOUNT_INITIALIZER((r)), \
 	.strong = UK_REFCOUNT_INITIALIZER((s)), \
-})
+}
+#define UK_SWREFCOUNT_INIT_VALUE(r, s) \
+	((struct uk_swrefcount)UK_SWREFCOUNT_INITIALIZER((r), (s)))
 
 /**
  * Initialize refcount with `ref` references, of which `strong` are strong.

lib/posix-eventfd/eventfd.c

@@ -137,7 +137,7 @@ struct uk_file *uk_eventfile_create(unsigned int count, int flags)
 	al->alloc = a;
 	al->counter = count;
 	al->fstate = UK_FILE_STATE_INITIALIZER(al->fstate);
-	al->frefcnt = UK_FILE_REFCNT_INITIALIZER;
+	al->frefcnt = UK_FILE_REFCNT_INIT_VALUE;
 	al->f = (struct uk_file){
 		.vol = vol,
 		.node = &al->counter,

lib/posix-pipe/pipe.c

@@ -292,8 +292,8 @@ int uk_pipefile_create(struct uk_file *pipes[2], int flags)
 	al->node.whead = 0;
 	memset(al->node.buf, 0, sizeof(al->node.buf));
 	al->fstate = UK_FILE_STATE_INITIALIZER(al->fstate);
-	al->rref = UK_FILE_REFCNT_INITIALIZER;
-	al->wref = UK_FILE_REFCNT_INITIALIZER;
+	al->rref = UK_FILE_REFCNT_INIT_VALUE;
+	al->wref = UK_FILE_REFCNT_INIT_VALUE;
 	al->rf = (struct uk_file){
 		.vol = PIPE_VOLID,
 		.node = &al->node,

lib/posix-poll/epoll.c

@@ -368,7 +368,7 @@ struct uk_file *uk_epollfile_create(void)
 	al->alloc = a;
 	al->list = NULL;
 	al->fstate = UK_FILE_STATE_INITIALIZER(al->fstate);
-	al->frefcnt = UK_FILE_REFCNT_INITIALIZER;
+	al->frefcnt = UK_FILE_REFCNT_INIT_VALUE;
 	al->f = (struct uk_file){
 		.vol = EPOLL_VOLID,
 		.node = &al->list,

lib/posix-socket/socket.c

@@ -230,7 +230,7 @@ static void _socket_init(struct socket_alloc *al,
 		.driver = d
 	};
 	al->fstate = UK_FILE_STATE_INITIALIZER(al->fstate);
-	al->fref = UK_FILE_REFCNT_INITIALIZER;
+	al->fref = UK_FILE_REFCNT_INIT_VALUE;
 	al->f = (struct uk_file){
 		.vol = POSIX_SOCKET_VOLID,
 		.node = &al->node,

lib/posix-timerfd/timerfd.c

@@ -225,7 +225,7 @@ struct uk_file *uk_timerfile_create(clockid_t id)
 		.upthread = NULL
 	};
 	al->fstate = UK_FILE_STATE_INITIALIZER(al->fstate);
-	al->frefcnt = UK_FILE_REFCNT_INITIALIZER;
+	al->frefcnt = UK_FILE_REFCNT_INIT_VALUE;
 	al->f = (struct uk_file){
 		.vol = TIMERFD_VOLID,
 		.node = &al->node,

lib/ukfile/include/uk/file.h

@@ -133,6 +133,7 @@ struct uk_file {
 
 /* Files always get created with one strong reference held */
 #define UK_FILE_REFCNT_INITIALIZER UK_SWREFCOUNT_INITIALIZER(1, 1)
+#define UK_FILE_REFCNT_INIT_VALUE UK_SWREFCOUNT_INIT_VALUE(1, 1)
 
 /* Operations inlines */
 static inline