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From e25370368e98e6d8766e50b7f13e3543e1c3ef9b Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Mon, 9 Sep 2013 14:28:12 +0200
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Subject: [PATCH 21/38] qapi: Flat unions with arbitrary discriminator
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <1378736903-18489-22-git-send-email-kwolf@redhat.com>
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Patchwork-id: 54208
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O-Subject: [RHEL-7.0 qemu-kvm PATCH 21/32] qapi: Flat unions with arbitrary discriminator
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Bugzilla: 1005818
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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Bugzilla: 1005818
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Instead of the rather verbose syntax that distinguishes base and
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subclass fields...
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  { "type": "file",
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    "read-only": true,
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    "data": {
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        "filename": "test"
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    } }
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...we can now have both in the same namespace, allowing a more direct
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mapping of the command line, and moving fields between the common base
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and subclasses without breaking the API:
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  { "driver": "file",
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    "read-only": true,
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    "filename": "test" }
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 50f2bdc75c5ee00617ad874c9ceac2cea660aa1e)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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 docs/qapi-code-gen.txt | 22 ++++++++++++
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 scripts/qapi-types.py  | 11 ++++--
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 scripts/qapi-visit.py  | 90 +++++++++++++++++++++++++++++++++++++-------------
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 3 files changed, 98 insertions(+), 25 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 docs/qapi-code-gen.txt |   22 ++++++++++++
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 scripts/qapi-types.py  |   11 +++++-
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 scripts/qapi-visit.py  |   90 +++++++++++++++++++++++++++++++++++------------
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 3 files changed, 98 insertions(+), 25 deletions(-)
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diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
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index f6f8d33..11f19cf 100644
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--- a/docs/qapi-code-gen.txt
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+++ b/docs/qapi-code-gen.txt
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@@ -103,6 +103,28 @@ And it looks like this on the wire:
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    "data" : { "backing-file": "/some/place/my-image",
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               "lazy-refcounts": true } }
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+
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+Flat union types avoid the nesting on the wire. They are used whenever a
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+specific field of the base type is declared as the discriminator ('type' is
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+then no longer generated). The discriminator must always be a string field.
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+The above example can then be modified as follows:
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+
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+ { 'type': 'BlockdevCommonOptions',
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+   'data': { 'driver': 'str', 'readonly': 'bool' } }
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+ { 'union': 'BlockdevOptions',
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+   'base': 'BlockdevCommonOptions',
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+   'discriminator': 'driver',
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+   'data': { 'raw': 'RawOptions',
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+             'qcow2': 'Qcow2Options' } }
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+
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+Resulting in this JSON object:
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+
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+ { "driver": "qcow2",
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+   "readonly": false,
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+   "backing-file": "/some/place/my-image",
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+   "lazy-refcounts": true }
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+
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+
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 === Commands ===
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 Commands are defined by using a list containing three members.  The first
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diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
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index c0684a7..f139bfe 100644
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--- a/scripts/qapi-types.py
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+++ b/scripts/qapi-types.py
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@@ -135,7 +135,9 @@ def generate_union(expr):
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     name = expr['union']
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     typeinfo = expr['data']
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+
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     base = expr.get('base')
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+    discriminator = expr.get('discriminator')
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     ret = mcgen('''
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 struct %(name)s
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@@ -158,8 +160,13 @@ struct %(name)s
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 ''')
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     if base:
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-        struct = find_struct(base)
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-        ret += generate_struct_fields(struct['data'])
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+        base_fields = find_struct(base)['data']
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+        if discriminator:
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+            base_fields = base_fields.copy()
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+            del base_fields[discriminator]
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+        ret += generate_struct_fields(base_fields)
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+    else:
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+        assert not discriminator
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     ret += mcgen('''
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 };
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diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
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index be56ba4..b1c1ad6 100644
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--- a/scripts/qapi-visit.py
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+++ b/scripts/qapi-visit.py
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@@ -17,8 +17,30 @@ import os
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 import getopt
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 import errno
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-def generate_visit_struct_fields(field_prefix, members):
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+def generate_visit_struct_fields(name, field_prefix, fn_prefix, members):
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+    substructs = []
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     ret = ''
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+    full_name = name if not fn_prefix else "%s_%s" % (name, fn_prefix)
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+
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+    for argname, argentry, optional, structured in parse_args(members):
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+        if structured:
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+            if not fn_prefix:
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+                nested_fn_prefix = argname
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+            else:
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+                nested_fn_prefix = "%s_%s" % (fn_prefix, argname)
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+
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+            nested_field_prefix = "%s%s." % (field_prefix, argname)
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+            ret += generate_visit_struct_fields(name, nested_field_prefix,
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+                                                nested_fn_prefix, argentry)
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+
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+    ret += mcgen('''
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+
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+static void visit_type_%(full_name)s_fields(Visitor *m, %(name)s ** obj, Error **errp)
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+{
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+    Error *err = NULL;
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+''',
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+        name=name, full_name=full_name)
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+    push_indent()
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     for argname, argentry, optional, structured in parse_args(members):
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         if optional:
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@@ -31,7 +53,7 @@ if (obj && (*obj)->%(prefix)shas_%(c_name)s) {
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             push_indent()
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         if structured:
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-            ret += generate_visit_struct_body(field_prefix + argname, argname, argentry)
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+            ret += generate_visit_struct_body(full_name, argname, argentry)
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         else:
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             ret += mcgen('''
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 visit_type_%(type)s(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, "%(name)s", &err;;
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@@ -47,6 +69,12 @@ visit_type_%(type)s(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, "%(name)s",
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 visit_end_optional(m, &err;;
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 ''')
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+    pop_indent()
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+    ret += mcgen('''
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+
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+    error_propagate(errp, err);
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+}
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+''')
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     return ret
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@@ -56,8 +84,9 @@ if (!error_is_set(errp)) {
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 ''')
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     push_indent()
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+    full_name = name if not field_prefix else "%s_%s" % (field_prefix, name)
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+
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     if len(field_prefix):
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-        field_prefix = field_prefix + "."
