On Fri, Jun 22, 2018 at 04:11:22PM -0400, John Snow wrote:
> If a tree consists exclusively of implicit filter nodes, we might crash
> QEMU. This configuration should not exist in practice, but if it did,
> skipping it would be fine.
>
> For the purposes of debug builds, throw an assert to remind us that
> this configuration is truly unexpected, but if it's compiled out we
> will cope just fine.
>
> Signed-off-by: John Snow <js...@redhat.com>
> ---
> migration/block-dirty-bitmap.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
> index 3bafbbdc4c..02725293dd 100644
> --- a/migration/block-dirty-bitmap.c
> +++ b/migration/block-dirty-bitmap.c
> @@ -287,6 +287,10 @@ static int init_dirty_bitmap_migration(void)
> while (bs && bs->drv && bs->implicit) {
> bs = backing_bs(bs);
> }
> + if (!bs) {
> + g_assert_not_reached();
> + continue;
> + }
If bs can never be NULL, why test that it is non-NULL in the while loop
condition?
Try:
/* Precondition: bs != NULL thanks to the for loop */
while (bs->drv && bs->implicit) {
bs = backing_bs(bs);
}
/* Postcondition: bs != NULL due to implicit node layout assumption */
Does this silence Coverity? ISTR it looks for cues like the bs check in
the while loop condition to decide whether it's likely that a variable
could be NULL.
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