qapi: Unbox base members

Rather than storing a base class as a pointer to a box, just
store the fields of that base class in the same order, so that
a child struct can be directly cast to its parent.  This gives
less malloc overhead, less pointer dereferencing, and even less
generated code.  Compare to the earlier commit 1e6c1616 "qapi:
Generate a nicer struct for flat unions" (although that patch
had fewer places to change, as less of qemu was directly using
qapi structs for flat unions).  It also allows us to turn on
automatic type-safe wrappers for upcasting to the base class
of a struct.

Changes to the generated code look like this in qapi-types.h:

| struct SpiceChannel {
|-    SpiceBasicInfo *base;
|+    /* Members inherited from SpiceBasicInfo: */
|+    char *host;
|+    char *port;
|+    NetworkAddressFamily family;
|+    /* Own members: */
|     int64_t connection_id;

as well as additional upcast functions like qapi_SpiceChannel_base().
Meanwhile, changes to qapi-visit.c look like:

| static void visit_type_SpiceChannel_fields(Visitor *v, SpiceChannel **obj, Error **errp)
| {
|     Error *err = NULL;
|
|-    visit_type_implicit_SpiceBasicInfo(v, &(*obj)->base, &err);
|+    visit_type_SpiceBasicInfo_fields(v, (SpiceBasicInfo **)obj, &err);
|     if (err) {

(the cast is necessary, since our upcast wrappers only deal with a
single pointer, not pointer-to-pointer); plus the wholesale
elimination of some now-unused visit_type_implicit_FOO() functions.

Without boxing, the corner case of one empty struct having
another empty struct as its base type now requires inserting a
dummy member (previously, the 'Base *base' member sufficed).

And now that we no longer consume a 'base' member in the generated
C struct, we can delete the former negative struct-base-clash-base
test.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1445898903-12082-11-git-send-email-eblake@redhat.com>
[Commit message tweaked slightly]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

hmp.c

@@ -569,8 +569,8 @@ void hmp_info_vnc(Monitor *mon, const QDict *qdict)
         for (client = info->clients; client; client = client->next) {
             monitor_printf(mon, "Client:\n");
             monitor_printf(mon, "     address: %s:%s\n",
-                           client->value->base->host,
-                           client->value->base->service);
+                           client->value->host,
+                           client->value->service);
             monitor_printf(mon, "  x509_dname: %s\n",
                            client->value->x509_dname ?
                            client->value->x509_dname : "none");
@@ -638,7 +638,7 @@ void hmp_info_spice(Monitor *mon, const QDict *qdict)
         for (chan = info->channels; chan; chan = chan->next) {
             monitor_printf(mon, "Channel:\n");
             monitor_printf(mon, "     address: %s:%s%s\n",
-                           chan->value->base->host, chan->value->base->port,
+                           chan->value->host, chan->value->port,
                            chan->value->tls ? " [tls]" : "");
             monitor_printf(mon, "     session: %" PRId64 "\n",
                            chan->value->connection_id);

scripts/qapi-types.py

@@ -77,16 +77,13 @@ struct %(c_name)s {
 ''',
                 c_name=c_name(name))
 
-    if base:
-        ret += gen_struct_field('base', base, False)
-
-    ret += gen_struct_fields(members)
+    ret += gen_struct_fields(members, base)
 
     # Make sure that all structs have at least one field; this avoids
     # potential issues with attempting to malloc space for zero-length
     # structs in C, and also incompatibility with C++ (where an empty
     # struct is size 1).
-    if not base and not members:
+    if not (base and base.members) and not members:
         ret += mcgen('''
     char qapi_dummy_field_for_empty_struct;
 ''')
@@ -280,11 +277,10 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor):
         if variants:
             assert not members      # not implemented
             self.decl += gen_union(name, base, variants)
-            # TODO Use gen_upcast on structs too, once they have sane layout
-            if base:
-                self.decl += gen_upcast(name, base)
         else:
             self.decl += gen_struct(name, base, members)
+        if base:
+            self.decl += gen_upcast(name, base)
         self._gen_type_cleanup(name)
 
     def visit_alternate_type(self, name, info, variants):

scripts/qapi-visit.py

@@ -72,13 +72,12 @@ static void visit_type_implicit_%(c_type)s(Visitor *v, %(c_type)s **obj, Error *
 
 
 def gen_visit_struct_fields(name, base, members):
-    struct_fields_seen.add(name)
-
     ret = ''
 
     if base:
-        ret += gen_visit_implicit_struct(base)
+        ret += gen_visit_fields_decl(base)
 
