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qemu: snapshot: Restructure control flow to detect errors sooner and work around compiler

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Some compilers aren't happy when an automatically freed variable is used
just to free something (thus it's only assigned in the code):

When compiling qemuSnapshotDelete after recent commits they complain:

../src/qemu/qemu_snapshot.c:3153:61: error: variable 'delData' set but not used [-Werror,-Wunused-but-set-variable]
                g_autoslist(qemuSnapshotDeleteExternalData) delData = NULL;
                                                            ^

To work around the issue we can restructure the code which also has the
following semantic implications:
 - since qemuSnapshotDeleteExternalPrepare does validation we error out
   sooner than attempting to start the VM

 - we read the temporary variable at least in one code path

Fixes: 4a4d89a925
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
This commit is contained in:
Peter Krempa 2023-01-09 14:01:59 +01:00
parent bb80344fd0
commit 64366c0056
1 changed files with 8 additions and 8 deletions
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16
src/qemu/qemu_snapshot.c
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@ -3146,12 +3146,13 @@ qemuSnapshotDelete(virDomainObj *vm,
if (virDomainSnapshotIsExternal(snap) && if (virDomainSnapshotIsExternal(snap) &&
!(flags & (VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN | !(flags & (VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN |
VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY))) { VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY))) {
g_autoslist(qemuSnapshotDeleteExternalData) tmpData = NULL;
externalData = qemuSnapshotDeleteExternalPrepare(vm, snap); /* this also serves as validation whether the snapshot can be deleted */
if (!(tmpData = qemuSnapshotDeleteExternalPrepare(vm, snap)))
goto endjob;
if (!virDomainObjIsActive(vm)) { if (!virDomainObjIsActive(vm)) {
g_autoslist(qemuSnapshotDeleteExternalData) delData = NULL;
if (qemuProcessStart(NULL, driver, vm, NULL, VIR_ASYNC_JOB_SNAPSHOT, if (qemuProcessStart(NULL, driver, vm, NULL, VIR_ASYNC_JOB_SNAPSHOT,
NULL, -1, NULL, NULL, NULL, -1, NULL, NULL,
VIR_NETDEV_VPORT_PROFILE_OP_CREATE, VIR_NETDEV_VPORT_PROFILE_OP_CREATE,
@ -3163,20 +3164,19 @@ qemuSnapshotDelete(virDomainObj *vm,
/* Call the prepare again as some data require that the VM is /* Call the prepare again as some data require that the VM is
* running to get everything we need. */ * running to get everything we need. */
delData = g_steal_pointer(&externalData); if (!(externalData = qemuSnapshotDeleteExternalPrepare(vm, snap)))
externalData = qemuSnapshotDeleteExternalPrepare(vm, snap); goto endjob;
} else { } else {
qemuDomainJobPrivate *jobPriv = vm->job->privateData; qemuDomainJobPrivate *jobPriv = vm->job->privateData;
externalData = g_steal_pointer(&tmpData);
/* If the VM is running we need to indicate that the async snapshot /* If the VM is running we need to indicate that the async snapshot
* job is snapshot delete job. */ * job is snapshot delete job. */
jobPriv->snapshotDelete = true; jobPriv->snapshotDelete = true;
qemuDomainSaveStatus(vm); qemuDomainSaveStatus(vm);
} }
if (!externalData)
goto endjob;
} }
} }