On 06/23/2016 01:31 AM, Eric Blake wrote:
On 06/22/2016 04:19 AM, Paolo Bonzini wrote:
On 22/06/2016 12:12, Changlong Xie wrote:
commit/mirror/stream/backup use block_job_create(..., cb,..) to create
relevant blockjob. When they finished, these jobs will invoke
block_job_completed, then invoke job->cb() unconditionally. So i think
we need this to avoid segment fault. Actually backup has implemented this.
So this suggests that the right place to put the assertion would be
block_job_create. But it's even better to add a
#define QEMU_NONNULL __attribute__((__nonnull__))
to include/qemu/compiler.h and declare the arguments as non-null.
Or alternatively fix things to only invoke job->cb() if it is non-NULL,
so that callers don't have to pass in a no-op callback just to appease a
non-NULL attribute.
Is there any reason, that we should invoke job->cb() unconditionally
without nonnull check? There is no relevant clue in the historical
commit messages. If yes, i prefer paolo's suggestion; otherwise
eric's solution is better.