+    struct_fields_seen.add(name)
     ret += mcgen('''
 
 static void visit_type_%(c_name)s_fields(Visitor *v, %(c_name)s **obj, Error **errp)
@@ -90,9 +89,9 @@ static void visit_type_%(c_name)s_fields(Visitor *v, %(c_name)s **obj, Error **e
 
     if base:
         ret += mcgen('''
-    visit_type_implicit_%(c_type)s(v, &(*obj)->%(c_name)s, &err);
+    visit_type_%(c_type)s_fields(v, (%(c_type)s **)obj, &err);
 ''',
-                     c_type=base.c_name(), c_name=c_name('base'))
+                     c_type=base.c_name())
         ret += gen_err_check()
 
     ret += gen_visit_fields(members, prefix='(*obj)->')

tests/Makefile

@@ -325,7 +325,6 @@ qapi-schema += returns-array-bad.json
 qapi-schema += returns-dict.json
 qapi-schema += returns-unknown.json
 qapi-schema += returns-whitelist.json
-qapi-schema += struct-base-clash-base.json
 qapi-schema += struct-base-clash-deep.json
 qapi-schema += struct-base-clash.json
 qapi-schema += struct-data-invalid.json

tests/qapi-schema/struct-base-clash-base.exit

-0

tests/qapi-schema/struct-base-clash-base.json

-# Struct member 'base'
-# FIXME: this parses, but then fails to compile due to a duplicate 'base'
-# (one explicit in QMP, the other used to box the base class members).
-# We should either reject the collision at parse time, or change the
-# generated struct to allow this to compile.
-{ 'struct': 'Base', 'data': {} }
-{ 'struct': 'Sub',
-  'base': 'Base',
-  'data': { 'base': 'str' } }

tests/qapi-schema/struct-base-clash-base.out

-object :empty
-object Base
-object Sub
-    base Base
-    member base: str optional=False

tests/test-qmp-commands.c

@@ -25,11 +25,9 @@ UserDefTwo *qmp_user_def_cmd2(UserDefOne *ud1a,
     UserDefOne *ud1d = g_malloc0(sizeof(UserDefOne));
 
     ud1c->string = strdup(ud1a->string);
-    ud1c->base = g_new0(UserDefZero, 1);
-    ud1c->base->integer = ud1a->base->integer;
+    ud1c->integer = ud1a->integer;
     ud1d->string = strdup(has_udb1 ? ud1b->string : "blah0");
-    ud1d->base = g_new0(UserDefZero, 1);
-    ud1d->base->integer = has_udb1 ? ud1b->base->integer : 0;
+    ud1d->integer = has_udb1 ? ud1b->integer : 0;
 
     ret = g_new0(UserDefTwo, 1);
     ret->string0 = strdup("blah1");
@@ -176,20 +174,17 @@ static void test_dealloc_types(void)
     UserDefOneList *ud1list;
 
     ud1test = g_malloc0(sizeof(UserDefOne));
-    ud1test->base = g_new0(UserDefZero, 1);
-    ud1test->base->integer = 42;
+    ud1test->integer = 42;
     ud1test->string = g_strdup("hi there 42");
 
     qapi_free_UserDefOne(ud1test);
 
     ud1a = g_malloc0(sizeof(UserDefOne));
-    ud1a->base = g_new0(UserDefZero, 1);
-    ud1a->base->integer = 43;
+    ud1a->integer = 43;
     ud1a->string = g_strdup("hi there 43");
 
     ud1b = g_malloc0(sizeof(UserDefOne));
-    ud1b->base = g_new0(UserDefZero, 1);
-    ud1b->base->integer = 44;
+    ud1b->integer = 44;
     ud1b->string = g_strdup("hi there 44");
 
     ud1list = g_malloc0(sizeof(UserDefOneList));

tests/test-qmp-event.c

@@ -179,9 +179,7 @@ static void test_event_c(TestEventData *data,
     QDict *d, *d_data, *d_b;
 
     UserDefOne b;
-    UserDefZero z;
-    z.integer = 2;
-    b.base = &z;
+    b.integer = 2;
     b.string = g_strdup("test1");
     b.has_enum1 = false;
 
