Re: [libvirt] [PATCH] add an assert, to avoid a false-positive NULL-deref warning from clang
According to Jim Meyering on 3/1/2010 10:13 AM:
Here's a case in which using an assertion appears to be the only
way to tell clang that "client" really is non-NULL at that point.
I'm sure clang's analyzers will eventually improve, and hence avoid
this sort of false positive, so have marked this with a FIXME comment,
to help ensure we eventually remove this otherwise unnecessary assertion.
Thanks for the extra context; it makes in-line review a breeze.
@@ -1504,34 +1505,38 @@ static void *qemudWorker(void *data)
virMutexLock(&server->lock);
while (((client = qemudPendingJob(server)) == NULL) &&
!worker->quitRequest) {
if (virCondWait(&server->job, &server->lock) < 0) {
virMutexUnlock(&server->lock);
return NULL;
}
}
Indeed, the only way client can be NULL at this point is if
worker->quitRequest is true...
if (worker->quitRequest) {
if (client)
virMutexUnlock(&client->lock);
virMutexUnlock(&server->lock);
return NULL;
}
But that means we exit here.
worker->processingCall = 1;
virMutexUnlock(&server->lock);
+ /* Tell clang we know what we're doing.
+ FIXME: remove when clang improves. */
+ assert (client);
So this assertion is valid. ACK, if assert() is okay.
On the other hand, perhaps a more invasive rewrite would also work while
also avoiding assert(), by hoisting the worker->quitRequest into the while
loop, something like:
while ((client = qemudPendingJob(server)) == NULL) {
if (worker->quitRequest
|| virCondWait(&server->job, &server->lock) < 0) {
virMutexUnlock(&server->lock);
return NULL;
}
}
if (worker->quitRequest) {
virMutexUnlock(&client->lock);
virMutexUnlock(&server->lock);
return NULL;
}
Should I write that into patch format?
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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