Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/qcow2-snapshot.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index d0e7fa9311..752883e5c3 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -92,11 +92,12 @@ int qcow2_read_snapshots(BlockDriverState *bs)
         }
         offset += extra_data_size;
 
-        if (extra_data_size >= 8) {
+        if (extra_data_size >= endof(QCowSnapshotExtraData,
+                                     vm_state_size_large)) {
             sn->vm_state_size = be64_to_cpu(extra.vm_state_size_large);
         }
 
-        if (extra_data_size >= 16) {
+        if (extra_data_size >= endof(QCowSnapshotExtraData, disk_size)) {
             sn->disk_size = be64_to_cpu(extra.disk_size);
         } else {
             sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
@@ -251,7 +252,7 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
     }
 
     QEMU_BUILD_BUG_ON(offsetof(QCowHeader, snapshots_offset) !=
-        offsetof(QCowHeader, nb_snapshots) + sizeof(header_data.nb_snapshots));
+                      endof(QCowHeader, nb_snapshots));
 
     header_data.nb_snapshots        = cpu_to_be32(s->nb_snapshots);
     header_data.snapshots_offset    = cpu_to_be64(snapshots_offset);
-- 
2.21.0

On 8/19/19 1:55 PM, Max Reitz wrote:
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2-snapshot.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

What, the file got larger in spite of using a helper macro for ease of
readability?  Good thing that 'lines of code' is not the only metric of
goodness ;)

> 
> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> index d0e7fa9311..752883e5c3 100644
> --- a/block/qcow2-snapshot.c
> +++ b/block/qcow2-snapshot.c
> @@ -92,11 +92,12 @@ int qcow2_read_snapshots(BlockDriverState *bs)
>          }
>          offset += extra_data_size;
>  
> -        if (extra_data_size >= 8) {
> +        if (extra_data_size >= endof(QCowSnapshotExtraData,
> +                                     vm_state_size_large)) {
>              sn->vm_state_size = be64_to_cpu(extra.vm_state_size_large);
>          }
>  
> -        if (extra_data_size >= 16) {
> +        if (extra_data_size >= endof(QCowSnapshotExtraData, disk_size)) {

Yes, that is nicer.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org