@@ -209,11 +207,9 @@ static void test_event_d(TestEventData *data,
 {
     UserDefOne struct1;
     EventStructOne a;
-    UserDefZero z;
     QDict *d, *d_data, *d_a, *d_struct1;
 
-    z.integer = 2;
-    struct1.base = &z;
+    struct1.integer = 2;
     struct1.string = g_strdup("test1");
     struct1.has_enum1 = true;
     struct1.enum1 = ENUM_ONE_VALUE1;

tests/test-qmp-input-visitor.c

@@ -262,7 +262,7 @@ static void test_visitor_in_struct_nested(TestInputVisitorData *data,
 
     check_and_free_str(udp->string0, "string0");
     check_and_free_str(udp->dict1->string1, "string1");
-    g_assert_cmpint(udp->dict1->dict2->userdef->base->integer, ==, 42);
+    g_assert_cmpint(udp->dict1->dict2->userdef->integer, ==, 42);
     check_and_free_str(udp->dict1->dict2->userdef->string, "string");
     check_and_free_str(udp->dict1->dict2->string, "string2");
     g_assert(udp->dict1->has_dict3 == false);
@@ -292,7 +292,7 @@ static void test_visitor_in_list(TestInputVisitorData *data,
 
         snprintf(string, sizeof(string), "string%d", i);
         g_assert_cmpstr(item->value->string, ==, string);
-        g_assert_cmpint(item->value->base->integer, ==, 42 + i);
+        g_assert_cmpint(item->value->integer, ==, 42 + i);
     }
 
     qapi_free_UserDefOneList(head);

tests/test-qmp-output-visitor.c

@@ -250,16 +250,14 @@ static void test_visitor_out_struct_nested(TestOutputVisitorData *data,
     ud2->dict1->dict2 = g_malloc0(sizeof(*ud2->dict1->dict2));
     ud2->dict1->dict2->userdef = g_new0(UserDefOne, 1);
     ud2->dict1->dict2->userdef->string = g_strdup(string);
-    ud2->dict1->dict2->userdef->base = g_new0(UserDefZero, 1);
-    ud2->dict1->dict2->userdef->base->integer = value;
+    ud2->dict1->dict2->userdef->integer = value;
     ud2->dict1->dict2->string = g_strdup(strings[2]);
 
     ud2->dict1->dict3 = g_malloc0(sizeof(*ud2->dict1->dict3));
     ud2->dict1->has_dict3 = true;
     ud2->dict1->dict3->userdef = g_new0(UserDefOne, 1);
     ud2->dict1->dict3->userdef->string = g_strdup(string);
-    ud2->dict1->dict3->userdef->base = g_new0(UserDefZero, 1);
-    ud2->dict1->dict3->userdef->base->integer = value;
+    ud2->dict1->dict3->userdef->integer = value;
     ud2->dict1->dict3->string = g_strdup(strings[3]);
 
     visit_type_UserDefTwo(data->ov, &ud2, "unused", &err);
@@ -301,8 +299,8 @@ static void test_visitor_out_struct_errors(TestOutputVisitorData *data,
                                            const void *unused)
 {
     EnumOne bad_values[] = { ENUM_ONE_MAX, -1 };
-    UserDefZero b;
-    UserDefOne u = { .base = &b }, *pu = &u;
+    UserDefOne u = {0};
+    UserDefOne *pu = &u;
     Error *err;
     int i;
 
@@ -416,8 +414,7 @@ static void test_visitor_out_list_qapi_free(TestOutputVisitorData *data,
         p->value->dict1->dict2 = g_new0(UserDefTwoDictDict, 1);
         p->value->dict1->dict2->userdef = g_new0(UserDefOne, 1);
         p->value->dict1->dict2->userdef->string = g_strdup(string);
-        p->value->dict1->dict2->userdef->base = g_new0(UserDefZero, 1);
-        p->value->dict1->dict2->userdef->base->integer = 42;
+        p->value->dict1->dict2->userdef->integer = 42;
         p->value->dict1->dict2->string = g_strdup(string);
         p->value->dict1->has_dict3 = false;
 

