qom: Clean up object_property_get_enum()'s error value

object_property_get_enum() is the only object_property_FOO() that is
documented to return an undefined value on error.  It does no such
thing, actually: it returns 0 on some errors, and -1 on others.

Needlessly complicated.  Always return -1 on error, and adjust the
contract.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200917125540.597786-2-armbru@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

3 files changed, 8 insertions, 6 deletions

diff --git a/include/qom/object.h b/include/qom/object.h
index 6c0d424..494827b 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1687,9 +1687,9 @@ uint64_t object_property_get_uint(Object *obj, const char *name,
  * @typename: the name of the enum data type
  * @errp: returns an error if this function fails
  *
- * Returns: the value of the property, converted to an integer, or
- * undefined if an error occurs (including when the property value is not
- * an enum).
+ * Returns: the value of the property, converted to an integer (which
+ * can't be negative), or -1 on error (including when the property
+ * value is not an enum).
  */
 int object_property_get_enum(Object *obj, const char *name,
                              const char *typename, Error **errp);
diff --git a/qom/object.c b/qom/object.c
index 387efb2..cecad35 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1564,21 +1564,21 @@ int object_property_get_enum(Object *obj, const char *name,
     EnumProperty *enumprop;
 
     if (prop == NULL) {
-        return 0;
+        return -1;
     }
 
     if (!g_str_equal(prop->type, typename)) {
         error_setg(errp, "Property %s on %s is not '%s' enum type",
                    name, object_class_get_name(
                        object_get_class(obj)), typename);
-        return 0;
+        return -1;
     }
 
     enumprop = prop->opaque;
 
     str = object_property_get_str(obj, name, errp);
     if (!str) {
-        return 0;
+        return -1;
     }
 
     ret = qapi_enum_parse(enumprop->lookup, str, -1, errp);
diff --git a/tests/check-qom-proplist.c b/tests/check-qom-proplist.c
index 1571606..1b76581 100644
--- a/tests/check-qom-proplist.c
+++ b/tests/check-qom-proplist.c
@@ -491,6 +491,7 @@ static void test_dummy_getenum(void)
                                    "av",
                                    "BadAnimal",
                                    &err);
+    g_assert(val == -1);
     error_free_or_abort(&err);
 
     /* A non-enum property name */
@@ -498,6 +499,7 @@ static void test_dummy_getenum(void)
                                    "iv",
                                    "DummyAnimal",
                                    &err);
+    g_assert(val == -1);
     error_free_or_abort(&err);
 
     object_unparent(OBJECT(dobj));