[Qemu-devel] [PATCH v13 14/18] qapi-commands: Wrap argument visit in visit_start_struct

[Eric Blake <eblake@redhat.com>]

The qmp-input visitor was playing rather fast and loose: when
visiting a QDict, you could grab members of the root dictionary
without first pushing into the dict.  But we are about to tighten
the input visitor, at which point the generated marshal code
MUST follow the same paradigms as everyone else, of pushing into
the struct before grabbing its keys, because the value of 'name'
should be ignored on the top-level visit.

Generated code grows as follows:

|@@ -515,7 +695,15 @@ void qmp_marshal_blockdev_backup(QDict *
|     BlockdevBackup qapi = {0};
|
|     v = qmp_input_get_visitor(qiv);
|+    visit_start_struct(v, NULL, NULL, 0, &err);
|+    if (err) {
|+        goto out;
|+    }
|     visit_type_BlockdevBackup_members(v, &qapi, &err);
|+    if (!err) {
|+        visit_check_struct(v, &err);
|+    }
|+    visit_end_struct(v);
|     if (err) {
|         goto out;
|     }
|@@ -527,7 +715,9 @@ out:
|     qmp_input_visitor_cleanup(qiv);
|     qdv = qapi_dealloc_visitor_new();
|     v = qapi_dealloc_get_visitor(qdv);
|+    visit_start_struct(v, NULL, NULL, 0, NULL);
|     visit_type_BlockdevBackup_members(v, &qapi, NULL);
|+    visit_end_struct(v);
|     qapi_dealloc_visitor_cleanup(qdv);
| }

Note that this change could also make it possible for the
marshalling code to automatically detect excess input at the top
level, and not just in nested dictionaries.  However, that checking
is not currently useful (and we rely on the manual checking in
monitor.c:qmp_check_client_args() instead) as long as qmp-commands.hx
uses .args_type, and as long as we have 'name:O' as an arg-type that
explicitly allows unknown top-level keys because we haven't yet
converted 'device_add' and 'netdev_add' to introspectible use of
'any'.

Signed-off-by: Eric Blake <eblake@redhat.com>

---
v13: rebase to earlier patches
v12: new patch
---
 scripts/qapi-commands.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 710e853..8b1a676 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -121,7 +121,15 @@ def gen_marshal(name, arg_type, ret_type):
     %(c_name)s qapi = {0};

     v = qmp_input_get_visitor(qiv);
+    visit_start_struct(v, NULL, NULL, 0, &err);
+    if (err) {
+        goto out;
+    }
     visit_type_%(c_name)s_members(v, &qapi, &err);
+    if (!err) {
+        visit_check_struct(v, &err);
+    }
+    visit_end_struct(v);
     if (err) {
         goto out;
     }
@@ -150,7 +158,9 @@ out:
     qmp_input_visitor_cleanup(qiv);
     qdv = qapi_dealloc_visitor_new();
     v = qapi_dealloc_get_visitor(qdv);
+    visit_start_struct(v, NULL, NULL, 0, NULL);
     visit_type_%(c_name)s_members(v, &qapi, NULL);
+    visit_end_struct(v);
     qapi_dealloc_visitor_cleanup(qdv);
 ''',
                      c_name=arg_type.c_name())
-- 
2.5.0