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Date: Mon, 26 Nov 2012 15:45:09 +0100
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Subject: Re: [Qemu-devel] [RFC PATCH v2 1/3] virtio-bus : Introduce
	VirtioBus.
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: peter.maydell@linaro.org, e.voevodin@samsung.com, mark.burton@greensocs.com, qemu-devel@nongnu.org, stefanha@redhat.com, cornelia.huck@de.ibm.com, fred.konrad@greensocs.com

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_=
_); \
>> +                          }
>=20
> #ifdef DEBUG_VIRTIO_BUS
> #define DPRINTF(fmt, ...) ...
> #else
> #define DPRINTF(fmt, ...) do { } while (0)
> #endif
>=20
> 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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