qapi: enable use of g_autoptr with QAPI types

Currently QAPI generates a type and function for free'ing it:

  typedef struct QCryptoBlockCreateOptions QCryptoBlockCreateOptions;
  void qapi_free_QCryptoBlockCreateOptions(QCryptoBlockCreateOptions *obj);

This is used in the traditional manner:

  QCryptoBlockCreateOptions *opts = NULL;

  opts = g_new0(QCryptoBlockCreateOptions, 1);

  ....do stuff with opts...

  qapi_free_QCryptoBlockCreateOptions(opts);

Since bumping the min glib to 2.48, QEMU has incrementally adopted the
use of g_auto/g_autoptr. This allows the compiler to run a function to
free a variable when it goes out of scope, the benefit being the
compiler can guarantee it is freed in all possible code ptahs.

This benefit is applicable to QAPI types too, and given the seriously
long method names for some qapi_free_XXXX() functions, is much less
typing. This change thus makes the code generator emit:

 G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoBlockCreateOptions,
                              qapi_free_QCryptoBlockCreateOptions)

The above code example now becomes

  g_autoptr(QCryptoBlockCreateOptions) opts = NULL;

  opts = g_new0(QCryptoBlockCreateOptions, 1);

  ....do stuff with opts...

Note, if the local pointer needs to live beyond the scope holding the
variable, then g_steal_pointer can be used. This is useful to return the
pointer to the caller in the success codepath, while letting it be freed
in all error codepaths.

  return g_steal_pointer(&opts);

The crypto/block.h header needs updating to avoid symbol clash now that
the g_autoptr support is a standard QAPI feature.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200723153845.2934357-1-berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
index 69eede6c2831c5739440bd48e9e97d21a3657f3e..f3e7ced212e73d7e378594ee62b91f3b4dfbb9cb 100644 (file)
--- a/docs/devel/qapi-code-gen.txt
+++ b/docs/devel/qapi-code-gen.txt
@@ -1321,6 +1321,7 @@ Example:
     };
 
     void qapi_free_UserDefOne(UserDefOne *obj);
+    G_DEFINE_AUTOPTR_CLEANUP_FUNC(UserDefOne, qapi_free_UserDefOne)
 
     struct UserDefOneList {
         UserDefOneList *next;
@@ -1328,6 +1329,7 @@ Example:
     };
 
     void qapi_free_UserDefOneList(UserDefOneList *obj);
+    G_DEFINE_AUTOPTR_CLEANUP_FUNC(UserDefOneList, qapi_free_UserDefOneList)
 
     struct q_obj_my_command_arg {
         UserDefOneList *arg1;

diff --git a/include/crypto/block.h b/include/crypto/block.h
index d274819791a7039cbe3a3e199204fc9e15c8c64c..7a65e8e402a4e72ad1e6874f1e4b8d3ad0408b2e 100644 (file)
--- a/include/crypto/block.h
+++ b/include/crypto/block.h
@@ -311,7 +311,5 @@ uint64_t qcrypto_block_get_sector_size(QCryptoBlock *block);
 void qcrypto_block_free(QCryptoBlock *block);
 
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoBlock, qcrypto_block_free)
-G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoBlockCreateOptions,
-                              qapi_free_QCryptoBlockCreateOptions)
 
 #endif /* QCRYPTO_BLOCK_H */

diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
index 3ad33af4ee3d43886c75a0085956d26afce08953..3640f17cd674ce10b31c139b80829844cb5bbcb4 100644 (file)
--- a/scripts/qapi/types.py
+++ b/scripts/qapi/types.py
@@ -213,6 +213,7 @@ def gen_type_cleanup_decl(name):
     ret = mcgen('''
 
 void qapi_free_%(c_name)s(%(c_name)s *obj);
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(%(c_name)s, qapi_free_%(c_name)s)
 ''',
                 c_name=c_name(name))
     return ret

diff --git a/tests/test-qobject-input-visitor.c b/tests/test-qobject-input-visitor.c
index 6bacabf063222b62d22c40bd09b1c79b72100fe8..e41b91a2a6fe71646aa74a17181ec93b3ff3cfeb 100644 (file)
--- a/tests/test-qobject-input-visitor.c
+++ b/tests/test-qobject-input-visitor.c
@@ -417,7 +417,7 @@ static void test_visitor_in_struct(TestInputVisitorData *data,
 static void test_visitor_in_struct_nested(TestInputVisitorData *data,
                                           const void *unused)
 {
-    UserDefTwo *udp = NULL;
+    g_autoptr(UserDefTwo) udp = NULL;
     Visitor *v;
 