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         ret += mcgen('''
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 Error **errp = &err; /* from outer scope */
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 Error *err = NULL;
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@@ -74,20 +103,14 @@ visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(name)s), &err;;
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     ret += mcgen('''
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 if (!err) {
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     if (!obj || *obj) {
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-''')
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-    push_indent()
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-    push_indent()
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-
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-    ret += generate_visit_struct_fields(field_prefix, members)
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-    pop_indent()
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-    ret += mcgen('''
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-    error_propagate(errp, err);
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-    err = NULL;
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-}
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-''')
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+        visit_type_%(name)s_fields(m, obj, &err;;
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+        error_propagate(errp, err);
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+        err = NULL;
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+    }
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+''',
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+        name=full_name)
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     pop_indent()
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-    pop_indent()
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     ret += mcgen('''
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         /* Always call end_struct if start_struct succeeded.  */
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         visit_end_struct(m, &err;;
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@@ -98,7 +121,9 @@ if (!err) {
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     return ret
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 def generate_visit_struct(name, members):
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-    ret = mcgen('''
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+    ret = generate_visit_struct_fields(name, "", "", members)
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+
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+    ret += mcgen('''
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 void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
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 {
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@@ -157,9 +182,17 @@ def generate_visit_union(expr):
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     members = expr['data']
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     base = expr.get('base')
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+    discriminator = expr.get('discriminator')
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     ret = generate_visit_enum('%sKind' % name, members.keys())
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+    if base:
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+        base_fields = find_struct(base)['data']
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+        if discriminator:
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+            base_fields = base_fields.copy()
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+            del base_fields[discriminator]
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+        ret += generate_visit_struct_fields(name, "", "", base_fields)
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+
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     ret += mcgen('''
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 void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
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@@ -179,23 +212,34 @@ void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **
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     push_indent()
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     if base:
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-        struct = find_struct(base)
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-        push_indent()
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-        ret += generate_visit_struct_fields("", struct['data'])
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-        pop_indent()
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+        ret += mcgen('''
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+    visit_type_%(name)s_fields(m, obj, &err;;
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+''',
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+            name=name)
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     pop_indent()
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     ret += mcgen('''
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-        visit_type_%(name)sKind(m, &(*obj)->kind, "type", &err;;
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+        visit_type_%(name)sKind(m, &(*obj)->kind, "%(type)s", &err;;
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         if (!err) {
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             switch ((*obj)->kind) {
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 ''',
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-                 name=name)
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+                 name=name, type="type" if not discriminator else discriminator)
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     for key in members:
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+        if not discriminator:
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+            fmt = 'visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err;;'
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+        else:
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+            fmt = '''visit_start_implicit_struct(m, (void**) &(*obj)->%(c_name)s, sizeof(%(c_type)s), &err;;
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+                if (!err) {
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+                    visit_type_%(c_type)s_fields(m, &(*obj)->%(c_name)s, &err;;
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+                    error_propagate(errp, err);
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+                    err = NULL;
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+                    visit_end_implicit_struct(m, &err;;
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+                }'''
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+
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         ret += mcgen('''
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             case %(abbrev)s_KIND_%(enum)s:
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-                visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err;;
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+                ''' + fmt + '''
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                 break;
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 ''',
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                 abbrev = de_camel_case(name).upper(),
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-- 
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1.7.1
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