[PATCH v6 02/11] qapi: Make QAPI_LIST_ADD() public

[Eric Blake <eblake@redhat.com>]

We have a useful macro for inserting at the front of any
QAPI-generated list; move it from block.c to qapi/util.h so more
places can use it, including one earlier place in block.c.

There are many more places in the codebase that can benefit from using
the macro, but converting them will be left to later patches.

In theory, all QAPI list types are child classes of GenericList; but
in practice, that relationship is not explicitly spelled out in the C
type declarations (rather, it is something that happens implicitly due
to C compatible layouts), and the macro does not actually depend on
the GenericList type.  We considered moving GenericList from visitor.h
into util.h to group related code; however, such a move would be
awkward if we do not also move GenericAlternate.  Unfortunately,
moving GenericAlternate would introduce its own problems of
declaration circularity (qapi-builtin-types.h needs a complete
definition of QEnumLookup from util.h, but GenericAlternate needs a
complete definition of QType from qapi-builtin-types.h).

Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
---
 include/qapi/util.h |  8 ++++++++
 block.c             | 14 ++------------
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/include/qapi/util.h b/include/qapi/util.h
index a7c3c6414874..501abca38eaa 100644
--- a/include/qapi/util.h
+++ b/include/qapi/util.h
@@ -22,4 +22,12 @@ int qapi_enum_parse(const QEnumLookup *lookup, const char *buf,

 int parse_qapi_name(const char *name, bool complete);

+/* For any GenericList @list, insert @element at the front. */
+#define QAPI_LIST_ADD(list, element) do { \
+    typeof(list) _tmp = g_malloc(sizeof(*(list))); \
+    _tmp->value = (element); \
+    _tmp->next = (list); \
+    (list) = _tmp; \
+} while (0)
+
 #endif
diff --git a/block.c b/block.c
index 857387f3912f..8f9df5547d5a 100644
--- a/block.c
+++ b/block.c
@@ -5211,7 +5211,7 @@ BlockDriverState *bdrv_find_node(const char *node_name)
 BlockDeviceInfoList *bdrv_named_nodes_list(bool flat,
                                            Error **errp)
 {
-    BlockDeviceInfoList *list, *entry;
+    BlockDeviceInfoList *list;
     BlockDriverState *bs;

     list = NULL;
@@ -5221,22 +5221,12 @@ BlockDeviceInfoList *bdrv_named_nodes_list(bool flat,
             qapi_free_BlockDeviceInfoList(list);
             return NULL;
         }
-        entry = g_malloc0(sizeof(*entry));
-        entry->value = info;
-        entry->next = list;
-        list = entry;
+        QAPI_LIST_ADD(list, info);
     }

     return list;
 }

-#define QAPI_LIST_ADD(list, element) do { \
-    typeof(list) _tmp = g_malloc(sizeof(*(list))); \
-    _tmp->value = (element); \
-    _tmp->next = (list); \
-    (list) = _tmp; \
-} while (0)
-
 typedef struct XDbgBlockGraphConstructor {
     XDbgBlockGraph *graph;
     GHashTable *graph_nodes;
-- 
2.29.0