Re: [Qemu-devel] [PATCH] bitops: fix types

[Blue Swirl]

On Sun, Jul 8, 2012 at 6:54 PM, Peter Maydell <address@hidden> wrote:
> On 8 July 2012 19:32, Blue Swirl <address@hidden> wrote:
>> On Sun, Jul 8, 2012 at 2:04 PM, Peter Maydell <address@hidden> wrote:
>>> On 8 July 2012 13:12,  <address@hidden> wrote:
>>>> -static inline uint64_t deposit64(uint64_t value, int start, int length,
>>>> -                                 uint64_t fieldval)
>>>> +static inline uint64_t deposit64(uint64_t value, unsigned int start,
>>>> +                                 unsigned int length, uint64_t fieldval)
>>>>  {
>>>>      uint64_t mask;
>>>> -    assert(start >= 0 && length > 0 && length <= 64 - start);
>>>> +    assert(length > 0 && length <= 64 - start);
>>>
>>> This breaks the assertion (consider the case of start == UINT_MAX
>>> and length == 64).
>>
>> The original is equally buggy in other cases since there is no bound
>> check for the upper limit.
>
> For what upper limit? Overlong length or start should both be caught
> by the third condition in the signed case.

Nice. Why is it written like that, I'd use
start + length <= 64?

>
>
> -- PMM