* Peter Xu (pet...@redhat.com) wrote: > It is error prone to use VMSTATE_UNUSED*() sometimes especially when > the size of the migration stream of the field is not the same as the > size of the structure (boolean is one example). Comment it well so > people will be aware of this when people want to use it. > > Signed-off-by: Peter Xu <pet...@redhat.com>
Queued > --- > include/migration/vmstate.h | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > index a668ec75b8..9224370ed5 100644 > --- a/include/migration/vmstate.h > +++ b/include/migration/vmstate.h > @@ -1035,6 +1035,20 @@ extern const VMStateInfo vmstate_info_qtailq; > #define VMSTATE_BUFFER_UNSAFE(_field, _state, _version, _size) \ > VMSTATE_BUFFER_UNSAFE_INFO(_field, _state, _version, > vmstate_info_buffer, _size) > > +/* > + * These VMSTATE_UNUSED*() macros can be used to fill in the holes > + * when some of the vmstate fields are obsolete to be compatible with > + * migrations between new/old binaries. > + * > + * CAUTION: when using any of the VMSTATE_UNUSED*() macros please be > + * sure that the size passed in is the size that was actually *sent* > + * rather than the size of the *structure*. One example is the > + * boolean type - the size of the structure can vary depending on the > + * definition of boolean, however the size we actually sent is always > + * 1 byte (please refer to implementation of VMSTATE_BOOL_V and > + * vmstate_info_bool). So here we should always pass in size==1 > + * rather than size==sizeof(bool). > + */ > #define VMSTATE_UNUSED_V(_v, _size) \ > VMSTATE_UNUSED_BUFFER(NULL, _v, _size) > > -- > 2.17.1 > > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
