Re: [Qemu-devel] [RFC PATCH v2 1/3] virtio-bus : Introduce VirtioBus.

["Andreas Färber" <afaerber@suse.de>]

Am 26.11.2012 15:33, schrieb Anthony Liguori:
> fred.konrad@greensocs.com writes:
>> +#define DEBUG_VIRTIO_BUS 1
>> +
>> +#define DPRINTF(fmt, ...) if (DEBUG_VIRTIO_BUS) {                        \
>> +                            printf("virtio_bus: " fmt , ## __VA_ARGS__); \
>> +                          }
> 
> #ifdef DEBUG_VIRTIO_BUS
> #define DPRINTF(fmt, ...) ...
> #else
> #define DPRINTF(fmt, ...) do { } while (0)
> #endif
> 
> You're leaving a dangling if clause which can do very strange things if
> used before an else statement.

If you look at the change history, this was a change in a reaction to me
pointing to a proposal by Samsung. I see your point with the else
statement, that can be circumvented by adding else {}. The reason is to
avoid DPRINTF()s bitrotting because your "do { } while (0)" performs no
compile-tests on "fmt, ..." arguments.

Andreas

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