Using error_is_set(ERRP) to find out whether a function failed is
either wrong, fragile, or unnecessarily opaque. It's wrong when ERRP
may be null, because errors go undetected when it is. It's fragile
when proving ERRP non-null involves a non-local argument. Else, it's
unnecessarily opaque (see commit 84d18f0).
The error_is_set(errp) in internal_snapshot_prepare() is merely
fragile, because the caller never passes a null errp argument.
Make the code more robust and more obviously correct: receive the
error in a local variable, then propagate it through the parameter.
Signed-off-by: Markus Armbruster <arm...@redhat.com>
---
blockdev.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/blockdev.c b/blockdev.c
index 5dd01ea..da358a6 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1116,6 +1116,7 @@ typedef struct InternalSnapshotState {
static void internal_snapshot_prepare(BlkTransactionState *common,
Error **errp)
{
+ Error *local_err = NULL;
const char *device;
const char *name;
BlockDriverState *bs;
@@ -1164,8 +1165,10 @@ static void
internal_snapshot_prepare(BlkTransactionState *common,
}
/* check whether a snapshot with name exist */
- ret = bdrv_snapshot_find_by_id_and_name(bs, NULL, name, &old_sn, errp);
- if (error_is_set(errp)) {
+ ret = bdrv_snapshot_find_by_id_and_name(bs, NULL, name, &old_sn,
+ &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
return;
} else if (ret) {
error_setg(errp,
--
1.8.1.4
