[Qemu-devel] [PATCH v10 10/25] qapi: Unbox base members

[Eric Blake]

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 1e6c1616a "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 drops a hack that was
needed for type-safe casting 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:

| static inline SpiceBasicInfo *qapi_SpiceChannel_base(const SpiceChannel *obj)
| {
|-    return (SpiceBasicInfo *)obj->base;
|+    return (SpiceBasicInfo *)obj;
| }

and this in qapi-visit.c:

| 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_SpiceBasiInfo_fields(v, (SpiceBasicInfo **)obj, &err);
|     if (err) {

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 pointer to the base would have
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: Eric Blake <address@hidden>

---
v10: split off some of the cleanups into earlier patches, improve
commit message, don't emit visit_type_FOO_fields out of order,
save positive tests in qapi-schema-tests for later
v9: (no v6-8): hoist from v5 34/46, rebase to master
---
 hmp.c                                         |  6 +++---
 scripts/qapi-types.py                         | 20 ++++++--------------
 scripts/qapi-visit.py                         | 13 ++++---------
 tests/Makefile                                |  1 -
 tests/qapi-schema/struct-base-clash-base.err  |  0
 tests/qapi-schema/struct-base-clash-base.exit |  1 -
 tests/qapi-schema/struct-base-clash-base.json |  9 ---------
 tests/qapi-schema/struct-base-clash-base.out  |  5 -----
 tests/test-qmp-commands.c                     | 15 +++++----------
 tests/test-qmp-event.c                        |  8 ++------
 tests/test-qmp-input-visitor.c                |  4 ++--
 tests/test-qmp-output-visitor.c               | 13 +++++--------
 tests/test-visitor-serialization.c            | 14 ++++++--------
 ui/spice-core.c                               |  9 +++------
 ui/vnc.c                                      | 12 ++++--------
 15 files changed, 40 insertions(+), 90 deletions(-)
 delete mode 100644 tests/qapi-schema/struct-base-clash-base.err
 delete mode 100644 tests/qapi-schema/struct-base-clash-base.exit
 delete mode 100644 tests/qapi-schema/struct-base-clash-base.json
 delete mode 100644 tests/qapi-schema/struct-base-clash-base.out

diff --git a/hmp.c b/hmp.c
index 5048eee..88fd804 100644
--- a/hmp.c
+++ b/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);
diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index ed4a11c..9c51d8f 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -76,16 +76,13 @@ 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;
 ''')
@@ -97,21 +94,17 @@ struct %(c_name)s {
     return ret


-def gen_upcast(name, base, struct):
+def gen_upcast(name, base):
     # C makes const-correctness ugly.  We have to cast away const to let
     # this function work for both const and non-const obj.
-    # TODO Ugly difference between struct and flat union bases
-    member = ''
-    if struct:
-        member = '->base'
     return mcgen('''

 static inline %(base)s *qapi_%(c_name)s_base(const %(c_name)s *obj)
 {
-    return (%(base)s *)obj%(member)s;
+    return (%(base)s *)obj;
 }
 ''',
-                 c_name=c_name(name), base=base.c_name(), member=member)
+                 c_name=c_name(name), base=base.c_name())


 def gen_alternate_qtypes_decl(name):
@@ -286,8 +279,7 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor):
         else:
             self.decl += gen_struct(name, base, members)
         if base:
-            # TODO Drop last param once structs have sane layout
-            self.decl += gen_upcast(name, base, not variants)
+            self.decl += gen_upcast(name, base)
         self._gen_type_cleanup(name)

     def visit_alternate_type(self, name, info, variants):
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 7204ed0..e30062b 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -72,26 +72,21 @@ static void visit_type_implicit_%(c_type)s(Visitor *v, 
%(c_type)s **obj, Error *


 def gen_visit_struct_fields(name, base, members):
-    ret = ''
-
-    if base:
-        ret += gen_visit_implicit_struct(base)
-
     struct_fields_seen.add(name)
-    ret += mcgen('''
+    ret = mcgen('''

 static void visit_type_%(c_name)s_fields(Visitor *v, %(c_name)s **obj, Error 
**errp)
 {
     Error *err = NULL;

 ''',
-                 c_name=c_name(name))
+                c_name=c_name(name))

     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)->')
diff --git a/tests/Makefile b/tests/Makefile
index cc6b24f..9194264 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -322,7 +322,6 @@ 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
diff --git a/tests/qapi-schema/struct-base-clash-base.err 
b/tests/qapi-schema/struct-base-clash-base.err
deleted file mode 100644
index e69de29..0000000
diff --git a/tests/qapi-schema/struct-base-clash-base.exit 
b/tests/qapi-schema/struct-base-clash-base.exit
deleted file mode 100644
index 573541a..0000000
--- a/tests/qapi-schema/struct-base-clash-base.exit
+++ /dev/null
@@ -1 +0,0 @@
-0
diff --git a/tests/qapi-schema/struct-base-clash-base.json 
b/tests/qapi-schema/struct-base-clash-base.json
deleted file mode 100644
index 0c84025..0000000
--- a/tests/qapi-schema/struct-base-clash-base.json
+++ /dev/null
@@ -1,9 +0,0 @@
-# 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' } }
diff --git a/tests/qapi-schema/struct-base-clash-base.out 
b/tests/qapi-schema/struct-base-clash-base.out
deleted file mode 100644
index e69a416..0000000
--- a/tests/qapi-schema/struct-base-clash-base.out
+++ /dev/null
@@ -1,5 +0,0 @@
-object :empty
-object Base
-object Sub
-    base Base
-    member base: str optional=False
diff --git a/tests/test-qmp-commands.c b/tests/test-qmp-commands.c
index bc59835..ea700d8 100644
--- a/tests/test-qmp-commands.c
+++ b/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));
diff --git a/tests/test-qmp-event.c b/tests/test-qmp-event.c
index 28f146d..035c65c 100644
--- a/tests/test-qmp-event.c
+++ b/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;
diff --git a/tests/test-qmp-input-visitor.c b/tests/test-qmp-input-visitor.c
index 8941963..514cfd0 100644
--- a/tests/test-qmp-input-visitor.c
+++ b/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);
diff --git a/tests/test-qmp-output-visitor.c b/tests/test-qmp-output-visitor.c
index c84002e..cfb06bb 100644
--- a/tests/test-qmp-output-visitor.c
+++ b/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;

diff --git a/tests/test-visitor-serialization.c 
b/tests/test-visitor-serialization.c
index fa86cae..634563b 100644
--- a/tests/test-visitor-serialization.c
+++ b/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, ==,
diff --git a/ui/spice-core.c b/ui/spice-core.c
index d43cfbe..6a62d71 100644
--- a/ui/spice-core.c
+++ b/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
@@ -384,16 +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;
diff --git a/ui/vnc.c b/ui/vnc.c
index 9473b32..cec2cee 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -262,7 +262,6 @@ 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,
                                          qapi_VncServerInfo_base(info), &err);
     info->has_auth = true;
@@ -301,7 +300,6 @@ 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,
                                          qapi_VncClientInfo_base(client->info),
                                          &err);
@@ -319,7 +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) {
@@ -364,11 +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);
-- 
2.4.3