     v = visitor_input_test_init(data, "{ 'string0': 'string0', "
@@ -433,8 +433,6 @@ static void test_visitor_in_struct_nested(TestInputVisitorData *data,
     g_assert_cmpstr(udp->dict1->dict2->userdef->string, ==, "string");
     g_assert_cmpstr(udp->dict1->dict2->string, ==, "string2");
     g_assert(udp->dict1->has_dict3 == false);
-
-    qapi_free_UserDefTwo(udp);
 }
 
 static void test_visitor_in_list(TestInputVisitorData *data,
@@ -546,7 +544,7 @@ static void test_visitor_in_union_flat(TestInputVisitorData *data,
                                        const void *unused)
 {
     Visitor *v;
-    UserDefFlatUnion *tmp;
+    g_autoptr(UserDefFlatUnion) tmp = NULL;
     UserDefUnionBase *base;
 
     v = visitor_input_test_init(data,
@@ -563,8 +561,6 @@ static void test_visitor_in_union_flat(TestInputVisitorData *data,
 
     base = qapi_UserDefFlatUnion_base(tmp);
     g_assert(&base->enum1 == &tmp->enum1);
-
-    qapi_free_UserDefFlatUnion(tmp);
 }
 
 static void test_visitor_in_alternate(TestInputVisitorData *data,
@@ -690,7 +686,7 @@ static void test_list_union_integer_helper(TestInputVisitorData *data,
                                            const void *unused,
                                            UserDefListUnionKind kind)
 {
-    UserDefListUnion *cvalue = NULL;
+    g_autoptr(UserDefListUnion) cvalue = NULL;
     Visitor *v;
     GString *gstr_list = g_string_new("");
     GString *gstr_union = g_string_new("");
@@ -782,7 +778,6 @@ static void test_list_union_integer_helper(TestInputVisitorData *data,
 
     g_string_free(gstr_union, true);
     g_string_free(gstr_list, true);
-    qapi_free_UserDefListUnion(cvalue);
 }
 
 static void test_visitor_in_list_union_int(TestInputVisitorData *data,
@@ -851,7 +846,7 @@ static void test_visitor_in_list_union_uint64(TestInputVisitorData *data,
 static void test_visitor_in_list_union_bool(TestInputVisitorData *data,
                                             const void *unused)
 {
-    UserDefListUnion *cvalue = NULL;
+    g_autoptr(UserDefListUnion) cvalue = NULL;
     boolList *elem = NULL;
     Visitor *v;
     GString *gstr_list = g_string_new("");
@@ -879,13 +874,12 @@ static void test_visitor_in_list_union_bool(TestInputVisitorData *data,
 
     g_string_free(gstr_union, true);
     g_string_free(gstr_list, true);
-    qapi_free_UserDefListUnion(cvalue);
 }
 
 static void test_visitor_in_list_union_string(TestInputVisitorData *data,
                                               const void *unused)
 {
-    UserDefListUnion *cvalue = NULL;
+    g_autoptr(UserDefListUnion) cvalue = NULL;
     strList *elem = NULL;
     Visitor *v;
     GString *gstr_list = g_string_new("");
@@ -914,7 +908,6 @@ static void test_visitor_in_list_union_string(TestInputVisitorData *data,
 
     g_string_free(gstr_union, true);
     g_string_free(gstr_list, true);
-    qapi_free_UserDefListUnion(cvalue);
 }
 
 #define DOUBLE_STR_MAX 16
@@ -922,7 +915,7 @@ static void test_visitor_in_list_union_string(TestInputVisitorData *data,
 static void test_visitor_in_list_union_number(TestInputVisitorData *data,
                                               const void *unused)
 {
-    UserDefListUnion *cvalue = NULL;
+    g_autoptr(UserDefListUnion) cvalue = NULL;
     numberList *elem = NULL;
     Visitor *v;
     GString *gstr_list = g_string_new("");
@@ -957,7 +950,6 @@ static void test_visitor_in_list_union_number(TestInputVisitorData *data,
 
     g_string_free(gstr_union, true);
     g_string_free(gstr_list, true);
-    qapi_free_UserDefListUnion(cvalue);
 }
 
 static void input_visitor_test_add(const char *testpath,
@@ -1253,7 +1245,7 @@ static void test_visitor_in_fail_alternate(TestInputVisitorData *data,
 static void do_test_visitor_in_qmp_introspect(TestInputVisitorData *data,
                                               const QLitObject *qlit)
 {
-    SchemaInfoList *schema = NULL;
+    g_autoptr(SchemaInfoList) schema = NULL;
     QObject *obj = qobject_from_qlit(qlit);
     Visitor *v;
 
@@ -1262,7 +1254,6 @@ static void do_test_visitor_in_qmp_introspect(TestInputVisitorData *data,
     visit_type_SchemaInfoList(v, NULL, &schema, &error_abort);
     g_assert(schema);
 
-    qapi_free_SchemaInfoList(schema);
     qobject_unref(obj);
     visit_free(v);
 }