Leonid Bloch <[email protected]> writes:
> Hi,
>
> On 1/8/19 2:20 PM, Kevin Wolf wrote:
>> Am 03.01.2019 um 22:33 hat Leonid Bloch geschrieben:
>>> The lookup table for power-of-two sizes is now auto-generated during the
>>> build, and not hard-coded into the units.h file.
>>>
>>> This partially reverts commit 540b8492618eb.
>>>
>>> Signed-off-by: Leonid Bloch <[email protected]>
>>
>> During a downstream review, Max found a problem with the table that we
>> could fix while we're touching it:
>>
>> Upstream: All >= S_2GiB are not valid ints. (qemu assumes that
>> sizeof(int) == 4, right?) So S_2GiB should be 2147483648u and all
>> above should be ...ull or better UINT64_C().
So their (integer) type can vary. Whether that's a problem depends on
how the macros are used.
> But the initial reasoning for this table was to have a pure number
> there. If there will be strings like "2147483648u/ull" or
> "UINT64_C(...)" there, they will be stringified, literally, and will
> appear as such inside the binary.
"Macro that expands to an integer constant that stringify() turns into a
decimal number" is a rather peculiar contract.
> If specifying the unit64 type is
> really needed, one can always use, e.g., 2 * GiB, from units.h.
Right now I suspect these S_ macros should generally be avoided.
We have 54 of them. I count six uses:
block/qcow2.h:#define QCOW_MAX_REFTABLE_SIZE S_8MiB
block/qcow2.h:#define QCOW_MAX_L1_SIZE S_32MiB
block/qcow2.h:#define DEFAULT_L2_CACHE_MAX_SIZE S_32MiB
block/qcow2.h:#define DEFAULT_L2_CACHE_MAX_SIZE S_8MiB
block/qcow2.h:#define DEFAULT_CLUSTER_SIZE S_64KiB
block/vdi.c:#define DEFAULT_CLUSTER_SIZE S_1MiB
Which if them truly need stringify-able integers?
