Peng Liang <liangpen...@huawei.com> writes:
> On 6/9/2021 8:15 PM, Daniel P. Berrangé wrote:
>> On Wed, Jun 09, 2021 at 02:09:47PM +0200, Markus Armbruster wrote:
>>> Paolo Bonzini <pbonz...@redhat.com> writes:
>>>
>>>> On 10/06/21 10:47, Zhenzhong Duan wrote:
>>>>> Based on the description of error_setg(), the local variable err in
>>>>> qemu_maybe_daemonize() should be initialized to NULL.
>>>>> Without fix, the uninitialized *errp triggers assert failure which
>>>>> doesn't show much valuable information.
>>>>> Before the fix:
>>>>> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp ==
>>>>> NULL' failed.
>>>>> After fix:
>>>>> qemu-system-x86_64: cannot create PID file: Cannot open pid file:
>>>>> Permission denied
>>>>> Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
>>>>> ---
>>>>> softmmu/vl.c | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>>>>> index 326c1e9080..feb4d201f3 100644
>>>>> --- a/softmmu/vl.c
>>>>> +++ b/softmmu/vl.c
>>>>> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
>>>>> static void qemu_maybe_daemonize(const char *pid_file)
>>>>> {
>>>>> - Error *err;
>>>>> + Error *err = NULL;
>>>
>>> Common mistake, I'm afraid.
>>
>> Initializing isn't likely to be a performance impact, so I'd think
>> we should make 'checkpatch.pl' complain about any 'Error *' variable
>> that is not initialized to NULL, as a safety net, even if not technically
>> required in some cases.
>>
>> Regards,
>> Daniel
>>
>
> Hi,
> Could we add a coccinelle script to check (and fix) these problems? e.g.:
Coccinelle is good for finding and fixing instances of bad patterns that
have crept in. checkpatch is good for keeping them out. Both has its
uses.
> @ r @
> identifier id;
> @@
> Error *id
> + = NULL
> ;
>
> Using this script, I found that local variable err in
> qemu_init_subsystems is not initialized to NULL too.
Crash bug, broken in commit efd7ab22fb "vl: extract
qemu_init_subsystems", v6.0.0. Care to submit a fix?
> The script is not
> prefect though, it will initialize all global/static 'Error *' variables
> and all local 'Error *' variables in util/error.c to NULL, which is
> unnecessary.
Excluding util/error.c is easy once you know how to:
@ depends on !(file in "util/error.c")@
identifier id;
@@
...
Excluding variable definitions with static storage duraction shouldn't
be too hard, either. If Coccinelle is sufficiently clever, adding
keyword auto suffices. Else, try matching keyword static separately,
like so:
(
static Error *id;
|
- Error *id;
+ Error *id = NULL;
)
Completely untested.
