[PATCH] conf: force 8 byte alignment for virObjectEvent
We need to be able to cast from virObjectEventPtr to one of
its many subclasses. Some of these subclasses have 8 byte
alignment on 32-bit platforms, but virObjectEventPtr only
has 4 byte alignment.
Previously the virObject base class had 8 byte alignment
but this dropped to 4 byte when converted to inherit from
GObject. This introduces cast alignment warnings on 32-bit:
../../src/conf/domain_event.c: In function 'virDomainEventDispatchDefaultFunc':
../../src/conf/domain_event.c:1656:30: error: cast increases required alignment of target
type [-Werror=cast-align]
1656 | rtcChangeEvent = (virDomainEventRTCChangePtr)event;
| ^
../../src/conf/domain_event.c:1785:34: error: cast increases required alignment of target
type [-Werror=cast-align]
1785 | balloonChangeEvent = (virDomainEventBalloonChangePtr)event;
| ^
../../src/conf/domain_event.c:1896:35: error: cast increases required alignment of target
type [-Werror=cast-align]
1896 | blockThresholdEvent = (virDomainEventBlockThresholdPtr)event;
| ^
../../src/conf/domain_event.c: In function
'virDomainQemuMonitorEventDispatchFunc':
../../src/conf/domain_event.c:1974:24: error: cast increases required alignment of target
type [-Werror=cast-align]
1974 | qemuMonitorEvent = (virDomainQemuMonitorEventPtr)event;
| ^
../../src/conf/domain_event.c: In function 'virDomainQemuMonitorEventFilter':
../../src/conf/domain_event.c:2179:20: error: cast increases required alignment of target
type [-Werror=cast-align]
2179 | monitorEvent = (virDomainQemuMonitorEventPtr) event;
| ^
Forcing 8-byte alignment on virObjectEventPtr removes the
alignment increase during casts to subclasses.
Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com>
---
Technically a build-breaker, but since we don't have any existing
usage of __attribute__((aligned)), I wanted to get a second opinion
on this approach.
One alternative approach would be to switch one of the current "int"
fields in virObjectEvent to "long long".
src/conf/object_event_private.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/conf/object_event_private.h b/src/conf/object_event_private.h
index b31441c53a..126464a9a5 100644
--- a/src/conf/object_event_private.h
+++ b/src/conf/object_event_private.h
@@ -42,7 +42,7 @@ typedef void
virConnectObjectEventGenericCallback cb,
void *cbopaque);
-struct _virObjectEvent {
+struct __attribute__((aligned(4))) _virObjectEvent {
virObject parent;
int eventID;
virObjectMeta meta;
--
2.24.1