qapi: Don't special-case simple union wrappers

Simple unions were carrying a special case that hid their 'data'
QMP member from the resulting C struct, via the hack method
QAPISchemaObjectTypeVariant.simple_union_type().  But by using
the work we started by unboxing flat union and alternate
branches, coupled with the ability to visit the members of an
implicit type, we can now expose the simple union's implicit
type in qapi-types.h:

| struct q_obj_ImageInfoSpecificQCow2_wrapper {
|     ImageInfoSpecificQCow2 *data;
| };
|
| struct q_obj_ImageInfoSpecificVmdk_wrapper {
|     ImageInfoSpecificVmdk *data;
| };
...
| struct ImageInfoSpecific {
|     ImageInfoSpecificKind type;
|     union { /* union tag is @type */
|         void *data;
|-        ImageInfoSpecificQCow2 *qcow2;
|-        ImageInfoSpecificVmdk *vmdk;
|+        q_obj_ImageInfoSpecificQCow2_wrapper qcow2;
|+        q_obj_ImageInfoSpecificVmdk_wrapper vmdk;
|     } u;
| };

Doing this removes asymmetry between QAPI's QMP side and its
C side (both sides now expose 'data'), and means that the
treatment of a simple union as sugar for a flat union is now
equivalent in both languages (previously the two approaches used
a different layer of dereferencing, where the simple union could
be converted to a flat union with equivalent C layout but
different {} on the wire, or to an equivalent QMP wire form
but with different C representation).  Using the implicit type
also lets us get rid of the simple_union_type() hack.

Of course, now all clients of simple unions have to adjust from
using su->u.member to using su->u.member.data; while this touches
a number of files in the tree, some earlier cleanup patches
helped minimize the change to the initialization of a temporary
variable rather than every single member access.  The generated
qapi-visit.c code is also affected by the layout change:

|@@ -7393,10 +7393,10 @@ void visit_type_ImageInfoSpecific_member
|     }
|     switch (obj->type) {
|     case IMAGE_INFO_SPECIFIC_KIND_QCOW2:
|-        visit_type_ImageInfoSpecificQCow2(v, "data", &obj->u.qcow2, &err);
|+        visit_type_q_obj_ImageInfoSpecificQCow2_wrapper_members(v, &obj->u.qcow2, &err);
|         break;
|     case IMAGE_INFO_SPECIFIC_KIND_VMDK:
|-        visit_type_ImageInfoSpecificVmdk(v, "data", &obj->u.vmdk, &err);
|+        visit_type_q_obj_ImageInfoSpecificVmdk_wrapper_members(v, &obj->u.vmdk, &err);
|         break;
|     default:
|         abort();

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1458254921-17042-13-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 12 insertions, 12 deletions

diff --git a/blockdev.c b/blockdev.c
index 85dee5787b..24c886142a 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1247,7 +1247,7 @@ void qmp_blockdev_snapshot_sync(bool has_device, const char *device,
     };
     TransactionAction action = {
         .type = TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC,
-        .u.blockdev_snapshot_sync = &snapshot,
+        .u.blockdev_snapshot_sync.data = &snapshot,
     };
     blockdev_do_action(&action, errp);
 }
@@ -1261,7 +1261,7 @@ void qmp_blockdev_snapshot(const char *node, const char *overlay,
     };
     TransactionAction action = {
         .type = TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT,
-        .u.blockdev_snapshot = &snapshot_data,
+        .u.blockdev_snapshot.data = &snapshot_data,
     };
     blockdev_do_action(&action, errp);
 }
@@ -1276,7 +1276,7 @@ void qmp_blockdev_snapshot_internal_sync(const char *device,
     };
     TransactionAction action = {
         .type = TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC,
-        .u.blockdev_snapshot_internal_sync = &snapshot,
+        .u.blockdev_snapshot_internal_sync.data = &snapshot,
     };
     blockdev_do_action(&action, errp);
 }
@@ -1515,7 +1515,7 @@ static void internal_snapshot_prepare(BlkActionState *common,
 
     g_assert(common->action->type ==
              TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_INTERNAL_SYNC);
-    internal = common->action->u.blockdev_snapshot_internal_sync;
+    internal = common->action->u.blockdev_snapshot_internal_sync.data;
     state = DO_UPCAST(InternalSnapshotState, common, common);
 