tests/test-visitor-serialization.c

@@ -258,15 +258,13 @@ static UserDefTwo *nested_struct_create(void)
     udnp->dict1->string1 = strdup("test_string1");
     udnp->dict1->dict2 = g_malloc0(sizeof(*udnp->dict1->dict2));
     udnp->dict1->dict2->userdef = g_new0(UserDefOne, 1);
-    udnp->dict1->dict2->userdef->base = g_new0(UserDefZero, 1);
-    udnp->dict1->dict2->userdef->base->integer = 42;
+    udnp->dict1->dict2->userdef->integer = 42;
     udnp->dict1->dict2->userdef->string = strdup("test_string");
     udnp->dict1->dict2->string = strdup("test_string2");
     udnp->dict1->dict3 = g_malloc0(sizeof(*udnp->dict1->dict3));
     udnp->dict1->has_dict3 = true;
     udnp->dict1->dict3->userdef = g_new0(UserDefOne, 1);
-    udnp->dict1->dict3->userdef->base = g_new0(UserDefZero, 1);
-    udnp->dict1->dict3->userdef->base->integer = 43;
+    udnp->dict1->dict3->userdef->integer = 43;
     udnp->dict1->dict3->userdef->string = strdup("test_string");
     udnp->dict1->dict3->string = strdup("test_string3");
     return udnp;
@@ -278,15 +276,15 @@ static void nested_struct_compare(UserDefTwo *udnp1, UserDefTwo *udnp2)
     g_assert(udnp2);
     g_assert_cmpstr(udnp1->string0, ==, udnp2->string0);
     g_assert_cmpstr(udnp1->dict1->string1, ==, udnp2->dict1->string1);
-    g_assert_cmpint(udnp1->dict1->dict2->userdef->base->integer, ==,
-                    udnp2->dict1->dict2->userdef->base->integer);
+    g_assert_cmpint(udnp1->dict1->dict2->userdef->integer, ==,
+                    udnp2->dict1->dict2->userdef->integer);
     g_assert_cmpstr(udnp1->dict1->dict2->userdef->string, ==,
                     udnp2->dict1->dict2->userdef->string);
     g_assert_cmpstr(udnp1->dict1->dict2->string, ==,
                     udnp2->dict1->dict2->string);
     g_assert(udnp1->dict1->has_dict3 == udnp2->dict1->has_dict3);
-    g_assert_cmpint(udnp1->dict1->dict3->userdef->base->integer, ==,
-                    udnp2->dict1->dict3->userdef->base->integer);
+    g_assert_cmpint(udnp1->dict1->dict3->userdef->integer, ==,
+                    udnp2->dict1->dict3->userdef->integer);
     g_assert_cmpstr(udnp1->dict1->dict3->userdef->string, ==,
                     udnp2->dict1->dict3->userdef->string);
     g_assert_cmpstr(udnp1->dict1->dict3->string, ==,

ui/spice-core.c

@@ -200,8 +200,6 @@ static void channel_event(int event, SpiceChannelEventInfo *info)
 {
     SpiceServerInfo *server = g_malloc0(sizeof(*server));
     SpiceChannel *client = g_malloc0(sizeof(*client));
-    server->base = g_malloc0(sizeof(*server->base));
-    client->base = g_malloc0(sizeof(*client->base));
 
     /*
      * Spice server might have called us from spice worker thread
@@ -218,9 +216,11 @@ static void channel_event(int event, SpiceChannelEventInfo *info)
     }
 
     if (info->flags & SPICE_CHANNEL_EVENT_FLAG_ADDR_EXT) {
-        add_addr_info(client->base, (struct sockaddr *)&info->paddr_ext,
+        add_addr_info(qapi_SpiceChannel_base(client),
+                      (struct sockaddr *)&info->paddr_ext,
                       info->plen_ext);
-        add_addr_info(server->base, (struct sockaddr *)&info->laddr_ext,
+        add_addr_info(qapi_SpiceServerInfo_base(server),
+                      (struct sockaddr *)&info->laddr_ext,
                       info->llen_ext);
     } else {
         error_report("spice: %s, extended address is expected",
@@ -229,7 +229,9 @@ static void channel_event(int event, SpiceChannelEventInfo *info)
 
