Leonid Bloch <lbl...@janustech.com> writes:
> On 1/10/19 2:51 PM, wrote:
>> Leonid Bloch <lbl...@janustech.com> 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 <lbl...@janustech.com>
>>>>
>>>> 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?
>>
>
> These two:
>
> block/qcow2.h:#define DEFAULT_CLUSTER_SIZE
> block/vdi.c:#define DEFAULT_CLUSTER_SIZE.
Compared to the complexity visible in this thread,
.def_value_str = "65536", /* must match DEFAULT_CLUSTER_SIZE */
looks attractively stupid to me then.
