According to the comment in qapi/error.h, dereferencing @errp requires
ERRP_GUARD():

* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
* - It must not be dereferenced, because it may be null.
...
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.
*
* Using it when it's not needed is safe, but please avoid cluttering
* the source with useless code.

In nubus_virtio_mmio_realize(), @errp is dereferenced without
ERRP_GUARD().

Although nubus_virtio_mmio_realize() - as a DeviceClass.realize()
method - is never passed a null @errp argument, it should follow the
rules on @errp usage.  Add the ERRP_GUARD() there.

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
v2: Used Markus' words in commit message and added his r/b tag.
---
 hw/nubus/nubus-virtio-mmio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/nubus/nubus-virtio-mmio.c b/hw/nubus/nubus-virtio-mmio.c
index 58a63c84d0be..a5558d3ec28b 100644
--- a/hw/nubus/nubus-virtio-mmio.c
+++ b/hw/nubus/nubus-virtio-mmio.c
@@ -23,6 +23,7 @@ static void nubus_virtio_mmio_set_input_irq(void *opaque, int n, int level)
 
 static void nubus_virtio_mmio_realize(DeviceState *dev, Error **errp)
 {
+    ERRP_GUARD();
     NubusVirtioMMIODeviceClass *nvmdc = NUBUS_VIRTIO_MMIO_GET_CLASS(dev);
     NubusVirtioMMIO *s = NUBUS_VIRTIO_MMIO(dev);
     NubusDevice *nd = NUBUS_DEVICE(dev);
-- 
2.34.1

On 23/7/24 18:18, Zhao Liu wrote:
> According to the comment in qapi/error.h, dereferencing @errp requires
> ERRP_GUARD():
> 
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> * - It must not be dereferenced, because it may be null.
> ...
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> *
> * Using it when it's not needed is safe, but please avoid cluttering
> * the source with useless code.
> 
> In nubus_virtio_mmio_realize(), @errp is dereferenced without
> ERRP_GUARD().
> 
> Although nubus_virtio_mmio_realize() - as a DeviceClass.realize()
> method - is never passed a null @errp argument, it should follow the
> rules on @errp usage.  Add the ERRP_GUARD() there.
> 
> Reviewed-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
> v2: Used Markus' words in commit message and added his r/b tag.
> ---
>   hw/nubus/nubus-virtio-mmio.c | 1 +
>   1 file changed, 1 insertion(+)

Patch queued, thanks!

On 23/7/24 18:10, Philippe Mathieu-Daudé wrote:
> On 23/7/24 18:18, Zhao Liu wrote:
>> According to the comment in qapi/error.h, dereferencing @errp requires
>> ERRP_GUARD():
>>
>> * = Why, when and how to use ERRP_GUARD() =
>> *
>> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
>> * - It must not be dereferenced, because it may be null.
>> ...
>> * ERRP_GUARD() lifts these restrictions.
>> *
>> * To use ERRP_GUARD(), add it right at the beginning of the function.
>> * @errp can then be used without worrying about the argument being
>> * NULL or &error_fatal.
>> *
>> * Using it when it's not needed is safe, but please avoid cluttering
>> * the source with useless code.
>>
>> In nubus_virtio_mmio_realize(), @errp is dereferenced without
>> ERRP_GUARD().
>>
>> Although nubus_virtio_mmio_realize() - as a DeviceClass.realize()
>> method - is never passed a null @errp argument, it should follow the
>> rules on @errp usage.  Add the ERRP_GUARD() there.
>>
>> Reviewed-by: Markus Armbruster <armbru@redhat.com>
>> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
>> ---
>> v2: Used Markus' words in commit message and added his r/b tag.
>> ---
>>   hw/nubus/nubus-virtio-mmio.c | 1 +
>>   1 file changed, 1 insertion(+)
> 
> Patch queued, thanks!

Squashing:

-- >8 --
diff --git a/hw/nubus/nubus-virtio-mmio.c b/hw/nubus/nubus-virtio-mmio.c
index a5558d3ec28..7a98731c451 100644
--- a/hw/nubus/nubus-virtio-mmio.c
+++ b/hw/nubus/nubus-virtio-mmio.c
@@ -7,6 +7,7 @@
   */

  #include "qemu/osdep.h"
+#include "qapi/error.h"
  #include "hw/nubus/nubus-virtio-mmio.h"

---

to avoid:

../hw/nubus/nubus-virtio-mmio.c:26:5: error: call to undeclared function 
'ERRP_GUARD'; ISO C99 and later do not support implicit function 
declarations [-Wimplicit-function-declaration]
     ERRP_GUARD();
     ^
1 error generated.

Better to test your patches ;)

Regards,

Phil.