Eric Blake writes:
> 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 _obj_ImageInfoSpecificQCow2_wrapper {
> | ImageInfoSpecificQCow2 *data;
> | };
> |
> | struct _obj_ImageInfoSpecificVmdk_wrapper {
> | ImageInfoSpecificVmdk *data;
> | };
> ...
> | struct ImageInfoSpecific {
> | ImageInfoSpecificKind type;
> | union { /* union tag is @type */
> | void *data;
> |-ImageInfoSpecificQCow2 *qcow2;
> |-ImageInfoSpecificVmdk *vmdk;
> |+_obj_ImageInfoSpecificQCow2_wrapper qcow2;
> |+_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__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__obj_ImageInfoSpecificVmdk_wrapper_members(v,
> &obj->u.vmdk, &err);
> | break;
> | default:
> | abort();
>
> Signed-off-by: Eric Blake
>
> ---
> v4: improve commit message, rebase onto exposed implicit types
> [no v3]
> v2: rebase onto s/fields/members/ change, changes in master; pick
> up missing net/ files
> ---
> scripts/qapi.py | 11 --
> scripts/qapi-types.py | 8 +---
> scripts/qapi-visit.py | 22 ++-
> backends/baum.c | 2 +-
> backends/msmouse.c | 2 +-
> block/nbd.c | 6 +--
> block/qcow2.c | 6 +--
> block/vmdk.c| 8 ++--
> blockdev.c | 24 ++--
> hmp.c | 8 ++--
> hw/char/escc.c | 2 +-
> hw/input/hid.c | 8 ++--
> hw/input/ps2.c | 6 +--
> hw/input/virtio-input-hid.c | 8 ++--
> hw/mem/pc-dimm.c| 2 +-
> net/dump.c | 2 +-
> net/hub.c | 2 +-
> net/l2tpv3.c| 2 +-
> net/net.c | 4 +-
> net/netmap.c| 2 +-
> net/slirp.c | 2 +-
> net/socket.c| 2 +-
> net/tap-win32.c | 2 +-
> net/tap.c | 4 +-
> net/vde.c | 2 +-
> net/vhost-user.c| 2 +-
> numa.c | 4 +-
> qemu-char.c | 82
> +
> qemu-nbd.c | 6 +--
> replay/replay-input.c | 44 +++---
> spice-qemu-char.c | 14 ---
> tests/test-io-channel-socket.c | 40 ++--
> tests/test-qmp-commands.c | 2 +-
> tests/test-qmp-input-visitor.c | 25 +++--
> tests/test-qmp-output-visitor.c | 24 ++--
> tpm.c | 2 +-
> ui/console.c| 4 +-
> ui/input-keymap.c | 10 ++---
> ui/input-legacy.c | 8 ++--
> ui/input.c | 34 -
> ui/vnc-auth-sasl.c | 3 +-
> ui/vnc.c| 29 ---
> util/qemu-sockets.c | 35 +-
> 43 files changed, 246 insertions(+), 269 deletions(-)
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index 797ac7a..0574b8b 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -1006,7 +1006,
