+Eric
On 5/5/21 11:22 PM, Keith Busch wrote:
> On Wed, May 05, 2021 at 11:10:31PM +0200, Philippe Mathieu-Daudé wrote:
>> The compiler isn't clever enough to figure 'SEG_CHUNK_SIZE' is
>> a constant! Help it by using a definitions instead.
>
> I don't understand.
Neither do I TBH...
> It's labeled 'const', so any reasonable compiler
> will place it in the 'text' segment of the executable rather than on the
> stack. While that's compiler specific, is there really a compiler doing
> something bad with this? If not, I do prefer the 'const' here if only
> because it limits the symbol scope ('static const' is also preferred if
> that helps).
Using: gcc version 10.2.1 20201125 (Red Hat 10.2.1-9) (GCC)
Both static+const / const trigger:
hw/block/nvme.c: In function ‘nvme_map_sgl’:
hw/block/nvme.c:818:5: error: ISO C90 forbids variable length array
‘segment’ [-Werror=vla]
818 | NvmeSglDescriptor segment[SEG_CHUNK_SIZE], *sgld, *last_sgld;
| ^~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
>
>> Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
>> ---
>> hw/block/nvme.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/block/nvme.c b/hw/block/nvme.c
>> index 5fe082ec34c..2f6d4925826 100644
>> --- a/hw/block/nvme.c
>> +++ b/hw/block/nvme.c
>> @@ -812,7 +812,7 @@ static uint16_t nvme_map_sgl(NvmeCtrl *n, NvmeSg *sg,
>> NvmeSglDescriptor sgl,
>> * descriptors and segment chain) than the command transfer size, so it
>> is
>> * not bounded by MDTS.
>> */
>> - const int SEG_CHUNK_SIZE = 256;
>> +#define SEG_CHUNK_SIZE 256
>>
>> NvmeSglDescriptor segment[SEG_CHUNK_SIZE], *sgld, *last_sgld;
>> uint64_t nsgld;
>> --
>> 2.26.3
>>
>
