On 2014/11/13 19:27, Stefan Hajnoczi wrote:
> On Thu, Nov 13, 2014 at 10:39:32AM +0800, [email protected] wrote:
>> From: Gonglei <[email protected]>
>>
>> Signed-off-by: Gonglei <[email protected]>
>> ---
>> hw/virtio/virtio-bus.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
>> index eb77019..dfd2d8c 100644
>> --- a/hw/virtio/virtio-bus.c
>> +++ b/hw/virtio/virtio-bus.c
>> @@ -58,7 +58,7 @@ void virtio_bus_reset(VirtioBusState *bus)
>> {
>> VirtIODevice *vdev = virtio_bus_get_device(bus);
>>
>> - DPRINTF("%s: reset device.\n", qbus->name);
>> + DPRINTF("%s: reset device.\n", BUS(bus)->name);
>
> In general the problem with existing DPRINTF() macros is that they use
> #ifdef. This leads to bitrot, such as this instance.
>
Yes.
> A better approach is:
>
> #define DEBUG_FOO 0
> #define DPRINTF(...) \
> do { \
> if (DEBUG_FOO) { \
> fprintf(stderr, ...); \
> } \
> } while (0)
>
> Now the compiler always checks the DPRINTF() code.
>
> Trace events can be a good solution too. If you like stderr output,
> build QEMU with ./configure --enable-trace-backend=stderr and all
> trace_*() calls are turned into fprintf(stderr).
>
> The cool thing about trace events is that they are available in
> production too.
>
Hum, trace events is great! :)
Best regards,
-Gonglei