     /* 1. parse input */
@@ -1665,7 +1665,7 @@ static void external_snapshot_prepare(BlkActionState *common,
     switch (action->type) {
     case TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT:
         {
-            BlockdevSnapshot *s = action->u.blockdev_snapshot;
+            BlockdevSnapshot *s = action->u.blockdev_snapshot.data;
             device = s->node;
             node_name = s->node;
             new_image_file = NULL;
@@ -1674,7 +1674,7 @@ static void external_snapshot_prepare(BlkActionState *common,
         break;
     case TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC:
         {
-            BlockdevSnapshotSync *s = action->u.blockdev_snapshot_sync;
+            BlockdevSnapshotSync *s = action->u.blockdev_snapshot_sync.data;
             device = s->has_device ? s->device : NULL;
             node_name = s->has_node_name ? s->node_name : NULL;
             new_image_file = s->snapshot_file;
@@ -1723,7 +1723,7 @@ static void external_snapshot_prepare(BlkActionState *common,
     }
 
     if (action->type == TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC) {
-        BlockdevSnapshotSync *s = action->u.blockdev_snapshot_sync;
+        BlockdevSnapshotSync *s = action->u.blockdev_snapshot_sync.data;
         const char *format = s->has_format ? s->format : "qcow2";
         enum NewImageMode mode;
         const char *snapshot_node_name =
@@ -1861,7 +1861,7 @@ static void drive_backup_prepare(BlkActionState *common, Error **errp)
     Error *local_err = NULL;
 
     assert(common->action->type == TRANSACTION_ACTION_KIND_DRIVE_BACKUP);
-    backup = common->action->u.drive_backup;
+    backup = common->action->u.drive_backup.data;
 
     blk = blk_by_name(backup->device);
     if (!blk) {
@@ -1943,7 +1943,7 @@ static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
     Error *local_err = NULL;
 
     assert(common->action->type == TRANSACTION_ACTION_KIND_BLOCKDEV_BACKUP);
-    backup = common->action->u.blockdev_backup;
+    backup = common->action->u.blockdev_backup.data;
 
     blk = blk_by_name(backup->device);
     if (!blk) {
@@ -2029,7 +2029,7 @@ static void block_dirty_bitmap_add_prepare(BlkActionState *common,
         return;
     }
 
-    action = common->action->u.block_dirty_bitmap_add;
+    action = common->action->u.block_dirty_bitmap_add.data;
     /* AIO context taken and released within qmp_block_dirty_bitmap_add */
     qmp_block_dirty_bitmap_add(action->node, action->name,
                                action->has_granularity, action->granularity,
@@ -2048,7 +2048,7 @@ static void block_dirty_bitmap_add_abort(BlkActionState *common)
     BlockDirtyBitmapState *state = DO_UPCAST(BlockDirtyBitmapState,
                                              common, common);
 
-    action = common->action->u.block_dirty_bitmap_add;
+    action = common->action->u.block_dirty_bitmap_add.data;
     /* Should not be able to fail: IF the bitmap was added via .prepare(),
      * then the node reference and bitmap name must have been valid.
      */
@@ -2068,7 +2068,7 @@ static void block_dirty_bitmap_clear_prepare(BlkActionState *common,
         return;
     }
 
-    action = common->action->u.block_dirty_bitmap_clear;
+    action = common->action->u.block_dirty_bitmap_clear.data;
     state->bitmap = block_dirty_bitmap_lookup(action->node,
                                               action->name,
                                               &state->bs,