     switch (event) {
     case SPICE_CHANNEL_EVENT_CONNECTED:
-        qapi_event_send_spice_connected(server->base, client->base, &error_abort);
+        qapi_event_send_spice_connected(qapi_SpiceServerInfo_base(server),
+                                        qapi_SpiceChannel_base(client),
+                                        &error_abort);
         break;
     case SPICE_CHANNEL_EVENT_INITIALIZED:
         if (auth) {
@@ -242,7 +244,9 @@ static void channel_event(int event, SpiceChannelEventInfo *info)
         break;
     case SPICE_CHANNEL_EVENT_DISCONNECTED:
         channel_list_del(info);
-        qapi_event_send_spice_disconnected(server->base, client->base, &error_abort);
+        qapi_event_send_spice_disconnected(qapi_SpiceServerInfo_base(server),
+                                           qapi_SpiceChannel_base(client),
+                                           &error_abort);
         break;
     default:
         break;
@@ -378,16 +382,15 @@ static SpiceChannelList *qmp_query_spice_channels(void)
 
         chan = g_malloc0(sizeof(*chan));
         chan->value = g_malloc0(sizeof(*chan->value));
-        chan->value->base = g_malloc0(sizeof(*chan->value->base));
 
         paddr = (struct sockaddr *)&item->info->paddr_ext;
         plen = item->info->plen_ext;
         getnameinfo(paddr, plen,
                     host, sizeof(host), port, sizeof(port),
                     NI_NUMERICHOST | NI_NUMERICSERV);
-        chan->value->base->host = g_strdup(host);
-        chan->value->base->port = g_strdup(port);
-        chan->value->base->family = inet_netfamily(paddr->sa_family);
+        chan->value->host = g_strdup(host);
+        chan->value->port = g_strdup(port);
+        chan->value->family = inet_netfamily(paddr->sa_family);
 
         chan->value->connection_id = item->info->connection_id;
         chan->value->channel_type = item->info->type;

ui/vnc.c

@@ -262,8 +262,8 @@ static VncServerInfo *vnc_server_info_get(VncDisplay *vd)
     Error *err = NULL;
 
     info = g_malloc(sizeof(*info));
-    info->base = g_malloc(sizeof(*info->base));
-    vnc_init_basic_info_from_server_addr(vd->lsock, info->base, &err);
+    vnc_init_basic_info_from_server_addr(vd->lsock,
+                                         qapi_VncServerInfo_base(info), &err);
     info->has_auth = true;
     info->auth = g_strdup(vnc_auth_name(vd));
     if (err) {
@@ -300,8 +300,8 @@ static void vnc_client_cache_addr(VncState *client)
     Error *err = NULL;
 
     client->info = g_malloc0(sizeof(*client->info));
-    client->info->base = g_malloc0(sizeof(*client->info->base));
-    vnc_init_basic_info_from_remote_addr(client->csock, client->info->base,
+    vnc_init_basic_info_from_remote_addr(client->csock,
+                                         qapi_VncClientInfo_base(client->info),
                                          &err);
     if (err) {
         qapi_free_VncClientInfo(client->info);
@@ -317,7 +317,6 @@ static void vnc_qmp_event(VncState *vs, QAPIEvent event)
     if (!vs->info) {
         return;
     }
-    g_assert(vs->info->base);
 
     si = vnc_server_info_get(vs->vd);
     if (!si) {
@@ -326,7 +325,8 @@ static void vnc_qmp_event(VncState *vs, QAPIEvent event)
 
     switch (event) {
     case QAPI_EVENT_VNC_CONNECTED:
-        qapi_event_send_vnc_connected(si, vs->info->base, &error_abort);
+        qapi_event_send_vnc_connected(si, qapi_VncClientInfo_base(vs->info),
+                                      &error_abort);
         break;
     case QAPI_EVENT_VNC_INITIALIZED:
         qapi_event_send_vnc_initialized(si, vs->info, &error_abort);
@@ -361,11 +361,10 @@ static VncClientInfo *qmp_query_vnc_client(const VncState *client)
     }
 
     info = g_malloc0(sizeof(*info));
-    info->base = g_malloc0(sizeof(*info->base));
-    info->base->host = g_strdup(host);
-    info->base->service = g_strdup(serv);
-    info->base->family = inet_netfamily(sa.ss_family);
-    info->base->websocket = client->websocket;
+    info->host = g_strdup(host);
+    info->service = g_strdup(serv);
+    info->family = inet_netfamily(sa.ss_family);
+    info->websocket = client->websocket;
 
     if (client->tls) {
         info->x509_dname = qcrypto_tls_session_get_peer_name(client->tls);