Re: [Qemu-devel] [PATCH] hw/ide/ahci.c: Fix shift left into sign bit

[Peter Maydell]

On 16 October 2015 at 21:43, John Snow <address@hidden> wrote:
>
>
> On 10/16/2015 01:48 PM, Peter Maydell wrote:
>> Avoid undefined behaviour from shifting left into the sign bit:
>>
>> hw/ide/ahci.c:551:36: runtime error: left shift of 255 by 24 places cannot 
>> be represented in type 'int'
>>
>> (Unfortunately C's promotion rules mean that in the expression
>> "some_uint8_t_variable << 24" the LHS gets promoted to signed
>> int before shifting.)
>>
>> Signed-off-by: Peter Maydell <address@hidden>
>> ---
>> clang's undefined sanitizer produces a lot of copies of this warning during
>> 'make check'...
>>
>>  hw/ide/ahci.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
>> index 796be15..21f76ed 100644
>> --- a/hw/ide/ahci.c
>> +++ b/hw/ide/ahci.c
>> @@ -548,7 +548,7 @@ static void ahci_init_d2h(AHCIDevice *ad)
>>          ad->init_d2h_sent = true;
>>          /* We're emulating receiving the first Reg H2D Fis from the device;
>>           * Update the SIG register, but otherwise proceed as normal. */
>> -        pr->sig = (ide_state->hcyl << 24) |
>> +        pr->sig = ((uint32_t)ide_state->hcyl << 24) |
>>              (ide_state->lcyl << 16) |
>>              (ide_state->sector << 8) |
>>              (ide_state->nsector & 0xFF);
>>
>
> Reviewed-by: John Snow <address@hidden>
>
> Since the "patches" tool seems to still be hiccuping, do you want to
> just apply this directly?

OK, applied to master.

thanks
-- PMM